Motor control device, motor control method, motor module, and electric power steering device

Abstract

To provide a control device which can improve steering feeling an operator can feel.SOLUTION: A motor control device comprises a model following controller 230A which generates correction torque based on output of a control object that is a motor to correct input of the controlled object on the basis of the correction torque. The model following controller 230A includes: a high pass filter 233 having a first cut-off frequency; and a low pass filter 232 having a second cut-off frequency which is larger than the first cut-off frequency. When transfer functions of the low pass filter 232 and the high pass filter 233 are Q(s) and HPF(s), respectively, in a frequency band where a gain in gain characteristics of Q(s) and HPF(s) is 1, the transfer functions of the controlled object are restrained by a nominal model.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a motor control device, a motor control method, a motor module, and an electric power steering device. [Background technology]

[0002] Ordinary automobiles are equipped with an electric power steering system (EPS) that includes an electric motor (hereinafter simply referred to as "motor") and a motor control device. An electric power steering system is a device that assists the driver's steering wheel operation by driving a motor. Conventionally, torque control is used to realize motor output according to steering torque, thereby assisting steering operation.

[0003] Patent Documents 1 and 2 each disclose techniques related to disturbance observer control. Patent Document 1 uses a robust controller to reduce the impact of disturbances or parameter fluctuations of the controlled object on steering control. Patent Document 2 uses a resonance point disturbance controller configured with a disturbance observer to suppress resonance point disturbances excited at the longitudinal resonance point of the suspension. Patent Document 3 discloses a technique for eliminating friction torque generated by internal friction in the steering mechanism and generating an appropriate steering reaction force that does not cause discomfort in accordance with the road reaction force. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-219310 [Patent Document 2] International Publication No. 2016 / 208665 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-88610 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to improve the steering feel that the driver can feel when assisting the driver's steering operation.

[0006] In recent years, market demands for NVH (Noise, Vibration, and Harshness), a standard used to evaluate vehicle comfort, have become increasingly stringent. However, conventional torque control is particularly susceptible to high-frequency disturbances and is unable to suppress high-frequency torque fluctuations, making it difficult to meet market demands.

[0007] Conventionally, a friction model has been constructed as a function of the motor's angular velocity ω, and friction compensation control has been performed using this model. However, with typical friction characteristics, chattering can easily occur due to the sudden reversal of the sign of the friction torque when the motor's angular velocity ω approaches zero.

[0008] The present invention has been made to solve at least one of the above problems, and aims to provide a motor control device that can improve the steering feel that the driver can sense by applying model following control and / or friction compensation control to torque control, a motor module equipped with the control device, an electric power steering device equipped with the motor module, and a motor control method. [Means for solving the problem]

[0009] In a non-limiting exemplary embodiment, a control device of the present disclosure is a control device used in an electric power steering device equipped with a motor, for controlling the motor, and includes a model-following controller that generates a correction torque based on an output from a controlled object, which is the motor, and corrects an input to the controlled object by the correction torque, wherein the model-following controller includes a high-pass filter having a first cutoff frequency and a low-pass filter having a second cutoff frequency greater than the first cutoff frequency, and is configured such that, when the transfer functions of the low-pass filter and the high-pass filter are Q(s) and HPF(s), respectively, the transfer function of the controlled object is constrained to a nominal model in a frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1.

[0010] In a non-limiting exemplary embodiment, a motor module of the present disclosure includes a motor and the above-described control device.

[0011] In a non-limiting exemplary embodiment, an electric power steering apparatus according to the present disclosure includes the motor module described above.

[0012] In a non-limiting exemplary embodiment, a control method of the present disclosure is a computer-implemented method for controlling a motor of an electric power steering device including a motor, the method causing a computer to execute the following: generating a correction torque based on an output from the controlled object, and correcting an input to the controlled object with the correction torque, using a model-following controller including a high-pass filter having a first cutoff frequency and a low-pass filter having a second cutoff frequency greater than the first cutoff frequency, where the transfer functions of the low-pass filter and the high-pass filter are Q(s) and HPF(s), respectively, and constraining the transfer function of the controlled object, that is, the motor, to a nominal model in a frequency band where a gain in a gain characteristic of Q(s)·HPF(s) is 1. [Effects of the Invention]

[0013] According to an exemplary embodiment of the present disclosure, there are provided a motor control device capable of improving the steering feel that the driver can feel by applying model following control and / or friction compensation control to torque control, a motor module including the control device, an electric power steering device including the motor module, and a motor control method. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of an electric power steering device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing a typical example of the configuration of a control device according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a functional block diagram illustrating the functions of a processor for controlling a motor according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a functional block diagram showing an example of the configuration of a model following controller in the first implementation example. [Figure 5] FIG. 5 is a graph illustrating the gain characteristic T(s) of Q(s)·HPF(s) and the gain characteristic of the reciprocal of the modeling error Δ(s) between the plant and the nominal model Pn(s). [Figure 6] FIG. 6 is a graph illustrating a gain diagram of the transfer function C(s) of the phase compensator in the torque controller. [Figure 7] FIG. 7 is a graph illustrating a gain diagram of the transfer function HPF(s) of the high-pass filter. [Figure 8] FIG. 8 is a graph illustrating a gain diagram of the nominal model Pn(s). [Figure 9] FIG. 9 is a graph showing the measurement results of the steering angle and the torsion torque when the model following control is not applied. [Figure 10] FIG. 10 is a graph showing the measurement results of the steering angle and the torsion torque when the model following control is applied. [Figure 11] FIG. 11 is a graph showing the measurement results of the change in steering angle over time when model following control is not applied and when model following control is applied. [Figure 12] FIG. 12 is a functional block diagram showing a configuration example of a model following controller in the second implementation example. [Figure 13] FIG. 13 is a graph showing simulation results of steering angle and steering torque when friction compensation control is not applied and when friction compensation control is applied. [Figure 14] FIG. 14 is a graph showing simulation results of steering angle and steering torque when conventional friction compensation control is applied and when friction compensation control according to the second implementation example is applied. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, with reference to the accompanying drawings, embodiments of a motor control device mounted in an electric power steering device, a motor control method, a motor module including the control device, and an electric power steering device including the motor module of the present disclosure will be described in detail. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art.

[0016] The following embodiments are merely examples, and the motor control device and motor control method mounted on an electric power steering device according to the present disclosure are not limited to the following embodiments. For example, the numerical values, steps, and order of steps shown in the following embodiments are merely examples, and various modifications are possible as long as no technical contradictions occur. The embodiments or examples described below are merely examples, and various combinations are possible as long as no technical contradictions occur.

[0017] [1. Configuration of electric power steering device 1000] FIG. 1 schematically shows an example of the configuration of an electric power steering device 1000 according to an embodiment of the present disclosure.

[0018] The electric power steering device 1000 (hereinafter referred to as "EPS") has a steering system 520 and an assist torque mechanism 540 that generates an assist torque. The EPS 1000 generates an assist torque that assists the steering torque of the steering system that is generated when the driver operates the steering wheel. The assist torque reduces the driver's operational burden.

[0019] The steering system 520 includes, for example, a steering wheel 521, a steering shaft 522, universal joints 523A, 523B, a rotating shaft 524, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A, 552B, tie rods 527A, 527B, knuckles 528A, 528B, and left and right steering wheels 529A, 529B.

[0020] Assist torque mechanism 540 includes, for example, steering torque sensor 541, steering angle sensor 542, automotive electronic control unit (ECU) 100, motor 543, reduction gear 544, inverter 545, and torsion bar 546. Steering torque sensor 541 detects the amount of torsion of torsion bar 546 to detect the steering torque in steering system 520. Steering angle sensor 542 detects the steering angle of the steering wheel. Note that the steering torque may be an estimated value derived by calculation, rather than a value from the steering torque sensor. The steering angle may also be calculated based on the output value of an angle sensor.

[0021] ECU 100 generates a motor drive signal based on detection signals detected by a steering torque sensor 541, a steering angle sensor 542, a vehicle speed sensor (not shown) mounted on the vehicle, and the like, and outputs the generated signal to inverter 545. For example, inverter 545 converts DC power into three-phase AC power, which is a pseudo-sine wave of U-phase, V-phase, and W-phase, in accordance with the motor drive signal, and supplies the power to motor 543. Motor 543 is, for example, a surface permanent magnet synchronous motor (SPMSM) or a switched reluctance motor (SRM), and receives the three-phase AC power to generate assist torque according to the steering torque. Motor 543 transmits the generated assist torque to steering system 520 via reduction gear 544. Hereinafter, ECU 100 will be referred to as EPS control device 100.

[0022] The control device 100 and the motor are modularized and manufactured and sold as a motor module. The motor module includes the motor and the control device 100 and is suitable for use in an EPS. Alternatively, the control device 100 can be manufactured and sold as a control device for controlling an EPS, independent of the motor.

[0023] 2. Example of the configuration of the control device 100 2 shows a typical example of the configuration of a control device 100 according to an embodiment of the present disclosure. The control device 100 includes, for example, a power supply circuit 111, an angle sensor 112, an input circuit 113, a communication I / F 114, a drive circuit 115, a ROM 116, and a processor 200. The control device 100 can be realized as a printed circuit board (PCB) on which these electronic components are mounted. The control device 100 is used to control a motor of an electric power steering device that includes a motor.

[0024] A vehicle speed sensor 300, a steering torque sensor 541, and a steering angle sensor 542 mounted on the vehicle are communicatively connected to the processor 200, and the vehicle speed, steering torque, and steering angle are transmitted from the vehicle speed sensor 300, the steering torque sensor 541, and the steering angle sensor 542 to the processor 200, respectively.

[0025] The control device 100 is electrically connected to an inverter 545 (see FIG. 1). The control device 100 controls the switching operations of a plurality of switch elements (e.g., MOSFETs) included in the inverter 545. Specifically, the control device 100 generates control signals (hereinafter referred to as "gate control signals") that control the switching operations of the respective switch elements and outputs the control signals to the inverter 545.

[0026] The control device 100 generates a torque command value based on the steering torque, etc., and controls the torque and rotational speed of the motor 543, for example, by vector control. The control device 100 is not limited to vector control and can perform other closed-loop control. The rotational speed is expressed as the number of rotations (rpm) at which the rotor rotates per unit time (e.g., one minute) or the number of rotations (rps) at which the rotor rotates per unit time (e.g., one second). Vector control is a method of decomposing the current flowing through the motor into a current component that contributes to the generation of torque and a current component that contributes to the generation of magnetic flux, and independently controlling each of the mutually orthogonal current components.

[0027] The power supply circuit 111 is connected to an external power supply (not shown) and generates a DC voltage required for each block in the circuit. The generated DC voltage is, for example, 3V or 5V.

[0028] The angle sensor 112 is, for example, a resolver or a Hall IC. Alternatively, the angle sensor 112 can be realized by combining a magnetoresistive (MR) sensor having an MR element with a sensor magnet. The angle sensor 112 detects the rotation angle of the rotor and outputs the detected rotation angle to the processor 200. The control device 100 may include a speed sensor and an acceleration sensor that detect the rotation speed and acceleration of the motor instead of the angle sensor 112. The processor 200 calculates the electrical angle θ of the motor. m The angular velocity ω [rad / s] can be calculated based on the above.

[0029] The input circuit 113 receives a motor current value (hereinafter referred to as an "actual current value") detected by a current sensor (not shown), converts the level of the actual current value to an input level for the processor 200 as necessary, and outputs the actual current value to the processor 200. A typical example of the input circuit 113 is an analog-to-digital conversion circuit.

[0030] The processor 200 is a semiconductor integrated circuit, also referred to as a central processing unit (CPU) or microprocessor. The processor 200 sequentially executes a computer program, which is stored in the ROM 116 and contains instructions for controlling the motor drive, to perform desired processing. In addition to or instead of the processor 200, the control device 100 may include a field programmable gate array (FPGA) equipped with a CPU, a graphics processing unit (GPU), an application specific integrated circuit (ASIC), an application specific standard product (ASSP), or a combination of two or more circuits selected from these circuits. The processor 200 sets a current command value according to the actual current value and the rotor rotation angle, etc., generates a pulse width modulation (PWM) signal, and outputs it to the drive circuit 115.

[0031] The communication I / F 114 is, for example, an input / output interface for transmitting and receiving data in accordance with an in-vehicle control area network (CAN).

[0032] The drive circuit 115 is typically a gate driver (or pre-driver). The drive circuit 115 generates a gate control signal in accordance with the PWM signal and applies the gate control signal to the gates of multiple switch elements included in the inverter 545. When the drive target is a motor that can be driven at a low voltage, the gate driver may not necessarily be required. In this case, the function of the gate driver may be implemented in the processor 200.

[0033] The ROM 116 is electrically connected to the processor 200. The ROM 116 is, for example, a writable memory (e.g., PROM), a rewritable memory (e.g., flash memory, EEPROM), or a read-only memory. The ROM 116 stores a control program including a group of instructions for causing the processor 200 to control motor drive. For example, the control program is temporarily loaded into a RAM (not shown) at boot time.

[0034] 3 shows functional blocks of a processor 200 for controlling a motor according to an embodiment of the present disclosure. In the illustrated implementation example, the processor 200, which is a computer, sequentially executes processes (or tasks) required for motor control using a torque controller, a model-following controller, a subtractor, and an adder.

[0035] Each functional block is implemented in the processor 200 as software (or firmware) and / or hardware. The processing of each functional block is typically written in a computer program in software modules and stored in the ROM 116. However, when using an FPGA or the like, all or part of these functional blocks may be implemented as a hardware accelerator. Furthermore, the motor control method according to the embodiment of the present disclosure may be implemented in a computer and performed by causing the computer to perform desired operations.

[0036] The control device 100 includes a torque controller 210, a model following controller 230, a subtractor AD1, and an adder AD2. In other words, the processor 200 implements functions corresponding to the torque controller 210, the model following controller 230, the subtractor AD1, and the adder AD2.

[0037] The torque controller 210 controls the steering torque T h and provides an input to the controlled object 220, which is a motor. For example, the steering torque T his input to the torque controller 210. The torque controller 210 controls the steering torque T h By applying phase compensation to the target motor torque (or torque command value), T ref is generated and input to the control object 220.

[0038] The torque controller 210 illustrated in FIG. 3 includes a base assist calculation unit 211 and a phase compensator 212.

[0039] The base assist calculation unit 211 calculates the steering torque T h and vehicle speed. The base assist calculation unit 211 calculates the steering torque T h and the vehicle speed. For example, the base assist calculation unit 211 calculates the base assist torque based on the steering torque T h The base assist calculation unit 211 may have a look-up table (LUT) that defines the correspondence between the vehicle speed and the base assist torque. The base assist calculation unit 211 refers to the LUT to calculate the steering torque T h Based on the steering torque T h The base assist gain can be determined based on a gradient defined by the ratio of the amount of change in the base assist torque to the amount of fluctuation in the torque.

[0040] The phase compensator 212 in the embodiment of the present disclosure adjusts the assist gain within a range of possible steering frequencies when the driver operates the steering wheel, thereby compensating for the stiffness of the torsion bar. In the embodiment of the present disclosure, an example of the predetermined range is 5 Hz or less. The phase compensator 212 may apply, for example, first-order phase compensation to the steering torque (torsion torque) when the steering frequency is 5 Hz or less. The first-order phase compensation is expressed, for example, by a transfer function in the mathematical expression (1).

number

[0041] The phase compensator 212 calculates the target motor torque T based on the base assist torque and base assist gain output from the base assist calculation unit 211. ref For example, the phase compensator 212 is a stabilization compensator and can apply stability phase compensation to the base assist torque. The phase compensator 212 can have a second-order or higher transfer function whose frequency characteristics are variable depending on the base assist gain. The second-order or higher transfer function is expressed using a responsiveness parameter ω and a damping parameter ζ. The second-order or higher transfer function can be expressed by, for example, Equation 2. By making the order of the transfer function second-order, damping can be applied to the characteristics of the transfer function. Changing the damping makes it possible to adjust the phase characteristics.

number

[0042] The model following controller 230 is configured to estimate a disturbance torque based on the motor angular velocity ω (MR angular velocity) which is an output from the controlled object 220, calculate the estimated disturbance torque, and feed it back to the input of the controlled object 220. The torque fed back from the model following controller 230 to the input of the controlled object 220 corresponds to a "correction torque" that corrects the input of the controlled object 220. The model following controller 230 generates the correction torque based on the output of the controlled object 220. An example of the model following controller 230 is a model following controller configured to perform model following control. A specific configuration of the model following controller 230 will be described in detail later.

[0043] The subtractor AD1 subtracts the target motor torque T ref The output from the subtractor AD1 is input to an adder AD2 and the model following controller 230. The adder AD2 subtracts the estimated disturbance torque T d and output the result to the control object 220. Here, examples of disturbances in the embodiment of the present disclosure include friction caused by mechanisms such as the motor and reduction gear, torque ripple or rattle, self-aligning torque, or disturbances that may occur when traveling on an unpaved, bumpy road or gravel road. Here, self-aligning torque refers to torque that acts in the direction of returning the steering wheel due to the elasticity of the tire that twists when the steering wheel is turned.

[0044] [First implementation example] A model-following controller has an inverse plant model, a high-pass filter, and a low-pass filter (or Q filter). When the transfer functions of the low-pass filter and the high-pass filter are Q(s) and HPF(s), respectively, the model-following controller calculates the inverse plant model P(s) of the controlled object in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1. nIn this specification, "the transfer function of the controlled object is constrained to the nominal model" means that the controlled object is controlled so that the transfer function of the controlled object appears to be the transfer function of the nominal model when the input / output relationship is viewed, for example.

[0045] 4 shows a configuration example of model-following controller 230A in the first implementation example. Model-following controller 230A has controlled object inverse model 231, low-pass filter 232, high-pass filter 233, and subtractor SU1. High-pass filter 233 has a first cutoff frequency, and low-pass filter 232 has a second cutoff frequency.

[0046] The angular velocity ω of the motor is input to the controlled object inverse model 231. The subtractor SU1 subtracts the output of the subtractor AD1 from the output of the controlled object inverse model 231 to obtain the estimated disturbance torque ^T d Generates the estimated disturbance torque ^T d is filtered by a low-pass filter 232 and a high-pass filter 233 connected in series in this order, and is input to the subtractor AD1. In this way, the model following controller 230A calculates the estimated disturbance torque ^T d is fed back to the input of the controlled object 220. d " is the hatched T shown in Figures 4 and 12. d means.

[0047] The model-following controller 230A executes model-following control, which refers to a feedback loop that uses the angular velocity ω of the motor, which is the controlled object 220, as the outer loop of current control. In the first implementation example, the feedback loop formed by the model-following controller 230A makes it possible to compensate for torque ripple that depends on the angular velocity ω. The angular velocity ω signal used for control can be corrected for each type of motor, and the accuracy of the angular velocity ω signal can be increased compared to current signals, etc. As a result, highly accurate torque ripple compensation can be applied to torque control.

[0048] The model-following controller 230A is similar in configuration to a conventional disturbance estimator (or disturbance observer), but has different intended actions and effects. A conventional disturbance estimator estimates the disturbance torque by selecting an inverse plant model close to the plant model, and reduces the influence of the disturbance by adjusting the disturbance torque in advance. The frequency band that is the target of this compensation is a low frequency of 4 Hz or less that can be taken in vehicle behavior.

[0049] Model-following control according to an embodiment of the present disclosure utilizes the effect of a feedback loop that constrains a plant to a nominal model defined by an inverse plant model. The frequency band that can be compensated for is approximately 4 Hz to 150 Hz, which is different from the frequency band of conventional disturbance estimators. For example, if an inverse plant model is defined so that there is no torque ripple, model-following control constrains the plant model to a torque-ripple-free characteristic. As a result, torque ripple can be reduced by applying torque ripple compensation. Alternatively, by constructing an inertia or viscosity model and constraining the plant model to that model, the inertia or viscosity of the plant model can be reduced. By performing model-following control, in addition to compensating for motor torque ripple, for example, loss torque compensation or motor inertia compensation can be performed.

[0050] In this specification, the controlled object 220, the nominal model (or plant model) used to constrain the controlled object 220, the controlled object inverse model 231 defined by the inverse plant model of the plant model, the transfer function of the low-pass filter 232, and the transfer function of the high-pass filter 233 are respectively referred to as P(s), P n (s), P n -1 (s), Q(s) and HPF(s).

[0051] The plant model (nominal model) is expressed by the formula 3, and the inverse plant model is expressed by the formula 4. mn and B mnBy appropriately setting, it is possible to impart a desired frequency characteristic to P(s) of the controlled object 220. In this embodiment, the plant model (nominal model) is a model of a one-inertia system.

number

number

[0052] Let T(s) be the complementary sensitivity function of the inner loop composed of a model-following controller, and Δ(s) be the modeling error of the plant model. T(s) is expressed as Q(s)HPF(s), and the relationship shown in equation 5 holds for Δ(s). The robust stability of a model-following controller is guaranteed when the small gain theorem shown in equation 6 holds between T(s) and Δ(s). For disturbance suppression, it is sufficient for T(s)=1, but when robust stability is taken into consideration, equation 6 must be satisfied. As can be seen from this, disturbance suppression and robust stability are incompatible.

number

number

[0053] Figure 5 shows an example of a gain diagram of the transfer function of the entire steering system. In the gain diagram, the horizontal axis represents frequency (Hz) and the vertical axis represents gain (dB). In the first implementation example, to achieve disturbance suppression by frequency band, the frequency band is divided into Region I where disturbance suppression is required, where T(s) = 1, and Region II where T(s) is lowered to ensure robust stability. In Region II, 1 / Δ(s) > T(s) holds.

[0054] The gain characteristics of the transfer function of the entire steering system have peaks, for example, near 20 Hz and near 50 Hz, and the modeling error appears in the peak near 50 Hz of the two peaks. That is, Δ(s) has a peak near 50 Hz, and 1 / Δ(s) shown in Figure 5 has a bottom near 50 Hz. There are two methods for adjusting the gain characteristics: adjusting 1 / Δ(s) and adjusting the break point of T(s). Adjusting 1 / Δ(s) is done by adjusting the J of the plant model. mn and B mn The adjustment of the break point of T(s) is performed by adjusting the second cutoff frequency of low-pass filter 232. Furthermore, the sensitivity to disturbances can be adjusted by the amount of steering assist, the steering speed, or the vehicle speed. When the bottom frequency of the modeling error is close to the frequency at the boundary between Region I and Region II, a method is often adopted as a countermeasure, in which the order of low-pass filter 232 is increased to steeply drop T(s) in Region I, where disturbance suppression is required.

[0055] The control device 100 performs torque control for low-frequency torque signals and performs control for high-frequency disturbances so that the angular velocity ω≈0, thereby stabilizing steering so that the steering wheel does not get out of hand. To achieve this goal, the control device 100 uses the torque controller 210 to reduce the high-frequency gain of the torque control, and uses the model following controller 230A to constrain the control target P(s) to a characteristic that reduces the high-frequency gain. The reason for performing the latter process is to prevent the control target 220 from reacting to a disturbance such as Td shown in FIG. 4 when the disturbance is input to the control target 220.

[0056] 6 shows an example of a gain diagram of the transfer function C(s) of the phase compensator 212 in the torque controller 210. FIG. 7 shows an example of a gain diagram of the transfer function HPF(s) of the high-pass filter 233. FIG. 8 shows an example of a gain diagram of the nominal model P n 6 shows an example of a gain diagram of the nominal model P(s). In the gain diagram, the horizontal axis indicates frequency (Hz) and the vertical axis indicates gain (dB). For example, if a phase compensator 212 having the gain characteristics of the transfer function C(s) shown in FIG. 6 is applied, the gain of the nominal model P(s) isn The high frequency gain can be reduced in the gain characteristic of the transfer function C(s). The cutoff frequency fc in the gain diagram of the transfer function C(s) is, for example, 2 Hz or more and 10 Hz or less, and P n The cutoff frequency fc in the gain diagram of (s) is, for example, 2 Hz or more and 20 Hz or less.

[0057] The model following controller 230A calculates whether the transfer function P(s) of the controlled object 220 is equal to the nominal model P(s) in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1. n (s). The inverse plant model P n -1 (s) is designed to give the inverse characteristic to be constrained and to take advantage of the gain characteristic of Q(s)·HPF(s). mn and B mn By properly designing the nominal model P, the gain decreases in the high frequency range as shown in Figure 8. n A gain characteristic of (s) is obtained. The boundary frequency between Region I and Region II (the lower limit of the frequency range defining Region I) is the maximum frequency that can be input by the driver, and is generally about 2 Hz to 10 Hz. This frequency depends on the first cutoff frequency of high-pass filter 233. Therefore, the lower limit frequency of the effective range of model following control is determined by adjusting the first cutoff frequency of high-pass filter 233 so as not to impede torque control.

[0058] The low-pass filter 232 and the high-pass filter 233 are connected in series. The low-pass filter 232 may be configured with multiple LPF stages. That is, Q(s) may be expressed as the transfer function of an n-stage LPF (n is 1 or more). The second cutoff frequency is higher than the first cutoff frequency. The first cutoff frequency is, for example, 2 Hz or more and 10 Hz or less, and preferably, for example, 5 Hz or more and 7 Hz or less. The second cutoff frequency is, for example, 3 Hz or more and preferably 50 Hz or less. However, the upper limit of the second cutoff frequency may be set to approximately 140 Hz to 200 Hz. The nominal model P shown in FIG. 8 n The cutoff frequency fc of the gain characteristic (s) depends on the first cutoff frequency and the second cutoff frequency, and is, for example, 2 Hz or more and 20 Hz or less.

[0059] The inventors of the present invention have confirmed the effects of applying model following control according to the embodiments of the present disclosure by conducting measurements on an actual vehicle. In the measurements on the actual vehicle, the effect of reducing torque ripple and steering pull by applying model following control to torque control was measured. Here, steering pull refers to the steering wheel swaying from side to side when going over a bump with the hands off the wheel.

[0060] Figure 9 shows the measurement results of the steering angle and torsion torque when model following control is not applied. Figure 10 shows the measurement results of the steering angle and torsion torque when model following control is applied. In the graph, the horizontal axis represents the steering angle (deg) and the vertical axis represents the torsion torque (Nm). The graph shows the waveform measured when steering from end to end (from turning the steering wheel fully left to fully right, or vice versa) at an angular velocity of 180 (deg / s).

[0061] When the area enclosed by the dashed line in the graph is enlarged, it is clear that torque ripple is suppressed when model following control is applied compared to when it is not applied. Specifically, it was found that the amount of variation in torsion torque is reduced by about 0.1 [Nm].

[0062] Figure 11 shows the measurement results of the change in steering angle over time when model following control is not applied and when it is applied. In the graph, the horizontal axis represents time [sec] and the vertical axis represents steering angle [deg]. The region of time when the vehicle went over the step is shown by the dashed rectangle. It was found that by applying model following control to torque control, the fluctuation in steering angle when the vehicle went over the step was suppressed, and steering wheel pull was appropriately reduced.

[0063] According to the first implementation example, applying model following control to torque control makes it possible to reduce high-frequency components of disturbances, thereby making it possible to appropriately reduce torque ripple that may occur when steering and steering wheel pull that may occur when the vehicle goes over a bump.

[0064] [Second implementation example] Next, a model following controller according to a second implementation example will be described with reference to Figures 12 to 14. The model following controller according to the second implementation example differs from the model following controller according to the first implementation example in that it includes a friction compensation calculator. Below, the differences from the model following controller according to the first implementation example will be mainly described.

[0065] Since the disturbances estimated by the model-following controller include mechanical friction such as that of the motor and reduction gear, the model-following controller according to the second implementation example is configured to extract the friction component from the estimated disturbance torque and apply friction compensation to the estimated disturbance torque. The targets of friction compensation include, for example, motor friction, reduction gear friction, or left-right friction difference of the reduction gear.

[0066] When conventional friction compensation control is applied, when the motor angular velocity ω is near zero, it is necessary to make the change in the friction compensation torque (Nm) relative to the motor angular velocity ω gentle in order to prevent chattering, and as a result, it is sometimes impossible to perform highly accurate friction compensation control. According to the inventor's investigation, in order to solve this problem, it is desirable to successively estimate and compensate for friction.

[0067] A model-following controller according to a second implementation example is configured to feed back a disturbance compensation torque to an input of a controlled object. Specifically, the model-following controller includes a high-pass filter that removes low-frequency components from an estimated disturbance torque, a friction compensation calculator connected in parallel to the high-pass filter that applies friction compensation to the estimated disturbance torque to calculate an estimated value of mechanical friction torque, and an adder that adds the estimated value of friction torque to the estimated disturbance torque from which the low-frequency components have been removed by the high-pass filter to generate disturbance compensation torque. In the second implementation example, the estimated disturbance torque corresponds to a "first correction torque" and the disturbance compensation torque corresponds to a "second correction torque."

[0068] 12 shows an example of the configuration of the model following controller 230B in the second implementation example. The model following controller 230B is configured to perform model following control in the same manner as the model following controller 230A in the first implementation example. However, the model following control function is not essential.

[0069] The model following controller 230B includes a friction compensation calculator 250. The friction compensation calculator 250 is connected in parallel to the high-pass filter 233 and calculates the estimated disturbance torque ^T d , and calculates an estimated value of the friction torque of the mechanism. Friction compensation calculator 250 has a subtractor 251, a limiter 252, and a gain adjuster 253. Subtractor 251 subtracts the output value from high-pass filter 233 from the output value from low-pass filter 232. Limiter 252 limits the output value from subtractor 251. If the input value exceeds an upper or lower threshold, limiter 252 clips the input value to the upper or lower threshold.

[0070] The gain adjuster 253 multiplies the output value from the limiter 252 by a gain K. The maximum value of the gain K of the gain adjuster 253 is determined under the condition that the transfer function of the controlled object 220 is constrained to the nominal model. The maximum value of the gain K is set to, for example, about 1 to 1.2.

[0071] Estimated disturbance torque^T d This includes mechanical friction. In estimating the disturbance, friction is first estimated from the transmission path of the motor's output torque, and then torque acting on the motor, such as self-aligning torque, is estimated. For this reason, friction compensation calculator 250 calculates a value equivalent to the friction torque from the initially estimated disturbance as an estimated value of friction torque. Since an appropriate amount of friction is generally required for EPS, by setting a value smaller than the actual friction force as the estimated value of friction torque, it is possible to achieve highly accurate friction compensation while maintaining an appropriate amount of friction force.

[0072] To apply friction compensation to the estimated disturbance torque used in model-following control, attention must be paid to the stability condition of model-following control. This condition, according to the small-gain theorem described above, requires that the gain in the gain characteristic of the transfer function of friction compensation calculator 250, which is constrained to a characteristic that takes stability into consideration, does not exceed 1. This is derived from the design conditions of low-pass filter 232. In the second implementation example, the friction compensation gain, i.e., the value of gain K, is set to a maximum of 1 so as to always satisfy this condition, and subtractor 251 is provided before limiter 252 to apply subtraction processing so that the gain in the gain characteristic becomes 1 under this condition. In other words, friction compensation calculator 250 behaves as a low-pass filter having a transfer function of 1-HPF(s).

[0073] Estimated disturbance torque^T d is the low frequency component ^T d1 , medium frequency component ^T d2 , and the high frequency component ^T d3 The low-pass filter 232 includes the estimated disturbance torque ^T d to high frequency component ^Td3 The high-pass filter 233 further removes the estimated disturbance torque ^T d to the low frequency component ^T d1 In this way, the medium frequency component ^T of the estimated disturbance torque, which is in the range of not less than the first cutoff frequency of the high-pass filter 233 but not more than the second cutoff frequency of the low-pass filter 232, is removed. d2 However, since the assumed friction included in the disturbance is a low-frequency component of the disturbance, the above filtering process reduces the low-frequency component ^T d1 Therefore, by connecting the friction compensation calculator 250 in parallel with the high-pass filter 233, the low-frequency component ^T of the disturbance that has been filtered by the high-pass filter 233 and is no longer compensated for is eliminated. d1 Estimate the disturbance torque ^T d In more detail, the friction compensation calculator 250 calculates the low frequency component ^T d1 The value multiplied by the gain K is the mid-frequency component ^T d2 The disturbance compensation torque is generated by adding "^T d1 " is the hatched T shown in Figure 12. d1 means "^T d2 " is the hatched T shown in Figure 12. d2 means "^T d3 " is the hatched T shown in Figure 12. d3 means.

[0074] A vehicle equipped with an EPS can travel in a driving mode that includes an automatic driving mode and a manual driving mode. In this case, the gain K of the gain adjuster 253 may be switched depending on the driving mode. The larger the gain K, the greater the degree of friction reduction. The gain K set in the automatic driving mode is preferably larger than the gain K set in the manual driving mode. This allows for optimal friction compensation to be applied to the automatic driving mode, which requires greater friction reduction.

[0075] The model following controller 230B further includes an adder AD3. The adder AD3 adds the output value from the gain adjuster to the output value from the high-pass filter 233. The output from the adder AD3 is fed back to the input of the controlled object 220 as a disturbance compensation torque.

[0076] Assistance devices have been developed that recognize lane markings, such as white or yellow lines, when traveling on expressways, and assist the vehicle in autonomous driving by following the lane. It is known that in vehicles equipped with an EPS and an assistance device, a difference in friction between the left and right reduction gears can affect the control of the assistance device, which drives the vehicle straight along the center of the lane. According to the friction compensation control of the embodiments of the present disclosure, even if there is a difference in friction between the left and right reduction gears, it is possible to sequentially calculate an estimated value of friction torque, thereby solving the above problem. The motor angular velocity ω, which is the output of the plant model, includes information regarding the difference in friction between the left and right reduction gears.

[0077] The inventors have confirmed the effect of applying friction compensation control by gain adjustment through simulations, and measured the effect of reducing friction through friction compensation control through simulations.

[0078] Figure 13 shows the simulation results of steering angle and steering torque when friction compensation control by gain adjustment is not applied and when it is applied. In the graph, the horizontal axis represents steering angle [deg] and the vertical axis represents steering torque [Nm]. The dashed line represents the waveform when friction compensation control is not applied, and the solid line represents the waveform when friction compensation control is applied. The arrows in the figure represent the range of steering torque, which corresponds to the magnitude of friction. It was found that friction can be appropriately reduced by applying friction compensation control.

[0079] Figure 14 shows the simulation results of steering angle and steering torque when conventional friction compensation control and friction compensation control with gain adjustment are applied. In the graph, the horizontal axis represents steering angle [deg], and the vertical axis represents steering torque [Nm]. The dashed line represents the waveform when conventional friction compensation control is applied, and the solid line represents the waveform when friction compensation control with gain adjustment is applied. With conventional friction compensation control, as described above, when the motor angular velocity ω is near zero, the change in friction compensation torque (Nm) relative to the motor angular velocity ω must be made gradual to prevent chattering. As a result, a spike in steering torque was observed when turning the steering wheel (see the area circled by the dashed line in the figure). In contrast, when friction compensation control with gain adjustment is applied, no spike was observed, indicating that friction was appropriately reduced.

[0080] According to the second implementation example, by further applying friction compensation control by gain adjustment to torque control, it becomes possible to reduce high frequency components of disturbances while also reducing friction appropriately.

[0081] [Third implementation example] In the third implementation example, the control object includes a steering wheel 521, universal joints 523A and 523B, a rotating shaft 524, a torsion bar 546, a motor 543, and a reduction gear 544. Because the control object in the third implementation example includes parts that can rotate relatively to each other via the torsion bar 546, the motion of the control object cannot be described by a simple equation of motion for a one-inertia system. The control object in the third implementation example changes between a one-inertia system and a two-inertia system depending on the strength with which the driver of the vehicle grips the steering wheel 521. The stronger the driver grips the steering wheel 521, the closer the control object becomes to a one-inertia system. The weaker the driver grips the steering wheel, the closer the control object becomes to a two-inertia system. In the third implementation example, an angular velocity corresponding to the angular velocity of the reduction gear 544 is input to the model-following controller as the output of the control object.

[0082] In the third implementation example, the plant model (nominal model) is a model having frequency characteristics between the one-inertia system and the two-inertia system. The transfer function P n (s) is expressed by the formula 7, and the transfer function P n -1 (s) is expressed by the formula in equation 8.

[0083]

number

[0084]

number

[0085] In the formulas of formulas 7 and 8, s is the Laplace transform, and J STGn is a parameter that represents the moment of inertia of the nominal model, and B STGn is a parameter representing the viscous friction coefficient of the nominal model, and ω 1n is the transfer function P n is the frequency of the zero point of (s), and ω 2n is the transfer function P n is the frequency of the pole of (s), and ζ 1n is the transfer function P n is the damping ratio at the zero point of (s), and ζ 2n is the transfer function P n (s) is the damping ratio at the pole.

[0086] In the third implementation example, the nominal model is a model having frequency characteristics between the one-inertia system and the two-inertia system. The transfer function P n The formula (7) for (s) is an equation that adds a damping term to the formula for a two-inertia system. In the formula (7), the damping term is 2ζ 1n ω 1n s and 2ζ 2n ω 2n s. The equation obtained by removing these damping terms from Equation 7 is the equation representing the two-inertia system. In the third implementation example, the transfer function Pn The degree of (s) is 3.

[0087] In the third implementation example, the nominal model is a model that takes into account the mechanical characteristics when the driver (steerer) steers the steering wheel 521. The more strongly the driver grips the steering wheel 521, the closer the controlled object is to a one-inertia system, and the more weakly the driver grips the steering wheel 521, the closer it is to a two-inertia system. Therefore, the transfer function P(s) of the controlled object in the third implementation example changes between the one-inertia system and the two-inertia system depending on how force is applied to the steering wheel 521 from the driver's arms. In the third implementation example, by making the nominal model a model that has frequency characteristics between the one-inertia system and the two-inertia system, the transfer function P of the nominal model can be n This can prevent the modeling error Δ(s) between (s) and the transfer function P(s) of the controlled object from becoming too large. Therefore, the controlled object can be suitably controlled using the nominal model regardless of how the driver steers the steering wheel 521. In this way, in the third implementation example, the nominal model is a model that takes into account the mechanical characteristics that are imparted to the controlled object depending on how the driver grips the steering wheel 521. The control device 100 in the third implementation example has such a nominal model as an internal model, and can therefore perform suitable control of the controlled object. Other configurations in the third implementation example can be similar to those of the other implementation examples described above.

[0088] Although the control device in each of the above-described implementation examples includes a torque controller that provides an input to a controlled object, which is a motor, the present disclosure is not limited to this. The control device according to the present disclosure does not necessarily need to include a torque controller. [Industrial Applicability]

[0089] An embodiment of the present disclosure can be used in a motor control device for controlling an EPS mounted on a vehicle. [Explanation of symbols]

[0090] 100: control device (ECU), 200: processor, 210: torque controller, 211: response phase compensation unit, 212: phase compensator, 220: controlled object, 230, 230A, 230B: model following controller, 231: controlled object inverse model, 232: low-pass filter, 233: high-pass filter, 250: friction compensation calculator, 251: subtractor, 252: limiter, 253: gain adjuster, 1000: electric power steering device, AD1: subtractor, AD2, AD3: adders, SU1: subtractor

Claims

1. A control device for controlling an electric power steering device including a motor, the control device comprising: a model following controller that generates a correction torque based on an output from a controlled object that is the motor, and corrects a target motor torque that is an input to the controlled object with the correction torque; The model following controller a high-pass filter having a first cutoff frequency and a low-pass filter having a second cutoff frequency greater than the first cutoff frequency; an inverse model of a controlled object to which the output of the controlled object is input; Including, the control object inverse model is an inverse model of a nominal model, which is a plant model, the process of calculating the correction torque by the model following controller includes subtracting the target motor torque corrected by the correction torque from an output of the controlled object inverse model, and subjecting the subtracted value to filtering by the low-pass filter and filtering by the high-pass filter; the model following controller is configured such that, when transfer functions of the low-pass filter and the high-pass filter are Q(s) and HPF(s), respectively, an output of the controlled object becomes equal to an output of the nominal model when the target motor torque is input to the nominal model in a frequency band where a gain in a gain characteristic of Q(s)·HPF(s) is 1; The control device, wherein the nominal model includes a parameter representing a moment of inertia of the nominal model and a parameter representing a viscous friction coefficient of the nominal model.

2. The control device according to claim 1 , wherein the first cutoff frequency is equal to or greater than 2 Hz and equal to or less than 10 Hz.

3. The control device according to claim 2 , wherein the second cutoff frequency is equal to or greater than 3 Hz.

4. A motor; The control device according to any one of claims 1 to 3; A motor module comprising:

5. An electric power steering device comprising the motor module according to claim 4.

6. 1. A computer-implemented method for controlling a motor of an electric power steering device including a motor, comprising: a model following controller including a high-pass filter having a first cutoff frequency, a low-pass filter having a second cutoff frequency greater than the first cutoff frequency, and a controlled object inverse model which is an inverse model of a nominal model which is a plant model and to which an output of a controlled object which is the motor is input, wherein when transfer functions of the low-pass filter and the high-pass filter are Q(s) and HPF(s), respectively, the model following controller is configured so that the output of the controlled object becomes equal to the output of the nominal model when a target motor torque is input to the nominal model in a frequency band where a gain in a gain characteristic of Q(s)·HPF(s) is 1; generating a correction torque based on the output from the controlled object and correcting the target motor torque which is an input of the controlled object with the correction torque; performing a process of calculating the correction torque by the model following controller, the process including subtracting the target motor torque after being corrected by the correction torque from the output of the controlled object inverse model, and filtering the subtracted value using the low-pass filter and the high-pass filter; The method, wherein the nominal model includes a parameter representing a moment of inertia of the nominal model and a parameter representing a viscous friction coefficient of the nominal model.

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