Control of a rotary separator

Abstract

In a rotary separator for separating particles from a gas flow, having a rotationally driven separating element, having a BLDC motor for electrically driving the separating element in rotation, and having a set of control electronics that influences the rotational speed of the BLDC motor, the invention proposes that the motor is designed as a sensorless BLDC motor and therefore has no sensor for detecting the rotational angle position of the rotor, and that the set of control electronics is configured to switch automatically between open-loop control behavior and closed-loop control behavior such that, for starting up, the BLDC motor is supplied with a phase current at a fixed frequency in an open-loop control mode, and such that the BLDC motor is operated in a closed-loop control mode after a certain rotational speed has been reached.

Description

[0001] Control of a rotary separator

[0002] Description:

[0003] The invention relates to a rotary separator and a method for controlling a rotary separator.

[0004] The rotary separator is used to separate particles from a gas stream. The rotary separator features a rotary-driven separator element and a BLDC motor for electrically driving the separator element. The rotary separator also features control electronics that influence the speed of the BLDC motor.

[0005] DE 10 2022 105 879 A1 discloses a generic rotary separator, also known as a disc separator, which is used to separate liquid particles from hot gas. The separator rotor of the rotary separator has a plurality of separating discs. This disc separator uses a brushless direct current (BLDC) motor to drive the discs.

[0006] Other types of rotary separators or centrifuges, which are also electrically driven, are known from practice. BLDC motors, which feature a sensor for detecting the position of the BLDC motor's rotor, are commonly used for separators in commercial vehicles. These sensors—e.g., Hall sensors—enable reliable motor start-up and high dynamic performance because the target and actual state of the motor can always be compared. In particular, the circulating magnetic field is optimally matched to the current position of the rotor, namely its rotational angle, allowing the motor to be controlled optimally at all times.

[0007] It is also known that sensorless BLDC motors are used in practice for separators in cars. These motors offer advantages over BLDC motors with sensors in terms of cost and, due to the smaller number of components, also in terms of robustness. However, firstly, not every start-up attempt with a sensorless BLDC motor may be successful, and secondly, the dynamics are limited because in both cases the circulating magnetic field is not – or at best only randomly – optimally matched to the current position of the rotor.

[0008] The invention is based on the object of improving a generic rotary separator so that it is both inexpensive and robust, yet also offers reliable start-up behavior and high dynamics. Furthermore, the invention is based on the object of providing a method for controlling an electrically driven rotary separator that enables reliable start-up behavior and high dynamics of the rotary separator when using a sensorless BLDC motor.

[0009] This object is achieved by a rotary separator according to claim 1 and by a method according to claim 10. Advantageous embodiments are described in the subclaims. According to the invention, the motor is designed as a sensorless BLDC motor and thus free of a sensor that detects the rotational angle of the rotor. The control electronics are configured to automatically switch between a control mode and a regulation mode, such that, for start-up, a phase current with a fixed frequency is supplied to the BLDC motor in a controlled mode, and that after reaching a certain speed, the BLDC motor is operated in a regulated mode.

[0010] In other words, the invention proposes using a sensorless BLDC motor as the drive for a centrifuge, particularly in the form of a disc separator, so that the advantages of dispensing with a sensor come into play. To avoid the disadvantages of a sensorless BLDC motor as much as possible, the invention controls the BLDC motor using control electronics, which operate as a controller when the BLDC motor starts up and later, once the BLDC motor has reached a certain speed, automatically switches to act as a closed-loop control. In control mode, a phase current with a fixed, predetermined frequency is supplied to the BLDC motor.

[0011] The invention is based on the assumption that such a phase current will most likely be sufficiently well-matched to the motor position, that the motor will start, and that the motor speed can then be increased even without being able to determine the rotor speed. After reaching a certain speed, the motor can then be operated in a controlled mode.

[0012] Preferably, the control electronics are configured to detect electrical parameters of the BLDC motor and, based on these, automatically switch from the open-loop to the closed-loop mode. Even without a sensor, the motor's behavior can be determined with sufficient accuracy based on the electrical parameters of the BLDC motor, such as current consumption, inductances, or a counter voltage, so that the rotor position can be determined with good accuracy and the parameters of the supplied phase current can be changed in a closed-loop manner, thus achieving high dynamics in the operation of the motor and thus also of a rotationally driven separation element of the centrifuge, e.g., the multiple separator discs of a disc separator.

[0013] Since there is a risk of an unsuccessful start-up attempt when starting the motor, the control electronics are advantageously designed to automatically detect such an unsuccessful start-up attempt, for example based on the electrical parameters. In one embodiment, the control electronics are configured to brake the rotary-driven separation element after an unsuccessful start-up attempt in order to be able to initiate a new start-up attempt as quickly as possible. The braking is achieved with as little wear as possible and not through friction, but rather through a short-circuit in the windings of the BLDC motor or through a magnetic field counteracting the rotation. The control electronics are preferably configured to detect an unsuccessful start-up attempt of the BLDC motor, to brake the separation element by short-circuiting the windings after an unsuccessful start-up attempt, and to initiate a new start-up attempt of the BLDC motor.

[0014] As an alternative to such active motor braking, in another embodiment, the control electronics are also configured to detect an unsuccessful motor start-up attempt. However, this alternative assumes that the rotor of the BLDC motor is coasting down and its speed is decreasing. Therefore, after an unsuccessful start-up attempt has been detected, the control electronics automatically reduce the power supply to the BLDC motor for a specific time interval, e.g., by reducing the power supply to zero during this time interval. After the time interval has elapsed, the control electronics automatically initiate a new start-up attempt for the BLDC motor.Preferably, the control electronics are configured to detect an unsuccessful start-up attempt of the BLDC motor, reduce the power supply to the BLDC motor for a specific time interval after an unsuccessful start-up attempt, and initiate a new start-up attempt of the BLDC motor after the time interval has elapsed. Particularly preferably, the control electronics are configured to reduce the power supply to the BLDC motor to zero after an unsuccessful start-up attempt of the BLDC motor during the specific time interval.

[0015] In both alternative embodiments, in which the control electronics automatically initiate a new start-up attempt of the BLDC motor after a detected unsuccessful start-up attempt, the control electronics are preferably configured to initiate a new start-up attempt after the BLDC motor has come to a standstill. The new start-up attempt can, for example, already occur when the rotor of the BLDC motor is still rotating at a low speed. In one embodiment, however, the control electronics are configured to initiate the new start-up attempt only after the BLDC motor has come to a standstill, e.g., by selecting a sufficiently long time interval in the second alternative mentioned.

[0016] The control electronics are preferably configured to supply a phase current with modified parameters to the BLDC motor in the controlled mode during the new start-up attempt. The renewed start-up attempt can be carried out using the same parameters of the phase current supplied to the motor as during the previous start-up attempt. In one embodiment, however, the control electronics are configured to initially supply a phase current with modified parameters to the BLDC motor during a new start-up attempt, namely in the controlled mode. For example, the evaluation circuit can be configured to initially perform not just one but several start-up attempts, always with the same parameters, and to change the parameters of the phase current supplied to the motor after a predetermined number of unsuccessful start-up attempts, in order to increase the probability of a successful start-up of the BLDC motor.

[0017] In order to record the number of unsuccessful start-up attempts, in one embodiment an error entry is automatically written to an electronic error memory after the first unsuccessful start-up attempt. If a start-up attempt is again unsuccessful, the entry in the error memory is automatically changed so that it represents the number of unsuccessful start-up attempts. For example, an additional entry can be written to the error memory so that the number of entries corresponds to the number of unsuccessful start-up attempts. Or the value of the entry can be changed, for example from “1” to “2” or similar, so that although there is only a single entry in the error memory, the value of this entry indicates the number of unsuccessful start-up attempts. Before a next start-up attempt, the error memory is automatically read out so that, if necessary, a further error message can be generated based on the number of unsuccessful start-up attempts determined from this.The next start-up attempt can be made automatically with modified parameters of the phase current supplied to the motor. After a successful start-up attempt, the error memory can preferably be reset automatically. Alternatively, the value of the error memory can be assigned to another date so that the respective number of failed starts is retained in a later error log. The control electronics are preferably implemented as part of a higher-level control unit. Particularly preferably, the control unit is designed as a control device and can be mounted / is mounted at a distance from the rotary separator. Further preferably, the control unit is also designed to control other functions beyond the rotary separator.The control electronics can be designed as an integral component of the rotary separator; alternatively, and preferably, it can be implemented in an external control unit, for example, in vehicles in one of the existing control units, e.g., the engine control unit. This not only advantageously reduces the manufacturing costs of the rotary separator, but also reduces the total number of components required in the vehicle, since the control unit is not only dedicated to the rotary separator but also controls other functions.

[0018] In one embodiment, the rotary separator is designed as a disc separator, wherein the separating element, which is in particular comprised by the disc separator, has a plurality of discs arranged on a common axis of rotation.

[0019] The method according to the invention serves to control a rotary separator electrically driven by a sensorless BLDC motor. This is, in particular, the rotary separator according to the invention. The features described above with reference to the rotary separator according to the invention are also to be understood as relating to the method described below.

[0020] According to the method, the BLDC motor is started in a controlled mode by supplying it with a phase current at a fixed frequency. Once the BLDC motor reaches a certain speed, it is operated in a regulated mode. Electrical parameters of the BLDC motor are recorded, and based on these parameters, the motor automatically switches from controlled to regulated mode.

[0021] Preferably, an unsuccessful start-up attempt of the BLDC motor is automatically detected based on the electrical parameters. Afterward, the separator is automatically decelerated. A new start-up attempt of the BLDC motor is then preferably initiated automatically. The separator is preferably decelerated by a short circuit in the BLDC motor's windings.

[0022] Preferably, an unsuccessful start-up attempt of the BLDC motor is automatically detected based on the electrical parameters, and after an unsuccessful start-up attempt, the power supply to the BLDC motor is automatically reduced for a specific time interval. After the time interval has elapsed, a new start-up attempt of the BLDC motor is automatically initiated. Particularly preferably, the power supply to the BLDC motor is reduced to zero during the specific time interval. A new start-up attempt is preferably initiated after the BLDC motor has come to a standstill.

[0023] During a new start-up attempt, in particular, a phase current with modified parameters is supplied to the BLDC motor in the controlled mode. In the event of a first unsuccessful start-up attempt, an error entry is preferably automatically written to an electronic error memory. In the event of a subsequent unsuccessful start-up attempt, either an additional error entry is automatically written to the error memory or a value of the error entry is changed such that the number of unsuccessful start-up attempts can be automatically read from the error memory. In the event of a successful start-up attempt, the error memory is particularly preferably automatically reset. Preferably, when a certain number of unsuccessful start-up attempts is reached, the phase current supplied to the BLDC motor is automatically varied during the next start-up attempt.

[0024] The invention, in particular the method according to the invention, is explained in more detail below using the purely schematic representation.

[0025] Fig. 1 shows in the form of a flow chart a method for controlling a rotary separator driven by a sensorless BLDC motor.

[0026] Fig. 1 shows, as a first step 1, the starting of the rotary separator. This first step can, for example, be a start signal transmitted to the control electronics of the rotary separator, e.g., when a vehicle's internal combustion engine is started.

[0027] Step 2 involves accelerating the rotor, either from a low speed or from standstill, to a higher speed. This occurs in a controlled mode, also known as "open-loop mode," in which a phase current with fixed parameters is supplied to the BLDC motor, which is intended to rotate the separator's separating element.

[0028] Variations of step 2 consist of either repeating step 2 with the same phase current parameters if a new start-up attempt is made after an unsuccessful start-up attempt, or automatically varying the phase current during a new start-up attempt, i.e. supplying the BLDC motor with modified parameters. Such a variation can, for example, occur automatically after the first unsuccessful start-up attempt, but may also only occur after a predetermined number of, for example, two or three unsuccessful start-up attempts. Step 3 of the process consists of automatically checking whether the rotor start-up attempt was successful, which can be determined based on the electrical parameters that are automatically monitored by the control electronics.If the query result is “Yes”, the control system automatically switches from the controlled mode to the regulated mode for operating the rotary separator, which is shown as step 4 in the drawing.

[0029] However, if the query result is “No”, in the illustrated embodiment of the method, a message about the termination of the start-up attempt is automatically transmitted to a control unit (“ECU” = electronic control unit) of the vehicle according to step 5.

[0030] In addition, according to a step 6, the rotor of the BLDC motor is braked, which can be carried out either as an active braking process by a winding short circuit or as a passive braking process by waiting for a predetermined time interval during which the rotor gradually "runs down", i.e. reduces its speed due to a lack of energy supply.

[0031] Step 7 consists of waiting for the so-called pre-positioning of the BLDC motor's rotor. This time interval can be fixed and always constant. Alternatively, the time interval can be determined dynamically, for example, in the case of passive braking, depending on other measured parameters that influence the rotor's rotational resistance, such as temperature.

[0032] Step 8 consists of a second automatic query, namely checking whether the conditions for a renewed rotor start attempt are met. This condition can be the expiration of the aforementioned time interval or an automatically detected rotational movement of the rotor, which can be detected, for example, using electrical parameters. If the answer to the query is "No," steps 6 and 7 are repeated, followed by the query according to step 8.

[0033] However, if the answer to the second query is "yes," an entry is automatically written to an error log according to step 9. This creates an error counter so that the entry in the error log indicates the number of unsuccessful startup attempts. For example, a numerical value can be incremented by "1" starting from "0."

[0034] A subsequent step 10 consists of a third automatic query, namely whether the value in the error log—and thus the number of unsuccessful start-up attempts—has reached or exceeded a predetermined limit. If the answer to this query is "no," the process is repeated from the beginning, beginning with step 1. Depending on the number of unsuccessful start-up attempts, the parameters of the phase current supplied to the motor when the separator starts in controlled mode can be varied, as explained above for step 2.

[0035] However, if the answer to the query is "yes," meaning the number of unsuccessful start-up attempts has reached or exceeded a predetermined limit, a fourth automatic query is performed in step 11 to determine whether the boundary conditions for a start-up attempt are acceptable or not. These boundary conditions can, for example, be a specific temperature window or at least a minimum temperature, or values ​​for a minimum electrical voltage and / or a maximum electrical voltage as the supply voltage.

[0036] As explained above, the query in step 11 only occurs if, according to the query in step 10, the error counter has reached or exceeded a certain limit. If the query in step 11 determines that the boundary conditions for a start-up attempt are OK, then, in view of the large number of unsuccessful start-up attempts, an error message is automatically transmitted to the vehicle's control unit mentioned above in step 12, for example by writing an error entry to a corresponding error memory in the control unit. This error entry can, for example, lead to an automatic functional restriction of the vehicle, e.g. with regard to the maximum achievable vehicle speed or the maximum achievable engine speed of an internal combustion engine, or the error entry can lead to an automatically triggered alarm, e.g. a request to visit a workshop.

[0037] In an alternative embodiment, the query described as step 11 can also occur before each increment of the error memory, for example, before step 9. In this case, the increment of the error memory can also be made dependent on the query result, i.e., the entry in the error memory is only incremented if the boundary conditions are OK. In a further alternative, the query described as step 11 can occur before the separator starts - i.e., before step 1. The query described as step 11 can also be performed at multiple points in the process. As an alternative to the described embodiment, a separate memory can also be provided for the results of the queries.Regardless of the point in the process at which the query described as step 11 is carried out, the entry in the control unit's fault memory in step 12 is preferably triggered when a certain number of false starts have occurred under proper boundary conditions.

[0038] If the minimum temperature is not met or the temperature is outside the specified temperature window, and if the supply voltage is below the minimum voltage or above the maximum voltage, the query in step 11 is answered with "No" and the system automatically waits according to step 14 until the boundary conditions are OK. Then, in step 15, the error entry in the error memory is automatically reset, i.e. the corresponding error counter is set to "0", and a new start-up attempt is automatically started, beginning with step 1. The error counter can be saved in a data record before being reset, or alternatively, the error counter can be omitted and the current value can be assigned to another date, e.g. a time value.

[0039] Reference symbol:

[0040] Step Start

[0041] Step Pre-positioning

[0042] Step acceleration

[0043] Query successful

[0044] Step switching

[0045] Step Message Cancel

[0046] Step Deceleration

[0047] Query conditions

[0048] Step error memory

[0049] Query error memory

[0050] Query boundary conditions

[0051] Step Error Message

[0052] Step Wait

[0053] Step Reset error message

Claims

Claims: 1 . Rotary separator for separating particles from a gas stream, with a rotationally driven separation element, and with a BLDC motor for electrically rotating the separation element, and with control electronics influencing the speed of the BLDC motor, characterized in that the motor is designed as a sensorless BLDC motor and is thus free of a sensor detecting the rotational angle position of the rotor, and in that the control electronics are set up to automatically switch between a control behavior and a control behavior in such a way that a phase current with a fixed predetermined frequency is supplied to the BLDC motor in a controlled mode for starting up, and that after reaching a certain speed the BLDC motor is operated in a controlled mode.

2. Rotary separator according to claim 1, characterized in that the control electronics are designed to detect electrical parameters of the BLDC motor and to automatically switch from the controlled to the regulated mode based on these parameters.

3. Rotary separator according to claim 1 or 2, characterized in that the control electronics are designed to detect an unsuccessful start-up attempt of the BLDC motor, after an unsuccessful start-up attempt the separating element to slow down by short-circuiting the windings and to start a new start-up attempt of the BLDC motor.

4. Rotary separator according to claim 1 or 2, characterized in that the control electronics are configured to detect an unsuccessful start-up attempt of the BLDC motor, to reduce the energy supply to the BLDC motor for a specific time interval after an unsuccessful start-up attempt, and to start a new start-up attempt of the BLDC motor after the expiration of the time interval.

5. Rotary separator according to claim 4, characterized in that the control electronics are configured to reduce the energy supply to the BLDC motor to zero in the event of an unsuccessful start-up attempt of the BLDC motor during the specific time interval.

6. Rotary separator according to one of claims 3 to 5, characterized in that the control electronics are designed to initiate a new start-up attempt after the BLDC motor has come to a standstill.

7. Rotary separator according to one of claims 3 to 6, characterized in that the control electronics are configured to supply a phase current with modified parameters to the BLDC motor in the controlled mode during a new start-up attempt.

8. Rotary separator according to one of the preceding claims, characterized in that the control electronics are implemented as part of a higher-level control unit which is designed as a control device and can be mounted at a distance from the rotary separator and is also designed to control other functions beyond the rotary separator.

9. Rotary separator according to one of the preceding claims, characterized in that the rotary separator is designed as a disc separator, wherein the separating element has a plurality of discs arranged on a common axis of rotation.

10. A method for controlling a rotary separator electrically driven by a sensorless BLDC motor, in particular according to one of the preceding claims, comprising the following method steps: • To start the BLDC motor, it is operated in a controlled mode by supplying the BLDC motor with a phase current at a fixed frequency, • and after reaching a certain speed of the BLDC motor, it is operated in a controlled mode, • where electrical parameters of the BLDC motor are recorded and based on these, the system automatically switches from controlled to regulated mode. 11 . Method according to claim 10, characterized in that an unsuccessful start-up attempt of the BLDC motor is automatically is automatically recorded based on the electrical parameters, and that after an unsuccessful start-up attempt the separator is automatically braked and that a new start-up attempt of the BLDC motor is then automatically started.

12. Method according to claim 11, characterized in that the separating element is braked by a short circuit of the windings of the BLDC motor.

13. The method according to claim 10, 11 or 12, characterized in that an unsuccessful start-up attempt of the BLDC motor is automatically detected on the basis of the electrical parameters, and that after an unsuccessful start-up attempt, the energy supply to the BLDC motor is automatically reduced for a certain time interval, and after the expiry of the time interval, a new start-up attempt of the BLDC motor is automatically started.

14. The method according to claim 13, characterized in that during the specific time interval the power supply to the BLDC motor is reduced to zero.

15. Method according to one of claims 11 to 14, characterized in that a new start-up attempt is started after the BLDC motor has come to a standstill.

16. Method according to one of claims 11 to 15, characterized in that during a new start-up attempt, the BLDC motor in the controlled mode is supplied with a phase current with changed parameters.

17. Method according to one of claims 11 to 16, characterized in that in the event of a first unsuccessful start-up attempt, an error entry is automatically written into an electronic error memory, and in the event of a further unsuccessful start-up attempt, either an additional error entry is automatically written into the error memory or a value of the error entry is changed in such a way that the number of unsuccessful start-up attempts can be automatically read out from the error memory, and in the event of a successful start-up attempt, the error memory is automatically reset.

18. Method according to claim 17, characterized in that when a certain number of unsuccessful start-up attempts is reached, the phase current supplied to the BLDC motor is automatically varied during the next start-up attempt.

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