Parameter identification device, robot controller, and parameter identification method

Abstract

This invention provides a parameter identification device that can identify parameters used in field weakening control with higher accuracy. [Solution] The voltage prediction value calculator 12 calculates the voltage prediction value V' when the rotation speed command value ω_ref and torque command value τref of the motor 4 are changed and storage in the storage unit 14 is performed a predetermined number of times m. The parameter calculator 13 calculates the updated parameter x k+1 And the parameter x that was updated last time k The difference is calculated. The voltage prediction calculator 12 recalculates the voltage prediction value V' if the difference does not satisfy the termination condition of the iteration process, and the parameter calculator 13 identifies the parameter x if the difference satisfies the termination condition. out Confirm and output.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for identifying parameters used when controlling the field weakening of motors constituting the joint portion of a robot arm, and to a robot controller equipped with the apparatus. [Background technology]

[0002] Generally, when rotating a motor at high speed, field weakening control is performed to counteract the back electromotive force generated in the motor windings and apply a higher voltage. To perform field weakening control, parameters such as winding resistance, inductance, and back electromotive force constant are required. These parameters are either obtained using the motor's catalog values, or, if catalog values ​​are unavailable during the prototyping stage, measured using specialized equipment such as an LCR meter.

[0003] However, catalog parameters may include errors in modeling, individual differences, and power supply voltage errors. Furthermore, measuring them using specialized equipment such as LCR meters is cumbersome. For example, Patent Document 1 discloses a technique for identifying parameters for field weakening control based on motor rotation speed, current, and voltage commands. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-119473 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, there is a discrepancy between the voltage command value used for parameter identification in Patent Document 1 and the voltage value actually applied to the motor windings, and this discrepancy results in an error being present in the obtained parameters. The present invention has been made in view of the above circumstances, and its purpose is to provide a parameter identification device, a robot controller, and a parameter identification method that can identify parameters used for field weakening control with higher accuracy. [Means for solving the problem]

[0006] According to the parameter identification device described in claim 1, the D-axis current and Q-axis current from a robot controller that vector-controls a motor located at the joint of a robot arm via a drive circuit and performs field weakening control according to the motor's operating conditions, and the voltage sensor signal from a voltage sensor that detects the voltage output from the drive circuit are input.

[0007] The memory unit stores the combined voltage, D-axis current, Q-axis current, and motor rotation speed obtained when the motor is vector-controlled in response to the input motor rotation speed command and torque command. The prediction value calculation unit calculates a predicted voltage value obtained as a function with the motor winding resistance, inductance, and back electromotive force constant, as well as the D-axis current, Q-axis current, and rotation speed as elements. The parameter identification unit identifies the resistance, inductance, and back electromotive force constant as parameters based on the difference between the combined voltage and the predicted voltage value.

[0008] With this configuration, the output voltage of the drive circuit detected by the voltage sensor allows for highly accurate identification of the motor winding resistance, inductance, and back electromotive force constant—parameters used for field weakening control of the motor located at the joint of the robot arm—without the need to use voltage command values ​​or dedicated measuring instruments as in the conventional method.

[0009] According to the parameter identification device described in claim 2, when the storage to the storage unit is executed a specified number of times in response to the change in the rotation speed command and torque command of the motor, the prediction value calculation unit calculates a voltage prediction value. The parameter identification unit obtains the difference between the parameter updated this time and the parameter updated last time. If the difference does not satisfy the end condition of the iterative process, the prediction value calculation unit calculates the voltage prediction value again. When the difference satisfies the end condition of the iterative process, the parameter identification unit determines the updated parameter.

[0010] With this configuration, parameters can be identified in advance at a stage before the robot controller actually operates the robot arm. When operating the robot arm, field weakening control can be performed using the identified parameters.

[0011] The robot controller according to claim 3 includes a drive circuit, a voltage sensor, a current sensor signal output from a current sensor that detects each phase current output from each phase output terminal of the drive circuit, and the parameter identification device according to claim 1 or 2.

Brief Description of the Drawings

[0012] [Figure 1] First Embodiment, Functional Block Diagram Showing the Configuration of a Robot Controller and a Parameter Identification Device [Figure 2] In the robot controller, a functional block diagram mainly showing the part that performs vector control [Figure 3] Flowchart Showing the Processing Contents of the Parameter Identification Device [Figure 4] Second Embodiment, Functional Block Diagram Showing the Configuration of a Robot Controller Equipped with a Parameter Identification Device [Figure 5] Flowchart Showing the Processing Contents of the Parameter Identification Device [Figure 6] Diagram Showing Mathematical Formulas

Modes for Carrying Out the Invention

[0013] (First Embodiment) As shown in Figure 1, the robot system of this embodiment includes a robot controller 21 and a parameter identification device 22. Figure 2 is a functional block diagram showing the part of the robot controller 21 that performs vector control. The motor control unit 1 controls the inverter 2 by outputting three-phase voltage command values ​​Vu_ref, Vv_ref, and Vw_ref. Note that the inverted voltage command values ​​that control the negative switching elements are omitted. The inverter 2, which is the drive circuit, is configured by connecting semiconductor switching elements such as IGBTs and power MOSFETs in a three-phase bridge. Each phase output terminal of the inverter 2 is connected to one end of each phase winding of the motor 4. In this embodiment, the motors that are the target of drive control are the motors that make up each joint in a multi-joint robot arm, and motor 4 is one of them.

[0014] The motor control unit 1 includes a current command calculator 8, a DQ axis voltage command calculator 9, and a UVW voltage command calculator 10. A current detector 3 is placed between each phase output terminal of the inverter 2 and each phase winding of the motor 4. The current detector 3 detects the phase currents Iu, Iv, and Iw and outputs them to the DQ axis current calculator 5.

[0015] The position detector 6 is, for example, a rotary encoder, which detects the rotational position θ of the rotor of the motor 4 and outputs it to the DQ axis current calculator 5, the speed calculator 7, and the UVW voltage command calculator 10. The DQ axis current calculator 5 converts the three-phase currents Iu, Iv, and Iw into the D axis current Id and Q axis current Iq and outputs them to the DQ axis voltage command calculator 9. The speed calculator 7 calculates the rotational speed ω of the motor 4 from the rotational position θ and outputs it to the current command calculator 8 which constitutes the motor control unit 1.

[0016] In the motor control unit 1, the current command calculator 8 receives the torque command value τ_ref and the speed command value ω_ref as inputs. Based on each input, the current command calculator 8 generates the D-axis current command value Id_ref and the Q-axis current command value Iq_ref and outputs them to the DQ-axis voltage command calculator 9. The DQ-axis voltage command calculator 9 generates the D-axis voltage command value Vd_ref and the Q-axis voltage command value Vq_ref and outputs them to the UVW voltage command calculator 10. The UVW voltage command calculator 10 converts the input voltage commands into three-phase voltage command values ​​Vu_ref, Vv_ref, and Vw_ref and outputs them as PWM signals to the inverter 2. The above components, excluding the motor 4 and the position detector 6, constitute the robot controller 21.

[0017] Figure 1 is a block diagram showing the parameter identification device 22, primarily focusing on its function of identifying parameters used for field weakening control, and partially overlaps with Figure 2. The input terminal of the voltage detector 11, which is a voltage sensor, is connected to the output terminals of each phase of the inverter 2. The voltage detector 11 detects the line voltages Vuv, Vvw, and Vwu output from the inverter 2, calculates a combined voltage V based on these line voltages using equation (1) shown in Figure 6, and outputs it to the parameter calculator 13.

[0018] The voltage prediction calculator 12, which is the prediction value calculation unit, calculates the voltage prediction value V' based on the D-axis current Id, the Q-axis current Iq, and the rotation speed ω, and outputs it to the parameter calculator 13. The parameter calculator 13, which is the parameter identification unit, has a built-in memory unit 14. The parameter calculator 13 calculates the parameter group x_out used for field weakening control based on the combined voltage V, the D-axis current Id, the Q-axis current Iq, the voltage prediction value V', and the rotation speed ω, and outputs it to the current command calculator 8 of the motor control unit 1. The calculation of the voltage prediction value V' and the parameter group x_out will be described later.

[0019] In the above configuration, the voltage prediction calculator 12 and the parameter calculator 13 constitute the parameter identification device 22. Furthermore, the remaining components, excluding the motor 4, position detector 6, and voltage detector 11, constitute the robot controller 21.

[0020] Next, the operation of this embodiment will be described. The process shown in FIG. 3 assumes a case where parameters used for field-weakening control are identified in advance at a stage before actually operating the robot system. When an operator instructs the position of the tip of the robot arm via an operation terminal such as a teaching pendant, for example, the motor control unit 1 generates a speed command value ω_ref and a torque command value τ_ref according to the instructed position. In step S1, the motor 4 is operated according to these command values.

[0021] In step S2, the parameter calculator 13 causes the storage unit 14 to record the synthesized voltage V, D-axis current Id, Q-axis current Iq, and rotational speed ω associated with the above operation. Then, it is determined whether the number of recorded times has reached a specified number m or more (S3). If it is less than the specified number m (no), the operator instructs the next tip position. Along with this, the speed command value ω_ref and the torque command value τ_ref are changed (S8), and the process returns to step S1.

[0022] When the number of recorded times reaches a specified number m or more (S3; yes), the voltage predictor 12 calculates a voltage prediction value V' (S\(4\)). The calculation here is performed by the formula (2) shown in FIG. 6 as follows. The function f(x i , ek , a i ) in the right side of the formula (2) is the formula (3), and x k is the resistance value R of the winding of the motor 4, the inductance L k , and the back electromotive force constant K k which are parameters used for field-weakening control in advance shown in the formula (4). The initial value of k is "1". Also, a ek (i = 1, … m) is the D-axis current I i , Q-axis current I di , and rotational speed ω qi obtained in step S2 shown in the formula (5). i

[0023] In the subsequent step S\(5), the parameter x k is updated by the formula (6). J k on the right side of the formula (6) is the Jacobian shown in the formula (7), and the function G(xk ) is given by equation (8). In step S6, for example, the parameter x updated in step S5 is used. k+1 However, when using an iterative method such as Newton's method, the termination condition for the iteration process (|x k+1 -x k Determine whether the condition |<ε,ε≒0) is satisfied. If the termination condition is not met (no), increment k (S9) and return to step S4. If the termination condition is met (yes), the parameter calculator 13 sets the parameter x to the current update count k=n. out =x n Output (S7).

[0024] As described above, according to this embodiment, in the parameter identification device 22, the voltage prediction value calculator 12 calculates the voltage prediction value V' when the storage unit 14 is stored a predetermined number of times m in response to changes in the rotational speed command value ω_ref and torque command value τ_ref of the motor 4. The parameter calculator 13 then calculates the updated parameter x k+ The value 1 and the previously updated parameter x k The difference between this value and the value of is calculated. The voltage prediction calculator 12 recalculates the voltage prediction value V' if the difference does not satisfy the termination condition of the iteration process, and the parameter calculator 13 identifies the parameter x if the difference satisfies the termination condition. out Confirm and output.

[0025] With this configuration, the resistance R, inductance L, and back electromotive force constant Ke of the motor 4 windings, which are parameters used for field weakening control, can be identified with high accuracy based on the output voltage of the inverter 2 detected by the voltage detector 11, without using voltage command values ​​or dedicated measuring instruments as in the conventional method. Furthermore, parameters x can be identified in advance at a stage before actually operating the robot arm. out Since it is possible to identify the parameter x, when operating the robot arm, the identified parameter x out Field weakening control can be performed using this method.

[0026] Then, the parameter identification device 22 determines the parameter x based on the voltage V obtained by synthesizing the line voltages detected by the voltage detector 11. out Since it identifies the rotational position θ output by the position detector 6, the parameter x out It can be identified.

[0027] (Second Embodiment) In the following description, parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted, while the differences are described. As shown in Figure 4, the robot controller 31 of the second embodiment includes a motor control unit 32 that replaces the motor control unit 1. The motor control unit 32 incorporates a parameter identification device 22. For illustrative purposes, the storage unit 14 built into the parameter calculator 13 is omitted.

[0028] Next, the operation of the second embodiment will be described. In the second embodiment, it is assumed that the parameters used for field weakening control are identified when the robot system is actually in operation, that is, during actual machine operation. As shown in Figure 5, during actual machine operation, the combined voltage V, D-axis current Id, Q-axis current Iq, and rotational speed ω are recorded (S11), similar to step S2.

[0029] Then, when steps S4-S7 and S9 are executed, the parameter to be input to the current command calculator 8 is the parameter x output in step S7. out The data is updated (S12), and the process returns to step S11. In this case, as in the first embodiment, the parameter x is updated when the number of recordings reaches a specified number m or more. k Without completing the identification of parameter x, the robot system continues to operate. k This will continue to be updated.

[0030] The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or extensions are possible. Other iterative methods, such as the bisection method or the gradient method, can also be used. Instead of detecting line voltage, phase voltage can be detected. Alternatively, instead of detecting the phase current, a phase current or a line current may be detected. [Explanation of symbols]

[0031] In the drawing, 1 is the motor control unit, 2 is the inverter, 3 is the current detector, 4 is the motor, 5 is the DQ axis current calculator, 6 is the position detector, 7 is the speed calculator, 8 is the motor control unit, 9 is the DQ axis voltage command calculator, 10 is the UVW voltage command value calculator, 13 is the parameter calculator, 14 is the memory unit, 21 is the robot controller, 22 is the parameter identification device, 31 is the robot controller, and 32 is the motor control unit.

Claims

1. The D-axis current and Q-axis current are input from a robot controller that vector-controls the motors located at the joints of the robot arm via a drive circuit, and also performs field weakening control according to the operating conditions of the motors. The voltage sensor signal of a voltage sensor that detects the voltage output from the drive circuit, A storage unit that stores the combined voltage of the voltages, the D-axis current and the Q-axis current, and the rotation speed of the motor, which are acquired when the motor is vector-controlled in response to the input rotation speed command and torque command of the motor. A prediction value calculation unit calculates a voltage prediction value obtained by a function that takes the resistance, inductance, and back electromotive force constant of the motor winding, as well as the D-axis current, the Q-axis current, and the rotational speed as its elements. A parameter identification device comprising: a parameter identification unit that identifies the resistance value, the inductance, and the back electromotive force constant as parameters based on the difference between the combined voltage and the predicted voltage value.

2. The predicted value calculation unit calculates the voltage predicted value when the motor's rotation speed command and torque command are changed and storage in the storage unit is performed a predetermined number of times. The parameter identification unit calculates the difference between the parameter updated this time and the parameter updated last time. The predicted value calculation unit recalculates the voltage predicted value if the difference does not satisfy the termination condition for the iterative process. The parameter identification device according to claim 1, wherein the parameter identification unit determines the updated parameter when the difference satisfies the termination condition of the iterative process.

3. The aforementioned drive circuit, The voltage sensor and, A current sensor detects the phase current output from each phase output terminal of the aforementioned drive circuit. A robot controller comprising the parameter identification device according to claim 1 or 2.

4. A method for vector-controlling a motor located at the joint of a robot arm via a drive circuit, and for identifying parameters used when performing field weakening control according to the operating conditions of the motor, The D-axis current and Q-axis current generated in the aforementioned vector control, Based on the position sensor signal of the position sensor attached to the motor, The combined voltage of the voltages, the D-axis current, the Q-axis current, and the rotation speed of the motor are stored when the motor is vector-controlled in response to the input rotation speed command and torque command of the motor. The voltage prediction value is calculated using a function that takes the resistance, inductance, and back electromotive force constant of the motor winding, as well as the D-axis current, the Q-axis current, and the rotational speed as its elements. A parameter identification method for identifying the resistance value, inductance, and back electromotive force constant as parameters based on the difference between the combined voltage and the predicted voltage value.

5. When the memory operation is performed a specified number of times while changing the rotation speed command and torque command of the motor, the predicted voltage value is calculated. We will calculate the difference between the parameters updated this time and the parameters updated last time. If the difference does not satisfy the termination condition for the iteration process, the voltage prediction value is recalculated. The parameter identification method according to claim 4, wherein the identified parameter is determined when the difference satisfies the termination condition of the iterative process.

Images