Actuator with brushless permanent-magnet motor

Abstract

Disclosed is an actuator (1) for moving a load in an HVAC system. The actuator (1) includes a motor (15), the motor being a brushless permanent-magnet motor. The actuator includes a gear unit (16), wherein an input side of the gear unit (16) is coupled to the rotor and an output member (12) of the gear unit (16) is configured for coupling to the load. The actuator further includes a control unit (13). The control unit (13) is configured for repeatedly determining in a rotor position determination routine an electrical rotor position at any rotational speed including standstill exclusively by way of measuring and computationally processing electrical variables. The control unit is further configured for controlling the motor (15) in dependence of the electric rotor position. The control unit is further configured for updating, based on the electrical rotor position, an output member position variable, the output member position variable representing a computed output member position. The control unit is further configured to control execution of a synchronization routine, the synchronization routine including setting the output member position variable to a reference value.

Description

[0001] ACTUATOR WITH BRUSHLESS PERMANENT-MAGNET MOTOR

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to an actuator with a brushless permanent-magnet motor for moving a load, in particular a valve member of a valve, or a damper blade of a damper.

[0004] BACKGROUND OF THE INVENTION

[0005] Actuators with a control unit, a reduction gear and a motor are generally known in the art and used for actuating a large variety of loads in numerous applications, such as for controlling dampers or valves of HVAC (Heating, ventilation, and air conditioning) sys- terns. In a typical HVAC system, a number of actuators is typically present and require different operation parameters regarding, e.g. moving ranges, torque, speed, and control mode. In particular, e.g., operation in position control, speed control or torque control mode may be required. In the interest of cost efficiency for installation as well as maintenance, the use of standardized drives respectively multi-purpose drives that can be used in a plurality of applications is desirable.

[0006] Further, it is desirable to rely on sensor feedback as little as possible and ideally completely avoid the need for sensors in control and supervision of the actuators, since typically applied sensors are comparatively costly and often have a limited lifetime. Sensors therefore require particular care in maintenance and are generally fault susceptible. SUMMARY OF THE INVENTION

[0007] It is the overall objective of the present disclosure to improve the state of the art regarding actuators in particular for use in HVAC systems. Favorably, one or more drawbacks of known actuators are reduced or fully eliminated. Particular favorable properties and advantages of various types and embodiments of actuators as disclosed in the following are discussed in their respective specific context. In an aspect, the present disclosure concerns an actuator for moving a load in an HVAC system. The load may in particular be a fluid flow regulating member, in particular a valve member of a valve or a damper blade of a damper. It is to be understood, however, that the actuator may generally be used for other types of loads. The fluid may in principle be any fluid, being it liquid, gaseous, or mixture of both. In the context of an HVAC system, the fluid may in particular be or include water, air, an internal auxiliary fluid of the HVAC system, such as Glycol, or any mixture thereof. Further in an HVAC context, the fluid is generally a heat transport fluid. A valve or damper is also referred to as fluid flow control device.

[0008] The actuator includes a motor. The motor is a brushless permanent-magnet (PM) motor having a permanent-magnet rotor and a stator with a at least two phases. The permanent magnet rotor causes a measurable inductance variation in the stator windings that is periodical with the electrical rotor position. The inductance variation is due to saturation effects caused by the magnetic field of the permanent magnets. In a typical design that is generally assumed in the following, the motor has three phases. The motor may be a synchronous motor, preferably generating a sinusoidal or approximately sinusoidal back- EMF in operation. The poles may be salient poles with buried or surface-mounted permanent magnets which may be optionally potted. In another design, the motor may be a synchronous reluctance motor (RM). The circuitry that is required for the commutation and energizing the phases is not considered as part of the motor but as part of a control unit as discussed further below. In a further embodiment the motor may be a brushless permanent magnet motor according to WO2011 / 047488A1 , the motor having a detent torque plate for generating a torque to bring the motor into latching position when being inoperative or not powered.

[0009] The actuator further includes a gear unit. An input side of the gear unit is coupled to the rotor and an output member of the gear unit is configured for coupling to the load. A relation between the movement of the input side and the output member is referred to as transmission rate. In an embodiment, the gear unit is or includes a reduction gear. In embodiments where the actuator is a rotatory actuator, the gear unit may be a reduction gear and the transmission ratio may be the gear ratio of the reduction gear. Such type of embodiment is generally assumed in the following. In other embodiments, however, the gear unit may be designed differently and may, in addition or alternatively to a reduction gear, include further transmission mechanics, for example a rotational-to-translational conversion mechanism which may, e.g. be realized as a linear stage with a spindle gear. In an embodiment where the output member is designed for a linear movement as it is the case, e.g., for a linear stage, the transmission ratio reflects the relation between the rotational movement of the input side and the translational movement of the output member, and may have a unit of displacement per angle, for example mm per degree (°) or mm per revolution. Also for embodiments where the actuator is as such a rotatory actuator and the output member accordingly makes a rotational movement, the load may include a rotational-to-transitional conversion mechanism or may be coupled with the output member via such a conversion mechanism.

[0010] In typical embodiments, the actuator is a rotatory actuator and is designed to provide a torque at the output member in a range of 1 Nm to 250Nm. In an embodiment, the output member may rotate continuously in the same direction without mechanical stops in an endless manner, respectively over any desired number of revolutions. In other embodiments, however, the rotational angle of the output member, respectively the output mem- ber position, is limited due to the design of the actuator to less than a full rotation respectively 360°, for example 90°. Elements that mechanically limit the movement range are referred to as end position stops. In an embodiment, at least one end stop of an actuator housing limits the rotational freedom of the output member or an end wheel of the gear unit, as disclosed, e.g. in W02007 / 051332A1. In an embodiment, two opposed end position stops may be foreseen at the opposed ends of the movement range.

[0011] The actuator further includes a control unit. The control unit includes a power circuit for energizing the phases of the motor. The control unit is configured for repeatedly executing the steps of:

[0012] - determining, in a rotor position determination routine, an electrical rotor position at any rotational speed including standstill exclusively by way of measuring and computationally processing electrical variables of the power circuit and / or the motor,

[0013] - controlling the motor, in particular controlling energization of the phases, in dependence of the electric rotor position, thereby generating a stator field,

[0014] - updating, based on the electrical rotor position, an output member position variable, the output member position variable representing a computed output member position.

[0015] In an embodiment, the control unit is configured to control energization of the phases by way of pulse width modulation (PWM) as generally known in the art.

[0016] In the here-discussed design, the control unit is further configured to control execution of a synchronization routine. The synchronization routine includes setting the output member position variable to a reference value.

[0017] For the here-described actuator, control of the motor, especially energizing of the phases, relies only on electrical measurements at the motor respectively in the control unit, but does not rely on feedback signals generated by sensors that directly detect or measure a mechanical movement. Energization of the phases does in particular not rely on a position sensor. This holds true under all operational conditions including stillstand. Particular approaches and methods that may be employed in this context are discussed further below.

[0018] Also, the output member position is generally determined from the electrical rotor position that is, in turn, determined by way of electrical measurements. The output member position variable uniquely reflects an output member position, e.g. in form of a rotational angle or a linear position respectively displacement. It is further assumed that in an operational configuration the load is coupled to the output member such that the output member position also uniquely respectively unambiguously reflects the load position. For a rotatory actuator, the load may be directly coupled, in particular rotationally coupled, with the output member, e.g. via a shaft. The movement of the load, however, may also be different from rotatory, for example linear in case of the load being the valve member of a globe valve as mentioned above. In this case, a corresponding rotational-to-transla- tional conversion mechanism may be foreseen in the power flow between the output member and the load.

[0019] It is noted that in some embodiments of a rotatory actuator respectively an actuator with a rotatory output member, output member positions of more than 360° respectively one full revolution of the output member may be required, e.g. for a globe valve that is coupled to the output member via a rotational-to-translational conversion mechanism to achieve a full stroke. For such applications, the actuator may be a rotatory actuator where the output member is continuously rotatable over more than a full rotation, e.g. in an endless manner as discussed above. Here, the output member position variable may reflect a linear position of the load corresponding to rotational angle of in a range of 0° to 3600° or ten revolutions, respectively, Once the output member position variable is correctly set respectively initialized, it can be continuously updated by increasing respectively decreasing in accordance with the electrical rotor position changing. The initialization is achieved by executing the synchronization routine, in particular when powering up the actuator or as desired or required during operation as discussed further below.

[0020] For the here-described actuator, no sensors need accordingly to be relied on for determining the output member position and accordingly the load position in regular operation.

[0021] The output member position is linked to the mechanical rotor position via the transmission ratio. The mechanical rotor position is to be understood as actual and measurable rotatory position and is cyclic in accordance with the rotor revolutions.

[0022] The relation between the electrical rotor position and the mechanical rotor position depends on the design of the motor. A brushless permanent-magnet motor as mentioned before is generally known in the art and comprises a stator with a number of circumferentially distributed teeth. A typical example is a design with 3 phases and 3 teeth per phase, i.e. 9 teeth in total.

[0023] The mechanical rotor angle and the electrical rotor angle are linked by the number of pairs of poles as proportionality factor. For an exemplary design with three pole pairs, a change in the electrical rotor position by 360 degrees corresponds to a change of the mechanical rotor position by only 120 degrees, i.e., one third of a revolution. A full 360° cycle of the electrical rotor position is referred to as electrical period.

[0024] It follows that from a change of the electrical rotor angle, the corresponding change of the output member position can be computed in a straight-forward way based on the given motor design, specifically the number of pairs of poles, and the transmission ratio. The expression "computed output member position" reflects the fact that the output member position variable as determined based on the electrical rotor position is a computed value that generally corresponds to the actual mechanical output member position.

[0025] Methods and procedures for determining the electrical rotor position byway of measuring and computationally processing electrical variables, i.e., without relying on physical sensors, are known in the art. An overview of various methods that may be used for an actuator in accordance with the present disclosure is given in the following work: SZALAI, Thomas, 2015. Sensorlose Regelung gesattigter Synchronmaschinen bis zum Stillstand unter Last [online]. Available under https: / / www.db-thueringen.de / re- ceive / dbt_mods_00025982. An exemplary specific method that may, e.g., be used is the so-called "INFORM" method (INFORM: ”l Ndirect Flux detection by On-line Reactance Measurement") as described in Manfred Schroedl, "Sensorless Control of AC Machines at Low Speed and Standstill Based on the "INFORM" Method", Conference Record of the 1996 IEEE Industrial Applications Society, page 270-277, as well as AT406722B.

[0026] Under certain conditions that may occasionally occur in use, however, the output member position variable and accordingly the computed output member position may not correspond to the actual mechanical output member position.

[0027] The actuator may in some embodiments as discussed further below allow a decoupling of the load from the motor and a movement of the load, e.g. a damper blade, by way of external forces, for example by hand and without the rotor moving. In this case, the correct correspondence between the computed output member position as reflected by the output member position variable on the one side, and the actual mechanical output member position and the load on the other side, is lost. Further, the output member position variable may become void due to a loss in the power supply, or under general error conditions.

[0028] Further, the correspondence between the output member position variable respectively computed output member position and the actual mechanical output member position is generally unknown at the time of powering up. It therefore needs to be correctly set, e.g., during commissioning and after maintenance.

[0029] To deal with any of such situations, the control unit is configured to execute respectively control execution of a synchronization routine. The synchronization routine serves the purpose of unambiguously linking the output member position variable and accordingly the computed output member position to an actual mechanical output member position and the load. It is noted that by executing the synchronization routine an initialization of the output member position variable respectively a calibration is achieved. Therefore, the synchronization routine may equivalently be an initialization routine or calibration routine.

[0030] In an embodiment, the reference value to which the output member position variable is set in the synchronization routine is a pre-defined value, for example zero. Alternatively or additionally, the reference value may be received by the control unit via a wired or wireless communication interface, respectively may be configurable.

[0031] Generally, values and parameters, such as configurable respectively user-settable values as discussed in the present documents may be received by the actuator by way of a wired and / or wireless communication interfaces. For wired as well as wireless communication, generally all types of standards and technologies as known in the art may be used. Field bus systems are known in the art. For wireless communication, the actuator respectively its control unit may include one or more wireless communication interface, such as a Bluetooth interface and / or a NFC (Near Field Communication) interface of establishing communication with an external device via an NFC link. In a particular embodiment with NFC interface, the control unit is configured for data transmission without relying on a power supply of the actuator respectively in a state where the actuator is not connected to a power supply, or such power supply is interrupted or switched off. In such a design, the NFC interface and optionally further circuity may be designed for wireless power supply via the NFC link.

[0032] In further embodiments, the synchronization routine may include determining an actual mechanical output member position by way of a quantitative output member position sensor, and / or may include detecting if the output member assumes a mechanically predetermined reference output member position as discussed further below. In an embodiment, the synchronization routine may include controlling the motor to move the output member to assume or pass through the reference output member position.

[0033] The output member assuming a specific position, such as a reference output member position, includes the case of the output member moving into the position as end position, as well as the case of the output member passing through the respective position.

[0034] The circuitry of the actuator, in particular the control unit, may generally be semiconductor-based and include passive as well as active components as known in the art. While other designs are possible as well, the control unit may include one or more microcomputers and / or microcontrollers with corresponding software respectively firmware for controlling operation of the actuator, including execution of the various routines in accordance with the present disclosure, in particular the synchronization routine. In a further favorable design, the control unit includes one or more ASICs. In an embodiment, the control unit is configured to control, based on the electrical angle, an output member position and / or a torque applied by the actuator at stillstand. Control of the output member position at stillstand is particularly useful in applications where a load, e.g. the valve member of a valve or a damper blade of a damper, shall be controlled to maintain a particular target position in the presence of external forces and / or torques acting thereon. Torque control at stillstand is particularly useful for maintaining the load, in particular a damper blade, in a desired position, in particular a fully open or fully closed position, in a well-defined manner. Torque control may generally refer to the torque exerted by the motor or the torque at the output member. For controlling the actuator to maintain a particular target position, one or more particular position maintaining modes may be foreseen as discussed further below.

[0035] In an embodiment, the control unit is configured to monitor, in particular continuously monitor, the output member position and / or speed under torque control in particular at stillstand. The actuator, specifically the control unit, may further be configured to detect, based on the computed output member position respectively the output member position variable and / or speed, the occurrence of a fault or hazardous condition and to modify the control of the motor in dependence of the output member position and / or speed in this case. Such fault or hazardous may in particular be a mechanical defect at the side of the load, for example a damper. At stillstand, the output member position can be expected to be constant and the speed can be expected to be zero. A significant change in the output member position and / or a non-zero output member speed may indicate a mechanical defect of the damper, for example a breakage. Without safety measures, torque control would in this situation result in an uncontrolled acceleration, resulting in an ultimate damage of the actuator and / or further elements as well as in safety risks. Therefore, the control unit may be configured in such situation to de-energize the motor, to limit the motor speed, to switch to speed or position control or to move the output member, e.g. in a particular fault control mode, into a safety position which is subsequently maintained.

[0036] In an embodiment, the control unit may be configured to control the torque applied by the motor or the output member while at the same time limiting the rotational speed of the output member and / or the rotor. Such control is particularly useful for approaching a mechanical stop, for example an end position of a damper, under torque control.

[0037] The control unit may be configured for determining the torque exerted by the motor and / or the output member, as well as a rotational speed of the rotor and / or of the output member as computed motor torque, computed output member torque, computed rotor speed and / or computed output member speed based on the electrical rotor position and / or the computed output member position as stored by the output member position variable, and / or generally by way of measuring and computationally processing electrical variables of the power circuit and / or the motor, i.e. in a sensorless manner. In an embodiment, the control unit may, e.g., be configured to compute the computed motor torque from the drawn current as known in the art and to compute the computed output member torque from the computed motor torque and the gear ratio. Similarly, the computed rotor speed may be computed from the change of the electrical rotor position in time respectively the time derivative of the electrical rotor position. The computed output member speed may be computed from the computed rotor speed and the gear ratio or as time derivate of the computed output member position. In another embodiment, the control unit includes, additionally or alternatively, a mathematical motor model and / or actuator model, for example an observer-based motor model and / or actuator model. The control unit may be configured to determine the computed output member position and / or one or more of the other before-discussed computed variables by evaluating the mathematical motor model and / or actuator model. In an embodiment, the mathematical model may include temperature information of the motor and / or the control circuit and / or the actuator and / or an ambient temperature.

[0038] In an embodiment, the control unit is configured to control the actuator in a number of alternative control modes. The control modes may in particular include one or more of a position control mode, torque control mode and a speed control mode. The control unit may be configured for switching between control modes in operation, in particular during movement. Providing alternative control modes and allowing a switching between control modes during movement allows a flexible operation and is favorable in various situations. For example, when moving a damper blade into a pre-defined damper blade position, for example a fully closed position, it can be favorable to do most of the movement under position control but to finally move the damper blade into the closed position with speed control or torque control in order to ensure tight closing. In an embodiment, the actuator is configured to operate in a gum sealing mode in which the load, in particular a damper blade, is continuously pushed into a rubber respectively gum seal via the actuator. A positional range for the gum sealing mode may be set by way of parametrization.

[0039] In an embodiment, the actuator is configured for switching between alternative control modes autonomously in dependence of operational conditions. Typical operational conditions that may trigger a switching between alternative control modes may be, for example, one or more of: the output member assuming or approaching a generally predetermined target position; the rotational speed of the output member and / or the rotor falling below or rising above a threshold speed; the torque exerted by the motor or the output member exerting a pre-determined threshold torque; a temperature of the motor as measured by a temperature sensor of the actuator exceeding a threshold motor temperature; a current drawn by the actuator or the motor raising above or falling below a threshold current. Further in an embodiment, the actuator is configured for selecting a control mode from a number of alternative control modes via an integrated or external user interface. Further, the actuator and in particular the control unit may be configured for receiving a control mode command via wired or wireless communication interface and to select the control mode in accordance with the control mode command.

[0040] An external user interface may, for example, be realized by a dedicated programming device, configuration device and / or diagnostic device, or by a general-purpose device, such as a smartphone or tablet computer with a corresponding software application.

[0041] In an embodiment, the actuator is configured to operate in a client mode and an alternative server mode. In the client mode, the actuator may in particular be configured to operate in a position control mode or a speed control mode. In the server mode, the actuator may in particular be configured to operate in a torque control mode. An operator operating in the client mode is referred to as client actuator and an actuator operating in the server mode is referred to as server actuator. The actuator may be configured for coupling with at least one further actuator via a communication link, respectively via wired or wireless communication interfaces of each of the actuators. Thereby, a client-server actuator arrangement with at least two actuators may be formed. The client actuator operates generally under position or speed control and provides, via the communication link, required support torque values to one or more server actuators operating in each case in a torque control mode. The output members of all actuators may be mechanically coupled and act on a common load. In this, way, movement of the load may be position controlled or force respectively torque controlled, with the required torque being distributed among the client actuator and the one or more server actuators. In a variant, an actuator is configured to operate as client actuator respectively in the client mode only or may be configured to operate as server actuator or in the server mode only. While the combination of more than one actuator in a client-server actuator arrangement are generally known, e.g., from EP2681634B1 which particularly concern an automatic mode selection for the actuators, the here-described solution is particularly simple and favorable in application. Such arrangement with a client actuator and one or more server actuators which may, e.g. be arranged in a piggyback arrangement, may be used for load sharing and may include actuators of different size respective dimensioning. Further, in case of the client actuator failing, a server actuator may automatically switch from the server mode into the client mode.

[0042] In an embodiment, the control unit is configured for controlling the motor, in particular energization of the phases, by way of closed loop control, wherein feedback signals are generated by way of measuring and computationally processing electrical variables of the power circuit and / or the motor. In a particular design, feedback signals are exclusively generated by way of measuring and computationally processing electrical variables of the power circuit and / or the motor. In an embodiment, the control unit includes an observer, such as a Luenberger observer, of the motor or and / or the actuator.

[0043] In an embodiment, the control unit is configured for controlling the motor, in particular energization of the phases, in a primary control mode and simultaneously one or more superimposed safety limit control modes. For the primary control mode, a constant or time-variable target value may be provided as input variable. General references to a control mode through this document refer to a primary control mode. Superimposed safety limit control modes may be used for monitoring one or more variables and ensure that respective threshold values are not exceeded or fallen below, respectively. For example for torque control with additional monitoring and supervision of the speed as discussed above, the primary control mode is a torque control mode and the speed may be monitored via a superimposed speed safety limit control mode. A safety limit control mode may generally overrule the primary control mode. In a particular embodiment with alternative control modes, the control unit is configured to control the motor to move the output member into a mode switching position in position control mode and to switch, upon the computed output member corresponding to the mode switching position, into speed control mode. A mode switching position value which represents the mode switching position may be stored in the control unit. The output member position variable may be continuously checked against the mode switching position value. Alternatively or additionally, a mode switching position may be stored as a time that is needed for output member to reach the mode switching position at a given speed. In a particular embodiment, the actuator may further be configured to switch from the speed control mode back into position control mode and / or force control respectively torque control mode. In particular, a constant target position or target torque may be maintained after switching back from the speed control mode back to position control or torque control. This may in particular be used to maintain a target position or target torque after moving to the target position under speed control.

[0044] In an embodiment, the control unit is configured to select control modes and / or control parameters according to the motor type. The control unit may accordingly a number of at least two alternative control modes for different motor types. Motor-dependent control mode and / or control parameter selection may be done hardware-wise, e.g. by way of jumpers or switches, and / or software wise and may be stored in one or more corresponding registers of the control unit when parameterizing the actuator during manufacture. In a further variant, the control unit is configured to autonomously determine the motor type by way of electrical measurements during operation and select control modes and / or control parameters accordingly. In particular a position maintaining mode as mentioned before may be selected in dependence of the motor type. In a position maintaining mode, the control unit is configured to maintain the output member in a target position or a target range around a target position with low and favourable minimal power consumption. A motor as used in the present context may in particular be a cogging torque motor or a non-cogging torque motor. A cogging torque motor has dedicated stable rotor positions that are maintained without the motor phases being energized, up to a certain threshold torque (generally referred to as cogging torque, detent torque or no-current torque) acting on the rotor. A cogging torque motor is to be understood as a motor that designed such that it has a high cogging torque, in particular a cocking torque of at least 10%, 50%, 80% or 100% if its nominal torque. Up to the design-given cogging torque, it can hold the rotor position and accordingly the position of the output member and the thereto coupled load without being energized. The stable rotor positions are periodic per rotor revolution. Around each stable rotor position, a stability range exists from where the rotor, after being deflected, returns to the stable rotor position. In a non-energized state, the rotor of a cogging torque motor generally stops in a stable rotor position. Cogging torque motors are generally suited, e.g., for actuating, e.g. valves and dampers in many HVAC applications. In a particular embodiment, the motor is a cogging torque motor with 6 poles or 12 poles and, e.g., square respectively rectangular magnetization.

[0045] A non-cogging torque motor, in contrast, is a motor of low or even negligible threshold torque. Some degree of periodic torque variation and accordingly residual cogging is generally present nevertheless. A non-cogging torque motor may be a motor with a residual cogging torque of less or no more than 10%, preferably less or no more than 5% of its nominal torque. A non-cogging torque motor has accordingly no stable rotor positions or has stable rotor positions which, however, are not pronounced. The residual cogging torque of a non-cogging torque motor is generally not sufficient to maintain a load in a stable position without the motor being energized. A non-cogging torque motor may for example be used in spring return actuators respectively fail-safe actuators as used in fire and / or smoke protection systems. As generally known in the art, a damper blade is generally maintained in a regular operational position by the motor against the torque exerted by a return spring. If the motor is de-energized in an emergency, such as a fire and / or smoke situation, the return spring moves the damper blade in a typically fully open of fully closed emergency position. Here, a non-cogging torque motor is favourable since the need for overcoming a cogging force in case of an emergency is undesirably. While a low energy consumption of the actuator for maintaining a target position is generally desirable, it is particular relevant for spring return actuators. In a particular embodiment, the motor is a non-cogging torque motor with 8 poles and sine magnetization.

[0046] In an embodiment, the control unit is configured to control the actuator to operate in a holding torque mode as position maintaining mode. A holding torque mode as described in the following is particularly suited in the context of non-cogging torque motors and / or spring-return actuators. In the holding torque mode, a combination of torque resulting from energizing the motor respectively its phases, residual cogging and internal friction of the actuator, in particular the gear unit, is used for maintaining the output member (and accordingly a thereto coupled load) in a position tolerance range. The holding torque mode may include automatically determining a minimum holding torque limit that is required to maintain the output member in a stable manner and within the position tolerance range. Determining the minimum holding torque limit may include stepwise respectively successively reducing a maximum holding torque and therewith the holding torque that is exerted by the motor. The maximum holding torque is an adjustable respectively settable maximum limit for the torque that may be provided by the motor. The step width, i.e. the amount by which the maximum holding torque is reduced, may be constant in each step. In a particularly favourable design, however, the step width is not constant but successively reduced. That is, the reduction starts with a maximum step width and is subsequently reduced from step to step. The reduction may, e.g. be exponential and follow a decreasing exponential function or an approximation thereof. In this way, the reduction can be done with a small number of iterations respectively in a short time. As initial value for the minimum holding torque limit, a value of zero may be used. As initial value for the maximum holding torque, a comparatively high value may be set as maximum holding torque limit. The maximum holding torque limit may in particular be higher than a value that is actually required for position maintaining. For example, the maximum holding torque limit may be set to the nominal torque of the motor as initial value.

[0047] Operating in the holding torque mode may in particular be executed under position control with superimposed torque limit control. Via the torque limit control, the actuator is controlled not to exceed a torque beyond the maximum holding torque. The maximum holding torque is controlled in the holding torque mode not to fall below the minimum holding torque limit as mentioned.

[0048] In an embodiment, the holding torque mode includes determining if the computed output member position respectively the output member position variable is within a position tolerance range around the target position. Favorably, the position tolerance range is centered with respect to the target position. The width of the position tolerance range is generally pre-determined and may optionally be a settable parameter.

[0049] Determining whether the computed output member position is stable may be carried out in various ways, for example via the motor speed. In a particular embodiment, however, determining whether the output member position variable is stable is determined by determining whether the output member position variable is within a stability range. The output member position variable is assumed to be stable if it is within the stability range, in particular for a pre-determined time span. For this purpose, a timer, in particular a countdown timer, may be foreseen. An appropriate time span is generally determined by an overall time constant of the actuator respectively the time that is required for building- up respectively stabilizing the torque. The time span, may, for example be in a range of 300ms to 700ms, preferably 400 to 600ms in a typical design. A width of the stability range, i.e. the angular difference between the limits of the stability range, is generally smaller than the width of the position tolerance range and may, e.g., be approximately half of the width of the position tolerance range. If the width of the position tolerance range is between 100 degrees and 150 degrees, for example 110 degrees or 130 degrees, the width of the stability range may typically be between 40 degrees and 70 degrees, for example 50 degrees or 65 degrees, when referring to the movement of the rotor. While in the above mentioned cases the position tolerance range and of the stability range a fraction of a rotor revolution, the ranges can also include one or more rotor revolutions. Like the position tolerance range, the width of the stability range may be predetermined and may optionally be a settable parameter. The stability range may move together with the rotor. In an embodiment, the holding torque mode may include repeatedly updating the stability range. Specifically, the stability range may be repeatedly updated or set such that that the center of the stability range corresponds to the computed output member position. Along with setting the stability range, the computed output member position as center of the stability range may be saved as saved position.

[0050] In a particular embodiment, the holding torque mode includes executing the following steps: a) set the maximum holding torque to the maximum holding torque limit such that the output member position variable moves into the position tolerance range; optionally verify that the output member position variable is stable, store the output member position variable as saved position and set the stability range; b) reduce the maximum holding torque, but in any case not below the minimum holding torque limit; c) start the countdown timer for measuring the pre-determined time span, store the output member position variable as saved position and set the stability range; d) while the countdown timer is running d1) if the output member position variable leaves the position tolerance range: increase the minimum holding torque limit and continue with step (a); d2) If the output member position variable leaves the stability range: proceed with step (c); e) if the pre-determined time span has elapsed: Proceed with step (b).

[0051] As mentioned before, the described holding torque mode is particularly suited as position maintaining mode for non-cogging torque motors. For cogging torque motors, a separate parking mode may additionally of alternatively be foreseen as position maintaining mode. In contrast to the holding torque mode that is generally executed under position control, the parking mode includes a switching into torque control. Taking advantage of the cogging torque, the electrical motor torque and therewith the motor current can be reduced. In particular embodiments the motor current and the motor torque can be reduced to zero if the cogging torque is high enough. The power consumption of the motor may accordingly be reduced to zero in the parking mode. In both modes, the holding torque mode and the parking mode, however, a stable position is automatically determined that can be maintained with minimum (holding torque mode) or potentially no (parking mode) power consumption respectively torque that is exerted by the motor. This stable position generally somewhat deviates from the target position.

[0052] The parking mode includes moving the rotor into a stable position that can be maintained without the phases being energized due to cogging; The parking mode may include, under torque control, setting a torque setpoint to zero. If in the parking mode the output member position variable respectively the output member and a thereto coupled load move out of a position tolerance range as mentioned before, the torque setpoint may be temporarily increased and the output member may be moved back into the stable position. A parking mode is described in more detail in application W02020 / 049079A1 .

[0053] The holding torque mode and parking mode as described before may, for determining and monitoring the output member position, rely on the output member position variable which is computed from the electrical rotor position as described before. This however, is not essential. The output member position and also the stability range may also be determined by way of an output member position sensor as discussed further below. Further, the rotor position may be evaluated rather than the output member position. In a variant, the rotor position is determined by way of a rotor position sensor, e.g. an optical or magnetically encoder as generally known in the art. In such a design, the rotor position determination routine based on measuring and computationally processing electrical variables of the power circuit and / or the motor as discussed before may not be present. Instead, the output member position variable may be determined respectively repeatedly updated based on a signal provided by the rotor position sensor. Also, the signal provided by the rotor position sensor may be used for controlling energization of the motor phases as generally known in the art.

[0054] It is specifically noted that, while the mechanical rotor position does generally not unambiguously define the output member position because of the reduction gear, each output member position corresponds, when ignoring backlash, to a particular mechanical rotor position. Once the mechanical rotor position is known for a target position of the output member, control of the motor can accordingly be carried out based on the mechanical rotor position similar to the computed output member position similar to the computed output member position respectively the output member position variable as generally used in the present disclosure. This applies for a holding torque mode and / or parking mode as well as for other control modes in accordance with the present disclosure. In an embodiment, the actuator includes or is configured to operatively couple to an output member position sensor. The output member position sensor is configured to provide a quantitative output member position signal that represents an actual mechanical output member position. The expression "quantitative" is to be understood as value-continuous or quasi-continuous, as opposed to binary. The sensor signal may be analogue or digital. In case of the sensor signal as such being analogue, the control unit generally includes corresponding analogue-to-digital converter circuitry. The output member position sensor may be an absolute position sensor respectively absolute position encoder. In another embodiment, the output member position sensor may be an incremental position sensor respectively incremental position encoder with an absolute reference.

[0055] The output member position sensor may in particular be or include a potentiometric encoder.

[0056] In further embodiments, the output member position sensor may be of a different type and may, e.g., be an optical encoder or another type of optical sensor, for example an optical distance sensor, a magnetic sensor or an inductive sensor, for example a magnetic encoder, eddy-current sensor or differential transformer. In principle, the information provided by the output member position sensor is redundant with the computed output member position. Such redundancy, however, is useful or even required in various applications in the interest of reliability and operational safety. Further, the output member position sensor may be used in the synchronization routine as discussed below.

[0057] The output member position sensor may be configured to measure the actual mechanical output member position directly at the output member. For example, a shaft of an encoder, e.g. a potentiometric encoder, may be directly connected with the output mem- ber. In other embodiments, however, the output member position sensor may be configured to measure the position of another element in unambiguous relation the output member position, e.g. gear wheel connected to the output member.

[0058] In an embodiment, the output member position sensor, in particular an encoder, may be coupled with the output member or another element as discussed above via a follower gear, with the encoder being coupled to the output-side of the follower gear. In an embodiment, the follower gear may ba a speed-increasing follower gear. Such speed-in- creasing follower gear translates a rotational movement angle at its input side into a larger angle at the output side. In the present context, such arrangement is useful if the encoder, for example potentiometric encoder, has a larger operational angle as compared to movement range of the output member or generally the element to which is coupled. By way of example, the output member may have a movement range of 90° and a potentiometric encoder may have an operational angle of 360°. A speed-increasing follower gear may be foreseen to fully exploit the operational angle and accordingly the resolution of the encoder. In another embodiment, the follower gear is a speed-decreasing follower gear. Such speed-decreasing follower gear translates a rotational movement angle at its input side into a smaller angle at the output side. In the present context, such arrangement is useful if a rotatory-to-linear transmission is used and more than one revolution of output member is required to achieve a linear target stroke.

[0059] Further in an embodiment, the output member position sensor may be an internal device of the actuator and be arranged with other parts, in particular the motor, the reduction gear and the control unit, in an actuator housing. In other embodiments, the output member position sensor can be arranged separately and coupled with the control unit via a wired or wireless communication link. By way of example, the output member position sensor may be arranged at the load and be configured to measure an absolute mechanical position of the load. In an embodiment with an output member position sensor as discussed above, the output member position variable could in principle be derived from the output member position signal respectively be given by the output member position signal also during general operation, rather than computing it based on the electrical rotor position. A determination based on the electrical rotor position, however, has the advantage of a generally better resolution.

[0060] In a particular embodiment with an output member position sensor, the control unit is configured to monitor, in particular continuously or regularly monitor, a relation between the output member position variable and the output member position signal. The control unit may be configured to trigger execution of the synchronization routine if the relation indicates the occurrence of an error condition. The error condition includes in particular a deviation between the computed output member position and the actual mechanical output member position.

[0061] In such embodiment, the computed output member position is accordingly continuously, substantially continuously or regularly checked against the actual mechanical output member position as determined by the output member position sensor. In case of a significant deviation, the synchronization routine is executed. A position deviation threshold is typically stored in form of a variable in the control unit. It may be unchangeable set by the manufacturer or may be configurable.

[0062] In an embodiment, the reference value to which the output member position variable is set in the synchronization routine may represent respectively be determined or computed based on the output member position signal as provided by the output member position sensor. Since the output member position signal directly represents the actual mechanical output member position, this kind of synchronization can be carried out generally at any time if needed and without requiring any special movement of the output member and the load for the purpose of synchronization. In an alternative embodiment, the synchronization routine includes detecting if the output member assumes a pre-determined reference output member position as discussed further below. Here, the output member position signal as provided by the output member position sensor only serves for detecting a condition in which the synchronization routine shall be executed.

[0063] In an embodiment, the actuator is configured to detect if the output member assumes a mechanically pre-determined reference output member position. The reference value represents the reference output member position. In such embodiment, no additional output member position sensor with a quantitative output member position signal e.g. potentiometric encoder, is in principle required. It may, however, optionally be present nevertheless. Generally, the synchronization routine involves in such an embodiment a movement of the output member to assume or pass the reference output member position, as discussed further below.

[0064] The pre-determined reference output member position is a mechanically fixed position that may be given by the device design or may be adjustable, as discussed further below. Further, detecting if the output member assumes a pre-determined reference output member position may be achieved in different ways as discussed below. In particular, the mechanical reference output member position may be defined via a reference position stop as a mechanical stop, or by a reference position detector.

[0065] The mechanically predetermined reference output member position may be given by design and accordingly known in advance, e.g. as a design-given end position stop. In this case, the reference value may be readily programmed respectively permanently stored in the control unit during the manufacture. As discussed further below in more detail, however, the mechanically pre-determined reference output member position may alternatively not be known in advance, for example in the case of an adjustable end position stop or end position switch as discussed further below. In an embodiment, the actuator is configured to execute a reference position search movement, the reference position search movement including moving the actuator until it is detected that the output member assumes the reference output member position, and setting the reference value in this position. The reference value may be set to a pre-determined value, for example zero.

[0066] In an embodiment, the actuator includes or is configured to operatively couple to a reference position detector for detecting if the output member assumes the reference output member position. The reference position detector may in particular be a reference position switch. It is noted that the reference position detector may be but is not necessarily realized as mechanical switch, but may also be realized, e.g., as inductive, optical or capacitive proximity switch. The expression "position detector" refers to a detector or sensor element that generally provides a binary signal, in contrast to an output member position sensor as quantitative sensor. It is noted that a detector, in particular a position detector, may also be realized by way of a sensor, in particular a position sensor, that provides as such a quantitative output signal, in combination with signal processing, e.g. a Schmitt trigger or threshold detector.

[0067] In an embodiment with a reference position detector, the mechanically pre-determined reference output member position is determined by the design of the reference position detector, for example reference position switch, and its mechanical arrangement. In some embodiments, the reference output member position is unchangeable given by the actuator design. In alternative embodiments, however, the reference position detector is arranged adjustably, thereby allowing an adjustment respectively setting of the reference output member position. In an embodiment, the reference output member position is defined by a reference position stop. The control unit may be configured to detect if the output member or a thereto coupled load hits the reference position stop. Similar to a reference position detector as discussed above, the reference position stop may be determined by the actuator design or may be adjustable. A reference position stop generally defines a fixed or adjustable end of the movement range and is accordingly an end position stop.

[0068] For detecting that the output member hits respectively has hit the reference position stop or generally a mechanical stop, the control unit may be configured to detect an overload situation. An overload situation may be detected ,e.g., via monitoring one or more phase currents and / or the motor torque, and or via variables derived therefrom, e.g. a time derivative respectively steepness of a current and / or torque increase. The motor torque may in principle be measured by way of a torque sensor. Alternatively or additionally, however, the motor torque may be computed by the control unit from the phase currents, or via an e.g. observer-based mathematical model as discussed above and further below. Advanced signal processing technics and data analytics may be used to detect the overload situation, e.g. artificial intelligence can be applied to detect a mechanical stop. Corresponding signal processing algorithms may be implemented in the control unit.

[0069] Further additionally or alternatively, one or more further sensors, such as a force sensor or acceleration sensor, may be included in the actuator and / or coupled to the control unit to detect the hitting of a mechanical stop. Identical of different threshold values may be foreseen for different stops. For example, for a design with two opposed end position stops, with either of them optionally being the reference position stop, different threshold values may optionally be foreseen.

[0070] In an embodiment, a threshold value, for example a current threshold value or torque threshold value for detecting a mechanical stop, for example the reference position stop or generally an end position stop, may be configurable. Threshold values may, for example, be selectable form a pre-defined list via an internal or external user interface of the actuator, and / or may be provided via a wired or wireless communication interface of the actuator.

[0071] In an embodiment with a mechanically pre-determined reference output member position, the synchronization routine may include controlling the motor to move the output member to assume the pre-determined reference output member position.

[0072] A synchronization routine that involves moving the output member to assume the reference output member position may generally be carried out as standard synchronization or as hidden synchronization. Standard synchronization means that motor is controlled to move the output member in a dedicated synchronization movement to assume the reference output member position, starting at any current output member position. Subsequent to executing the synchronization routine, the output member may be moved into any desired target position, for example a position prior to executing the synchronization routine. Standard synchronization may be carried out in particular if the output member position variable is void, e.g. due to an error condition.

[0073] Alternatively or additionally, the actuator may be configured for carrying out a hidden synchronization in the synchronization routine. In contrast to a standard synchronization, a hidden synchronization does generally not include a movement of the output member especially for the purpose of synchronization. For a hidden synchronization, the synchronization routine includes setting a synchronization indication by, e.g., setting a synchronization flag in case of a situation where synchronization should be carried out, without, however, directly controlling the motor to move the output member. The next time the output member is moved to assume the reference output member position during regular operation, the output member position variable is set to the reference value and the synchronization indication is cleared. For the hidden synchronization, the synchronization is accordingly executed in two distinct steps that are general not carried out directly one after the other. In the first step, it is defined that a synchronization should be carried out. In the second step, the output member position variable is set to the reference value and the synchronization indication is cleared during an actuation respectively a movement of the output member that occurs during regular operation. In this case, a generally undesired deviation between the actual mechanical position and the computed output member position is accordingly temporarily accepted. Such hidden synchronization may be executed, e.g. following a power interruption during which the load and the output member may have been moved due to external forces, e.g. by hand.

[0074] In an embodiment, the actuator is configured to only move the output member in a setting range, the setting range having a first and a second setting range end position. The setting range is typically smaller than respectively is a sub-range of a maximum moving range as determined by the actuator design.

[0075] In an embodiment, either or both of the first and / or second setting range end position respectively values representing setting range end positions are stored in the control unit. In an embodiment, either or both of the of the first and / or setting range end position may be configurable, for example user-settable, in particular via an internal or external user interface and / or via a wired or wireless communication link. A setting range end position that is not mechanically defined, in particular by a position detector or mechanical stop, but is stored as soft end position variable in the control unit, is also referred to as soft end position.

[0076] Configurable end position settings respectively soft end positions are in particular useful for adapting the actuator for use with different types of loads, for example different types of valves or dampers, or generally for different operational conditions. For example, setting range end positions may be used for adapting an actuator with a movement range of 90° for moving a damper blade of a damper having an operational range of 60°, or, adapting an actuator having a movement range of. e.g. 360° or an endless moving range for moving the valve member of a valve having an operational range of 180° or 270°, or for adjusting a linear operating range of a globe valve.

[0077] Configurable setting range end positions, for example, soft end positions, are interesting for special dampers designs e.g. 0 to 60° or specific valve types, using other opening ranges, e.g. 0 .. 180 or 0 .. 270 degrees, or globe valves.

[0078] Further in particular soft end positions are particularly useful in an HVAC application to define Kvs values respectively Cv values of a valve software-wise. The Kvs value expresses the amount of flow in m3 / hr of a fully open valve with produces a pressure drop of 1 bar. Cv is the equivalent coefficient, using Imperial instead of metric units (Kvs = Cv x 1 .03). The control valves have to be selected to have their Kvs respectively Cv values in a certain range to allow flow balancing.

[0079] Further, special end position settings that may deviate from the end position settings during regular operation may be used for testing and / or commissioning purposes. In particular if the setting range is temporarily set or modified for testing or commissioning, also the movement speed may be adjusted.

[0080] Soft end positions are favorable regarding the power consumption as well the mechanical robustness since they may reduce mechanical wear that would be unavoidable for mechanical stops. Likewise, the motor does not have to push against the mechanical stop and therefor consume energy, if the set respectively the target position of the output member is a soft end position. Also, they fully avoid the need for position sensors, such as mechanical switches, that are known to be susceptible to wear. Further, soft end positions are favorable regarding flexibility.

[0081] Generally, each of the first and second setting range end position may in principle be a soft setting range end position, defined by a mechanical stop or a position detector.

[0082] A mechanical stop defining the first respectively second setting range end position is referred to as first respectively second setting range end position stop. Similarly, a position detector defining the first respectively second setting range end position is referred to as first respectively second setting range end position detector.

[0083] Favorably, the control unit is configured to store values corresponding to the first and second setting range end position in a first and second setting range end position variable, respectively. The control unit may be configured to control the actuator, in particular the motor, to decelerate respective reduce the motor speed, e.g. by switching to a reduced motor speed, upon approaching a setting range end position. The switching position for switching to the reduced motor speed may be set, in particular by the actuator manufacturer, via an internal or external user interface, and / or via a wired or wireless, e.g. NFC-based communication interface. In a particular embodiment, the control unit may be configured to control the actuator, in particular the motor, to decelerate respective reduce the motor speed, e.g. by switching to a reduced motor speed, upon approaching a setting range end position in the gum seal region.

[0084] It is noted that a soft setting end position stop may be provided via a corresponding value for the output member position. Alternatively, one of the first setting range end position and the second setting range end position may be defined as an angular difference respectively movement angle relative to the other of the first and second setting range end position. For example, the first setting range end position may be defined by a first setting range and position stop or a first second range end position detector, and the second setting range and position may be defined by settable movement range of the actuator, e.g. 30° or 60°.

[0085] A setting range as discussed above may be realized in different configurations in particular as follows:

[0086] Both first and second setting range end position may be soft end positions.

[0087] Either of the first setting range end position and the second setting range end position is a soft end position respectively and the other setting range end position is defined by a first respectively second setting range end position stop. The setting range end position stop may be given by the actuator design or may be an adjustable mechanical stop. The setting range end position stop may optionally be at the same time a reference position stop as discussed above or may be an adjustable position stop.

[0088] Either of the first setting range end position and the second setting range end position is a soft end position and the other end position is defined by a first respectively second setting range end position detector. Such setting range end position detector may optionally be at the same time a reference position detector as discussed above, but may also be additional adjustable position detector.

[0089] Both setting range end positions are defined by a first and second setting end position stop. One of the setting range end position stops mechanical stops may be given by the actuator design, while the other setting range end position stop is an adjustable stop, or both setting range end position stops are adjustable stops.

[0090] Both setting range end positions are defined by a respective setting range end position detector, i.e. the first setting range end position is defined by a first setting range end position detector and the second setting range end position is defined by a second setting range end position detector. One of the setting range end position detectors may optionally at the same time be a reference position detector as discussed above.

[0091] In embodiments where both the first and the second setting range end position is in each case mechanical defined, either by a corresponding setting range end position detector or a setting range stop, an adaption routine as discussed further below is particularly useful.

[0092] A soft end position variable for a soft end position may be set using an output member position provided by an output member position sensor as discussed above. Further, a soft end position variable may be set in relation to a reference output member position that is defined by a reference position detector or reference position stop discussed above. Once the synchronization routine has been executed respectively as long as the output member position variable correctly reflects the actual output member position, the soft end position variable corresponds to respectively correctly reflects the soft end position. Further, one of the first and second setting range end positions may be defined as angular difference to the other of the first and second setting range end position as mentioned above.

[0093] The control unit is favorably configured to store values corresponding to the first respectively second setting range end position in a first respectively second setting range end position variable.

[0094] It is noted that mechanical stops as well as position detectors can also be provided at the load, for example at a damper or a valve, in particular at a globe valve, rather than as integral part of the actuator.

[0095] In a particular embodiment with a setting range, either of the first or second setting range end position is the reference output member position. In such embodiment, a first or second setting range end position stop is at the same time the reference position stop, or a first or second setting range end position sensor is at the same time the reference position detector as discussed above.

[0096] In a particular embodiment with a setting range, the setting range is mapped in the control unit to a setting value range, the setting value range having a minimum setting value and a maximum setting value. The minimum setting value corresponds to either of the first and second setting range end position, and the maximum setting value corresponds to the other of the first and second setting range end position. The setting value range respectively the minimum and maximum setting value are pre-determined independently from the physical movement range as defined by the first and second setting range end position. By changing the mapping of the minimum setting value to either the first and second end position and the maximum setting value to the other first and second end position it is further possible to allows the change the direction of rotation from a default setting, e.g. clock wise to counter clock wise.

[0097] For such type of embodiment, control of the actuator is possible based on setpoints. By way of example, the actuator may be configured to receive in position control mode a desired output member setpoint position or in speed control mode a desired speed setpoint which corresponds to a desired change rate of the output member position. Due to the mapping, control based on setpoints is independent of the specific technical setup. By way of example, if the output member has a mechanically possible movement range of 0° to 90 ° and an actually possible movement range of a thereto coupled damper blade is only in a range from 10° to 80° of the output member, the minimum setting value may correspond to 10° and the maximum setting value may correspond to 80°. In an embodiment, the setpoint is a percentage value, with the minimum setting value corresponding to 0% and the maximum setting value corresponding to 100%, or vice versa. In an embodiment, the control unit is configured to control a rotational speed and / or acceleration of the motor respectively the rotor in dependence of the setting range. The rotational speed and / or acceleration of the output member is accordingly also controlled in dependence of the setting range for such embodiment. The control unit may in particular be configured to set a set maximal rotational speed such that a time for moving the output member between the first end second setting range end position is independent from the angular difference between the first and second setting range end position. In such design, target values respectively set values for speed control are favorable provided in relation to the set maximal rotational speed, e.g. as percentage value, with 100% corresponding to the set maximal rotational speed. The time for moving between the end position settings is also referred to as running time and is typically generally configured by the manufacturer. In an embodiment, the running time may be configured or modified via a wired or wireless communication interface, e.g. an NFC communication interface.

[0098] In an embodiment with a setting range, the first setting end position is defined by a first setting end position stop or a first setting end position detector, and the second setting range end position is defined by a second setting end position stop or a second setting end position detector. The control unit may be configured to detect if the output member assumes either of the first setting range end position or the second setting range end position. The actuator may further be configured to execute an adaption routine. The adaption routine includes moving the output member between the first and second setting range end position and determining the setting range from the movement of the output member between the first and second setting range end position. Determining the setting range may in particular be done by the control unit.

[0099] An adaption routine is in particular useful in embodiments where either or both of the setting range end positions are defined by a respective adjustable setting range end position detector or setting and position stop. By way of the adaption routine, the actuator automatically learns the first and second setting range end position.

[0100] In an embodiment, the adaption routine is executed subsequent, favorable directly subsequent, to the synchronization routine. In particular synchronization and adaption may be carried out in combination, including moving the output member into either of the first and second setting range end position that at the same time is the reference output member position, followed by moving the output member into the other of the first and second setting range end position.

[0101] An application where adaption is particularly useful is in the actuation of globe valves. Here, the adaption routine allows the control unit to autonomously set the movement range of the output member in accordance with the specific valve.

[0102] It is noted that not necessarily two setting end position stops or two setting end position detectors, in particular end position switches, are foreseen. In some embodiments, a first setting end position stop and a second setting end position detector are foreseen, or vice versa. The first and / or second setting end position stop respectively the first and / or second setting end position detector may be adjustable as discussed before in the context of a reference position detector.

[0103] In a particular embodiment with a setting range, the actuator is configured to only move the output member in a control range in a position control mode, the control range being a subrange of the setting range, the control range having a first and second control end position. In an embodiment, the control range is mapped in the control unit to a control value range, the control value range having a minimum control value corresponding to either of the first and second control end position, and a maximum control value corresponding to the other of the first and second control end position. The minimum and maximum control value may be pre-determined independently from the physical movement range as defined by the first and second control end position. In an embodiment, the minimum control value is 0% and the maximum control value is 100%, or vice versa. In an embodiment with a control range as discussed, the actuator may be controlled in position control mode based on control values.

[0104] In an embodiment, the actuator further includes a clutch. The clutch is arranged in a power flow from the motor, specifically the rotor, to the output member. The clutch may in particular be arranged at a gear stage of the reduction gear. In further embodiments, however, it may in principle also be arranged, e.g., between the motor and the first stage of the reduction gear or between the last stage of the reduction gear and the output member. The clutch is switchable between an engaging configuration and a non-engaging configuration. The actuator may further include an engagement detector. The control unit may be configured to trigger execution of the synchronization routine in response to the engagement detector indicating a switching of the clutch from the non-engaging configuration into the engaging configuration.

[0105] The clutch may include a manually operable actuation element, e.g. in form of a push button, knob or lever for switching the clutch between the engaging and non-engaging configuration. In a particular embodiment, the actuation element is a rotatable lever, with a rotational axis of the lever being transverse, in particular perpendicular, to the rotational axis of the output member. The actuation element may act on an element of the reduction gear, e.g. a toothed wheel, via a linkage member. The linkage member may be linearly movable beared and may be configured to convert a rotational movement of the actuation element, in particular lever, into a linear movement. The linkage element may be configured to act as further lever. Other arrangements, however, may be used as well. In an embodiment, the clutch is configured for releasable locking in the non-engaging configuration. The engagement detector provides a signal, in particular a binary signal, that indicates whether the clutch is in the engaging or non-engaging configuration, respectively. The engagement detector may in particular be realized as electromechanical engagement switch or switching element. Alternatively to an electromechanical switch as structurally distinct component, a switching element may, e.g., be realized via a contact on a printed circuit of the control unit. Further, the engagement detector may also be realized, e.g., as capacitive or inductive switch. As discussed above in the context of position detectors, such as a reference position detector, the engagement detector may also be realized by way of a sensor that generally provides a quantitative output signal, in combination with corresponding signal processing. In a particular embodiment with an electromechanical engagement switch or switching element or generally an electrical contact, the electrical contact is open in the engaging configuration, i.e. during regular operation, and closed in the non-engaging configuration. In this way, regular operation is still possible in case of a failure of the electrical switch or switching element respectively of the electrical contact.

[0106] Upon switching from the engaging into the non-engaging configuration, the motor respectively the phases are favorably de-energized.

[0107] In the non-engaging configuration, all elements that are arranged in the power flow downstream of the clutch, in particular the output member and the thereto connected load, may be moved by external forces, e.g. manually by hand, without the elements upstream of the clutch, in particular the rotor of the motor, moving accordingly. Such manual movement of the motor may be required, e.g., during service or repair.

[0108] When moving the output member independently from the rotor, however, the correspondence between the actual mechanical output member position and the computed output member position is lost respectively becomes void. Synchronization is accordingly required after returning to the engaging configuration. Along with switching into the engaging configuration, the power supply of the motor is favorably restored respectively the phases are energized. The synchronization may generally be a standard synchronization or a hidden synchronization as discussed before.

[0109] In an embodiment, the actuator is configured to carry out the synchronization routine based on a user command. For providing the user command, the actuator may include a corresponding control element, such as a pushbutton. Further, in an embodiment, the actuator is configured to a receive a trigger command for executing the synchronization routine via a wired or wireless communication interface, e.g. an NFC interface as discussed above. In this case, a virtual pushbutton, e.g. on the touch screen of a smart phone or tablet computer or generally a mobile device may be foreseen for providing the user command that triggers execution of the synchronization routine.

[0110] In an embodiment, the actuator is configured to be powered via an external power supply. The control unit may be configured to detect an interruption of the powering via the external power supply and to store, in response to the interruption, recovery data, the recovery data being indicative of the output member position variable and optionally the electrical rotor position, in a non-volatile memory. The control unit may further be configured to detect a recovery of the powering via the external power supply and to read, in response to the recovery, the recovery data from the non-volatile memory. The nonvolatile memory is generally part of the control unit and may be, e.g., part of an ASIC.

[0111] In an embodiment, the control unit is further configured to trigger, in response to the recovery, the execution of the synchronization routine. The synchronization may generally be a standard synchronization or a hidden synchronization as discussed before. Provided that no movement has occurred in the period of interrupted power supply, the recovery data will generally be correct and in particular reflect the actual mechanical output member position. If, however, a manual movement has occurred, the recovery data may be incorrect or void. By executing the synchronization routine, the output member position variable can again be set correctly in accordance with the actual mechanical output member position after recovery of the external power supply.

[0112] In an embodiment, the actuator, in particular the control unit, is configured to trigger, in response to the recovery, in any case the execution of the synchronization routine. In another embodiment, the actuator, in particular the control unit, is configured, in response to the recovery, to trigger execution of the synchronization routine only in case of the computed output member position as read from the non-volatile memory in response to the recovery deviating from the actual mechanical output member position, or a deviation between the computed output member position as read from the non-volatile memory in response to the recovery and the actual mechanical output member position exceeding a generally pre-determined position deviation threshold. In such embodiment, an output member position sensor is generally present and the actuator, in particular the control unit, is configured to evaluate the output member position signal in response to the recovery.

[0113] In an embodiment, the control unit is configured to adapt the rotor position determination routine in dependence of a rotatory speed of the rotor. The adaption of the rotor position determination routine may in particular be or include a switching between alternative rotor position determination routines.

[0114] Regarding a determination of the electrical rotor position via electrical variables of the power circuit and / or the motor respectively in a sensorless manner, a variety of methods is generally known in the art as discussed above, each having specific characteristics and advantages respectively drawbacks. An adaption of the rotor position determination routine allows to fit the rotor position determination routine to the operation conditions. Additionally or alternatively to switching between alternative rotor position determination routines, the adaption may include adapting operational parameters of the rotor position determination routine in a continuous or non-continuous respectively switched manner.

[0115] In a particular embodiment with adaption of the rotor position determination routine as discussed, the rotor position determination routine includes a low speed rotor position determination routine and a high speed rotor position determination routine. The control unit may be configured to switch between determining the electrical rotor position either according to the low speed rotor position determination routine or according to the high speed rotor position determination routine in dependence of the rotatory speed of the rotor. A rotational speed at which the switching occurs is also referred to as switching speed.

[0116] In a typical design of the actuator, the motor may be designed for a maximal rotational speed of, e.g., about 4500rpm (revolutions per minute), with the switching between the low speed rotor position determination routine and the high speed rotor position determination routine between 500rpm and lOOOrpm. Other motor designs with other maximal rotational speeds and / or switching speeds may be used as well. For switching between the low speed rotor position determination routine and the high speed rotor position determination routine, a rotational speed threshold may be foreseen.

[0117] Rotor position determination routines that are particular suited at low rotor speeds, including stillstand, are generally associated with undesired fluctuations of the generated torque respectively a loss of torque. This results from the fact the position determination routines generally involve a temporary modification respectively disruption of the commutation, respectively the energizing of the phases. Such fluctuation or loss of torque is in typical applications acceptable at low rotational speeds, but is particularly disadvantageous at higher speeds. Switching between alternative rotor position determination routines allows selecting an appropriate routine in dependence of the rotational speed.

[0118] In an embodiment, the rotor position determination routine includes an inductance-based rotor position determination routine. The inductance-based rotor position determination routine includes measuring an inductance or a therewith correlated variable for at least one phase, in particular each of the phases, and computing the electrical rotor position from the measured inductance(s) or therewith correlated variable(s). A variable correlated with the inductance may in particular be a time derivative of a phase current respectively a phase current change. Inductance-based rotor position determination as here-described is possible for motors where the measurable inductances vary periodically with the electrical rotor position, such as brushless permanent-magnet (PM) motors as discussed before. The inductance change in the phases results from the fact that the phase inductance, or generally the inductivity of an electric coil, varies with an external magnetic field. In the here-discussed context, the magnetic field is the magnetic field of the permanent magnets which periodically varies for each of the phases with the electrical angle. Such inductance-based rotor position determination routine may in particular serve as low speed rotor position determination routine.

[0119] In an embodiment, the rotor position determination routine includes an inductance-based rotor position determination routine. The inductance-based rotor position determination routine includes applying a sequence of test voltage vectors to at least two phases, determining resulting test phase current changes and evaluating a relation between the test voltage vectors and the resulting test phase current changes. In an embodiment with switchable rotor position determination routine, the inductance-based rotor position determination routine may in particular serve as low speed rotor position determination routine. A representative for such inductance-based rotor position determination routine is the INFORM method as discussed above. According to this method, at least two test voltage vectors are sequentially applied to at least two phases, and the resulting current change is in each case measured. In a typical realization, each test voltage vector has a test voltage for one of the phases, while the voltages for the other phases are zero. Typically, the absolute value of the test voltage is identical for all test voltage vectors. That is, the test voltage is sequentially applied to at least two phases. While other implementations may be used as well, a typical implementation includes sequentially applying a respective test voltage vector respectively the test voltage sequentially to each phase. In combination, the current changes define a complex vector, the argument of which comprises the electrical rotor position. Other methods as known in the art may be used as well. As discussed further below, the voltage may further be applied to the phases sequentially with opposite polarities.

[0120] The rotor position determination routine, in particular the low speed rotor position determination routine, is configured to determine the electrical rotor position in the angle of 360°, respectively a full period. Typical routines for determining the electrical rotor position based on measuring and processing electrical variables, such as the INFORM method and other inductance-based methods, however, may generally not determine the true electrical angle, referred to as <pelectric, but only a thereto related auxiliary angle, referred to as <paux= 2<pelectric. The auxiliary angle <pauxaccordingly varies with the double frequency of the electrical angle <pelectricandeach value of the auxiliary angle yauxaccordingly corresponds to two potential values for the electrical angle <pelectric. The resulting ambiguity for the electrical angle <pelectricis referred to as 180°-ambiguity. Once an initial value for the for the electrical angle <pelectrichas been correctly determined respectively the 180°-ambiguity is resolved, the electrical angle <pelectriccan be continuously computed respectively updated by way of comparison with a previously determined value. As discussed further below in more detail, an initial value may in particular be determined at stillstand. The rotor position determination routine is accordingly configured for resolving the 180° ambiguity of the electrical rotor position, in particular at stillstand.

[0121] In a particular embodiment with an inductance-bases rotor position determination routine, the actuator is configured to execute a stillstand rotor position determination routine. The stillstand rotor position determination routine includes, at rotor stillstand, executing the steps of:

[0122] - carrying out the inductance-based rotor position determination routine,

[0123] - energizing the phases with a first operating point current vector, the first operating point current vector generating a first operating point stator field with magnetic saturation without resulting in a torque being exerted on the rotor,

[0124] - applying, while energizing the phases with the first operating point current vector, a first sequence of test voltage vectors to at least two phases and determining resulting first test phase current changes,

[0125] - energizing the phases with a second operating point current vector, the second operating point current vector generating a second operating point stator field with magnetic saturation, the second operating point current vector being collinear with the first operating point current vector,

[0126] - applying, while energizing the phases with the second operating point current vector, a second sequence of test voltage vectors to at least two phases and determining resulting second test phase current changes,

[0127] - evaluating a relation between the resulting first test phase current changes and second test phase current changes.

[0128] The stillstand rotor position determination routine allows resolving the before-discussed 180°-ambiguity. In particular, the relation between the first and second test phase current changes are different for the two alternative values for the electrical angle <pelectricthat are associated with the same auxiliary angle <paux. Via the inductance-based rotor position determination routine at the beginning, the auxiliary angle <pelectric'sfirst determined, and via the subsequent steps the 180°-ambiguity is resolved. It is noted that the required axis of the first and second operating point current vector corresponds to respectively is parallel to the axis of the magnetic flux in the complex plane and can in any case be determined from the auxiliary angle <pauxas determined via the inductancebased position determination routine, as generally known in the art, prior to the 180°- uncertainty being resolved.

[0129] Since the direction of the first and second operating point current vector is designed in a way such that it does not produce a torque and the second operating point current vector is collinear with the first operating point current vector, also the second operating point current vector does not produce a torque. No movement of the rotor accordingly occurs.

[0130] Generally, the test phase current changes will be different for the first and second operating point current vector. Evaluating a relation between the resulting first test phase current changes and second test phase current changes may in particular include assessing which of the first and second test phase current changes is larger. For the operating point current vector that is aligned with respectively is parallel to the magnetic flux generated by the permanent magnets, the total flux is increased and the test phase current change is larger as compared the other operating point current vector that is antiparallel to the magnetic flux generated by the permanent magnets and accordingly decreases the total magnetic flux. It is noted that the first respectively second test phase current changes are to be understood as a respective test phase current change per phase, forming, in combination, a test phase current change vector. There may accordingly be a first test phase current change vector associated with the first operating point current vector and the first sequence of test voltage vectors, as well as a second test phase current change vector associated with the second operating point current vector and the second sequence of test voltage vectors. Evaluating which of the first and second test phase current changes is larger may be or include comparing the magnitudes of the first and second test phase current change vector.

[0131] Applying a sequence of test voltage vectors in series allows evaluating the respective test phase current change sequentially for each of the phases and combining the test phase change current vector from the sequentially measured test phase change currents.

[0132] Further approaches and procedures for resolving the 180° ambiguity, as described, e.g., in the work of Thomas SZALAI or the paper by Manfred Schroedl regarding the INFORM- method, both mentioned above, may be used as well.

[0133] In a particular embodiment with a stillstand rotor position determination routine of the before-discussed type, the first and second operating point current vector are in each case continuously built up over time. The magnetic stator fields that are generated by the first and second operating point current vectors need to result in magnetic saturation. In a particularly favorable variant, the absolute value of the current vector (Id) is half of the nominal current of the motor.

[0134] Building up such magnetic fields quickly respectively in a short timeframe is accompanied by undesired noise. Such noise is prevented by building the operation point currents up continuously over an extended time of, e.g., 3ms for the time constant of the motor being 0.3ms.

[0135] In a particular embodiment with stillstand rotor position determination routine, the first operating point current vector and the second operating point current vector have identical absolute values and opposite directions. For such embodiment, the first and second operating point current vector cancel each other out. In principle, however, the first and second operating point current vectors may have the same direction and different absolute values. It is noted that either of the first operating point current vector or the second operating point current vector may in principle also be a zero-vector where the phase current is zero for each of the phases.

[0136] In a particular embodiment with stillstand rotor position determination routine, the first sequence of test voltage vectors and the second sequence of test voltage vectors are identical.

[0137] In a particular embodiment with a stillstand rotor position determination routine, applying the first sequence of test voltage vectors and the second sequence of test voltage vectors includes in each case applying a test voltage sequentially to at least two phases, in particular to each of the phases. For such embodiment which is favorable regarding an efficient technical implementation, each test vector of a sequence of test voltage vectors accordingly comprises a test voltage in a component associated with one of the phases, with the components of the other phases being in each case zero. In an embodiment, the absolute value of the non-zero component is identical for each of the test voltage vectors of the series.

[0138] In a particular embodiment with an inductance-bases rotor position determination routine, the control unit is configured to sequentially measure a respective phase current of at least two phases, in particular of each of the phases. In a particular embodiment, the control unit includes a common measurement shunt for sequentially measuring the at least two phase currents, in particular of each of the phases.

[0139] Sequential measurement of the phase currents is particularly useful for measuring current changes in the phases in the context of rotor position determination as discussed above, as well as for monitoring, controlling and / or limiting the torque applied by the actuator. A sequential measurement via a common measurement shunt has the advantage that only a single measurement shunt is needed. It is noted that any tolerances of the measurement shunt directly cause a corresponding error of the measured phase currents. By using a single measurement shunt it is ensured that no different measurement errors are present for different phases. Sequential phase current measurement via a common shunt can be achieved by energizing the at least two phases, in particular each of the e.g. three phases, sequentially, one after the other via the measurement shunt. Corresponding circuit designs are as such known in the art.

[0140] In a particular embodiment with energization of the motor phases using PWM as discussed before and an inductance-based rotor position determination routine as discussed before, a pre-determined part of each PWM cycle is reserved for inductance measurement, i.e. applying at least one test voltage vector and determining the resulting at least one test phase current changes. This portion of a PWM cylce is referred to as measurement portion. The other generally longer portion of a PWM cycle is used for control and is referred to as torque control portion. The torque control portion and the measurement portion may be arranged time wise sequentially in a PWM cycle, with the measurement portion being at the beginning or end of each PWM cycle. Typically, the measurement cycle may be, e.g., the last 30% of each cycle while the preceding 70% serve as torque control portion.

[0141] In a particular design of the before-described type, executing the inductance-based rotor position determination routine, specifically applying the sequence of test voltage vectors and determining the resulting test phase current changes is distributed over a number of consecutive PWM cycles, in particular directly consecutive PWM cycles. In each PWM cycle respectively its measurement portion, a respective test voltage vector is applied to one of the phases and the resulting test phase current change is measured. If the steps of applying a respective test voltage vector and determining the resulting test phase current changes, the number of PWM cycles that is required for an inductance-based rotor position determination may accordingly correspond to the number of phases, e.g. three or may be twice the number of phases if test voltages of two polarities are used as discussed below. In a favourable design, the rotor position determination is done in a sliding manner. That is, a rotor position determination is executed for each PWM cycle, using the last available measurement respectively impedance determination for each phase.

[0142] Reserving a pre-determined portion of each PWM cycle for inductance measurement has the particular advantage of decoupling the inductance measurement and the torque generation. However, it is noted that the effective maximal voltage that can be provided to the motor respectively its phases is reduced in accordance with the relative duration of the torque control portion in relation to duration of the PWM cycle.

[0143] In an embodiment with inductance based rotor position determination unit, the sequence of test voltage vectors comprises for at least two phases, in particular for each phase, a respective first test voltage vector and a respective second test voltage vector, wherein the polarity of the test voltage is reversed for the second test voltage vector as compared to the first test voltage vector. That is, two test voltages of opposite polarity may be sequentially applied to each phase. For e.g. three phases, a total of six test voltage vectors may accordingly be used. With P1 , P2, P3, indicating three phases in consecutive order and "+", "-" indicating the opposite polarities of the test voltage, the sequence of test voltage vectors may accordingly be "+P1", "-P1", "+P2", "-P2", "+P3", "-P3". It has been found that such procedure minimizes or avoids generally disturbing acoustic noise that may result from applying the test voltages. It is noted, however, that the polarities and / or order of the phases may also be chosen differently, for example as random order. In an embodiment, the rotor position determination routine includes a back-EMF-based rotor position determination routine. The back-EMF-based rotor position determination routine includes processing at least one back-EMF generated in at least one phase. The back-EMF based rotor position determination routine may in particular include processing the back-EMF generated in each of the phases. The back-EMF-based rotor position determination routine may in particular be the high speed rotor position determination routine.

[0144] In an embodiment, the back-EMF based rotor position determination routine includes processing the zero-crossing of the back-EMF generated in at least one of the phases, in particular each of the phases. In such embodiment, the control unit is configured to detect zero-crossings of the back-EMF generated in at least one phase, in particular the respective back-EMF generated in each of the phases, and processing the back-EMF or back-EMFs includes evaluating the respective zero-crossings as a function of time. As generally known, two zero-crossings occur for each electrical period, with the zero-crossings being phase-shift in dependence of the number of phases, e.g. 120° for three phases. Based on the zero-crossings, the output member position variable may accordingly be continuously updated as generally known in the art.

[0145] In a further embodiment, the back- EMF-based rotor position determination routine includes real-time sampling and processing a course of the back-EMF generated in at least one of the phases, in particular in each of the phases. Real time processing of the back- EMF may include sampling the back-EMF at a constant or a time variant sampling rate. Sampling may also be adjusted in function of the rotor speed, e.g. to get a similar amount of samples for each electrical period. In such embodiment, the control unit is configured for real-time measurement of the back-EMF generated in at least one phase, in particular the respective back-EMF generated in each of the phases. Measuring and evaluating quantitative back-EMF is more complex but generally allows a determination of the electrical rotor position with higher accuracy as compared to the evaluation of zero-crossings only.

[0146] In an embodiment, a back-EMF-based rotor position determination routine, in particular a routine based on evaluating quantitative values of the back-EMF, includes a motormodel, for example an observer-based motor model as discussed above, with the model being configured for evaluating the measured back-EMF of back-EMFs in real time. In an embodiment, the observer-based motor model includes a Kalman filter.

[0147] In an embodiment, the control unit is configured to energize the phases to generate torque on the rotor in a pre-determined direction. For this purpose, the control unit may be configured for individually controlling the phase voltage and / or phase current for each phase. In combination, the phase currents define a current vector. In this way, the direction and favorable the amount of the generated torque may be adjusted and controlled as needed. In particular operating point current vectors that do not result in a torque being exerted on the rotor as discussed before may be produced.

[0148] In an embodiment, the control unit is configured to energize the phases in each case with a respective continuously varying phase current. Time varying drive currents may in particular be realized via PWM (Pulse Width Modulation) as generally known in the art. In particular, the control unit may be configured to energize the phases by generating sinusoidal (sinus commutation) or quasi sinusoidal waveform outputs, in particular by using Pulse-Width Modulation.

[0149] In a particular embodiment, the control unit is configured for Third Harmonic Injection (TH I) as in principle known in the art, the output voltages that are provided of the control unit for energizing the, e.g., three phases of the motor are, as such not sinusoidal when measured against a reference potential, in particular ground (GND) potential. Instead the individual output voltages correspond in a strict or approximated manner to the superimposition of a sinusoidal base signal with a further sinusoidal superimposed signal. The superimposed signal has a lower amplitude of, e.g., 15% of the base signal, and a three times higher frequency (i.e. the third harmonic), with the phase of both signals being identical. It can be shown that, for each of the outputs, the resulting voltage as measured against a common reference potential, e.g. ground (GND), is no longer sinusoidal but closer to a square signal, having the same fundamental frequency and phase as the base signal. The amplitude of the resulting output voltage as measured against ground is in this case lower than for the sinusoidal base signal, allowing to increase the base signal amplitude and therewith the torque without saturating exceeding the output voltage. The linked voltage that can be applied to the motor without exceeding the voltage of the motor controller is increased by typically about 15%. Hence it is possible to generate with the motor maximum torque that is about 15% higher and a speed at no load that is also about 15% higher as compared to ordinary sinusoidal energization of the motor phases.

[0150] TH I is particularly favourable in combination with an impedance rotor position determination where a part of each PWM cycle is reserved for applying test voltage vectors respectively impedance measurement. As discussed above, the available voltage that can be applied by the motor is generally reduced in this case. TH I allows to fully or at least partly compensate this generally undesirable effect.

[0151] In an embodiment, the control unit, in particular the power circuit of the control unit, is configured to provide a voltage output to the motor phases. Defined respectively desired phase currents, as required e.g. for torque control, may be converted by the control unit into a corresponding voltage output. In a further embodiment, vector control respectively field oriented control (FOC) is applied to provide the voltage output to the motor phases to generate the phase currents required for controlling the torque of the motor.

[0152] In an embodiment, the control unit is configured to store a number of auxiliary output member positions, the auxiliary output member positions being in particular configurable. The control unit may be configured to compare, in particular continuously compare, the computed output member position respectively a current value of the output member position variable with auxiliary output member position variables, each auxiliary output member variable representing an auxiliary output member position. The control unit may be configured to provide a corresponding auxiliary signal if the computed output member position is larger or smaller than a threshold defined by at least an auxiliary output member position respectively the output member position variable is larger or smaller than an auxiliary output member position variable. Typically, a separate auxiliary signal is foreseen for each auxiliary output member position. The number of auxiliary output member positions may generally be any number, including zero or one. An auxiliary signal may, e.g., change its sign or logical value as output member passes through the respective auxiliary output member position. In a further variant, an auxiliary output signal is a pulse signal with a pulse being generated as the output member assumes or passes the respective auxiliary output member position.

[0153] Auxiliary output member position variables that represent auxiliary output member positions may be stored in the control unit in each case in a corresponding register, generally in the same way as the computed output member position. Favorably, the registers are stored in a non-volatile memory and are accordingly maintained in the event of a power interruption respectively in a powerless state.

[0154] Auxiliary output member positions and auxiliary signals may be realized for any desired position or positions of the movement range of the output member. Via auxiliary output member positions, virtual, i.e. non-physical, auxiliary position detectors respectively position switches may be realized. The corresponding auxiliary signals may be used, e. g., for triggering actions e.g. in an HVAC system or fire protection systems. Particularly, they may be used for switching further devices, such as pumps.

[0155] For setting or configuring auxiliary output member positions, an internal or external user interface may be used. Specifically, values representing auxiliary output member positions may be entered via a user interface and / or be transmitted to the control unit via a wired or wireless communication interface. In a particular embodiment, the actuator, in particular the control unit, is configured for receiving values representing auxiliary output member position via an NFC communication interface, for example a powerless NFC communication interface that is wirelessly powered via the NFC link as discussed above. The auxiliary positions may preferably be stored in a non-volatile memory of an NFC circuit as part of the control unit. The same may apply for further configurable parameters and values as discussed above and / or further below.

[0156] The auxiliary signal or auxiliary signals may be communicated by a wired or wireless communication interface. Alternatively or additionally, a physical auxiliary output port may be provided corresponding to one, some or all auxiliary output member positions and a voltage level or current level at the port may be switched as the computed output member position assumes the respective auxiliary output member position. Further, a physical output port may be designed or configured as switch, in particular solid-state, e.g. transistor based switch that is switched between a conducting and an alternative non conducting state. Via such design, the behavior of electro-mechanical switches or contacts, for example relay contacts, may be simulated.

[0157] An auxiliary physical output port is favorable for switching devices such as pumps. In an embodiment, two physical output ports are associated with one and the same auxiliary signal, with the two physical outputs being complementary and toggling and switching in each case upon the computed output member position corresponding to assuming the respective auxiliary output member position, respectively the output member passing through the respective auxiliary output member position. In this way, an electro-mechanical toggling switch respectively a latching relay that switches upon an auxiliary output member position is assumed, can be simulated.

[0158] In an embodiment, the actuator is configured to switch into a power saving mode upon the output member and a thereto coupled load assuming a target position. In the power saving mode, the phase currents may be reduced or the motor may be de-energized. The control unit may be configured to monitor the rotor position in the power saving mode by continuously or repeatedly executing the rotor position determination routine, in particular a low speed rotor position determination routine as discussed above. The control unit may be further configured to increase the phase currents or energize the phases upon the electrical rotor position indicating a rotor movement. In this way, the energy consumption as well as the thermal and mechanical load may be significantly reduced, while ensuring that the output member is kept in the target position.

[0159] In an embodiment, the control unit is configured, upon the output member or the load hitting a mechanical stop, to control the motor to execute a release movement, with a moving direction of the release movement being opposite to the movement direction when hitting the mechanical stop. Via the release moment, the mechanics and in particular the reduction gear of the actuator are released. The amount of movement for the release movement is favorably sufficiently small not to significantly alter the output member position and the position of thereto coupled load, and accordingly the fluid flow. By way of example, the movement for the release movement may be in the range of few degrees. For example, for a typical ball valve as control valve the range of no flow for the valve member may be from 0°to to 5° or even from 0° to 20° and the release movement may be selected accordingly.

[0160] A release movement has the advantage of reducing the mechanical load and stress for the actuator as well as for the load, thereby increasing the life time.

[0161] In an embodiment, the control unit is configured to control the motor, while generally maintaining a target position of the output member, to periodically execute a break-loose routine. The break-loose routine includes moving the output member out of the target position and back into the target position. Control of the break-loose routine is based on the computed output member position respectively the output member position variable. In this context, the possibility for sensorless motor control in accordance with the present disclosure is particularly advantageous.

[0162] Such periodic break-loose is particularly favorable in applications where the actuator is used to control a valve respectively where the load is the valve member of a valve that is moved only seldom in regular operation. Due to the periodical movement, sticking is prevented. The movement is typically small, e.g. a few degrees and may be selected not to influence the fluid flow as discussed before in the context of a release movement. In an embodiment, the amount of movement in the break loose routine and / or a time-interval for executing the break-loose movement are configurable. A typical time interval may, e.g., be weekly.

[0163] In an embodiment, the control unit is configured to control the motor, in particular to control energizing of the phases, to reduce the motor speed upon the computed output member position approaching a pre-determined mechanical stop position. In this way, it can be ensured that the output member and / or the load approach a mechanical stop with low respectively reduced speed. The control unit may be configured to store a mechanical stop position variable, the mechanical stop position variable reflecting respectively corresponding to the mechanical stop position. The control unit may further be configured for continuously or quasi-continuously checking the output member position variable against the mechanical stop position variable. The mechanical stop position may be given by the design of the actuator and / or the load, or may be an adjustable stop, for example an adjustable setting end position stop as discussed before. It is noted that also more than one mechanical stop may be present, in particular two mechanical stops. The control unit may accordingly be configured to store a number of more than one, e.g. two, stop position variables.

[0164] Reducing the speed for approaching a mechanical stop may, for example include switching the motor speed to a pre-determined slow speed, or reducing the motor speed step- wise and / or reducing the motor speed in a continuous or substantially continuous manner.

[0165] Approaching a mechanical stop with reduced speed is favorably enabled for an actuator in accordance with the present disclosure, since it allows the sensorless motor control and correct determination of the electrical rotor position in particular at low speeds up to and including stillstand without loss of the correct electrical rotor position respectively the computed electrical rotor position becoming potentially incorrect or void.

[0166] In a further aspect, the present disclosure concerns an HVAC assembly. The HVAC assembly includes an actuator according any embodiment as discussed above and / or further below. The HVAC assembly further includes a fluid flow control device, the fluid flow control device being in particular a valve or damper. A fluid flow regulating member of the fluid flow control device is coupled to the output member of the actuator. In a further aspect, the present disclosure concerns an HVAC system. The HVAC system includes at least one HVAC assembly according to any embodiment as discussed above and / or further below. The HVAC system further includes an HVAC system control unit. The HVAC system control unit is operatively coupled to the actuator of at least one each HVAC assembly and is configured for controlling operating of the actuator of each HVAC assembly. In a typical design, a number of HVAC assemblies is present with the actuators of at least one of the HVAC assemblies, in particular each of the HVAC assemblies, being controlled by the HVAC system control unit.

[0167] In a further aspect, the present disclosure generally concerns an actuator for moving a load in an HVAC system, the load being a fluid flow regulating member, in particular a valve member of a valve or a damper blade of a damper. The actuator includes a motor. Exemplarily but not necessarily, the motor is a brushless permanent-magnet motor having a permanent-magnet rotor and a stator with a at least two phases. Alternatively, the motor may be another type of motor, such as a conventional DC motor with brushes.

[0168] The actuator further includes a gear unit, wherein an input side of the gear unit is coupled to the rotor and an output member of the gear unit is configured for coupling to the load.

[0169] The actuator includes a control unit. The control unit is configured for controlling operation of the motor. The control unit is further configured for repeatedly determining an output member position and / or updating an output member position variable. The output member position may be determined by way of an output member position sensor as discussed before. Further, an output member position variable may be determined by way of electrical measurement at the motor as discussed before, and / or using a sensor, for example using an optical or magnetic encoder at the rotor of the motor. The actuator may be configured to operate in one or more control modes as discussed above and / or further below. In particular, the actuator may be operated in a parking mode and / or a holding torque mode. Further, the actuator respectively its control unit may, e.g. be configured for Third Harmonic Injection (THI).

[0170] BRIEF DESCRIPTION OF THE DRAWINGS

[0171] The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

[0172] Fig. 1 shows a first exemplary embodiment of an HVAC assembly;

[0173] Fig. 2 shows a second exemplary embodiment of an HVAC assembly;

[0174] Fig. 3 sow an exemplary embodiment of an actuator in a functional view;

[0175] Fig. 4 shows further details and aspects of the actuator of Fig. 3 in a functional view;

[0176] Fig. 5 schematically shows an example for an inductance variation for a phase of a brushless permanent-magnet motor in dependence of the rotor position;

[0177] Fig. 6 schematically illustrates an example for defining a setting range;

[0178] Fig. 7 schematically illustrates another example for defining a setting range;

[0179] Fig. 8 schematically illustrates another example for defining a setting range; Fig. 9 shows a partial internal view of an embodiment of an actuator with a clutch in the engaging configuration of the clutch;

[0180] Fig. 10 a view corresponding to Figure 8 in the non-engaging configuration of the clutch;

[0181] Fig. 11 the operating element of a clutch in the engaging configuration;

[0182] Fig. 12 a view corresponding to Figure 11 in the non-engaging configuration;

[0183] Fig. 13 an example for the application of test voltage vectors for inductance-based rotor position determination;

[0184] Fig. 14 aspects of the control structure of an embodiment of an actuator;

[0185] Fig. 15 an example of a position tolerance range and setting range for holding torque control;

[0186] Fig. 16 an operational flow for a holding torque mode.

[0187] DESCRIPTION OF THE EMBODIMENTS

[0188] Figure 1 shows a first embodiment of an HVAC assembly in accordance with the present disclosure with an actuator 1 and a fluid flow control device which is in this design a ball valve 2, but may also be another type of valve as used in HVAC systems. The actuator 1 is a rotatory actuator with an actuator-sided interface structure 11. The ball valve 2 has a corresponding fluid flow regulating device-sided interface structure 21 , with the interface structures 11 , 21 being designed for mutual engagement. The ball valve 2 comprises a control shaft 22 that is coupled to or integral with a ball (not visible in Figure 1) as fluid flow regulating member of the ball valve 1. In Figure 1 , the ball valve 1 and the actuator 2 are shown spaced with respect to each other along a coupling axis. Upon moving the actuator 1 towards the ball valve 2 along the coupling axis 2 and engaging the interface structures 11 , 21 , the control shaft 22 will engage an output member (not visible in Figure 1).

[0189] Figure 2 schematically illustrates a second embodiment of an HVAC assembly. In this embodiment, the fluid flow control device is a damper 2'. The damper 2' includes a duct 23 in which a damper blade 24 as flow regulating member is rotatably arranged. The rotatory output member 12 of the actuator 1 is in this arrangement coupled with the damper blade 24 via a linkage 22'. Figure 2 shows the configuration where the flow channel of the duct 23 is fully closed by the damper blade 24 in solid lines and a configuration where the flow channel is fully opened in dashed lines for the linkage 22' and the damper blade 24. It is noted that the arrangement of Figure 1 and Figure 2 are merely exemplary. Other arrangements as generally known in the art may be used as well.

[0190] Figure 3 schematically shows an embodiment of an actuator 1 in a functional view as block diagram. The actuator 1 of Figure 3 may be used in a fluid flow control device, e.g. of Figure 1 or Figure 2, but also in other setups. Major functional couplings of mechanical elements or components are indicated by dashed lines.

[0191] The actuator 1 comprises a motor 15 in form of a brushless permanent-magnet motor in accordance with the general description above. For exemplary purposes, the motor 15 is here assumed to have three phases. A rotor (not individually shown) of the motor 15 is coupled to the input side of a reduction gear 16 as gear unit. An output member 12 is driven by the motor 15 via the reduction gear 16 is designed for coupling to flow regulating member as load. While shown separately, the output member 12 may optionally form a functional part of the reduction gear 16. The reduction gear 16 may, e.g., be realized as a spur gearbox with toothed wheels, has a first gear part 16.1 (e.g. a primary gear) and a second gear part 16.2 (e.g. a secondary gear) that are arranged sequentially in the power flow. Typical gear ratios may, e.g., be in a range of 1 :300 up to 1 :10000.

[0192] In the shown design, the actuator 1 further comprises an optional clutch 17. The clutch 17 is configured for selectively interrupting the power flow in the reduction gear 16 respectively selectively disengaging power transmitting elements, for example spur wheels, between the first gear part 16.1 and the second gear part 16.2 in a non-engaging configuration. The clutch 17 may have an actuation device 17.1 that is arranged to act on a torque transmitting element, e.g. a toothed wheel as mentioned before of the first gear part 16.1 or the second gear part 16.2. By way of example, a toothed wheel of the first gear part 16.1 or the second gear part 16.2 may be arranged axially movable on its rotational axis and may generally be forced into engagement via a spring member, e.g. a cup spring (not individually shown) in the engaging configuration of the clutch. Via the actuation device, said toothed wheel may be axially displaced against a force exerted by the cup spring into the non-engaging configuration. Other arrangements may be used as well.

[0193] The clutch 17 further includes a manually operable lever 17.2 as actuation element that acts on the actuation device 17.1 for switching the clutch 17 between the engaging and the non-engaging configuration. Favorably, the clutch 17 latches in the non-engaging configuration. In a particular embodiment, a latching tab is integrated in the lever 17.2 which can be pressed into a recess of an actuator housing when the clutch is in the nonengaging configuration in order to lock the clutch in the non-engaging configuration.

[0194] The actuator 1 further includes a control unit 13. The control unit 13 is generally an electronic device and includes the control and supervision functionality of the actuator. The control unit 13 includes both signal and data processing units as well as the power circuit required for driving the motor 15 respectively energizing the motor phases. The control unit 13 may generally include a plurality of passive and active components as generally known in the art and may in particular include one or more microcontrollers, microcomputers and / or ASICs. In a particular design, a core element that implements the control functionally is realized by an ASIC. Particular design features and functions of the control unit 13 are discussed in the general description above and as well as further below.

[0195] In the shown design, the actuator 1 is designed to be connected to and be powered via an external power supply (not shown). The actuator 1 includes a power supply unit 14 with a power line terminal 141. The power supply unit 14 provides power to the control unit 13 and to the motor 15 via the control unit 13.

[0196] In the shown design, the actuator 1 includes an output member position sensor, exemplarily realized by a potentiometric encoder 18. The potentiometric encoder 18 is coupled to the output member12, optionally via a speed-increasing follower gear (not separately shown) as discussed in the general description above. The potentiometric encoder 18 provides a quantitative respectively continuous output member position signal omps to the control unit 13. The output member position signal omps may be used by the control unit 13 for monitoring and supervision purposes and / or may provide the reference value to which the output member position variable is set in a synchronization routine.

[0197] In the shown design, the actuator 1 further includes two position detectors that are exemplarily realized as position switches 19.1 , 19.2 and are in this case configured to determine if the output member 12 assumes a respective associated output member position and provide a corresponding binary first position switch signal pss.1 respectively a second position switch signal pss.2 to the control unit 13. The corresponding output member positions are determined by the arrangement of the position switches 19.1 , 19.2. Both position switches 19.1 , 19.2 may be adjustable as first respectively second setting range end position switch that define, in combination, a setting range for the movement of the output member 12, with the setting range being smaller than a mechanically possible movement range. The latter may be defined by mechanical stops or otherwise by the actuator design and be, e.g., 90°. Alternatively, the design of the actuator 1 allows in principle continuous movement of the output member 12 over a number more than one, e.g. ten, revolutions or an infinite number of revolutions. Also in this case, a setting range may be defined via position switches 19.1 , 19.2.

[0198] Either of the position switches 19.1 or 19.2 may at the same time serve as reference position switch for setting the output member position variable ompv in the synchronization routine. In this case, the reference output member position corresponds to either of the setting range end positions. Alternatively, the reference output member position may be provided by the potentiometric encoder 18 respectively via the output member position signal 18 as mentioned before. In this case, the position switches 19.1 , 19.2 may solely be used for adjusting the setting range, without either of them being directly linked to the reference output member position.

[0199] In a further variant, the position switches 19.1 , 19.2 are not adjustable for setting a setting range, but are fixed by design and switch at positions that are generally at or close to the opposed ends of the mechanical movement range.

[0200] In a further variant, the position switches 19.1 , 19.2 are not present. Optionally, a first and second mechanical stop 19.11 , ,19.22, for example adjustable mechanical stops as setting range end position stops may be provided. In such embodiment, the control unit 13 is configured to determine if the out member hits a corresponding mechanical stop via the torque and / or the phase currents. Either of the first mechanical stop 19.11 and the second mechanical stop 19.22 may define the reference output member position. In a further variant, the setting range is defined by either of the first position switch 19.1 or second position switch 19.2, respectively as first respectively second setting range end position switch, while the opposed end of the setting range is defined by the second mechanical stop 19.22 or the first mechanical stop 19.11 as second respectively first setting range end position stop.

[0201] If at least one of the setting range end positions is defined by a by a position switch 19.1 , 19.2 respectively a mechanical stop 19.11 , 19.22, the actuator may automatically detect the respective setting range end position and the setting range in an adaption routine as discussed above in the general description.

[0202] In a further variant, only a single position switch, e.g. the first position switch 19.1 , is provided as reference position switch. Such reference position switch may be provided at an end of the mechanical movement range, which, however, is not essential.

[0203] In a further variant, the mechanical stops 19.11 , 19.22 and / or position switches 19.1 , 19.2 are not foreseen as integral parts of the actuator 1. Instead, they may be directly arranged at a load that is coupled to the output member 12. For this purpose, control unit 13 may optionally have corresponding position detector terminals (see also Figure 4 below) for connecting external position detectors, e.g. external position switches. Relying on position detectors respectively mechanical stops at the load is in particular favorable e.g. in the context of globe valves or in other application where more than one revolution of the output member 12 may be required for covering the full movement range of the load.

[0204] It is noted that the potentiometric encoder 18 may in principle be omitted if the reference output member position is defined via a mechanical stop or position detector, e.g. position switch. It is noted that different embodiments respectively configurations of the actuator 1 , in particular regarding the presence of the potentiometric encoder 18, the position switches 19.1 , 19.2 and the mechanical stops 19.11 , 19.22 may be realized in variants with one and the same overall design of the actuator 1 and in particular its control unit 13. The control unit 13 may be configured to receive corresponding configuration information by way of programming, e.g., via a wired or wireless communication interface. In a further embodiment, the control unit 13 is configured to automatically detect the presence of the position switches 19.1 , 19.2 as well as the potentiometric encoder 18, respectively be configured to detect whether and which of such elements are connected to the control unit and execute a corresponding self-configuration.

[0205] In the shown embodiment, the clutch 17 further includes an engagement detector that is exemplary realized as engagement switch 17.3 that may be a dedicated switch or be realized by contacts, e.g., on a printed circuit board of the control unit 13. The engagement switch 17.3 provides a binary engagement switch signal ess in dependence on whether the clutch 17 is in the engaging or non-engaging configuration, respectively. Favourably, the engagement switch 17.3 is open in the engaging configuration and closed in the non-engaging configuration.

[0206] Figure 4 illustrates further aspects of the actuator 1 according to Figure 3, and in particular of its control unit 13 in a schematic functional view, similar to Figure 3.

[0207] The control unit 13 includes a power circuit 13.1 for energizing the exemplarily three phases P1 , P2, P3 of the motor 15 in a controlled manner. The power circuit 13.1 is configured for energizing the phases P1 , P2, P3 for generating a current vector in a predetermined direction, in particular any pre-determined direction and may also energize the phases such that the resulting current vector is aligned with the magnetic flux and no torque is exerted on the rotor, as disused above in the general description. The power circuit 13.1 may in particular be configured for energizing the phases P1 , P2, P3 by way of pulse width modulation and be configured for energizing the phases P1 , P2, P3 in a sinusoidal manner. The control unit 13 may be optionally configured for Third Harmonic Injection (THI).

[0208] The control unit 13 further includes a back-EMF measurement unit 13.2 that is configured for measuring a back-EMF generated in each of the phases P1 , P2, P3. The back-EMF measurement unit 13.2 is in this embodiment configured for sampling the back-EMF generated in each phase P1 , P2, P3, thereby the value of the back-EMFs as a function of time.

[0209] The control unit 13 further includes a phase current measurement unit 13.3 that is configured for measuring the phase currents for each of the phases P1 , P2, P3. Favorably, the phase current measurement unit 13.3 has a common measurement shunt 13.3.1 (not individually shown in Figure 4, see Figure 14) via which the phase currents are measured sequentially.

[0210] Further functional units are in Figure 4 shown as commonly integrated in an overall control instance 13.4 of the control unit 13 for exemplary purposes. It is noted that the representation of the individual units in Figure 4 as well as Figure 3 does not necessarily imply any particular physical design. Various units may be integrated with each other or distributed as appropriate.

[0211] The control unit 13, in particular the overall control instance 13.4, includes a motor control unit 13.5 which, in turn includes a position control unit 13.5.1 for controlling the motor 15 under position control, a speed control unit 13.5.2 for controlling the motor 15 under speed control, and a torque control unit 13.5.3 for controlling the motor 15 under torque control. Generally, the control modes are used alternatively and the control unit 13 may be configured for switching between them as needed, including during movement. Optionally, two or more of the position control unit 13.5.1 , the speed control unit 13.5.2 and the torque control unit 15.5.3 may be cascaded respectively arranged in series in the control flow, and / or may be nested. Further either of the control modes may serve as primary control mode and one or more further control modes may serve as safety limit control mode as discussed above in the general description.

[0212] The control unit 13, in particular the overall control instance 13.4, includes an electrical rotor position determination unit 13.6. The rotor position determination unit 13.6 includes an inductance-based rotor position determination unit 13.6.1 for executing an inductance-based rotor position determination routine as low speed rotor position determination routine. The inductance-based rotor position determination routine may, e.g., implement the INFORM method as discussed above in the general description. Further, the rotor position determination unit 13.6 includes a back-EMF based rotor position determination unit 13.6.2 for executing a back-EMF based rotor position determination routine as high speed rotor position determination routine. The inductance-based rotor position determination unit 13.6.1 in particular evaluates the phases currents of the phases P1 , P2, P3 as determined by the phase current measurement unit 13.3 and the back-EMF based rotor position determination unit 13.6.2 in particular evaluates back-EMF for the phases P1 , P2, P3 as measured by the back-EMF measurement unit 13.2. The inductance-based rotor position determination unit 13.6.1 is further configured for executing a stillstand rotor position determination routine for avoiding respectively avoiding the otherwise present 180°-ambiguity as discussed above in the general description.

[0213] The electrical rotor position as determined by either of the inductance-based rotor position determination 13.6.1 or back-EMF based rotor position determination unit 13.6.2 serves as basis for controlling the energization of the phases P1 , P2, P3 respectively control of the power circuit 13.1. Further, the electrical rotor position serves as a basis for continuously respectively regularly updating the output member position variable ompv that is stored in a register and represents the computed output member position. In case of a power disconnection or power breakdown, the control unit 13 is configured to store the current value of the output member position variable ompv in a non-volatile memory as discussed before and retrieve it afterwards.

[0214] Favorably, the control unit 13 includes a mathematical motor model, in particular an observer-based motor model (not individually references). The measured back-EMF values as determined by the back-EMF measurement unit 13.3 and the phase currents as determined by the phase current measurement unit are continuously fed into the mathematical motor model

[0215] The control unit 13 further stores in respective registers a first setting range end position variable sepv.1 and a second setting range end position variable sepv.2 that define a moving range for moving the output member 12 in a configurable setting range as discussed before.

[0216] The control unit 13 further stores a number of exemplarily three auxiliary output member position variables aux.1 , aux.2, aux.3 in respective registers and are configurable. It is noted that the number of three is merely exemplary. The control unit 13 is configured to continuously monitor if the output member position variable ompv corresponds to an auxiliary output member position variable aux1 , aux 2, aux3. For each auxiliary output member position a respective auxiliary signal x1 , x2, x3 is provided. In the shown configuration, a pair of two respective auxiliary physical output ports are provided for each of the auxiliary signals x1 , x2, x3 that are in each case binary and complementary, as discussed before in the general description. In the shown embodiment, the control unit 13 further includes an NFC communication interface 13.7 that is configured for data change, in particular for configuration and diagnosis purposes, e.g., with a remote device such as an external handheld device and as discussed before in the general description. The NFC communication interface 13.7 is favorably designed to be powered wirelessly via the communication link with the remote device. In the shown design, the control unit 13 further includes a wired or wireless HVAC system control unit communication interface 13.8 for data exchange with, in particular receiving control commands from, an HVAC system control unit of an HVAC system.

[0217] Figure 5 schematically illustrates the variation of the inductance L in one of the phases in dependence of the electrical rotor position <pelectricforabrushless permanent-magnet (PM) motor exemplarily with a single pole pair for illustrative purposes. The four figures at bottom schematically show, from left to right, the rotor at an electrical rotor position ^electric of 0°=360°, 90°, 180°, 270°, with the south pole S in light grey and the north pole N transparent. The diagram at the top of Figure 5 illustrates the inductance L for one of the three phases, exemplary phase P1. It can be seen that the inductance L varies in a sinusoidal manner. For <pelectric= °° respectively <pelectric= 360° , as well as for ^electrical = 180°, th© inductance L is minimal (indicated with dashed circles), while it is maximal for <pelectric= 90° and <pelectric= 270° (indicated with dotted dashed circles). The inductance accordingly varies the double frequency respectively half period of the mechanical angle.

[0218] Figure 6, Figure 7 and Figure 8 illustrate alternative exemplary options for defining a setting range SR. In Figure 6, the opposed ends of the setting range SR are in each case defined by a respective mechanical stop 19.11 , 19.22 as setting range end position stops. Movement of the output member 12 is allowed between those stops. Either of the stops, for example the first mechanical stop, may also serve as reference position stop, thereby defining the respective end position as reference position. In an adaption movement, the output member 12 may be moved from one of the mechanical stops, for example the first mechanical stop and reference position stop 19.11 , to the second end position stop, thereby determining the movement range. It is noted that the mechanical stops 19.11 , 19.22 do not necessarily determine the movement range of the actuator 1. The latter may be larger or the mechanical end stops 19.11 , 19.22 may not be present and the actuator 1 may be designed for endless continuous movement as discussed above. Either or both of the mechanical stops 19.11 , 19.22 may be replaced by a respective position detector, for example position switch, as discussed before.

[0219] In Figure 7, the setting range SR is defined by a second soft setting range end position stop SEPS.2 by providing a settable angle in relation to the first mechanical stop 19.11 as a hard first setting range end position stop. The range between the second soft setting range end position stop SEPS.2 and the optionally present second mechanical stop 19.22 is not used and can be regarded as prohibited. It is noted that the second soft setting end position stop does not have a physical representation but is merely defined by a numeric value.

[0220] In Figure 8, the first setting range end position is defined by a first soft setting range end position stop SEPS.1 and the second setting range end position is defined by a second soft setting range end position stop SEPS.2. As mechanical reference for defining the soft setting range and position stops SEPS.1 , SEPS.2, an output member position sensor such as potentiometric encoder 18 (see Figure 3) may be foreseen. Detecting if either of the setting range end positions is assumed by the output member 12 in operation is done by checking the output member position variable ompv against the values for the soft setting range end positions SEPS.1 , SEPS.2 as stored in the setting range end position variables sepv.1 , sepv.2, as discussed above. Figure 9 and Figure 10 illustrate the design and operation of an exemplary embodiment of the optional clutch 17 (see also Figure 2), with Figure 9 showing the engaging configuration and Figure 10 showing the non-engaging configuration. The clutch 17 acts in this design between two toothed wheels of the reduction gear respectively gear unit 16, namely between the second gear part 16.2 as last toothed wheel in the power flow. The second gear part 16.2 can be rigidly coupled to or formed integrally with the output member 12. The in the power flow preceding gear part 16.x is arranged displaceable along an axis parallel to the rotational axis of the output member for switching between the engaging and the non-engaging configuration.

[0221] For switching the clutch 17 from the engaging into the non-engaging configuration, the actuation device 17.1 and the thereto coupled gear part 16.x are displaced (downwards in Figure 9, 10), such that gear parts 16.x and 16.2 are disengaged. The actuation part 17.1 , in turn, is operationally coupled with a lever 17.2 (see also Figures 11, 12), respectively a pushing part 17.2.2 thereof which exerts a pushing force onto the actuation device 17.1 upon the lever 17.2 being rotated around its rotational axis. The rotational axis of the lever 17.2 is transverse to the rotational axes of the gear parts and of the output member 12. A spring member 17.4 in form of a coil spring is foreseen that acts on the actuation device 17.1 and biases it towards the engaging configuration.

[0222] Further, the actuation device 17.1 acts on the engagement switch 17.3 which includes an electrical contact. In the engaging configuration of Figure 9, the engagement switch 17.3 is open, while it is closed in the non-engaging configuration of Figure 10.

[0223] Figures 11, 12 show the operating element 17.2.1 of lever 17. 2 in the engaging (Figure 11) respectively non-engaging (Figure 12) configuration. The operation element 17.2.1 is arranged at an outside of the housing (not referenced) of the actuator 1 and accessible for an operator. In the shown design, a depression respectively engaging recess 17.5 is arranged at the housing of the actuator 1 that releasably engages with a corresponding latch 17.2.11 of the operating element 17.2.1 in the non-engaging configuration of the clutch 17. The latch 17.2.11 is resilient and in the shown design an integral part of the operation element 17.2.1. A slit (not referenced) that separates the latch 17.2.11 from the rest of the operation part provides a required flexibility, in particular a required elasticity. In this way, the clutch 17 can be kept in the non-engaging configuration in a stable manner.

[0224] Figure 13 illustrates the application of test voltage vectors for impedance rotor position determination in an exemplary embodiment. The diagram illustrates a current i as measured over a common measurement shunt as a function of time t. For energizing the motor phases, pulse width modulation with a PWM period is used. In each PWM period, a torque control portion TCP is used for energizing the motor phases with pulse width modulation, and a subsequent measurement period MP of e.g. 30% is used for the measurement. It is noted the diagram only schematically illustrates the current in the measurement portion that results from applying a test voltage. This current is superimposed to the current resulting from the torque control portion. It is noted that that the phase currents continue to flow in the measurement portion.

[0225] In each measurement phase, a test voltage vector is applied in which a test voltage is applied to one of the exemplary three phases P1 , P2, P3. In the shown design, only a single test voltage vector is applied to each phase in the order P1 , P2, P3, P1 , P2, ... . A complete measurement accordingly requires three periods respectively measurement phases MP. In an alternative embodiment as mentioned in the general description before, test voltages of opposite polarity may be sequentially applied to each phase, for example in the order +P1 , -P1 , +P2, -P2, +P3, -P2, P1 , -P1 , +P2, ... . Figure 14 shows a simplified view of a control structure and especially the motor control structure of an actuator 1 in accordance with the present disclosure (see also Figure 4). Like in Figure 4, a position control unit 13.5.1 and a speed control unit 13.5.2 are present. Further, a torque control unit 13.5.3 and a current limiter 13.5.4 are foreseen. Generally, the position controller 13.5.1 , the speed controller 13.5.2, the torque controller 13.5.3 and the current limiter 13.5.4 are arranges in series respectively as cascade as generally known in the art. Further, an observer 13.9 is foreseen that provides an inertia-based mathematical / physical motor model. The observer 13.9 provides outputs for the rotor position the speed and the torque that serve as feedback signals for closed-loop control. Further, the observer 9 provides an output for computing the output member position variable ompv.

[0226] Figure 15 illustrates an example for a position tolerance range and a stability range when operating the actuator 1 under holding torque control as discussed in the general description above. It is noted that the angular ranges refer to the rotor of motor 15. The limits of the position tolerance range is indicated in solid bold lines and the limit of the narrower stability range in bold dashed lines. The ranges as such are indicated as corresponding double sided-arrows. TP indicates the rotor position for the target position of the output member and is, as explained before, centered in the position tolerance range. SP indicates the saved position which is, like the limits of the stability rage, modified respectively updated as the rotor moves. It is noted that in the depicted example the stability range is within respectively is a sub-range of the target position range. This, however, is not always the case as explained before. While the position tolerance range, is fixed, the stability range moves together with the rotor. Therefore, the stability range may temporarily only overlap with or be completely outside the position tolerance range.

[0227] Figure 16 illustrates an exemplary operational flow for operating an actuator 1 in a holding torque mode. Figure 16 is best understood with additional reference to Figure 15. In Step SO, the maximum holding torque is set to the maximum holding torque limit, typically the nominal torque of the motor. As a result, the motor moves the output member to a "stable position" where the output member position variable is within the position tolerance range. Step SO may include verifying that the output member has reached the stable position where the output member position variable is in the position tolerance range and optionally in the stability range centered with respect to the target position. The verification may require that the output member position variable has not left the position tolerance range and the stability range for a pre-determined time span.

[0228] In step S1 , the maximum holding torque is compared with the minimum holding torque limit. If the maximum holding torque equals or is below the minimum holding torque limit, the maximum holding torque is not modified. Otherwise, it is reduced. The comparison ensures that the maximum holding torque will subsequently not be reduced below the minimum holding torque limit.

[0229] In step S2, a countdown timer for measuring a pre-determined time span is started. Further, the current value of the output member position variable is stored as saved position and the stability range is set.

[0230] In step S3, it is tested whether the output member position variable is outside respectively has left the position tolerance range. If this is the case, the minimum holding torque limit is increased in Step S4 and the operational flow subsequently proceeds with step SO.

[0231] If it is determined in step S3 that the output member position variable is within the position tolerance range, the operational flow proceeds with step S5 where it is tested whether the output member position variable is outside respectively has left the stability range. If this is the case, the operational flow proceeds with step S2. If it is determined in step S5 that the output member position variable is within the stability range, the operational flow proceeds with step S6 where it is tested whether the predetermined time span has elapsed. If this is not the case and the timer is still running, the operational flow proceeds with step S3. Otherwise, the operational flow proceeds with step S1. As mentioned in the general description, the reduction of the maximum holding torque may follow a decreasing exponential functions for repeated executions of step S1.

[0232] REFERENCE SIGNS

[0233] I actuator

[0234] I I actuator-sided interface structure

[0235] 12 output member

[0236] 13 control unit

[0237] 13.1 power circuit

[0238] 13.2 back-EMF measurement unit

[0239] 13.3 phase current measurement unit

[0240] 13.3.1 common measurement shunt

[0241] 13.4 overall control instance

[0242] 13.5 motor control unit

[0243] 13.5.1 positon control unit

[0244] 13.5.2 speed control unit

[0245] 13.5.3 torque control unit

[0246] 13.5.4 current limiter

[0247] 13.6 electrical rotor position determination unit

[0248] 13.6.1 inductance-based rotor position determination unit

[0249] 13.6.2 back-EMF based rotor position determination unit

[0250] 13.7 NFC communication interface

[0251] 13.8 HVAC system control unit communication interface

[0252] 13.9 observer

[0253] 14 power supply unit

[0254] 141 power line terminal

[0255] 15 motor

[0256] 16 reduction gear (gear unit)

[0257] 16.1, 16.2, 16.x gear part

[0258] 17 clutch 17.1 actuation device

[0259] 17.2 lever (actuation element)

[0260] 17.2.1 operating element

[0261] 17.2.11 latch

[0262] 17.2.2 pushing part

[0263] 17.3 engagement switch

[0264] 17.4 spring member

[0265] 17.5 engaging recess

[0266] 18 potentiometric encoder (output member position sensor)

[0267] 19.1, 9.2 position switch (position detector)

[0268] 19.11 , 19.22 mechanical stop

[0269] 2 ball valve (fluid flow control device)

[0270] 2' damper (fluid flow control device)

[0271] 21 fluid flow control device-sided interface structure

[0272] 22 control shaft

[0273] 22' linkage assembly

[0274] 23 duct

[0275] 24 damper blade (fluid flow regulating member)

[0276] X coupling axis aux.1 , aux.2, aux.3 auxiliary output member position variable x1 , x2, x3 auxiliary signal ess engagement switch signal omps output member position signal ompv output member position variable pss.1 first position switch signal pss.2 second position switch signal sepv.1 first setting range end position variable sepv.2 second setting range end position variable L inductance

[0277] N magnetic north

[0278] S magnetic south

[0279] SR setting range SEPS.1 first soft setting range end position stop

[0280] SEPS.2 first soft setting range end position stop

[0281] SP saved position

[0282] TP target position

[0283] P1 , P2, P3 phases

Claims

CLAIMS1 . Actuator (1) for moving a load in an HVAC system, the load being a fluid flow regulating member, in particular a valve member of a valve (2) or a damper blade (24) of a damper (2'), the actuator (1) including: a motor (15), the motor being a brushless permanent-magnet motor having a permanent-magnet rotor and a stator with a at least two phases (P1 , P2, P3), a gear unit (16), wherein an input side of the gear unit (16) is coupled to the rotor and an output member (12) of the gear unit (16) is configured for coupling to the load, a control unit (13), the control unit (13) including a power circuit (13.1) for energizing the phases of the motor (1), the control unit (13) being configured for repeatedly executing the steps of: o determining, in a rotor position determination routine, an electrical rotor position at any rotational speed including standstill exclusively by way of measuring and computationally processing electrical variables of the power circuit (13.1) and / or the motor (15), o controlling the motor (15), in particular controlling energization of the phases, in dependence of the electric rotor position, thereby generating a stator field, o updating, based on the electrical rotor position, an output member position variable, the output member position variable representing a computed output member position, wherein the control unit (13) is further configured to control execution of a synchronization routine, the synchronization routine including setting the output member position variable to a reference value.

2. Actuator (1) according to claim 1 , wherein the control unit (13) is configured to control, based on the electrical angle, an output member position and / or a torque applied by the actuator (1) at stillstand.

3. Actuator (1) according to any of claim 1 to claim 2, wherein the control unit (13) is configured to control the actuator (1) in a number of alternative control modes, the control modes including in particular one or more of a position control mode, a torque control mode and a speed control mode, and to switch between control modes during operation, in particular during movement.

4. Actuator (1) according to claim 3, wherein the control unit (13) is configured to control the motor (15) to move the output member (12) into a mode switching position in position control mode and to switch, upon the computed output member position corresponding to the switching position, into speed control mode.

5. Actuator (1) according to any of claim 1 to claim 4, wherein the actuator (1) includes or is configured to operatively couple to an output member position sensor, in particular a potentiometric encoder (18), wherein the output member position sensor is configured to provide a quantitative output member position signal, the output member position signal representing an actual mechanical output member position.

6. Actuator (1) according to claim 5, wherein the control unit (13) is configured to monitor, in particular continuously or regularly monitor, a relation between the output member position variable and the output member position signal, and to trigger execution of the synchronization routine if the relation indicates the occurrence of an error condition, the error condition including in particular a deviation betweenthe computed output member position and the actual mechanical output member position.

7. Actuator (1) according any of claim 1 to claim 6, wherein the actuator (1) is configured to detect if the output member (12) assumes a mechanically pre-determined reference output member position, wherein the reference value represents the reference output member position.

8. Actuator (1) according to claim 7, wherein the actuator (1) includes or is configured to operatively couple to a reference position detector for detecting if the output member (12) assumes the reference output member position, wherein the reference position detector is in particular a reference position switch.

9. Actuator (1) according to claim 7 or claim 8, wherein the reference output member position is defined by a reference position stop (19.11).

10. Actuator (1) according to any of claim 7 to claim 9, wherein the synchronization routine includes controlling the motor (15) to move the output member (12) to assume the reference output member position.11 . Actuator (1) according to any of claim 1 to claim 10, wherein the actuator is configured to only move the output member in a setting range (SR), the setting range having a first and a second setting range end position.

12. Actuator (1) according to claim 11 , wherein the setting range (SR) is mapped in the control unit (13) to a setting value range, the setting value range having a minimum setting value corresponding to either of the first and second setting range end position, and a maximum setting value corresponding to the other of the firstand second setting range end position, wherein the minimum and maximum setting value are pre-determined independent from the first and second setting range end position.

13. Actuator (1) according to any of claim 11 or claim 12, wherein the first setting end position is defined by a first setting end position stop (19.11) or a first setting end position detector (19.1) and the second setting range end position is defined by a second setting end position stop (19.22) or a second setting end position detector (19.1), wherein the control unit (13) is configured to detect if the output member assumes either of the first setting range end position or the second setting range end position, wherein the actuator (1) is configured to execute an adaption routine, wherein the adaption routine includes moving the output member (12) between the first and second setting range end position and determining the setting range from the movement of the output member between the first and second setting range end position.

14. Actuator (1 ) according to claim 11 to claim 13, wherein either of the first or second setting range end position is the reference output member position.

15. Actuator (1) according to any of claim 1 to claim 14, the actuator (1) further including a clutch (17), the clutch (17) being arranged in a power flow from the motor (15) to the output member (12), in particular at a gear stage of the reduction gear (16), the clutch (17) being switchable between an engaging configuration and a non-engaging configuration, an engagement detector (17.3),wherein the control unit (13) is configured to trigger execution of the synchronization routine in response to the engagement detector (17.3) indicating a switching of the clutch (17) from the non-engaging configuration into the engaging configuration.

16. Actuator (1) according to any of claim 1 to claim 15, the actuator (1) being configured to be powered via an external power supply, the control unit (13) being further configured- to detect an interruption of the powering via the external power supply and to store, in response to the interruption, recovery data, the recovery data being indicative of the output member position variable and optionally the electrical rotor position, in a non-volatile memory, and- to detect a recovery of the powering via the external power supply and to read, in response to the recovery, the recovery data from the non-volatile memory.

17. Actuator (1) according to claim 16, the control unit (13) being further configured to trigger, in response to the recovery, the execution of the synchronization routine.

18. Actuator (1) according to any of claim 1 to claim 17, wherein the control unit (13) is configured to adapt the rotor position determination routine in dependence of a rotatory speed of the rotor.

19. Actuator (1) according to claim 18, wherein the rotor position determination routine includes a low speed rotor position determination routine and a high speed rotor position determination routine, wherein the control unit (13) is configured to switch between determining the electrical rotor position either according to the low speed rotor position determination routine or according to the high speed rotor position determination routine in dependence of the rotatory speed of the rotor.

20. Actuator (1) according to any of claims 1 to 19, wherein the rotor position determination routine includes an inductance-based rotor position determination routine, wherein the inductance-based rotor position determination routine includes applying a sequence of test voltage vectors to at least two phases, determining resulting test phase current changes and evaluating a relation between the test voltage vectors and the resulting test phase current changes, wherein the inductance-based rotor position determination routine is in particular the low speed rotor position determination routine.21 . Actuator (1) according to claim 20, wherein the actuator (1) is configured to execute a stillstand rotor position determination routine, wherein the stillstand rotor position determination routine includes, at rotor stillstand, executing the steps of carrying out the inductance-based rotor position determination routine, energizing the phases with a first operating point current vector, the first operating point current vector generating a first operating point stator field with magnetic saturation without resulting in a torque being exerted on the rotor, applying, while energizing the phases with the first operating point current vector, a first sequence of test voltage vectors to at least two phases and determining resulting first test phase current changes, energizing the phases with a second operating point current vector, the second operating point current vector generating a second operating point stator field with magnetic saturation, the second operating point current vector being collinear with the first operating point current vector, applying, while energizing the phases with the second operating point current vector, a second sequence of test voltage vectors to at least two phases and determining resulting second test phase current changes,evaluating a relation between the resulting first test phase current changes and second test phase current changes.

22. Actuator (1) according to claim 21 , wherein the first and second operating point current vector are in each case continuously built up over time.

23. Actuator (1) according to claim 21 or claim 22, wherein the first operating point current vector and the second operating point current vector have identical absolute values and opposite directions.

24. Actuator (1) according to any of claim 21 to claim 23, wherein applying the first sequence of test voltage vectors and the second series of test voltage vectors includes in each case applying a test voltage sequentially to at least two phases, in particular to each of the phases.

25. Actuator (1) according to any of claim 1 to claim 24, wherein the control unit (13) is configured to sequentially measure a respective phase current of at least two phases, in particular of each of the phases.

26. Actuator (1) according to claim 25, wherein the control unit (13) includes a common measurement shunt (13.3.1) for sequentially measuring the at least two phase currents, in particular the respective phase current of each of the phases.

27. Actuator (1) according to any of claim 1 to claim 26, wherein the rotor position determination routine includes a back-EMF-based rotor position determination routine, the back-EMF-based rotor position determination routine including processing at least one back-EMF generated in at least one phase, in particular in each of thephases, wherein the back-EMF-based rotor position determination routine is in particular the high speed rotor position determination routine.

28. Actuator (1) according to claim 27, wherein the back-EMF-based rotor position determination routine includes real-time sampling and processing a course of the back-EMF generated in at least one of the phases, in particular in each of the phases.

29. Actuator (1) according to any of claim 1 to claim 28, wherein the control unit (13) is configured to energize the phases (P1 , P2, P3) to generate torque on the rotor in a pre-determined direction.

30. Actuator (1) according to any of claim 1 to claim 29, wherein the control unit (13) is configured, upon the output member (12) or the load hitting a mechanical stop, to control the motor (15) to execute a release movement, with a moving direction of the release movement being opposite to the movement direction when hitting the mechanical stop.

31. Actuator (1) according to any of claims 1 to 30, wherein the control unit (13) is configured to control the motor (1), in particular to control energizing of the phases (P1 , P2, P3), to reduce the motor speed upon the computed output member position approaching a pre-determined mechanical stop position.

32. HVAC assembly, the HVAC assembly including an actuator according to any of claim 1 to claim 31 and a fluid flow control device, the fluid flow control device being in particular a valve (2) or damper (2'), wherein a fluid flow regulating member of the fluid flow control device is coupled to the output member (12) of the actuator.

33. HVAC system, the HVAC system including at least one HVAC assembly according to claim 32, the HVAC system further including an HVAC system control unit (13), the HVAC system control unit (13) being operatively coupled to the actuator (1) of the at least one HVAC assembly and being configured for controlling operating of the at least one actuator (1).

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