Steering system

Abstract

The invention provides a steer-by-wire steering system with high practicability. In a steer-by-wire steering system mounted in a vehicle equipped with a driving simulator, an operation device (18) is used for operating the driving simulator, and controllers (40, 42) cause a reaction force application device (12) to apply an operation reaction force (Tc) including a steering force-based component (Tcs) based on a steering force, which is a force for steering wheels, and cause the operation device (18) to operate the driving simulator, and cause the control device (40, 42) to control the operation reaction force (Tc) to apply a steering force-based component (Tcs) based on the steering force-based component (Tcs). In a traveling mode in which the vehicle is actually traveling, the steering force-dependent component (120) is determined on the basis of a current (Is) supplied to the steering motor (38), and in a simulator mode, the steering force-dependent component (118) is determined by correcting a command-dependent component on the basis of a command (theta) from the driving simulator on the basis of the operating speed of the operating member (10).

Description

Technical Field

[0001] This invention relates to a steer-by-wire system for vehicles. Background Technology

[0002] In recent years, research has focused on steerable systems (hereinafter sometimes referred to as "steerable-by-wire systems") that are equipped in vehicles, specifically systems that mechanically separate operating components such as the steering wheel from the steering mechanism that steers the wheels. In steerable-by-wire systems, for example, as described in the following patent documents, a reaction force imparting device is provided to impart an operating reaction force to the operating components so that the driver can feel the steering operation.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-142704

[0004] On the other hand, research has also been conducted on games using driving simulators (hereinafter sometimes simply referred to as "simulators") that allow drivers to enjoy while the vehicle is not actually moving. In this case, when operating the vehicle (hereinafter sometimes referred to as the "simulated vehicle") being driven in the simulator using the steer-by-wire system's operating components, it is desirable to apply the aforementioned operating reaction force in the same way as in actual driving. If an appropriate operating reaction force can be applied through a reaction force application device, it will contribute to improving the practicality of the steer-by-wire system. The present invention was made in view of this practical situation, and its objective is to provide a highly practical steer-by-wire system. Summary of the Invention

[0005] To address the aforementioned issues, the steer-by-wire steering system of the present invention comprises:

[0006] The operating device has an operating component operated by a driver and a reaction force imparting device that imparts a reaction force to the operation relative to the operating component, i.e., an operating reaction force.

[0007] The steering system includes an electric motor, i.e., a steering motor, as the drive source to steer the wheels; and

[0008] The controller controls the aforementioned steering mechanism and the aforementioned reaction force imparting device.

[0009] The aforementioned steer-by-wire system is installed in vehicles equipped with driving simulators.

[0010] in,

[0011] The aforementioned operating device is used to operate the driving simulator in the simulator mode where the driving simulator functions.

[0012] The controller is configured to: apply an operating reaction force to the reaction force applicator, including a steering force component based on the force that steers the wheel, i.e., the steering force, and in simulator mode, determine the steering force component by modifying the operating speed of the operating component based on the instruction component based on the instruction from the driving simulator.

[0013] In simulator mode (the mode in which the simulator is being used), the steering mechanism does not turn the wheels of the vehicle. Therefore, the steering force on which the aforementioned steering force component is based is a simulated steering force used to turn the wheels of the simulated vehicle in the simulator, which is the object of the action. This simulated steering force, or the instruction indicating this simulated steering force, is sent from the simulator to the controller via electrical communication. This communication is conducted via a common communication line such as CAN (controllable area network or car area network), therefore, for example, the possibility of delay is high. In the steer-by-wire system of the present invention, in simulator mode, the aforementioned instruction component is modified as described above, thus providing an appropriate operating reaction force in simulator mode as well.

[0014] The configuration of the "steer-by-wire system" in this invention is not particularly limited and can be a general configuration. A "driving simulator" is a device that operates a vehicle as the object of action within a virtual space or environment. By using this simulator, drivers can enjoy games, etc., while the vehicle is not actually moving, such as while charging.

[0015] As explained later, the operating reaction force can also contain various components, with the "steering force based component" being the central component among these. Steering force is the force required to turn the wheel or maintain the amount of steering of that wheel. In the case where the steering system has a steering rod (rack) connecting the left and right wheels, it can be considered as a force acting in the axial direction of that steering rod. Therefore, steering force can also be called axial force, and the steering force based component can also be called the axial force based component. Furthermore, as explained earlier, in simulator mode, steering force is the steering force used to turn the wheels of the simulated vehicle, i.e., the simulated steering force.

[0016] In driving mode (the mode in which the vehicle is actually driven), the steering force is roughly proportional to the torque generated by the steering motor. That is, it is roughly proportional to the current supplied to the steering motor. Therefore, in driving mode, the steering force component can also be determined based on this current. In contrast, in simulator mode, no current is supplied to the steering motor, so the steering force component is determined based on instructions from the simulator. Moreover, the instructions can be the value of the steering force component itself, or they can be instructions indicating any value of the steering force.

[0017] "Correction based on the operating speed of the operating components" can also be performed, for example, to compensate for delays in commands from the simulator. Since the simulator is ultimately an optional feature of the vehicle—in other words, an entertainment device—as mentioned earlier, it typically uses common communication methods such as CAN to communicate with the system's controller. Therefore, in this case, the aforementioned commands are highly likely to experience delays. These delays depend on the operating speed of the operating components, making the aforementioned correction particularly effective in preventing them. Furthermore, communication within the system—for example, in cases where the controller is divided into sections controlling the reaction force application device and sections controlling the steering device—is generally conducted via dedicated high-speed communication lines, thus avoiding delays in signals regarding the current supplied to the steering motor in driving mode.

[0018] The aforementioned correction can also be made in such a way that the higher the operating speed of the operating component, the greater the operating reaction force. For example, since the higher the operating speed, the greater the aforementioned delay, such a correction is suitable for mitigating the effects of the aforementioned delay.

[0019] The aforementioned correction can also be made, for example, by adding a compensation component based on the operating speed of the operating component to the instruction-based component. In this case, the operating force of the driver applied to the operating component can also be considered in determining the compensation component, as will be explained later. Specifically, for example, the compensation component can be determined to be smaller as the operating force increases. Furthermore, the speed of the simulated vehicle acting as the action target in the simulator can also be considered in determining the compensation component. Specifically, for example, the compensation component can be determined to be smaller as the speed decreases. Attached Figure Description

[0020] Figure 1 This is a diagram showing the overall structure of the steering system in an embodiment.

[0021] Figure 2 This is a block diagram illustrating the functional structure of the controller of the steering system in an embodiment.

[0022] Figure 3 This is a block diagram showing the details of the functional units in the controller's functional structure that determine the components of the operational reaction force based on instructions from the driving simulator.

[0023] Figure 4 It is a graph representing the mapping referenced when determining the component of the reaction force based on instructions from the driving simulator.

[0024] Explanation of reference numerals in the attached figures

[0025] 10…Handle (operating component); 12…Reaction force actuator (reaction force imparting device); 14…Wheel; 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…Driving simulator; 100…Target steering angle determination unit; 102…Steering torque determination unit; 104…Steering power control unit; 105…Vehicle speed selection unit; 110…Current sensor; 112…Auxiliary component determination unit; 114…Steering force basis component determination unit; 116…Steering angle basis component determination unit; 118…Analog component determination unit; 120…Steering current basis component determination unit; 122…Component switcher; 132…Reaction force actuator; 14…Steering force actuator (controller); 15…Steering force actuator (controller); 16…Steering force actuator (controller); 17…Steering force actuator (controller); 18…Steering force actuator (controller); 19…Steering force actuator (controller); 102…Steering force actuator (controller); 103…Steering force actuator (controller); 104…Steering force actuator (controller); 105…Steering force actuator (controller); 106…Steering force actuator (controller); 107…Steering force actuator (controller); 108…Steering force actuator (controller); 109…Steering force actuator (controller); 10 ... Force energization control unit; 144… Basic compensation component determination unit; 148… Correction unit; 150… Operating torque based gain determination unit; 152… Vehicle speed based gain determination unit; Tc… Reaction torque; Tca… Auxiliary component; Tcs… Steering force based component; Tcd… Steering angle based component; Tcb… Steering current based component; Tcc… Simulation component; Tce… Inferred actual steering force based component; Tcf… Basic compensation component; Tcg… Compensation component; Tch… Simulator command component; δ… Operating angle; δ'… Operating speed; ω… Steering angle; ω*… Target steering angle; Is… Steering current; v… Vehicle speed; vr… Actual vehicle speed; vs… Simulator vehicle speed; Kb… Current-steering force conversion gain; Θ… Simulator command value; Ka… Contribution change gain; Ko… Operating torque based gain; Kv… Vehicle speed based gain. Detailed Implementation

[0026] Hereinafter, a steering system as an embodiment of the present invention will be described in detail with reference to the accompanying drawings, as a means of carrying out the present invention. Furthermore, in addition to the embodiments described below, the present invention can be implemented in various ways with various modifications and improvements based on the knowledge of those skilled in the art, starting with the manner described in the above-described [Technical Solution of the Invention].

[0027]

Example

[0028] [1] Overall structure of the steering system

[0029] The steering system of this embodiment (hereinafter, sometimes referred to as "this steering system" or "this system") is a steer-by-wire system that can turn the wheels without relying on the driver's operating force applied to the operating components, such as... Figure 1As shown, the system comprises a handle (steering wheel) 10 as an operating component, a reaction force actuator 12 connected to the handle 10 as a reaction force applying device, and a steering actuator 16 as a steering device that connects to the left and right wheels 14, which are steering wheels, and turns them together. Furthermore, the system is configured such that when the handle 10 is rotated by the driver, the reaction force actuator 12 receives the operation and applies a reaction force (hereinafter sometimes referred to as "operation reaction force") relative to the operation of the handle 10, specifically relative to the operation of the handle 10. The operating device 18 of this steering system comprises the handle 10 and the reaction force actuator 12.

[0030] The reaction force actuator 12 is configured to include a steering column 20 supported by a reinforcement member on the instrument panel, a steering shaft 22 held rotatably by the steering column 20, and a reaction force motor 24, which serves as an electric motor for imparting rotational torque to the steering shaft 22 via a power transmission mechanism. A handle 10 is mounted at the rear end of the steering shaft 22. The power transmission mechanism is configured to include a worm gear mounted on the motor shaft of the reaction force motor 24, and a turbine mounted on the steering shaft 22 and meshing with the worm gear; detailed descriptions of its construction are omitted here. The reaction force motor 24 is a three-phase brushless DC motor, which functions as the drive source for the reaction force actuator 12. The torque generated by the reaction force motor 24 imparts a reaction force torque, acting as an operating reaction force, to the handle 10 connected to the steering shaft 22.

[0031] The steering actuator 16 is configured to include a generally cylindrical housing 30 supported on the chassis in a left-right extending position, a steering rod (rack rod) 32 held in place by the housing 30 to prevent rotation but capable of left-right movement, and a pair of tie rods 34 connected to the left and right ends of the steering rod 32 via ball joints. The front end of each tie rod 34 is connected to the wheel 14 via a ball joint. More specifically, each tie rod 34 is connected via a ball joint to a steering knuckle arm that holds the wheel 14 in a rotatable position and is held in a steerable position by the suspension arm.

[0032] A threaded groove 36 is formed in the steering lever 32. Although not shown in the figure, the nut, which holds the bearing balls and engages with the threaded groove 36, is kept within the housing 30 so that it cannot move left or right but can rotate. That is, the steering lever 32 and the nut constitute a ball screw mechanism. A steering motor 38, which is an electric motor, is attached to the housing 30. The steering motor 38 rotates the nut via a power transmission mechanism. Moreover, although not shown in the figure, the power transmission mechanism is configured to include a pulley mounted on the motor shaft of the steering motor 38 and a timing belt wound around the pulley and the outer periphery of the nut. The steering motor 38 is a three-phase brushless DC motor and functions as the drive source for the steering actuator 16. By rotating the steering motor 38, the steering lever 32 moves left or right, causing the left and right wheels 14 to turn together.

[0033] The reaction force actuator 12 is controlled by a reaction force electronic control unit (hereinafter, sometimes referred to as a "reaction force ECU") 40 attached to the reaction force motor 24. The reaction force ECU 40 is configured as a computer comprising a CPU, ROM, RAM, etc., and an inverter serving as a 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 a "steering ECU") 42 attached to the steering motor 38. The steering ECU 42 is configured as a computer comprising a CPU, ROM, RAM, etc., and an inverter serving as a driver (drive circuit) for the steering motor 38, and is powered by a battery.

[0034] The reaction force ECU 40 and the steering ECU 42 cooperate with each other, forming a controller for the steering system. Therefore, the reaction force ECU 40 and the steering ECU 42 are connected via a dedicated high-speed communication line 44. Furthermore, they are both connected to the vehicle's CAN (car area network or controllable area network) 46. In addition, the vehicle speed sensor 48, used to detect the vehicle's actual driving speed, i.e., the actual vehicle speed vr, is also connected to the CAN 46.

[0035] Related to control, although detailed structural descriptions are omitted for the reaction force actuator 12, it includes an operating torque sensor 50 that detects the operating torque To, which is the operating force applied by the driver to the handlebar 10, by detecting the amount of torsion of the steering shaft 22. Additionally, it includes an operating angle sensor 52 that detects the operating angle δ of the handlebar 10 by detecting the rotation angle of the steering shaft 22, and a reaction force motor rotation angle sensor 54 that detects the rotation angle (rotation phase) θmc of the reaction force motor 24 for purposes such as switching the energized phase.

[0036] The steering actuator 16 will be described below. Since the steering angle of the wheel 14 and the left-right movement position of the steering lever 32 are fixed, a steering angle sensor 56 is provided to detect the movement position of the steering lever 32 in order to detect the steering angle of the wheel 14. To briefly explain, a rack 58 is formed in the steering lever 32, and a pinion shaft 60 meshing with the rack 58 is held in the housing 30. While it is possible to use the rotation angle (toe angle) of the wheel 14 as the steering angle, 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. Furthermore, the steering actuator 16 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 of the energized phase.

[0037] The vehicle equipped with this system is equipped with a driving simulator (hereinafter, sometimes simply referred to as "simulator") 70. The simulator 70 is a device that makes a simulated vehicle, which is a virtual action object, drive within a virtual environment (virtual space) and displays changes in scenery (environmental components) that can be observed from the simulated vehicle as images. For example, when the vehicle stops, such as while it is charging, the driver of the vehicle can enjoy games or the like through the simulator 70.

[0038] The simulator 70 is configured to include a simulator body 72, which is mainly a computer; a goggle-type head-mounted display (hereinafter, sometimes simply referred to as "display") 74 for the driver to observe images from the perspective of a simulated vehicle; and a simulation malfunction determination unit 76 for determining whether the simulator 70 can work. Furthermore, while the aforementioned head-mounted display 74 is used as the means of image display in this simulator 70, various other means can be used, such as a head-up display that projects images onto the windshield of the vehicle, a large display located in front of the vehicle, a screen located in front of the vehicle, and a projector for projecting images onto the screen.

[0039] In the simulated operation of the vehicle, this system, specifically the operating device 18 of this system, is used. Therefore, the simulator body 72 and the simulation permission determiner 76 are connected to the CAN 46, and communication between the simulator 70 and this system is performed via the CAN 46. Furthermore, in the simulated operation of the vehicle, the accelerator pedal 80 and brake pedal 82 of the vehicle are also used; therefore, the accelerator operation amount sensor 84, which detects the operation amount of the accelerator pedal 80 (i.e., the accelerator operation amount λa), and the brake operation amount sensor 86, which detects the operation amount of the brake pedal 82 (i.e., the brake operation amount λb), are also connected to the CAN 46.

[0040] [2] Functions of the controller

[0041] The controller of this steering system, consisting of the reaction force ECU40 and the steering ECU42, has Figure 2 The functional structure is as shown in the functional block diagram. This functional structure is implemented by a computer executing a prescribed program. The inputs to or outputs from each component (functional unit) shown in the diagram are mostly signals representing torque, its components, steering angle, operating angle, etc. However, to avoid making the explanation lengthy, in the following description, it will be expressed as only inputting to or outputting torque, its components, steering angle, operating angle, etc., to each component. Furthermore, for ease of understanding, the functions related to steering control performed by the steering ECU 42 in the actual driving mode of the vehicle (i.e., driving mode), the functions related to reaction force control performed by the reaction force ECU 40, and the reaction force control performed by the reaction force ECU 40 in the simulator mode where driving simulation is performed by the simulator 70 will be explained in turn.

[0042] (a) Steering control in driving mode

[0043] Steering control concerns the control of the steering angle ω of the wheels 14 steered by the steering actuator 16. The steering ECU 42, serving as the steering control unit, includes a target steering angle determination unit 100, a steering torque determination unit 102, and a steering energization control unit 104. Furthermore, in reaction force control and steering control, the vehicle's travel speed, i.e., vehicle speed v, is used. However, the vehicle speed v used differs between driving mode and simulator mode. Specifically, in driving mode, it is the actual travel speed of the vehicle, i.e., actual vehicle speed vr; in simulator mode, it is the travel speed of the simulated vehicle in simulator 70, i.e., simulator vehicle speed vs. . Therefore, the steering ECU 42 has a vehicle speed selection unit 105 to selectively use either the actual vehicle speed vr detected by the vehicle speed sensor 48 or the simulator vehicle speed vs sent from the simulator body 72 as 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 affirmative / negative signal Sa sent from the simulation affirmative / negative determinant 76. Specifically, in driving mode, simulation is disabled, and the actual vehicle speed (vr) is selected; in simulation mode, simulation is enabled, and the simulator speed (vs) is selected.

[0044] In the control of this steering system, the steering angle ω is used as the steering amount of wheel 14. However, this steering angle ω does not use the value detected by the steering angle sensor 56, but rather a value calculated 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 the steering angle ω. The cumulative amount of the steering angle ω and the steering motor rotation angle θms is related according to a predetermined reduction ratio, therefore, the steering angle conversion unit 108 performs a conversion based on this reduction ratio.

[0045] The target steering angle determination unit 100 determines the control target, i.e., the target steering angle ω*, of the steering angle ω based on the operating angle δ calculated by the operating angle conversion unit 108 of the reaction force ECU 40, as described later. This steering system is one in which the steering transmission ratio γ, i.e., the ratio of steering angle ω to operating angle δ, changes according to the vehicle speed v. The target steering angle determination unit 100 determines the target steering angle ω* based on the operating angle δ and vehicle speed v, referring to stored mapping data. Furthermore, the method for changing the steering transmission ratio γ is a conventional method, and its description is omitted here. In addition, the target steering angle ω* is also used as the target steering angle of the simulated vehicle in the simulation, and therefore is sent to the simulator 70, specifically, to the simulator body 72, via CAN 46.

[0046] 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 considered, for example, the torque that the steering motor 38 should generate. Specifically, based on the actual steering angle ω at the current moment calculated by the steering angle conversion unit 106 and the target steering angle ω*, the deviation of the steering angle ω from the target steering angle ω*, i.e., the steering angle deviation Δω, is determined. Based on this steering angle deviation Δω, the steering torque Ts to be generated is determined according to a PID feedback control rule. The determination method according to this feedback control rule is a conventional method, and its explanation is omitted here.

[0047] The steering power control unit 104 is configured to include an inverter that serves as a drive circuit (driver) for the steering motor 38. Based on the determined steering torque Ts, the steering power control unit 104 determines the steering current Is, which should be supplied to the steering motor 38, and supplies this steering current Is from the inverter to the steering motor 38. Furthermore, the steering ECU 42 has a current sensor 110 for detecting the actual supplied steering current Is.

[0048] Furthermore, in simulator mode, there is no need to steer the vehicle's wheels 14; therefore, the steering torque determination unit 102 does not determine the steering torque Ts and does not send a signal regarding the steering torque Ts to the steering energization control unit 104. This determination and its execution / non-execution are based on the simulation yes / no signal Sa described above.

[0049] (b) Reaction force control in driving modes

[0050] The reaction force ECU40, which is a reaction force control unit, controls the reaction force torque Tc that should be applied to the handle 10 by the reaction force actuator 12, which is a reaction force application device. The reaction force ECU40 has an auxiliary component Tca that determines the component of the reaction force torque Tc, an auxiliary component determining component Tcs that determines the steering force basis component, and a steering force basis component determining component 114.

[0051] The steering force reference component Tcs is determined by adjusting the steering angle reference component Tcd and the inferred actual steering force reference component Tce. For the inferred actual steering force reference component Tce, in driving mode, it is determined as the steering current reference component Tcb, and in simulator mode, it is determined as the analog component Tcc, which will be explained in detail later. The steering force reference component Tcs includes these components; therefore, the steering force reference component determination unit 114 includes a steering angle reference component determination unit 116, an analog component determination unit 118, a steering current reference component determination unit 120, a component switcher 122, weighters 124 and 126, and an adder 128.

[0052] In the control of this steering system, the operating angle δ is used as the operation amount of the handle 10. Therefore, similar to the steering ECU 42, the reaction force ECU 40 has an operating angle conversion unit 108 that converts the reaction force motor rotation angle θmc detected by the reaction force motor rotation angle sensor 54 into the operating angle δ. The cumulative amount of the operating angle δ and the reaction force motor rotation angle θmc is in a relationship corresponding to a predetermined reduction ratio. Therefore, the operating angle conversion unit 108 performs a conversion based on this reduction ratio.

[0053] Regarding the determination of each component of the aforementioned reaction torque Tc, the following explanation is provided according to the driving mode: The assist component Tca is a component similar to the assist force in so-called power steering. The assist component determination unit 112 determines the assist component Tca based on the operating torque To detected by the operating torque sensor 50 and the vehicle speed v. In short, the value of the assist component Tca is set larger when the operating torque To is larger, and a smaller value is taken at high vehicle speeds to provide the driver with a stable operating feel for the lever 10, while a larger value is taken at low vehicle speeds to provide a light operating feel. The orientation of the assist component Tca is the same as the direction of operation of the lever 10, i.e., the steering operation direction.

[0054] The steering force component Tcs can be considered as the central component of the reaction torque Tc; broadly speaking, it is the component of the force required for the driver to feel the steering of the wheel 14, i.e., the steering force. The steering force component Tcs can also be considered as the axial force component, i.e., the component based on the force (axial force) acting axially on the steering lever 32 of the steering actuator 16. The steering force component Tcs is generally the component in the direction opposite to the steering operation direction.

[0055] The steering angle reference component Tcd, which is a component of the steering force reference 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-centering torque. In other words, it can be considered as a steering force that does not reflect road surface unevenness that does not affect the lateral behavior of the vehicle, or road surface differences that do affect the lateral behavior of the vehicle. The steering angle reference component determination unit 116 determines the steering angle reference component Tcd based on the target steering angle ω* determined by the target steering angle determination unit 100 of the steering ECU 42 and the vehicle speed v, according to a prescribed mapping, the details of which are omitted here. The larger the target steering angle ω*, the larger the value of the steering angle reference component Tcd will be determined. In addition, the higher the vehicle speed v, the larger the value of the steering angle reference component Tcd will be determined.

[0056] As explained above, the analog component Tcc determined by the analog component determination unit 118 is the inferred actual steering force basis component Tce in simulator mode. Therefore, the analog component determination unit 118 and the analog component Tcc will be explained later. Furthermore, the switching between the analog component Tcc and the steering current basis component Tcb is performed by the component switcher 122. This switching is based on the analog yes / no signal Sa explained above.

[0057] The steering current reference component Tcb, which is the inferred actual steering force reference component Tce during driving modes, differs from the steering angle reference component Tcd. It is a component that reflects the influence of the aforementioned road surface information; in other words, it is, for example, a component that comprehensively reflects the force exerted on the wheel 14 from the road surface. In short, the steering current reference component determination unit 120 determines the steering current reference component Tcb by multiplying the actual steering current Is detected by the current sensor 110 by the set current-steering force conversion gain Kb.

[0058] The adjustment of the steering angle reference component Tcd and the inferred actual steering force reference component Tce is as follows. Weighter 124 multiplies the steering angle reference component Tcd by a weighting coefficient α (0 < α < 1). Simultaneously, weighter 126 multiplies the inferred steering angle reference component Tce by 1 and subtracts the weighting coefficient α. Adder 128 then sums these multiplied values ​​to determine the steering force reference component Tcs. Although detailed explanations are omitted, the weighting coefficient α can be set to a fixed value, but it can also be set to vary based on various important factors such as vehicle speed v, road surface conditions, and vehicle driving conditions.

[0059] The auxiliary component Tca determined by the auxiliary component determination unit 112 and the steering force basis component Tcs determined by the steering force basis component determination unit 114 are synthesized by the synthesizer 130, and the reaction torque Tc is determined. The determined reaction torque Tc is input to the reaction force energizing control unit 132. The reaction force energizing control unit 132 is configured as an inverter including a drive circuit (driver) for the reaction force motor 24. Based on the reaction torque Tc, the reaction force energizing control unit 132 determines the reaction current Ic, which is the current to be supplied to the reaction force motor 24, and supplies the reaction current Ic from the inverter to the reaction force motor 24.

[0060] (c) Reaction force control in simulator mode

[0061] In simulator mode, the simulated component Tcc is determined by using the actual steering force reference component Tce instead of the aforementioned steering current reference component Tcb. Otherwise, the reaction force control in simulator mode is the same as in driving mode. See below for further details. Figure 3 The block diagram illustrates the functions of the analog component Tcc and the analog component determination unit 118 that determines it.

[0062] like Figure 3As shown in the block diagram, the simulator command value Θ, transmitted from the simulator body 72 via CAN 46, is input to the simulation component determination unit 118. This simulator command value Θ indicates the inferred actual steering force basis component Tce that should be generated by the simulator 70. This component is multiplied by the conversion gain Kc by the conversion gain multiplier 140, thereby determining the simulator command component Tch. Furthermore, if the simulator command value Θ is in the same unit as the reaction torque Tc and its components, in other words, if the simulator command component Tch is directly input from the simulator body 72, then the conversion gain multiplier 140 is not required.

[0063] As mentioned earlier, the simulator command value Θ is sent from the simulator body 72 via communication, which results in a delay; in other words, a phase delay. Therefore, in the analog component determination unit 118, in order to eliminate or mitigate this delay, a correction process based on the compensation component Tcg, as described below, is performed.

[0064] The analog component determination unit 118 is input with the operating angle δ calculated by the operating angle conversion unit 108. The analog component determination unit 118 has a differentiator 142, which calculates the operating speed δ' (=dδ / dt) of the handle 10, which is the operating component. The basic compensation component determination unit 144 is referenced in… Figure 4 The basic compensation component determination mapping, represented by the curve in (a), determines the basic compensation component Tcf based on the operating speed δ'. Considering that the higher the operating speed δ', the greater the delay, the basic compensation component determination mapping is set as follows: the greater the operating speed δ', the greater the basic compensation component Tcf.

[0065] As shown by the dashed line in the graph, the basic compensation component determination mapping can also be set so that the basic compensation component Tcf varies linearly with respect to the operating speed δ'. However, if the basic compensation component Tcf increases, the damping component of the reaction torque Tc increases, which weakens the clarity of the handle 10's operation feel and reduces the sense of presence in the simulation. Therefore, as shown by the solid line in the graph, a nonlinear basic compensation component determination mapping can also be used, where the basic compensation component Tcf decreases in the region with relatively little delay relative to the operating speed δ', i.e., in the region with low operating speed δ'. Moreover, if the basic compensation component Tcf varies linearly with respect to the operating speed δ', then mapping is not necessary, and the basic compensation component Tcf can be determined based on a fixed gain setting.

[0066] In this simulation component determination unit 118, the contribution-change gain multiplier 146 multiplies the basic compensation component Tcf determined by the basic compensation component determination unit 144 by the contribution-change gain Ka 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, the magnitude of the basic compensation component Tcf can be changed based on the simulated vehicle speed vs, the road surface on which the simulated vehicle travels, and the driving state of the simulated vehicle. However, if a contribution-change function is further added to the above-mentioned basic compensation component determination mapping, the contribution-change gain multiplier 146 may not be required.

[0067] The analog component determination unit 118 has a correction unit 148, which determines the compensation component Tcg by multiplying the determined basic compensation component Tcf by the operating torque-based gain Ko and the vehicle speed-based gain Kv.

[0068] The operating torque-based gain Ko is set to account for other effects caused by the increase in the compensation component Tcg. Specifically, if the compensation component Tcg increases, road surface information such as the reduction in operating reaction force in the simulated vehicle's tire grip limit will not be transmitted to the driver. The operating torque-based gain Ko is a gain that takes this situation into account. The operating torque-based gain determination unit 150 determines the operating torque based on the operating torque To detected by the operating torque sensor 50, according to... Figure 4 The operating torque based gain Ko is determined by the curve-based mapping in (b). Based on this determined operating torque based gain Ko, the compensation component Tcg is reduced in the high operating torque region where high lateral acceleration during cornering occurs. Alternatively, the system can be configured such that information about the lateral acceleration during cornering generated by the simulated vehicle is input from the simulator body 72 to the reaction force ECU 40, and the operating torque based gain determination unit 150 determines the operating torque based gain Ko based on this lateral acceleration instead of the operating torque To. In this case, even when the communication speed of the lateral acceleration information is low, the operating torque based gain Ko can be determined based on the differential value of this lateral acceleration.

[0069] The vehicle speed-based gain Kv is a component used to adjust the compensation component Tcg based on the vehicle speed v, specifically the simulator vehicle speed vs. In typical vehicle characteristics, in the high-speed region where vehicle speed v is high, there is a response delay in the self-centering torque acting on the wheels relative to the operation of the handle 10. Taking this into account, the vehicle speed-based gain determination unit 152, based on the vehicle speed v, adjusts the compensation component Tcg according to the vehicle speed v. Figure 4 The curve (c) represents the vehicle speed based on the gain mapping, which determines the vehicle speed based gain Kv. According to this determined vehicle speed based gain Kv, as the vehicle speed v increases, the compensation component Tcg will increase.

[0070] Adder 154 adds the compensation component Tcg determined by correction unit 148 to simulator instruction component Tch, and uses the result to determine simulation component Tcc.

[0071] To summarize the reaction force control in simulator mode, the reaction torque Tc, as the operating reaction force, is determined in driving mode based on the steering force component Tcs, which is determined by the current Is supplied to the steering motor 38. In contrast, in simulator mode, it is determined based on the following component: a component that corrects for the operating speed δ' of the handle 10, which is the simulator command component Tch, based on the simulator command value Θ from the simulator 70. This correction is made to compensate for delays in the commands from the simulator 70; specifically, the higher the operating speed δ' of the handle 10, the greater the reaction torque Tc. Furthermore, this correction is achieved by adding a compensation component Tcg, determined based on the operating speed δ' of the handle 10, to the simulator command component Tch. This compensation component Tcg is determined by considering both the operating torque To, which is the operating force applied to the handle 10, and the speed of the simulated vehicle in the simulator 70, i.e., the simulator vehicle speed vs.

Claims

1. A steering system, a steer-by-wire type steering system, mounted on a vehicle equipped with a driving simulator, comprising: The operating device has an operating component operated by a driver and a reaction force imparting device that imparts a reaction force to the operation relative to the operating component, i.e., an operating reaction force. The steering system has an electric motor, also known as a steering motor, as the drive source to turn the wheels. as well as The controller controls the steering mechanism and the reaction force application device. in, The operating device is used to operate the driving simulator in the simulator mode where the driving simulator functions. The controller is configured to: apply an operating reaction force to the reaction force applicator, including a steering force basis component based on the force that steers the wheel, i.e., the steering force, and, in simulator mode, determine the steering force basis component by modifying the operating speed of the operating component based on the instruction basis component based on the instruction from the driving simulator.

2. The steering system according to claim 1, wherein, The controller is configured to determine the steering force based on the current supplied to the steering motor during actual vehicle operation.

3. The steering system according to claim 1, wherein, The controller is configured to perform a correction based on the operating speed of the operating components in order to compensate for the delay of instructions from the driving simulator.

4. The steering system according to claim 1, wherein, The controller is configured to correct the operating speed of the operating component in such a way that the higher the operating speed of the operating component, the greater the operating reaction force.

5. The steering system according to claim 1, wherein, The controller is configured to correct the operating speed of the operating component by adding a compensation component determined based on the operating speed of the operating component to the instruction basis component.

6. The steering system according to claim 5, wherein, The controller is configured to determine the compensation component by also taking into account the driver's operating force applied to the operating component.

7. The steering system according to claim 5, wherein, The controller is configured to determine the compensation component by also considering the speed of the simulated vehicle that becomes the action object in the driving simulator.

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