JP2024062719A - Motor control device - Google Patents

Abstract

In torque control of a motor, the process of determining torque loss for each operating state of each motor for torque compensation that suppresses the effects of variations in torque output characteristics due to differences in materials used in each motor is made as easy as possible.
[Solution] A control device for a motor M obtains a required torque to be output from the motor, obtains a loss torque determined for each operating state for a particular motor, obtains a torque correction value for each operating state determined by the motor constant of the motor and the torque generated for each operating state of the particular motor, corrects the required torque based on the loss torque and the torque correction value to determine a command value for the torque to be generated by the motor, and controls the operation of the motor to generate the torque of the command value.
[Selected Figure] Figure 1

Description

The present invention relates to a motor control device, and more specifically, to a device that controls the torque generated by a motor.

When motor constants such as the motor inductance and armature resistance are used in the control, the torque control accuracy and responsiveness of the motor are affected by the accuracy of the motor constants, so various configurations have been proposed to identify such motor constants. For example, Patent Document 1 proposes that in a control device that controls the operation of a synchronous motor by vector control, in order to identify the motor constants, the rotor is pulled into a specified position when the motor is stopped, current is applied appropriately to the d-axis and q-axis, and the parameters included in a model that follows the voltage equation of the system including the synchronous motor and the control device are sequentially estimated using voltage/current information and rotor position information, and the motor constants for the d-axis and q-axis are obtained from the estimated parameters.

Patent Publication 2008-182881

In general, the torque output from a motor is lower than the torque generated by the motor due to losses (loss torque) caused by iron loss, etc., so in torque control, in order to realize the torque (required torque) required of the motor from the drive system of the vehicle, etc., a torque value obtained by adding the loss torque as a compensation value to the required torque is given to the motor control device as a command value. In this regard, the loss torque varies depending on the operating state of the motor, i.e., the generated torque or winding current, rotation speed, input voltage to the inverter, etc., so it is experimentally determined for each operating state using these as variable parameters. However, even for motors with the same specifications, there is variation in the loss torque due to differences in materials, such as electromagnetic steel sheets and magnets, used in each motor. Therefore, in order to align the torque output characteristics of the motors, it is necessary to compensate the output torque using the loss torque for each operating state determined for each motor.

Since the torque loss of a motor depends on the motor constants (inductance, armature flux linkage, winding resistance, etc.) of each individual motor, if the torque loss for each operating state of a certain motor is known, it is possible to convert the torque loss for each operating state of other motors from the torque loss for each operating state of the certain motor using the motor constants of each motor. In this case, there is no need to experimentally investigate the torque loss for each operating state of all of the multiple motors, which is advantageous. This knowledge is utilized in the present invention.

Thus, the main objective of the present invention is to make the process of determining the loss torque for each operating state of an individual motor as easy or simple as possible for the purpose of compensating for the output torque in torque control of the motor.

According to the present invention, the above object is achieved by a motor control device including a required torque acquisition means for acquiring a required torque to be output from the motor, a loss torque acquisition means for acquiring a loss torque determined for each operating state of a motor, a torque correction value acquisition means for acquiring a torque correction value for each operating state determined by the motor constant of the motor and the torque generated for each operating state of the motor, a torque command value determination means for correcting the required torque based on the loss torque and the torque correction value to determine a command value for the torque to be generated by the motor, and an operation control means for controlling the operation of the motor to generate a torque of the command value.

In the above configuration, the "motor" may be any type of motor that is controlled to output the torque (required torque) required by the drive unit of the vehicle, and is typically, but not limited to, a permanent magnet synchronous motor that is operated and controlled by vector control using dq transformation. As described above, the "loss torque" is the torque component that is lost and not taken out as output from the total torque generated in the motor. As already described, the "operating state" here is the state value (operating state value) that is a parameter that determines the generated torque, such as the generated torque of the motor or the winding current, the rotation speed, and the input voltage to the inverter. The "one motor" is another motor (hereinafter referred to as the "reference motor") with the same specifications as the motor (hereinafter referred to as the "motor") whose operation is controlled by this control device, and may be any motor whose loss torque is determined by any method for each operating state, and may typically be a representative motor used for adapting a motor with a certain specification. The "motor constant" is a constant parameter that determines the torque characteristics for each motor with respect to the input current or voltage, specifically, inductance, armature flux linkage, winding resistance, etc. The "torque correction value" is a numerical value for converting the loss torque for each operating state of the reference motor into the loss torque for each operating state of the motor (this motor) controlled by this control device, and is typically calculated in advance for each operating state using the motor constant of this motor and the generated torque for each operating state of the reference motor, as described in detail later. The "torque command value" (torque command value) is a command value that represents the total torque to be generated in the motor, which is the sum of the required torque and the loss torque of this motor.

In the device of the present invention described above, the torque loss for each operating state, which varies due to differences in the materials used for each motor, is not experimentally investigated for each motor, but is obtained by converting the torque loss for each operating state obtained for a certain motor using the motor constants of each motor. With this configuration, it is only necessary to obtain the motor constants for each motor other than the certain motor, and it is expected that the effort, time, and cost required for adapting each motor will be significantly reduced.

In the above configuration, the loss torque may be prepared as a map with several operating state values as variables, and a value may be picked up from the map depending on the operating state at each moment. The torque correction value may also be prepared in advance as a map with the operating state values as variables, and a value may be picked up from the map depending on the operating state at each moment, or may be calculated depending on the operating state at each moment using a formula with the operating state values as variables. The torque correction value may be a constant that does not change depending on the operating state value. Specifically, the torque correction value for each operating state may be determined from the ratio or difference between the torque generated by the reference motor and the estimated value of the torque generated by the present motor obtained by calculation using the motor constant of the present motor for each operating state. The torque generated by the reference motor may be the torque actually measured for each operating state, or may be the estimated value of the generated torque obtained by calculation using the motor constant of the reference motor.

In the above configuration, the motor constants of each motor may be determined experimentally or theoretically by any method, for example, by using the method described below.

Previously, compensating for the variation in the torque output characteristics of each motor due to differences in materials, such as the magnetic steel sheets and magnets, required a huge amount of effort, time, and cost for adaptation, such as experimentally investigating the torque loss for each operating state of each motor. However, with the device of the present invention described above, the variation in the torque output characteristics of each motor due to differences in materials is compensated for by a relatively simple method using the motor constants of each motor, without the need for additional special equipment, and it is expected that the required torque can be output more reliably from the motor while saving the effort, time, and cost for adaptation.

Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

FIG. 1 is a block diagram showing the configuration of a motor control device according to this embodiment. Fig. 2(A) is a schematic diagram of a map of torque loss with the operation state values being variables (ai, bj, ck) used in the motor control device of this embodiment. Fig. 2(B) is a schematic diagram of a map of torque correction values with the operation state values being variables (ai, bj, ck) in a mode in which the torque correction values are given using a map in the motor control device of this embodiment. 3A and 3B are block diagrams showing another example of the configuration of the part that calculates the torque command value when the torque correction value is a constant in the motor control device of this embodiment. FIG. 4 is a flow chart illustrating one embodiment of a process for identifying the motor constants of a motor.

M...motor, INV...inverter, PS...power supply, Si...current sensor, Sv...voltage sensor, Sw...angle sensor (rotation speed sensor)

1, the configuration of the exemplary motor control device is for controlling the operation of a permanent magnet type synchronous motor by vector control in which the winding current is feedback-controlled using dq transformation so as to generate a torque of a command value, but the motor control device of this embodiment may be applied to any type of motor used in a vehicle drive device or the like and controlled to output a required torque (the power supply may or may not have a boost circuit). As shown in the figure, in the device of this embodiment, a torque command value obtained by adding a loss torque determined in advance for each operating state to the required torque required by the vehicle drive device or the like is basically calculated as the torque to be generated by the motor, and target values of d-axis and q-axis currents Id and Iq determined by a command conversion unit corresponding to the torque command value are used as input values for the FB control unit, and feedback control is performed via a voltage command unit and an inverter so that the actual d-axis and q-axis currents Id and Iq coincide with the target values. Here, as for the lost torque, typically, as shown in Fig. 2(A), a map is prepared in advance in which the operation state values of the motor, such as the torque command value or the actual torque value, or the winding current, the rotation speed, the voltage input to the inverter, etc., are used as variable parameters (ai, bj, ck), and in controlling the motor, the lost torque value corresponding to the set of the current operation state values detected by the sensors Si, Sv, Sw, etc. may be picked up from the map in which the operation state values at every moment are used as variables, and used as the command value (the rotation speed may be calculated from the detection value of the angle sensor, or may be estimated in the case of a sensorless motor). As a result, the torque generated by the motor is a value that corresponds to the torque command value, and the lost torque is lost when it is output from the motor, so that it is expected that a torque that corresponds to the required torque is obtained from the output shaft of the motor (the torque is negative during regeneration).

However, in actual motors, even if the specifications are the same, differences in the material properties used can cause variations in torque output characteristics, and if a loss torque determined for one motor is used to control another motor, it may not be possible to output the required torque. Therefore, in order to compensate for the torque with precision, it is necessary to use a loss torque that is suitable for each motor. In this regard, in the present embodiment, as shown in the figure, in the calculation of the torque command value, the loss torque determined for a certain motor is corrected using a torque correction value calculated so that it can be converted into a loss torque suitable for each motor, and the loss torque obtained is added to the required torque.

Specifically, in the device of this embodiment, the torque command value may be calculated by any one of the following equations.
[Torque command value] = [requested torque] + [loss torque] × [torque correction value] … (1)
[Torque command value] = [requested torque] + [loss torque] + [torque correction value] … (2)
Here, the "loss torque" is a loss torque determined, typically by experiment, for each operating state of a certain motor (reference motor), and the "torque correction value" is a numerical value calculated, typically for each operating state, using the motor constants of each motor so that the "loss torque" can be converted into a loss torque suited to each motor (this motor). With this configuration, a loss torque map for calculating the torque command value needs to be prepared only for the reference motor, and the loss torque suited to each motor is found by calculation using the torque correction value obtained using the motor constants, simplifying the experimental adaptation process for obtaining the loss torque.

In the above control device, the torque correction value for each motor may be prepared in the following several ways. In the first way, as shown in FIG. 2B, the torque correction value for each operating state is stored in the form of a map, similar to the loss torque of the reference motor, and in the control of the motor, the torque correction value corresponding to the set of operating state values at each moment may be picked up from the map and used in the calculation of the above formula (1) or (2). Note that maps of torque correction values for various motors may be stored in the device, and the map corresponding to the present motor may be selectively used. In addition, the torque correction value for an operating state value not recorded in the map may be obtained by interpolation or extrapolation from the map value. Furthermore, if it is desired to perform correction only when a specific torque is generated, for example, only when the maximum torque is generated, a significant value may be given to the map value in the state where a specific torque is generated, and all map values corresponding to the state where no correction is performed may be given a value of 1 or 0.

In the second aspect, when the torque correction value for each operating state is expressed by a formula with one or more operating state values as variables, the coefficients, orders, and constants of the variables in the formula are stored, and in the control of the motor, the torque correction value corresponding to the operating state at each moment is calculated from the operating state value at each moment using the formula, and may be used in the calculation of the above formula (1) or (2). The formula may be a polynomial, etc., or may be an equation obtained by machine learning. In addition, formulas for various motors may be stored in the device, and the formula corresponding to the present motor may be selectively used. Furthermore, the torque correction value may be obtained by interpolation or extrapolation.

As a third aspect, when the torque correction value is a fixed value that does not depend on the operating state, the fixed value may be stored and used in the calculation of the above formula (1) or (2). When the torque correction value is a fixed value, the torque correction value may be added to or multiplied by the required torque or the sum of the required torque and the lost torque, as shown in Figures 3(A) and (B).

Determination of Torque Correction Value The torque correction value of each motor is, as already mentioned, a numerical value calculated to convert the loss torque of the reference motor into a loss torque suited to each motor, and may be calculated by any method. Typically, the torque correction value of each motor may be calculated for each operating state based on the ratio or difference between the torque generated by the reference motor and the generated torque of each motor estimated by calculation using the motor constants and operating state values of each motor. Specifically, for example, when the motor is operated and controlled by vector control using dq transformation, the generated torque T of the motor is expressed as follows:
T = P _n φ _a I _q + P _n (L _d -L _q ) I _d I _q ... (3)
Here, _Pn , _φa , _Ld , _Lq , _Id , and _Iq are the number of pole pairs, armature flux linkage, d-axis inductance, q-axis inductance, d-axis current, and q-axis current, respectively, _Pn , _φa , _Ld , and _Lq are motor constants, and _Id and _Iq are operation state values. Therefore, in one aspect, for each operation state value, the generated torque Tra when the loss torque is examined is used for the reference motor, and for each motor, the generated torque estimate value Tee calculated by equation (3) using the motor constant of each motor is used to calculate the torque correction value:
Tee-Tra or Tee/Tra... (4)
In another embodiment, the generated torque Tra of the reference motor for each operating state value may be an estimated value calculated by equation (3) using the motor constant of the reference motor.

Determination of Motor Constants The motor constants of each motor used in the calculation of the torque correction value may be determined by any method. In this embodiment, for example, for a motor directly connected to the drive shaft of a vehicle such as an automobile and operated and controlled by vector control using dq transformation, the motor constants (armature interlinkage magnetic flux φ _a , d-axis inductance L _d , q-axis inductance L _q ) may be detected by the following method. Referring to FIG. 4, first, in the manufacturing process, the vehicle is run on a drum, and the torque of the motor is adjusted arbitrarily while the rotation speed is kept constant (steps 1 and 2). The torque can be adjusted by adjusting other power (engine or other motor). For example, when the motor is directly connected to the engine, an arbitrary torque load can be obtained by adjusting the engine load and the motor drive amount. In addition, when there is no other power or when the maximum torque cannot be realized, the torque is adjusted by changing the running resistance on the drum. The motor constants detected here change in value depending on the generated torque, so they may be detected for each torque. Then, while controlling the rotation speed ω and torque T to be constant, the d-axis and q-axis converted currents of the motor are set to Id = 0 and Iq = an arbitrary value to realize a state of an advance angle of 0 deg (step 3). Then, from the motor voltage equation, the armature interlinkage magnetic flux φ _a is first calculated by the following formula (step 4).
φ _a = (V _q -R _a ·I _q ) / ω ... (5)
Here, R _a is the winding resistance (which may be measured separately by any method), and V _q is the voltage applied to the q axis, which is determined by the voltage command unit in current feedback control. Next, the d-axis and q-axis converted currents are changed so as to balance with the torque T (step 5), and the d-axis inductance L _d and the q-axis inductance L _q are calculated from the motor voltage equation by the following equations (step 6).
_Lq = (R _a · I _d - V _d ) / ωI _q ... (6)
L _d = (V _q -R _a ·I _q -ωφ _a ) / ωI _d ... (7)
Here, _Vd is the voltage input to the d-axis, and is determined by the voltage command unit in the feedback control of the current. Next, when detecting the motor constant at a different torque, the torque is changed (step 8), and the above process is repeated. When the detection of the required range is completed, the process is terminated (step 7). The motor constant between the state points where the detection of the motor constant is executed may be calculated from an approximation function of _Ld and _Lq with Id and _Iq as variables. The approximation function may be obtained by machine learning to obtain _an approximation model, or a model may be created in advance and only the coefficients may be identified.

The above description is given in relation to an embodiment of the present invention, but many modifications and changes are easily possible for those skilled in the art, and it is clear that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims (1)

A motor control device, comprising:
a required torque acquisition means for acquiring a required torque to be output from the motor;
a torque loss acquisition means for acquiring a torque loss determined for each operating state of one motor;
a torque correction value acquisition means for acquiring a torque correction value for each operating state determined by a motor constant of the motor and a torque generated for each operating state of the one motor;
a torque command value determining means for determining a command value of a torque to be generated by the motor by correcting the required torque based on the lost torque and the torque correction value;
and an operation control means for controlling the operation of the motor so as to generate the torque of the command value.

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