Steering system

Abstract

To provide a steer-by-wire type steering system of high practicability.SOLUTION: During normal operation, an urging force TqC applied to an operation member 10 functions as operation reaction force (TqC-A, TqC-C, TqC-L). During automatic steering operation in automatic parking or the like, the urging force is used to achieve operation of the operation member in response to steering of the wheels (TqC-M), while preventing at least a part of the urging force (TqC-C, TqC-L) during normal operation from being generated. During the automatic steering operation, appropriate operation of the operation member according to the steering of the wheels is thereby secured.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a steering system mounted on a vehicle. [Background technology]

[0002] Recently, development of a steering system that realizes steering of wheels according to the operation of an operating member such as a steering wheel by a steering device having a drive source without relying on the operating force applied by a driver to the operating member, i.e., a so-called steer-by-wire type steering system, is underway. In the steer-by-wire type steering system, a reaction force imparting device, i.e., a biasing device that generates a biasing force to bias the operating member, is provided in order to impart an operation reaction force, which is a reaction force against the operation of the operating member, to the operating member. As the biasing force for imparting the operation reaction force, for example, as described in the following patent document, it is also considered that the biasing device generates a biasing force consisting of several components and changes the ratio of the components depending on the situation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5994868 Summary of the Invention [Problem to be solved by the invention]

[0004] In a steering system, for example, when automatically parking a vehicle, an operation to automatically steer the wheels without operating an operating member, i.e., an automatic steering operation, may be performed. In a steer-by-wire steering system, the steered wheels and the operating member are not mechanically connected, so that in the automatic steering operation, the biasing force of the biasing device can be used to realize the operation of the operating member corresponding to the steering of the wheels. However, since the biasing device is originally a device for generating a biasing force to impart an operation reaction force, it is predicted that the operation member will not operate properly corresponding to the steering of the wheels in the automatic steering operation if a biasing force consisting of the above-mentioned several components is generated. In other words, there is a possibility that the operating member will operate unnaturally. Such an operation of the operating member may reduce the practicality of the steer-by-wire steering system. The present invention has been made in consideration of such a situation, and an object of the present invention is to provide a steer-by-wire steering system with high practicality. [Means for solving the problem]

[0005] In order to solve the above problems, the steering system of the present invention comprises: A steer-by-wire type steering system equipped in a vehicle includes an operating member operated by a driver, a biasing device that generates a biasing force to bias the operating member, a steering device that steers wheels, and a controller that controls the biasing device and the steering device, the controller comprising: In a normal operation, the steering of the wheels is realized in response to the operation of the operating member, and the biasing force functions as an operation reaction force against the operation of the operating member. In an automatic steering operation in which the wheels are steered without the operation of the operating member, the operation of the operating member in response to the steering of the wheels is realized by the biasing force, and at least a part of the biasing force in the normal operation is not generated. 、 the biasing force includes a plurality of components, one of which is an active operation component for actively operating the operating member in response to steering of the wheels, The controller: The positive action component is generated only during the automatic steering operation, and a non-generated component during automatic steering, which is at least a part of the components other than the positive action component, is not generated during the automatic steering operation, and During the automatic steering operation, the automatic steering operation is configured such that at least a portion of the components that do not occur during automatic steering is not generated by maintaining at least a portion of the components while adding a component to the positive operation component to offset the at least a portion of the components. Effect of the Invention

[0006] According to the steer-by-wire type steering system of the present invention, in the automatic steering operation, at least one component of the biasing force by the biasing device that functions as an operation reaction force in the normal operation is no longer generated, so that the appropriate operation of the operating member in response to the steering of the wheels is ensured.

[0007] The automatic steering operation in the steering system of the present invention is suitable for automatic parking, where the wheels of the vehicle are automatically steered without the driver operating an operating member, although the application is not particularly limited. In addition, transportation of the vehicle by automatically driving the vehicle within a business facility such as a production factory (hereinafter, sometimes referred to as "automatic driving transportation") is also being considered, and the automatic steering operation in the steering system of the present invention is suitable for this automatic driving transportation.

[0008] As described above, the biasing force can be made up of various components. In the case of normal operation, for example, the biasing force can include an assist component for assisting the driver in operating the operating member, a compensation component for compensating for the operating feeling of the operating member given to the driver, and a steering load dependent component based on the load of the steering device against the steering of the wheels.

[0009] Supplementally, the assist component is a component similar to the assist force in so-called power steering, and can be a component that increases as the operating force applied by the driver to the operating member increases, for example.

[0010] The compensation components can include, for example, a return compensation component that returns and maintains the operating member in the operating position when the vehicle is moving straight (hereinafter sometimes referred to as the "neutral position"), a hysteresis compensation component for imitating the hysteresis characteristics due to mechanical friction when operating the operating member, a damping compensation component for viscously suppressing micro-vibrations that occur in the operating member, and an inertia compensation component for suppressing the feeling of resistance when starting to operate the operating member and the feeling of slippage when the operation ends.

[0011] The steering load dependent component can be considered to be the central component of the operation reaction force, and is a component that allows the driver to feel the steering force, which is the force required to steer the wheels. The steering load dependent component can be considered to be a component based on the axial force acting on the steering rod (sometimes called a "rack bar") that connects the left and right wheels in a so-called standard steering system. It is a concept that broadly includes not only the above-mentioned steering force, but also forces acting on the wheels from the road surface. The steering load dependent component is generally a force acting in the opposite direction to the assist component described above. Simply put, the assist component acts in the same direction as the operation direction of the operating member, and the steering load dependent component acts in the opposite direction to the operation direction of the operating member.

[0012] The turning load-dependent component can include several components, such as a theoretical component which is a theoretical component based on the amount of operation of the operating member and the amount of steering of the wheels, an actual load-dependent component which indicates the actual load which can be determined based on the current supplied to the electric motor when the steering device has an electric motor as a driving source, a turning end-dependent component which provides a sense of the turning end, and a turning hysteresis-dependent component which is based on the hysteresis characteristics of the steering device.

[0013] The components described above are components that can be generated in normal operation, but in automatic steering operation, in order to realize the operation of the operating member in response to the steering of the wheels, a positive action component can be generated as a component for actively operating the operating member in response to the steering of the wheels. It is desirable that this positive action component be the main biasing force in automatic steering operation. In view of this, since the above-mentioned assist component, compensation component, steering load dependent component, etc. that constitute the operation reaction force may hinder the proper operation of the operating member in automatic steering operation, it is desirable that at least a part of these components, in other words, at least a part of all components except the positive action component, are not generated in automatic steering operation as "components not generated during automatic steering".

[0014] The positive action component may be determined, for example, based on the steering amount of the wheels, by determining the operation amount of the operating member corresponding to that steering amount as a target operation amount, and then determining the positive action component in accordance with a feedback control law based on the deviation of the actual operation amount from the target operation amount.

[0015] If the positive action component is generated only during automatic steering operation, it is expected that the operating member will move abruptly depending on whether or not the positive action component is generated. In view of this, it is desirable to gradually increase the positive action component at the start of automatic steering operation and gradually decrease it when returning to normal operation, that is, at the end of automatic steering operation. On the other hand, if the component not generated during automatic steering is suddenly changed at the start of automatic steering operation, it is expected that the operating member will move abruptly due to the sudden change. In view of this, it is desirable to gradually decrease the component not generated during automatic steering at the start of automatic steering operation.

[0016] As an example of a mode in which at least a part of the components not generated during automatic steering are not generated during automatic steering operation, for example, a component for offsetting at least a part of the components not generated during automatic steering (hereinafter sometimes referred to as an "offsetting component") can be added to the active action component while maintaining at least a part of the components not generated during automatic steering during automatic steering operation. To explain a more specific mode, the components not generated during automatic steering can be divided into a same direction component that acts in the same direction as the active action component with respect to the operation of the operating member, i.e., with respect to the direction in which the operating member moves, and an opposite direction component that acts in the opposite direction to the active action component. When an opposite direction component is not generated during automatic steering operation, for example, it is possible to offset the opposite direction component by adding a component of the same magnitude as the opposite direction component to the active action component.

[0017] In the aspect of adding the offsetting component, by quickly deciding, in other words, quickly reducing the offsetting component together with at least a portion of the component to be offset at the end of the automatic steering operation, it is possible to sufficiently reduce or prevent inappropriate operation of the operating member at the end of the automatic steering operation due to the remaining of the at least a portion of the component. If at least a portion of the component to be offset is the opposite direction component, by quickly deciding, in other words, quickly reducing the opposite direction component together with the component of the same magnitude at the end of the automatic steering operation, it is possible to sufficiently reduce or prevent inappropriate operation of the operating member at the end of the automatic steering operation due to the remaining of the opposite direction component. The above-mentioned turning load dependent component is an opposite direction component and is highly likely to remain even after the automatic steering operation is terminated, and there is a great advantage in quickly deciding the turning load dependent component. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram illustrating a hardware configuration of the steering system of the present invention. [Diagram 2] FIG. 2 is a functional block diagram showing a functional configuration of a controller of the steering system of the present invention. [Diagram 3]FIG. 4 is a block diagram showing first to third switches included in the functional configuration of the controller. [Figure 4] 11 is a table showing whether or not various components of a biasing force applied to an operating member are generated in each of normal operation and automatic steering operation. [Diagram 5] 5 is a graph showing changes in the biasing force on the operating member and some of its components when switching between normal operation and automatic steering operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A steer-by-wire type steering system according to an embodiment of the present invention will be described in detail below with reference to the drawings. In addition to the following embodiment, the present invention can be embodied in various forms including those described in the above section on "Modes of the Invention" and various modifications and improvements based on the knowledge of those skilled in the art. EXAMPLES

[0020] [A] Steering system hardware configuration The steering system of the embodiment is a steer-by-wire type steering system, as shown diagrammatically in FIG. 1, and is roughly composed of an operation section 14 having a steering wheel 10 which is an operating member operated by the driver and a reaction force actuator 12 for applying an operating reaction force to the steering wheel 10, a steering section 20 having a steering actuator 18 as a steering device for steering the wheels 16, and a steering electronic control unit (hereinafter sometimes abbreviated as "steering ECU") 22 as a controller which controls the reaction force actuator 12 and the steering actuator 18.

[0021] Regarding the operation unit 14, the steering wheel 10 is fixed to the tip of the steering shaft 30, and the reaction force actuator 12 has a reaction force motor 32 as a power source, and a reduction mechanism 38 consisting of a worm 34 and a worm wheel 36 attached to the motor shaft of the reaction force motor 32, and the worm wheel 36 is attached to the steering shaft 30. The reaction force actuator 12 generates an urging torque (a sub-concept of "urging force") Tq that depends on the motor torque of the reaction force motor 32. C and biases the steering wheel 10 via the steering shaft 30 with the biasing torque Tq C The reaction torque Tq (which is a lower concept of "operation reaction force") against the operation of the steering wheel 10 C By making it function as a reaction force applying device, the force applying torque Tq C Since it mainly functions as a reaction torque, in the rest of this specification, it will be referred to as the reaction torque Tq C This will sometimes be referred to as ".

[0022] The reaction motor 32 is a three-phase brushless motor, and the rotation phase of the motor shaft of the reaction motor 32, or simply the rotation angle of the reaction motor 32 (hereinafter sometimes referred to as the “reaction motor rotation angle”) θ MC The steering shaft 30 has a structure in which two shaft portions, an upper portion and a lower portion, are connected via a torsion bar 42, and the operation unit 14 detects the amount of twist of the torsion bar 42 to thereby determine the operation torque (which is a sub-concept of "operation force") Tq applied to the steering wheel 10 by the driver. O The reaction force motor rotation angle θ detected by the motor rotation angle sensor 40 is provided. MC and the operation torque Tq detected by the operation torque sensor 44 O A signal regarding the above is sent to the steering ECU 22.

[0023] Regarding the steering unit 20, the steering actuator 18 has a steering rod 50 extending left and right, and a housing 52 that holds the steering rod 50 so that it can move left and right. A screw groove 54 constituting a ball screw mechanism is formed in the steering rod 50, and a nut 56 that holds a bearing ball is held in the housing 52 so as to be rotatable but immovable left and right so as to be screwed into the screw groove 54. A steering motor 58 as a drive source is disposed in the housing 52, and a timing belt 62 is wound around a pulley 60 attached to a motor shaft of the steering motor 58 and an outer periphery of the nut 56 that functions as another pulley. The rotation of the motor shaft of the steering motor 58, i.e., the rotation of the steering motor 58, rotates the nut 56, and the steering rod 50 moves left and right. The left and right ends of the steering rod 50 are connected to knuckle arms of steering knuckles that rotatably hold the left and right wheels 16, respectively, via ring rods (not shown). As the steering rod 50 moves left and right, the left and right wheels 16 are turned, that is, steered.

[0024] A rack 64 is formed on the steering rod 50, and a pinion shaft 66 is rotatably held in the housing 52 in a state of meshing with the rack 64. The rack 64 and the pinion shaft 66 do not necessarily have to be provided in the steering actuator 18 constituting the present steer-by-wire type steering system. As can be easily understood, a general power steering system is realized by connecting the pinion shaft 66 to the steering shaft 30 of the operation unit 14. In other words, the present steering system is constructed by slightly modifying the structure of a general power steering system. The steering rod 50 can also be called a rack bar, since the rack 64 is formed on the steering rod 50.

[0025] The steering motor 58 is a three-phase brushless motor, and the rotation phase of the motor shaft of the steering motor 58, or simply, the rotation angle of the steering motor 58 (hereinafter sometimes referred to as the "steering motor rotation angle") θ MSThe motor rotation angle sensor 68 detects the steering motor rotation angle θ MS The signal is sent to the steering ECU 22.

[0026] The steering ECU 22 is configured to include a computer constituted by a CPU, ROM, RAM, etc., an inverter which is a drive circuit for the reaction force motor 32, and an inverter which is a drive circuit for the steering motor 58. As will be described in detail later, this steering system executes an automatic steering operation in which the wheels 16 are automatically steered without the driver's operation of the steering wheel 10 when the vehicle is automatically parked. In order to execute this automatic steering operation, the steering ECU 22 is connected to an automatic parking controller 70. The steering ECU 22 also obtains a signal relating to the traveling speed v of the vehicle (hereinafter sometimes abbreviated as "vehicle speed") from a vehicle speed sensor 72 which detects the vehicle speed v.

[0027] [B] Controller Functions Steering ECU 22, which is a controller of this steering system, has a functional configuration as shown in the functional block diagram in FIG. 2. This functional configuration is realized by a computer executing a predetermined program, but may also be realized by a dedicated circuit such as an ASIC. Steering ECU 22 can be roughly divided into a reaction force control unit 100 and a steering control unit 102. Most of what is input to or output from each component shown in the figure are signals indicating values ​​of torque, its components, steering angle, operation angle, etc., but in consideration of the redundancy of the explanation, in the following explanation, it will be expressed simply that torque, its components, steering angle, operation angle, etc. are input to or output from each component.

[0028] (a) Reaction force control section The reaction force control unit 100 controls the biasing torque Tq C (Reaction torque Tq C) and each of them controls the bias torque Tq C The assist component Tq C-A , compensation component Tq C-C ,active motion component Tq C-M , steering load dependent component Tq C-L The system includes an assist component determiner 104, a compensation component determiner 106, an active action component determiner 108, and a steering load dependent component determiner 110, which determine the above components, respectively.

[0029] In the control of this steering system, the operation angle θ O is used, the reaction force control unit 100 detects the reaction force motor rotation angle θ MC The operation angle θ O The operation angle conversion unit 112 converts the operation angle θ O and reaction motor rotation angle θ MC Since the integrated amount of the steering wheel 10 is related to the reduction ratio of the reduction mechanism 38, the conversion is performed based on the reduction ratio. Although a detailed explanation is omitted, the steering system of the present invention is configured such that the steering wheel 10 is rotated at an operating angle θ O The operation angle conversion unit 112 converts the operation angle θ based on the detection value of the sensor (not shown). O The calibration is performed at a predetermined timing.

[0030] In addition, the reaction force control unit 100 controls the steering angle θ as the amount of steering of the wheels 16 in order to perform the automatic steering operation. S and the operating angle θ O The current steering angle θ when the specific steering gear ratio γ0 is reached. S Operation angle θ according to O The target operating angle θ O * The target operation angle determining unit 114 determines the target operation angle as follows:

[0031] The above-mentioned biasing torque Tq C The determination of each component is explained in order: Assist component TqC-A is a component similar to the assist force in so-called power steering, and the component determining unit 104 determines the operation torque Tq detected by the operation torque sensor 44. O ,Based on the vehicle speed v, the assist component Tq C-A Simply put, the operating torque Tq O The larger the value, the larger the assist component Tq is determined to be. When the vehicle speed v is high, the assist component Tq is set to a small value in order to make the driver's feeling of operation of the steering wheel 10 (hereinafter, sometimes referred to as "steering operation feeling" or simply "operation feeling") heavier. When the vehicle speed v is low, the assist component Tq is set to a large value in order to make the driver's feeling of operation lighter. C-A The direction of the steering wheel 10 is the same as the steering operation direction.

[0032] Compensation component Tq C-C includes a return compensation component for returning and maintaining the steering wheel 10 in the neutral position, a hysteresis compensation component for imitating the hysteresis characteristics due to mechanical friction in the operation of the steering wheel 10, a damping compensation component for viscously suppressing the micro-vibrations occurring in the steering wheel 10, and an inertia compensation component for suppressing the feeling of sticking at the start of the operation of the steering wheel 10 and the feeling of slippage at the end of the operation. The compensation component determination unit 106 determines these components and adds up the determined components to determine the compensation component Tq C-C Determine.

[0033] Specifically, the return compensation component is the operating torque Tq O , vehicle speed v, operation angle θ O , and its operating angle θ O The operation speed θ obtained by differentiating O ' is determined based on the steering angle θ O The hysteresis compensation component is determined to be a larger value as the operating angle θ O , the vehicle speed v, the hysteresis characteristic is determined so as to be optimized. The damping compensation component is determined based on the vehicle speed v and the steering angle θ O The operation speed θ obtained by differentiatingO ', in short, the operation speed θ O The higher the value, the larger the value is set. The inertia compensation component is determined by the vehicle speed v and the operation speed θ O The operation acceleration θ obtained by further differentiating O " In short, the operation acceleration θ O The higher the value, the larger the compensation component Tq C-C The direction of the steering wheel can be in the same direction or in the opposite direction to the steering direction.

[0034] Steering load dependent component Tq C-L can be considered to be a central component of the reaction torque, and roughly speaking, is a component that allows the driver to feel the steering force, which is the force required to steer the wheels 16. It can also be considered to be a component based on the force (axial force) acting on the steering rod 50 of the steering actuator 18 in its axial direction, and is a component that allows the driver to feel not only the above steering force, but also the force acting on the wheels 16 from the road surface. C-L is generally a component in the opposite direction to the steering direction.

[0035] In detail, the steering load dependent component Tq C-L The steering angle θ of the steering wheel 10 is O and the wheel turning angle θ S The steering load dependent component determination unit 110 determines these components and adds up the determined components to determine the steering load dependent component Tq. C-L Determine.

[0036] Specifically, the theoretical component is a component that does not take into account friction between the road surface and the wheels 16, and is a steering angle θ at which the wheels 16 should be steered. S The target steering angle θ S *In short, the target steering angle θ is calculated based on the self-aligning torque of the wheels 16. S * The larger the value of the actual load dependent component, the larger the vehicle speed v is, and the larger the value of the actual load dependent component, the larger the steering current I S Since the steering current I S Based on this, the steering current I S The larger the value, the larger the end-dependent component is. S * Based on this, the target steering angle θ S * is determined to rise at a steep slope when the steering angle θ approaches the steering end to some extent. O , Based on the vehicle speed v, the hysteresis characteristics are determined to be optimized.

[0037] Active motion component Tq C-M is a component for actively steering the wheels 16, and in this steering system, is a component corresponding to the automatic steering operation when the vehicle performs automatic parking. O * The current operation angle θ O The deviation of the operating angle Δθ O Based on this, according to the feedback control law, the active action component Tq C-M Specifically, proportional control, that is, the operation angle deviation Δθ O In other words, the operation angle deviation Δθ O The larger the positive action component Tq, the larger the value is determined. C-M is a component in the same direction as the direction in which the steering wheel 10 is operated, and is approximately the assist component Tq C-A The same direction component and the steering load dependent component Tq C-L This is the opposite direction component to

[0038] The assist component Tq determined by the assist component determination unit 104 C-A is input to the adder 116, and the compensation component Tq determined by the compensation component determination unit 106 is C-C is input to the adder 116 via the first switch 118. The positive action component Tq determined by the positive action component determining unit 108 C-M is input to the preliminary adder 122 via the second switch 120, and the turning load dependent component Tq determined by the turning load dependent component determination unit 110 is C-L is input to the preliminary adder 122 via the third switch 124. The preliminary adder 122 outputs the input positive action component Tq C-M and steering load dependent component Tq C-L and are added together, and the added component is input to the adder 116. In the adder 116, the input assist component Tq C-A , compensation component Tq C-C ,active motion component Tq C-M and steering load dependent component Tq C-L The sum of the above is input to a final adder 126. The turning load dependent component Tq determined by the turning load dependent component determination unit 110 C-L is also input to a final adder 126 via a third selector 124. The final adder 126 subtracts the steering load dependent component Tq input from the third selector 124 from the component input from the adder 116. C-L is subtracted, resulting in the biasing torque Tq C is determined. Simply put, the first switch 118, the second switch 120, and the third switch 124 are functional units for switching between the presence and absence of generation of a component when switching between normal operation and automatic steering operation.

[0039] The first switch 118 has a functional configuration as shown in Fig. 3(a). More specifically, the first switch 118 includes an operation mode determiner 128, a gain changeover switch 130, a bidirectional change amount limiter 132, and a multiplier 134. The operation mode determiner 128 receives the flag value of the automatic steering flag ASF from the automatic parking controller 70 and the operation torque Tq detected by the operation torque sensor 44. OThe automatic steering flag ASF is set to "1" when automatic steering is instructed (hereinafter, may be referred to as "ASF="1"), and is set to "0" when automatic steering is not instructed (hereinafter, may be referred to as "ASF="0"). The operation mode determiner 128 determines whether ASF is "1" and whether the operation torque Tq O Threshold operating torque Tq O - TH If the two conditions that the steering wheel 10 is not being operated by the driver are met, the operation of the steering system is determined to be automatic steering operation, and if at least one of the two conditions is not met, the operation of the steering system is determined to be normal operation.

[0040] Based on the determination by the operation mode determiner 128, the gain changeover switch 130 outputs 1 when automatic steering is in operation and 0 when normal operation is in operation. The bidirectional change amount limiter 132 prevents a sudden change in value when the gain G switches from 1 to 0 or from 0 to 1. Specifically, when the value of the gain G after a predetermined time pitch has elapsed is a predetermined value or more from the value before the lapse, the change in the gain G is set to the predetermined value. The gain G that has passed through the bidirectional change amount limiter 132 is input to a multiplier 134. The multiplier 134 receives the compensation component Tq determined by the compensation component determination unit 106. C-C is also input, and in the multiplier 134, the gain G is multiplied by the compensation component Tq C-C and the multiplied compensation component Tq C-C is output from the first switch 118.

[0041] The second switch 120 has a functional configuration as shown in Fig. 3(b). More specifically, the second switch 120 includes an operation mode determiner 128, a bidirectional change amount limiter 132, and a multiplier 134, similar to the first switch 118. The second switch 120 also has a gain change switch 136, but unlike the gain change switch 130 of the first switch 118, this gain change switch 136 outputs 0 when automatic steering is in operation and 1 when normal operation is in operation. The positive action component Tq determined by the positive action component determination unit 108 C-M is processed by the second switch 120 and then output from the second switch 120.

[0042] The third switch 124 has a functional configuration as shown in Fig. 3(c). More specifically, the third switch 124 includes an operation mode determiner 128 similar to the first switch 118, a multiplier 134, and a gain changeover switch 136 similar to the second switch 120. The third switch 124 also has a change amount limiter, but the increase direction change amount limiter 138 of the third switch 124 prevents a sudden change in value when the gain G switches from 0 to 1, but allows a sudden change in value when the gain G switches from 1 to 0.

[0043] The third switch 124 further includes a resetter 140. The resetter 140 receives the turning load dependent component Tq determined by the turning load dependent component determiner 110. C-L and the flag value of the automatic steering flag ASF are input. When ASF=“0”, that is, when automatic steering is no longer instructed, the resetter 140 resets the steering load dependent component Tq C-L is reset to 0 once, and when normal operation starts, the steering load dependent component Tq C-L is gradually increased from 0. The resetter 140 outputs the steering load dependent component Tq C-L is output directly to the final adder 126 in addition to the multiplier 134.

[0044] The biasing torque Tq output from the final adder 126 C is input to the reaction force current control unit 142. The reaction force current control unit 142 is configured to include an inverter that is a drive circuit (driver) of the reaction force motor 32. The reaction force current control unit 142 calculates the input biasing torque Tq C Based on this, the reaction current I C Determine the reaction current I C is supplied to the reaction motor 32 from the inverter.

[0045] (b) Steering control section The steering control unit 102 controls the steering angle θ of the wheels 16 which are steered by the steering actuator 18 which is a steering device. S and has a target steering angle determination section 150, a target steering angle changeover switch 152, a steering torque determination section 154, and a steering current control section 156.

[0046] In the control of this steering system, the amount of steering of the wheels 16 is determined by the steering angle θ S is used, the steering control unit 102 detects the steering motor rotation angle θ MS The steering angle θ S Incidentally, the steering angle θ S Alternatively, the toe angle of the wheels 16 may be used, but in the control of the present steering system, the rotation angle of the pinion shaft 66 is used. S and the steering motor rotation angle θ MS Since the integrated amount of is in a relationship corresponding to a predetermined reduction gear ratio, specifically, a reduction gear ratio determined by the reducer included in steering motor 58, the lead angle of the ball screw mechanism of steering actuator 18, the diameter of pinion shaft 66, etc., conversion is performed based on that reduction gear ratio. Although detailed explanation is omitted, this steering system has a sensor (not shown) for detecting the rotation angle from the rotation position of pinion shaft 66 when wheels 16 are in a straight traveling state, and based on the detection value of that sensor, steering angle θ S The calibration is performed at a predetermined timing.

[0047] The target steering angle determination unit 150 determines the operation angle θ O Based on this, the steering angle θ S The target steering angle θ S * The steering system determines the steering gear ratio γ, i.e., the steering angle θ S Operation angle θ O The target steering angle determination unit 150 is a system that can change the ratio of the steering angle θ O Based on the vehicle speed v and the vehicle speed v, the stored map data is referenced to determine the target steering angle θ S * Incidentally, the method for changing the steering gear ratio γ is a common one, and therefore the explanation thereof will be omitted here.

[0048] The target steering angle θ determined by the target steering angle determination unit 150 S * is adopted in normal operation, but in the automatic steering operation described above, the target steering angle θ S * is a target steering angle θ based on a signal sent from the automatic parking controller 70. S * The target steering angle changeover switch 152 changes the target steering angle θ S * Although detailed explanation will be omitted, the target turning angle changeover switch 152 has a determiner similar to the operation mode determiner 128 of the first changeover switch 118 of the reaction force control unit 100, and determines the target turning angle θ S * Switch.

[0049] The steering torque determination unit 154 determines the steering torque Tq required to steer the wheels 16. S This is the functional section that determines the steering torque Tq Scan be considered as, for example, the torque to be generated by the steering motor 58. Specifically, the actual steering angle θ at the present time converted by the steering angle conversion unit 158 S and the target steering angle θ S * Based on this, the target steering angle θ S * The steering angle θ S The deviation of the steering angle Δθ S and the steering angle deviation Δθ S According to the PID feedback control law based on S The method of following this feedback control law is a common one, and the description thereof will be omitted here.

[0050] The steering current control unit 156 is configured to include an inverter that is a drive circuit (driver) of the steering motor 58. The steering current control unit 156 controls the determined steering torque Tq S Based on this, the steering current I S Determine the steering current I S is supplied from the inverter to the steering motor 58. The steering ECU 22 controls the steering current I S The steering wheel has a current sensor 160 for detecting the steering current I S is the steering load dependent component Tq C-L is used to determine.

[0051] [C] The biasing force and its switching during normal operation and automatic steering operation The steering ECU 22 having the above-mentioned functional configuration, more specifically, the reaction force control unit 100 thereof controls the bias torque Tq C As described above, the steering system of the present invention has an operation mode that is switched between normal operation and automatic steering operation for automatic parking, and the biasing torque Tq C can also be switched.

[0052] More specifically, the first switch 118, the second switch 120, the third switch 124, the preliminary adder 122, the adder 116, and the final adder 126 act to adjust the bias torque Tq C Each component of the assist component Tq C-A , compensation component Tq C-C ,active motion component Tq C-M , steering load dependent component Tq C-L Specifically, the generation of the assist component Tq C-A is generated in both normal operation and automatic steering operation, but the compensation component Tq C-C , steering load dependent component Tq C-L can be generated in normal operation, but not in automatic steering operation. Conversely, the active operation component Tq C-M is not generated in normal operation, but is generated in automatic steering operation.

[0053] What I want to explain in particular is the steering load dependent component Tq C-L is at least a part of the non-occurrence component during automatic steering, and the active operation component Tq C-M This steering load dependent component Tq C-L is not simply not generated in automatic steering operation, but is the steering load dependent component Tq C-L is added via the preliminary adder 122 to the positive action component Tq C-M and added to adder 116 to obtain the steering load dependent component Tq C-L As a result, the steering load dependent component Tq C-L The problem is that this will no longer occur.

[0054] As can be seen from the table in Figure 4, in normal operation, the assist component Tq C-A , compensation component Tq C-C , steering load dependent component Tq C-L Therefore, the applied torque Tq C is a reaction torque Tq against the driver's operation of the steering wheel 10. COn the other hand, in the automatic steering operation, the positive action component Tq C-M Including the bias torque Tq C The steering angle θ of the wheel 16 is S Operation angle θ according to O The steering wheel 10 is operated appropriately so that the compensation component Tq C-C , steering load dependent component Tq C-L Since the compensation component Tq is not generated, the proper operation of the steering wheel 10 is not hindered. C-C , steering load dependent component Tq C-L In this way, the steering wheel 10 is prevented from being moved in an inappropriate manner due to the steering force. C-A remains, but the assist component Tq C-A is the operation torque Tq applied to the steering wheel 10 by the driver O In the automatic steering operation that does not assume the operation of the steering wheel 10 by the driver, the assist component Tq C-A has almost no adverse effect on the operation of the steering wheel 10. In summary, in this steering system, the positive operation component Tq C-M is generated only during automatic steering operation, and the biasing torque Tq C Among the multiple components of the active action component Tq C-M At least a portion of the components other than those mentioned above are configured as non-occurring components during automatic steering and are not generated during automatic steering operation.

[0055] In addition, due to the action of the bidirectional change amount limiter 132 of the first switch 118 and the second switch 120, when switching from normal operation to automatic steering operation, that is, at the start of the automatic steering operation, the positive operation component Tq C-M is gradually increased, and the compensation component Tq C-C Similarly, when switching from automatic steering operation to normal operation, that is, when the automatic steering operation is terminated, the positive action component Tq C-M is gradually decreased, and the compensation component Tq C-C is gradually increased. As a result, the biasing torque TqC This prevents or suppresses abrupt movement of the steering wheel 10 due to a sudden change in the steering angle.

[0056] Furthermore, due to the action of the increase direction change amount limiter 138 of the third switch 124, when switching from normal operation to automatic steering operation, that is, at the start of automatic steering operation, the compensation component Tq C-C Similarly, the steering load dependent component Tq C-L On the other hand, due to the action of the resetter 140 of the third switch 124, when switching from automatic steering operation to normal operation, that is, when the automatic steering operation is terminated, the steering load dependent component Tq C-L The steering load dependent component Tq C-L In short, the steering load dependent component Tq input to the final adder 126 and the preliminary adder 122 with respect to the passage of time t is C-L Change in active action component Tq C-M The total applied torque Tq is the sum of these components. C The change in is shown in the graph of Figure 5. Incidentally, the steering load dependent component Tq C-L is shown as a negative value so that it is easy to understand that it is a component in the opposite direction. Also, the active action component Tq C-M is a value necessary and sufficient for operating the steering wheel 10, and the turning load dependent component Tq C-L Even at the end of the automatic steering operation, a considerable value remains.

[0057] Referring to the graph of FIG. 5, in the automatic steering operation, the steering load dependent component Tq C-L As explained above, the steering load dependent component Tq C-L The change in the active action component Tq C-M The steering load dependent component Tq determined by the steering load dependent component determining unit 110 does not adversely affect the operation of the steering wheel 10.C-L For example, even if the wheels 16 are placed in a neutral position during automatic parking, there is a high possibility that some of the steering load-dependent component Tq will remain due to tire deformation or the like. When switching from automatic steering operation to normal operation, the remaining component may cause unnecessary, i.e., inappropriate, operation of the steering wheel 10. In this steering system, when the automatic steering operation is terminated, the steering load-dependent component Tq C-L To reset to 0, the steering load dependent component Tq C-L The above-mentioned unnecessary operation due to the remaining of the torque Tq does not occur. C The steering load dependent component Tq C-L Since is set to 0, the steering load dependent component Tq C-L Even if you suddenly reset to 0, the reset will not affect the bias torque Tq C It has no effect on [Explanation of symbols]

[0058] 10: Steering wheel (operating member) 12: Reaction force actuator (biasing device) 14: Operation unit 16: Wheel 18: Turning actuator (steering device) 20: Turning unit 22: Steering electronic control unit (steering ECU) (controller) 32: Reaction force motor 40: Motor rotation angle sensor 44: Operation torque sensor 50: Turning rod 58: Turning motor 68: Motor rotation angle sensor 70: Automatic parking controller 72: Vehicle speed sensor 100: Reaction force control unit 102: Turning control unit 104: Assist component determination unit 106: Compensation component determination unit 108: Positive operation component determination unit 110: Turning load-dependent component determination unit 112: Operation angle conversion unit 114: Target operation angle determination unit 116: Adder 118: First switch 120: Second switch 122: Auxiliary adder 124: Third switch 126: Final adder 128: Operation mode determiner 130: Gain switch 132: Bidirectional change amount limiter 134: Multiplier 136: Gain switch 138: Increase direction change amount limiter 140: Resetter 142: Reaction force current control unit 150: Target turning angle determination unit 152: Target turning angle switch 154: Turning torque determination unit 156: Turning current control unit 158: Turning angle conversion unit 160: Current sensor

Claims

1. A steer-by-wire type steering system equipped in a vehicle, the system comprising: an operating member operated by a driver; a biasing device which generates a biasing force to bias the operating member; a steering device which steers wheels; and a controller which controls the biasing device and the steering device, The controller: In a normal operation, the steering of the wheels is realized in response to the operation of the operating member, and the biasing force functions as an operation reaction force against the operation of the operating member. In an automatic steering operation in which the wheels are steered without operation of the operating member, the operation of the operating member in response to the steering of the wheels is realized by the biasing force, and at least a part of the biasing force in the normal operation is not generated, the biasing force includes a plurality of components, one of which is an active operation component for actively operating the operating member in response to steering of the wheels, The controller: The positive action component is generated only during the automatic steering operation, and a non-generated component during automatic steering, which is at least a part of the components other than the positive action component, is not generated during the automatic steering operation, and A steering system configured such that, during the automatic steering operation, at least a portion of the components that do not occur during automatic steering are maintained while a component for offsetting the at least a portion of the components is added to the active operation component, thereby preventing the at least a portion of the components from occurring.

2. The controller:

2. The steering system according to claim 1, wherein a component for offsetting the at least a portion of the component is immediately determined together with the at least a portion of the component at a time point when the automatic steering operation is terminated.

3. A steering system as described in claim 1 or claim 2, wherein at least some of the components include a steering load-dependent component based on the load of the steering device relative to the steering of the wheels, the steering load-dependent component including an actual load-dependent component based on the actual load of the steering device, and the actual load-dependent component is determined based on the current supplied to a steering motor which is the driving source of the steering device.

4. 4. The steering system according to claim 1, wherein the automatic steering operation is an operation of the steering system performed when the vehicle is automatically parked.

5. The controller:

5. The steering system according to claim 1, wherein the positive action component is gradually increased at the start of the automatic steering operation and gradually decreased at the end of the automatic steering operation.

6. The controller:

6. The steering system according to claim 1, wherein the automatic steering non-occurring component is gradually reduced at the start of the automatic steering operation.

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