Steering system

Abstract

Provided is a steer-by-wire steering system that is highly practical. A steer-by-wire steering system mounted in a vehicle having a simulated driving device mounted thereon is configured such that, in a simulation mode in which the simulated driving device is activated, an operation device (18) is used for operating a simulated vehicle to be operated in the simulated driving device, and controllers (40, 42) control the simulated vehicle to be operated in the simulated driving device in the simulation mode. An operation reaction force (Tc) including a vertical acceleration basis component (Tci) based on a signal relating to the vertical acceleration (Gz) of the simulated vehicle from the simulated driving device is added to the operation member (10) by a reaction force adding device (12). Under the condition that the vehicle is simulated to be separated from the route, the driver can properly experience the separation.

Description

Technical Field

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

[0002] In recent years, there has been active exploration into incorporating steer-by-wire systems (hereinafter sometimes referred to as "steer-by-wire systems") into vehicles. More specifically, these systems mechanically separate the steering components, such as the steering wheel, from the steering mechanism that steers the wheels. In steer-by-wire systems, to allow the driver to experience steering operation, a reaction force supplement device is installed that adds a reaction force to the operation of the steering components.

[0003] On the other hand, there is also active exploration of games where the driver enjoys a driving simulation device (hereinafter sometimes simply referred to as a "simulator") inside the vehicle when the vehicle is not actually being driven. In this case, the operation of the vehicle (hereinafter sometimes referred to as a "simulated vehicle") being driven in the simulator, utilizing a steer-by-wire system, is also being explored. When using the operating components to simulate vehicle operation, it is desirable to add the aforementioned operational reaction force, similar to actual driving. Regarding the operational reaction force of the simulator, there exists a technology as described in the following patent documents.

[0004] Patent Document 1: Japanese Patent Application Publication No. 4-232829

[0005] In the technology described in the aforementioned patent documents, in addition to the restoring force used to return the operating components to a neutral position, vibrations based on the simulated vehicle's speed and engine rotation speed are added as operating reaction forces to achieve a driving feel close to that of actual driving. There is still much room for improvement in the work required to achieve a driving feel close to that of actual driving. By applying certain improvements to the added operating reaction forces, the operating components can be used for operating a simulated vehicle in a simulator, thereby improving the practicality of the steer-by-wire system. This invention was made in view of this reality, and the objective is to provide a highly practical steer-by-wire system. Summary of the Invention

[0006] To solve the above-mentioned problems, the steering system of the present invention comprises:

[0007] The operating device has an operating component operated by a driver and a reaction force affixing device, wherein the reaction force affixing device affixes an operating reaction force as a reaction force to the operation of the operating component;

[0008] A steering system that steers the wheels and includes an electric motor, i.e., a steering motor, as the drive source; and

[0009] The controller controls the aforementioned steering mechanism and the aforementioned reaction force auxiliary device.

[0010] The aforementioned steering system is a steer-by-wire system installed in vehicles equipped with driving simulators.

[0011] in,

[0012] The aforementioned operating device, in the simulation mode activated by the aforementioned driving simulator, is used to operate the simulated vehicle that becomes the object of the action within the driving simulator.

[0013] The controller is configured such that, in the simulation mode, the reaction force attachment device applies an operational reaction force, the operational reaction force containing an up-and-down acceleration basis component, the up-and-down acceleration basis component being based on a signal from the simulated driving device related to the up-and-down acceleration of the simulated vehicle.

[0014] According to the steering system of the present invention, in simulation mode, an operating reaction force is added to the operating components, the operating reaction force containing a component based on the vertical acceleration generated in the simulated vehicle. The vertical acceleration can indicate changes in road surface characteristics (the road conditions on which the simulated vehicle is traveling), and the steering system according to the present invention allows the driver to experience these changes in road surface characteristics. For example, in a simulation of a vehicle traveling on a ring road, when the simulated vehicle deviates from the path, the driver can easily feel the presence of that deviation.

[0015] [Invention Method]

[0016] The structure of the "steer-by-wire system" in this invention is not particularly limited and a conventional structure can be used. The "driving simulator" is a device for operating a vehicle (i.e., a "simulated vehicle") within an imaginary space and environment. Using this simulator, drivers can enjoy games, etc., while the vehicle is not actually moving, such as while charging. Furthermore, in the "simulation mode" activated by the simulator, no actual wheel steering occurs due to the steering device.

[0017] The "vertical acceleration component," which is one component of the operational reaction force, is a component generated only in simulation 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 (road characteristics), it can be considered a component reflecting these driving states and road characteristics. By employing this vertical acceleration component, as mentioned above, it is possible to provide the driver with a sense of presence, for example, when the simulated vehicle deviates from its path.

[0018] For example, the advantages of using signals related to vertical acceleration to provide the driver with a sense of presence are described below. Taking the simulation of a vehicle veering off course as an example, consider having the controller simply receive a signal from the simulator that the vehicle has veered off course and, based on this signal, cause the operating components to vibrate through an operational reaction force. However, this vibration would only be a single pattern. In contrast, if a signal related to vertical acceleration is used, various patterns of vibration can be added to the operating components by varying the vibration period (frequency variation) and amplitude of this vertical acceleration. That is, by using a signal related to vertical acceleration, the period and amplitude of the vibration generated on the operating components can be easily dynamically varied. Furthermore, for example, in the case of a vehicle equipped with an active suspension system, this signal can also be used to provide various vibration actions to the vehicle body itself through the system.

[0019] The vertical acceleration component can also be determined based on the vertical acceleration within a set frequency range. For example, a bandpass filter can be used to extract vertical acceleration within a certain frequency band, and the vertical acceleration component can be determined based on this extracted vertical acceleration. By using vertical acceleration within a set frequency range, a suitable sense of presence can be provided to the driver. This "set range" can be adjusted considering the ease with which vibrations are transmitted to the driver, or it can be set based on the spring resonant frequency of the vehicle equipped with the system. Specifically, for example, it can be set to a range of a few Hz to 30 Hz. Furthermore, the set range is preferably varied based on the simulated vehicle's speed (hereinafter sometimes referred to as "vehicle speed"). Specifically, since the variation in vertical acceleration is caused by the unevenness of the road surface on which the simulated vehicle travels, and since the period of this variation depends on the simulated vehicle's speed, it is preferable to set the set range to increase as the vehicle speed increases.

[0020] Furthermore, when the simulated vehicle speed is lower than the set low speed, it is preferable to set the aforementioned vertical acceleration component to 0. When the simulated vehicle speed exceeds the set high speed, it is preferable to reduce the vertical acceleration component as the speed increases. This is because, in low-speed areas (e.g., below 10 km / hr), it is preferable to avoid vibration of the operating components and discomfort caused by their movement. On the other hand, in high-speed areas (e.g., above 80-100 km / hr), it is preferable to consider the possibility that the driver may become annoyed by the vibration of the operating components. Moreover, considering the abrupt movement of the operating components, it is preferable to limit the vertical acceleration component to a set value. This set value can be set, for example, by considering the magnitude of the impact and discomfort to the driver.

[0021] The operating reaction force can also contain various components. Specifically, for example, the central component of the operating reaction force can also include a "steering force basis component." "Steering force" is the force required to turn the wheel or maintain the amount of steering (steering angle) 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 basis component can also be called the axial force basis component. Furthermore, as explained above, in simulation mode, the steering force is the steering force used to turn the wheels of the simulated vehicle, i.e., the simulated steering force.

[0022] In "driving mode," which represents the actual driving mode of the vehicle, the steering force is approximately proportional to the torque generated by the steering motor. That is, it is approximately 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 simulation mode, since no current is supplied to the steering motor, the steering force component can be determined based on instructions from the simulator, specifically instructions related to the steering force. Incidentally, these instructions can be the value of the steering force component itself, or they can be instructions indicating any value of the steering force.

[0023] "Correction based on the operating speed of the operating components" can also be used, for example, to compensate for delays in commands from the simulator. Since the simulator is essentially an optional feature of the vehicle—in other words, an entertainment device—it typically communicates with the system's controller using common communication methods such as CAN (controllable area network or car area network). Therefore, in this case, the commands are highly susceptible to delay. Because this delay depends on the operating speed of the operating components, the aforementioned correction is suitable for preventing this delay. Incidentally, communication within the system, for example, in cases where the controller is divided into a section controlling the reaction force attachment and a section controlling the steering mechanism, is typically conducted via dedicated high-speed communication lines. For example, in driving mode, there is no delay in the signal for the current supplied to the steering motor.

[0024] For example, the above correction can be made such that the operating reaction force increases as the operating speed of the operating component increases. For example, given that the above delay increases with the operating speed, such a correction is suitable for mitigating the effect of the above delay.

[0025] The aforementioned correction can also be made, for example, by adding a compensation component determined based on the operating speed of the control unit to the component determined by the steering force-related command from the simulator (hereinafter sometimes referred to as the "steering force command-based component," or simply the "command-based component"). In this case, the compensation component can also be determined by taking into account the driver's operating force applied to the control unit, as will be described later. Specifically, for example, the compensation component can also be determined to decrease as the operating force increases. Furthermore, the compensation component can also be determined by taking into account the speed of the simulated vehicle in the simulator that is the object of the action. Specifically, for example, the compensation component can also be determined to decrease as the speed decreases. Attached Figure Description

[0026] Figure 1 This is a diagram showing the overall structure of the steering system in an embodiment.

[0027] Figure 2 This is a block diagram illustrating the functional structure of the controller of the steering system in an embodiment.

[0028] Figure 3 It 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 commands or signals from the driving simulator.

[0029] Figure 4 It is a diagram representing the mapping referenced when determining the component of the reaction force based on the steering force-related instructions from the driving simulator.

[0030] Figure 5 It is a diagram representing the component of the operational reaction force referenced when determining the signal from the driving simulator related to the vertical acceleration of the simulated vehicle.

[0031] Explanation of reference numerals in the attached figures:

[0032] 10…Steering wheel (operating component); 12…Reaction force actuator (reaction force auxiliary 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; 115…Vertical and vertical acceleration 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 power control unit; 144…Basic compensation component determination unit; 148…Correction unit; 150…Operating… 152…Vehicle speed gain determination unit; 164…Second vehicle speed gain determination unit; Tc…Reaction torque; Tca…Auxiliary component; Tcs…Steering force basis component; Tcd…Steering angle basis component; Tcb…Steering current basis component; Tcc…Analog component; Tce…Estimated actual steering force basis component; Tcf…Basic compensation component; Tcg…Compensation component; Tch…Simulator command component; Tci…Vertical and vertical acceleration basis component; Tcj… Basically, the acceleration is based on the following components: δ…operation angle; δ'…operation speed; ω…steering angle; ω*…target steering angle; Is…steering current; v…vehicle speed; vr…actual vehicle speed; vs…simulated vehicle speed; vl…low vehicle speed; vh…high vehicle speed; Kb…current-steering force conversion gain; θ…simulator command value; Gz…vertical acceleration; Ka…contribution change gain; Ko…operation torque based gain; Kv…vehicle speed based gain; Kv2…second vehicle speed based gain; f(Gz)…variation frequency. Detailed Implementation

[0033] The steering system, as an embodiment of the present invention, will now be described in detail with reference to the accompanying drawings as a way of implementing the present invention. It should be noted that, in addition to the following embodiments, the present invention can also be implemented in various forms by those skilled in the art making various modifications and improvements to the solutions described in the foregoing summary based on their professional knowledge.

[0034]

Example

[0035] [1] Overall structure of the steering system

[0036] The steering system of this embodiment (hereinafter sometimes referred to as "this steering system" or "this system") is a steer-by-wire system capable of steering the wheels independently of the driver's operating force applied to the operating components, such as... Figure 1 As shown, the system comprises a steering wheel 10 as an operating component, a reaction force actuator 12 connected to the steering wheel 10 as a reaction force actuation 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. Incidentally, the steering wheel 10 is operated by the driver's rotation, and the reaction force actuator 12 is configured to receive this operation and, more specifically, to apply a reaction force (hereinafter sometimes referred to as "operation reaction force") to the steering wheel 10. Furthermore, the steering wheel 10 and the reaction force actuator 12 together constitute the operating device 18 of this steering system.

[0037] The reaction force actuator 12 comprises a steering column 20 supported by a reinforcement of the instrument panel, a steering shaft 22 held rotatably by 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 mounted at the rear end of the steering shaft 22. Detailed descriptions of the power transmission mechanism are omitted, but it comprises a worm gear mounted on the motor shaft of the reaction force motor 24, and a worm wheel mounted on the steering shaft 22 and meshing with the worm gear. 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 applies a reaction force torque as an operating reaction force to the steering wheel 10 connected to the steering shaft 22.

[0038] The steering actuator 16 comprises a generally cylindrical housing 30 supported by the chassis in a left-right extending posture, a steering rod (rack rod) 32 held by the housing 30 in a non-rotatable but laterally movable manner, 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. Specifically, each tie rod 34 is connected via a ball joint to a steering knuckle arm, which holds the wheel 14 rotatably and is held steerable by the suspension arm.

[0039] A threaded groove 36 is formed in the steering lever 32. Although not shown in the figure, within the housing 30, a nut holding the bearing balls threadedly engaged with the groove 36 is kept immobile but capable of rotation. That is, the steering lever 32 and the nut constitute a ball screw mechanism. A steering motor 38, which functions as an electric motor, is attached to the housing 30. This steering motor 38 rotates the nut via a power transmission mechanism. Incidentally, although the power transmission mechanism is not shown in the figure, it comprises a pulley mounted on the motor shaft of the steering motor 38 and a synchronous belt wound around the pulley and the outer circumference of the nut. The steering motor 38 is a three-phase brushless DC motor, functioning as the drive source for the steering actuator 16. By rotating the steering motor 38, the steering lever 32 moves left and right, causing the left and right wheels 14 to turn together.

[0040] The reaction force actuator 12 is controlled by a reaction force electronic control unit (hereinafter sometimes referred to as "reaction force ECU") 40, which is attached to the reaction force motor 24. The reaction force ECU 40 comprises a computer consisting of a CPU, ROM, RAM, etc., and an inverter that serves as 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, which is attached to the steering motor 38. The steering ECU 42 comprises a computer consisting of a CPU, ROM, RAM, etc., and an inverter that serves as the driver (drive circuit) for the steering motor 38, and is powered by a battery.

[0041] The reaction force ECU 40 and the steering ECU 42 work together to form 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. Incidentally, they are also connected to the vehicle's CAN (car area network or controllable area network) 46. Furthermore, the vehicle speed sensor 48, used to detect the actual vehicle speed (vr), is also connected to the CAN 46.

[0042] Regarding control, although the detailed structure of the reaction force actuator 12 is omitted, the reaction force actuator 12 has an operating torque sensor 50 that detects the operating torque To, which is the operating force applied by the driver to the steering wheel 10, by detecting the amount of torsion of the steering shaft 22. Additionally, it 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 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 of the energizing phase.

[0043] Regarding the steering actuator 16, since the steering angle of the wheel 14 is specifically related to the left-right movement of the steering lever 32, a steering angle sensor 56 is provided to detect the movement of the steering lever 32 in order to detect the steering angle of the wheel 14. Simply put, a rack 58 is formed in the steering lever 32, and a pinion shaft 60 meshing with the rack 58 is held by the housing 30. Although the toe angle of the wheel 14 can also be used 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 includes 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.

[0044] 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 hypothetical action object, drive within a hypothetical environment (hypothetical space) and realizes the changes in scenery (environmental components) seen from the simulated vehicle in the form of 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.

[0045] The simulator 70 comprises a simulator body 72 with a computer as its main body, a goggle-style 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 malfunction determiner 76 for determining whether the simulator 70 can operate. Incidentally, 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.

[0046] This system is used for operating the simulated vehicle; 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, the accelerator pedal 80 and brake pedal 82 of the simulated vehicle are also used for operating the vehicle; therefore, the acceleration operation amount sensor 84, which detects the acceleration operation amount λa as the operation amount of the accelerator pedal 80, and the brake operation amount sensor 86, which detects the braking operation amount λb as the operation amount of the brake pedal 82, are also connected to the CAN 46.

[0047] [2] Functions of the controller

[0048] 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 signals input to or output from the components (functional units) shown in the diagram are mostly signals representing values ​​of torque, its components, steering angle, operating angle, etc. However, to avoid lengthy explanations, in the following description, they will be simply represented as inputting or outputting torque, its components, steering angle, operating angle, etc. to or from each component. Furthermore, for ease of understanding, the explanation will proceed in the following order: the actual driving mode of the vehicle, the steering control function implemented by the steering ECU 42 in the driving mode, the reaction force control function implemented by the reaction force ECU 40, and the reaction force control implemented by the reaction force ECU 40 in the simulation mode where driving simulation is performed by the simulator 70.

[0049] (a) Steering control in driving mode

[0050] Steering control is the control of the steering angle ω of the wheels 14, which are steered by the steering actuator 16. The steering ECU 42, which is 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. Furthermore, in reaction force control and steering control, the vehicle speed v is used as the vehicle's travel speed, but the vehicle speed v used differs between driving mode and simulation mode. Specifically, in driving mode, it is the actual travel speed of the vehicle, i.e., the actual vehicle speed vr; in simulation mode, it is the travel speed of the simulated vehicle in the simulator 70, i.e., the simulated 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 simulated vehicle speed vs. sent from the simulator body 72 as the vehicle speed v. The vehicle speed selection unit 105 selects either the actual vehicle speed vr or the simulated vehicle speed vs. based on the simulation affirmative / negative signal Sa sent from the simulation affirmative / negative determiner 76. Specifically, in driving mode, simulation is disabled and the actual vehicle speed (vr) is selected; in simulation mode, simulation is enabled and the simulated vehicle speed (vs) is selected.

[0051] 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 is not a value detected by the steering angle sensor 56, but 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 in a relationship according to a predetermined reduction ratio, so the conversion based on this reduction ratio is performed in the steering angle conversion unit 106.

[0052] The target steering angle determination unit 100 determines the target steering angle ω*, which is the control target 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 (described later). This steering system is one in which the steering 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 the vehicle speed v, referring to stored mapping data. Incidentally, the method for changing the steering ratio γ is a conventional method, and its explanation is omitted here. Furthermore, since the target steering angle ω* can also be used as the target steering angle of the simulated vehicle in the simulation, it is transmitted to the simulator 70 via CAN 46, specifically to the simulator main body 72.

[0053] 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, as the torque to be generated by the steering motor 38. 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, and the steering torque Ts to be generated is determined according to a PID feedback control rule based on this steering angle deviation Δω. The method of determination according to this feedback control rule is a conventional method, and its description is omitted here.

[0054] The steering power control unit 104 is configured to include a frequency converter as a drive circuit (driver) for the steering motor 38. The steering power control unit 104 determines the current to be supplied to the steering motor 38, i.e., the steering current Is, based on the determined steering torque Ts, and supplies this steering current Is from the frequency converter to the steering motor 38. Furthermore, the steering ECU 42 has a current sensor 110 for detecting the actual supplied steering current Is.

[0055] Furthermore, in simulation 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 the signal for the steering torque Ts is not sent to the steering energization control unit 104. This determination and its execution or non-execution are based on the simulation yes / no signal Sa described above.

[0056] (b) Reaction force control in driving mode

[0057] The reaction force ECU 40, which serves as the reaction force control unit, controls the reaction torque Tc applied to the steering wheel 10 via the reaction force actuator 12, which acts as a reaction force amplification device. The reaction force ECU 40 includes an auxiliary component determination unit 112, a steering force basis component determination unit 114, and a vertical acceleration basis component determination unit 115. Each of these units determines an auxiliary component Tca, a steering force basis component Tcs, and a vertical acceleration basis component Tci, which will be explained in detail in the section on reaction force control in simulation mode later.

[0058] The steering force reference component Tcs is determined through the coordinated processing of the steering angle reference component Tcd and the estimated actual steering force reference component Tce. In driving mode, the estimated actual steering force reference component Tce is determined as the steering current reference component Tcb, and in simulation mode, it is determined as the simulation component Tcc, which will be explained in detail later. Because the steering force reference component Tcs contains these components, the steering force reference component determination unit 114 includes a steering angle reference component determination unit 116, a simulation component determination unit 118, a steering current reference component determination unit 120, a portion of the component switcher 122, weighters 124 and 126, and an adder 128.

[0059] In the control of this steering system, since the operating angle δ is used as the operation amount of the steering wheel 10, the reaction force ECU 40, like the steering ECU 42, 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. Since 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, the conversion based on this reduction ratio is performed in the operating angle conversion unit 108.

[0060] Regarding the determination of each component of the reaction torque Tc, in terms of driving modes, the assist component Tca is a component similar to an assist force in 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. Simply put, the assist component Tca is determined to be a value that increases as the operating torque To increases. At high vehicle speeds (v), a smaller value is determined to increase the driver's input to the steering wheel 10, while at low vehicle speeds (v), a larger value is determined to reduce the input. The assist component Tca is the component whose direction is the same as the direction of steering wheel 10 operation, i.e., the steering operation direction.

[0061] The steering force component Tcs can be considered as the central component of the reaction torque Tc; in short, it is the component of the steering force required for the driver to experience the force needed to steer the wheel 14. The steering force component Tcs can also be considered as the axial force component, that is, the component based on the force (axial force) acting axially on the steering rod 32 of the steering actuator 16. The steering force component Tcs is approximately the component in the opposite direction to the steering operation direction.

[0062] The steering angle reference component Tcd, which is one 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 roughly corresponding to the self-centering torque. In other words, it can be considered as a steering force that does not reflect road surface information, such as road surface unevenness that does not affect the vehicle's lateral behavior, or step differences that do affect the vehicle's lateral behavior. Although a detailed description of the steering angle reference component determination unit 116 is omitted, the steering angle reference component determination unit 116 determines the steering angle reference component Tcd according to a prescribed mapping 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. The steering angle reference component Tcd is determined to be a value that increases as the target steering angle ω* increases, or a value that increases as the vehicle speed v increases.

[0063] As explained above, the analog component Tcc determined by the analog component determination unit 118 is the estimated actual steering force basis component Tce in simulation 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.

[0064] The steering current reference component Tcb, which is the estimated actual steering force reference component Tce in driving mode, differs from the steering angle reference component Tcd. It reflects the influence of road surface information mentioned above; in other words, it is, for example, a component used to realize the force exerted on the wheel 14 from the road surface that is also widely experienced. 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-to-steering force conversion gain Kb.

[0065] The coordination between the steering angle reference component Tcd and the estimated actual steering force reference component Tce is performed as follows: The estimated steering angle reference component Tce is multiplied by a weighting coefficient α (0 < α < 1) using weighter 124. The steering angle reference component Tcd is multiplied by 1 using weighter 126, and the result is subtracted from the weighting coefficient α. These multiplied values ​​are then added together using adder 128 to determine the steering force reference component Tcs. Detailed explanations are omitted, but the weighting coefficient α can be set to a fixed value, or it can be set to vary based on various factors such as vehicle speed v, road surface conditions, and vehicle driving conditions.

[0066] The reaction torque Tc is determined by synthesizing 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 through the synthesizer 130. The determined reaction torque Tc is input to the reaction force energizing control unit 132. The reaction force energizing control unit 132 is configured to include a frequency converter as a drive circuit (driver) for the reaction force motor 24. The reaction force energizing control unit 132 determines the current to be supplied to the reaction force motor 24, i.e., the reaction force current Ic, based on the reaction torque Tc, and supplies the reaction force current Ic from the frequency converter to the reaction force motor 24.

[0067] (c) Reaction force control in simulation mode

[0068] As explained earlier, in simulation mode, instead of the aforementioned steering current reference component Tcb, the simulation component Tcc is used to determine the estimated actual steering force reference component Tce. Additionally, in simulation mode, an upper and lower acceleration reference component Tci is added as one component of the reaction torque Tc. Otherwise, the reaction force control in simulation mode is the same as in driving mode. See below for further details. Figure 3 The block diagram explains the functions of the analog component Tcc and the analog component determination unit 118 that determines the analog component Tcc, as well as the functions of the vertical acceleration reference component Tci and the vertical acceleration reference component determination unit 115 that determines the vertical acceleration reference component Tci.

[0069] i) Analog components and analog component determination unit

[0070] like Figure 3 As shown in block diagram (a), the simulator command value θ, sent from the simulator body 72 via CAN 46, is input to the simulation component determination unit 118. This simulator command value θ is an index indicating the estimated actual steering force basis component Tce to be generated by the simulator 70. The simulator command component Tch is determined by multiplying it by the conversion gain Kc using the conversion gain multiplier 140. Incidentally, if the simulator command value θ is a command value 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.

[0071] As described above, the simulator command value θ is sent from the simulator body 72 via communication, thus causing 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 is performed as described below.

[0072] The operating angle δ, calculated by the operating angle conversion unit 108, is input to the analog component determination unit 118. The analog component determination unit 118 has a differentiator 142, which calculates the operating speed δ' (=dδ / dt) of the steering wheel 10, which is an operating component. The basic compensation component determination unit 144 is referenced in… Figure 4 The basic compensation component determination mapping, represented graphically in (a), determines the basic compensation component Tcf based on the operating speed δ'. Considering that the faster the operating speed δ', the greater the delay, the basic compensation component determination mapping is set such that the basic compensation component Tcf increases as the operating speed δ' increases.

[0073] The basic compensation component determination mapping can also be set as shown by the dashed line in the table, where 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, thereby impairing the clarity of the steering wheel 10's handling feel and reducing the sense of presence in the simulation. Therefore, as shown by the solid line in the table, a non-linear basic compensation component determination mapping can also be used, where the basic compensation component Tcf is smaller in the region where the delay is relatively small with respect to the operating speed δ', i.e., in the region where the operating speed δ' is low. Incidentally, if the basic compensation component Tcf varies linearly with respect to the operating speed δ', there is no need to deliberately use mapping, and the basic compensation component Tcf can also be determined based on a fixed gain setting.

[0074] In this 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 by the contribution change gain multiplier 146 to determine the final basic compensation component Tcf. This contribution change gain Ka is used to change 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 according to the simulated vehicle speed vs, the road surface on which the simulated vehicle travels, the driving state of the simulated vehicle, etc. However, if the contribution change function is also considered for the above-mentioned basic compensation component determination mapping, the contribution change gain multiplier 146 may not be provided.

[0075] 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.

[0076] 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 information such as the reduction in operating reaction force at the tire grip limit is no longer transmitted to the driver. The operating torque based gain Ko is set precisely to take this into account. The operating torque based gain determination unit 150, based on the operating torque To detected by the operating torque sensor 50, determines... Figure 4 The operating torque based gain Ko is determined by the graph-based mapping in (b). Based on this determined operating torque based gain Ko, the compensation component Tcg becomes smaller in the high operating torque region where higher lateral acceleration during cornering occurs. Alternatively, the operating torque based gain unit 150 can be configured to input information about the lateral acceleration during cornering generated in the simulated vehicle from the simulator body 72 to the reaction force ECU 40, replacing the operating torque To, and determine the operating torque based gain Ko based on this lateral acceleration. 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 the lateral acceleration. Incidentally, in this case, it is preferable to refer to the operating torque based gain unit 150 as the lateral acceleration based gain unit, and the operating torque based gain Ko as the lateral acceleration based gain.

[0077] The vehicle speed-based gain Kv is used to adjust the compensation component Tcg based on the vehicle speed v, specifically based on the simulated 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 corresponding to the operation of the steering wheel 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 4The vehicle speed-based gain Kv is determined by the speed-based gain mapping shown in graph (c). Based on the speed-based gain Kv determined in this way, the compensation component Tcg increases as the vehicle speed v increases.

[0078] The compensation component Tcg determined by the correction unit 148 is added to the simulator instruction component Tch by the adder 154. That is, the simulator instruction component Tch is corrected by the compensation component Tcg, and the simulation component Tcc is determined as a result.

[0079] Regarding the steering force reference component Tcs, the reaction force control in simulation mode can be summarized as follows: In driving mode, the reaction torque Tc, which is the operating reaction force, is determined based on the steering force reference component Tcs, which is determined based on the current Is supplied to the steering motor 38. Conversely, in simulation mode, the reaction torque Tc, which is the operating reaction force, is determined based on a component obtained by correcting the simulator command component Tch based on the operating speed δ' of the steering wheel 10, which is the operating component. The simulator command component Tch is a command reference component (steering force command reference component) based on the simulator command value θ, which is a command from the simulator 70. This correction is performed to compensate for the delay in the command from the simulator 70; specifically, the reaction 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, determined based on the operating speed δ' of the steering wheel 10, to the simulator command component Tch. Furthermore, the compensation component Tcg is determined by also taking into account the operating torque To applied to the steering wheel 10 as an operating force, or the simulated vehicle speed vs, which is the driving speed of the simulated vehicle in the simulator 70, which is the object of the action.

[0080] ii) Vertical acceleration components and the component determining vertical acceleration

[0081] like Figure 3 As shown in block diagram (b), the vertical acceleration determination unit 115 receives a signal for the vertical acceleration Gz of the simulated vehicle transmitted from the simulator body 72 via CAN46. This vertical acceleration Gz varies periodically, so that only the component of the variation frequency f(Gz) within a set range is extracted by the bandpass filter 160.

[0082] The bandpass filter 160 is configured to change the set range of the frequency f (GHz) of the extracted component based on the vehicle speed v (simulated vehicle speed vs), i.e., to set the frequency band. For details, refer to... Figure 5The frequency extraction mapping, represented graphically in (a), extracts the vertical acceleration Gz of the variable frequency f(Gz) of a set frequency band. Incidentally, in the graph, the horizontal axis represents the vehicle speed v, and the vertical axis represents the variable frequency f(Gz) that becomes the center value of the set frequency band, i.e., the center value f0(Gz). The bandpass filter 160 extracts the vertical acceleration Gz of a set width of frequency band centered on this variable frequency f(Gz). Furthermore, the solid line in the graph represents the center value f0(Gz) of the frequency extraction mapping used in this bandpass filter 160, in which the center value f0(Gz) increases linearly with increasing vehicle speed v. Alternatively, instead of such a frequency extraction mapping, a frequency extraction mapping in which the center value f0(Gz) changes nonlinearly with respect to vehicle speed v can be used, as shown by the dashed line or single-dot line in the graph. Specifically, the frequency band is set, that is, the range of frequency f (Gz) is set, for example, when the vehicle speed v is 50km / hr, the center value of frequency f0 (Gz) can be a few Hz to 30Hz.

[0083] The vertical acceleration Gz extracted as described above is multiplied by the conversion gain Kd in the conversion gain multiplier 162 to determine the basic vertical acceleration basis component Tcj. In short, the conversion gain Kd is the gain used to convert the units of the vertical acceleration Gz to the basic vertical acceleration basis component Tcj.

[0084] On the other hand, the vertical acceleration determination unit 115 has a second vehicle speed determination unit 164 that determines the second vehicle speed determination gain Kv2. The second vehicle speed determination gain Kv2 is a gain used to change the essentially vertical acceleration determination component Tcj according to the vehicle speed v. The second vehicle speed determination unit 164 refers to... Figure 5The second vehicle speed gain determination mapping, represented graphically in (b), is based on vehicle speed v (simulated vehicle speed vs) to determine the second vehicle speed gain Kv2. According to this second vehicle speed gain determination mapping, in the medium vehicle speed region, the second vehicle speed gain Kv2 is determined to be 1; in the low vehicle speed region where vehicle speed v is less than the low vehicle speed vl, the second vehicle speed gain Kv2 is determined to be 0; and in the high vehicle speed region where vehicle speed exceeds the high vehicle speed vh, the second vehicle speed gain Kv2 is determined to be [value missing], decreasing further from 1 as vehicle speed v increases. Incidentally, the low vehicle speed vl and high vehicle speed vh can be arbitrarily set according to the characteristics of the required reaction torque Tc, but in this second vehicle speed gain determination mapping, for example, the low vehicle speed vl is set to 10 km / hr and the high vehicle speed vh is set to 90 km / hr. Alternatively, the second vehicle speed can be mapped based on gain to make the second vehicle speed based on gain Kv2 have the conversion function of the aforementioned conversion gain Kd. In this case, the conversion gain Kd and the conversion gain multiplier 162 can be omitted.

[0085] The multiplier 166 multiplies the basic vertical acceleration reference component Tcj, as determined above, by the second vehicle speed reference gain Kv2 to determine the vertical acceleration reference component Tci. Using the second vehicle speed reference gain Kv2, in the low vehicle speed region, the vertical acceleration reference component Tci is set to 0, and in the high vehicle speed region, the vertical acceleration reference component Tci is set to decrease as the vehicle speed v increases.

[0086] A limiter 168 is provided in the vertical acceleration basis component determination unit 115 to allow the determined vertical acceleration basis component Tci to pass through the limiter 168. The limiter 168 has the function of limiting the vertical acceleration basis component Tci to below a set value. Specifically, the vertical acceleration Gz oscillates in a manner that takes positive and negative values, and the vertical acceleration basis component Tci also oscillates in a manner that takes positive and negative values. Therefore, the limiter 168 limits the absolute value of the vertical acceleration basis component Tci to below the set value.

[0087] like Figure 2 As shown in the block diagram, the vertical acceleration component Tci is input to the synthesizer 130 via component switcher 122. Component switcher 122, based on the previously described analog yes / no signal Sa, switches the generation / disabling of the vertical acceleration component Tci in analog mode and in driving mode. That is, the reaction torque Tc is determined such that the vertical acceleration component Tci is present only in analog mode.

[0088] Regarding the vertical acceleration component Tci, the reaction force control described above in simulation mode can be summarized as follows: In simulation mode, an operating torque Tc, containing the vertical acceleration component Tci based on a signal related to the vertical acceleration Gz of the simulated vehicle, is applied to the steering wheel 10. Since the vertical acceleration Gz varies approximately periodically depending on the road surface characteristics of the simulated vehicle, the vertical acceleration component Tci also varies approximately periodically. As a result, the steering wheel 10 vibrates according to this variation. For example, in the case where the simulated vehicle deviates from its path on a ring road, the amplitude of this vibration becomes relatively large, and the driver experiences a suitable sense of presence.

[0089] In this system, the vertical acceleration component Tci is determined based on the vertical acceleration Gz within a set range of the variation frequency f (Gz). This set range is configured to increase as the simulated vehicle speed vs increases, which is the speed v of the simulated vehicle. Furthermore, in this system, when the simulated vehicle speed vs is lower than the low vehicle speed vl, the vertical acceleration component Tci is 0; when the simulated vehicle speed vs exceeds the high vehicle speed vh, the vertical acceleration component Tci decreases as the simulated vehicle speed vs increases. Moreover, the vertical acceleration component Tci is limited to below a set value.

Claims

1. A steering system, wherein, have: The operating device has an operating component operated by a driver and a reaction force affixing device, the reaction force affixing device adding an operating reaction force as a reaction force to the operation of the operating component; Steering system, which turns the wheels, and has an electric motor as the drive source, namely the steering motor; as well as The controller controls the steering mechanism and the reaction force attachment. The steering system is a steer-by-wire type steering system installed in vehicles equipped with driving simulators. in, The operating device is used in the simulation mode activated by the driving simulator to operate the simulated vehicle that becomes the object of the action in the driving simulator. The controller is configured to, in this simulation mode, apply an operational reaction force containing an up-and-down acceleration component to the reaction force attachment device, the up-and-down acceleration component being based on a signal from the simulated driving device related to the up-and-down acceleration of the simulated vehicle.

2. The steering system according to claim 1, wherein, The controller is configured to determine the vertical acceleration basis component based on the vertical acceleration within a set range of varying frequency.

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

4. The steering system according to claim 1, wherein, The controller is configured such that when the simulated vehicle's speed is lower than a set low speed, the vertical acceleration is determined to be 0 based on its components.

5. The steering system according to claim 1, wherein, The controller is configured such that, when the speed of the simulated vehicle exceeds a set high speed, the vertical acceleration component is reduced as the speed increases.

6. The steering system according to claim 1, wherein, The controller is configured to limit the vertical acceleration components to below a set value.

7. The steering system according to claim 1, wherein, The controller is configured to apply an operational reaction force containing a steering force-based component to the reaction force-adding device, the steering force-based component being based on a steering force that steers the wheels. The controller is configured to determine the steering force basis component based on steering force-related instructions from the simulated driving device in simulation mode.

8. The steering system according to claim 7, wherein, The controller is configured to determine the steering force based on the current supplied to the steering motor in the actual driving mode of the vehicle.

9. The steering system according to claim 7, wherein, The controller is configured to, in simulation mode, determine the steering force-related component by correcting the operating speed of the operating component based on the component determined by the steering force-related command from the driving simulator.

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