Method for absorbing energy in an electric drive system, and electric drive system

Abstract

The invention relates to a method for absorbing energy in an electric drive system (1), in particular a drive system for operating an entry system or door system of a vehicle, the system comprising: an electric drive motor (M) for driving a drive body (2); and a motor control circuit (3) for controlling the drive of the drive motor (M). In said method: electric energy is supplied in a controlled manner to the drive motor (M) via the motor control circuit (3) in a driving operating mode and electric energy is absorbed by the drive motor (M) via the motor control circuit (3) in a braking operating mode; and optionally at least one part of the absorbed energy is converted into heat in a controlled manner by an ohmic resistor of the drive system (1) by injecting an alternating current into the drive system (1). The invention also relates to an electric drive system (1), in particular a drive system for operating an entry system or door system of a vehicle, which is controlled by means of such a method.

Description

[0001] Method for energy absorption in an electric drive system and electric drive system

[0002] The invention relates to a method for energy absorption in an electric drive system, in particular a drive system for an entry or door system of a vehicle, as well as such an electric drive system.

[0003] In such drive systems, which are used, for example—but not necessarily limited to—for entrance or door systems of road or rail vehicles, a drive element, e.g., a door leaf, ramp, step, and the like, is electrically moved by at least one electric motor. The door travel can be controlled using a cascaded controller structure, which may, for example, include a current controller, a speed controller, and a position controller.

[0004] In order to reach or maintain the speed specified by the position controller, the speed controller calculates a current setpoint, which is then implemented by the current controller. During an opening and closing process, the motor runs through all four operating quadrants I-IV, namely forward travel (I), forward braking (II), reverse travel (III), and reverse braking (IV), through the acceleration and deceleration phases that occur in both drive directions in what is known as four-quadrant operation (see Fig. 1). In drive mode, the electric machine acts as a motor, converting electrical energy into mechanical energy and assisting its movement. In braking mode, the electric machine acts as a generator, converting mechanical energy into electrical energy and thereby resisting the movement. The motor can basically operate in both forward and reverse directions (i.e., in drive and braking processes).

[0005] In the controller structure mentioned above, the output value of the current controller (i.e. through pulse pattern or duty cycle) acts on the control of a so-called motor bridge. In a typical design, the motor bridge, as shown in Fig. 2 as an example, consists of two half-bridges, the center point of which is each connected to a motor pole M1+, M1-, and an intermediate circuit capacitor CZK. When the motor is operating in quadrants I and III, the motor bridge supplies energy to the motor, while in quadrants II and IV the motor bridge must absorb energy from the motor. In many cases, it is not possible to feed the energy absorbed by the motor back into the upstream supply network. One reason for this could be a rectifier between the supply network and the motor bridge, which does not allow any reverse current to flow into the supply network.

[0006] In this case, the motor's energy consumption must be stopped as soon as the voltage in the DC link capacitor reaches the maximum permissible value. The absorption capacity of the DC link capacitor is limited by its capacitance and the maximum permissible voltage.

[0007] When designing a DC link capacitor for an electrically driven entrance or door system, the DC link capacitor must be able to absorb at least the energy stored as kinetic energy in the door system at maximum travel speed. The energy stored in the DC link capacitor during deceleration is fed back into the door system during the next acceleration, so that the DC link capacitor can absorb the next deceleration of the door system. With this design, the voltage of the DC link capacitor does not reach the maximum permissible voltage during normal operation on the plane.

[0008] However, such an interpretation does not cover the following special cases:

[0009] • Single-leaf door system with vehicle inclination (e.g. stop on a slope)

[0010] • Force caused by vandalism (e.g. person / passenger trying to accelerate door)

[0011] These two special cases require the motor bridge to absorb energy from the motor so that the speed controller can maintain the specified speed. For single-leaf door systems with a tilted vehicle, the required energy absorption capacity of the intermediate circuit capacitor can be determined or calculated and taken into account using simulation. In the event of a force applied by vandalism, the energy introduced into the door system depends on the force (vandalism by one or more people) and the duration of the impact. Due to space and cost constraints, it is not possible in most cases to design the intermediate circuit capacitor for vandalism.

[0012] To increase the energy absorption capacity of the intermediate circuit, it is common practice in industrial frequency converters to use braking resistors, which convert the regenerated energy into heat during braking operations of the electric motor. Additional braking resistors, including control and monitoring circuits, are associated with costs and installation space, which are incompatible with the requirements for door control units in vehicles (e.g., passenger transport).

[0013] In door control units, the voltage of the DC link capacitors is passively limited by voltage-limiting components (e.g., varistors, TVS diodes, etc.), or the energy consumption is stopped by switching off the motor bridge. Voltage-limiting components are subject to aging, and their energy consumption capacity must not be exceeded to protect the components (difficult design). Switching off the motor bridge leaves a slightly movable door system, which may move too quickly to the end position if further force is applied, resulting in mechanical damage.

[0014] Against this background, the invention is based on the object of providing a method for energy absorption in an electric drive system, for example, for operating a vehicle's entry or door system, as well as an electric drive system that ensures reliable, durable, efficient, and safe operation, for example, of the entry / door system. The method and the drive system should be structurally simple and cost-effective to implement.

[0015] This object is achieved by a method having the features of claim 1 and by an electric drive system having the features of claim 12. Further, particularly advantageous embodiments of the invention are disclosed in the respective subclaims. It should be noted that the features listed individually in the claims can be combined with one another in any technically reasonable manner (even across category boundaries, for example, between method and device) and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0016] It should further be noted that a conjunction "and / or" used herein between two features and linking them together is always to be interpreted such that in a first embodiment of the subject matter according to the invention only the first feature can be present, in a second embodiment only the second feature can be present, and in a third embodiment both the first and the second feature can be present.

[0017] Furthermore, the term "approximately" used herein is intended to indicate a tolerance range that a person skilled in the art in this field considers usual. In particular, the term "approximately" is to be understood as a tolerance range of the referenced size of up to a maximum of + / -20%, preferably up to a maximum of + / -10%.

[0018] In a method according to the invention for energy absorption in an electric drive system, in particular a drive system for operating an entry or door system of a vehicle (e.g., a land vehicle such as a road or rail vehicle, an aircraft, or a watercraft), wherein the drive system has an electric drive motor for driving a drive body (e.g., a door leaf, a ramp, or a step) and a motor control circuit for controlling the drive of the drive motor, electrical energy is supplied to the drive motor in a drive mode via the motor control circuit in a controlled manner, and electrical energy is absorbed by the drive motor via the motor control circuit in a braking mode. The method according to the invention provides that optionally at least part of the absorbed energy is controlled by an ohmic resistance of the drive system by impressing an alternating current into the drive system, i.e.is actively converted into heat through targeted action, but not through an inherent, passive process (herein also referred to as targeted or controlled energy conversion).

[0019] An inherent energy conversion process is understood to mean, in particular, the heat development of every ohmic resistor (e.g. conductor) through which current flows, which always occurs during operation of the drive system and is therefore unavoidable. However, this is not to be understood as energy conversion according to the invention. Instead, the invention discloses an energy conversion caused by the alternating current that is specifically (additionally) impressed into the drive system, which in itself essentially does not generate or is intended to generate any drive power in the drive motor. The optional execution of the controlled energy conversion, i.e. the controlled activation and deactivation, preferably takes place according to predetermined operating criteria and / or operating states of the drive system. Here and below, an alternating current is understood to mean an electric current whose direction changes cyclically or periodically.Accordingly, an alternating voltage is an electrical voltage whose polarity changes cyclically or periodically.

[0020] In principle, with the alternating current or alternating voltage, the duration of the two directions of the current or the two polarities of the voltage and, alternatively or additionally, the absolute value of the level of the two directions of the current or the two polarities of the voltage can be different. In other words, the alternating current or alternating voltage does not have to be symmetrical either in terms of time or level. However, according to a preferred embodiment, it is provided that with the alternating current, the temporal duration of an interval of a current flow in a first direction corresponds to the temporal duration of an interval of a current flow in a direction opposite to the first direction. The alternating current would therefore be temporally symmetrical.

[0021] A further preferred embodiment is characterized in that, in the alternating current, the absolute value of a current flow during an interval of current flow in a first direction corresponds to the absolute value of a current flow during an interval of current flow in a direction opposite to the first direction. Accordingly, the alternating current is then symmetrical in its absolute value. It should be noted that the above statements relate to the alternating and thus the impressed current, and not to the current as a whole. Despite a symmetry of the alternating current, the current as a whole may not exhibit this symmetry.

[0022] By selectively injecting the alternating current into the drive system, which includes at least the drive motor and the motor control circuit, the invention utilizes the electrical resistance already present in the drive system (e.g., the motor winding of the drive motor, electrical connection / connection lines, possible semiconductor switching elements of the motor control circuit, etc.) to convert electrical energy or electrical power into heat. In this way, the energy or power does not have to be absorbed or completely absorbed, for example, by an intermediate circuit capacitor of the motor control circuit. No further (additional) components are required for this, since existing components of the drive system are utilized.

[0023] In the event of a force applied by vandalism, for example, the energy introduced into the drive system or into an entry or door system driven by it depends on the force (vandalism by one or more people) and the duration of the impact. Targeted energy conversion in the ohmic resistors of the drive system makes it possible to reliably and safely withstand such cases of indeterminate force without a special, additional electrical design of the drive system, for example, an intermediate circuit capacitor in the engine control unit. The drive system or an entry or door system of a vehicle can thus be operated reliably, safely, durably, and efficiently.

[0024] It has been found that, for example, in a case of vandalism, a typical power input of around 100 W, or in a range of around 50 W to 150 W, can be expected. Since the power input due to vandalism can only occur during a predetermined, limited drive path of the drive unit, e.g., the movement of a powered entrance door, ramp, or step, the duration of the power input is limited in time by the duration of the drive unit's travel from one end position to another. Consequently, the total energy that can be input is also limited. Thermal overload of the drive system components can therefore be ruled out with appropriate component design. A power loss of around 100 W can be generated using an exemplary total ohmic resistance in the drive system of around 1 ohm with an applied current of around 10 A.The ohmic power loss P is determined in a known manner from the ohmic resistance R through which a current I flows.

[0025] P = R ■ I 2 .

[0026] In a particularly preferred development of the invention, the inherent ohmic resistance of at least one electrical component provided for functional operation of the drive system, in particular, for example, electrical power line(s), motor winding(s) of the drive motor, and / or semiconductor switching element(s) of the motor control circuit (e.g., semiconductor switch of a motor bridge), is used for the controlled conversion of energy into heat. Such an electrical component is generally understood to mean any electrical component of the drive system with an inherent ohmic resistance that is provided for implementing the actual drive control of the drive motor, so that a dedicated ohmic resistor, which would essentially only be provided for energy conversion, can be dispensed with, enabling a cost-effective and compact implementation.

[0027] A frequency and / or a current intensity can be determined for the alternating current. The frequency and / or current intensity of the alternating current to be impressed can be determined once, e.g., after manufacture and / or assembly of the drive system, and thus fixed (i.e., predetermined) before actual operation. Alternatively or additionally, the frequency and / or current intensity can also be determined during operation, i.e., in response to current operating conditions, and automatically adapted to these operating conditions (e.g., instantaneous mechanical resistance in the drive system, instantaneous force applied, for example, due to an inclined mounting of the drive system, due to human intervention, or similar). This allows the ohmic energy conversion to be controlled particularly efficiently and precisely.

[0028] According to a further advantageous embodiment of the invention, the frequency of the impressed alternating current is selected such that it is higher than a mechanical time constant of the drive system, for example by a factor of at least 10 higher, preferably up to a factor of 100. It is also possible for the frequency of the impressed alternating current to be higher by a factor of at least 100. The mechanical time constant represents, in a well-known manner, a measure of the mechanical reaction time of the drive system, for example the reaction time of a motor speed when the motor terminal voltage changes. This allows the desired alternating current to be impressed into the drive system for targeted energy conversion, but which has essentially no effect, or only a negligible effect, on the acceleration or deceleration of the driving body, e.g. an entrance door, ramp, step, or similar.In any case, the frequency of the impressed alternating current chosen in this way is not noticeable in the mechanical drive system.

[0029] Likewise in this sense, an advantageous development of the subject matter of the invention provides that the frequency and current intensity of the impressed alternating current are selected such that the time average of the impressed current is zero. In other words, the alternating current additionally impressed into the drive system has essentially no DC component. It is also possible for the alternating current to have the electrical energy delivered during an interval of a current flow in a first direction to correspond to the electrical energy delivered during an interval of a current flow in a direction opposite to the first direction. Consequently, the same amount of energy is then expended for both drive directions, resulting in a net energy consumption of zero for the movement. These variants can ensure that the alternating current has essentially no or very little DC component.has no noticeable negative impact on the acceleration and deceleration processes of the drive system. The acceleration and deceleration resulting from the applied alternating current cancel each other out.

[0030] According to yet another preferred embodiment of the invention, the drive motor is controlled by outputting a manipulated variable signal from at least one controller, wherein a ripple signal for impressing the alternating current is superimposed on the manipulated variable signal. In particular, the ripple signal is formed with a frequency corresponding to the current to be impressed and / or with an amplitude corresponding to the current to be impressed. This ultimately serves to generate the current to be impressed with a specific frequency and / or a specific current intensity and enables easy-to-implement intervention in, for example, a conventional controller structure for generating the alternating, preferably high-frequency, current in the drive system or drive motor.

[0031] The at least one controller can comprise a plurality of controllers, in particular a current controller, a speed controller, and / or a position controller, which can preferably be arranged in a functionally cascaded or nested manner. This means, for example, that the speed controller supplies the current controller with a current command variable as a manipulated variable signal depending on a feedback actual speed of the drive motor, and that the position controller supplies the speed controller with a speed command variable—again as a manipulated variable signal—depending on a feedback actual position of the drive motor or of the drive body driven by it. An actual current feeding the drive motor is preferably also fed back to the current controller.

[0032] It is fundamentally conceivable to use other regulator / control structures than those mentioned above and to impart the ripple signal to the drive system in a different way. For example, it is conceivable that a ripple signal is directly imprinted on a pulse-width modulated (PWM) signal for controlling the drive motor. For this purpose, the duty cycle of the PWM signal can be directly manipulated or changed to achieve the inventive effect of the ripple signal in the drive system.

[0033] For the most efficient and reliable operation of the drive system, according to a further development of the subject matter of the invention, at least a portion of the electrical energy absorbed by the drive motor via the motor control circuit can be stored in a rechargeable energy storage device, e.g., a capacitor. If the drive motor is controlled by a motor bridge, which can, for example, comprise two half-bridges, the energy storage device can be a so-called intermediate circuit capacitor.

[0034] If the energy absorbed by the drive motor is temporarily stored in an energy storage device, according to a further preferred embodiment, it can be withdrawn from the energy storage device to the drive motor in its drive mode and fed back to it in a controlled manner via the motor control circuit. In this way, the energy storage device can be completely emptied to provide maximum storage capacity for the next absorption. This further increases the operating efficiency of the drive system.

[0035] Preferably, the electrical energy absorbed by the drive motor can first be supplied to the energy storage device until a first predetermined electrical and / or thermal threshold is exceeded, and only after the first threshold has been exceeded can the electrical energy absorbed by the drive motor be converted into heat in a controlled manner by injecting the alternating current into the drive system. The threshold can be, for example, a maximum / minimum storage capacity of the energy storage device, a maximum / minimum electrical supply voltage at the energy storage device, a maximum / minimum temperature of the energy storage device, and the like. In any case, the predetermined threshold can be selected with the aim of ensuring safe and reliable operation of the drive system at all times, in particular protecting electrical components of the drive system from overload and damage.For example, the energy storage device can first be fully charged before further energy absorbed by the drive system or drive motor is deliberately converted into heat in order to protect the energy storage device from overload / damage and at the same time increase the operating efficiency of the drive system.

[0036] According to yet another advantageous embodiment of the invention, the controlled conversion of the electrical energy absorbed by the drive motor into heat is terminated when a second predetermined electrical and / or thermal threshold is undershot, wherein the second threshold differs from the first threshold. In other words, the inventive definition of the first and second threshold values ​​creates a hysteresis for the activation and deactivation of the targeted energy conversion. Depending on the physical quantity to which the respective threshold value refers, e.g., storage capacity, supply voltage level, temperature, and the like, the second threshold value can be smaller in magnitude, e.g., as soon as a certain temperature of the energy storage device is (again) undershot or the supply voltage at the energy storage device (again) falls below a certain value.Preferably, after the controlled energy conversion has ended, energy absorbed by the drive motor is again stored in the energy storage device until the first threshold value is exceeded again.

[0037] According to a particularly preferred embodiment of the subject matter of the invention, the drive system is designed such that the total ohmic resistance available for the controlled conversion into heat has a value of 0.5 to 5 ohms in the drive system, preferably 1 ohm to 5 ohms, for example also approximately 1 ohm, 2 ohms, 3 ohms or 4 ohms as well as other intermediate values ​​between 0.5 and 5 ohms. It has surprisingly been found that such a total ohmic resistance ensures sufficient energy conversion for operating cases that require protection, such as vandalism, with an already low applied current of approximately 1 A. The method and the drive system can thus be implemented cost-effectively and in a space-saving manner.

[0038] In principle, the method according to the invention disclosed herein is generically applicable and can be used accordingly with all such drive systems which have a drive body driven by at least one drive motor, wherein the drive motor must receive or absorb electrical energy from the motor control circuit in certain operating phases (e.g. braking operations).

[0039] According to a further aspect of the invention, an electric drive system, in particular for operating an entry or door system of a vehicle (e.g., a land vehicle such as a road or rail vehicle, aircraft, or watercraft), comprises an electric drive motor for driving a drive body (e.g., a door leaf, a ramp, or a step) and a motor control circuit for controlling the drive of the drive motor. Electrical energy can be controllably supplied to the drive motor via the motor control circuit in a drive mode and electrical energy can be absorbed by the drive motor via the motor control circuit in a braking mode. According to the invention, a control unit is provided that is designed to carry out a method according to one of the embodiments disclosed herein in order to control the drive motor.It should be understood that with regard to drive system-related definitions of terms as well as the effects and advantages of drive system-related features, the disclosure of corresponding definitions, effects, and advantages of the method according to the invention is fully relied upon, and vice versa. Repetition of explanations of similar features, their effects, and advantages can thus be omitted in favor of a more concise description, without such omissions being interpreted as a limitation of any of the disclosed subject matter of the invention.

[0040] The motor control circuit of the drive system can be designed as a motor bridge, which can, for example, have two half bridges with several semiconductor switching elements.

[0041] According to a preferred development, the drive system comprises at least one controller for controlling the drive motor by outputting a manipulated variable signal, as well as a ripple generator configured to generate a ripple signal for impressing the alternating current, which ripple signal is superimposed on the manipulated variable signal. In the case of a plurality of controllers, these can, for example, be functionally cascaded or nested. Thus, a speed controller and a current controller can be designed and arranged such that the speed controller supplies the current controller with a current control variable to be controlled as a manipulated variable signal.

[0042] It should be noted again that, in principle, other controller / control structures than those described above can also be provided, so that the ripple signal can also be applied to the drive system in other ways. For this purpose, the ripple signal can, for example, be applied directly to a pulse-width modulated (PWM) signal for controlling the drive motor, for example, by appropriately changing the PWM duty cycle.

[0043] Particularly preferably, the drive system has a total ohmic resistance available for the controlled conversion into heat with a value of approximately 0.5 to approximately 5 ohms, preferably approximately 1 ohm to approximately 5 ohms, whereby any intermediate values ​​between 0.5 and 5 ohms or 1 and 5 ohms are also intended to be included. According to a preferred development, the drive body of the drive system is a door leaf, a ramp, or a step of an entry system of a vehicle, e.g., a road or rail vehicle for public transport. In this case, the control unit can, for example, be a central part of the control of the door system, steps, and ramps.

[0044] Further features and advantages of the invention will become apparent from the following description of non-limiting embodiments of the invention, which are explained in more detail below with reference to the drawings. In this drawing, schematically show:

[0045] Fig. 1 four operating quadrants of an electric motor in four-quadrant operation,

[0046] Fig. 2 is a circuit diagram of an exemplary embodiment of a motor bridge according to the prior art and

[0047] Fig. 3 shows a block diagram of an embodiment of an electric drive system according to the invention, which is controlled by an embodiment of a method according to the invention.

[0048] In the different figures, parts that are equivalent in terms of their function are always provided with the same reference symbols, so that they are usually only described once.

[0049] Fig. 1 shows four operating quadrants I, II, III and IV to illustrate four-quadrant operation of a drive motor, where quadrant I represents a forward drive operation, quadrant II a forward braking operation, quadrant III a reverse drive operation and quadrant IV a reverse braking operation with the direction of rotation n shown (a positive value corresponds to clockwise) and the acting torque M (a positive value also corresponds to clockwise). In drive mode, the electric machine operates as a motor, converting electrical energy into mechanical energy and supporting its movement. In braking mode, the electric machine operates as a generator, converting mechanical energy into electrical energy and thereby opposing the positive drive movement. The four-quadrant operation scheme is well known, so further explanations will be omitted here.

[0050] Fig. 2 shows a circuit diagram of an exemplary embodiment of a motor bridge according to the prior art. In such a conventional embodiment, the motor bridge, as illustrated in Fig. 2, consists of two half-bridges, each with two semiconductor switches V1 and V2, or V3 and V4, with the centers of the respective half-bridges each connected to a motor pole M1+ or M1-. Furthermore, the motor bridge shown in Fig. 2 has an intermediate circuit capacitor CZK to store energy absorbed by the motor M (e.g., braking).

[0051] When the motor is operating in quadrants I and III, the motor bridge supplies power to the motor, while in quadrants II and IV, the motor bridge must absorb energy from the motor. In many cases, it is not possible to feed the energy absorbed by the motor back into the upstream supply network. This can be due, for example, to a rectifier between the supply network and the motor bridge, which prevents reverse current from flowing into the supply network.

[0052] Fig. 3 shows a block diagram of an embodiment of an electric drive system 1 according to the invention, which is controlled by an embodiment of a method according to the invention. The present drive system 1 serves, by way of example, to operate an entry or door system of a vehicle (neither shown), but is not necessarily limited thereto. The vehicle is preferably a road or rail vehicle, e.g., a bus or train. Other vehicles, such as aircraft and watercraft, are also conceivable.

[0053] In Fig. 3 it can be seen that the drive system 1 has an electric drive motor M for driving a drive body 2, for example an entrance door, step, ramp and the like. The motor M can, for example and without necessarily being limited to this, be a DC servomotor. The drive system 1 also has a motor control circuit 3 for controlling the drive motor M, which can, for example, be designed essentially in the manner of a motor bridge as shown in Fig. 2, but without necessarily being limited to this. The motor control circuit 3 can be controlled by a pulse-width modulated control signal (PWM signal) 5 in order to supply the drive motor 2 with a drive current and thus electrical drive energy in a drive mode in accordance with the PWM signal. The PWM signal 5 can be based on a motor control specification 4 (e.g. a value of a PWM duty cycle to be used orDuty Cycle) in a conventional manner, so it will not be discussed further here. In a braking mode, electrical energy can be absorbed from the drive motor M via the motor control circuit 3, as described in detail in the general part of this description.

[0054] The motor control specification 4 ultimately results to a significant extent from a target position 6' generated on the input side depending on a specific operating mode of the drive system (e.g. opening / closing of the door system), which is provided by a position specification unit 6.

[0055] Overall, the frame of the drive system 1, shown by way of example in dashed lines in Fig. 3, can be understood as a control unit 7. However, it should be understood that not all of the components shown in Fig. 3 necessarily have to be part of one and the same control unit 7, but can also be provided outside the frame shown in Fig. 3, e.g. the position specification unit 6. Likewise, the control unit 7 can have further components that are not shown in Fig. 3. The control unit 7 can essentially be formed by a computing and storage device, e.g. a microprocessor, microcontroller, etc., as well as memories in the form of, for example, RAM, ROM, flash, etc. In any case, the control unit 7 is designed to carry out a method according to the invention as disclosed herein in order to control the drive motor M.

[0056] In the embodiment illustrated in Fig. 3, the drive system 1 comprises, as controller 18, a current controller 8, a speed controller 9, and a position controller 10 for controlling the drive motor M, which in this case are assigned to the control unit 7. Current controller 8, speed controller 9, and position controller 10, which represent controller 18, are arranged in a functionally nested manner in the illustrated drive system 1, but are not necessarily limited to this.In other words, the speed controller 9 in this case supplies the current controller 8 with a current command variable as a manipulated variable signal 11 depending on a feedback actual speed 12 of the drive motor M, and the position controller 10 supplies the speed controller 9 with a speed command variable 13—which can also be understood as a manipulated variable signal 11—depending on a feedback actual position 14 of the drive motor M, which correlates with an actual position of the drive body 2. An actual current 15 transmitted to the motor M is fed back to the current controller 8. The motor control specification 4 can also be understood as a manipulated variable signal 11.

[0057] As can be further seen from Fig. 3, the drive system 1 has a ripple generator 16 for the controlled generation of a ripple signal 17 (e.g., essentially a square-wave signal) with a frequency and amplitude, shown schematically in Fig. 3. The ripple generator 16 can be selectively activated and deactivated via an activation signal EN in order to switch the generation of the ripple signal 17 on and off accordingly. Fig. 3 shows that the ripple signal 17 is superimposed on the manipulated variable signal 11 of the current command variable, so that the current controller 8 receives the superimposed ripple signal 17 in addition to the manipulated variable signal 11 output by the speed controller 9 as the current command variable, which describes the drive current to be supplied for the actual drive of the motor M.As a result, when the ripple signal 17 is activated, the current regulator 8 generates a drive current superimposed by an alternating current with a frequency and current intensity that depend on the selected frequency and amplitude of the ripple signal 17. In other words, an additional alternating current can be selectively injected into the drive system 1 or the drive motor M in a controlled manner.

[0058] It should be noted that the invention also includes other regulator / control structures than the one shown in Fig. 3, as the invention is not necessarily limited to the specific regulator / control structure of the control unit 7 shown in Fig. 3. Thus, the ripple signal 17 can also be impressed on the drive system 1 in other ways not shown here. For example, the ripple signal 17 can also be impressed on the motor control input 4, resulting in a modified PWM signal 5 for controlling the drive motor M.

[0059] The additionally impressed alternating current is used according to the invention to convert at least a part of the energy absorbed by the drive motor M into heat in a controlled manner by an ohmic resistance which is inherently provided by the drive system 1 in order to absorb the part of the absorbed energy.

[0060] The inherent ohmic resistance of the drive system 1 is formed by its electrical components, which are provided for functional operation of the drive system 1, in particular electrical power / connection line(s), motor winding(s) of the drive motor M and / or semiconductor switching element(s) of a motor bridge of the motor control circuit 3, as identified, for example, in Fig. 2 with the reference symbols V1-V4. An additional, dedicated ohmic resistance, which is used essentially solely for controlled energy conversion, is neither required nor provided in the drive system 1 according to the invention.

[0061] The drive system 1 according to the invention can be designed such that its total ohmic resistance available for the controlled conversion into heat has a value of 0.5 to 5 ohms, preferably 1 ohm to 5 ohms including all intermediate values ​​lying in the respective value ranges.

[0062] The frequency of the impressed alternating current is preferably selected such that it is higher (e.g., by a factor of 10 to 100 higher) than a mechanical time constant of the drive system 1, so that the additionally impressed alternating current is not noticeable in the mechanical drive system 1. The frequency of the alternating impressed current can be determined using the predetermined frequency of the generated ripple signal 17.

[0063] In particular, the frequency and current intensity of the impressed alternating current are preferably selected such that the time average of the alternating current is zero and thus has essentially no DC component.

[0064] The motor control circuit 3 of the exemplary drive system 1 shown in Fig. 3 can have a rechargeable energy storage device, similar to the intermediate circuit capacitor CZK shown in Fig. 2, in order to store at least a portion of the electrical energy absorbed by the drive motor M via the motor control circuit 3 in the energy storage device. In such a case, energy from the energy storage device can also be supplied to the drive motor M in its drive mode in a controlled manner via the motor control circuit 3.

[0065] Particularly preferably, the electrical energy absorbed by the drive motor M is first fed to the energy storage device until a first predetermined electrical and / or thermal threshold value is exceeded, and only after the first threshold value has been exceeded is the electrical energy still absorbed by the drive motor M converted into heat in a controlled manner by impressing the alternating current into the drive system 1 or the drive motor M.

[0066] If an optional second predetermined electrical and / or thermal threshold is undershot, the controlled conversion of the electrical energy absorbed by the drive motor M into heat can be terminated. To create a hysteresis, the second threshold may differ from the first threshold.

[0067] The method according to the invention disclosed herein for energy absorption in an electric drive system, in particular a drive system for operating an entry or door system of a vehicle, as well as the electric drive system according to the invention, are not limited to the specific embodiments described herein, but also include other embodiments with the same effect, which result from technically expedient further combinations of the features of all subject matter of the invention described herein. In particular, the features and combinations of features mentioned above in the general description and the description of the figures and / or shown alone in the figures can be used not only in the combinations explicitly specified herein, but also in other combinations or on their own, without departing from the scope of the present invention.

[0068] In a particularly preferred embodiment, the electric drive system according to the invention is used to operate an entry or door system in a vehicle (e.g., a land vehicle such as a road or rail vehicle, aircraft, or watercraft), wherein the drive system is controlled by a method disclosed herein for controlling such a drive system. The vehicle entry system preferably has a ramp and / or a step as the drive element, while the door system, for example, has a door leaf as the drive element.

[0069] List of reference symbols

[0070] 1 drive system

[0071] 2 drive bodies

[0072] 3 Motor control circuit

[0073] 4 Engine control specification

[0074] 5 PWM signal

[0075] 6 Position setting unit

[0076] 6' Target position

[0077] 7 Control unit

[0078] 8 current regulators

[0079] 9 speed controls

[0080] 10 position controllers

[0081] 11 Control variable signal

[0082] 12 Feedback actual speed

[0083] 13 Speed ​​command variable

[0084] 14 Feedback actual position

[0085] 15 Feedback actual current

[0086] 16 Ripple Generator

[0087] 17 Ripple Signal

[0088] 18 controllers

[0089] EN activation signal

[0090] GND Electrical reference potential / ground n Speed / rotational speed

[0091] M torque

[0092] M engine

[0093] M1+ Motor positive pole

[0094] Ml- Motor negative pole

[0095] Ub Electrical voltage

[0096] VI, V2 semiconductor switch first half bridge

[0097] V3, V4 semiconductor switch second half bridge

Claims

Claims: Method for energy absorption in an electric drive system (1), in particular a drive system for operating an entry or door system of a vehicle, comprising an electric drive motor (M) for driving a drive body (2) and a motor control circuit (3) for controlling the drive motor (M), wherein electrical energy is supplied to the drive motor (M) in a drive mode via the motor control circuit (3) and electrical energy is absorbed by the drive motor (M) in a braking mode via the motor control circuit (3), wherein optionally at least a part of the absorbed energy is converted into heat by means of an ohmic resistance of the drive system (1) by means of imprinting an alternating current into the drive system (1).A method according to claim 1, characterized in that an inherent ohmic resistance of at least one electrical component provided for the proper operation of the drive system (1), in particular electrical current line(s), motor winding(s) of the drive motor and / or semiconductor switching element(s) (V1-V4) of the motor control circuit, is used for the controlled conversion of energy into heat. A method according to any of the preceding claims, characterized in that a frequency and / or a current intensity is determined for the alternating current. A method according to the preceding claim, characterized in that the frequency of the impressed alternating current is selected such that it is higher than a mechanical time constant of the drive system. A method according to one of the two preceding claims, characterized in that the frequency and current of the applied alternating current are selected such that its time average is zero. A method according to one of the preceding claims, characterized in that the drive motor (M) is controlled by outputting a control signal (11) from at least one controller (18), wherein a ripple signal (17) for applying the alternating current is superimposed on the control signal (11). A method according to one of the preceding claims, characterized in that at least a portion of the electrical energy consumed by the drive motor (M) via the motor control circuit (3) is stored in a rechargeable energy storage device (CZK). A method according to the preceding claim, characterized in that energy is supplied to the drive motor (M) from the energy storage device via the motor control circuit (3) in a controlled manner during its drive operation.A method according to one of the two preceding claims, characterized in that the electrical energy absorbed by the drive motor (M) is first supplied to the energy storage device (CZK) until a first predetermined electrical and / or thermal threshold is exceeded, and only after exceeding the first threshold is the electrical energy still absorbed by the drive motor (M) converted into heat in a controlled manner by injecting the alternating current into the drive system (1). A method according to the preceding claim, characterized in that when a second predetermined electrical and / or thermal threshold is undershot, the controlled conversion of the energy absorbed by the drive motor is initiated. (M) absorbed electrical energy is converted into heat, wherein the second threshold differs from the first threshold. Method according to one of the preceding claims, characterized in that the drive system (1) is designed such that the total ohmic resistance available for the controlled conversion into heat in the drive system (1) has a value of 0.5 to 5 ohms, preferably 1 to 5 ohms.Electric drive system (1), in particular for operating an entry or door system of a vehicle, comprising an electric drive motor (M) for driving a drive element (2) and a motor control circuit (3) for controlling the drive motor (M), wherein electrical energy can be supplied to the drive motor (M) in a drive mode via the motor control circuit (3) and electrical energy can be received by the drive motor (M) in a braking mode via the motor control circuit (3), wherein a control unit (7) is provided which is configured to carry out a method according to one of the preceding claims in order to control the drive motor (M).Drive system according to the preceding claim, characterized in that the drive system (1) comprises at least one controller (18) for controlling the drive motor (M) by outputting a control signal (11) and a ripple generator (16) which is configured to generate a ripple signal (17) for imprinting the alternating current, which is superimposed on the control signal (11). Drive system according to one of the two preceding claims, characterized by a total ohmic resistance available for controlled conversion to heat with a value of 0.5 to 5 ohms, preferably 1 to 5 ohms. Drive system according to one of the three preceding claims, characterized in that. the driving element (2) is a door leaf, a ramp or a step.

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