Adaptive keep-alive for an electrically commutated electric motor
阅读说明：本技术 用于电整流的电动机的自适应的保持通电 (Adaptive keep-alive for an electrically commutated electric motor ) 是由 约尔格·哈茨池 于 2019-08-01 设计创作，主要内容包括：一种用于在具有至少两个绕组(A、B、S12、S23、S31)的电整流的电动机(10)的静止状态下产生保持力矩的方法,在静止状态下有时变化的负载力矩从外部作用到该电动机上,在该方法中,首先把具有最大值的保持电流馈入到第一绕组(A、B、S12、S23、S31)中。该保持电流连续地必要时减小至最小值。从这起,如果在电感的实际值与给定值之间的调控偏差超过了预定的阈值,调控电动机(10)的电感,确切地说,通过控制保持电流予以调控。由此可以自适应地调控保持电流,只要通过改变保持电流即使负载力矩变化也可以保持电动机(10)的静止状态。(A method for generating a holding torque in the stationary state of an electrically commutated electric motor (10) having at least two windings (A, B, S12, S23, S31), to which a sometimes varying load torque acts from the outside, in which method a holding current having a maximum value is initially fed into the first winding (A, B, S12, S23, S31). The holding current is continuously reduced to a minimum value if necessary. From this point on, the inductance of the electric motor (10) is controlled, to be precise by controlling the holding current, if a control deviation between the actual value of the inductance and the set value exceeds a predetermined threshold value. The holding current can thus be regulated adaptively, as long as the stationary state of the electric motor (10) can be maintained even if the load torque changes by changing the holding current.)
1. A method for generating a holding torque in the stationary state of an electrically commutated electric motor having at least two windings, to which a sometimes varying load torque acts from the outside in the stationary state, wherein, in the method,
a) feeding a holding current having a maximum value that can be set into a junction of the first winding;
b) determining a motor inductance parameter of the motor, wherein the magnitude of the motor inductance parameter forms an initial value, and the motor inductance parameter represents the inductance of the motor when the motor is electrified by using the maximum holding current in a static state;
c) by continuously reducing the holding current, the deviation of the magnitude of the motor inductance parameter relative to the initial value is tried to be larger than the set regulation deviation;
d) for the condition that the deviation of the motor inductance parameter is not generated, when the set minimum value of the holding current is reached, the holding current is reduced, then the magnitude of the motor inductance parameter is regulated to a value, and the difference between the value and the regulation output value generated when the regulation of the motor inductance parameter is started is not larger than the regulation deviation;
e) for the condition that the deviation value of the motor inductance parameter generated in the step c) is larger than the set regulation deviation, regulating and controlling the value of the motor inductance parameter to a value, wherein the difference between the value and the regulation output value generated at the beginning of regulation and control of the motor inductance parameter is not larger than the regulation and control deviation;
f) by adopting the regulation and control, the change of the inductance parameter of the motor, which is caused by the change of the load moment and has the changed magnitude larger than the regulation and control deviation, is compensated by changing the holding current, but the holding current is selected to be not smaller than the set minimum value and not larger than the set maximum value.
2. A method according to claim 1, wherein, as a motor inductance parameter, a recirculation time period is used in which the test current fed as a pulse into a winding other than the first winding drops from its feed to a settable minimum value.
3. The method according to claim 2, wherein the electric motor is controlled by means of a driver circuit with a driver final stage assigned to a winding connection of the electric motor; the drop in the test current fed as a pulse is determined by means of a discharge current detector assigned to the terminals of the following windings of the electric motor: a test current is fed into the winding as a pulse; and determining a recirculation period by means of the output signal of the discharge current detector.
4. The method of claim 3, wherein the discharge current detector generates an output signal when the value of the test current drops below a minimum value.
5. A method according to claim 3, wherein, when the motor is implemented as a unipolar stepper motor, in addition to the driver final stages common to unipolar stepper motors, a clamping circuit is employed for each driver final stage, which limits the voltage on the following winding connections to set values during the recirculation period: a test current has been fed as a pulse into the winding connection; and the discharge current detector signals the end of the voltage limitation, wherein the recirculation time period is determined thereby.
6. The method of claim 1, wherein the motor is controlled by a current chopping circuit having a current chopping compensator; feeding a holding current through a current chopping control of the joints of the first winding; feeding current into the joints of the first winding at the beginning of a clock cycle of current chopping control until the current rises to a set value and then falls until the end of the clock cycle; and from the beginning of the clock cycle to the time point when the current reaches the set value in the clock cycle, adopting the chopping time length as the inductance parameter of the motor.
7. A device for generating a holding torque in the stationary state of an electrically commutated electric motor having at least two windings, to which motor a sometimes varying load torque is applied from the outside in the stationary state, with:
-a holding current generating unit for feeding a holding current into a connection of a first winding of the electric motor;
-a motor inductance detection unit for detecting a motor inductance parameter representing a value of a motor inductance in a stationary state of the electric motor;
a controller for controlling the holding current in a stationary state of the electric motor in order to compensate for a sometimes changing load moment acting on the electric motor from the outside, wherein a difference between a motor inductance parameter setpoint value as a reference variable and a motor inductance parameter actual value as a feedback variable is supplied to the controller as a control deviation, wherein the motor inductance parameter actual value is a value generated on the basis of a magnitude of the holding current fed in the stationary state and a magnitude of the load moment acting on the electric motor, wherein the controller outputs a signal as a control parameter to the holding current generating unit;
a control unit for
-controlling the holding current generating unit in a stationary state of the electric motor so as to feed a maximum holding current;
-controlling a motor inductance detection unit intended to detect a motor inductance parameter when the electric motor is energized with a maximum holding current;
-switching between a first operating mode in which the holding current generating unit is controlled by the control unit and a second operating mode in which the holding current generating unit is controlled by the regulator,
-controlling the holding current generating unit for feeding a holding current which decreases continuously from a maximum holding current for inducing a regulation deviation at the input of the regulator which is larger than a settable threshold value, wherein this control of the holding current generating unit ends at the latest when the holding current decreases to a settable minimum current,
-activating a function of the regulator for switching the control of the holding current generating unit from the control unit to the regulator when the regulation deviation is larger than a threshold value during the continuous reduction of the holding current, in particular for regulating the motor inductance to the magnitude of the regulated output value of the motor inductance parameter generated at the activation of the function of the regulator.
8. The apparatus of claim 7, wherein there is a test current generating unit for generating a test pulse fed into another winding different from the first winding during a stationary state of the motor, wherein the motor inductance detecting unit detects a recirculation period generated by feeding the test pulse as a motor inductance parameter.
9. The device of claim 8, wherein there is a driver circuit with a driver final stage assigned to a winding connection of the motor and a discharge current detector assigned to a connection of the following windings of the motor: a test pulse can be fed into this winding, wherein the recirculation time period can be determined by means of the output signal of the discharge current detector.
10. The apparatus of claim 9, wherein the discharge current detector generates an output signal when the value of the test current drops below a settable minimum value.
11. The apparatus of claim 9, wherein, when the motor is implemented as a unipolar stepping motor, each driver final stage is provided with a clamping circuit for limiting the voltage to a set value on a winding of the motor into which a test pulse can be fed, wherein the discharge current detector outputs an output signal when decreasing below the set value.
12. The apparatus of claim 7, wherein the holding current generating unit has a current chopping circuit for current chopping control of the connection of the first winding; at the beginning of a clock cycle of current chopping control, current can be fed into the joints of the first winding until the current rises to a set value and then falls until the end of the clock cycle; from the start of the clock cycle until the point in time within the clock cycle when the current reaches the set value, the chopping duration is a motor inductance parameter that represents the motor inductance.
Technical Field
The invention relates to a method and a device for generating a holding torque in the stationary state of an electrically commutated electric motor having at least two windings, wherein a sometimes varying load torque acts on the electric motor from the outside in the stationary state, said load torque not exceeding a predetermined maximum value. In particular, the invention relates to the generation of a holding torque in the stationary state of a sensorless electric motor, in particular a sensorless stepping motor.
Background
The customer requests an electrically controlled drive (stellrantriebe) which, in addition to the torque during normal operation or travel operation, often also has a holding torque, up to which the control drive must remain stationary in the stationary state when a load torque is applied from the outside. In the case of electrically commutated motors with sensors for electrical commutation, such as potentiometers, Hall sensors, or in the case of expensive BLDC motor systems using special methods, such as "dimensional-Hall" (Virtu-Hall), there are solutions for the requirement for a holding torque which is static up to a set value. All the solutions currently on the market share the common feature that they are rather complicated and are therefore for commercial reasons less suitable for smaller, cost-effective adjustment drives.
The commutation of an electrically commutated electric motor is carried out without sensors, i.e. without sensors, for which the holding torque requirement is usually achieved by constant holding current in the stationary state of the actuator, whereby continuous electrical energy is required for maintaining the stationary state even if no or only a slight holding torque is mechanically required.
A method for reducing the holding current for maintaining the rotor position for an electrically commutated electric motor is known from US 2013/0193889 a 1. The method operates with hall sensors in order to identify changes in the rotor position to be maintained. Furthermore, a plurality of iteration steps are carried out in which the reduced holding current oscillates around its target value which is required to maintain the rotor position, which disadvantageously leads to noise and electromagnetic radiation.
DE 102009030884 a1 and US 2007/0252587 disclose the detection of the rotor position of an electrically commutated electric motor by means of the magnitude of the motor inductance and its changes.
Different control circuits for electrically commutated electric motors are described in WO 88/02952 a1, WO 2009/071267 a1 and US 4272714 a.
Disclosure of Invention
The aim of the invention is to improve the maintained energization of a sensorless, electrically commutated electric motor.
In order to achieve this object, the invention proposes a method and a device for generating a holding torque in the stationary state of an electrically commutated electric motor having at least two windings, on which motor a sometimes varying load torque is applied from the outside, which load torque does not exceed a set maximum value, wherein, in the method,
a) feeding a holding current having a maximum value into the connection of the first winding, which holding current compensates a set maximum load moment acting on the electric motor from the outside;
b) determining a motor inductance parameter, wherein the size of the motor inductance parameter forms an initial value, and the motor inductance parameter represents the inductance of the motor when the motor is electrified by using the maximum holding current in a static state;
c) by continuously reducing the holding current, the deviation of the magnitude of the motor inductance parameter relative to the initial value is tried to be larger than the set regulation deviation;
d) for the condition that the deviation of the motor inductance parameter is not generated, when the set minimum value of the holding current is reached, the holding current is reduced, then the magnitude of the motor inductance parameter is regulated to a value, and the difference between the value and the regulation output value generated when the regulation of the motor inductance parameter is started is not larger than the regulation deviation;
e) for the condition that the deviation value of the motor inductance parameter generated in the step c) is larger than the set regulation deviation, regulating and controlling the value of the motor inductance parameter to a value, wherein the difference between the value and the regulation output value generated at the beginning of regulation and control of the motor inductance parameter is not larger than the regulation and control deviation;
f) by adopting the regulation and control, the change of the inductance parameter of the motor, which is caused by the change of the load moment and has the changed magnitude larger than the regulation and control deviation, is compensated by changing the holding current, but the holding current is selected to be not smaller than the set minimum value and not larger than the set maximum value.
The invention therefore advantageously provides for an adaptive control of the holding current, which is required to maintain the standstill of the electrically commutated electric motor having at least two windings, wherein the method is applicable to a sensorless electrically commutated electric motor. In this case, at the beginning of the standstill of the electric motor, the maximum holding current is fed into the terminals of the first winding of the electric motor. The holding current is dimensioned such that it takes up the maximum load moment occurring as a result of the application, so that the motor remains stationary. Then, the holding current starts to be continuously reduced. During this phase, the magnitude or value of the parameter representing the motor inductance is determined. Because the motor inductance varies when the load torque applied to the machine causes the motor rotor position to change. This state is now intentionally induced by reducing the holding current. And ending the reduction of the holding current when the holding current reaches the set minimum value. If the motor rotor position has not changed until then, this indicates that the applied load torque is comparatively small or non-existent.
And switching to regulating and controlling the inductance parameter of the motor along with the minimum value of the holding current. From now on, as long as the change of the inductance parameter of the motor is larger than the set regulation deviation, the holding current is regulated and controlled, and the regulation deviation can be equal to zero or not. The magnitude of the motor current can then now be adapted and regulated to the level required for maintaining the current feed in order to keep the electric motor at a standstill as a function of the changing load torque.
According to the invention, the transition from the continuous reduction of the holding current to the holding current regulation takes place without iterative steps, i.e. without an intermediate connection of a two-point control device (Zwei-Punkt-Steuerung), in which case the actual value of the holding current oscillates around its target or set value. In particular, starting from the regulation according to the invention, a continuous regulation is carried out.
There are various examples of which values can be detected or determined in a stationary state of the motor in order to derive a parameter indicative of the inductance of the motor. It has been found to be advantageous for the motor inductance parameter to be determined by means of a recirculation period which is generated when the test current is fed into a further winding (which is different from the winding into which the holding current is fed) with the holding current energized. The test current feed is advantageously carried out in the form of test pulses.
In principle, the detection of the magnitude of the inductance of the motor can be carried out by means of a sensor, for example, an inductively operating sensor. However, it is clearly advantageous in this respect to operate sensorless, as will be described below with reference to various exemplary embodiments.
In a further advantageous embodiment of the invention, provision is therefore made in this respect for: the electric motor is controlled by means of a driver circuit with a final driver stage assigned to the winding connections of the electric motor; determining a drop in a test current fed as a pulse by means of a discharge current detector assigned to a connection of a winding of the electric motor, into which winding the test current is fed as a pulse; the recirculation time period is determined by the output signal of the discharge current detector, i.e. by the occurrence time of the output signal relative to the test pulse generation time.
In the aforementioned embodiment, the discharge current detector advantageously generates an output signal when the value of the test current or test pulse falls below a minimum value.
In a further advantageous embodiment of the invention, provision can be made for: when the electric motor is implemented as a unipolar stepper motor, in addition to the driver final stages that are common for unipolar stepper motors, a clamping circuit is used for each driver final stage, which limits the voltage at the following winding connections to a set value during the recirculation period: a test current has been fed as a pulse into the winding connection; the discharge current detector signals the end of the voltage limitation, whereby (i.e. with the aid of the time point) the recirculation time period is determined.
Finally, in a further embodiment of the invention, provision can be made for: the motor is controlled by a current chopping circuit with a current chopping compensator; feeding a holding current through current chopping control of a tap of the first winding; feeding current into a joint of a first winding at the beginning of a clock period controlled by current chopping until the current rises to a set value, and then descending until the end of the clock period; from the beginning of the clock cycle to the time point when the current reaches the set value in the clock cycle, the chopping time length is used as the inductance parameter of the motor.
In order to achieve the above object, the invention also provides a device for generating a holding torque in a stationary state of an electrically commutated electric motor having at least two windings, a sometimes varying load torque acting on the electric motor from the outside in the stationary state, the load torque not exceeding a set maximum value, comprising:
-a holding current generating unit for feeding a holding current into a connection of a first winding of the electric motor;
-a motor inductance detection unit for detecting a motor inductance parameter representing a value of a motor inductance in a stationary state of the electric motor;
a controller for controlling the holding current in the stationary state of the electric motor in order to compensate for a sometimes changing load moment acting on the electric motor from the outside, wherein a difference between a motor inductance parameter setpoint value as a reference variable and a motor inductance parameter actual value as a feedback variable is supplied to the controller as a control deviation, wherein the motor inductance parameter actual value is a value generated on the basis of the magnitude of the holding current fed in the stationary state and the magnitude of the load moment acting on the electric motor, wherein the controller outputs a signal as a control parameter to the holding current generating unit;
a control unit for
-controlling the holding current generating unit in the stationary state of the electric motor so as to feed a maximum holding current for compensating a maximum load moment that may be externally applied to the electric motor in the stationary state of the electric motor;
-controlling a motor inductance detection unit intended to detect a motor inductance parameter when the motor is energized with a maximum holding current;
switching between a first operating mode in which the holding current generating unit is controlled by the control unit and a second operating mode in which the holding current generating unit is controlled by the regulator,
controlling a holding current generating unit for feeding a holding current which decreases continuously from a maximum holding current for inducing a control deviation at the input of the regulator which is greater than a settable threshold value, wherein the control of the holding current generating device is ended at the latest when the holding current decreases to a settable minimum current,
the function of activating the regulator is used to switch the control of the holding current generating device from the control unit to the regulator when the regulating deviation is greater than a threshold value during the continuous reduction of the holding current, in particular to regulate the motor inductance to the magnitude of the regulated output value of the motor inductance parameter which is generated when the regulator function is activated.
Advantageously, the device of the invention employs a test current generating unit for generating a test pulse fed into a further winding different from the first winding during a stationary state of the electric motor, wherein the motor inductance detection unit detects a recirculation period generated by the fed test pulse as a motor inductance parameter.
In the aforementioned variant of the invention, a driver circuit can additionally be provided, with a driver final stage assigned to the winding connections of the electric motor and a discharge current detector assigned to the connections of the following windings of the electric motor: a test pulse can be fed into this winding, wherein the recirculation time period can be determined by means of the output signal of the discharge current detector.
In this case, it can be advantageous if the discharge current detector generates an output signal when the value of the test current falls below a minimum value.
In the case of the implementation of the electric motor as a unipolar stepping motor, it is advantageous if a clamping circuit for limiting the voltage to a set value is provided for each drive output stage on the winding of the electric motor, into which winding a test pulse can be fed, wherein the discharge current detector outputs an output signal when it falls below the set value.
In a further advantageous embodiment of the device according to the invention, it can be provided that the holding current generating unit has a current chopping circuit for current chopping control of the connections of the first winding; feeding current into a joint of a first winding at the beginning of a clock period controlled by current chopping until the current rises to a set value, and then descending until the end of the clock period; from the start of the clock cycle until the point in time within the clock cycle when the current reaches the set value, the chopping duration is a motor inductance parameter that represents the motor inductance.
According to the invention, when the sensorless, electrically commutated electric motor is designed, for example, as a bipolar stepping motor, one of the two windings is used to feed an adjustable holding current in the stationary state. Depending on the control scheme, this can be done by a current source, a chopper current generator or a PWM-generating mechanism. At a specific time, for example, a test current is modulated onto the second winding, to be precise, the following test pulses are preferably periodically modulated onto the second winding: the input energy of these test pulses is as low as possible, and the modulation thereof is selected so that as little or no mechanical and acoustic interference occurs. The electronic evaluation device then detects the decay behavior of the test pulse and thus its recirculation time.
This electronic evaluation device, together with the device for generating test pulses, in combination with the usual driver circuit, is considered to be an embodiment of the inventive device for carrying out the inventive method.
In tests it has been shown that the resulting measured value is almost independent of the magnitude of the holding current, but that the measured value is related to the load moment acting on the motor. This load moment causes a slight change in the mechanical position of the rotor, which is sometimes referred to as "drag loss" (or "phase angle").
Said slight variation of the mechanical position of the rotor has an influence on the motor inductance and thus on the measurement results of an electronic analysis device which detects the attenuation characteristics of the test pulses and thus their recirculation period.
A common procedure for carrying out the invention is, for example, to stop the electric motor first after an application-specific operation and to apply, as usual, a maximum holding current which ensures a specific holding torque in a specific maximum mechanical load state. According to the invention, the test pulse is then fed at the latest from this point in time, for example, into a further winding, which is different from the winding to which the holding current is fed.
The holding current is then continuously reduced and the analysis continues continuously as described above. In the case of a mechanical load moment applied to the electric machine, the measured values then begin to drift as the holding current decreases, as described above. If this is the case, according to the invention, a further reduction of the holding current is ignored as soon as the degree of drift exceeds a set threshold.
In a preferred embodiment, a control system is thus realized on the basis of which the holding current is controlled such that no loss of rotor position occurs and is reduced when the mechanical load torque decreases and is increased when the mechanical load torque increases.
For a unipolar stepping motor, the aforementioned method may be implemented in a physically identical manner.
Depending on the type of sensorless, electrically commutated electric motor, the invention can be implemented in a correspondingly adapted manner, wherein the above-mentioned independence of the measurement signal for determining the motor inductance and the magnitude of the holding current can be ensured.
With the invention, the constant current supply can be implemented adaptively even for inexpensive control drives with sensorless electronically commutated electric motors, as is currently possible only for systems with sensors or for systems with complex BLDC systems (which have a high and thus high computation power).
Drawings
The invention is described in detail below with the aid of a number of embodiments and with reference to the accompanying drawings. Here specifically:
FIG. 1 shows an example of wiring for a bipolar stepper motor with adaptive hold-on;
FIG. 2 illustrates exemplary characteristics of a bipolar motor with adaptive keep-alive;
FIG. 3 shows an example of a unipolar stepper motor with adaptive hold energization;
fig. 4 shows an example of a three-phase motor with adaptive keep-alive.
Detailed Description
As shown in fig. 1, the control of the
-an adjustable current source;
-an adjustable current sink;
-duty-cycle adjustable PWM-modulation; alternatively, the first and second electrodes may be,
-chopping current control with adjustable current threshold.
A test current is modulated onto the second winding, the input energy of the test current being as small as possible, the modulation of the test current being selected to present as little mechanical and acoustic interference as possible.
A common control for a bipolar stepper motor comprises
In order to remain energized, a
In the exemplary embodiment shown in fig. 1, the test
The
Some of the signal lines are shown in dashed lines in fig. 1. These signal lines are only needed when: the invention is also used in the opposite winding configuration with respect to the test pulse and the holding current, or the method is also applied to the respective second connection of the winding. When the method is applied to all windings, the finest adjustment accuracy of the maintenance of the holding position will be achieved.
Fig. 2 shows that the resulting measurement is almost independent of the magnitude of the holding current, but is related to the load torque acting on the motor.
Fig. 3 shows the present invention applied to a unipolar stepping motor. As long as the wiring parts shown in fig. 3 of the unipolar stepping motor are the same or functionally the same as the components shown in fig. 1, they are labeled with the same reference numerals as in fig. 1 in fig. 3.
In addition to the components of the individual
It also applies to fig. 3 that if the method is also used in the opposite winding configuration with respect to the test pulse and the holding current, the signal lines shown in dashed lines are required there. When the method is applied to all windings, the finest adjustment accuracy of the maintenance of the holding position will be achieved.
In fig. 4, a last exemplary embodiment of the application of the invention is shown, the electrically commutated electric motor being designed in this case as a three-phase stepping motor and without commutation sensors.
As long as the wiring components shown in fig. 4 of the unipolar stepping motor are identical or functionally identical to the components shown in fig. 1, they are labeled with the same reference numerals in fig. 4 as in fig. 1. Some signal lines are also shown in dashed lines in fig. 4, which means that they are needed when: the method is also used in the opposite winding configuration with respect to the test pulse and the holding current. When the method is applied to all windings, the finest adjustment accuracy of the maintenance of the holding position will be achieved.
Three embodiments have been described with reference to fig. 1-4, wherein the adaptive keep-alive related modules according to the invention are hatched respectively. Depending on the desired system performance, it may be sufficient to limit the analysis to one or more driver final stages. The finest adjustment accuracy of the holding position maintenance possible according to the invention is achieved when the method is applied to all windings and thus all final stages.
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