Steering system, control method thereof, and program

Abstract

To reduce a deterioration in steering feeling occurring due to the structure of an electric power steering, in a configuration in which the electric power steering is combined with a hydraulic power steering.SOLUTION: A steering system is equipped with: a steering mechanism including a steering shaft; a turning mechanism that turns a turning wheel in tandem with rotation of the steering shaft; a power steering device provided in the turning mechanism; an electric power steering device provided in the steering mechanism; and a control part that controls operation of the electric power steering device. The control part derives a compensation value of coulomb friction caused by parts constituting the electric power steering device, and outputs a control value for controlling the parts by using the compensation value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steering system, a control method thereof, and a program. [Background technology]

[0002] In recent years, various technologies have been developed for power steering devices in order to realize functions such as advanced driver-assistance systems (ADAS) and autonomous driving (AD) in vehicles. For example, consider implementing ADAS and AD in buses and trucks. Most mass-produced buses and trucks are equipped with hydraulic power steering (HPS). For such vehicles, it is conceivable to make them compatible with autonomous driving by retaining the existing HPS and installing a relatively low-output electric power steering (EPS) in the upper part of the power steering system. In such a configuration, for example, a column EPS can be used.

[0003] For example, Patent Document 1 discloses a configuration in which an EPS and an HPS are combined, and the torsion settings of the torsion bar are made different on the EPS side and the HPS side, thereby allowing the EPS to operate in the event of a failure of the HPS.

[0004] Furthermore, Patent Document 2 discloses a configuration that combines an EPS and an HPS, assuming vehicles such as large trucks and buses. In this configuration, it is described that the EPS operates as a steering actuator when a lane keeping assist function is activated, and cooperates with the HPS to provide steering assist during normal operation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6222427 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-264622 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a column EPS is installed above the HPS, problems with steering arise, such as heavier steering and poorer steering return, compared to a conventional HPS configuration with a manual column, due to friction from the reducer and motor that make up the column EPS.

[0007] Although the above-mentioned prior art documents disclose a configuration in which an EPS and an HPS are combined, they do not sufficiently consider the deterioration of steering performance that may result from the combination of these.

[0008] In view of the above problems, the present invention aims to reduce the deterioration of steering feel caused by the structure of electric power steering in a configuration in which electric power steering and power steering of a steering mechanism are combined. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration: That is, a steering system comprising: a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a control unit that controls the operation of the electric power steering device; Equipped with The control unit is characterized in that it derives a compensation value for Coulomb friction generated by a component constituting the electric power steering device, and uses the compensation value to output a control value for controlling the component.

[0010] Another aspect of the present invention has the following configuration: a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; A method for controlling a steering system comprising: The present invention is characterized in that a compensation value for Coulomb friction generated by a component of the electric power steering device is derived, and a control value for controlling the component is output using the compensation value.

[0011] Another aspect of the present invention has the following configuration: a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a computer for controlling a steering system comprising: A program is provided for causing the electric power steering device to function as a control unit that derives a compensation value for Coulomb friction generated by a component of the device and uses the compensation value to output a control value for controlling the component. [Effects of the Invention]

[0012] According to the present invention, in a configuration in which an electric power steering system and a power steering system of a steering mechanism are combined, it is possible to reduce deterioration in steering performance caused by the structure of the electric power steering system. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a schematic diagram showing an example of the general configuration of a hydraulic power steering device; [Figure 1B] 1 is a schematic diagram showing an example of the general configuration of a steering system having the functions of both a hydraulic power steering device and an electric power steering device. [Figure 2] FIG. 1 is a diagram showing an example of a functional configuration according to an embodiment of the present invention. [Figure 3] FIG. 2 is a block diagram showing a conceptual configuration of a static friction compensation function according to an embodiment of the present invention. [Figure 4] FIG. 4 is a graph illustrating a static friction compensation function according to an embodiment of the present invention. [Figure 5] FIG. 2 is a block diagram showing a conceptual configuration of a dynamic friction compensation function according to an embodiment of the present invention. [Figure 6] FIG. 4 is a graph illustrating a dynamic friction compensation function according to an embodiment of the present invention. [Figure 7] FIG. 1 is a graph illustrating fade switching according to an embodiment of the present invention. [Figure 8] FIG. 10 is a graph illustrating verification results according to an embodiment of the present invention. [Figure 9] FIG. 4 is a graph illustrating an example of operating torque caused by a manual column. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention and is not intended to be interpreted as limiting the present invention. Furthermore, not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. Furthermore, in each drawing, the same components are assigned the same reference numerals to indicate correspondence.

[0015] First Embodiment A first embodiment of the present invention will be described below. Note that the configuration of the electric power steering device shown below is one example, and the present invention is applicable to steering systems in general, including steering devices.

[0016] [Configuration overview] Before describing the configuration of the steering system of the present invention, the configuration of a conventional hydraulic power steering device will be described for comparison. As described above, it is assumed that vehicles such as buses and trucks are equipped with hydraulic power steering devices (HPS).

[0017] FIG. 1A is a diagram showing an example of the schematic configuration of a hydraulic power steering device 100. The steering wheel 1 is a steerable wheel used by a driver to perform steering operation. The steering shaft 2 of the steering wheel 1 includes a manual column and is connected to a rotary control valve 7 via a universal joint 4a, an intermediate shaft 5, a universal joint 4b, and a bevel gear 6. The steering shaft includes the steering shaft 2, the universal joint 4a, the intermediate shaft 5, the universal joint 4b, and the bevel gear 6. The rotary control valve 7 supplies oil, which is supplied from a tank 9 via a hydraulic pump 8, to a hydraulic chamber 10. The rotary control valve 7 controls the flow rate of oil to the hydraulic chamber 10 based on the steering force transmitted from the steering wheel 1, reaction force from the road surface, and the like. The hydraulic chamber 10 drives a power cylinder (not shown) inside a steering box 11. Although not shown in FIG. 1A, the steering box 11 also includes a pinion connected to a pinion shaft to which the steering force from the steering wheel 1 is transmitted, a rack fitted to the pinion, and the like. The rotational motion transmitted to the pinion is converted into linear motion in the vehicle width direction by the rack. The driving force from the power cylinder is connected to steered wheels 15a, 15b via left and right connecting parts 12a, 12b, tie rods 13a, 13b, and hub units 14a, 14b.

[0018] Next, a configuration example of an electric power steering system (EPS) according to this embodiment will be described. As described above, the electric power steering system according to this embodiment is intended to enable driving control by autonomous driving (AD) or advanced driver assistance systems (ADAS) for vehicles such as buses that have conventionally been equipped with an HPS. Examples of ADAS functions include a lane keeping function and a lane change function, but the types are not particularly limited.

[0019] 1B is a diagram showing an example of the schematic configuration of a steering system 110 according to this embodiment. The configuration of the HPS on the steered wheels 15 side (hereinafter also referred to as the downstream side) is the same as that shown in FIG. 1A, but on the steering wheel 1 side (hereinafter also referred to as the upstream side), an EPS functional unit 30 is provided instead of the manual column. In other words, the EPS functional unit 30 is provided on a steering shaft that includes a steering shaft 2, a universal joint 4a, an intermediate shaft 5, a universal joint 4b, a bevel gear 6, etc. Here, a description of the HPS located on the downstream side will be omitted.

[0020] The steering shaft 2 is provided with a torque sensor 31 that detects a steering torque T applied to a torsion bar (not shown). The torque sensor 31 also detects a steering angle θ , which indicates the rotation angle of the steering shaft 2 around the axis on the steering wheel 1 side (upstream side). h and an output shaft angle θ indicating the rotation angle around the axis of the universal joint 4a side (downstream side) of the steering shaft 2. c That is, the torque sensor 31 may be configured to detect the steering angle θ h and output shaft angle θ c The steering torque T is detected based on the twist of the torsion bar caused by the difference between the torques. Furthermore, information on the steering torque T and the rotation angle θ is notified to an EPS-ECU (Electronic Control Unit) 32 via a torque sensor 31.

[0021] In FIG. 1B, the torque sensor 31 is shown as a single sensor. h and output shaft angle θ cA steering angle sensor and an output shaft angle sensor may be configured separately as sensors for detecting each. Therefore, the configuration of the torque sensor 31 is not particularly limited, and for example, a sleeve type or a ring type that detects torque from the twist of a torsion bar may be used. In the above configuration, the steering torque T is calculated based on the steering angle θ h and output shaft angle θ c However, the present invention is not limited to this. For example, the steering torque T may be detected using the difference between the angle signal on the steering wheel 1 side of the torsion bar and the angle signal on the universal joint 4a side.

[0022] A steering assist motor 33 that assists the steering force applied to the steering wheel 1 is connected to the steering shaft 2 via a worm 34 and a worm wheel 35 that form a reduction gear. An EPS-ECU 32 that is a controller that controls the EPS is supplied with power from a battery (not shown). Note that the means for applying the steering assist force to the steering shaft 2 is not limited to a motor, and various types of actuators may be used.

[0023] The EPS-ECU 32 calculates a current command value as an assist command value based on the steering torque T and rotation angle θ detected by the torque sensor 31, and various information provided by the vehicle-side ECU 40. The information provided by the vehicle-side ECU 40 includes the vehicle speed V detected by a vehicle speed sensor (not shown), h The EPS-ECU 32 outputs an output voltage V according to a current command value based on the steering torque T and a current command value based on the driving support function. m The steering assist motor 33 controls the power supplied to the steering assist motor 33 based on the output voltage V m Based on this, the worm 34 and the worm wheel 35 are operated to perform assist control for the steering wheel 1. Also, the output voltage V m The motor current I applied to the steering assist motor 33 in accordance with mis detected by a motor current detection unit (not shown) and notified to the EPS-ECU 32. Also, the motor angle θ of the steering assist motor 33 m is detected by a motor angle sensor (not shown) configured by an encoder, resolver, etc., and notified to the EPS-ECU 32.

[0024] The EPS-ECU 32 may include, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device may include any of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include memories such as a register, a cache memory, and a ROM (Read Only Memory) and a RAM (Random Access Memory) used as a main storage device. The functions of the EPS-ECU 32 described below are realized, for example, by the processor of the EPS-ECU 32 executing a computer program stored in the storage device.

[0025] The EPS-ECU 32 may be formed by dedicated hardware for executing each of the information processes described below. For example, the EPS-ECU 32 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit. For example, the EPS-ECU 32 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0026] The vehicle-side ECU 40 may also have the same configuration as the EPS-ECU 32, or may have a different configuration depending on the functions realized by the AD or ADAS. Furthermore, the vehicle-side ECU 40 may be realized by a plurality of ECUs.

[0027] By providing the EPS functional unit 30 as described above around the steering shaft 2, more friction occurs around the steering shaft 2 than in the configuration of the hydraulic power steering device 100 as shown in FIG. 1A. As a result, it is expected that the friction will cause a deterioration in steering performance. For example, friction at the contact surfaces between the steering shaft 2 and each component, such as the steering assist motor 33, the worm 34, and the worm wheel 35, can cause the deterioration in steering performance. In this embodiment, control is performed to suppress such a deterioration in steering performance. More specifically, in this embodiment, a compensation value for Coulomb friction (static friction and kinetic friction) caused by the functional unit 30 around the steering shaft 2 is derived, and the steering assist motor 33 is controlled based on the compensation value.

[0028] [Function Configuration] FIG. 2 is a block diagram showing an example of a functional configuration related to a friction compensation function in the EPS-ECU 32 according to this embodiment. In FIG. 2, the arrows indicate an example of data flow, but the flow is not limited to that shown here, and other data may be transmitted and received when components are linked together. Also, while FIG. 2 shows only the functions according to this embodiment, the EPS-ECU 32 may further include configurations for realizing other functions. For example, the EPS-ECU 32 may further include a component for calculating an assist command value and a component for performing various processes corresponding to the ADAS function.

[0029] The Coulomb friction compensation unit 200 includes a static friction compensation unit 210, a dynamic friction compensation unit 220, and a fade switching unit 230. The static friction compensation unit 210 receives the steering torque T detected by the torque sensor 31 as an input, and calculates a static friction compensation value F due to static friction. s The dynamic friction compensation unit 220 receives the steering speed ω as an input and derives a dynamic friction compensation value F d and steering state determination flag L s The steering speed ω is calculated by multiplying the steering angle θ detected by the torque sensor 31. h The steering speed ω is calculated by a steering speed calculation unit (not shown) of the EPS-ECU 32 based on the motor angle θ. The steering speed ω may be calculated on the torque sensor 31 side and notified to the EPS-ECU 32.m The fade switching unit 230 may obtain the static friction compensation value F s , dynamic friction compensation value F d , and the steering state determination flag L s Based on the value of Coulomb friction compensation value F c Switching parameters for calculating the Coulomb friction compensation value F c is derived.

[0030] (Static friction compensation section) 3 is a block diagram showing an example of the functional configuration of the static friction compensation unit 210 according to this embodiment. The static friction compensation unit 210 includes an input filter unit 211, a torque hysteresis center calculation unit 212, a subtraction unit 213, and a static friction gain unit 214.

[0031] The input filter unit 211 is configured for the purpose of removing noise from the input steering torque T. The input filter unit 211 is configured, for example, with an LPF (Low Pass Filter) or a BPF (Band Pass Filter), but is not particularly limited to these. The filter used here may be configured with a first or second order filter. The following equation (1) shows an example of the transfer function of a first order filter. In each of the following equations, z -1 indicates the value of each variable one sample in the past.

[0032]

number

[0033] The torque hysteresis center calculation unit 212 calculates the steering torque T after the processing by the input filter unit 211 is applied. f and an arbitrary torque hysteresis width ΔT, a torque hysteresis central value Y is calculated. The value of the torque hysteresis width ΔT is set in advance and stored in a storage unit (not shown) or the like. In this embodiment, the torque hysteresis central value Y is calculated by the following equation (2). Note that the following equation is an example, and other conditions and equations may be used.

[0034] Condition 1: T f >Yz -1 In the case of +ΔT Y=T f -ΔT Condition 2: T f <Yz -1 In the case of -ΔT Y=T f +ΔT Condition 3: Condition 1 or Condition 2 does not apply, or in other cases Y=Yz -1 …(2)

[0035] The subtraction unit 213 subtracts the steering torque T f The torque hysteresis center value Y calculated by the torque hysteresis center calculation unit 212 is subtracted from (T f -Y).

[0036] The static friction gain unit 214 calculates a gain G as shown in the following equation (3) for the value obtained from the subtraction unit 213. s By multiplying this, the static friction compensation value F s Calculate the gain G s is predefined and its parameters are stored. F s =G s (T f -Y) …(3)

[0037] Figure 4 shows the steering torque T f The static friction compensation value F s 4 is a graph showing the change in torque value [Nm]. In Fig. 4, the vertical axis represents torque value [Nm] and the horizontal axis represents time [s]. In the torque value, + (plus) represents the value when the steering wheel 1 is rotated counterclockwise (CCW), and - (minus) represents the value when the steering wheel 1 is rotated clockwise (CW).

[0038] (Dynamic friction compensation section) 5 is a block diagram showing an example of the functional configuration of the dynamic friction compensation unit 220 according to this embodiment. The dynamic friction compensation unit 220 includes an encoding unit 221, an absolute value conversion unit 222, a steering state determination unit 223, a multiplication unit 224, and a dynamic friction gain unit 225.

[0039] The encoding unit 221 derives a code indicating the steering direction based on the steering speed ω. Here, the code is derived using the encoding function sign(ω), resulting in +1 (i.e., positive) or −1 (i.e., negative). For example, +1 indicates a counterclockwise steering direction, and −1 indicates a clockwise steering direction. This may also be reversed.

[0040] The absolute value conversion unit 222 derives the absolute value |ω| of the steering speed ω.

[0041] The steering state determination unit 223 determines the steering state by the following equation (4) using the absolute value |ω|, and sets a steering state determination flag L s The threshold value ω th is defined in advance and stored in a storage unit (not shown) or the like. Condition 1:|ω|≧ω th in the case of L s =1 (operating state) Condition 2: |ω|<ω th in the case of L s =0 (stationary state) ... (4)

[0042] The multiplication unit 224 multiplies the output of the encoding unit 221 and the steering state determination flag L output by the steering state determination unit 223. s The multiplication unit 224 outputs one of the values 1, 0, and −1.

[0043] The dynamic friction gain unit 225 multiplies the value obtained from the multiplication unit 224 by a gain G d By multiplying this, the dynamic friction compensation value F d That is, the dynamic friction compensation value F obtained by the dynamic friction compensation unit 220 is calculated. dcan be expressed by the following equation (5). F d =G d L s ·sign(ω) …(5)

[0044] Fig. 6 shows the dynamic friction compensation value F d 6 is a graph showing the change in steering speed [deg / s]. In Fig. 6, the vertical axis represents the steering speed [deg / s], and the horizontal axis represents time [s]. In the steering speed values, + (plus) represents the value of the counterclockwise (CCW) rotation of the steering wheel 1, and - (minus) represents the value of the clockwise (CW) rotation of the steering wheel 1.

[0045] (Fade switching section) The fade switching unit 230 according to this embodiment is configured to set the steering state determination flag L s According to the change in the value of , the dynamic friction compensation value F d and static friction compensation value F s Here, the dynamic friction compensation value F d The ratio of kinetic friction P d and the static friction compensation value F s The static friction ratio P s Shown in.

[0046] 7A and 7B are graphs for explaining the switching of the ratio of each compensation value by the fade switching unit 230. FIG. 7A shows the steering state determination flag L s 7(a), the vertical axis represents the change in the value of the steering state determination flag L s The horizontal axis indicates the time [ms]. s The value of P is between 0 and 1 as shown in the above equation (4), but in the graph it is shown as changing between 0 and 1 during the control period. d and the static friction ratio P s 7(b) is a graph showing the change in the ratio [%]. In Fig. 7(b), the vertical axis represents the percentage [%] and the horizontal axis represents the time [ms]. The time axes in Fig. 7(a) and Fig. 7(b) correspond to each other.

[0047] In this embodiment, L s If =0, P s = 100%, and P d =0%. Also, L s If =1, P s = 30%, and P d = 100%. Furthermore, in this embodiment, in order to reduce abrupt changes in the compensation value, the steering state determination flag L s For example, the steering state determination flag L is set at 10 ms in FIG. s The value of changes from 0 to 1. At that time, the static friction ratio P s The kinetic friction ratio P gradually decreases from 100% to 0%, but is limited to 30% and remains constant at this level. The change takes approximately 7 ms (9 to 16 ms). d The value gradually increases from 0% to 100%. The change takes about 10 ms (9 to 19 ms).

[0048] Similarly, at the timing of 30 ms in FIG. 7(a), the steering state determination flag L s The value of changes from 1 to 0. At that time, the static friction ratio P s is the steering state determination flag L s After a certain time has passed since the value of P changed, it gradually increases from 30% to 100%. At this time, the change takes about 7 ms (32 to 39 ms section). Also, the kinetic friction ratio P d is the steering state determination flag L s When the value of changes, it gradually decreases from 100% to 0%. At this time, the change takes about 10 ms (29-39 ms section).

[0049] Note that the ratio switching conditions shown in FIG. 7 are merely examples and are not limiting. For example, because static friction compensation is expected to have the effect of reducing torque fluctuations, the minimum value of the static friction ratio is set to 30% instead of 0%. However, the minimum value of the static friction ratio may be controlled to 0%. Also, although the fluctuation ratios of the static friction ratio and the kinetic friction ratio (i.e., the amount of change per unit time when the ratio changes from the maximum value to the minimum value, or from the minimum value to the maximum value) are set to be the same, they may also be controlled to be different. Furthermore, different fluctuation ratios may be used when increasing and decreasing the ratio.

[0050] In the example of Figure 7, the static friction ratio P s If the steering state determination flag L s In the example shown in FIG. 7, the increase begins not when the value changes from 1 to 0, but after a certain amount of time has passed since this timing. However, these timings may be made to coincide. In this case, the timing of the change may be adjusted according to the upper and lower limit values of the ratio and the fluctuation ratio. Also, in the example of FIG. 7, the fluctuation ratio is controlled linearly, i.e., constant, but the ratio may be changed according to the fluctuation ratio shown by a curve.

[0051] Then, the fade switching unit 230 determines the static friction ratio P s and the kinetic friction ratio P d Using the above, the Coulomb friction compensation value F is calculated using the following equation (6). c is derived. F c =P s F s +P d F d …(6)

[0052] Then, the EPS-ECU 32 calculates the derived Coulomb friction compensation value F c is reflected in the control value for the steering assist motor 33, the output voltage V mBy this adjustment, the steering system 110 is controlled so as to approach the steering characteristics of the hydraulic power steering device 100 shown in Fig. 1A, that is, so as to approach the steering feel of a manual column.

[0053] (Example of operation) Figure 8 shows the results of operation with and without Coulomb friction compensation according to this embodiment. In Figure 8, the horizontal axis represents the rotation angle [deg] of the steering wheel 1, with + (plus) values representing counterclockwise (CCW) rotation angles and - (minus) values representing clockwise (CW) rotation angles. The vertical axis represents the torque value [Nm], with + (plus) values representing counterclockwise (CCW) torque values and - (minus) values representing clockwise torque values.

[0054] As shown in FIG. 8, without Coulomb friction compensation according to this embodiment, an operating torque (friction torque) of ±1.3 Nm can be generated. On the other hand, with Coulomb friction compensation according to this embodiment, the operating torque is ±0.2 Nm, and the magnitude of this operating torque can be suppressed. Furthermore, without Coulomb friction compensation according to this embodiment, the fluctuation range near the upper and lower limit values of +1.3 Nm and −1.3 Nm is large, and the fluctuation range is approximately 0.5 Nm. On the other hand, with Coulomb friction compensation according to this embodiment, the fluctuation range near the upper and lower limit values of +0.2 Nm and −0.2 Nm is small. As a result, with Coulomb friction compensation according to this embodiment, steering performance can be improved even in a configuration that combines EPS and HPS.

[0055] FIG. 9 shows the measurement results of the manual column of the hydraulic power steering device shown in FIG. 1A. In FIG. 9, the horizontal axis represents the rotation angle [deg] of the steering wheel 1, with + (plus) values representing counterclockwise (CCW) rotation angles and - (minus) values representing clockwise (CW) rotation angles. The vertical axis represents torque values [Nm], with + (plus) values representing counterclockwise (CCW) torque values and - (minus) values representing clockwise (CW) torque values. Comparing FIG. 9 with FIG. 8, the configuration combining a conventional EPS and HPS exhibited large torque fluctuations. However, by applying Coulomb friction compensation according to this embodiment, the steering performance is closer to that of an HPS without an EPS. This makes it possible to suppress deterioration in steering performance.

[0056] As described above, according to this embodiment, in a configuration in which electric power steering and hydraulic power steering are combined, it is possible to reduce the deterioration of steering performance that occurs due to the structure of the electric power steering.

[0057] <Other embodiments> Furthermore, the configuration of the electric power steering device is not limited to the configuration shown in Fig. 1. For example, the electric power steering device may be configured with a steer-by-wire (SBW) mechanism in which the steering wheel 1 side, i.e., the steering mechanism side, and the steered road wheels 15 side, i.e., the steering mechanism side, are mechanically separated.

[0058] In the steer-by-wire function, the downstream side may be a hydraulic power steering device or an electric power steering device using a motor. Even in this case, control may be performed to compensate for friction caused by the configuration of the motor or reduction gear of the electric power steering device on the upstream side, for example.

[0059] Furthermore, the present invention can also be realized by supplying a program or application for realizing the functions of one or more of the above-described embodiments to a system or device via a network or storage medium, etc., and having one or more processors in the computer of that system or device read and execute the program.

[0060] In addition, the dynamic friction compensation value F d Although the above description has been given of a form in which is calculated based on equations (4) and (5), it may instead be calculated based on the following equations (7) and (8). Condition 1:|ω|≧ω th in the case of L s =1 (operating state) G ds =1 Condition 2: |ω|<ω th in the case of L s =0 (resting state) G ds = |ω| / ω th …(7) F d =G d G ds ·sign(ω) …(8) By doing this, the steering speed ω becomes ±ω th In the range of kinetic friction compensation value F d can be smoothly changed. In equation (7), G ds changes linearly, but G is controlled by a map that changes in a curve according to the steering speed. ds may be set.

[0061] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0062] As described above, the present specification discloses the following: (1) a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a control unit that controls the operation of the electric power steering device; Equipped with a control unit that derives a compensation value for Coulomb friction generated by a component of the electric power steering device, and outputs a control value for controlling the component using the compensation value. According to this configuration, in a configuration in which electric power steering and power steering of a steering mechanism are combined, it is possible to reduce deterioration in steering performance that occurs due to the structure of the electric power steering.

[0063] (2) the compensation value of the Coulomb friction is derived based on compensation values of static friction and kinetic friction of the part; The steering system according to (1), wherein the control unit derives the compensation value for the static friction based on a center value of hysteresis of torque applied to the steering shaft. According to this configuration, it is possible to derive a compensation value for static friction with higher accuracy based on torque hysteresis.

[0064] (3) The steering system according to (2), wherein the control unit derives the compensation value for the dynamic friction based on a steering speed of the steering shaft. According to this configuration, it is possible to more accurately derive a compensation value for dynamic friction based on the steering speed of the steering shaft provided with the electric power steering device.

[0065] (4) The control unit determining a steering state of the steering shaft; The steering system according to (3), characterized in that the compensation value for Coulomb friction is derived by switching the ratio between the compensation value for static friction and the compensation value for dynamic friction based on the determined steering state. This configuration makes it possible to adjust the ratio of the compensation values for dynamic friction and static friction based on the steering state, thereby enabling the compensation value for Coulomb friction to be derived with higher accuracy.

[0066] (5) The steering system according to (4), wherein the minimum ratio of the compensation value for static friction is different from the minimum ratio of the compensation value for dynamic friction. This configuration makes it possible to combine the compensation value for dynamic friction and the compensation value for static friction in an appropriate ratio.

[0067] (6) The steering system according to (4) or (5), characterized in that the rate of change of the ratio per unit time is the same for the rate of the compensation value for static friction and the rate of the compensation value for dynamic friction. According to this configuration, it is possible to commonly control the fluctuation ratio of the compensation value for dynamic friction and the compensation value for static friction.

[0068] (7) The steering system according to (4) or (5), characterized in that the amount of change in the ratio per unit time differs between the ratio of the compensation value for static friction and the ratio of the compensation value for dynamic friction. According to this configuration, it is possible to control the fluctuation ratios of the compensation value for dynamic friction and the compensation value for static friction using different values.

[0069] (8) The steering system according to any one of (1) to (7), wherein the electric power steering device includes a motor and a reducer as the components. This configuration makes it possible to control the Coulomb friction caused by the motor and reducer included in the electric power steering device.

[0070] (9) a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; A method for controlling a steering system comprising: A control method for a steering system, comprising: deriving a compensation value for Coulomb friction generated by a component constituting the electric power steering device; and using the compensation value to output a control value for controlling the component. According to this configuration, in a configuration in which electric power steering and power steering of a steering mechanism are combined, it is possible to reduce deterioration in steering performance that occurs due to the structure of the electric power steering.

[0071] (10) a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a computer for controlling a steering system comprising: A program for causing the electric power steering device to function as a control unit that derives a compensation value for Coulomb friction generated by a component of the device and uses the compensation value to output a control value for controlling the component. According to this configuration, in a configuration in which electric power steering and power steering of a steering mechanism are combined, it is possible to reduce deterioration in steering performance that occurs due to the structure of the electric power steering. [Explanation of symbols]

[0072] 1...Steering wheel 2...Steering shaft 4a, 4b...Universal joint 5...Intermediate shaft 6...Bevel gear 7...Rotary control valve 8...Hydraulic pump 9. Tank 10...Hydraulic chamber 11...Steering box 12a, 12b...Connection 13a, 13b...Tie rod 14a, 14b...hub unit 15a,15b...Steering wheel 30...Functional part 31...Torque sensor 32…EPS-ECU(Electronic Control Unit) 33...Steering assist motor 34...Warm 35...worm wheel 40...Vehicle ECU 100...Hydraulic power steering device 110...Steering system

Claims

1. a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a control unit that controls the operation of the electric power steering device; Equipped with the control unit derives a compensation value for Coulomb friction generated by a component constituting the electric power steering device, and outputs a control value for controlling the component using the compensation value, the compensation value of the Coulomb friction is derived based on compensation values of static friction and kinetic friction of the part; the static friction compensation value is derived based on a center value of hysteresis of torque with respect to the steering shaft; 10. A steering system according to claim 9, wherein the compensation value for dynamic friction is derived based on a steering speed for the steering shaft.

2. The control unit deriving a discrimination flag for discriminating whether the steering state of the steering shaft is in a moving state or a stationary state; 2. The steering system according to claim 1, wherein the compensation value for Coulomb friction is derived by switching a ratio between the compensation value for static friction and the compensation value for dynamic friction based on the discrimination flag indicating the determined steering state.

3. 3. The steering system according to claim 2, wherein the minimum percentage of the compensation value for static friction is different from the minimum percentage of the compensation value for dynamic friction.

4. 4. The steering system according to claim 2, wherein the rate of change of the ratio per unit time is the same for the ratio of the compensation value for static friction and the ratio of the compensation value for dynamic friction.

5. 4. The steering system according to claim 2, wherein the rate of change of the ratio per unit time differs between the rate of the compensation value for static friction and the rate of the compensation value for dynamic friction.

6. 6. The steering system according to claim 1, wherein the electric power steering device includes a motor and a reducer as the components.

7. a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; A method for controlling a steering system comprising: deriving a compensation value for Coulomb friction generated by a component constituting the electric power steering device, and outputting a control value for controlling the component using the compensation value; the compensation value of the Coulomb friction is derived based on compensation values of static friction and kinetic friction of the part; the static friction compensation value is derived based on a center value of hysteresis of torque with respect to the steering shaft; 10. A method for controlling a steering system, comprising: deriving the compensation value for dynamic friction based on a steering speed for the steering shaft.

8. a steering mechanism including a steering shaft; a steering mechanism that steers steered wheels in conjunction with rotation of the steering shaft; a power steering device provided in the steering mechanism; an electric power steering device provided in the steering mechanism; a computer for controlling a steering system comprising: a program for causing the electric power steering device to function as a control unit that derives a compensation value for Coulomb friction generated by a component of the device, and outputs a control value for controlling the component using the compensation value, the compensation value of the Coulomb friction is derived based on compensation values of static friction and kinetic friction of the part; the static friction compensation value is derived based on a center value of hysteresis of torque with respect to the steering shaft; The compensation value for dynamic friction is derived based on a steering speed of the steering shaft.

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