Steering system

Abstract

We provide a highly practical steer-by-wire steering system. [Solution] In a steer-by-wire steering system installed in a vehicle equipped with a drive simulator, the operating device 18 is used to operate the simulated vehicle that is the target of operation in the drive simulator when the drive simulator is functioning, and the controllers 40 and 42 are configured to apply an operating reaction force Tc, which includes a vertical acceleration dependent component Tci based on a signal from the drive simulator regarding the vertical acceleration Gz of the simulated vehicle, to the operating member 10 via a reaction force application device 12 in that simulator mode. When the simulated vehicle deviates from the course, the driver can appropriately feel that deviation.

Description

Technical Field

[0001] The present invention relates to a steer-by-wire type steering system mounted on a vehicle.

Background Art

[0002] In recent years, it has been considered to mount a steer-by-wire type steering system (hereinafter sometimes referred to as a "steer-by-wire system") on a vehicle. Specifically, a system in which an operation member such as a steering wheel and a steering device that steers wheels are mechanically separated. In the steer-by-wire system, a reaction force applying device that applies a reaction force to the operation of the operation member is provided in order to make the driver feel the steering operation.

[0003] On the other hand, it has also been considered to enable a driver to enjoy a game using a driving simulator (hereinafter sometimes simply referred to as a "simulator") in the vehicle interior when the vehicle is not actually running. In that case, it has also been considered to use the operation member of the steer-by-wire system for the operation of a vehicle (hereinafter sometimes referred to as a "simulated vehicle") that is the object of driving in the simulator. When using the operation member for the operation of the simulated vehicle, it is desirable to apply the above-described operation reaction force as in actual driving. Regarding the operation reaction force of the simulator, there are techniques as described in the following patent documents.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in the above-mentioned patent document, in addition to a restoring force to return the operating member to a neutral position, vibrations based on the vehicle speed and engine speed of the simulated vehicle are applied as an operating reaction force to provide an operating feel close to that of actual driving. There is still much room for improvement in the methods for providing an operating feel close to that of actual driving, and the practicality of a steer-by-wire system that can be used to operate a simulated vehicle in a simulator can be improved by making some improvements to the application of the operating reaction force. The present invention has been made in view of such circumstances, and aims to provide a highly practical steer-by-wire type steering system. [Means for solving the problem]

[0006] To solve the above problems, the steering system of the present invention is An operating device having an operating member operated by the driver and a reaction force applying device that applies an operating reaction force which is a reaction force to the operation of the operating member, A steering device that steers the wheels using an electric motor, which is a steering motor, as the driving source, A controller that controls the steering device and the reaction force application device. A steer-by-wire steering system equipped with a driving simulator, which is installed in a vehicle equipped with a driving simulator, The aforementioned operating device is used to operate the simulated vehicle that is the target of operation in the drive simulator in the simulator mode in which the drive simulator is functioning. The controller is configured to, in its simulator mode, cause the reaction force application device to apply an operating reaction force that includes a vertical acceleration-dependent component based on a signal from the drive simulator regarding the vertical acceleration of the simulated vehicle. [Effects of the Invention]

[0007] According to the steering system of the present invention, in simulator mode, an operating reaction force including a component based on the vertical acceleration occurring in the simulated vehicle is applied to the operating member. Vertical acceleration can indicate changes in road surface conditions (the road surface on which the simulated vehicle travels), and according to the steering system of the present invention, it is possible to make the driver feel these changes in road surface conditions. For example, in a simulation in which a simulated vehicle travels on a circuit, when the simulated vehicle deviates from the course, it is possible to easily give the driver a sense of realism regarding that deviation. (Aspects of the Invention)

[0008] The "steer-by-wire steering system" in this invention is not particularly limited in its configuration, and a general configuration can be used. The "driving simulator" operates a "simulated vehicle," which is a vehicle that operates in a virtual space or virtual environment. By using this simulator, the driver can enjoy games, etc., when the vehicle is not actually running, such as when it is charging. Note that in "simulator mode," when the simulator is functioning, the actual wheels are not steered by the steering mechanism.

[0009] The "vertical acceleration-dependent component," which is one component of the operating reaction force, is a component that can only be generated in simulator mode. Since the "vertical acceleration" of the simulated vehicle is an indicator of the vehicle's driving state and the condition of the road surface it is driving on (road surface characteristics), this component can be considered to reflect those driving states and road surface characteristics. By adopting this vertical acceleration component, as mentioned above, it is possible to give the driver a sense of realism, for example, when the simulated vehicle deviates from the course.

[0010] The advantages of using signals related to vertical acceleration to give the driver a sense of realism can be considered as follows: For example, if we consider a simulated vehicle deviating from its course, the controller could simply receive a signal from the simulator indicating that the course has deviated and, based on that signal, vibrate the control member using the operating reaction force. However, that vibration would be of a single nature. In contrast, by using signals related to vertical acceleration, it becomes possible to apply various types of vibrations to the control member by changing the vibration period (fluctuation frequency), amplitude, etc., of that vertical acceleration. In other words, by using signals related to vertical acceleration, the period and amplitude of the vibration generated in the control member can be easily and dynamically changed. Furthermore, if, for example, the vehicle is equipped with an active suspension system, it is also possible to use that signal to apply various vibration actions to the vehicle body itself through that system.

[0011] The vertical acceleration-dependent component may be determined based on vertical accelerations whose fluctuating frequencies fall within a set range. In other words, vertical accelerations in a certain frequency band may be extracted, for example, using a bandpass filter, and the vertical acceleration-dependent component may be determined based on these extracted vertical accelerations. By basing the fluctuating frequency on vertical accelerations within a set range, it becomes possible to provide the driver with an appropriate sense of realism. The "set range" in this case may be tuned considering how easily vibrations are transmitted to the driver, or it may be set based on the unsprung resonance frequency of the vehicle on which the system is installed. Specifically, for example, it may be set to around a few Hz to 30 Hz. Furthermore, it is desirable that the set range be varied based on the driving speed of the simulated vehicle (hereinafter sometimes referred to as "vehicle speed"). More specifically, considering that fluctuations in vertical acceleration are caused by irregularities in the road surface on which the simulated vehicle travels, the period of these fluctuations depends on the vehicle speed of the simulated vehicle, so it is desirable that the set range be set higher the higher the vehicle speed.

[0012] Furthermore, it is desirable that the vertical acceleration-dependent component be set to 0 when the simulated vehicle's speed is below the set low speed, and that it be reduced in proportion to the increase in speed when the simulated vehicle's speed exceeds the set high speed. This is because, in the low speed range (e.g., speed range below 10 km / hr), there is no need to vibrate the operating member, and it is desirable to consider the discomfort caused by the operation of the operating member, while in the high speed range (e.g., speed range exceeding 80-100 km / hr), it is desirable to consider the possibility that the driver may find the vibration of the operating member bothersome. In addition, out of consideration for the sudden operation of the operating member, it is desirable to limit the vertical acceleration-dependent component to below a set value. This set value can be determined, for example, by considering the magnitude of the impact on the driver, the discomfort, etc.

[0013] The operating reaction force may include various components. Specifically, for example, the central component of the operating reaction force may include a "steering force-dependent component." The "steering force" is the force required to steer the wheels or maintain the amount of steering (steering angle) of those wheels. If the steering device has a steering rod (rack bar) connecting the left and right wheels, it can be considered as the axial force acting on that steering rod. Therefore, the steering force may be called the axial force, and the steering force-dependent component may be called the axial force-dependent component. As explained earlier, in simulator mode, the steering force is the steering force for steering the wheels of the simulated vehicle, i.e., the simulated steering force.

[0014] In the "driving mode," which is the mode in which the vehicle actually runs, the steering force is generally proportional to the torque generated by the steering motor. That is, it is generally proportional to the current supplied to the steering motor. Therefore, in the driving mode, the steering force-dependent component may be determined based on that current. In contrast, in the simulator mode, no current is supplied to the steering motor, so the steering force-dependent component can be determined based on commands from the simulator, more specifically, on commands related to the steering force. Incidentally, the command may be a command for the value of the steering force-dependent component itself, or it may be a command for any value that indicates the steering force.

[0015] The "correction based on the operating speed of the operating member" may be performed, for example, to compensate for delays in commands from the simulator. Since the simulator is merely an optional piece of equipment for the vehicle, in other words, a recreational piece of equipment, it is common to communicate with the system's controller using general-purpose communication means such as CAN (controllable area network or car aera network). Therefore, in that case, the above commands are likely to experience delays. Since this delay depends on the operating speed of the operating member, the above correction is suitable for preventing such delays. Incidentally, in the case of communication within the system, for example, when the controller is divided into a part that controls the reaction force application device and a part that controls the steering device, it is common to communicate between these parts via a dedicated high-speed communication line, and for example, signals regarding the current supplied to the steering motor in driving mode are designed not to experience delays.

[0016] The above correction may be made, for example, so that the operating reaction force increases as the operating speed of the operating member increases. Such a correction is suitable for mitigating the effect of the above-mentioned delay, considering that the above-mentioned delay increases as the operating speed increases.

[0017] The above correction may be performed, for example, by adding a compensation component determined based on the operating speed of the operating member to a component determined based on a steering force command from the simulator (hereinafter sometimes referred to as the "steering force command-dependent component" or simply the "command-dependent component"). In that case, as will be explained in detail later, the compensation component may be determined taking into account the driver's operating force applied to the operating member. Specifically, for example, the compensation component may be determined so that it becomes smaller as the operating force increases. The compensation component may also be determined taking into account the driving speed of the simulated vehicle that is the subject of operation in the simulator. Specifically, for example, the compensation component may be determined so that it becomes smaller as the driving speed decreases. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram showing the overall configuration of the steering system of the embodiment. [Figure 2] This is a block diagram showing the functional configuration of the controller of the steering system of the embodiment. [Figure 3] This is a block diagram showing details of a functional unit that determines a component of an operating reaction force based on a command or signal from a drive simulator in the functional configuration of the controller. [Figure 4] This is a graph showing a map referred to when determining a component of an operating reaction force based on a command regarding a steering force from a drive simulator. [Figure 5] This is a graph showing a map referred to when determining a component of an operating reaction force based on a signal regarding the vertical acceleration of a simulated vehicle from a drive simulator.

Mode for Carrying Out the Invention

[0019] Hereinafter, as a mode for carrying out the present invention, a steering system which is an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention can be implemented in various forms obtained by making various changes and improvements based on the knowledge of those skilled in the art, in addition to the following embodiments and the forms described in the section of 〔Aspects of the Invention〕 above.

Embodiment

[0020] [1] Overall Configuration of Steering System The steering system of this embodiment (hereinafter sometimes referred to as "this steering system" or "this system") is a steer-by-wire type steering system that can steer the wheels without the driver's operating force applied to the operating member. As shown in Figure 1, it is composed of a steering wheel 10 which is an operating member, a reaction force actuator 12 which is a reaction force applying device to which the steering wheel 10 is connected, and a steering actuator 16 which is a steering device that connects the left and right wheels 14, each of which is a steering wheel, and steers them together. The steering wheel 10 is rotated by the driver, and the reaction force actuator 12 is configured to receive this operation and to apply a reaction force (hereinafter sometimes referred to as "operating reaction force") to the steering wheel 10, or more specifically, to the operation of the steering wheel 10. The operating device 18 of this steering system is composed of the steering wheel 10 and the reaction force actuator 12.

[0021] The reaction force actuator 12 comprises a steering column 20 supported by the reinforcement of the instrument panel, a steering shaft 22 rotatably held in the steering column 20, and a reaction force motor 24, which is an electric motor for applying rotational torque to the steering shaft 22 via a power transmission mechanism. The steering wheel 10 is attached to the rear end of the steering shaft 22. The power transmission mechanism, although a detailed structural description is omitted, comprises a worm attached to the motor shaft of the reaction force motor 24 and a worm wheel attached to the steering shaft 22 that meshes with the worm. The reaction force motor 24 is a three-phase brushless DC motor and functions as the drive source for the reaction force actuator 12. The torque generated by the reaction force motor 24 applies a reaction force torque as an operating reaction force to the steering wheel 10 connected to the steering shaft 22.

[0022] The steering actuator 16 comprises a generally cylindrical housing 30 supported by the chassis in an orientation extending to the left and right, a steering rod (rack bar) 32 held in the housing 30 so as to be non-rotatable and movable from side to side, and a pair of tie rods 34 connected to the left and right ends of the steering rod 32 via ball joints. The ends of each tie rod 34 are connected to the wheels 14 via ball joints. More specifically, each tie rod 34 is connected via ball joints to the knuckle arm of a steering knuckle, which is held rotatably on the suspension arm and holds the wheel 14 so as to be rotatable.

[0023] The steering rod 32 has a screw groove 36 formed therein. Although not shown in the illustration, a nut that holds bearing balls and screws into the screw groove 36 is held inside the housing 30 so as to be immovable from side to side but rotatable. In other words, the steering rod 32 and the nut constitute a ball screw mechanism. An electric motor, the steering motor 38, is attached to the housing 30, and the steering motor 38 rotates the nut via a power transmission mechanism. Incidentally, although not shown in the illustration, the power transmission mechanism includes a pulley attached to the motor shaft of the steering motor 38 and a timing belt wrapped around the pulley and the outer circumference of the nut. The steering motor 38 is a three-phase brushless DC motor and functions as a drive source for the steering actuator 16. By rotating the steering motor 38, the steering rod 32 is moved from side to side, and the left and right wheels 14 are steered together.

[0024] The reaction force actuator 12 is controlled by a reaction force electronic control unit (hereinafter sometimes referred to as "reaction force ECU") 40 attached to the reaction force motor 24. The reaction force ECU 40 consists of a computer consisting of a CPU, ROM, RAM, etc., and an inverter which is the driver (drive circuit) for the reaction force motor 24, and is powered by a battery. Similarly, the steering actuator 16 is controlled by a steering electronic control unit (hereinafter sometimes referred to as "steering ECU") 42 attached to the steering motor 38. The steering ECU 42 consists of a computer consisting of a CPU, ROM, RAM, etc., and an inverter which is the driver (drive circuit) for the steering motor 38, and is powered by a battery.

[0025] The reaction force ECU 40 and the steering ECU 42 work in coordination with each other, and together they constitute a single controller for the steering system. Therefore, the reaction force ECU 40 and the steering ECU 42 are connected by a dedicated high-speed communication line 44. Incidentally, both are also connected to the CAN (car area network or controllable area network) 46 provided by the vehicle. Furthermore, a vehicle speed sensor 48 for detecting the actual vehicle speed r, which is the actual driving speed of the vehicle, is also connected to this CAN 46.

[0026] In relation to control, the reaction actuator 12, although a detailed structural description will be omitted, has an operating torque sensor 50 that detects the amount of twist of the steering shaft 22 to detect the operating torque To, which is the operating force applied by the driver to the steering wheel 10. It also has an operating angle sensor 52 that detects the operating angle δ of the steering wheel 10 by detecting the rotation angle of the steering shaft 22, and a reaction motor rotation angle sensor 54 for detecting the rotation angle (rotation phase) θmc of the reaction motor 24 for purposes such as switching the energized phase.

[0027] Regarding the steering actuator 16, since there is a specific relationship between the steering angle of the wheel 14 and the lateral movement position of the steering rod 32, it has a steering angle sensor 56 that detects the movement position of the steering rod 32 in order to detect the steering angle of the wheel 14. Briefly, a rack 58 is formed on the steering rod 32, and a pinion shaft 60 that meshes with the rack 58 is held in the housing 30. The steering angle can also be the toe angle of the wheel 14, but in this system, the rotation angle of the pinion shaft 60 detected by the steering angle sensor 56 is treated as the steering angle ω of the wheel 14. The steering actuator 16 also has a steering motor rotation angle sensor 62 for detecting the rotation angle (rotation phase) θms of the steering motor 38 for purposes such as switching the energized phase.

[0028] Vehicles equipped with this system are fitted with a driving simulator (hereinafter sometimes simply referred to as "simulator") 70. The simulator 70 is a device that drives a simulated vehicle, which is a virtual target of operation, within a virtual environment (virtual space), and realizes as video the changes in the scenery (environmental components) etc. that can be seen from the simulated vehicle. For example, when the vehicle is stopped, such as while charging, the driver of the vehicle can enjoy games etc. using the simulator 70.

[0029] The simulator 70 consists of a computer-based simulator unit 72, a goggle-type head-mounted display (hereinafter sometimes simply referred to as "display") 74 for the driver to view images from the perspective of a simulated vehicle, and a simulation feasibility determination device 76 for determining whether the simulator 70 can operate. Incidentally, in this simulator 70, the head-mounted display 74 is used as a means of realizing images, but various means can be used, such as a head-up display that projects images onto the windshield of the vehicle, a large display installed in front of the vehicle, or a screen installed in front of the vehicle with a projector for projecting onto that screen.

[0030] In the simulation, the operation of the simulated vehicle is controlled by this system, specifically by the system's control device 18. Therefore, the simulator body 72 and the simulation permission determination device 76 are connected to CAN46, and communication between the simulator 70 and this system is conducted via CAN46. In addition, since the accelerator pedal 80 and brake pedal 82 of the simulated vehicle are also used to operate the vehicle, an accelerator pedal operation amount sensor 84 for detecting the accelerator pedal operation amount λa, which is the amount of operation of the accelerator pedal 80, and a brake pedal operation amount sensor 86 for detecting the brake pedal operation amount λb, which is the amount of operation of the brake pedal 82, are also connected to CAN46.

[0031] [2] Controller functions The controller of this steering system, which consists of a reaction force ECU 40 and a steering ECU 42, has a functional configuration as shown in the functional block diagram in Figure 2. This functional configuration is realized by a computer executing a predetermined program. Most of the inputs to or outputs from each component (functional unit) shown in the figure are signals indicating values ​​such as torque, its components, steering angle, and operating angle. However, to avoid redundancy in the explanation, in the following explanation, we will simply say that torque, its components, steering angle, and operating angle are input to or output from each component. Furthermore, in consideration of ease of understanding, the following will explain the steering control function by the steering ECU 42 in the driving mode, which is the mode in which the vehicle is actually driving, the reaction force control function by the reaction force ECU 40, and the reaction force control by the reaction force ECU 40 in the simulator mode, in which a drive simulation by the simulator 70 is being performed.

[0032] (a) Steering control in driving mode Steering control is the control of the steering angle ω of the wheel 14 steered by the steering actuator 16. The steering ECU 42, acting as the steering control unit, has a target steering angle determination unit 100, a steering torque determination unit 102, and a steering energization control unit 104. In reaction force control and steering control, the vehicle speed v, which is the vehicle's travel speed, is used, but the vehicle speed v used differs between the driving mode and the simulator mode. Specifically, in the driving mode, it is the actual vehicle speed vr, which is the actual travel speed of the vehicle, and in the simulator mode, it is the simulator vehicle speed vs, which is the travel speed of the simulated vehicle in the simulator 70. Therefore, the steering ECU 42 has a vehicle speed selection unit 105 to selectively adopt either the actual vehicle speed vr detected by the vehicle speed sensor 48 or the simulator vehicle speed vs transmitted from the simulator main unit 72 as the vehicle speed v. The vehicle speed selection unit 105 selects either the actual vehicle speed vr or the simulator vehicle speed vs based on the simulation permission signal Sa transmitted from the simulation permission determination unit 76. Specifically, in driving mode, simulation is prohibited and the actual vehicle speed vr is selected, while in simulation mode, simulation is permitted and the simulator vehicle speed vs is selected.

[0033] In the control of this steering system, the steering angle ω is used as the amount of steering of the wheel 14. However, this steering angle ω is not the value detected by the steering angle sensor 56, but rather a value converted based on the steering motor rotation angle θms detected by the steering motor rotation angle sensor 62. Therefore, the steering ECU 42 has a steering angle conversion unit 106 that converts the steering motor rotation angle θms detected by the steering motor rotation angle sensor 62 into a steering angle ω. Since the cumulative amount of the steering angle ω and the steering motor rotation angle θms has a relationship according to a predetermined reduction ratio, the steering angle conversion unit 108 performs the conversion based on that reduction ratio.

[0034] The target steering angle determination unit 100 determines the target steering angle ω, which is the control target for the steering angle ω, based on the operating angle δ converted by the operating angle conversion unit 108 of the reaction force ECU 40, which will be described later. *The steering system determines the steering gear ratio γ, that is, the ratio of the steering angle ω to the operating angle δ, according to the vehicle speed v. The target steering angle determination unit 100 determines the target steering angle ω by referring to the stored map data based on the operating angle δ and the vehicle speed v. * This is determined. Incidentally, the method for changing the steering gear ratio γ is common, so its explanation will be omitted here. The target steering angle ω * This is also used as the target steering angle of the simulated vehicle in the simulation, and is therefore transmitted via CAN46 to the simulator 70, or more specifically, the simulator main unit 72.

[0035] The steering torque determination unit 102 is a functional unit that determines the steering torque Ts required to steer the wheel 14. The steering torque Ts can be thought of as, for example, the torque that the steering motor 38 should generate. Specifically, it is calculated by comparing the current actual steering angle ω converted by the steering angle conversion unit 106 with the target steering angle ω * Based on this, the target steering angle ω * The steering angle deviation Δω, which is the deviation of the steering angle ω relative to the given value, is identified, and based on this steering angle deviation Δω, the steering torque Ts that should be generated is determined according to the PID feedback control law. This determination method following the feedback control law is a general one, and its explanation is omitted here.

[0036] The steering power supply control unit 104 includes an inverter, which is the drive circuit (driver) for the steering motor 38. Based on the determined steering torque Ts, the steering power supply control unit 104 determines the steering current Is, which is the current to be supplied to the steering motor 38, and supplies this steering current Is from the inverter to the steering motor 38. The steering ECU 42 has a current sensor 110 for detecting the steering current Is that is actually being supplied.

[0037] In simulator mode, since there is no need to steer the vehicle's wheels 14, the steering torque determination unit 102 does not determine the steering torque Ts, and no signal regarding the steering torque Ts is transmitted to the steering energization control unit 104. Whether or not to perform this determination and transmission is determined based on the simulation feasibility signal Sa described earlier.

[0038] (b) Reaction force control in driving mode The reaction force control unit, reaction force ECU 40, controls the reaction force torque Tc to be applied to the steering wheel 10 by the reaction force actuator 12, which is a reaction force application device. The reaction force ECU 40 has an assist component determination unit 112, a steering force dependent component determination unit 114, and a vertical acceleration dependent component determination unit 115, which determine the assist component Tca, the steering force dependent component Tcs, and the vertical acceleration dependent component Tci, which will be explained in detail in the section on reaction force control in the simulator mode later, respectively, and are components of the reaction force torque Tc.

[0039] The steering force-dependent component Tcs is determined by mediating between the steering angle-dependent component Tcs and the estimated actual steering force-dependent component Tce. The estimated actual steering force-dependent component Tce is determined to be the steering current-dependent component Tcb in driving mode, and to the simulation component Tcc, which will be explained in detail later, in simulator mode. Since the steering force-dependent component Tcs includes these components, the steering force-dependent component determination unit 114 includes a steering angle-dependent component determination unit 116, a simulation component determination unit 118, a steering current-dependent component determination unit 120, part of a component switcher 122, weighters 124 and 126, and an adder 128.

[0040] In the control of this steering system, the steering angle δ is used as the amount of steering of the steering wheel 10. Therefore, similar to the steering ECU 42, the reaction force ECU 40 has a steering angle conversion unit 108 that converts the reaction force motor rotation angle θmc detected by the reaction force motor rotation angle sensor 54 into a steering angle δ. Since the integrated amount of the steering angle δ and the reaction force motor rotation angle θmc has a relationship according to a predetermined reduction ratio, the steering angle conversion unit 108 performs the conversion based on that reduction ratio.

[0041] Regarding the determination of each component of the reaction torque Tc described above, if we explain it in order with respect to the driving mode, the assist component Tca is a component similar to the assist force in so-called power steering, and the assist component determination unit 112 determines the assist component Tca based on the operating torque To and vehicle speed v detected by the operating torque sensor 50. Simply put, the assist component Tca is determined to be a larger value the larger the operating torque To is, and when the vehicle speed v is high, it is determined to be a smaller value in order to make the operating feel that the driver receives in response to the operation of the steering wheel 10 heavier, and when the vehicle speed v is low, it is determined to be a larger value in order to make the operating feel lighter. The direction of the assist component Tca is the same as the direction of operation of the steering wheel 10, that is, the steering operation direction.

[0042] The steering force-dependent component Tcs can be considered the central component of the reaction torque Tc, and broadly speaking, it is the component that allows the driver to feel the steering force, which is the force required to steer the wheels 14. The steering force-dependent component Tcs can also be considered an axial force-dependent component, that is, a component based on the force (axial force) acting on the steering rod 32 of the steering actuator 16 in its axial direction. The steering force-dependent component Tcs is generally a component in the direction opposite to the steering operation direction.

[0043] The steering angle-dependent component Tcd, which is one component of the steering force-dependent component Tcs, can be considered as an ideal steering force determined based on the vehicle model, that is, a force that roughly corresponds to the self-aligning torque. In other words, it can be considered as a steering force that does not reflect road surface information such as unevenness in the road surface that does not affect the lateral behavior of the vehicle, or steps that do affect the lateral behavior of the vehicle. The steering angle-dependent component determination unit 116, although a detailed explanation will be omitted, determines the target steering angle ω determined by the target steering angle determination unit 100 of the steering ECU 42. * Based on the vehicle speed v, the steering angle-dependent component Tcd is determined according to a predetermined map. The steering angle-dependent component Tcd is the target steering angle ω * The larger the value, the larger the resulting value, and the higher the vehicle speed v, the larger the resulting value.

[0044] As explained earlier, the simulation component Tcc determined by the simulation component determination unit 118 is the estimated actual steering force-dependent component Tce in simulator mode; therefore, the simulation component determination unit 118 and the simulation component Tcc will be explained later. The switching between the simulation component Tcc and the steering current-dependent component Tcb is performed by the component switcher 122. This switching is performed based on the simulation feasibility signal Sa explained earlier.

[0045] The steering current-dependent component Tcb, which is the estimated actual steering force-dependent component Tce in driving mode, differs from the steering angle-dependent component Tcd in that it reflects the influence of the road surface information mentioned above. In other words, it is a component that allows the driver to feel, for example, the force acting on the wheel 14 from the road surface. The steering current-dependent component determination unit 120, simply put, determines the steering current-dependent component Tcb by multiplying the actual steering current Is detected by the current sensor 110 by a set current-to-steering force conversion gain Kb.

[0046] The mediation between the steering angle-dependent component Tcd and the estimated actual steering force-dependent component Tce is performed as follows: The estimated steering angle-dependent component Tce is multiplied by a weighting coefficient α (0 < α < 1) by the weighting device 124, and the steering angle-dependent component Tcd is multiplied by the weighting coefficient α divided by 1 by the weighting device 126. These multipliers are then added together by the adder 128 to determine the steering force-dependent component Tcs. A detailed explanation is omitted, but the weighting coefficient α may be set to be fixed, or it may be set to change depending on various factors such as vehicle speed v, the condition of the road surface on which the vehicle is traveling, and the vehicle's driving condition.

[0047] The assist component Tca determined by the assist component determination unit 112 and the steering force-dependent component Tcs determined by the steering force-dependent component determination unit 114 are combined by the combiner 130 to determine the reaction force torque Tc. The determined reaction force torque Tc is input to the reaction force energization control unit 132. The reaction force energization control unit 132 is configured to include an inverter, which is the drive circuit (driver) for the reaction force motor 24. Based on the reaction force torque Tc, the reaction force energization control unit 132 determines the reaction force current Ic, which is the current to be supplied to the reaction force motor 24, and supplies that reaction force current Ic from the inverter to the reaction force motor 24.

[0048] (c) Reaction force control in simulator mode As explained earlier, in simulator mode, the simulation component Tcc is determined as the estimated actual steering force-dependent component Tce, replacing the steering current-dependent component Tcb mentioned above. In addition, in simulator mode, the vertical acceleration-dependent component Tci is added as one component of the reaction force torque Tc. Aside from these differences, the reaction force control in simulator mode is the same as the reaction force control in driving mode. The functions of the simulation component Tcc and the simulation component determination unit 118 that determines it, and the functions of the vertical acceleration-dependent component Tci and the vertical acceleration-dependent component determination unit 115 that determines it will be explained below with reference to the block diagram in Figure 3.

[0049] i) Simulation components and simulation component determination unit As shown in the block diagram of Figure 3(a), the simulation component determination unit 118 receives the simulator command value Θ transmitted from the simulator main unit 72 via CAN 46. This simulator command value Θ indicates the estimated actual steering force-dependent component Tce that should be generated by the simulator 70, and the simulator command component Tch is determined by multiplying it by the converted gain Kc using the converted gain multiplier 140. Incidentally, if the simulator command value Θ is in the same units as the reaction force torque Tc and its components, in other words, if the simulator command component Tch is input directly from the simulator main unit 72, then there is no need to provide this converted gain multiplier 140.

[0050] As mentioned earlier, since the simulator command value Θ is transmitted from the simulator main unit 72 via communication, a delay, or in other words, a phase delay, occurs. Therefore, the simulation component determination unit 118 performs a correction process using the compensation component Tcg described below in order to eliminate or mitigate this delay.

[0051] The simulation component determination unit 118 receives the operating angle δ converted by the operating angle conversion unit 108. The simulation component determination unit 118 has a differentiator 142, which calculates the operating speed δ' (=dδ / dt) of the handle 10, which is the operating member. The basic compensation component determination unit 144 determines the basic compensation component Tcf based on the operating speed δ' by referring to the basic compensation component determination map shown as a graph in Figure 4(a). The basic compensation component determination map is set so that the basic compensation component Tcf increases as the operating speed δ' increases, taking into account that the delay is greater as the operating speed δ' increases.

[0052] The basic compensation component determination map may be set so that the basic compensation component Tcf changes linearly with respect to the operating speed δ', as shown by the dashed line in the graph. However, if the basic compensation component Tcf increases, the damping component of the reaction torque Tc increases, impairing the clarity of the feel of operating the handle 10 and leading to a decrease in the realism of the simulation. Therefore, as shown by the solid line in the graph, it is also possible to adopt a nonlinear basic compensation component determination map such that the basic compensation component Tcf becomes small in the region where the delay is relatively small with respect to the operating speed δ', that is, in the region where the operating speed δ' is low. Incidentally, if the basic compensation component Tcf is to change linearly with respect to the operating speed δ', it is also possible to determine the basic compensation component Tcf by a fixedly set gain without adopting a map.

[0053] In the simulation component determination unit 118, the basic compensation component Tcf determined by the basic compensation component determination unit 144 is multiplied by the contribution change gain Ka in the contribution change gain multiplier 146 to determine the final basic compensation component Tcf. This contribution change gain Ka changes the contribution of the basic compensation component Tcf in the simulation component Tcc. For example, it is possible to change the magnitude of the basic compensation component Tcf according to the vehicle speed of the simulated vehicle in the simulation, the road surface on which the simulated vehicle is traveling, the driving conditions of the simulated vehicle, etc. However, if the basic compensation component determination map is designed to incorporate the contribution change function, this contribution change gain multiplier 146 does not need to be provided.

[0054] The simulation component determination unit 118 includes a correction unit 148, which determines the compensation component Tcg by multiplying the determined basic compensation component Tcf by the operating torque-dependent gain Ko and the vehicle speed-dependent gain Kv.

[0055] The operating torque-dependent gain Ko is set taking into account other effects caused by an increase in the compensation component Tcg. More specifically, when the compensation component Tcg increases, road surface information such as the reduction in operating reaction force at the tire grip limit of the simulated vehicle is no longer transmitted to the driver. The operating torque-dependent gain Ko takes this into account. The operating torque-dependent gain determination unit 150 determines the operating torque-dependent gain Ko based on the operating torque To detected by the operating torque sensor 50, according to the operating torque-dependent gain determination map shown graphically in Figure 4(b). With the operating torque-dependent gain Ko determined in this way, the compensation component Tcg will be reduced in the high operating torque range where high turning lateral acceleration occurs. Alternatively, information on the turning lateral acceleration generated in the simulated vehicle may be input from the simulator body 72 to the reaction force ECU 40, and the operating torque-dependent gain determination unit 150 may be configured to determine the operating torque-dependent gain Ko based on that lateral acceleration instead of the operating torque To. In that case, if the communication speed of the turning lateral acceleration information is low, the operating torque-dependent gain Ko may be determined based on the derivative of that lateral acceleration. Incidentally, in that case, it is preferable to call the operating torque-dependent gain determination unit 150 the lateral acceleration-dependent gain determination unit, and the operating torque-dependent gain Ko the lateral acceleration-dependent gain.

[0056] The vehicle speed-dependent gain Kv is a component used to adjust the compensation component Tcg according to the vehicle speed v, or more specifically, the simulator vehicle speed vs. In typical vehicle characteristics, the response of the self-aligning torque acting on the wheels to the operation of the steering wheel 10 is delayed in the high-speed range where the vehicle speed v is high. Taking this into consideration, the vehicle speed-dependent gain determination unit 152 determines the vehicle speed-dependent gain Kv based on the vehicle speed v, according to the vehicle speed-dependent gain determination map shown in the graph of Figure 4(c). According to the vehicle speed-dependent gain Kv determined in this way, the compensation component Tcg will increase as the vehicle speed v increases.

[0057] The compensation component Tcg, determined via the correction unit 148, is added to the simulator command component Tch by the adder 154. In other words, the simulator command component Tch is corrected by the compensation component Tcg, and as a result, the simulation component Tcc is determined.

[0058] To briefly summarize the reaction force control in simulator mode with respect to the steering force-dependent component Tcs, in driving mode, the reaction force torque Tc as an operating reaction force is determined based on the steering force-dependent component Tcs, which is determined based on the current Is supplied to the steering motor 38. In contrast, in simulator mode, the reaction force torque Tc is determined based on a component obtained by correcting the simulator command component Tch, which is a command-dependent component (steering force command-dependent component) based on the simulator command value Θ, which is a command from simulator 70, based on the operating speed δ' of the steering wheel 10, with respect to the steering force-dependent component Tcs. This correction is performed to compensate for the delay of the command from simulator 70, and specifically, the reaction force torque Tc increases as the operating speed δ' of the steering wheel 10 increases. Furthermore, this correction is performed by adding a compensation component Tcg, which is determined based on the operating speed δ' of the steering wheel 10, to the simulator command component Tch. The compensation component Tcg is determined by taking into account the operating torque To, which is the operating force applied to the steering wheel 10, and the simulator vehicle speed vs, which is the driving speed of the simulated vehicle that is the target of operation in simulator 70.

[0059] ii) Vertical acceleration-dependent component and vertical acceleration-dependent component determination unit As shown in the block diagram of Figure 3(b), the vertical acceleration-dependent component determination unit 115 receives a signal regarding the vertical acceleration Gz of the simulated vehicle transmitted from the simulator main unit 72 via CAN46. This vertical acceleration Gz fluctuates periodically, and after passing through the bandpass filter 160, only the component of the fluctuating frequency f(Gz) within the set range is extracted.

[0060] The bandpass filter 160 is configured to change the setting range of the fluctuating frequency f(Gz) of the extracted component, i.e., the set frequency band, according to the vehicle speed v (simulator vehicle speed vs). More specifically, it extracts the vertical acceleration Gz of the fluctuating frequency f(Gz) in the set frequency band by referring to the extraction frequency map shown in the graph in Figure 5(a). Incidentally, in the graph, the horizontal axis represents the vehicle speed v, and the vertical axis represents the frequency median f0(Gz), which is the fluctuating frequency f(Gz) at the center of the set frequency band. The bandpass filter 160 extracts the vertical acceleration Gz of the frequency band with a set width centered on that fluctuating frequency f(Gz). The solid line in the graph represents the frequency median f0(Gz) in the extraction frequency map used in this bandpass filter 160, and this bandpass filter 160 employs an extraction frequency map in which the frequency median f0(Gz) increases linearly as the vehicle speed v increases. Instead of such an extracted frequency map, an extracted frequency map in which the median frequency f0(Gz) changes nonlinearly (nonlinearly) with respect to vehicle speed v may be used, as shown by a dashed or dotted line in the graph. Specifically, the set frequency band, that is, the range for setting the fluctuating frequency f(Gz), should be set such that, for example, when the vehicle speed v is 50 km / hr, the median frequency f0(Gz) is between a few Hz and 30 Hz.

[0061] The vertical acceleration Gz extracted as described above is multiplied by the conversion gain Kd in the conversion gain multiplier 162 to determine the fundamental vertical acceleration-dependent component Tcj. Simply put, the conversion gain Kd is a gain used to change the unit of the vertical acceleration Gz to the fundamental vertical acceleration-dependent component Tcj.

[0062] On the other hand, the vertical acceleration-dependent determination unit 115 has a second vehicle speed-dependent gain determination unit 164 that determines the second vehicle speed-dependent gain Kv2. The second vehicle speed-dependent gain Kv2 is a gain for changing the basic vertical acceleration-dependent component Tcj according to the vehicle speed v, and the second vehicle speed-dependent gain determination unit 164 determines the second vehicle speed-dependent gain Kv2 based on the vehicle speed v (simulated vehicle speed vs) while referring to the second vehicle speed-dependent gain determination map shown in the graph in Figure 5(b). According to this second vehicle speed-dependent gain determination map, the second vehicle speed-dependent gain Kv2 is determined to be 1 in the medium vehicle speed range, determined to be 0 in the low vehicle speed range where the vehicle speed v is less than the low vehicle speed vl, and determined to be smaller than 1 as the vehicle speed v increases in the high vehicle speed range where the vehicle speed exceeds the high vehicle speed vh. Incidentally, the low speed vl and high speed vh can be arbitrarily set according to the characteristics of the required reaction torque Tc, but in this second speed-dependent gain determination map, for example, the low speed vl is set to 10 km / hr and the high speed vh is set to 90 km / hr. Furthermore, by changing this second speed-dependent gain determination map, the conversion function of the conversion gain Kd described above can be assigned to this second speed-dependent gain Kv2, in which case the conversion gain Kd and the conversion gain multiplier 162 can be omitted.

[0063] As described above, the basic vertical acceleration-dependent component Tcj is multiplied by the second vehicle speed-dependent gain Kv2 in the multiplier 166 to determine the vertical acceleration-dependent component Tci. Due to the second vehicle speed-dependent gain Kv2, the vertical acceleration-dependent component Tci is set to 0 in the low vehicle speed range and decreases as the vehicle speed v increases in the high vehicle speed range.

[0064] The vertical acceleration-dependent component determination unit 115 is equipped with a limiter 168, and the determined vertical acceleration-dependent component Tci is passed through the limiter 168. The limiter 168 has the function of limiting the vertical acceleration-dependent component Tci to a set value or less. More specifically, the vertical acceleration Gz oscillates to take on positive and negative values, and the vertical acceleration-dependent component Tci also oscillates to take on positive and negative values. Therefore, the limiter 168 is designed to limit the absolute value of the vertical acceleration-dependent component Tci to a set value or less.

[0065] As shown in the block diagram of Figure 2, the vertical acceleration-dependent component Tci is input to the combiner 130 via the component switch 122. Based on the simulation feasibility signal Sa described earlier, the component switch 122 switches the generation / non-generation of the vertical acceleration-dependent component Tci so that it is generated in simulator mode and not generated in driving mode. In other words, the reaction torque Tc is determined so that it includes the vertical acceleration-dependent component Tci only in simulator mode.

[0066] To briefly summarize the reaction force control in simulator mode with respect to the vertical acceleration-dependent component Tci, in simulator mode, an operating torque Tc including a vertical acceleration-dependent component Tci based on a signal relating to the vertical acceleration Gz of the simulated vehicle is applied to the steering wheel 10. Since the vertical acceleration Gz fluctuates generally periodically according to the road surface conditions on which the simulated vehicle is traveling, the vertical acceleration-dependent component Tci also fluctuates generally periodically. As a result, the steering wheel 10 is made to vibrate in accordance with these fluctuations. For example, if the simulated vehicle deviates from the course on a circuit, the amplitude of the vibration will be relatively large, and the driver will experience an appropriate sense of realism.

[0067] In this system, the vertical acceleration-dependent component Tci is determined based on the vertical acceleration Gz, where the fluctuation frequency f(Gz) is within a set range. The setting range is set higher as the simulator vehicle speed v, which is the speed of the simulated vehicle, increases. Furthermore, in this system, the vertical acceleration-dependent component Tci is set to 0 when the simulator vehicle speed vs is less than a low vehicle speed vl, and decreases in proportion to the increase in simulator vehicle speed vs when the simulator vehicle speed vs exceeds a high vehicle speed vh. In addition, the vertical acceleration-dependent component Tci is limited to a set value or less. [Explanation of Symbols]

[0068] 10: Steering wheel (operating component) 12: Reaction force actuator (reaction force application device) 14: Wheels 16: Steering actuator (steering device) 18: Operating device 24: Reaction force motor (drive source) 38: Steering motor (drive source) 40: Reaction force ECU (controller) 42: Steering ECU (controller) 44: Dedicated high-speed communication line 46: CAN 70: Drive simulator 100: Target steering angle determination unit 102: Steering torque determination unit 104: Steering energization control unit 105: Vehicle speed selection unit 110: Current sensor 112: Assist component determination unit 114: Steering force dependent component determination unit 115: Vertical acceleration dependent component determination unit 116: Steering angle dependent component determination unit 118: Simulation component determination unit 120: Steering current dependent component determination unit 122: Component switcher 132: Reaction force energization control unit 144: Basic compensation component determination unit 148: Correction unit 150: Operation torque-dependent gain determination unit 152: Vehicle speed-dependent gain determination unit 164: Second vehicle speed-dependent gain determination unit Tc: Reaction torque Tca: Assist component Tcs: Steering force-dependent component Tcd: Steering angle-dependent component Tcb: Steering current-dependent component Tcc: Simulation component Tce: Estimated actual steering force-dependent component Tcf: Basic compensation component Tcg: Compensation component Tch: Simulator command component Tci: Vertical acceleration-dependent component Tcj: Basic vertical acceleration-dependent component δ: Operation angle δ': Operation speed ω: Steering angle ω *:Target steering angle Is:Steering current v:Vehicle speed vr:Actual vehicle speed vs:Simulator vehicle speed vl:Low vehicle speed vh:High vehicle speed Kb:Current-to-steering force conversion gain Θ:Simulator command value Gz:Vertical acceleration Ka:Contribution change gain Ko:Operating torque dependent gain Kv:Vehicle speed dependent gain Kv2:Second vehicle speed dependent gain f(Gz):Fluctuating frequency

Claims

1. An operating device having an operating member operated by the driver and a reaction force applying device that applies an operating reaction force which is a reaction force to the operation of the operating member, A steering device that steers the wheels using an electric motor, which is a steering motor, as the driving source, A controller that controls the steering device and the reaction force application device. A steer-by-wire steering system equipped with a driving simulator, which is installed in a vehicle equipped with a driving simulator, The aforementioned operating device is used to operate the simulated vehicle that is the target of operation in the drive simulator in the simulator mode in which the drive simulator is functioning. A steering system in which the controller is configured to cause the reaction force application device to apply an operating reaction force, which includes a vertical acceleration-dependent component based on a signal relating to the vertical acceleration of the simulated vehicle from the drive simulator, in its simulator mode.

2. The steering system according to claim 1, wherein the controller is configured to determine the vertical acceleration-dependent component based on vertical acceleration whose fluctuation frequency is within a set range.

3. The steering system according to claim 2, wherein the controller is configured to set the setting range higher the higher the driving speed of the simulated vehicle.

4. The steering system according to claim 1, wherein the controller is configured to determine the vertical acceleration-dependent component to 0 when the driving speed of the simulated vehicle is below a set low vehicle speed.

5. The steering system according to claim 1, wherein the controller is configured to reduce the vertical acceleration-dependent component in accordance with the increase in the driving speed when the driving speed of the simulated vehicle exceeds a set high speed.

6. The steering system according to claim 1, wherein the controller is configured to limit the vertical acceleration-dependent component to a set value or less.

7. The steering system according to claim 1, wherein the controller is configured to cause the reaction force application device to apply an operating reaction force including a steering force-dependent component based on a steering force which is the force that turns the wheels, and in simulator mode, the steering force-dependent component is configured to be determined based on a command regarding the steering force from the drive simulator.

8. The steering system according to claim 7, wherein the controller is configured to determine the steering force-dependent component based on the current supplied to the steering motor in the driving mode in which the vehicle is actually driving.

9. The steering system according to claim 7, wherein the controller is configured to determine the steering force-dependent component in simulator mode by applying a correction based on the operating speed of the operating member to the component determined based on the steering force command from the drive simulator.

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