Control device, drive device, electric power steering device and control method

Abstract

Control device (1) for controlling an electric power steering device (2000), wherein the control device (1) comprises: an oversampling code extension unit (2) which performs oversampling processing on a steering torque signal according to a steering torque and obtains a post-code extension steering torque by moving average processing of a weighting of a steering torque oversampling signal obtained by the oversampling processing, and a basic support control unit (31) which obtains a basic support torque based on the post-code extension steering torque.

Description

TECHNICAL FIELD

[0001] The present invention relates to a control device that controls the drive of an electric power steering device, a drive device controlled by the control device, an electric power steering device having the drive device, and a control method. BACKGROUND TECHNOLOGY

[0002] In an electric power steering (EPS) system that uses a motor as a power source, torque ripple (pulsation) is generated due to electrical or mechanical factors. When such torque ripple occurs, abnormal noise is generated or the vehicle's steering feel deteriorates. Therefore, it is necessary to reduce such torque ripple.

[0003] Conventionally, a motor in an electric power steering device, which is considered to have low torque ripple, has a torque ripple of about 0.2 Nm. In recent years, a higher level of torque ripple suppression to the order of 0.01 Nm has been required. One method for reducing torque ripple is to improve the motor structure or improve the control technology.

[0004] In such a situation, JP H11-313497 A discloses an electric power steering device that improves a control technique for reducing torque ripple and performs current feedback control. The electric power steering device of JP H11-313497 A reduces torque ripple by using a notch filter that removes a specific frequency component contained in a control signal generated based on an actual current value.

[0005] Further exemplary control devices for controlling an electric power steering device are known from US 2008 / 0 009 993 A1, CN 1 04 661 897 A, US 2010 / 0 211 263 A1, JP H10- 324 262 A, JP 2019- 88 036 A and US 6 107 767 A. SUMMARY OF THE INVENTION TECHNICAL PROBLEMS

[0006] However, the technology of JP H11- 313 497 A may not be able to meet a current high level of requirement for suppressing torque ripple.

[0007] An object of the present invention is to provide a control device, a drive device, an electric power steering device and a control method capable of reducing torque ripple and realizing comfortable driving for a driver. SOLUTIONS TO THE PROBLEMS

[0008] The object is achieved by a control device having the features of claim 1, a drive device having the features of claim 12, an electric power steering device having the features of claim 13 and by a control method having the features of claim 14. Exemplary developments of the invention are defined in the subclaims.

[0009] A control device according to the present invention is a control device for controlling an electric power steering device, the control device comprising: an oversampling code extension unit that performs oversampling processing on a steering torque signal corresponding to a steering torque and obtains a post-code extension steering torque by moving average processing of a weight of a steering torque oversampling signal obtained by the oversampling processing; and a basic assist control unit that obtains a basic assist torque based on the post-code extension steering torque.

[0010] A drive device according to the present invention comprises the control device and an electric motor driven by the control device.

[0011] An electric power steering apparatus according to the present invention includes the control device, an electric motor driven by the control device, and an electric power steering mechanism driven by the electric motor.

[0012] A control method according to the present invention is a control method for controlling an electric power steering device, the control method comprising: performing oversampling processing on a steering torque signal corresponding to a steering torque, obtaining a post-code extension steering torque by moving average processing of a weight of a steering torque oversampling signal obtained by the oversampling processing, and obtaining a basic assist torque based on the post-code extension steering torque. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0013] According to the present invention, it is possible to reduce the torque ripple and realize comfortable driving for the driver. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the configuration of a control device according to an embodiment of the present invention. Fig. 2 is a block diagram showing a configuration of an oversampling code extension unit of the control device according to an embodiment of the present invention. Fig. 3 is a block diagram showing a configuration of a motor loss torque compensation unit of an EPS control unit of the control device according to the embodiment of the present invention. Fig. 4 is a diagram for explaining processing in the oversampling code expansion unit of the control apparatus according to the embodiment of the present invention. Fig. 5 is a diagram for explaining processing in the engine loss torque compensation unit of the EPS control unit of the control device according to the embodiment of the present invention. Fig. 6 is a diagram for explaining processing in a quantization noise reduction compensation unit of the control device according to the embodiment of the present invention. Fig. 7 is a diagram illustrating the transition of a steering torque in the processing of the control device according to the embodiment of the present invention compared with the related art. Fig. 8 is a diagram schematically showing a configuration of an electric power steering apparatus according to the embodiment of the present invention. DESCRIPTION OF AN EMBODIMENT

[0014] A control device according to an embodiment of the present invention will be described below with reference to the drawings. Note that the scope of the present invention is not limited to the embodiments described below, but includes any modifications thereof within the scope of the technical idea of ​​the present invention. Furthermore, in the following drawings, the scale, number, etc. of each structure may differ from those of the actual structures for a better understanding of the individual components. <Konfiguration einer Steuervorrichtung>

[0015] A configuration of a control device 1 according to an embodiment of the present invention will be described below with reference to Fig. 1 described in more detail.

[0016] The control device 1 controls a drive of an electric power steering mechanism described later. The control device 1 includes an oversampling code expansion unit 2, an EPS control unit 3, a quantization noise reduction compensation unit 4, and a current control unit 5. EPS stands for "Electric Power Steering."

[0017] The oversampling code expansion unit 2 performs oversampling code expansion processing on each of a steering torque signal corresponding to an input steering torque and an engine speed signal corresponding to an engine speed to obtain a post-code expansion steering torque signal and a post-code expansion engine speed signal. The oversampling code expansion unit 2 outputs the obtained post-code expansion steering torque signal to a basic assist control unit 31 of the EPS control unit 3 and outputs the obtained post-code expansion engine speed signal to an engine loss torque compensation unit 33 of the EPS control unit 3. The configuration of the oversampling code expansion unit 2 will be described later with reference to Fig. 2 described in detail.

[0018] The EPS control unit 3 obtains an assist torque of the electric power steering device based on a vehicle speed signal corresponding to the input vehicle speed, and the post-code extension steering torque signal and the post-code extension engine speed signal input from the oversampling code extension unit 2, and performs control to compensate for the obtained assist torque. The EPS control unit 3 includes a base assist control unit 31, a stabilization compensation unit 32, a motor loss torque compensation unit 33, and an adder 34.

[0019] The basic assist control unit 31 obtains a basic assist torque based on the input vehicle speed signal and the post-code extension steering torque signal input from the oversampling code extension unit 2. The basic assist control unit 31 previously stores, for example, a table in which the vehicle speed, the steering torque, and the basic assist torque are associated with each other, and refers to this table to obtain the basic assist torque associated with the vehicle speed indicated by the input vehicle speed signal and the steering torque indicated by the post-code extension steering torque signal input from the oversampling code extension unit 2.The basic assist control unit 31 outputs a basic assist torque signal corresponding to the thus obtained basic assist torque to the stabilization compensation unit 32.

[0020] The stabilization compensation unit 32 performs phase compensation by combining a plurality of phase advance compensation and phase retardation compensation for the process of advancing the phase of the basic assist torque signal input from the basic assist control unit 31. The stabilization compensation unit 32 dynamically changes the frequency characteristic of the phase compensation according to the steering state and the vehicle traveling speed. The stabilization compensation unit 32 performs the stabilization process to obtain the assist torque of the electric power steering device and outputs the assist torque signal corresponding to the obtained assist torque to the adder 34.

[0021] The motor loss torque compensation unit 33 obtains a motor loss torque compensation torque that compensates the assist torque of the electric motor based on the post-code expansion motor speed signal input from the oversampling code expansion unit 2. The motor loss torque compensation unit 33 outputs a motor loss torque compensation torque signal corresponding to the obtained motor loss torque compensation torque to the adder 34. Details of the configuration of the motor loss torque compensation unit 33 will be described later with reference to Fig. 3 described.

[0022] The adder 34 is a torque compensation unit that compensates the assist torque by adding the assist torque of the assist torque signal input from the stabilization compensation unit 32 and the motor loss torque compensation torque of the motor loss torque compensation torque signal input from the motor loss torque compensation unit 33. The adder 34 outputs an assist torque signal corresponding to the compensated assist torque to the quantization noise reduction compensation unit 4.

[0023] The quantization noise reduction compensation unit 4 reduces a quantization error contained in the assist torque signal input from the adder 34 through an IIR filter or the like and outputs the assist torque signal with the reduced quantization error to the current control unit 5. IIR stands for "Infinite Impulse Response."

[0024] The current control unit 5 calculates a drive current of the electric motor based on the assist torque signal input from the quantization noise reduction compensation unit 4. The drive current calculated by the current control unit 5 is output to an electric motor (not shown), and the electric power steering device is driven by the electric motor. <Konfiguration der Überabtastungscodeerweiterungseinheit>

[0025] A configuration of the oversampling code extension unit 2 of the control device 1 according to the embodiment of the present invention will be described below with reference to Fig. 2 described in more detail.

[0026] The oversampling code extension unit 2 includes an oversampling unit 21, an FIR filter 22, an oversampling unit 23, and an FIR filter 24.

[0027] The oversampling unit 21 oversamples the input steering torque signal, which is an analog signal or a digital signal, to generate a steering torque oversampling signal, which is a digital signal, and outputs the generated steering torque oversampling signal to the FIR filter 22. The oversampling unit 21 oversamples the steering torque signal at a cycle faster than the control cycle at the time of controlling the assist torque. For example, the oversampling cycle is 200 µs when the control cycle for controlling the assist torque is 1 ms.

[0028] The FIR filter 22 performs weighted moving average processing (weighted moving average processing) on ​​the steering torque oversampling signal input from the oversampling unit 21, thereby controlling the gain and phase of the steering torque oversampling signal to obtain a post-code extension steering torque signal. The FIR filter 22 outputs the obtained post-code extension steering torque signal to the base assist control unit 31.

[0029] The oversampling unit 23 oversamples the input motor speed signal to generate a motor speed oversampling signal and outputs the generated motor speed oversampling signal to the FIR filter 24. The oversampling unit 23 oversamples the motor speed signal at a cycle faster than the control cycle for controlling the assist torque. For example, the oversampling cycle is 200 µs when the control cycle for controlling the assist torque is 1 ms.

[0030] The FIR filter 24 performs a moving average processing of the weight of the engine speed oversampling signal input from the oversampling unit 23 to control the gain and phase of the engine speed oversampling signal to obtain a post-code extension engine speed signal. The FIR filter 24 outputs the obtained post-code extension engine speed signal to the engine loss torque compensation unit 33.

[0031] Here, the FIR filter 22 and the FIR filter 24 have the same configuration and include a multiplier 221, a register 222, a multiplier 223, an adder 224, a register 225, a multiplier 226, an adder 227, a register 228, a multiplier 229, an adder 230, a register 231, a multiplier 232, an adder 233 and a multiplier 234. It should be noted that in Fig. 2 not all registers, multipliers, and adders of the FIR filters 22 and 24 are shown. For example, the "···" between registers 225 and 228 indicates that there is a predetermined number of registers between registers 225 and 228. The "···" between multipliers 226 and 229 also indicates that there is a predetermined number of multipliers between multipliers 226 and 229. The "···" between adders 227 and 230 also indicates that there is a predetermined number of multipliers between adders 227 and 230.

[0032] The multiplier 221 multiplies an input signal x[n] from the oversampling unit 21 or the oversampling unit 23 by a weighting coefficient h0 and outputs the multiplied signal to the adder 224.

[0033] The register 222 adds a delay of one sampling cycle to the input signal x[n] from the oversampling unit 21 or the oversampling unit 23 and outputs the signal to the multiplier 223 and the register 225.

[0034] The multiplier 223 multiplies the output signal of the register 222 by a weighting coefficient h1 and outputs the multiplied signal to the adder 224.

[0035] The adder 224 adds the output signal of the multiplier 221 and the output signal of the multiplier 223 and outputs the result to the adder 227.

[0036] Register 225 adds a delay of one sampling cycle to the output signal of register 222 and outputs the signal to multiplier 226 and a register (not shown) of a subsequent stage.

[0037] The multiplier 226 multiplies the output signal of the register 225 by a weighting coefficient h2 and outputs the result to the adder 227.

[0038] The adder 227 adds the output of the adder 224 and the output of the multiplier 226 and outputs the result to an adder (not shown) in a subsequent stage.

[0039] Register 228 adds a delay of one sampling cycle to the output of the previous register and outputs the signal to multiplier 229 and register 231.

[0040] The multiplier 229 multiplies the output signal of the register 228 by a weighting coefficient h N-1 and outputs the result to the adder 230.

[0041] The adder 230 adds the output of the adder (not shown) of the previous stage and the output of the multiplier 229 and outputs the result to the adder 233.

[0042] Register 231 adds a delay of one sampling cycle to the output signal of register 228 and outputs the signal to multiplier 232.

[0043] The multiplier 232 multiplies the output signal of the register 231 by a weighting coefficient h N and outputs the result to the adder 233.

[0044] The adder 233 adds the output signal of the adder 230 and the output signal of the multiplier 232 and outputs the result to the multiplier 234.

[0045] The multiplier 234 outputs an output signal y[n], which is obtained by multiplying the output signal of the adder 233 by 1 / w, to the basic assist control unit 31 or the motor loss torque compensation unit 33. w is a total value obtained by summing (adding) the weighting coefficients h0 to h N is obtained. <Konfiguration der Motorverlustdrehmomentkompensationseinheit>

[0046] The configuration of the motor loss torque compensation unit 33 of the control device 1 according to the embodiment of the present invention will be described below with reference to Fig. 3 described in detail.

[0047] The motor loss torque compensation unit 33 includes a loss torque calculation unit 331 and a flutter suppression unit 332.

[0048] The loss torque calculation unit 331 obtains a motor loss torque compensation torque based on the post-code expansion motor speed signal input from the oversampling code expansion unit 2. Here, the motor loss torque compensation torque is a torque that compensates for a torque in advance in a range that does not become a torque even when a current flows to the electric motor due to a magnetic attraction force or the like. The loss torque calculation unit 331 outputs a motor loss torque compensation torque signal corresponding to the obtained torque to the chatter suppression unit 332.

[0049] The chatter suppression unit 332 suppresses the chatter caused in the torque signal input from the loss torque calculation unit 331 by a low-pass filter or the like and outputs the signal to the adder 34. <Betrieb der Überabtastungscodeerweiterungseinheit>

[0050] The operation of the oversampling code extension unit 2 of the control device 1 according to the embodiment of the present invention will be described below with reference to Fig. 4 described in detail.

[0051] The FIR filter 22 and the FIR filter 24 of the oversampling code expansion unit 2 can adjust the gain characteristic and the phase characteristic by adjusting the weighting factor, and increase the weight by multiplying the oversampling signal, which is the input signal, by a larger weighting coefficient (h0>h1>h2>···>h N-1 > h N ) when the oversampling signal is the latest, and perform the weighted moving average processing on the oversampling signal. As a result, as shown in Fig. 4, the FIR filter 22 or the FIR filter 24 can reduce the notch generated in a gain U2 of the post-code extension steering torque signal and the post-code extension engine speed signal, which are the output signals obtained by the weighted moving average processing, compared with the gain U1 of the post-code extension steering torque signal and the post-code extension engine speed signal obtained by the moving average, and reduce the delay of a phase U4 of the post-code extension steering torque signal and the post-code extension engine speed signal obtained by the weighted moving average processing, compared with a phase U3 of the post-code extension steering torque signal and the post-code extension engine speed signal obtained by the moving average processing.Since the FIR filter has a higher filter order than the IIR filter with the same cutoff frequency, it has the advantage of a large degree of freedom in adjusting the gain characteristics and the phase characteristics.

[0052] There is a trade-off between the controllability of the electric power steering device and the noise sensitivity. In order to suppress the high-frequency noise caused by quantization error components and the like entering the high-frequency band due to sensor noise and differential characteristics in assist control, it is necessary to increase the attenuation characteristic of the low-pass filter. However, as the attenuation characteristic increases, the phase lag also increases. As the phase lag increases, a control delay, i.e., a steering delay, occurs, causing the problem that the driver feels the steering is stiff. Therefore, in the present invention, the trade-off between the controllability of the electric power steering device and the noise sensitivity is eliminated by designing the weighting coefficients of the FIR filter.

[0053] For example, the assist control band of the electric power steering system is set to extend to 80 Hz. This reduces the phase delay to 100 Hz and configures an FIR filter with sufficient attenuation near the Nyquist frequency of -3 dB to -10 dB, which represents a compromise between the controllability and noise sensitivity of the electric power steering system. Therefore, a compromise can be found. The Nyquist frequency is half the oversampling rate.

[0054] As described above, the oversampling code expansion unit 2 oversamples the steering torque signal or the engine speed signal at a cycle faster than the control cycle at the time of controlling the assist torque, and performs the weighted moving average processing, so that it is possible to reduce the sensor noise of the AD converter or the like and increase the resolution of the digital signal used in the EPS control unit 3 from, for example, 12 bits to about 15 bits.

[0055] The method for designing the filter coefficients in the FIR filter is described in detail below.

[0056] First, the cutoff frequency is set in the FIR filter. This cutoff frequency is generally approximately 10 times higher than the control band of the electric power steering device.

[0057] Next, the order of the filter in the FIR filter is determined. Since the order of the filter can improve the resolution of the digital signal input by the moving average effect of the FIR filter, it can be adjusted according to the amount of resolution to be increased, that is, the number of bits to be increased. The relationship between the degree / order X of the filter and the number of bits Y is generally expressed as follows (Equation 1). For example, by setting the order X of the filter to 8, a number of bits Y of 3 can be obtained. This means that if the order X of the filter is set to 8, the resolution of the digital signal used in the EPS control unit 3 can be increased by 3 bits. [Math 1] X=2Y

[0058] Next, the filter coefficient of the FIR filter is calculated from the cutoff frequency and the filter order in the FIR filter described above. For example, the window function method is used to calculate the filter coefficient. At this time, the order of the filter to be used is limited to half (X / 2) or less, because there is a problem that the phase delay becomes too large when all orders of the filter are used. For example, in the case of a configuration where the order X of the filter is 8, the order of the filter used for calculating the filter coefficient is 4 or less. Here, by reducing the filter order to half or less, there is an order of the filter that is not used in the calculation of the filter coefficient. The filter coefficient calculated from the order of this filter is set to 0.

[0059] Since the filter coefficient obtained by the previous filter coefficient calculation does not increase the weighting coefficient of the last input signal, there is a problem that the phase delay becomes large. Therefore, in order to increase the weighting coefficient for the last input signal and reduce the phase delay, the filter coefficient is adjusted while maintaining the state where the sum of the filter coefficients is 1. By increasing the weighting factor of the FIR filter to the last input signal, the phase delay is improved, but there is a problem that the gain characteristic has a small amount of attenuation near the Nyquist frequency.Here, target values ​​are set for both the phase characteristic and the gain characteristic, and the weighting coefficient of the FIR filter is set such that the attenuation of the gain characteristic becomes large near the Nyquist frequency.

[0060] The setting of the weighting coefficient of this FIR filter can be obtained through an optimization process using the control system CAD. <Betrieb der Motorverlustdrehmomentkompensationseinheit>

[0061] The operation of the engine loss torque compensation unit 33 of the control device 1 according to the embodiment of the present invention will be described below with reference to Fig. 5 described in detail.

[0062] The motor loss torque compensation unit 33 sets, as the loss torque of the electric motor, a torque that does not become a torque even when a current flows due to a magnetic attraction force of a magnet of the electric motor or the like, and compensates for the loss torque.

[0063] As in Fig. Specifically, as shown in Figure 5, the motor loss torque compensation unit 33 compensates the torque of the electric motor with a loss torque compensation torque H1 in a range R1 where the torque is not achieved even when the drive current flows to the electric motor (a range where the drive current is equal to or less than a predetermined value). This allows a predetermined motor torque to be obtained in the motor drive current range R1.

[0064] As described above, the motor loss torque compensation unit 33 compensates the torque of the electric motor with the loss torque compensation torque H1 in the range R1 equal to or less than the predetermined value of the drive current, and sets the assist torque of the assist torque signal output from the EPS control unit 3 to the assist torque L2 after compensation from an assist torque L1 before compensation, whereby the responsiveness to the instruction to generate the minute assist torque in the electric motor can be improved. <Betrieb der Quantisierungsrauschreduktionskompensationseinheit>

[0065] The operation of the quantization noise reduction compensation unit 4 of the control device 1 according to the embodiment of the present invention will be described below with reference to Fig. 6 described in detail.

[0066] As in Fig. 6, the quantization noise reduction compensation unit 4 reduces the gain of the assist torque signal in a frequency band higher than a predetermined frequency of the input assist torque signal. Here, the predetermined frequency is preferably a control band in controlling the assist torque and is, for example, 100 Hz. The quantization noise reduction compensation unit 4 can reduce the gain in the frequency band higher than a predetermined frequency by reducing the gain by means of the IIR filter indicated by the solid line in Fig. 6, compared to the case where the gain is reduced by the low-pass filter, which is shown by the dashed line in Fig. 6 is displayed. The default frequency is 200 Hz, for example.

[0067] As in Fig. As shown in Figure 6, the quantization noise reduction compensation unit 4 performs phase delay compensation to reduce the gain in a frequency band higher than a predetermined frequency of the input assist torque signal. As a result, the quantization noise (quantization error) contained in the assist torque signal can be reduced. The quantization noise reduction compensation unit 4 performs phase delay compensation through the IIR filter indicated by the solid line in Fig. 6, so that it is possible to suppress deterioration of stability due to excessive decrease in phase and to delay the phase in a given frequency band, compared with the case of using the low-pass filter shown by the dashed line in Fig. 6 is displayed.

[0068] As described above, the quantization noise reduction compensation unit 4 performs phase delay compensation to reduce the gain in the frequency band higher than the predetermined frequency of the input assist torque signal, thereby reducing the quantization noise that has shifted to the high-frequency band due to the differential characteristic during processing of the EPS control unit 3. That is, the quantization noise reduction compensation unit 4 compensates for the quantization error contained in the assist torque signal by reducing the gain in the high-frequency band from the predetermined frequency of the assist torque signal. <Wirkung der Ausführungsform>

[0069] Fig. Fig. 7 is a diagram showing a result of an experiment conducted to confirm the effect of the present embodiment. As shown in Fig. 7, the control device 1 can reduce the torque ripple from 0.11 Nm in the prior art to 0.03 Nm by each processing in the oversampling code expansion unit 2, the motor loss torque compensation unit 33, and the quantization noise reduction compensation unit 4. <Ausführungsform einer Servolenkungsvorrichtung>

[0070] Vehicles such as automobiles are generally equipped with a power steering device. A power steering device generates assist torque to assist the steering torque of the steering system, which is generated by the driver operating the steering wheel. The assist torque is generated by an assist torque mechanism and can reduce the driver's burden. The assist torque mechanism includes, for example, a steering torque sensor, an ECU, an electric motor, a deceleration mechanism, and the like. The steering torque sensor detects the steering torque in the steering system. The ECU generates a drive signal based on the detection signal of the steering torque sensor. The electric motor generates assist torque corresponding to the steering torque based on the drive signal and transmits the assist torque to the steering system via the reduction mechanism.

[0071] The control device 1 of the above embodiment is used for a power steering device. Fig. 8 is a diagram schematically showing the configuration of an electric power steering apparatus 2000 according to the present embodiment.

[0072] The electric power steering apparatus 2000 includes a steering system 520 and an assist torque mechanism 540.

[0073] The steering system 520 includes, for example, a steering wheel 521, a steering shaft 522 (also referred to as a “steering column”), free shaft joints 523A and 523B, and a rotary shaft 524 (also referred to as a “pinion shaft” or “input shaft”).

[0074] The steering system 520 also includes, for example, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B, tie rods 527A and 527B, steering knuckles 528A and 528B, and left and right steering wheels (e.g., left and right front wheels) 529A and 529B.

[0075] The steering wheel 521 is connected to the rotating shaft 524 via the steering shaft 522 and the free shaft joints 523A and 523B. The rack shaft 526 is connected to the rotating shaft 524 via the rack and pinion mechanism 525. The rack and pinion mechanism 525 includes a pinion 531 provided on the rotating shaft 524 and a rack 532 provided on the rack shaft 526. The right steering wheel 529A is connected to the right end of the rack shaft 526 via the ball joint 552A, the tie rod 527A, and the knuckle 528A, in this order. Similar to the right side, the left steering wheel 529B is connected to the left end of the rack shaft 526 via the ball joint 552B, the tie rod 527B, and the steering knuckle 528B, in that order. Here, the right and left sides correspond to the right and left sides from the perspective of the driver sitting on the seat.

[0076] According to the steering system 520, when the driver operates the steering wheel 521, a steering torque is generated and transmitted to the left and right steering wheels 529A and 529B via the rack and pinion mechanism 525. As a result, the driver can operate the left and right steering wheels 529A and 529B.

[0077] The assist torque mechanism 540 includes, for example, a steering torque sensor 541, an ECU 542, an electric motor 543, a deceleration mechanism 544, and a power supply device 545. The assist torque mechanism 540 transmits an assist torque to the steering system 520 from the steering wheel 521 to the left and right steering wheels 529A and 529B. The assist torque is sometimes also referred to as "extra torque."

[0078] For example, a control circuit is used as the ECU 542. The control device 1 of Fig. 1 is included in the ECU 542, for example, as a microcontroller. An inverter, for example, is used as the power supply device 545. The ECU 542, the electric motor 543, and the power supply device 545 may form a unit, generally referred to as a "mechanically and electrically integrated motor."

[0079] Of the Fig. 8, the mechanism configured from the elements except the ECU 542, the electric motor 543, and the power supply device 545 corresponds to an example of the power steering mechanism driven by the electric motor 543.

[0080] The steering torque sensor 541 detects the steering torque of the steering system 520 applied by the steering wheel 521. The ECU 542 generates a drive signal for driving the electric motor 543 based on a detection signal from the steering torque sensor 541 (hereinafter referred to as a "torque signal"). The electric motor 543 generates an assist torque corresponding to the steering torque based on the drive signal. The assist torque is transmitted to the rotating shaft 524 of the steering system 520 via the deceleration mechanism 544. The deceleration mechanism 544 is, for example, a worm gear mechanism. Assist torque is also transmitted from the rotating shaft 524 to the rack and pinion mechanism 525.

[0081] The power steering device 2000 is classified as a pinion assist type, a rack assist type, a column assist type, or the like depending on the part where the assist torque is applied to the steering system 520. Fig. 8 shows the pinion assist type power steering device 2000. However, the power steering device 2000 may also be applied to the rack assist type, the column assist type, or the like.

[0082] Not only a torque signal, but also, for example, a vehicle speed signal can be input to the ECU 542. The microcontroller of the ECU 542 can control the electric motor 543 based on the torque signal, the vehicle speed signal, and the like through pulse width modulation.

[0083] The ECU 542 sets a target current value based at least on the torque signal. Preferably, the ECU 542 sets the target current value taking into account the vehicle speed signal detected by the vehicle speed sensor and the rotor rotation signal detected by the angle sensor. The ECU 542 can control the drive signal, i.e., the drive current, of the electric motor 543 such that the actual current value detected by the current sensor matches the target current value.

[0084] According to the power steering device 2000, the right and left steering wheels 529A and 529B can be operated by the rack shaft 526 by utilizing the combined torque resulting from the addition of the assist torque of the electric motor 543 and the driver's steering torque.

[0085] In the above, a power steering device is mentioned as an example for use in the control device of the present invention, but the use of the control device of the present invention is not limited to those described above. It is applicable to a wide range, including a pump, a compressor, or the like.

[0086] As described above, according to the present embodiment, there are provided the oversampling code extension unit 2, which performs oversampling processing on the steering torque signal corresponding to the steering torque and obtains the post-code extension steering torque by the moving average processing of the weight of the steering torque oversampling signal obtained by the oversampling processing; the basic assist control unit 31, which obtains the basic assist torque based on the post-code extension steering torque and obtains the basic assist torque signal that decreases the basic assist torque as the vehicle speed increases; the stabilization compensation unit 32, which obtains the assist torque signal corresponding to the assist torque of the electric power steering device by performing stabilization processing on the basic assist torque signal;and the quantization noise reduction compensation unit 4, which compensates for the quantization error contained in the assist torque signal by reducing the gain in the frequency band higher than the predetermined frequency of the assist torque signal, thereby reducing the torque ripple, so that it is possible to realize comfortable driving for the driver.

[0087] It should be noted that the above-described embodiments are illustrative and not restrictive in all respects. The scope of the present invention is not indicated by the above-described embodiment, but by the scope of the claims, and is intended to encompass all modifications within the meaning and scope that correspond to the scope of the claims. LIST OF REFERENCE SYMBOLS 1 control device 2 Oversampling code expansion unit 3 EPS control unit 4 Quantization noise reduction compensation unit 5 Power control unit 21 Oversampling unit 22 FIR filters 23 Oversampling unit 24 FIR filters 31 Basic support control unit 32 Stabilization compensation unit 33 Motor loss torque compensation unit 34 adders 331 Loss torque calculation unit 332 Flutter suppression unit

Claims

[1] Control device (1) for controlling an electric power steering device (2000), the control device (1) comprising: an oversampling code expansion unit (2) that performs oversampling processing on a steering torque signal according to a steering torque and obtains a post-code expansion steering torque by moving average processing of a weight of a steering torque oversampling signal obtained by the oversampling processing, and a basic assist control unit (31) that obtains a basic assist torque based on the post-code extension steering torque. [2] The control device (1) according to claim 1, wherein the basic assist control unit (31) acquires a basic assist torque signal that decreases the basic assist torque with increasing vehicle speed. [3] Control device (1) according to claim 1 or 2, further comprising: a stabilization compensation unit (32) that performs stabilization processing on the basic assist torque signal to obtain an assist torque signal corresponding to an assist torque of the electric power steering device (2000) by performing phase compensation combining a plurality of phase advance compensation and phase lag compensation for the basic assist torque signal. [4] Control device (1) according to one of claims 1 to 3, further comprising: a quantization noise reduction compensation unit (4) that compensates for a quantization error included in the assist torque signal by reducing a gain in a frequency band higher than a predetermined frequency of the assist torque signal. [5] Control device (1) according to one of claims 1 to 4, further comprising: a motor loss torque compensation unit (33) that obtains a motor loss torque compensation torque that compensates for the lost assist torque when a drive current for driving an electric motor (543) of the electric power steering device (2000) is equal to or less than a predetermined value, and a torque compensation unit (34) which compensates the assist torque obtained by the stabilization compensation unit (32) with the engine loss torque compensation torque, wherein the oversampling code expansion unit (2) performs the oversampling processing on an engine speed signal corresponding to a speed of the electric motor (543), and obtains a post-code expansion engine speed signal by moving average processing of a weight of an engine speed oversampling signal obtained by the oversampling processing, the engine loss torque compensation unit (33) obtains the engine loss torque compensation torque based on the post-code extension engine speed signal, and the quantization noise reduction compensation unit (4) compensates the quantization error included in the assist torque signal corresponding to the assist torque compensated by the torque compensation unit (34). [6] The control device (1) according to claim 5, wherein the motor loss torque compensation unit (33) suppresses chatter that occurs when the motor loss torque compensation torque is obtained. [7] The control device (1) according to any one of claims 1 to 6, wherein the oversampling code extension unit (2) performs the oversampling processing at a cycle faster than a control cycle in controlling the assist torque. [8] The control device (1) according to any one of claims 1 to 7, wherein the oversampling code extension unit (2) performs the moving average processing by an FIR filter. [9] Control device (1) according to claim 8, wherein the FIR filter has a gain characteristic near a Nyquist frequency with an attenuation of -3 to -10 dB. [10] Control device (1) according to one of claims 1 to 9, wherein the predetermined frequency is a control band for controlling the assist torque. [11] Control device (1) according to one of claims 1 to 10, wherein the quantization noise reduction compensation unit (4) compensates the quantization error by an IIR filter. [12] Drive device, comprising: a control device (1) according to one of claims 1 to 11, and an electric motor which is controlled by the control device (1). [13] Electric power steering device (2000), comprising: a control device (1) according to one of claims 1 to 11, an electric motor (543) controlled by the control device (1), and an electric power steering mechanism driven by the electric motor (543). [14] A control method for controlling an electric power steering device (2000), the control method comprising: Performing oversampling processing on a steering torque signal corresponding to a steering torque, Obtaining a post-code extension steering torque by moving average processing of a weight of a steering torque oversampling signal obtained by the oversampling processing, Obtaining a base assist torque based on the post-code extension steering torque. [15] Control method according to claim 14, comprising: Obtaining the base assist torque signal, which decreases the base assist torque with increasing vehicle speed, Stabilizing the base assist torque signal to obtain an assist torque signal corresponding to an assist torque of the electric power steering device (2000), and Compensating for a quantization error included in the assist torque signal by reducing a gain in a frequency band higher than a predetermined frequency of the assist torque signal. [16] Control method according to claim 15, comprising: performing the oversampling processing on an engine speed signal corresponding to a speed of an electric motor (543) of the electric power steering device (2000), Obtaining a post-code extension engine speed signal by moving average processing of a weight of an engine speed oversampling signal obtained by the oversampling processing, Obtaining, based on the post-code extension motor speed signal, a motor loss torque compensation torque that compensates for the assist torque lost when a drive current for driving the electric motor (543) is equal to or less than a predetermined value, and Compensating the assist torque with the motor loss torque compensation torque, wherein the quantization error contained in the assist torque signal is compensated according to the compensated assist torque.

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