Control device and method for a motor, motor module, electric power steering device

Abstract

The present application provides a motor control device and method, a motor module, and an electric power steering device. The motor control device has a torque controller that acts in accordance with a steering torque to provide an input to a control target that is a motor, and a model following controller that generates a first correction torque in accordance with an output from the control target. The model following controller has a high-pass filter that removes low-frequency components from the first correction torque, a friction compensation calculator that is coupled in parallel with the high-pass filter to calculate an estimated value of a friction torque of the motor by applying friction compensation to the first correction torque, and an adder that adds the estimated value of the friction torque to the first correction torque from which the low-frequency components have been removed by the high-pass filter to generate a second correction torque, and the control device feeds back the second correction torque to the input of the control target.

Description

Technical Field

[0001] This invention relates to a motor control device, a motor control method, a motor module, and an electric power steering device. Background Technology

[0002] Most cars are equipped with an electric motor (hereinafter referred to as "motor") and an electric power steering (EPS) system with a motor control device. The electric power steering system is a device that assists the driver in operating the steering wheel (or steering wheel) by driving the motor. Previously, torque control was used to achieve motor output corresponding to the steering torque, thereby assisting in steering wheel operation.

[0003] Patent documents 1 and 2 disclose technologies related to interference observer control. Patent document 1 uses a robust controller to reduce the impact of parameter variations of the interference or controlled object on steering control. Patent document 2 uses a resonance point interference controller composed of an interference observer to suppress resonance point interference excited at the resonance point in the forward and backward directions of the suspension. Patent document 3 discloses a technology to eliminate frictional torque generated by internal friction of the steering mechanism, thereby generating an appropriate steering reaction force corresponding to the road surface reaction force without discomfort.

[0004] Patent Document 1: Japanese Patent Application Publication No. 06-219310

[0005] Patent Document 2: International Publication No. 2016 / 208665

[0006] Patent Document 3: Japanese Patent Application Publication No. 2005-88610

[0007] The aim is to improve the steering feel that the driver can perceive when assisting with steering wheel operations.

[0008] In recent years, the market has placed increasingly stringent demands on NVH (noise, vibration, and harshness), a benchmark for evaluating vehicle comfort. However, existing torque control systems are particularly susceptible to high-frequency interference and cannot suppress high-frequency torque fluctuations, thus failing to meet market requirements.

[0009] Previously, friction models were constructed as functions of the motor's angular velocity ω, and these models were used for friction compensation control. However, in typical friction characteristics, the following problem exists: near the zero angular velocity ω of the motor, the sign of the friction torque reverses sharply, which can easily cause oscillations. Summary of the Invention

[0010] The present invention was made to solve at least one of the above-mentioned problems, and its object is to provide a motor control device that can improve the steering feel that the driver can feel by applying model tracking control and / or friction compensation control to torque control, a motor module having the control device, an electric power steering device having the motor module, and a motor control method.

[0011] In a non-limiting and illustrative embodiment, the control device of the present invention is used in an electric power steering system having a motor for controlling the motor. The control device includes: a torque controller that operates according to a steering torque to provide input to a controlled object, which is the motor; and a model tracking controller that generates a first correction torque based on an output from the controlled object. The model tracking controller includes: a high-pass filter that removes low-frequency components from the first correction torque; a friction compensation calculator coupled in parallel with the high-pass filter to apply friction compensation to the first correction torque to calculate an inferred value of the friction torque of the machine; and an adder that adds the inferred value of the friction torque to the first correction torque (from which the low-frequency components have been removed by the high-pass filter) to generate a second correction torque. The control device feeds back the second correction torque to the input of the controlled object.

[0012] In a non-limiting and illustrative embodiment, the motor module of the present invention includes a motor and the control device described above.

[0013] The electric power steering device of the present invention includes the motor module described above in a non-limiting and exemplary embodiment.

[0014] In a non-limiting and illustrative embodiment, the control method of the present invention is used to control the motor of an electric power steering device having a motor, wherein the control method includes the following steps: acquiring a steering torque; determining an operating amount based on the steering torque and inputting it to a control object serving as the motor; generating a first correction torque based on an output from the control object; removing low-frequency components from the first correction torque; applying friction compensation to the first correction torque to calculate an inferred value of mechanical friction torque; adding the inferred value of friction torque to the first correction torque after removing the low-frequency components, thereby generating a second correction torque; and feeding the second correction torque back to the input of the control object.

[0015] According to an exemplary embodiment of the present invention, a motor control device is provided that can improve the steering feel perceived by the driver by applying model tracking control and / or friction compensation control to torque control, a motor module having the control device, an electric power steering device having the motor module, and a motor control method are provided. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating an example of the structure of an electric power steering device according to an embodiment of the present invention.

[0017] Figure 2 This is a block diagram illustrating a typical example of the structure of a control device according to an embodiment of the present invention.

[0018] Figure 3 This is a functional block diagram illustrating the functions of a processor used to control a motor according to an embodiment of the present invention.

[0019] Figure 4 This is a functional block diagram illustrating the structure of the model tracking controller in the first installation example.

[0020] Figure 5 This illustrates the gain characteristics T(s) of Q(s)·HPF(s) and the device (plant) versus the nominal model P. n A graph showing the gain characteristics of the reciprocal of the modeling error Δ(s) of (s).

[0021] Figure 6 This is a graph illustrating the gain curve of the transfer function C(s) of the phase compensator in the torque controller.

[0022] Figure 7 This is a graph illustrating the gain plot of the transfer function HPF(s) of a high-pass filter.

[0023] Figure 8 This illustrates the nominal model P. n The curve of the gain line plot of (s).

[0024] Figure 9 It is a graph showing the measured results of steering angle and torsional torque without applying model tracking control.

[0025] Figure 10 It is a graph showing the measured results of steering angle and torsional torque when model tracking control is applied.

[0026] Figure 11 This is a graph showing the measured results of the time variation of the steering angle for the cases where model tracking control is not applied and the cases where model tracking control is applied.

[0027] Figure 12 This is a functional block diagram illustrating the structure of the model tracking controller in the second installation example.

[0028] Figure 13 The graph shows the simulation results of steering angle and steering torque with and without friction compensation control.

[0029] Figure 14 The graph shows the simulation results of steering angle and steering torque when the existing friction compensation control is applied and when the friction compensation control of the second installation example is applied.

[0030] Label Explanation

[0031] 100: Control Unit (ECU); 200: Processor; 210: Torque Controller; 211: Responsive Phase Compensation Unit; 212: Phase Compensator; 220: Controlled Object; 230, 230A, 230B: Model Tracking 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 System; AD1: Subtractor; AD2, AD3: Adder; SU1: Subtractor. Detailed Implementation

[0032] Hereinafter, with reference to the accompanying drawings, a control device for a motor mounted on the electric power steering system of the present invention, a control method for the motor, a motor module having the control device, and embodiments of the electric power steering system having the motor module will be described in detail. However, sometimes unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of substantially the same structures are sometimes omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0033] The following embodiments are illustrative, and the control device and control method of the motor mounted in the electric power steering device of the present invention are not limited to the following embodiments. For example, the values, steps, and order of the steps shown in the following embodiments are merely examples, and various changes can be made as long as they do not create technical contradictions. The embodiments or examples described below are merely illustrative, and various combinations can be made as long as they do not create technical contradictions.

[0034] 【1. Structure of the Electric Power Steering System 1000】

[0035] exist Figure 1 The diagram schematically illustrates a structural example of an electric power steering device 1000 according to an embodiment of the present invention.

[0036] The electric power steering system 1000 (hereinafter referred to as "EPS") includes a steering system 520 and an auxiliary torque mechanism 540 that generates auxiliary torque. The EPS 1000 generates auxiliary torque to assist the steering torque of the steering system generated by the driver operating the steering wheel. The auxiliary torque reduces the driver's workload.

[0037] The steering system 520 includes, for example, a steering wheel 521, a steering shaft 522, universal joints 523A and 523B, a rotary shaft 524, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B, tie rods 527A and 527B, steering knuckles 528A and 528B, and left and right steering wheels 529A and 529B.

[0038] The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, a steering angle sensor 542, an automotive electronic control unit (ECU) 100, a motor 543, a reduction gear 544, an inverter 545, and a torsion bar 546. The steering torque sensor 541 detects the steering torque in the steering system 520 by detecting the amount of torsion in the torsion bar 546. The steering angle sensor 542 detects the steering angle of the steering wheel. Alternatively, the steering torque may not be the value from the steering torque sensor, but rather an inferred value derived through calculation. The steering angle can also be calculated based on the output value of an angle sensor.

[0039] The ECU 100 generates a motor drive signal based on detection signals detected by the steering torque sensor 541, steering angle sensor 542, and vehicle speed sensor (not shown), and outputs it to the inverter 545. For example, the inverter 545 converts DC power into three-phase AC power as pseudo-sine waves (U-phase, V-phase, and W-phase) based on the motor drive signal and supplies it to the motor 543. The motor 543, for example, is a surface magnet synchronous motor (SPMSM) or a switched reluctance motor (SRM), which receives the three-phase AC power supply and generates an auxiliary torque corresponding to the steering torque. The motor 543 transmits the generated auxiliary torque to the steering system 520 via a reduction gear 544. Hereinafter, the ECU 100 will be referred to as the EPS control device 100.

[0040] The control device 100 and the motor are modularized and manufactured and sold as a motor module. The motor module has a motor and control device 100 and is suitable for use in EPS. Alternatively, the control device 100 can be manufactured and sold independently of the motor as a control device for controlling EPS.

[0041] [2. Example of the structure of the control device 100]

[0042] exist Figure 2The diagram illustrates a typical example of the structure of a control device 100 according to an embodiment of the present invention. 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 implemented as a printed circuit board (PCB) on which these electronic components are mounted. The control device 100 is used to control the motor of an electric power steering system having a motor.

[0043] The vehicle speed sensor 300, steering torque sensor 541, and steering angle sensor 542 are connected to the processor 200 in a communicative manner, and send vehicle speed, steering torque, and steering angle to the processor 200 respectively from the vehicle speed sensor 300, steering torque sensor 541, and steering angle sensor 542.

[0044] Control device 100 and inverter 545 (see reference) Figure 1 Electrical connection. The control device 100 controls the switching operation of multiple switching elements (e.g., MOSFETs) in the inverter 545. Specifically, the control device 100 generates control signals (hereinafter referred to as "gate control signals") to control the switching operation of each switching element and outputs them to the inverter 545.

[0045] The control device 100 generates torque command values ​​based on steering torque, etc., and controls the torque and rotational speed of the motor 543, for example, through vector control. The control device 100 is not limited to vector control; it can also perform other closed-loop controls. The rotational speed is expressed as the rotor's rotational speed (rpm) per unit time (e.g., 1 minute) or the rotor's rotational speed (rps) per unit time (e.g., 1 second). Vector control is a method of decomposing the current flowing in the motor into current components that contribute to torque generation and current components that contribute to magnetic flux generation, and independently controlling these mutually perpendicular current components.

[0046] The power supply circuit 111 is connected to an external power source (not shown) to generate the DC voltage required by each block within the circuit. The generated DC voltage is, for example, 3V or 5V.

[0047] Angle sensor 112 is, for example, a rotary transformer or a Hall effect IC. Alternatively, angle sensor 112 can also be implemented by a combination of an MR sensor with a magnetoresistive (MR) element and a sensor magnet. Angle sensor 112 detects the rotation angle of the rotor and outputs this rotation angle to processor 200. Control device 100 may replace angle sensor 112 with a speed sensor or an acceleration sensor that detects the rotational speed and acceleration of the motor. Processor 200 can determine the rotation angle θ of the motor based on the motor's electrical angle θ. m To calculate the angular velocity ω [rad / s].

[0048] Input circuit 113 receives the motor current value (hereinafter referred to as "actual current value") detected by a current sensor (not shown), converts the level of the actual current value to the input level of processor 200 as needed, and outputs the actual current value to processor 200. A typical example of input circuit 113 is an analog-to-digital converter circuit.

[0049] Processor 200 is a semiconductor integrated circuit, also known as a central processing unit (CPU) or microprocessor. Processor 200 sequentially executes a computer program stored in ROM 116, which contains a set of instructions for controlling the motor drive, to achieve the desired processing. Control device 100 may, in addition to or in place of processor 200, include an FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), ASSP (Application Specific Standard Product), or a combination of two or more circuits selected from these circuits, all equipped with a CPU. Processor 200 sets the current command value based on the actual current value and the rotor's rotation angle, generates a PWM (Pulse Width Modulation) signal, and outputs it to drive circuit 115.

[0050] The communication I / F 114 is, for example, an input / output interface for transmitting and receiving data based on the vehicle's control area network (CAN).

[0051] The drive circuit 115 is typically a gate driver (or pre-driver). The drive circuit 115 generates a gate control signal based on the PWM signal and provides the gate control signal to the gates of the multiple switching elements of the inverter 545. When the driven object is a motor that can be driven at low voltage, a gate driver may not always be necessary. In this case, the function of the gate driver can be installed in the processor 200.

[0052] ROM 116 is electrically connected to processor 200. ROM 116 is, for example, a writable memory (e.g., PROM), a rewritable memory (e.g., flash memory, EEPROM), or a dedicated read memory. ROM 116 stores a control program containing a set of instructions for enabling processor 200 to control motor drive. For example, the control program is temporarily expanded to RAM (not shown) during boot.

[0053] exist Figure 3The diagram shows functional blocks of a processor 200 used for controlling a motor according to an embodiment of the present invention. In the illustrated installation example, the processor 200, acting as a computer, sequentially executes the processing (or tasks) required for motor control using a torque controller, a model tracking controller, a subtractor, and an adder.

[0054] Each functional block is installed in the processor 200 as software (or firmware) and / or hardware. The processing of each functional block is typically described in a computer program as a software module and stored in ROM 116. However, when using an FPGA or the like, all or part of these functional blocks can be installed as hardware accelerators. Furthermore, the motor control method of embodiments of the present invention can be implemented by installing it in a computer and having the computer perform the desired actions.

[0055] The control device 100 includes a torque controller 210, a model tracking controller 230, a subtractor AD1, and an adder AD2. In other words, the processor 200 is equipped with functions corresponding to the torque controller 210, the model tracking controller 230, the subtractor AD1, and the adder AD2, respectively.

[0056] Torque controller 210 based on steering torque T h The system performs actions by providing input to the controlled object 220, which functions as a motor. For example, the steering torque T detected by the steering torque sensor 541. h The torque is input to the torque controller 210. When the steering frequency or steering speed is within a specified range, the torque controller 210 controls the steering torque T. h The target motor torque (or torque command value) T is generated by applying phase compensation. ref And input it into control object 220.

[0057] Figure 3 The illustrated torque controller 210 has a basic auxiliary calculation unit 211 and a phase compensator 212.

[0058] Basic auxiliary computing unit 211 obtains steering torque T h And vehicle speed. The basic auxiliary calculation unit 211 calculates the steering torque T based on the vehicle speed. h The basic auxiliary torque is generated based on the vehicle speed. For example, the basic auxiliary calculation unit 211 may have a specified steering torque T. h A lookup table (LUT) showing the correspondence between vehicle speed and basic auxiliary torque. The basic auxiliary calculation unit 211 can refer to the LUT and calculate the steering torque T. h The basic auxiliary torque is determined based on the vehicle speed and the corresponding relationship. Furthermore, the basic auxiliary calculation unit 211 can determine the basic auxiliary torque based on the change in the basic auxiliary torque and the steering torque T. hThe slope of the ratio of the change in the base auxiliary gain is used to determine the base auxiliary gain.

[0059] In embodiments of the present invention, the phase compensator 212 adjusts the auxiliary gain within a suitable range of steering frequencies when the driver operates the steering wheel, compensating for the stiffness of the torsion bar. In embodiments of the present invention, an example of the aforementioned range is below 5 Hz. The phase compensator 212 may also apply, for example, first-order phase compensation to the steering torque (torsional torque) when the steering frequency is below 5 Hz. First-order phase compensation is, for example, represented by the transfer function of the mathematical expression in Formula 1.

[0060] 【Mathematical Formula 1】

[0061]

[0062] Here, s is the Laplace transform operator, f1 is the frequency (Hz) of the zeros of the transfer function, and f2 is the frequency (Hz) of the poles of the transfer function. A graph plotted with gain (or loop gain) on the vertical axis and the logarithm of frequency on the horizontal axis is called a gain plot. In a gain plot, a zero is the intersection of the gain curve and the horizontal axis representing 0 dB, and a pole is the maximum point of the gain curve. For example, by making the frequency of the pole greater than that of the zero, phase lead compensation can be applied. The larger the frequency interval, the greater the phase lead.

[0063] Phase compensator 212 generates target motor torque T based on the basic auxiliary torque and basic auxiliary gain output from basic auxiliary calculation unit 211. ref For example, phase compensator 212 is a stabilizing compensator capable of applying stable phase compensation to the base auxiliary torque. Phase compensator 212 can have a transfer function of order two or higher whose frequency characteristics can change according to the base auxiliary gain. The transfer function of order two or higher is represented using the responsiveness parameter ω and the damping parameter ζ. The transfer function of order two or higher can, for example, be represented by a mathematical expression of equation 2. By setting the order of the transfer function to two, damping can be applied to the characteristics of the transfer function. By changing the damping, the phase characteristics can be adjusted.

[0064] 【Mathematical Formula 2】

[0065]

[0066] Here, s is the Laplace transform operator, ω1 is the frequency of the zero, ω2 is the frequency of the pole, ζ1 is the damping of the zero, and ζ2 is the damping of the pole. The frequency of the pole ω2 is less than the frequency of the zero ω1.

[0067] The model tracking controller 230 is configured to infer the disturbance torque based on the angular velocity ω (MR angular velocity) of the motor, which is an output from the controlled object 220, calculate the inferred disturbance torque, and feed it back to the input of the controlled object 220. The torque fed back to the controlled object 220 from the model tracking controller 230 is equivalent to a "correction torque" that corrects the input of the controlled object 220. The model tracking controller 230 generates this correction torque based on the output of the controlled object 220. An example of the model tracking controller 230 is a model tracking controller configured to perform model tracking control. The specific structure of the model tracking controller 230 will be described in detail later.

[0068] Subtractor AD1 obtains the target motor torque T ref The inferred disturbance torque output from the model tracking controller 230 is subtracted. The output from subtractor AD1 is input to adder AD2 and model tracking controller 230. Adder AD2 adds the disturbance torque T to the output from subtractor AD1. d And output to the controlled object 220. Here, examples of interference in embodiments of the present invention are friction, torque fluctuations or swaying caused by machinery such as motors and reduction gears, self-centering torque, or interference that may occur when driving on unpaved, shaky roads or gravel roads. Here, self-centering torque refers to the torque that acts in the direction that returns the steering wheel when the steering wheel is disengaged due to the elasticity of the torsional tires.

[0069] [Installation Example 1]

[0070] The model tracking controller has an inverse device model, a high-pass filter, and a low-pass filter (or Q-filter). The model tracking controller is configured such that, with the transfer functions of the low-pass and high-pass filters set to Q(s) and HPF(s) respectively, the transfer function P(s) of the controlled object is constrained to the nominal model P in the frequency band where the gain is 1 in the gain characteristic of Q(s)·HPF(s). n In (s). Furthermore, in this specification, "constraining the transfer function of the controlled object within the nominal model" means, for example, when observing the input-output relationship, 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.

[0071] exist Figure 4 The diagram shows a structural example of the model tracking controller 230A in the first installation example. The model tracking controller 230A includes a controlled object inverse model 231, a low-pass filter 232, a high-pass filter 233, and a subtractor SU1. The high-pass filter 233 has a first cutoff frequency, and the low-pass filter 232 has a second cutoff frequency.

[0072] The angular velocity ω of the motor is input to the inverse model 231 of the controlled object. Subtractor SU1 subtracts the output of subtractor AD1 from the output of the inverse model 231 of the controlled object to generate the inferred disturbance torque ^T. d Inferring the disturbance torque ^T d The input to the subtractor AD1 is sequentially filtered by a series-coupled low-pass filter 232 and a high-pass filter 233. In this way, the model tracking controller 230A infers the disturbance torque ^T. d The input is fed back to control object 220. Additionally, "^T d " refers to Figure 4 and Figure 12 The T-shirt with a brim shown d .

[0073] The model tracking controller 230A performs model tracking control of the outer loop, which represents the feedback loop of the motor (controlled object 220) used for current control. In the first installation example, the feedback loop formed by the model tracking controller 230A enables compensation for torque fluctuations dependent on the angular velocity ω. The signal of the angular velocity ω used for control can be corrected according to the type of motor, improving the accuracy of the angular velocity ω signal compared to current signals, etc. As a result, higher-precision torque fluctuation compensation can be applied to torque control.

[0074] The model tracking controller 230A is structurally similar to existing interference inferrs (or interference observers), but its target function and effect differ. Existing interference inferrs infer interference torque by selecting an inverse device model that approximates the device model's value, and reduce the impact of interference by pre-adding or subtracting the interference torque. The frequency band targeted for this compensation is the lower frequencies below 4Hz that can be obtained during vehicle behavior.

[0075] The model tracking control in this invention utilizes the effect of constraining the device within a nominal model defined by the inverse device model via a feedback loop. The frequency band that can be compensated is approximately 4Hz to 150Hz, which differs from the frequency band of existing interference inferrs. For example, if the inverse device model is defined in a way that eliminates torque fluctuations, then through model tracking control, the device model is constrained to have characteristics free of torque fluctuations. As a result, torque fluctuations can be reduced by applying torque fluctuation compensation. Furthermore, inertial or viscous models can also be constructed, and the device model can be constrained within these models to achieve low inertia or low viscosity. By performing model tracking control, in addition to compensating for motor torque fluctuations, loss torque compensation or motor inertia compensation can also be performed, for example.

[0076] In this specification, the controlled object 220, the nominal model (or device model) used to constrain the controlled object 220, the inverse model 231 of the controlled object defined by the inverse device model of the device 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), ... n (s), P n - 1 Q(s), Q(s), and HPF(s).

[0077] The equipment model (nominal model) is represented by mathematical expression 3, and the inverse equipment model is represented by mathematical expression 4. By appropriately setting J... mn and B mn This allows the controlled object 220 to be assigned the desired frequency characteristics of P(s). In this embodiment, the device model (nominal model) is a model of an inertial system.

[0078] 【Mathematical Expression 3】

[0079]

[0080] 【Mathematical Expression 4】

[0081]

[0082] Let T(s) be the complementary sensitivity function of the inner loop formed by the model tracking controller, and let Δ(s) be the modeling error of the device model. T(s) is represented by Q(s)HPF(s), and the relationship shown in Equation 5 holds with respect to Δ(s). The robust stability of the model tracking controller is guaranteed when the small gain theorem, expressed by Equation 6, holds between T(s) and Δ(s). To suppress interference, T(s) = 1 is sufficient, but if robust stability is considered, Equation 6 must be satisfied. Therefore, it can be understood that it is impossible to simultaneously achieve interference suppression and robust stability.

[0083] 【Mathematical Expression 5】

[0084]

[0085] 【Mathematical Expression 6】

[0086] Or |T(jω)Δ(jω)|<1,

[0087] exist Figure 5The diagram illustrates the gain plot of the transfer function of the entire steering system. The horizontal axis of the gain plot represents frequency [Hz], and the vertical axis represents gain [dB]. In the first installation example, to achieve interference suppression via the frequency band, the band is divided into region I, where interference suppression is required (T(s) = 1), and region II, where T(s) decreases to ensure robust stability. In region II, 1 / Δ(s) > T(s) holds true.

[0088] The gain characteristic of the transfer function of the entire steering system has peaks, for example, around 20 Hz and 50 Hz, and the modeling error occurs at the peak around 50 Hz. That is, Δ(s) has a peak around 50 Hz. Figure 5 The 1 / Δ(s) shown has a bottom near 50Hz. As methods for adjusting the gain characteristics, there are adjustments to 1 / Δ(s) and adjustments to the inflection point of T(s). The adjustment of 1 / Δ(s) is achieved by adjusting the J of the device model. mn and B mn The inflection point of T(s) is adjusted by adjusting the second cutoff frequency of the low-pass filter 232. Furthermore, the sensitivity to interference can be adjusted by the steering assist amount, steering speed, or vehicle speed. When the frequency at the bottom of the modeling error is close to the boundary frequency between region I and region II, a common approach is to increase the order of the low-pass filter 232 to cause a sharp decrease in T(s) in region I where interference suppression is required.

[0089] The control device 100 performs torque control on the low-frequency torque signal and controls the angular velocity ω≈0 for high-frequency interference, thereby stabilizing steering so that the steering wheel does not turn. To achieve this, the control device 100 performs the following: using the torque controller 210 to reduce the high-frequency gain of torque control and using the model tracking controller 230A to constrain the controlled object P(s) to have a characteristic of decreasing high-frequency gain. The reason for performing the latter processing is to... Figure 4 The T shown d When such interference is input to the control object 220, the control object 220 will not react to the interference.

[0090] exist Figure 6 The image shows a gain graph of the transfer function C(s) of the phase compensator 212 in the torque controller 210. Figure 7 The gain plot of the transfer function HPF(s) of the high-pass filter 233 is illustrated below. Figure 8 The nominal model P is illustrated in the example. n (s) is a gain plot. The horizontal axis of the gain plot represents frequency [Hz], and the vertical axis represents gain [dB]. For example, if the application has... Figure 6The phase compensator 212 with the gain characteristic of the transfer function C(s) shown is as follows: Figure 8 As shown, it is possible to achieve the nominal model P n In the gain characteristics of transfer function C(s), the high-frequency gain is reduced. The cutoff frequency fc in the gain plot of C(s) is, for example, above 2Hz and below 10Hz. n The cutoff frequency fc in the gain plot of (s) is, for example, above 2 Hz and below 20 Hz.

[0091] The model tracking controller 230A is configured to constrain the transfer function P(s) of the controlled object 220 to the nominal model P within the frequency band where the gain is 1 in the gain characteristic of Q(s)·HPF(s). n In (s). Inverse device model P n -1 (s) is designed to impart the inverse characteristics of the desired constraint, leveraging the gain characteristics of Q(s)·HPF(s). This is achieved through appropriate design of the device model's J... mn and B mn ,like Figure 8 As shown, a nominal model P that reduces gain in the high-frequency region can be obtained. n (s) Gain characteristics. The frequency of the boundary between Region I and Region II (which defines the lower limit of the frequency range of Region I) is the maximum frequency that can be input by the driver, typically around 2Hz to 10Hz. This frequency depends on the first cutoff frequency of the high-pass filter 233. Therefore, the lower limit frequency of the effective range of model tracking control is determined by adjusting the first cutoff frequency of the high-pass filter 233 to avoid hindering torque control.

[0092] Low-pass filter 232 and high-pass filter 233 are coupled in series. Low-pass filter 232 can be composed of multiple stages of LPF. That is, Q(s) can be expressed as the transfer function of 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, 2Hz or higher and 10Hz or lower, preferably 5Hz or higher and 7Hz or lower. The second cutoff frequency is, for example, 3Hz or higher, preferably 50Hz or lower. However, the upper limit of the second cutoff frequency can be set to about 140Hz to 200Hz. Figure 8 The nominal model P shown n The cutoff frequency fc of the gain characteristic of (s) depends on the first cutoff frequency and the second cutoff frequency, for example, above 2Hz and below 20Hz.

[0093] The inventors confirmed the effectiveness of applying the model tracking control of the embodiments of the present invention by conducting real-vehicle tests. In the real-vehicle tests, the effect of applying model tracking control to torque control to reduce torque fluctuations and steering wheel rotation was measured. Here, steering wheel rotation refers to the left-right swaying of the steering wheel when going over a step with the steering wheel released from the steering wheel.

[0094] exist Figure 9 The results of steering angle and torsional torque measurements without applying model tracking control are shown. Figure 10 The figure shows the measured results of steering angle and torsional torque when model tracking control is applied. In the graph, the horizontal axis represents the steering angle [deg], and the vertical axis represents the torsional torque [Nm]. The graph shows the waveform measured when steering at an angular velocity of 180 [deg / s] from end to end (the steering wheel switches from a fully turned left state to a fully turned right state, or vice versa).

[0095] Compared to the case without model tracking control, it can be seen that when model tracking control is applied, if the portion enclosed by the dashed line on the graph is magnified for observation, torque fluctuations can be suppressed. Specifically, the variation in torsional torque is reduced by approximately 0.1 Nm.

[0096] exist Figure 11 The graph shows the measured results of the time variation of the steering angle with and without model tracking control. In the graph, the horizontal axis represents time [sec], and the vertical axis represents the steering angle [deg]. The dashed rectangles represent the areas where the vehicle passes over the step. It can be seen that by applying model tracking control to torque control, the variation of the steering angle when the vehicle passes over the step can be suppressed, thereby appropriately reducing the steering wheel rotation.

[0097] According to the first installation example, by applying model tracking control to torque control, the high-frequency components of disturbances can be reduced. As a result, torque fluctuations that may occur during steering and steering wheel rotation that may occur when the vehicle goes over a step can be appropriately reduced.

[0098] [Installation Example 2]

[0099] Next, refer to Figures 12 to 14 The model tracking controller of the second installation example will be described below. The model tracking controller of the second installation example differs from the model tracking controller of the first installation example in that it includes a friction compensation calculator. The following mainly describes the differences between the model tracking controller of the second installation example and the one in the first installation example.

[0100] The disturbance inferred by the model tracking controller includes friction from machinery such as motors and reduction gears. Therefore, the model tracking controller in the second installation example is configured to extract the friction component from the inferred disturbance torque and apply friction compensation to the inferred disturbance torque. The object of friction compensation is, for example, the friction of the motor, the friction of the reduction gear, or the left-right friction difference of the reduction gear.

[0101] If conventional friction compensation control is to be applied, when the motor's angular velocity ω is near zero, the friction compensation torque (Nm) must change slowly relative to the motor's angular velocity ω to prevent oscillation. As a result, there are situations where high-precision friction compensation control cannot be achieved. According to the inventors' research, to solve this problem, it is preferable to sequentially infer friction and perform compensation.

[0102] The model tracking controller in the second installation example is configured to feed back the disturbance compensation torque to the input of the controlled object. Specifically, the model tracking controller includes: a high-pass filter that removes low-frequency components from the inferred disturbance torque; a friction compensation calculator coupled in parallel with the high-pass filter that applies friction compensation to the inferred disturbance torque to calculate the inferred value of the mechanical friction torque; and an adder that adds the inferred value of the friction torque to the inferred disturbance torque from which the low-frequency components have been removed by the high-pass filter, thereby generating the disturbance compensation torque. In the second installation example, the inferred disturbance torque is equivalent to the "first correction torque," and the disturbance compensation torque is equivalent to the "second correction torque."

[0103] exist Figure 12 The diagram shows a structural example of the model tracking controller 230B in the second installation example. The model tracking controller 230B is configured similarly to the model tracking controller 230A in the first installation example to perform model tracking control. However, the model tracking control function is not required.

[0104] The model tracking controller 230B includes a friction compensation calculator 250. The friction compensation calculator 250 is coupled in parallel with a high-pass filter 233 to infer the disturbance torque ^T. d Friction compensation is applied to calculate the inferred value of the frictional torque of the machine. The friction compensation calculator 250 includes a subtractor 251, a limiter 252, and a gain adjuster 253. The subtractor 251 subtracts the output value from the high-pass filter 233 from the output value from the low-pass filter 232. The limiter 252 imposes a limit on the output value from the subtractor 251. If the input value exceeds an upper or lower threshold, the limiter 252 limits the input value to the upper or lower threshold value.

[0105] Gain adjuster 253 applies a gain K to the output value from limiter 252. The maximum value of gain K of gain adjuster 253 is determined under the condition that the transfer function of controlled object 220 is constrained within the nominal model. The maximum value of gain K is, for example, set to approximately 1 to 1.2.

[0106] Inferring the disturbance torque^T d This involves mechanical friction. In the interference inference, friction is first inferred based on the transmission path of the motor's output torque, followed by the inference of torques acting on the motor, such as self-centering torque. Therefore, the friction compensation calculator 250 calculates a value equivalent to the friction torque initially inferred in the interference as the inferred value of the friction torque. Generally, to ensure that EPS requires moderate friction, by using a value smaller than the actual frictional force as the inferred value of the friction torque, high-precision friction compensation can be achieved while maintaining a moderate amount of residual friction.

[0107] To apply friction compensation to the inferred disturbance torque used in model tracking control, the stability condition of model tracking control needs to be considered. This condition, based on the aforementioned small gain theorem, constrains the gain in the gain characteristic of the transfer function of the friction compensation calculator 250, which takes stability into account, to not exceed 1. This is derived from the design conditions of the low-pass filter 232. In the second installation example, the friction compensation gain, i.e., the value of gain K, is set to a maximum of 1 in a way that always satisfies this condition, and a subtractor 251 is set before the limiter 252 to apply subtraction processing in a way that makes the gain in the gain characteristic 1 under this condition. In other words, the friction compensation calculator 250 functions as a low-pass filter with a 1-HPF(s) transfer function.

[0108] Inferring the disturbance torque^T d Contains low-frequency components^T d1 Mid-frequency components^T d2 and high-frequency components ^T d3 The low-pass filter 232 infers the interference torque ^T d Removal of high-frequency components ^T d3 The high-pass filter 233 also infers the interference torque ^T d Removal of low-frequency components ^T d1 Thus, the intermediate frequency component of the inferred interference torque, ^T, is only located within the range above the first cutoff frequency of the high-pass filter 233 and below the second cutoff frequency of the low-pass filter 232. d2 It becomes the object of friction compensation. However, since the imagined friction contained in the interference is a low-frequency component of the interference, according to the above filtering process, the low-frequency component ^T d1Besides being the object of friction compensation, the low-frequency components that were not compensated for by the high-pass filter 233 are thus excluded by parallel coupling of the friction compensation calculator 250 with the high-pass filter 233. d1 Add the inferred interference torque^T again d This achieves friction compensation. More specifically, by adjusting the low-frequency components in the friction compensation calculator 250... d1 The value obtained by multiplying by the gain K and the intermediate frequency component ^T d2 Adding them together generates interference compensation torque. Additionally, "^T" d1 " refers to Figure 12 The T-shirt with a brim shown d1 “^T d2 " refers to Figure 12 The T-shirt with a brim shown d2 “^T d3 " refers to Figure 12 The T-shirt with a brim shown d3 .

[0109] Vehicles equipped with EPS can operate in driving modes with both automatic and manual operation modes. In this case, the gain K of the gain adjuster 253 can also be switched according to the driving mode. The larger the gain K, the greater the reduction in friction. Preferably, the gain K set in automatic operation mode is larger than the gain K set in manual operation mode. Thus, optimal friction compensation can be applied to the automatic operation mode, where further friction reduction is required.

[0110] The model tracking controller 230B also includes an adder AD3. Adder AD3 adds the output value from the high-pass filter 233 to the output value from the gain adjuster. The output from adder AD3 is fed back to the input of the controlled object 220 as a disturbance compensation torque.

[0111] An auxiliary device is being developed that, when driving on highways, identifies lane markings such as white or yellow lines to assist vehicles in automatically following lanes. In vehicles equipped with EPS and the auxiliary device, it is known that if there is a left-right difference in friction of the reduction gears, it will affect the control of the auxiliary device that keeps the vehicle traveling straight along the center of the lane. According to the friction compensation control of the present invention, even when there is a left-right difference in friction of the reduction gears, the inferred value of the friction torque can be calculated sequentially, thus solving the aforementioned problem. Furthermore, the angular velocity ω of the motor output as the device model contains information related to the left-right difference in friction of the reduction gears.

[0112] The inventors conducted simulations to confirm the effectiveness of applying gain-adjustment-based friction compensation control. Through simulation, they measured the friction reduction effect of the friction compensation control.

[0113] exist Figure 13 The figure shows simulation results of steering angle and steering torque with and without gain-adjustment-based friction compensation control. In the graphs, the horizontal axis represents steering angle [deg] and the vertical axis represents steering torque [Nm]. The dashed line graph shows the waveform without friction compensation control, and the solid line graph shows the waveform with friction compensation control. The arrows in the figure represent the magnitude of the steering torque, which corresponds to the magnitude of friction. It can be seen that by applying friction compensation control, friction can be appropriately reduced.

[0114] exist Figure 14 The diagram shows simulation results of steering angle and steering torque with and without existing friction compensation control and gain-adjustment-based friction compensation control. In the graphs, the horizontal axis represents steering angle [deg] and the vertical axis represents steering torque [Nm]. The dashed line graph shows the waveform with existing friction compensation control, while the solid line graph shows the waveform with gain-adjustment-based friction compensation control. According to existing friction compensation control, as mentioned above, to prevent oscillations when the motor's angular velocity ω is near zero, the friction compensation torque (Nm) must change slowly relative to the motor's angular velocity ω. Therefore, when the steering wheel is turned back (refer to the area enclosed by the dashed circle in the diagram), a spike is observed in the steering torque. In contrast, with gain-adjustment-based friction compensation control, no spike is observed, and friction is appropriately reduced.

[0115] According to the second installation example, by further applying gain-adjustment-based friction compensation control to torque control, friction can be appropriately reduced while minimizing high-frequency interference components.

[0116] [Installation Example 3]

[0117] In the third installation example, the controlled object includes a steering wheel 521, universal couplings 523A and 523B, a rotating shaft 524, a torsion bar 546, a motor 543, and a reduction gear 544. The controlled object in the third installation example includes parts that can rotate relative to each other via the torsion bar 546; therefore, the motion of the controlled object cannot be described solely by the equations of motion for a single inertial system. The controlled object in the third installation example varies between a single inertial system and a two-inertial system depending on the strength of the driver's grip on the steering wheel 521. The harder the driver grips the steering wheel 521, the closer the controlled object is to a single inertial system. The lighter the driver grips the steering wheel, the closer the controlled object is to a two-inertial system. In the third installation example, as the output of the controlled object, an angular velocity equivalent to the angular velocity of the reduction gear 544 is input to the model tracking controller.

[0118] In the third installation example, the device model (nominal model) is set as a model with frequency characteristics between inertial system 1 and inertial system 2. The transfer function P of the device model (nominal model) in the third installation example... n (s) The transfer function P of the inverse device model, expressed by mathematical expression 7. n -1 (s) is expressed by the mathematical expression of mathematical expression 8.

[0119] 【Mathematical Expression 7】

[0120]

[0121] 【Mathematical Expression 8】

[0122]

[0123] In mathematical expressions 7 and 8, s is the Laplace transform operator, J STGn B is a parameter representing the moment of inertia of the nominal model. STGn ω is a parameter representing the viscous friction coefficient of the nominal model. 1n It is the transfer function P n The frequency of the zero point of (s), ω 2n It is the transfer function P n The frequency of the poles of (s), ζ 1n It is the transfer function P n The attenuation ratio at the zero point of (s), ζ 2n It is the transfer function P n The attenuation ratio at the pole of (s).

[0124] In the third installation example, the nominal model is a model with frequency characteristics between inertial system 1 and inertial system 2. The transfer function P of the above nominal model is represented by... n The mathematical expression for (s) in equation 7 is obtained by adding a decay term to the expression representing a 2-inertial system. In equation 7, the decay term is 2ζ. 1n ω 1n s and 2ζ 2n ω 2n s. The expression obtained by removing these attenuation terms from the mathematical expression in equation 7 becomes the expression representing the 2-inertial system. In the third installation example, the transfer function P of the nominal model n The number of times (s) is 3.

[0125] In the third installation example, the nominal model is one that considers the mechanical characteristics when the driver (helmsman) operates the steering wheel 521. The harder the driver grips the steering wheel 521, the closer the controlled object is to a 1-inertial system; the lighter the driver grips the steering wheel 521, the closer it is to a 2-inertial system. Therefore, the transfer function P(s) of the controlled object in the third installation example varies between a 1-inertial system and a 2-inertial system depending on how much force is applied from the driver's arm to the steering wheel 521. In the third installation example, by setting the nominal model to have frequency characteristics between a 1-inertial system and a 2-inertial system, even if the state of the controlled object is any state between a 1-inertial system and a 2-inertial system, the transfer function P(s) of the nominal model remains constant. n The modeling error Δ(s) between the transfer function P(s) and the control object will not become too large. Therefore, regardless of how the driver steers the steering wheel 521, the control object can be appropriately controlled using the nominal model. Thus, in the third installation example, the nominal model becomes a model that takes into account the mechanical characteristics of the control object imparted by the driver's grip on the steering wheel 521. The control device 100 in the third installation example, by having such a nominal model as its internal model, is able to perform appropriate control of the control object. The other structures in the third installation example can be the same as those in the other installation examples described above.

[0126] Industrial availability

[0127] The embodiments of the present invention can be applied to control devices for controlling motors of EPS mounted in vehicles.

Claims

1. A control device used in an electric power steering system having a motor, for controlling said motor, wherein, The control device has: A torque controller that operates according to steering torque, providing input to the controlled object of the motor; and A model tracking controller generates a first correction torque based on the output from the controlled object, the first correction torque comprising low-frequency, mid-frequency, and high-frequency components. The model tracking controller has: A low-pass filter that removes the high-frequency components from the first corrected torque; A high-pass filter, which is coupled in series with the low-pass filter, removes the low-frequency component from the first correction torque from which the high-frequency component has been removed by the low-pass filter; A friction compensation calculator, coupled in parallel with the high-pass filter, applies friction compensation to the first corrected torque, which contains only the low-frequency component after removing the high-frequency component and the mid-frequency component output from the high-pass filter, to calculate the inferred value of the friction torque of the machine. as well as An adder that adds the inferred value of the frictional torque to the first corrective torque, which has had its low-frequency components removed by the high-pass filter and its high-frequency components removed by the low-pass filter, thereby generating a second corrective torque. The control device feeds back the second correction torque to the input of the controlled object.

2. The control device according to claim 1, wherein, The high-pass filter has a first cutoff frequency, and the low-pass filter has a second cutoff frequency that is larger than the first cutoff frequency.

3. The control device according to claim 2, wherein, The model tracking controller is configured such that when the transfer functions of the low-pass filter and the high-pass filter are set to Q(s) and HPF(s) respectively, in Q(s)... In the frequency band where the gain is 1 in the gain characteristics of HPF(s), the transfer function of the controlled object is constrained in the nominal model.

4. The control device according to claim 3, wherein, The friction compensation calculator has the following features: A subtractor that subtracts the output value from the high-pass filter from the output value from the low-pass filter; A limiter that imposes a limit on the output value from the subtractor; and A gain adjuster that applies a gain to the output value from the limiter. The adder adds the output value from the gain adjuster to the output value from the high-pass filter.

5. The control device according to claim 4, wherein, The maximum value of the gain of the gain adjuster is determined under the condition that the transfer function of the controlled object is constrained in the nominal model.

6. The control device according to any one of claims 3 to 5, wherein, The first cutoff frequency is above 2Hz and below 10Hz.

7. The control device according to claim 6, wherein, The second cutoff frequency is above 3Hz.

8. The control device according to any one of claims 1 to 5, wherein, When the steering frequency is within the specified range, the torque controller generates the target motor torque by applying phase compensation to the steering torque and inputs it to the controlled object.

9. The control device according to claim 4, wherein, Vehicles equipped with the electric power steering system can drive in a driving mode with an automatic operation mode and a manual operation mode, and the gain of the gain adjuster switches according to the driving mode.

10. A control device used in an electric power steering system having a motor for controlling the motor, wherein, The control device has: A torque controller that operates according to steering torque, providing input to the controlled object of the motor; and A model tracking controller that generates a first correction torque based on the output from the controlled object. The model tracking controller has: A low-pass filter that removes high-frequency components from the first corrected torque; A high-pass filter, which is coupled in series with the low-pass filter, removes low-frequency components from the first correction torque from which high-frequency components have been removed by the low-pass filter; A friction compensation calculator, coupled in parallel with the high-pass filter, applies friction compensation to the first corrected torque to calculate the inferred value of the mechanical friction torque; as well as An adder adds the inferred value of the friction torque to the first corrective torque, which has had its low-frequency components removed by the high-pass filter and its high-frequency components removed by the low-pass filter, thereby generating a second corrective torque. The friction compensation calculator has the following features: A subtractor that subtracts the output value from the high-pass filter from the output value from the low-pass filter; A limiter, located after the subtractor, limits the output value from the subtractor; and A gain adjuster, located after the limiter, applies a gain to the output value from the limiter. The control device feeds back the second correction torque to the input of the controlled object.

11. The control device according to claim 10, wherein, The high-pass filter has a first cutoff frequency, and the low-pass filter has a second cutoff frequency that is larger than the first cutoff frequency.

12. The control device according to claim 11, wherein, The model tracking controller is configured such that when the transfer functions of the low-pass filter and the high-pass filter are set to Q(s) and HPF(s) respectively, in Q(s)... In the frequency band where the gain is 1 in the gain characteristics of HPF(s), the transfer function of the controlled object is constrained in the nominal model.

13. The control device according to claim 12, wherein, The adder adds the output value from the gain adjuster to the output value from the high-pass filter.

14. The control device according to claim 13, wherein, The maximum value of the gain of the gain adjuster is determined under the condition that the transfer function of the controlled object is constrained in the nominal model.

15. The control device according to any one of claims 12 to 14, wherein, The first cutoff frequency is above 2Hz and below 10Hz.

16. The control device according to claim 15, wherein, The second cutoff frequency is above 3Hz.

17. The control device according to any one of claims 10 to 14, wherein, When the steering frequency is within the specified range, the torque controller generates the target motor torque by applying phase compensation to the steering torque and inputs it to the controlled object.

18. The control device according to claim 13, wherein, Vehicles equipped with the electric power steering system can drive in a driving mode with an automatic operation mode and a manual operation mode, and the gain of the gain adjuster switches according to the driving mode.

19. A motor module comprising: Motor; and The control device according to any one of claims 1 to 18.

20. An electric power steering device, wherein, The electric power steering system has the motor module as described in claim 19.

21. A control method for controlling the motor of an electric power steering system having a motor, wherein, The control method includes the following steps: Obtain steering torque; The amount of operation is determined based on the steering torque and input to the controlled object of the motor. A first correction torque comprising low-frequency, mid-frequency, and high-frequency components is generated based on the output from the controlled object; Remove the high-frequency component from the first corrected torque; Remove the low-frequency component from the first corrective torque after removing the high-frequency component; Friction compensation is applied to the first corrected torque, which contains only the low-frequency component after removing the high-frequency and mid-frequency components, to calculate the inferred value of the machine's friction torque; The first corrected torque, after removing both the low-frequency and high-frequency components, is supplemented with the inferred value of the frictional torque to generate the second corrected torque; and The second correction torque is fed back to the input of the controlled object.

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