ELECTRIC POWER STEERING DEVICE, CONTROL DEVICE FOR AN ELECTRIC POWER STEERING DEVICE AND CONTROL METHOD

Abstract

Control device (100) used in an electric power steering device (1000) which has a motor (543) and a delay gear (544) and is configured to control the drive of the motor (543), wherein the control device (100) has: a processor (200) and a memory (116) that stores a program for controlling the operation of the processor (200), where the processor (200) executes the program as follows: Detecting a steering torque (T) detected by a steering torque sensor (541) tor ), a vehicle speed (v) detected by a vehicle speed sensor (300), a steering angle (θ) detected by a steering angle sensor (542) and an engine speed (ω), Generating a basic support torque (T BASE ) based on the steering torque (T tor ) and the vehicle speed (v), Generating a self-aligning torque compensation torque (T SAT ) based on the steering torque (T tor ), the vehicle speed (v), the engine speed (ω) and the basic support torque (T BASE ), Generating an active restoring torque (T AR ) based on the vehicle speed (v) and the steering angle (θ), Generating a motor loss torque compensation torque (T ML ) based on the engine speed (ω), and Generating a torque command value (T) ref ), which is to be used to control the motor drive, based on the basic support torque (T BASE ), of the self-aligning torque compensation torque (T SAT ), of the active restoring torque (T AR ) and the engine loss torque compensation torque (T ML ), wherein the processor (200) refers to a table that defines a correspondence between a motor loss torque and the motor speed (ω), determines the motor loss torque based on the motor speed (ω) and applies a first-order phase delay compensation to the determined motor loss torque to obtain the motor loss torque compensation torque (T ML to generate.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an electric power steering apparatus, a control device used in the electric power steering apparatus, and a control method. BACKGROUND TECHNOLOGY

[0002] A general automobile is equipped with an electric power steering (EPS) device including an electric motor (hereinafter referred to simply as "motor"). The electric power steering device is a device that assists the driver's steering wheel operation by driving the motor. A technique has been proposed for compensating the steering feel in a central region by return control of a steering wheel in accordance with a steering angle. The central region is mainly a steering region in which the steering wheel is not significantly turned when the vehicle is traveling straight. Hereinafter, the return control of the steering wheel is referred to as "active return." JP 2002-369565 A and WO 2004 / 026665 A1 disclose techniques for compensating a desired steering characteristic in a central region by applying a pseudo self-aligning torque (SAT) through active return.

[0003] JP 2008 307 910 A discloses a control device used in an electric power steering device having a motor and a deceleration gear and configured to control the drive of the motor, the control device comprising: a processor and a memory storing a program for controlling an operation of the processor, wherein the processor executes, according to the program: detecting a steering torque detected by a steering torque sensor, a vehicle speed detected by a vehicle speed sensor, a steering angle detected by a steering angle sensor, generating a basic assist torque based on the steering torque, generating a self-aligning torque compensation torque based on the steering torque, the motor speed, and the basic assist torque,Generating an active return torque based on the vehicle speed and the steering angle, generating a motor loss torque compensation torque, and generating a torque command value to be used to control the motor drive based on the base assist torque, the self-alignment torque compensation torque, the active return torque, and the motor loss torque compensation torque.

[0004] Further control devices are known from: DE 10 2009 000 638 A1, JP 2008- 114 687 A, JP 2002- 145 101 A, PFEFFER, P.; HARRER, M.: Steering Manual, 2nd edition. Wiesbaden: Springer Vieweg, Springer Fachmedien, 2013. Pages 141, 161, 366. ISBN 978- 3-658-00976-2, GENS, W.: Expert Knowledge of the Engineer, Electrical Engineering - Electronics. 4th edition. Leipzig: VEB Fachbuchverlag. 1983. Pages 138ff., DE 10 2010 004 576 A1, US 2014 / 0 343 794 A1 and DE 695 33 576 T2. OVERVIEW OF THE INVENTIONTECHNICAL TASK

[0005] There is a need to improve the steering feel in the central area.

[0006] Embodiments of the present disclosure provide a control device and a control method for an electric power steering device that can provide a friction feeling in a central area and realize a natural steering feeling. SOLUTION TO THE TASK

[0007] The object is achieved by a control device having the features of claim 1, an electric power steering device having the features of claim 8 and by a control method having the features of claim 9. Advantageous further developments emerge from the subclaims.

[0008] In a non-limiting illustrative embodiment, a control device of the present disclosure is a control device used in an electric power steering device having a motor and a deceleration gear, and configured to control the drive of the motor. The control device includes a processor, and a memory storing a program for controlling an operation of the processor. According to the program, the processor performs: detecting a steering torque detected by a steering torque sensor, a vehicle speed detected by a vehicle speed sensor, a steering angle detected by a steering angle sensor, and a motor speed; generating a base assist torque based on the steering torque and the vehicle speed;Generating a self-aligning torque compensation torque based on the steering torque, vehicle speed, motor speed, and base assist torque; generating an active return torque based on the vehicle speed and steering angle; generating a motor loss torque compensation torque based on the motor speed; and generating a torque command value to be used to control the drive of the motor based on the base assist torque, the self-aligning torque compensation torque, the active return torque, and the motor loss torque compensation torque.

[0009] In a non-limiting illustrative embodiment, a control method of the present disclosure is a control method used in an electric power steering device that includes a motor and a deceleration gear and is configured to control the drive of the motor. The control method includes: detecting a steering torque detected by a steering torque sensor, a vehicle speed detected by a vehicle speed sensor, a steering angle detected by a steering angle sensor, and a motor speed; generating a base assist torque based on the steering torque and the vehicle speed; generating a self-aligning torque compensation torque based on the steering torque, the vehicle speed, the motor speed, and the base assist torque;Generating an active return torque based on the vehicle speed and the steering angle, generating a motor loss torque compensation torque based on the engine speed, and generating a torque command value used to control the drive of the motor based on the base assist torque, the self-alignment torque compensation torque, the active return torque, and the motor loss torque compensation torque. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0010] According to the illustrative embodiments of the present disclosure, a novel control apparatus and control method for an electric power steering apparatus are provided, which can provide a friction feeling in a central region and realize a natural steering feeling. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically shows a configuration example of an electric power steering apparatus 1000 according to the present embodiment. Fig. 2 is a block diagram showing a configuration example of a control device 100 according to the present embodiment. Fig. 3 is a functional block diagram illustrating, on a functional block basis, the functions of a processor 200 according to the present embodiment. Fig. Figure 4 is a functional block diagram describing the functions of a SAT compensation unit 220. Fig. 5 is a functional block diagram for describing the functions of a SAT estimator 221 in the SAT compensation unit 220. Fig. Figure 6 is a functional block diagram describing the functions of an active reset unit 230. Fig. 7 is a functional block diagram for describing the functions of a loss torque compensation unit 240. Fig. Figure 8 is a graph showing the motor torque characteristic for describing the motor loss torque compensation. Fig. Figure 9 is a graph showing the waveforms of steering characteristics as simulation results. Fig. 10 is a graph illustrating the steering characteristics of a general electric power steering apparatus, particularly in a central region. DESCRIPTION OF THE EMBODIMENTS

[0011] When a vehicle is traveling straight, the driver does not need to turn the steering wheel significantly. When the steering is in a central position, the feeling of friction between the vehicle and the road surface disappears, making it difficult for the driver to detect straight-line travel. For example, steering stability issues such as the vehicle swaying may occur simply by turning the steering wheel slightly. Therefore, the driver can detect the central position by appropriately generating the feeling of friction between the vehicle and the road surface.

[0012] As described above, in the related art, a desired steering characteristic in the center region is compensated by applying a pseudo-self-aligning torque through active return. However, only with active return does the corresponding frictional feeling disappear in a state where the steering wheel is positioned near the center (hereinafter referred to as the steering wheel center). Instead, an artificial feeling is provided to the driver, reinforcing the impression of being controlled by a device.

[0013] Fig. Figure 10 shows the steering characteristics of a general electric power steering device, particularly in the central region. The horizontal axis represents a steering angle (degrees), and the vertical axis represents a steering torque (N m). A range of the steering angle where the steering torque is smaller than a friction torque is generally referred to as a dead zone or hysteresis width, and a slope where the steering torque increases is referred to as a buildup. As the gain of the self-aligning torque compensation, which will be described later, increases, a cornering slope becomes steep, resulting in a steering characteristic where the steering torque increases sharply. As a result, the buildup becomes steeper, and the dead zone becomes narrower.

[0014] The steering feel in the center zone depends on the location of the steering characteristic curve and is closely related to the degree of increase in steering torque when the steering wheel is turned from the center, that is, the structure. Generally speaking, the steering feel is present when the steering torque increases sharply according to the steering angle. The narrower the dead zone, the easier it is for the driver to feel the vehicle traveling straight ahead. It is desirable to design the steering characteristics so that the hysteresis width is small, the friction feel is appropriate, and the torque build-up has a linear characteristic with respect to the steering angle. According to the inventor's research, it is desirable that the torque build-up be about 0.2 N m / degree, the hysteresis width be about ±3 degrees, and the friction feel be 1.3 N m or less than the numerical target values.

[0015] Based on the above findings, the inventor found that a natural steering feel can be achieved by appropriately utilizing the three functions of self-alignment torque compensation, active return, and motor loss torque compensation, and realized the present invention.

[0016] With reference to the accompanying drawings, a control device and a control method for an electric power steering device according to an embodiment of the present disclosure, as well as an electric power steering device including the control device, will be described in detail below. However, in some cases, specific descriptions will be omitted more than necessary. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially similar configurations may be omitted. This is done so that the following description is not redundant more than necessary and facilitates understanding by those skilled in the art.

[0017] The following embodiments are illustrative, and the control device and control method for an electric power steering device according to the present disclosure are not limited to the following embodiments. For example, the numerical values, steps, order of steps, and the like shown in the following embodiments are only illustrative, and various changes may be made unless technical inconsistencies occur. The embodiments described below are exemplary, and various combinations are possible unless technical inconsistencies occur. [1. Configuration of the electric power steering device 1000]

[0018] Fig. 1 is a diagram schematically showing a configuration example of an electric power steering apparatus 1000 according to the present embodiment.

[0019] The electric power steering device 1000 (hereinafter referred to as "EPS") includes a steering system 520 and an assist torque mechanism 540 that generates assist torque. The EPS 1000 generates assist torque to assist the steering torque of the steering system, which is generated when a driver operates a steering wheel. The assist torque reduces the burden on the driver during operation.

[0020] The steering system 520 includes, for example, a steering wheel 521, a steering shaft 522, universal joints 523A and 523B, a rotary shaft 524, a rack and pinion mechanism 525, a rack and pinion shaft 526, left and right ball joints 552A and 552B, tie rods 527A and 527B, steering knuckles 528A and 528B, and left and right steered wheels 529A and 529B.

[0021] The assist torque mechanism 540 includes, for example, a steering torque sensor 541, a steering angle sensor 542, an automotive electronic control unit (ECU) 100, a motor 543, a deceleration gear 544, an inverter 545, and a torsion bar 546. The steering torque sensor 541 detects a steering torque in the steering system 520 by detecting the amount of torsion of the torsion bar 546. The steering angle sensor 542 detects a steering angle of the steering wheel.

[0022] The ECU 100 generates a motor drive signal based on the detection signals received from the steering torque sensor 541, the steering angle sensor 542, a vehicle-mounted vehicle speed sensor (not shown), or the like, and outputs the motor drive signal to the inverter 545. The inverter 545 converts, for example, DC power into three-phase AC power with pseudo-sine waves of phases A, B, and C in accordance with the motor drive signal and supplies the power to the motor 543. The motor 543 is, for example, a surface permanent magnet synchronous motor (SPMSM) or a switched reluctance motor (SRM) and is supplied with the three-phase AC power to generate an assist torque corresponding to the steering torque. The motor 543 transmits the generated assist torque to the steering system 520 via the deceleration gear 544.Hereinafter, the ECU 100 is referred to as the EPS control device 100. [2. Exemplary configuration of the control device 100]

[0023] Fig. Figure 2 is a block diagram showing a typical configuration example of the control device 100 according to the present 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 memory (ROM) 116, and a processor 200. The control device 100 may be embodied as a printed circuit board (PCB) on which these electronic components are implemented.

[0024] A vehicle-mounted vehicle speed sensor 300, the steering torque sensor 541, and the steering angle sensor 542 are electrically connected to the processor 200. The vehicle speed sensor 300, the steering torque sensor 541, and the steering angle sensor 542 transmit, in a respective manner, a vehicle speed v, a steering torque T tor and a steering angle θ to the processor 200.

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

[0026] The control device 100 generates a torque command value based on the vehicle speed v, the steering torque T tor and a steering angle θ, etc., and controls a torque and a rotational speed of the motor 543, for example, by vector control. The control device 100 can perform not only vector control but also other controls. The rotational speed is expressed by the number of revolutions (rpm) at which a rotor rotates per unit time (e.g., one minute) or the number of revolutions (rps) at which the rotor rotates per unit time (e.g., one second). Vector control is a method in which the current flowing through the motor is divided into a current component that contributes to generating torque and a current component that contributes to generating magnetic flux, and the mutually orthogonal current components are controlled independently.

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

[0028] The angle sensor 112 is, for example, a resolver or a Hall IC. Alternatively, the angle sensor 112 is also implemented as a combination of an MR sensor with a magnetoresistive (MR) element and a sensor magnet. The angle sensor 112 detects the rotation angle of the rotor and outputs the rotation angle of the rotor to the processor 200. Instead of the angle sensor 112, the control device 100 can also include a speed sensor and an acceleration sensor for detecting the speed and acceleration of the motor.

[0029] The input circuit 113 receives a motor current value (hereinafter referred to as the "actual current value") detected by a current sensor (not shown), converts a level of the actual current value into an input level for 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 converter circuit.

[0030] The processor 200 is a semiconductor integrated circuit and is also referred to as a central processing unit (CPU) or microprocessor. The processor 200 sequentially executes a computer program stored in the ROM 116, which describes an instruction set for controlling the motor drive, and performs the desired processing. The processor 200 is generally interpreted as a term that includes a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or an application-specific standard product (ASSP) with a CPU. The processor 200 sets a target current value in accordance with, for example, the actual current value and the rotation angle of the rotor to generate a PWM signal and outputs the PWM signal to the drive circuit 115.

[0031] The communication interface 114 is an input / output interface configured to send and receive 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 a gate control signal in accordance with the PWM signal and passes the gate control signal to the gates of the multiple switching elements in the inverter 545. There is a case where a gate driver is not necessarily required if the drive target is a motor that can be operated at a low voltage. In this case, the processor 200 can perform the function of the gate driver.

[0033] The ROM 116 is electrically connected to the processor 200. The ROM 116 can be, for example, a writable memory (e.g., a PROM), a rewritable memory (e.g., a flash memory or an EEPROM), or a read-only memory. A control program is stored in the ROM 116, which includes a set of instructions that the processor 200 uses to control the motor drive. The control program is temporarily expanded into a RAM (not shown), for example, during boot-up.

[0034] Fig. Figure 3 is a functional block diagram illustrating the functions implemented in processor 200 in functional block units. In the present description, processor 200 includes a basic assist control unit 210, a SAT compensation unit 220, an active reset unit 230, a loss torque compensation unit 240, a stabilization compensator 250, a current control calculation unit 260, three adders 271, 272, and 273, and a motor control unit 280. Typically, the processes (or tasks) of the functional blocks corresponding to the respective units are described in the computer program on a software module basis and stored in ROM 116. However, if an FPGA or the like is used, all or some of the functional blocks may be implemented as hardware accelerators.

[0035] In a case where each functional block is implemented as software (or firmware) in the control device 100, a device that executes the software may be the processor 200. In one aspect, the control device according to the present disclosure includes the processor and a memory that stores a program that controls the operation of the processor. The processor executes the following processing in accordance with the program. (1) A steering torque detected by the steering torque sensor, a vehicle speed detected by the vehicle speed sensor, a steering angle detected by the steering angle sensor, and an engine speed are detected. (2) A basic assist torque is generated based on the steering torque and vehicle speed. (3) Based on the steering torque, vehicle speed, engine speed and base assist torque, a self-aligning torque compensation torque is generated. (4) Based on the vehicle speed and steering angle, an active restoring torque is generated. (5) Based on the engine speed, an engine loss torque compensation torque is generated. (6) A torque command value used to control the motor drive is generated based on the base assist torque, the self-alignment torque compensation torque, the active return torque, and the motor loss torque compensation torque. (7) A target current value is generated based on the torque command value, and the drive of the motor is controlled based on the current command value.

[0036] In a case where each functional block is implemented as software and / or hardware in the control device 100, a control device of the present disclosure in another aspect includes: a basic assist control unit that generates a basic assist torque based on a steering torque and a vehicle speed; a SAT compensation unit that generates a self-alignment torque compensation torque based on the steering torque, the vehicle speed, a motor speed, and the basic assist torque; an active return unit that generates an active return torque based on the vehicle speed and a steering angle; a loss torque compensation unit that generates a motor loss torque compensation torque based on the motor speed; a current control calculation unit;which generates a current command value in accordance with a torque command value generated based on the base assist torque, the self-alignment torque compensation torque, the active return torque, and the motor loss torque compensation torque, and a motor control unit that controls the drive of the motor based on the current command value.

[0037] The processor 200 receives as inputs the steering torque T detected by the steering torque sensor 541 tor, the vehicle speed v detected by the vehicle speed sensor, the steering angle θ detected by the steering angle sensor, and an engine speed ω. For example, if the control device 100 includes a speed sensor that detects a rotational speed of the engine, the processor 200 may detect the engine speed ω by detecting the detected rotational speed from the speed sensor. In a case where the control device 100 includes an angle sensor that detects a rotational angle (more precisely, a mechanical angle) of the rotor, the processor 200 may detect the rotational speed ω by detecting the detected rotational angle of the rotor from the angle sensor and calculate an angular velocity based on the rotational angle of the rotor.

[0038] The basic support control unit 210 detects the steering torque T tor and the vehicle speed v as inputs and generates a base assist torque T BASEbased on the signals and outputs it. A typical example of the basic assistance control unit 210 is a table (so-called lookup table / value table) that shows a correspondence between the steering torque T tor , the vehicle speed v and the base assistance torque T BASE The basic assistance control unit 210 determines the basic assistance torque T BASE based on the steering torque T tor and the vehicle speed v.

[0039] Fig. Figure 4 illustrates functional blocks describing the functions of the SAT compensation unit 220. Fig. Figure 5 shows functional blocks for describing the functions of the SAT estimator 221 in the SAT compensation unit 220. The SAT compensation unit 220 detects the steering torque T tor , the vehicle speed v, the engine speed ω and the base assistance torque T BASEas inputs and generates the self-alignment torque compensation torque T SAT based on these signals and outputs this.

[0040] The SAT compensation unit 220 compensates for a static amplification of a self-aligning torque. This makes it possible to improve the width of a dead zone and the buildup in a central area while maintaining a friction feel.

[0041] The self-alignment torque is determined from the balance of static forces around the steering wheel shaft between the base assistance torque T BASE and the steering torque T tor Therefore, the estimated self-alignment torque includes not only the self-alignment torque compensation torque T SAT, but also the friction in the estimation result. Therefore, the SAT compensation unit 220 according to the present embodiment applies a friction model to the SAT compensation to reduce the influence of friction on the estimation result.

[0042] The SAT compensation unit 220 includes the SAT estimator 221, a SAT gain correction unit 222, and a filter 223. The SAT estimator 221 detects the steering torque T tor , the base assistance torque T BASE and the engine speed ω as inputs and estimates the self-aligning torque based on these signals. The SAT estimator 221 includes a friction model 224, gains (or control gains) 225 and 226, and an adder 227. The SAT estimator 221 refers to a table defining a correspondence between the friction torque and the engine speed and determines the steering torque T tor based on the engine speed ω.

[0043] The friction model 224 is determined, for example, based on a Coulomb friction model. A friction torque T fric is calculated based on the engine speed ω using the friction model 224. The gain 225 is a gear ratio gc of the deceleration gear 544, and the gain 226 is a friction gain. The adder 227 calculates an estimated value of the self-aligning torque based on the following formula 1. The term T fric on the right side of Formula 1 includes the friction amplification. If the term T fric is subtracted from the right side of Formula 1, the influence of friction on the estimation result is reduced. TSAT=Ttor+gc*TBASE−Tfric

[0044] A typical example of the SAT gain correction unit 222 is a reference table that shows a correspondence between the vehicle speed v and a gain g s In the present embodiment, the gain g s relative to the estimated value of the self-aligning torque according to the vehicle speed v. The SAT gain correction unit 222 refers to a table that defines a correspondence between the gain and the vehicle speed relative to the estimated value of the self-aligning torque, and determines the gain g s relative to the estimated value of the self-aligning torque based on the vehicle speed v. The SAT gain correction unit 222 further multiplies the estimated self-aligning torque by the gain g sto correct the self-aligning torque in accordance with the vehicle speed v, thereby generating the corrected self-aligning torque.

[0045] For example, filter 223 applies a first-order phase lag compensation to the estimated self-alignment torque to obtain the self-alignment torque compensation torque T SAT to generate. An example of filter 223 is a first-order digital filter with infinite impulse response (IIR). When the motor speed ω is close to zero, chatter in the self-alignment torque may occur, which is the estimation result of the SAT estimator 221. When first-order phase delay compensation is applied by filter 223, the chatter can be adequately suppressed.

[0046] As described above, the SAT compensation unit 220 can change the strength of the SAT compensation by adjusting each steering gain. Note that the steering becomes heavy near the steering wheel center because a pseudo-self-alignment torque is likely to be excessively increased if the steering gain is excessively increased.

[0047] In Fig. 6 shows functional blocks for describing the functions of the active return unit 230. The active return unit 230 detects the vehicle speed v and the steering angle θ as inputs and generates an active return torque T ARThe active return unit 230 includes a return torque calculation unit 231, a vehicle speed gain correction unit 232, a multiplier 233, and a phase compensator 234. The return torque calculation unit 231 is a table that defines a correspondence between the steering angle and the active return torque (return torque), and the return torque calculation unit 231 determines the active return torque in accordance with the steering angle. The vehicle speed gain correction unit 232 is a table that defines a correspondence between the vehicle speed and a gain g a relative to the active restoring torque. The vehicle speed gain correction unit 232 determines the gain g aaccording to the vehicle speed v. The multiplier 233 multiplies the active return torque determined by the active return unit 230 and the gain g determined by the vehicle speed gain correction unit 232 a . The phase compensator 234 generates the active restoring torque T AR by applying a phase delay compensation or a phase advance compensation to a result of multiplication by the multiplier 233.

[0048] The active return unit 230 can improve the setup by applying pseudo self-aligning torque according to the steering angle. Note that an artificial steering feel is likely to be generated because the return (active return) of the steering wheel becomes too strong if the steering gain is excessively increased, which is similar to SAT compensation.

[0049] Fig. 7 shows functional blocks for describing the functions of the loss torque compensation unit 240. Fig. Figure 8 shows the motor torque characteristic for describing the motor loss torque compensation. The loss torque compensation unit 240 generates a motor loss torque compensation torque T ML based on the motor speed ω. The loss torque compensation unit 240 refers to a table that defines a correspondence between a motor loss torque and the motor speed, determines the motor loss torque based on the motor speed ω, and applies a first-order phase delay compensation to the determined motor loss torque, thereby determining the motor loss torque compensation torque T ML is generated.

[0050] The loss torque compensation unit 240 includes a loss torque calculation unit 241 and a filter 242. Here, the compensation of the motor loss torque is performed with reference to Fig. 8. The horizontal axis represents a motor current (A), and the vertical axis represents a motor torque (N m). The dashed line in the drawing indicates the characteristic of the motor torque with respect to the motor current when loss torque compensation is not applied. A solid line in the drawing indicates the characteristic of the motor torque with respect to the motor current when loss torque compensation is applied. For example, there is a motor current range WA in which no torque is generated due to the attractive force of a permanent magnet arranged in the rotor, even when current flows through the motor. In the present embodiment, loss torque compensation is used to compensate for a torque loss in the motor current range W Ato compensate. More specifically, the loss torque calculation unit 241 determines a loss torque compensation torque for performing the loss torque compensation in accordance with the engine speed ω. The loss torque calculation unit 241 is a table that defines a correspondence between the engine speed and the torque for performing the loss torque compensation. The table is determined based on, for example, a Coulomb friction model.

[0051] The filter 242 generates the loss torque compensation torque T ML by applying first-order phase delay compensation to the determined loss torque compensation torque of the motor. An example of filter 242 is a first-order digital IIR filter, similar to filter 223. When a general low-pass filter is used as filter 242, a high-frequency component contained in the loss torque compensation torque TML is removed, but a phase delay may occur, and as a result, a delay in the power assist of the EPS is likely to occur. On the other hand, when the first-order IIR filter is used as the filter 242, the chatter of a loss torque compensation torque signal output from the loss torque calculation unit 241 can be suppressed, and normal power assist can be performed while avoiding the phase delay.

[0052] The loss torque calculation unit 241 can improve the response to a small torque command by compensating for the engine loss torque. As a result, the steering friction feel at the steering wheel center is improved.

[0053] It will be repeated again Fig. 3.

[0054] The adder 271 adds the self-alignment torque compensation torque T output from the SAT compensation unit 220 SAT to the base support torque T BASE output from the base support control unit 210.

[0055] A torque command value T ref is based on the base assistance torque T BASE , the self-alignment torque compensation torque T SAT , the active restoring torque T AR and the motor loss torque compensation torque T ML The stabilization compensator 250 applies, for example, a phase lag compensation or a phase advance compensation to an addition value obtained by the adder 271 to generate a stabilization compensation torque. The adder 272 adds the active reset torque T output from the active reset unit 230. ARto the stabilization compensation torque output by the stabilization compensator 250. The adder 273 adds the loss torque compensation torque T output by the loss torque compensation unit 240 ML to an addition value obtained from the adder 272, whereby the torque command value T ref which is used to control the motor drive. The stabilization compensator 250 can receive the output of the adder 272 and / or the output of the adder 273, as with the output of the adder 271.

[0056] The current control calculation unit 260 generates a current command value I ref based on the torque command value T ref . The motor control unit 280 provides, based on the current command value I ref a current command value by vector control to generate, for example, a PWM signal, and outputs the PWM signal to the drive circuit 115.

[0057] According to the present embodiment, a natural steering feel can be achieved by utilizing the three functions of SAT compensation, active return, and motor loss torque compensation in a manner that complements each other. Specifically, the natural steering feel can be realized by generating, to a certain extent, a steering characteristic that can achieve the natural steering feel in the central region through SAT compensation, and by finely adjusting the steering characteristic in a direction in which the hysteresis width decreases through active return. Furthermore, the loss torque compensation improves the response to minute torque commands, thereby realizing a more natural steering feel.

[0058] The inventor of the present invention verified the validity of the control device 100 according to the present embodiment through simulation. As simulation conditions, the vehicle speed v was set to 60 km / h and the steering frequency to 0.25 Hz. Fig. Figure 9 shows graphs of the steering characteristics as simulation results. The horizontal axis represents the steering angle, and the vertical axis represents the steering torque. A waveform indicated by a dashed line shows a steering characteristic in a case where SAT compensation was not applied, and a waveform indicated by a solid line shows a steering characteristic in a case where SAT compensation was applied.

[0059] The simulation results show that the hysteresis width of the steering angle is improved by applying SAT compensation. Specifically, the hysteresis width was 16 degrees when SAT compensation was not applied, and the hysteresis width was 10 degrees when SAT compensation was applied. In such a steering angle range, it is typically difficult to detect the steering wheel center position from the steering torque information, and the vehicle is likely to deviate. Therefore, the hysteresis width of the steering angle is preferably narrow. The range where it is difficult to detect the steering wheel center position is a residual steering wheel angle where the steering wheel does not return to the steering wheel center position due to self-alignment torque, and the driver must intentionally return the steering wheel.Therefore, the assist torque for assisting in the direction of returning the steering wheel is generated by the SAT compensation and the active return to reduce the residual steering wheel angle in the present embodiment. INDUSTRIAL APPLICABILITY

[0060] Embodiments of the present disclosure may be applicable to a control device for controlling an electric power steering device mounted in a vehicle. LIST OF REFERENCE SYMBOLS 200 processor 210 Basic support control unit 220 SAT compensation unit 221 SAT estimators 222 SAT gain correction unit 223 filters 224 Friction model 225, 226 reinforcement 227 adders 230 active reset unit 231 Return torque calculation unit 232 Vehicle speed gain correction unit 233 multipliers 234 Phase compensator 240 Loss torque compensation unit 241 Loss torque calculation unit 242 filters 250 stabilization compensator 260 Power control calculation unit 271, 272, 273 adders 280 Engine control unit

Claims

[1] A control device (100) used in an electric power steering device (1000) having a motor (543) and a deceleration gear (544) and configured to control the drive of the motor (543), the control device (100) comprising: a processor (200) and a memory (116) storing a program for controlling operation of the processor (200), wherein the processor (200) executes according to the program: Detecting a steering torque (T tor ), a vehicle speed (v) detected by a vehicle speed sensor (300), a steering angle (θ) detected by a steering angle sensor (542) and an engine speed (ω), Generating a base support torque (T BASE ) based on the steering torque (T tor ) and the vehicle speed (v), Generating a self-alignment torque compensation torque (T SAT ) based on the steering torque (T tor ), the vehicle speed (v), the engine speed (ω) and the base assistance torque (T BASE ), Generating an active restoring torque (T AR ) based on the vehicle speed (v) and the steering angle (θ), Generating a motor loss torque compensation torque (T ML ) based on the engine speed (ω), and Generating a torque command value (T ref ) to be used to control the motor drive, based on the base assist torque (T BASE ), the self-alignment torque compensation torque (T SAT ), the active restoring torque (T AR ) and the motor loss torque compensation torque (T ML ), wherein the processor (200) refers to a table defining a correspondence between a motor loss torque and the motor speed (ω), determines the motor loss torque based on the motor speed (ω), and applies a first-order phase lag compensation to the determined motor loss torque to determine the motor loss torque compensation torque (T ML ) to generate. [2] Control device (100) according to claim 1, characterized by that the processor (200) further executes: Generating a stabilization compensation torque using a stabilization compensator (250) based on the base assist torque (T BASE ) and the self-alignment torque compensation torque (T SAT ), and Generating the torque command value (T ref ) based on the active restoring torque (T AR ), the motor loss torque compensation torque (TML ) and the stabilization compensation torque. [3] Control device (100) according to claim 2, characterized by that the generation of the self-alignment torque compensation torque (T SAT ) estimating a self-alignment torque compensation torque T SAT based on the following formula: TSAT=Ttor+gc*TBASE−Tfric, where T tor represents the steering torque, g c represents a gear ratio of the deceleration gear (544), T BASE represents the base assistance torque and T fric represents the friction torque. [4] Control device (100) according to claim 3, characterized by that the processor (200) refers to a table defining a correspondence between the friction torque and the engine speed (ω) and determines the friction torque based on the engine speed (ω). [5] Control device (100) according to claim 4, characterized by , that the processor (200) refers to a table defining a correspondence between a self-alignment torque gain and the vehicle speed (v), and determines the self-alignment torque gain based on the vehicle speed (v), and the estimated self-aligning torque is multiplied by the self-aligning torque gain to correct the self-aligning torque according to the vehicle speed (v), and a corrected self-aligning torque is generated. [6] Control device (100) according to claim 5, characterized by that the processor (200) applies a first-order phase shift compensation to the corrected self-alignment torque to determine the self-alignment torque compensation torque (T SAT ) to generate. [7] Control device (100) according to one of claims 1 to 6, characterized by that the processor (200) further comprises generating a current command value (I ref ) based on the torque command value (T ref ) and controlling the drive of the motor (543) based on the current command value (I ref ) executes. [8] An electric power steering apparatus (1000) comprising: a motor (543), a steering torque sensor (541), a steering angle sensor (542), and the control apparatus (100) according to any one of claims 1 to 7. [9] A control method used in an electric power steering apparatus (1000) having a motor (543) and a deceleration gear (544) and configured to control the drive of the motor (543), the control method comprising: Detecting a steering torque (T tor), a vehicle speed (v) detected by a vehicle speed sensor (300), a steering angle (θ) detected by a steering angle sensor (542) and an engine speed (ω), Generating a base support torque (T BASE ) based on the steering torque (T tor ) and the vehicle speed (v), Generating a self-alignment torque compensation torque (T SAT ) based on the steering torque (T tor ), the vehicle speed (v), the engine speed (ω) and the base assistance torque (T BASE ), Generating an active restoring torque (T AR ) based on the vehicle speed (v) and the steering angle (θ), Generating a motor loss torque compensation torque (T ML ) based on the engine speed (ω), and Generating a torque command value (T ref) to be used to control the motor drive, based on the base assist torque (T BASE ), the self-alignment torque compensation torque (T SAT ), the active restoring torque (T AR ) and the motor loss torque compensation torque (T ML ), where the motor loss torque compensation torque (T ML ) is generated by referring to a table defining a correspondence between a motor loss torque and the motor speed (ω), determining the motor loss torque based on the motor speed (ω), and applying a first-order phase delay compensation to the determined motor loss torque. [10] Control method according to claim 9, characterized by that the control method further comprises: Generating a stabilization compensation torque using a stabilization compensator (250) based on the base assist torque (T BASE ) and the self-alignment torque compensation torque (T SAT ), where the torque command value (T ref ) based on the active restoring torque (T AR ), the motor loss torque compensation torque (T ML ) and the stabilization compensation torque. [11] Control method according to claim 10, characterized by that the generation of the self-alignment torque compensation torque (T SAT ) estimating a self-alignment torque compensation torque T SAT based on the following formula: TSAT=Ttor+gc*TBASE−Tfric where T tor represents the steering torque, g c represents a gear ratio of the deceleration gear, TBASE represents the base assistance torque and T fric represents a friction torque. [12] Control method according to claim 11, characterized by that the friction torque is determined on the basis of the engine speed (ω) using a table that defines a correspondence between the friction torque and the engine speed (ω). [13] Control method according to claim 12, characterized by , that a self-aligning torque gain based on the vehicle speed (v) is determined by reference to a table defining a correspondence between the self-aligning torque gain and the vehicle speed (v), and the estimated self-aligning torque is multiplied by the self-aligning torque gain to correct the self-aligning torque according to the vehicle speed (v), and a corrected self-aligning torque is generated. [14] Control method according to claim 13, characterized by that the self-alignment torque compensation torque (T SAT ) is generated by applying a first-order phase shift compensation to the corrected self-alignment torque. [15] Control method according to one of claims 9 to 14, characterized by that the control method further comprises: Generating a current command value (I ref ) based on the torque command value (T ref ) and controlling the drive of the motor (543) based on the current command value (I ref ).

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