Control device, electric power steering device, and control method

Abstract

To provide an electric power steering device comprising a control device capable of improving a steering feeling felt by a person steering a vehicle, and a control method.SOLUTION: A control device for controlling, as a control object, a part including at least a motor, comprises: a reaction force control section which controls reaction force; and an assist control section which generates correction torque on the basis of an output of the control object and a nominal model. The assist control section comprises: a high-pass filter with a first cutoff frequency and a low-pass filter with a second cutoff frequency higher than the first cutoff frequency; and a disturbance compensation value calculation section. The assist control section is configured such that, when a transfer function of the low-pass filter is Q(s), and a transfer function of the high-pass filter is HPF(s), a transfer function of the control object is constrained by a transfer function of the nominal model in a frequency band where a gain in a gain characteristic of Q(s)*HPF(s) is 1. The disturbance compensation value calculation section calculates a disturbance compensation value for compensating at least part of self-aligning torque generated in the control object. The correction torque includes the disturbance compensation value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Electric power steering systems mounted on vehicles are known. For example, the electric power steering system described in Patent Document 1 includes a motor control device that includes a disturbance observer for estimating disturbance torque. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-183046 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In electric power steering systems like those described above, there is a need to improve the steering feel perceived by the driver. However, in the control system of an electric power steering system, stability, disturbance suppression characteristics, and responsiveness are all in a trade-off relationship with each other. Therefore, it has been difficult to adjust each element, making it challenging to improve the steering feel perceived by the driver.

[0005] In view of the above circumstances, one of the objectives of the present invention is to provide a control device that can improve the steering feel perceived by the driver, an electric power steering system equipped with such a control device, and a control method that can improve the steering feel perceived by the driver. [Means for solving the problem]

[0006] One aspect of the control device of the present invention is a control device for controlling at least a portion of a steering mechanism comprising an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, the control device comprising: a reaction force control unit that generates an input torque input to the control device based on the torsion bar torque generated in the torsion bar and controls the reaction force transmitted to the helmsman from the steering wheel; and an assist control unit that generates a correction torque to correct the input torque based on the output of the control device and a nominal model. The assist control unit comprises a high-pass filter having a first cutoff frequency, a low-pass filter having a second cutoff frequency higher than the first cutoff frequency, and a disturbance compensation value calculation unit, wherein when the transfer function of the low-pass filter is Q(s) and the transfer function of the high-pass filter is HPF(s), the control device is configured such that the transfer function of the control device is constrained to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1. The disturbance compensation value calculation unit calculates a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object. The corrected torque includes the disturbance compensation value.

[0007] One embodiment of the electric power steering device of the present invention comprises the control device described above and the steering mechanism.

[0008] One aspect of the control method of the present invention is a control method for controlling a steering mechanism comprising an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, wherein at least the portion including the motor is the control target, and the method includes generating an input torque input to the control target based on the torsion bar torque generated in the torsion bar, controlling the reaction force transmitted to the helmsman from the steering wheel, and generating a correction torque to correct the input torque based on the output of the control target and a nominal model. Generating the corrected torque includes, when the transfer function of a high-pass filter having a first cutoff frequency is HPF(s) and the transfer function of a low-pass filter having a second cutoff frequency higher than the first cutoff frequency is Q(s), constraining the transfer function of the controlled object to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1, and calculating a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object. The corrected torque includes the disturbance compensation value. [Effects of the Invention]

[0009] According to one aspect of the present invention, the steering feel experienced by the driver operating the steering wheel of a vehicle equipped with an electric power steering system can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing an electric power steering system according to one embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of a control device according to one embodiment. [Figure 3] Figure 3 is a functional block diagram showing the functions of the processor in a control device according to one embodiment. [Figure 4] Figure 4 is a graph illustrating the gain characteristics of the complementary sensitivity function and the gain characteristics of the reciprocal of the modeling error between the transfer function of the controlled object and the transfer function of the nominal model. [Figure 5] Figure 5 is a graph showing an example of the measurement results for steering angle and torsion torque when model following control is not applied. [Figure 6] Figure 6 is a graph showing an example of the measurement results for steering angle and torsion torque when model following control is applied. [Figure 7] Figure 7 is a graph showing another example of steering angle and torsion torque measurements when model-following control is not applied. [Figure 8] Figure 8 is a graph showing another example of the measurement results for steering angle and torsion torque when model following control is applied. [Figure 9] Figure 9 is a graph showing yet another example of steering angle and torsion torque measurements when model-following control is not applied. [Figure 10] Figure 10 is a graph showing yet another example of the measurement results for steering angle and torsion torque when model following control is applied. [Figure 11] Figure 11 is a graph showing yet another example of the measurement results for steering angle and torsion torque when model-following control is not applied. [Figure 12] Figure 12 is a graph showing yet another example of the measurement results for steering angle and torsion torque when model following control is applied. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the control device, electric power steering device, and control method relating to this disclosure will be described with reference to the attached drawings. However, unnecessarily detailed explanations 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 the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art.

[0012] The following embodiments are illustrative, and the control devices, electric power steering devices, and control methods relating to this disclosure are not limited to these embodiments. For example, the numerical values, steps, and the order of those steps shown in the following embodiments are merely examples, and various modifications are possible as long as they do not create a technical inconsistency. The embodiments or examples described below are merely illustrative, and various combinations are possible as long as they do not create a technical inconsistency.

[0013] The electric power steering system 1000 of this embodiment, shown in Figure 1, is mounted on a vehicle. As shown in Figure 1, the electric power steering system 1000 comprises a steering mechanism 530 and a control device 100. The steering mechanism 530 has a steering mechanism section 520 and an auxiliary mechanism section 540. The electric power steering system 1000 controls the auxiliary mechanism section 540 by the control device 100, thereby generating a steering torque T in the steering mechanism section 520 when the driver operating the vehicle steers the steering wheel 521. h It generates an auxiliary torque to assist the driver. This auxiliary torque reduces the burden on the driver when operating the steering wheel 521. The driver of the vehicle is the helmsman who steers the vehicle's steering wheel 521.

[0014] The steering mechanism 520 includes a steering wheel 521, a steering shaft 522, universal joints 523A, 523B, an input shaft 524a, an output shaft 524b, 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. In other words, the steering mechanism 530 includes a steering wheel 521, a steering shaft 522, universal joints 523A, 523B, an input shaft 524a, an output shaft 524b, 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.

[0015] The steering shaft 522 is a shaft that extends from the steering wheel 521, which is operated by the driver. One end of the input shaft 524a is connected to the end of the steering shaft 522 opposite to the side connected to the steering wheel 521, via universal joints 523A and 523B. Thus, the steering wheel 521 is connected to the input shaft 524a via the universal joints 523A and 523B and the steering shaft 522. The output shaft 524b is connected to the input shaft 524a via a torsion bar 546, which will be described later. More specifically, one end of the output shaft 524b is connected to the other end of the input shaft 524a via the torsion bar 546. The other end of the output shaft 524b is connected to the rack shaft 526 via a rack and pinion mechanism 525.

[0016] The input shaft 524a and the output shaft 524b are arranged coaxially. The input shaft 524a and the output shaft 524b are rotatable around the same central axis. The input shaft 524a and the output shaft 524b are rotatable relative to each other within the range in which the torsion bar 546, described later, can twist.

[0017] The auxiliary mechanism 540 includes a steering torque sensor 541, a steering angle sensor 542, a motor 543, a reduction mechanism 544, an inverter 545, and a torsion bar 546. In other words, the steering mechanism 530 includes a steering torque sensor 541, a steering angle sensor 542, a motor 543, a reduction mechanism 544, an inverter 545, and a torsion bar 546. The torsion bar 546 connects the input shaft 524a and the output shaft 524b. The torsion bar 546 is arranged coaxially with the input shaft 524a and the output shaft 524b. In the following description, the virtual axis passing through the common central axis of the input shaft 524a, the output shaft 524b, and the torsion bar 546 is called the rotation axis R. The torsion bar 546 can twist around the rotation axis R.

[0018] The steering torque sensor 541 detects the amount of twist around the rotation axis R of the torsion bar 546, thereby determining the steering torque T in the steering mechanism 520. hIt detects the steering torque T. h This is the torsion bar torque generated in the torsion bar 546, which is the torsional moment around the rotation axis R. The steering angle sensor 542 can detect the rotation angle θa of the input shaft 524a around the rotation axis R. The rotation angle θa of the input shaft 524a is equal to the steering angle of the steering wheel 521. In other words, the steering angle sensor 542 can detect the steering angle of the steering wheel 521 by detecting the rotation angle θa of the input shaft 524a. Based on the steering torque sensor 541 and the steering angle sensor 542, it is possible to detect the rotation angle θb of the output shaft 524b.

[0019] The inverter 545 converts DC power, which is a pseudo-sine wave of U-phase, V-phase, and W-phase, into three-phase AC power according to the motor drive signal input from the control device 100 and supplies it to the motor 543. The motor 543 is connected to the output shaft 524b via a reduction mechanism 544. The motor 543 is supplied with three-phase AC power from the inverter 545. The motor 543 is, for example, an embedded magnet synchronous motor (IPMSM), a surface magnet synchronous motor (SPMSM), or a switched reluctance motor (SRM). The motor 543, supplied with three-phase AC power from the inverter 545, provides steering torque T h It generates an auxiliary torque corresponding to the current. The motor 543 transmits the generated auxiliary torque to the output shaft 524b via the reduction mechanism 544.

[0020] The control device 100 controls the controlled object 560, which is part of the steering mechanism 530 and includes at least an input shaft 524a, an output shaft 524b, and a motor 543. In this embodiment, the controlled object 560 includes a handle 521, universal joints 523A, 523B, an input shaft 524a, an output shaft 524b, a torsion bar 546, a motor 543, and a reduction mechanism 544. Since the controlled object 560 includes an input shaft 524a and an output shaft 524b that can rotate relative to each other via the torsion bar 546, the motion of the controlled object 560 cannot be described by the equations of motion of a simple one-inertial frame alone. The controlled object 560 changes between a one-inertial frame and a two-inertial frame depending on how hard the helmsman grips the handle 521. The harder the helmsman grips the handle 521, the closer the controlled object 560 becomes to a one-inertial frame. The more lightly the helmsman grips the steering wheel 521, the closer the controlled object 560 becomes to a two-inertial frame of reference.

[0021] The control device 100 is electrically connected to the inverter 545. Based on detection signals detected by the steering torque sensor 541, the steering angle sensor 542, and the vehicle speed sensor 300 mounted on the vehicle, the control device 100 generates a motor drive signal and outputs it to the inverter 545. The control device 100 controls the controlled object 560 by controlling the rotation of the motor 543 via the inverter 545. More specifically, the control device 100 controls the switching operation of multiple switching elements in the inverter 545. Specifically, the control device 100 generates a control signal to control the switching operation of each switching element and outputs it to the inverter 545. Each switching element is, for example, a MOSFET. In the following description, the control signal that controls the switching operation of each switching element will be called a "gate control signal".

[0022] The control device 100 controls the steering torque T hA torque command value is generated based on these factors, and the torque and rotational speed of the motor 543 are controlled, for example, by vector control. Vector control is a method of decomposing the current flowing through the motor 543 into a current component that contributes to torque generation and a current component that contributes to magnetic flux generation, and independently controlling each mutually orthogonal current component. The control device 100 is not limited to vector control and can perform other closed-loop control methods. The rotational speed of the motor 543 is expressed, for example, as the number of rotations of the rotor per minute [rpm] or the number of rotations of the rotor per second [rps].

[0023] Furthermore, the control device 100 receives the steering torque T directly from the steering torque sensor 541. h The value may be input, or the control device 100 may input the steering torque T from the output value of the steering torque sensor 541. h The value of the steering angle may be calculated. The control device 100 may receive the steering angle value of the steering wheel 521 directly from the steering angle sensor 542, or the control device 100 may calculate the steering angle value from the output value of the steering angle sensor 542.

[0024] Furthermore, the control device 100 and the motor 543 are modularized and manufactured and sold as a motor module. The motor module comprises the motor 543 and the control device 100 and is suitably used in an electric power steering system 1000. In addition, the control device 100 can be manufactured and sold independently of the motor 543 as a control device for controlling the electric power steering system 1000.

[0025] Figure 2 shows a typical configuration of the control device 100 in this embodiment. The control device 100 includes, for example, a power supply circuit 111, an angle sensor 112, an input circuit 113, a communication interface 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.

[0026] The vehicle speed sensor 300, steering torque sensor 541, and steering angle sensor 542 mounted on the vehicle are communicated to the processor 200. The vehicle speed is transmitted to the processor 200 from the vehicle speed sensor 300. The steering torque T is transmitted to the processor 200 from the steering torque sensor 541. h The following is transmitted: The steering angle is transmitted to the processor 200 from the steering angle sensor 542.

[0027] The processor 200 is a semiconductor integrated circuit, also known as a central processing unit (CPU) or microprocessor. The processor 200 sequentially executes a computer program stored in the ROM 116, which describes a set of instructions for controlling the motor drive, to achieve the desired processing. In addition to the processor 200, or in place of the processor 200, the control device 100 may have an FPGA (Field Programmable Gate Array) equipped with a CPU, a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an ASSP (Application Specific Standard Product), 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 rotation angle of the motor 543 rotor, generates a PWM (Pulse Width Modulation) signal, and outputs the PWM signal to the drive circuit 115.

[0028] The power supply circuit 111 is connected to an external power supply (not shown). The power supply circuit 111 generates the DC voltage required for each part of the control device 100. The DC voltage generated by the power supply circuit 111 is, for example, 3V or 5V.

[0029] The angle sensor 112 detects the rotation angle of the motor 543's rotor and outputs it to the processor 200. The angle sensor 112 may be a resolver, a Hall element such as a Hall IC, or an MR sensor having a magnetoresistive element. The processor 200 can calculate the angular velocity ω [rad / s] of the motor 543 based on the electrical angle θm of the motor 543 obtained from the angle sensor 112. The control device 100 may also be equipped with a speed sensor capable of detecting the rotational angular velocity of the motor 543 and an acceleration sensor capable of detecting the rotational angular acceleration of the motor 543 instead of the angle sensor 112.

[0030] The input circuit 113 receives the motor current value detected by a current sensor (not shown). In the following description, the motor current value detected by the current sensor (not shown) will be referred to as the "actual current value". The input circuit 113 converts the level of the input actual current value to the input level of the processor 200 as needed, 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.

[0031] Communication I / F114 is an input / output interface for transmitting and receiving data in accordance with, for example, 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 gate control signals according to the PWM signal and applies gate control signals to the gates of the multiple switching elements of the inverter 545. For example, when the motor 543 to be driven is a motor that can be driven at a low voltage, the drive circuit 115 as a gate driver may not be necessary. In that case, the gate driver function of the drive circuit 115 can be implemented in the processor 200.

[0033] ROM116 is electrically connected to processor 200. ROM116 is, for example, writable memory, rewritable memory, or read-only memory. Examples of writable memory include PROM (Programmable Read Only Memory). Examples of rewritable memory include flash memory and EEPROM (Electrically Erasable Programmable Read Only Memory). ROM116 stores a control program containing instructions for processor 200 to control motor drive. For example, the control program stored in ROM116 is temporarily loaded into RAM (not shown) during boot-up.

[0034] Figure 3 shows an example of the functional blocks of the processor 200 in this embodiment. The processor 200, which is a computer, sequentially executes the processing or tasks necessary for controlling the motor 543 using each functional block. Each functional block of the processor 200 shown in Figure 3 may be implemented in the processor 200 as software such as firmware, as hardware, or as both software and hardware. Typically, the processing of each functional block in the processor 200 is described in a computer program in software module units 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 hardware accelerators. Furthermore, the control method of the control device 100 in this embodiment may be implemented by having the computer execute the desired operation.

[0035] The processor 200 includes a reaction force control unit 210, an assist control unit 230, a state feedback unit 280, a subtractor SU1, an adder AD1, and an adder AD2. That is, the control device 100 includes a reaction force control unit 210, an assist control unit 230, a state feedback unit 280, a subtractor SU1, an adder AD1, and an adder AD2. In other words, functions corresponding to the reaction force control unit 210, the assist control unit 230, the state feedback unit 280, the subtractor SU1, the adder AD1, and the adder AD2 are implemented in the processor 200 of the control device 100.

[0036] The reaction force control unit 210 receives the steering torque T detected by the steering torque sensor 541. h The reaction force control unit 210 generates an input torque T input to the control target 560 based on the steering torque T, that is, the torsion bar torque generated in the torsion bar 546. The input torque T is the target torque of the motor 543 and is a torque command value. The reaction force control unit 210 controls the reaction force transmitted from the steering wheel 521 to the driver by generating the input torque T and controlling the torque of the motor 543. The reaction force control unit 210 applies phase compensation to the steering torque T when the steering frequency or the steering speed is within a predetermined range to generate the input torque T. The steering frequency is the frequency of the steering angle that changes based on the operation of the driver's steering wheel 521. The steering speed is the speed of the steering angle that changes based on the operation of the driver's steering wheel 521. The reaction force control unit 210 illustrated in FIG. 3 includes a base assist calculation unit 211 and a phase compensator 212.

[0037] The base assist calculation unit 211 acquires the steering torque T and the vehicle speed. The base assist calculation unit 211 generates a base assist torque based on the steering torque T and the vehicle speed. For example, the base assist calculation unit 211 h and the vehicle speed. The base assist calculation unit 211 generates a base assist torque based on the steering torque T h and the vehicle speed. For example, the base assist calculation unit 211 h ​​​​​​​​​​​​It has a lookup table (LUT) that defines the relationship between vehicle speed and base assist torque. The base assist calculation unit 211 refers to the lookup table and calculates the steering torque T h Based on the vehicle speed, the corresponding base assist torque can be determined. The base assist calculation unit 211 calculates the steering torque T h The base assist gain can be determined based on the slope defined by the ratio of the change in base assist torque to the change in the amount of fluctuation.

[0038] In this embodiment, the phase compensator 212 adjusts the assist gain within the range of steering frequencies that the driver can take when operating the steering wheel 521, and compensates for the rigidity of the torsion bar 546. The range of steering frequencies that can take is, for example, 5 Hz or less. When the steering frequency is 5 Hz or less, the phase compensator 212 adjusts the steering torque T h In other words, a first-order phase compensation may be applied to the torsion bar torque. The first-order phase compensation is represented, for example, by the transfer function of equation (1).

[0039]

number

[0040] In equation (1), s is a Laplace transformer, f1 is the zero frequency [Hz] of the transfer function, and f2 is the pole frequency [Hz] of the transfer function. A graph with gain, or loop gain, on the vertical axis and the logarithm of frequency on the horizontal axis is called a gain diagram. In a gain diagram, the zero point represents the intersection of the gain curve and the horizontal axis representing 0 dB, and the pole represents the maximum point of the gain curve. For example, phase lead compensation can be applied by setting the pole frequency higher than the zero frequency. The larger the distance between the pole frequency and the zero frequency, the greater the phase lead.

[0041] The phase compensator 212 uses the base assist torque and base assist gain output from the base assist calculation unit 211 to determine the input torque T rThis generates a stable phase compensator. For example, the phase compensator 212 is a stabilization compensator, and stabilization phase compensation can be applied to the base assist torque. The phase compensator 212 may have a transfer function of order 2 or higher whose frequency characteristics are variable according to the base assist gain. A transfer function of order 2 or higher is expressed using a responsiveness parameter and a damping ratio parameter. A transfer function of order 2 or higher can be expressed by equation (2), for example. By making the order of the transfer function 2, damping can be applied to the characteristics of the transfer function. By changing the damping, it is possible to adjust the phase characteristics.

[0042]

number

[0043] In equation (2), s is a Laplace transformer, ω1 is the zero frequency of the transfer function, ω2 is the pole frequency of the transfer function, ζ1 is the zero attenuation ratio, and ζ2 is the pole attenuation ratio. The pole frequency ω2 is lower than the zero frequency ω1.

[0044] The assist control unit 230 controls the input torque T r Correction torque T to compensate for f This is generated based on the output of the controlled object 560 and the nominal model. In this embodiment, the corrected torque T f The input torque T r This is the feedback torque that is fed back to the control object 560. The nominal model is an internal model used as a model to constrain the control object 560 when controlling the control object 560. The nominal model will be described in detail later. In this embodiment, the assist control unit 230 is a model following controller configured to perform model following control. The specific configuration of the assist control unit 230 will be described in detail later.

[0045] The subtractor SU1 receives an input torque T r Therefore, the corrected torque T output from the assist control unit 230 fSubtract the value. The output from subtractor SU1 is input to adder AD1 and assist control unit 230. Adder AD1 outputs the value obtained by adding the output from state feedback unit 280 to the output from subtractor SU1 to adder AD2. Adder AD2 adds the disturbance torque T to the output from adder AD1. d The value obtained by adding this value is output to the controlled device 560.

[0046] Disturbance Torque T d This is the difference between the output torque of the ideal motor 543 and the actual output torque of the motor 543. Disturbance torque T d This includes disturbance torques applied externally to the controlled object 560. Disturbance torque T d This includes, for example, excess torque caused by friction and rattle resulting from mechanical elements such as the motor 543 and the reduction mechanism 544, torque ripple in the motor 543, self-aligning torque, and disturbance torque that may occur when driving on unpaved, bumpy or gravel roads. Self-aligning torque refers to the torque that acts in the direction that the steering wheel 521 returns to its original position due to the elasticity of the twisting tires when the steering wheel 521 is turned.

[0047] In this embodiment, the assist control unit 230 calculates the angular velocity ω from the rotation angle θa of the input shaft 524a. θ Based on the corrected torque T f Generates input torque T r Provides feedback to the angular velocity ω. θ This value corresponds to the angular velocity of the motor 543, which is theoretically calculated from the rotation angle θa of the input shaft 524a. For example, immediately after the steering wheel 521 is started to rotate by the helmsman, the input shaft 524a rotates along with the rotation of the steering wheel 521, but the motor 543 has not yet started to drive and the output shaft 524b has not yet rotated. In this case, the actual angular velocity ω of the motor 543 is zero, but theoretically, if the input shaft 524a rotates, the motor 543 will also rotate and the output shaft 524b will also rotate. Angular velocity ω θThis value corresponds to the angular velocity of motor 543 if motor 543 were to rotate in this theoretical manner. Therefore, the angular velocity ω θ The angular velocity ω of motor 543 may differ from the actual angular velocity ω. θ The rotation angle θa used in the calculation may be a value detected by the rudder angle sensor 542, or a value calculated from the rotation angle θb of the output shaft 524b.

[0048] The assist control unit 230 includes an inverse nominal model 231, a low-pass filter 232, a high-pass filter 233, an assist adjustment unit 270, a subtractor SU2, and an adder AD3. The high-pass filter 233 has a first cutoff frequency Cf1. The first cutoff frequency Cf1 is, for example, 2 Hz or more and 10 Hz or less, and preferably 5 Hz or more and 7 Hz or less.

[0049] The low-pass filter 232 has a second cutoff frequency Cf2 that is higher than the first cutoff frequency Cf1. The second cutoff frequency Cf2 is, for example, between 3 Hz and 50 Hz. However, the upper limit of the second cutoff frequency Cf2 may be set to a range of approximately between 140 Hz and 200 Hz. The order of the low-pass filter 232 is third order or higher. The low-pass filter 232 may be composed of, for example, multiple low-pass filters. The low-pass filter 232 and the high-pass filter 233 are connected in series.

[0050] The assist control unit 230, when the transfer function of the low-pass filter 232 is Q(s) and the transfer function of the high-pass filter 233 is HPF(s), determines that in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1, the transfer function P(s) of the controlled object 560 is the transfer function P of a predetermined nominal model. nIt is configured to be constrained to (s). Q(s)·HPF(s) is the complementary sensitivity function T(s) of the inner loop composed of the assist control unit 230. As shown in Figure 4, Q(s)·HPF(s), i.e., the complementary sensitivity function T(s), has a gain of 0 dB, i.e., a gain of 1 in the transfer function, in the frequency band where the frequency f is above the first cutoff frequency Cf1 and below the second cutoff frequency Cf2. Figure 4 shows the absolute value of the complementary sensitivity function T(s). In this specification, "the transfer function of the controlled object is constrained to the transfer function of the nominal model" means, for example, that the controlled object is controlled so that, when looking at the input / output relationship, the transfer function of the controlled object appears to be the transfer function of the nominal model.

[0051] The inverse nominal model 231 is the inverse model of a predetermined nominal model (plant model) used to constrain the controlled object 560. In this embodiment, the transfer function P of the predetermined nominal model is... n (s) is expressed by the following equation (3): Transfer function P of the inverse nominal model 231. n -1 (s) is expressed by the following equation (4).

[0052]

number

[0053]

number

[0054] In equations (3) and (4), s is the Laplace transformer, and J STGn is a parameter that represents the moment of inertia of the nominal model, and B STGn ω is a parameter that represents the viscous friction coefficient of the nominal model. 1n The transfer function P n The frequency of the zero point of (s) is ω 2n The transfer function P n (s) is the frequency of the pole, ζ 1n The transfer function P n(s) is the damping ratio at the zero point, ζ 2n The transfer function P n This is the damping ratio at the pole of (s).

[0055] In this embodiment, the nominal model is a model having frequency characteristics between one inertial frame and two inertial frames. The transfer function P of the above nominal model. n Equation (3) representing (s) is the equation representing the two inertial frames of reference with a damping term added. In equation (3) above, the damping term is 2ζ 1n ω 1n s and 2ζ 2n ω 2n s. Removing these damping terms from equation (3) gives the equation representing the two inertial frames. In this embodiment, the transfer function P of the nominal model n The degree of (s) is 3.

[0056] In this embodiment, the nominal model is a model that takes into account the mechanical characteristics when the helmsman steers the steering wheel 521. As described above, the controlled object 560 approaches the 1st inertial frame as the helmsman grips the steering wheel 521 more tightly, and approaches the 2nd inertial frame as the helmsman grips the steering wheel 521 more loosely. Therefore, the transfer function P(s) of the controlled object 560 changes between the 1st inertial frame and the 2nd inertial frame depending on how force is applied to the steering wheel 521 from the helmsman's arm. In this embodiment, by making the nominal model a model having frequency characteristics between the 1st inertial frame and the 2nd inertial frame, the transfer function P of the nominal model remains constant regardless of whether the state of the controlled object 560 is between the 1st inertial frame and the 2nd inertial frame. n The modeling error Δ(s) between (s) and the transfer function P(s) of the controlled object 560 can be prevented from becoming too large. Therefore, the controlled object 560 can be suitably controlled using the nominal model regardless of how the helmsman steers the steering wheel 521. Thus, in this embodiment, the nominal model is a model that takes into account the mechanical characteristics given to the controlled object 560 by how the helmsman grips the steering wheel 521. The control device 100 can suitably control the controlled object 560 by having such a nominal model as an internal model.

[0057] In this specification, "the nominal model is a model that takes into account the mechanical characteristics when the helmsman steers the steering wheel" means, for example, that the nominal model is a model that can compensate for at least a portion of the effects that are exerted on the controlled object by the mechanical characteristics when the helmsman steers the steering wheel. The nominal model may also be a model that directly incorporates the mechanical characteristics of the helmsman's arm movements.

[0058] As shown in Figure 3, the output of the controlled object 560 is input to the inverse nominal model 231. Specifically, the angular velocity ω calculated from the rotation angle θa of the input shaft 524a is input to the inverse nominal model 231. θ The following is input. The inverse nominal model 231 is obtained by the above equation (4) and the input angular velocity ω θ Torque T based on p It outputs the torque T. In other words, the assist control unit 230 uses the nominal model based on the output of the controlled object 560 to output the torque T. p Calculate the torque T. p This value is equal to the torque input to the nominal model when the output value of the nominal model is the same as the output value of the controlled device 560.

[0059] The subtractor SU2 subtracts the output of subtractor SU1 from the output of the inverse nominal model 231 to obtain the differential torque T. a It generates the corrected torque T. f After the feedback is given, the state compensation value V described later is used. s Input torque T before it is fed back r Torque T p Subtracting from the difference torque T a Generates the differential torque T. a For example, disturbance torque T d This is an estimated value. The differential torque T output from subtractor SU2. aThe differential torque T is filtered in this order by the series-connected low-pass filter 232 and high-pass filter 233 and input to the adder AD3. a This is a state in which frequency components lower than the first cutoff frequency Cf1 and frequency components higher than the second cutoff frequency Cf2 have been removed. In other words, the differential torque T filtered by the low-pass filter 232 and the high-pass filter 233 is removed. a This refers to frequency components T, which are above the first cutoff frequency Cf1 and below the second cutoff frequency Cf2. aM That is the case.

[0060] The assist adjustment unit 270 generates compensation values ​​for friction and disturbances, and adjusts the differential torque T a Adjusts the differential torque T. In this embodiment, the assist adjustment unit 270 adjusts the differential torque T. a Among them, frequency component T aM The assist adjustment unit 270 is coupled in parallel to the high-pass filter 233. The assist adjustment unit 270 includes a friction compensation value calculation unit 250, a disturbance compensation value calculation unit 260, and a subtractor SU3.

[0061] The subtractor SU3 subtracts the output value from the high-pass filter 233 from the output value from the low-pass filter 232. Here, the output value from the low-pass filter 232 is the differential torque T. a This is the value after removing frequency components higher than the second cutoff frequency Cf2. The output value from the high-pass filter 233 is the differential torque T a This is the value from which frequency components higher than the second cutoff frequency Cf2 and frequency components lower than the first cutoff frequency Cf1 have been removed. Therefore, the value output from the subtractor SU3 is the differential torque T a Among these, the frequency component T is lower than the first cutoff frequency Cf1. aL The output of the subtractor SU3 is input to the friction compensation value calculation unit 250 and the disturbance compensation value calculation unit 260. Frequency component T aLIt includes frictional force, self-aligning torque, disturbance torque caused by backlash of the control target 560, torque ripple generated in the control target 560, and the like.

[0062] The friction compensation value calculation unit 250 calculates a friction compensation value V that compensates for at least a part of the frictional force generated in the control target 560. f based on the differential torque T a As described above, the value from the subtracter SU3 input to the friction compensation value calculation unit 250 is the differential torque T a of the frequency component T aL lower than the first cut-off frequency Cf1. Therefore, in the present embodiment, the friction compensation value calculation unit 250 calculates the friction compensation value V a based on the component of the differential torque T f having a frequency lower than the first cut-off frequency Cf1.

[0063] The friction compensation value calculation unit 250 includes a limiter 252 and a gain adjuster 253. The limiter 252 limits the output value from the subtracter SU3. When the input value exceeds the upper or lower threshold value, the limiter 252 clips the input value to the upper or lower threshold value. The gain adjuster 253 multiplies the output value from the limiter 252 by a gain K1. The friction compensation value calculation unit 250 calculates the friction compensation value V a by applying the limitation by the limiter 252 and the gain K1 to the component of the differential torque T f having a frequency lower than the first cut-off frequency Cf1. The threshold value of the limiter 252 and the value of the gain K1 are determined in advance to be appropriate values based on, for example, the frictional force actually generated in the control target 560.

[0064] The correction torque T used for the model following control in the assist control unit 230 fIn order to apply friction compensation, it is necessary to pay attention to the stability conditions of the model following control. This condition is that, from the small gain theorem described later, the gain in the gain characteristics of the transfer function of the friction compensation value calculation unit 250, which is restricted to characteristics considering stability, does not exceed 1. This is derived from the design conditions of the low-pass filter 232. In the present embodiment, the value of the gain K1 in the gain adjuster 253 is set to a maximum of 1, and a subtractor SU3 is provided in front of the limiter 252 to apply a subtraction process so that the gain in the gain characteristics becomes 1 under this condition. In other words, the friction compensation value calculation unit 250 behaves as a low-pass filter having a transfer function of 1-HPF(s).

[0065] The friction compensation value V output from the friction compensation value calculation unit 250 f is a value that compensates for at least a part of the frictional force component included in the differential torque T a in the frequency component T aL of. Generally, since an appropriate amount of friction is required for the control target 560, the friction compensation value calculation unit 250 calculates a value of the friction compensation value V f that is smaller than the frictional force actually generated in the control target 560. Thereby, it becomes possible to realize high-precision friction compensation while leaving an appropriate frictional force in the control target 560. The object of friction compensation by the friction compensation value V f is, for example, the friction of the motor 543, the friction of the speed reduction mechanism 544, and the difference in friction between the left and right of the speed reduction mechanism 544.

[0066] Here, in the frequency component T a of the differential torque T aL in addition to the frictional force component, there are also included a self-aligning torque generated in the control target 560, a disturbance torque caused by backlash generated in the control target 560, and a torque ripple generated in the control target 560. Therefore, the friction compensation value V aL obtained by processing the frequency component T f with the limiter 252 and the gain adjuster 253 also includes a compensation value that compensates for at least a part of the self-aligning torque generated in the control target 560, the disturbance torque caused by backlash generated in the control target 560, and the torque ripple generated in the control target 560.

[0067] A vehicle equipped with an electric power steering system 1000 can be driven according to driving modes that include an automatic driving mode and a manual driving mode. In this case, the gain K1 of the gain adjuster 253 may be switched according to the driving mode. The larger the gain K1 of the gain adjuster 253, the greater the degree of friction reduction. It is preferable that the gain K1 in automatic driving mode is larger than the gain K1 set in manual driving mode. This makes it possible to apply optimal friction compensation to the automatic driving mode, where friction reduction is more important.

[0068] The disturbance compensation value calculation unit 260 calculates a disturbance compensation value V that compensates for at least a portion of the self-aligning torque generated in the controlled object 560. d The disturbance compensation value V is calculated in this embodiment. d This includes a compensation value that compensates for at least a portion of the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560. The disturbance compensation value calculation unit 260 calculates the torque T output from the inverse nominal model 231. p and input torque T r The difference is the differential torque T. a Based on this, the disturbance compensation value V d The disturbance compensation value calculation unit 260 calculates the torque T based on the output of the controlled object 560 using a nominal model. p and input torque T r The difference is the differential torque T. a Based on this, the disturbance compensation value V d The differential torque T is calculated. As described above, the value from the subtractor SU3 input to the disturbance compensation value calculation unit 260 is the differential torque T. a Among these, the frequency component is lower than the first cutoff frequency Cf1. Therefore, in this embodiment, the disturbance compensation value calculation unit 260 calculates the differential torque T a The disturbance compensation value V is based on the component with a frequency lower than the first cutoff frequency Cf1. d Calculate.

[0069] The disturbance compensation value calculation unit 260 includes a limiter 262 and a gain adjuster 263. The limiter 262 limits the output value from the subtractor SU3. If the input value exceeds an upper or lower threshold, the limiter 262 clips the input value to the upper or lower threshold. The threshold of the limiter 262 is different from, for example, the threshold of the limiter 252. The gain adjuster 263 applies a gain K2 to the output value from the limiter 262. The transfer function P(s) of the controlled object 560 is the transfer function P of the nominal model. n The maximum value of the gain K2 of the gain adjuster 263 is determined under the constraint of (s). The value of gain K2 is different from, for example, the value of gain K1. The value of gain K2 is, for example, between 0.3 and 0.8. The gain K2 of the gain adjuster 263 may be switched according to the vehicle's driving mode.

[0070] Disturbance compensation value V d is the differential torque T a The frequency component T aL This value compensates for at least a portion of the self-aligning torque component included in the control. The disturbance compensation value calculation unit 260 calculates, for example, a value equivalent to about half of the self-aligning torque actually generated in the controlled object 560 as the disturbance compensation value V. d The self-aligning torque actually generated in the controlled object 560 is determined experimentally in advance for each frequency, for example. The threshold value and gain K2 of the limiter 262 of the disturbance compensation value calculation unit 260 are set to a value approximately half the magnitude of the self-aligning torque determined in advance, and this is used to calculate the disturbance compensation value V. d The value is adjusted to the value at which the disturbance compensation value V is calculated in the disturbance compensation value calculation unit 260. d This is the friction compensation value V calculated in the friction compensation value calculation unit 250. f This is a different value.

[0071] Here, the differential torque T a The frequency component T aLIn addition to the self-aligning torque, this also includes the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560. Therefore, the frequency component T aL The disturbance compensation value V obtained by processing with limiter 262 and gain adjuster 263 is obtained. d This also includes compensation values ​​that compensate for at least a portion of the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560.

[0072] The adder AD3 adds the output value from the assist adjustment unit 270 to the output value from the high-pass filter 233. In other words, the adder AD3 adds the frequency component T aM Friction compensation value V f and disturbance compensation value V d Add and . Adder AD3 outputs the frequency component T aM and friction compensation value V f and disturbance compensation value V d The corrected torque T is calculated by adding these together. f The following is output. Correction torque T is output from adder AD3. f This is the input to the controlled object 560, i.e., the input torque T. r This is fed back to the assist control unit 230. In this embodiment, the assist control unit 230 receives the differential torque T from which frequency components lower than the first cutoff frequency Cf1 have been removed by the high-pass filter 233. a , that is, frequency component T aM For this, the friction compensation value V f and disturbance compensation value V d Adding these together, the corrected torque T f Generates.

[0073] The state feedback unit 280 determines the apparent transfer function of the controlled object 560 based on the output of the controlled object 560, and the transfer function P of the nominal model. n (s) should be approached, state compensation value V s Input torque T rFeedback is provided to the control target 560. The apparent transfer function of the control target 560 is, for example, the transfer function of a single part when the part located inside the feedback loop created by the assist control unit 230 is considered as a single part. Specifically, in this embodiment, the apparent transfer function of the control target 560 is the transfer function of the entire part from the subtractor SU1 to the output of the control target 560, and is the transfer function of the combined part of the state feedback unit 280 and the control target 560. In this embodiment, the state feedback unit 280 is the corrected torque T f The input torque T after correction and before being input to the controlled object 560. r For this, the state compensation value V s Provide feedback.

[0074] State compensation value V s This includes a compensation value that compensates for at least a portion of the inertial force, viscous force, and frictional force acting on the controlled object 560. More specifically, the state compensation value V s This includes a compensation value that compensates for at least a portion of the inertial force, viscous force, and frictional force generated in the motor 543. In this embodiment, the state compensation value V s This is a compensation value that includes the inertial force, viscous force, and frictional force acting on the motor 543, respectively.

[0075] The state feedback unit 280 includes an inertia compensator 281, a viscosity compensator 282, and a friction compensator 283. The inertia compensator 281 calculates a compensation value that compensates for at least a portion of the inertial force acting on the motor 543 based on the angular velocity ω of the motor 543. The viscosity compensator 282 calculates a compensation value that compensates for at least a portion of the viscous force acting on the motor 543 based on the angular velocity ω of the motor 543. The friction compensator 283 calculates a compensation value that compensates for at least a portion of the frictional force acting on the motor 543 based on the angular velocity ω of the motor 543. In this embodiment, the state compensation value V sThis consists of a compensation value calculated by the inertia compensator 281, a compensation value calculated by the viscosity compensator 282, and a compensation value calculated by the friction compensator 283. The compensation value calculated by the inertia compensator 281, the compensation value calculated by the viscosity compensator 282, and the compensation value calculated by the friction compensator 283 are output to the adder AD1, and the corrected torque T f Input torque T after correction r It will be added to.

[0076] Next, the control by the assist control unit 230 will be explained in more detail. The assist control unit 230 controls the controlled object 560 using the inverse model of the nominal model it has as an internal model, i.e., the inverse nominal model 231. In this embodiment, the feedback loop created by the assist control unit 230 makes it possible to compensate for torque ripple and other factors that depend on the angular velocity ω of the motor 543. The angular velocity ω signal used for control can be corrected for each type of motor 543, and the accuracy of the angular velocity ω signal can be improved compared to current signals, etc. As a result, it becomes possible to apply highly accurate torque ripple compensation to torque control.

[0077] The assist control unit 230 is structurally similar to a conventional disturbance estimator (disturbance observer), but its intended function and effect are different. Conventional disturbance estimators estimate disturbance torque by using an inverse plant model, which is an internal model, that is close to the controlled object 560, and reduce the effect of disturbances by adding or subtracting the disturbance torque in advance.

[0078] In this embodiment, the control by the assist control unit 230 is performed by a feedback loop, in which the transfer function P(s) of the controlled object 560 is determined by the transfer function P of the nominal model which has an internal model. nThe effect of being constrained by (s) is utilized. For example, if the nominal model is defined so that there is no torque ripple, the transfer function P(s) of the controlled object 560 is constrained to the characteristic of having no torque ripple by model following control, and as a result, torque ripple can be reduced by applying torque ripple compensation. Alternatively, by making the nominal model a low-inertia model and constraining the controlled object 560 with the nominal model, the controlled object 560 can be treated as a low-inertia model. Alternatively, by making the nominal model a low-viscosity model and constraining the controlled object 560 with the nominal model, the controlled object 560 can be treated as a low-viscosity model. By executing model following control by the assist control unit 230, in addition to torque ripple compensation for the motor 543, for example, lost torque compensation or motor inertia compensation is performed. In the above equations (3) and (4), J STGn and B STGn By appropriately setting this, the desired frequency characteristics can be imparted to the transfer function P(s) of the controlled object 560.

[0079] Transfer function P(s) of the controlled object 560 and the transfer function P of the nominal model n When the modeling error with (s) is denoted as Δ(s), the transfer function P(s) of the controlled object 560 is expressed by the following equation (5).

[0080]

number

[0081] The gain characteristics of the transfer function P(s) of the controlled object 560 have peaks at two frequency values, for example. The modeling error Δ(s) appears, for example, near the higher frequency peak of the two peaks in the gain characteristics of the controlled object 560. Therefore, as shown in Figure 4, the reciprocal of the modeling error Δ(s), 1 / Δ(s), has a bottom in the relatively high-frequency region. In Figure 4, the modeling error Δ(s) is shown as an absolute value. As the modeling error Δ(s) increases, the transfer function P(s) of the controlled object 560 and the transfer function P of the nominal model nThe deviation from (s) becomes large, and the control of the controlled object 560 using the nominal model by the assist control unit 230 becomes unstable. Therefore, in the region where the modeling error Δ(s) is relatively small, the gain of the complementary sensitivity function T(s), i.e., Q(s)·HPF(s), is set to 1, and the controlled object 560 is constrained to the nominal model, thereby enabling stable and suitable control of the controlled object 560. The frequency characteristics of the modeling error Δ(s) are the transfer function P of the nominal model. n (s) J STGn and B STGn This can be adjusted by adjusting the following: The frequency band in which the gain of Q(s)·HPF(s) is 1 can be adjusted by adjusting the first cutoff frequency Cf1 and the second cutoff frequency Cf2. This allows adjustment so that the gain of Q(s)·HPF(s) is 1 in the frequency band in which the modeling error Δ(s) is small.

[0082] In Figure 4, 1 / Δ(s) is relatively high in the frequency band below the second cutoff frequency Cf2, and decreases sharply in the frequency band above the second cutoff frequency Cf2. Model-following control, which constrains the controlled object 560 to the nominal model, can be performed stably, for example, in the range where 1 / Δ(s) is greater than 1, i.e., greater than 0 dB. Therefore, as shown in Figure 4, by adjusting 1 / Δ(s) to be greater than 1 in the frequency band where the gain of Q(s)·HPF(s) is 1, the controlled object 560 can be stably and suitably controlled by constraining it to the nominal model when the gain of Q(s)·HPF(s) is 1.

[0083] For example, in order to broaden the frequency band over which the controlled object 560 can be stably and suitably controlled while constrained to the nominal model, the second cutoff frequency Cf2 should be increased within the range where 1 / Δ(s) is not less than 1, that is, within the frequency band lower than the frequency at which the curve representing 1 / Δ(s) in Figure 4 intersects with the horizontal axis. However, if the second cutoff frequency Cf2 is increased too much, the gain of Q(s)·HPF(s) may remain relatively high in the frequency band above the second cutoff frequency Cf2, even though 1 / Δ(s) has decreased, which may lead to unstable control. In contrast, in this embodiment, since the order of the low-pass filter 232 is set to the third order or higher, the gain of Q(s)·HPF(s) can be sharply reduced in the region where the frequency is higher than the second cutoff frequency Cf2. This allows the gain of Q(s)·HPF(s) to be quickly reduced in frequency bands higher than the second cutoff frequency Cf2, even when the second cutoff frequency Cf2 is set relatively high, thereby suppressing instability in the control of the controlled device 560.

[0084] The robust stability of the assist control unit 230 is guaranteed when the small gain theorem shown in equation (6) below holds between the complementary sensitivity function T(s) and the modeling error Δ(s).

[0085]

number

[0086] As described above, in order to perform model-following control using the nominal model in the assist control unit 230, T(s) = 1 is sufficient. However, considering robust stability, it is necessary to satisfy equation (6) above. As can be understood from this, it is not possible to satisfy both T(s) = 1 and equation (6) in all frequency bands, and thus the suppression of disturbances by the assist control unit 230 and robust stability are incompatible.

[0087] As shown in Figure 4, even in the region where the frequency is lower than the first cutoff frequency Cf1, the gain of Q(s)·HPF(s), i.e., the gain of the complementary sensitivity function T(s), becomes less than 1. In the region where the gain of Q(s)·HPF(s) becomes less than 1, the input torque T in the reaction force control unit 210 r The controlled object 560 is controlled by performing this control. As described above, in the region where the frequency is higher than the second cutoff frequency Cf2, the gain of Q(s)·HPF(s) is greatly reduced, and the corrected torque T from the assist control unit 230 is reduced. f This results in a state where there is almost no feedback to the input of the controlled device 560. On the other hand, in the region where the frequency is lower than the first cutoff frequency Cf1, the gain of Q(s)·HPF(s) is set to a certain magnitude, and the corrected torque T f This is fed back to the input of the controlled device 560. In the region where the frequency is lower than the first cutoff frequency Cf1, the compensation value generated in the assist adjustment unit 270 described above is fed back to the input of the controlled device 560 according to the gain of Q(s)·HPF(s).

[0088] The control device 100 stabilizes steering by performing torque control in the reaction force control unit 210 for low-frequency torque signals lower than the first cutoff frequency Cf1, and by performing control so that the angular velocity ω ≈ 0 for high-frequency disturbances higher than the second cutoff frequency Cf2, thereby preventing the steering wheel 521 from being pulled. To achieve this objective, the control device 100 uses the reaction force control unit 210 to reduce the high-frequency gain of the torque control, and uses the assist control unit 230 to constrain the transfer function P(s) of the controlled object 560 to a characteristic where the high-frequency gain decreases. The reason for the latter processing is to prevent the controlled object 560 from reacting to disturbances when they are input to it.

[0089] The effective range of the model following control by the assist control unit 230 is the region between the first cutoff frequency Cf1 and the second cutoff frequency Cf2. In other words, the lower frequency limit of the effective range of the model following control depends on the first cutoff frequency Cf1. Therefore, the lower frequency limit of the effective range of the model following control is determined by adjusting the first cutoff frequency Cf1 of the high-pass filter 233 so as not to interfere with the control of the reaction force control unit 210 in the low-frequency region.

[0090] According to this embodiment, the input torque T r Correction torque T to compensate for f The assist control unit 230, which generates based on the output of the controlled object 560 and the nominal model, ensures that in the frequency band where the gain in the gain characteristic of the complementary sensitivity function T(s) with respect to the modeling error Δ(s) between the controlled object 560 and the nominal model is 1, the transfer function P(s) of the controlled object 560 is equal to the transfer function P of the nominal model. n It is configured to be constrained by (s). Specifically, in the region where the modeling error Δ(s) between the nominal model and the controlled object 560 is small, the gain in the gain characteristic of Q(s)·HPF(s) is set to 1, and the difference in output between the controlled object 560 and the nominal model is corrected to a torque T f Input torque T r By providing feedback, the transfer function P(s) of the controlled object 560 appears to be the transfer function P of the nominal model. n It can be brought closer to (s). For example, by setting the nominal model to a model in which no torque ripple occurs, torque ripple can be removed or reduced from the output of the controlled object 560 in the frequency band where the gain in the gain characteristic of Q(s)·HPF(s) is 1. Also, by setting the nominal model to a low-inertia and low-viscosity model, the controlled object 560 can be constrained to a low-inertia and low-viscosity model, making it easier to control the controlled object 560.

[0091] For example, conventional disturbance estimators had an internal model that closely resembled the controlled object 560, and compensated for disturbances occurring in the controlled object 560. However, it is difficult to have an internal model that is exactly the same as the controlled object 560, and a modeling error Δ(s) inevitably occurs. Therefore, in conventional disturbance estimators, in order to suppress the instability of the control, the gain in the gain characteristic of Q(s)·HPF(s) was set to a value less than 1 in all frequency bands. Furthermore, because conventional disturbance estimators only aimed to make the internal model as close as possible to the actual model of the controlled object 560, they could estimate disturbances applied to the controlled object 560 from the outside, but could not eliminate torque ripple and other disturbances occurring in the controlled object 560 itself.

[0092] In contrast, in this embodiment, the nominal model that the control device 100 has as an internal model is set not as a model that attempts to reproduce the actual model of the controlled object 560, but as an ideal model for the controlled object 560, and the gain of Q(s)·HPF(s) is set to 1 in the region where the modeling error Δ(s) is small. As a result, by suitably setting the nominal model, not only disturbances applied to the actual controlled object 560 from the outside, but also torque ripples that occur internally in the controlled object 560 can be eliminated. Therefore, according to this embodiment, the control device 100 can suitably control the controlled object 560, and the steering feel perceived by the helmsman can be improved.

[0093] Furthermore, for example, the steering mechanism 530 has a structure in which the input shaft 524a and the output shaft 524b are connected with a torsion bar 546 in between, and is not a simple single inertial system. Therefore, if the object controlled by the control device 100 is considered as a single inertial system including only the motor 543, it may be difficult to adequately guarantee against torque ripple and disturbances. In contrast, as in this embodiment, it is conceivable to consider the portion including both sides of the torsion bar 546 as the controlled object 560, but it is not the case that the controlled object 560 can be considered as a simple two-inertial system. As described above, the controlled object 560 changes between a single inertial system and a two-inertial system depending on how the helmsman steers the steering wheel 521. Therefore, even if the controlled object 560 is simply modeled as a two-inertial system, it may be difficult to adequately guarantee against torque ripple and disturbances.

[0094] In contrast, according to this embodiment, the nominal model is a model that takes into account the mechanical characteristics when the helmsman steers the steering wheel 521. Therefore, the nominal model can be suitably matched to the characteristics of the controlled object 560, which change according to how the helmsman steers the steering wheel 521. As a result, by constraining the controlled object 560 to the nominal model through the model-following control described above, torque ripple and disturbances can be more suitably compensated for. Consequently, the steering feel perceived by the helmsman can be further improved.

[0095] Furthermore, according to this embodiment, the transfer function P of the nominal model n The order of (s) is 3 or greater. Here, the inventors have revealed that the order of the transfer function of the steering mechanism 530 is, for example, 6. Therefore, the transfer function P of the nominal model n By making (s) a higher-order transfer function closer to the order of the transfer function of the steering mechanism 530, the control device 100 can more effectively control the steering mechanism 530. Therefore, the steering feel perceived by the driver can be further improved.

[0096] In this embodiment, the controlled object is considered within the range of a third-order transfer function, and the transfer function P of the nominal model is used. nThe order of (s) was also set to 3. However, for example, if the controlled object is considered within the range of transfer functions of order 4 or higher, the transfer function P of the nominal model can be considered. n The order of (s) may be 4 or higher. The order of the transfer function within the range considered as the controlled object and the transfer function P of the nominal model. n The closer the order of (s) is to the 6th order, which is the order of the transfer function of the steering mechanism 530, the more suitable the control can be. For example, if the steering torque sensor 541 is a resolver, the transfer function of the steering torque sensor 541 may be of order 2. Therefore, for example, if the controlled object is the controlled object 560 of this embodiment plus the steering torque sensor 541, the nominal model transfer function P n If the order of (s) is set to the fifth order, more suitable control can be achieved.

[0097] Furthermore, according to this embodiment, the nominal model is a model having frequency characteristics between one inertial frame and two inertial frames. As described above, the characteristics of the controlled object 560 change between one inertial frame and two inertial frames depending on how the helmsman steers the steering wheel 521. Therefore, by making the nominal model a model having frequency characteristics between one inertial frame and two inertial frames, the controlled object 560 can be controlled more effectively using the nominal model. Consequently, the steering feel perceived by the helmsman can be further improved.

[0098] Furthermore, according to this embodiment, the transfer function P of the nominal model n The equation representing (s) is the equation representing the two inertial frames of reference with a damping term added. Therefore, the transfer function P of the nominal model. n (s) can be suitably and easily converted into a model having frequency characteristics between one inertial frame and two inertial frames.

[0099] Furthermore, according to this embodiment, the transfer function P of the nominal model n (s) is expressed by equation (3) above. Therefore, the transfer function P of the nominal model is n (s) can be more preferably and easily converted into a model having frequency characteristics between one inertial frame and two inertial frames.

[0100] As explained above, by considering the controlled object 560 more broadly than a single inertial frame and setting the nominal model to match the controlled object 560, it becomes possible to compensate for disturbances, including torque ripples with a wider frequency band than before, through feedback control using the nominal model. This makes it possible to widen the frequency band in which disturbances can be suppressed compared to before. Specifically, for example, torque ripples occurring in the controlled object 560 include torque ripples caused by the worm gear used in the reduction mechanism 544. Such torque ripples caused by the worm gear may be disturbances of about 50 Hz. With the configuration of conventional disturbance estimators, it was not possible to suppress torque ripples in the first place, and the frequency band in which disturbances could be suppressed was lower than 50 Hz, so torque ripples caused by the worm gear as described above could not be suppressed. In contrast, with the configuration and method of this embodiment, by appropriately setting the nominal model, it becomes possible for the assist control unit 230 to compensate for relatively high-frequency torque ripples caused by the worm gear as described above, and it becomes possible to suppress such relatively high-frequency torque ripples.

[0101] Furthermore, according to this embodiment, the control device 100 determines the apparent transfer function of the controlled object 560 based on the output of the controlled object 560, and the transfer function P of the nominal model. n (s) should be approached, state compensation value V s Input torque T r It is equipped with a state feedback unit 280 that provides feedback to the state. Therefore, the control target 560 to be controlled by the feedback from the assist control unit 230 can appear to be closer to the nominal model it has as an internal model. As a result, when performing model following control by the assist control unit 230, the control target 560 can be considered as a model close to the nominal model, and the modeling error Δ(s) between the control target 560 and the nominal model can be reduced. Therefore, with the gain in the gain characteristic of Q(s)·HPF(s) set to 1, the transfer function P(s) of the control target 560 is equal to the transfer function P of the nominal model. nThe frequency band that can be constrained to (s) can be widened. As a result, model following control by the assist control unit 230 can be performed in a wider frequency band, and the steering feel perceived by the driver can be further improved.

[0102] Furthermore, according to this embodiment, the state feedback unit 280 corrects the torque T f The input torque T after correction and before being input to the controlled object 560. r For this, the state compensation value V s This provides feedback. Therefore, the feedback from the state feedback unit 280 can be placed within the feedback loop of the assist control unit 230. As a result, from the perspective of the assist control unit 230, the state feedback unit 280 and the controlled object 560 can be considered together as a single controlled object. Consequently, by considering the transfer function of this combined single controlled object as the apparent transfer function P(s) of the controlled object 560, control by the assist control unit 230 using the nominal model can be performed more favorably.

[0103] Furthermore, according to this embodiment, the state compensation value V s This includes compensation values ​​that compensate for at least a portion of the inertial force, viscous force, and frictional force acting on the controlled object 560. Therefore, the apparent transfer function of the controlled object 560 is the transfer function P of the nominal model. n (s) can be brought closer to this. In this embodiment, the inertia compensator 281, the viscosity compensator 282, and the friction compensator 283 provide a state compensation value V that includes the inertial force, viscosity force, and friction force, respectively. s By feeding this back, the apparent transfer function of the controlled object 560 is changed to the transfer function P of the nominal model. n (s) can be brought more favorably closer. The gains in the inertia compensator 281, the viscosity compensator 282, and the friction compensator 283 are set appropriately to values ​​that bring the controlled object 560 closer to the nominal model.

[0104] Furthermore, according to this embodiment, the state compensation value Vs This includes compensation values ​​that compensate for at least a portion of the inertial force, viscous force, and frictional force acting on the motor 543. Therefore, the inertial force and other forces acting on the motor 543 can be compensated to approximate the nominal model. This makes the apparent transfer function of the controlled object 560 closer to the transfer function P of the nominal model. n (s) can be brought more favorably closer.

[0105] Furthermore, according to this embodiment, the assist control unit 230 calculates the torque T based on the output of the controlled object 560 using a nominal model. p And, corrected torque T f The state compensation value V after correction by s Input torque T before it is fed back r Based on the difference, corrected torque T f This generates the state compensation value V for the subtractor SU2 of the assist control unit 230. s Input torque T before it is added r This allows input. Therefore, from the perspective of the assist control unit 230, the state feedback unit 280 and the controlled object 560 can be more preferably considered as a single controlled object. This makes it possible to more preferably bring the apparent transfer function P(S) of the controlled object 560 as seen from the assist control unit 230 closer to the nominal model.

[0106] Furthermore, for example, in a two-inertial frame, it is difficult to estimate the motion of the entire two-inertial frame from the motion of the output-side inertial frame. In other words, even in this embodiment, it is difficult to estimate the motion of the nominal model between the first and second inertial frames from only the information of the rotation angle θb of the output shaft 524b, and the torque T output from the inverse nominal model 231 is difficult to estimate from the information of the rotation angle θb of the output shaft 524b. p In some cases, it can be difficult to calculate this appropriately. In contrast, according to this embodiment, the assist control unit 230 corrects the torque T based on the rotation angle θa of the input shaft 524a. fThis generates the following. Therefore, by using the rotation angle θa of the input axis 524a, which is the input side, the motion of the nominal model between the first inertial frame and the second inertial frame can be suitably estimated. As a result, the torque T output from the inverse nominal model 231 is generated. p This allows for the appropriate calculation of the corrected torque T. f This allows for the optimal production of [the desired product].

[0107] Furthermore, the self-aligning torque is transmitted to the helmsman as feedback when the helmsman steers the steering wheel 521. For this reason, for example, in the low-frequency region where the self-aligning torque is present, it is conceivable to significantly reduce the gain of the assist control unit 230 so that the self-aligning torque is not compensated for. In this case, since no compensation is provided by the assist control unit 230, the reaction force control unit 210 applies compensation to control the controlled object 560. However, in this case, the amount of compensation in the reaction force control unit 210 becomes large, and the gain of the reaction force control unit 210 may become too large. As a result, there is a risk that the control by the control device 100 may become unstable.

[0108] In contrast, according to this embodiment, the assist control unit 230 compensates for at least a portion of the self-aligning torque generated in the controlled object 560 by a disturbance compensation value V d It has a disturbance compensation value calculation unit 260 that calculates the corrected torque T. f V is the disturbance compensation value. dThis includes the following. Therefore, even in the low-frequency region that includes self-aligning torque, the assist control unit 230 can compensate at least by the amount that compensates for the self-aligning torque. This reduces the amount of compensation that needs to be compensated by the reaction force control unit 210, and reduces the gain in the reaction force control unit 210. Therefore, it is possible to suppress instability in the control by the control device 100. Therefore, the steering feel felt by the driver can be further improved. In addition, by compensating at least a portion of the self-aligning torque with the assist control unit 230, the reaction force applied to the driver when steering the steering wheel 521 can be reduced. Therefore, the steering feel felt by the driver can be further improved. In particular, in this embodiment, by compensating only a portion of the self-aligning torque with the assist control unit 230, it is possible to make it easier for the driver to steer the steering wheel 521 while giving the driver an appropriate amount of resistance when steering the steering wheel 521.

[0109] Furthermore, according to this embodiment, the disturbance compensation value V d This includes a compensation value that compensates for at least a portion of the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560. Therefore, the disturbance compensation value V calculated in the disturbance compensation value calculation unit 260 of the assist control unit 230 is d This allows for compensation not only of the self-aligning torque, but also of frictional force, disturbance torque due to play, and at least a portion of the torque ripple. As a result, at least a portion of frictional force, disturbance torque due to play, and torque ripple can be compensated even in the low-frequency region below the first cutoff frequency Cf1 where model following control is not possible. Therefore, the steering feel perceived by the driver can be further improved in the low-frequency region below the first cutoff frequency Cf1.

[0110] Furthermore, according to this embodiment, the disturbance compensation value calculation unit 260 calculates the torque T based on the output of the controlled object 560 using a nominal model. p and input torque T r The difference is the differential torque T.a Based on this, the disturbance compensation value V d The differential torque T is calculated. a From this, values ​​such as self-aligning torque can be suitably estimated, and disturbance compensation value V d This allows for the appropriate calculation of the result.

[0111] Furthermore, according to this embodiment, the disturbance compensation value calculation unit 260 calculates the differential torque T a Among these, the component with a frequency lower than the first cutoff frequency Cf1, i.e., frequency component T aL Based on this, the disturbance compensation value V d The self-aligning torque is calculated using relatively low frequency components T. aL Because it is included in the frequency component T aL Based on this, the disturbance compensation value V d By calculating the frequency component T, the self-aligning torque can be appropriately compensated. aL This includes the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560. Therefore, the frequency component T aL The disturbance compensation value V is obtained by processing with limiter 262 and gain adjuster 263. d By calculating this disturbance compensation value V, it is possible to compensate not only for the self-aligning torque, but also for the frictional force generated in the controlled object 560, the disturbance torque caused by the play in the controlled object 560, and the torque ripple generated in the controlled object 560. d It can be calculated.

[0112] Furthermore, according to this embodiment, the assist control unit 230 compensates for at least a portion of the frictional force generated in the controlled object 560 with a friction compensation value V f The difference torque T a It has a friction compensation value calculation unit 250 that calculates based on the following. The assist control unit 230 detects frequency components T lower than the first cutoff frequency Cf1 by the high-pass filter 233. aL The difference torque T after removal a , that is, frequency component T aM For this, the friction compensation value V f and disturbance compensation value Vd Adding these together, the corrected torque T f This generates the friction force generated in the controlled object 560, which can be more effectively compensated by the assist control unit 230.

[0113] Furthermore, according to this embodiment, the friction compensation value calculation unit 250 calculates the differential torque T a Among these, the component with a frequency lower than the first cutoff frequency Cf1, i.e., frequency component T aL Based on the friction compensation value V f This calculates the friction force. As a result, frictional force can be suitably compensated even in the low-frequency region lower than the first cutoff frequency Cf1, where model following control is not possible. This allows the gain of the reaction force control unit 210 to be further reduced in the low-frequency region lower than the first cutoff frequency Cf1, thereby further suppressing instability in the control of the controlled object 560.

[0114] Furthermore, in conventional friction compensation control, when the angular velocity ω of the motor 543 is near zero, the change in the friction compensation value with respect to the angular velocity ω of the motor 543 must be slowed down in order to prevent chattering. As a result, high-precision friction compensation control was sometimes not possible. According to the inventor's research, in order to solve this problem, it is desirable to sequentially estimate and compensate for friction. With the friction compensation by the friction compensation value calculation unit 250 of this embodiment, the friction is sequentially estimated and the friction compensation value V f Since it can be calculated, this problem can be solved.

[0115] Furthermore, auxiliary devices have been developed that recognize lane markings such as white or yellow lines when driving on a highway, for example, and assist in the automatic driving of the vehicle by following the lane. In vehicles equipped with such auxiliary devices and electric power steering devices, it is known that if there is a difference in friction between the left and right sides of the reduction mechanism 544, it may affect the control of the auxiliary device that drives the vehicle straight along the center of the lane. With the friction compensation by the friction compensation value calculation unit 250 of this embodiment, even if there is a difference in friction between the left and right sides of the reduction mechanism 544, the friction can be estimated sequentially, thus solving the above problem. The angular velocity ω of the motor 543, which is the output of the controlled object 560, includes information regarding the difference in friction between the left and right sides of the reduction mechanism 544.

[0116] The inventors confirmed the effects obtained by applying model-following control using the control device 100 of the above-described embodiment by conducting measurements on an actual vehicle. In the actual vehicle measurements, torque ripple, viscosity, friction, and inertia were compared with and without model-following control.

[0117] Figures 5, 7, 9, and 11 show the measurement results of steering angle [deg] and torsion torque [Nm] when model following control is not applied. Figures 6, 8, 10, and 12 show the measurement results of steering angle [deg] and torsion torque [Nm] when model following control is applied. In the graphs from Figures 5 to 12, the horizontal axis is steering angle [deg] and the vertical axis is torsion torque [Nm]. Torsion torque is the torsion bar torque, and steering torque T h That is the case.

[0118] Figures 5 and 6 show the waveforms when the steering wheel 521 is steered at 90 [deg / s]. Looking at the enlarged views of Figures 5 and 6, it can be confirmed that the torque ripple is reduced in the waveform in Figure 6, where model following control is applied, compared to the waveform in Figure 5, where model following control is not applied. This confirms that applying model following control can reduce torque ripple when steering the steering wheel 521.

[0119] Figures 7 and 8 show the waveforms when the steering wheel 521 is steered at a steering frequency of 2 Hz. From Figures 7 and 8, it can be confirmed that the torsion torque fluctuation D1em in the waveform EM1 of Figure 8, to which model following control is applied, is smaller than the torsion torque fluctuation D1ce in the waveform CE1 of Figure 7, to which model following control is not applied. This confirms that applying model following control can reduce the viscous feeling when steering the steering wheel 521.

[0120] Figures 9 and 10 show the waveforms when the steering wheel 521 is steered at a steering frequency of 0.5 Hz within ±10 degrees. From Figures 9 and 10, it can be confirmed that the width D2em, indicated by the arrow in the waveform EM2 of Figure 10, to which model following control is applied, is smaller than the width D2ce, indicated by the arrow in the waveform CE2 of Figure 9, to which model following control is not applied. The widths D2ce and D2em correspond to the magnitude of friction, respectively. Therefore, it has been confirmed that friction when steering the steering wheel 521 can be reduced by applying model following control.

[0121] Figures 11 and 12 show the waveforms when steering the steering wheel 521 in a reverse direction with a steering frequency of 2 Hz. In Figure 11, the dashed ellipse Ece shows the waveform portion when the steering wheel 521 is reversed. In Figure 12, the dashed ellipse Eem shows the waveform portion when the steering wheel 521 is reversed. From Figures 11 and 12, it was confirmed that the inertial hesitation during the reverse direction in the waveform EM3 in Figure 12, to which model following control is applied, is smaller than the inertial hesitation during the reverse direction in the waveform CE3 in Figure 11, to which model following control is not applied. This confirms that applying model following control can reduce the feeling of inertia when steering the steering wheel 521.

[0122] The present invention is not limited to the embodiments described above, and other configurations and methods can be adopted within the scope of the technical idea of ​​the present invention. In the embodiments described above, the assist control unit was configured such that the transfer function of the controlled object is constrained to the transfer function of the nominal model in a frequency band where the gain in the gain characteristics of the complementary sensitivity function for the modeling error between the controlled object and the nominal model is 1, but the invention is not limited to this. The assist control unit only needs to be configured such that the transfer function of the controlled object is constrained to the transfer function of the nominal model in a frequency band where the gain in the gain characteristics of the complementary sensitivity function for the modeling error between the controlled object and the nominal model is approximately 1. "Approximately 1 gain" includes not only the case where the gain is 1, but also, for example, the case where the gain is 0.8 or more and 1.2 or less. This numerical range is, for example, the range in which the gain of the effective disturbance suppression characteristic can be adjusted to 1, taking into account the positive and negative efficiency of the worm gear, when the reduction mechanism connected to the motor has a worm gear. Since the efficiency of the worm gear is about 0.8, it is necessary to adjust the gain by ±0.2 relative to the target value of 1.

[0123] In the above embodiment, the complementary sensitivity function was defined as Q(s)·HPF(s), where Q(s) is the transfer function of the low-pass filter and HPF(s) is the transfer function of the high-pass filter, but it is not limited to this. For example, when the transfer function of the controlled object and the transfer function of the nominal model are equal, the complementary sensitivity function may be expressed as Q(s).

[0124] The nominal model can have any transfer function. For example, if the controlled system is a single inertial frame including a motor, the transfer function P of the nominal model is... n (s) can also be expressed as in equation (7) below.

[0125]

number

[0126] In equation (7), s is the Laplace transformer, and J mn is a parameter that represents the moment of inertia of the nominal model, and B mn This parameter represents the viscous friction coefficient of the nominal model.

[0127] The correction torque generated by the assist control unit can be any torque that corrects the input torque, and the input torque may be corrected in any way. The assist control unit may also correct the input torque using the correction torque in control systems other than feedback control, such as feedforward control.

[0128] The control device and control method described herein may be any part of a steering mechanism, provided that they include at least a motor. The control device may be a control device of one inertial system or a control device of two or more inertial systems. [Explanation of Symbols]

[0129] 100...Control device, 210...Reaction force control unit, 230...Assist control unit, 232...Low-pass filter, 233...High-pass filter, 250...Friction compensation value calculation unit, 260...Disturbance compensation value calculation unit, 280...State feedback unit, 521...Steering wheel, 524a...Input shaft, 524b...Output shaft, 530...Steering mechanism, 543...Motor, 546...Torsion bar, 560...Controlled object, 1000...Electric power steering device, Cf1...First cutoff frequency, Cf2...Second cutoff frequency, P(s)...Transfer function of the controlled object, P n (s)...Transfer function of the nominal model, T(s)...Complementary sensitivity function, T a ...Differential torque, T f ...correction torque, T h ...Steering torque (torsion bar torque), T p ...torque, T r ...input torque, V d ...Disturbance compensation value, V f ...Friction compensation value, V s ...state compensation value, θa...rotation angle

Claims

1. A control device for controlling at least the portion of a steering mechanism comprising an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, wherein the control device controls at least the portion including the motor, A reaction force control unit generates an input torque input to the controlled object based on the torsion bar torque generated in the torsion bar, and controls the reaction force transmitted to the helmsman from the steering wheel. An assist control unit that generates a correction torque to correct the input torque based on the output of the controlled object and a nominal model, Equipped with, The assist control unit, A high-pass filter having a first cutoff frequency, and a low-pass filter having a second cutoff frequency higher than the first cutoff frequency, Disturbance compensation value calculation unit, It has, When the transfer function of the low-pass filter is Q(s) and the transfer function of the high-pass filter is HPF(s), the transfer function of the controlled object is configured to be constrained to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)・HPF(s) is 1. The disturbance compensation value calculation unit calculates a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object, The corrected torque includes the disturbance compensation value, The control device is a control device in which the nominal model is a model having frequency characteristics between one inertial frame and two inertial frames.

2. A control device for controlling at least the portion of a steering mechanism comprising an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, wherein the control device controls at least the portion including the motor, A reaction force control unit generates an input torque input to the controlled object based on the torsion bar torque generated in the torsion bar, and controls the reaction force transmitted to the helmsman from the steering wheel. An assist control unit that generates a correction torque to correct the input torque based on the output of the controlled object and a nominal model, Equipped with, The assist control unit, A high-pass filter having a first cutoff frequency, and a low-pass filter having a second cutoff frequency higher than the first cutoff frequency, Disturbance compensation value calculation unit, It has, When the transfer function of the low-pass filter is Q(s) and the transfer function of the high-pass filter is HPF(s), the transfer function of the controlled object is configured to be constrained to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)・HPF(s) is 1. The disturbance compensation value calculation unit calculates a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object, The corrected torque includes the disturbance compensation value, The nominal model is a control device that can compensate for at least a portion of the influence on the controlled object due to the mechanical characteristics when the helmsman steers the steering wheel.

3. The control device according to claim 1 or 2, wherein the disturbance compensation value includes a compensation value that compensates for at least a portion of the frictional force generated in the controlled object, the disturbance torque caused by the play in the controlled object, and the torque ripple generated in the controlled object.

4. The control device according to any one of claims 1 to 3, wherein the disturbance compensation value calculation unit calculates the disturbance compensation value based on the difference torque, which is the difference between the torque calculated using the nominal model based on the output of the controlled object and the input torque.

5. The control device according to claim 4, wherein the disturbance compensation value calculation unit calculates the disturbance compensation value based on the component of the differential torque having a frequency lower than the first cutoff frequency.

6. The assist control unit, The system includes a friction compensation value calculation unit that calculates a friction compensation value based on the differential torque to compensate for at least a portion of the frictional force generated in the controlled object, and The control device according to claim 4 or 5, wherein the friction compensation value and the disturbance compensation value are added to the differential torque from which frequency components lower than the first cutoff frequency have been removed by the high-pass filter to generate the corrected torque.

7. The control device according to claim 6, wherein the friction compensation value calculation unit calculates the friction compensation value based on the component of the differential torque having a frequency lower than the first cutoff frequency.

8. The control device according to any one of claims 1 to 7, wherein the assist control unit generates the correction torque based on the rotation angle of the input shaft.

9. The control device according to any one of claims 1 to 8, wherein the order of the low-pass filter is third or higher.

10. A control device according to any one of claims 1 to 9, The steering mechanism and, An electric power steering system equipped with this system.

11. A control method for controlling at least the portion of a steering mechanism that includes an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, wherein the control target is the portion including the motor. The input torque input to the controlled object is generated based on the torsion bar torque generated in the torsion bar, and the reaction force transmitted to the helmsman from the steering wheel is controlled. A correction torque for correcting the input torque is generated based on the output of the controlled object and the nominal model. Includes, Generating the aforementioned corrected torque is When the transfer function of a high-pass filter having a first cutoff frequency is HPF(s), and the transfer function of a low-pass filter having a second cutoff frequency higher than the first cutoff frequency is Q(s), the transfer function of the controlled object is constrained to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)・HPF(s) is 1. Calculate a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object, Includes, The corrected torque includes the disturbance compensation value, A control method wherein the nominal model is a model having frequency characteristics between one inertial frame and two inertial frames.

12. A control method for controlling at least the portion of a steering mechanism that includes an input shaft to which a steering wheel operated by a helmsman is connected, an output shaft connected to the input shaft via a torsion bar, and a motor connected to the output shaft, wherein the control target is the portion including the motor. The input torque input to the controlled object is generated based on the torsion bar torque generated in the torsion bar, and the reaction force transmitted to the helmsman from the steering wheel is controlled. A correction torque for correcting the input torque is generated based on the output of the controlled object and the nominal model. Includes, Generating the aforementioned corrected torque is When the transfer function of a high-pass filter having a first cutoff frequency is HPF(s), and the transfer function of a low-pass filter having a second cutoff frequency higher than the first cutoff frequency is Q(s), the transfer function of the controlled object is constrained to the transfer function of the nominal model in the frequency band where the gain in the gain characteristic of Q(s)・HPF(s) is 1. Calculate a disturbance compensation value that compensates for at least a portion of the self-aligning torque generated in the controlled object, Includes, The corrected torque includes the disturbance compensation value, A control method wherein the nominal model is a model that can compensate for at least a portion of the influence on the controlled object due to the mechanical characteristics when the helmsman steers the steering wheel.

Images