Steering system

Abstract

This invention provides a highly practical steer-by-wire type steering system. In normal operation, the applied force (Tq) imparted to the operating member (10) is... C ) functions as an operational reaction force (Tq) C‑A 、Tq C‑C 、Tq C‑L In automatic steering operations such as automatic parking, this applied force is used to actuate the corresponding control components (Tq) to rotate the wheels. C‑M ), and make at least a portion (Tq) of the applied force during normal operation. C‑C 、Tq C‑L No action is generated. During automatic steering, the appropriate operating components corresponding to the steering of the wheels are ensured to move.

Description

Technical Field

[0001] This invention relates to a steering system mounted on a vehicle. Background Art

[0002] Recently, the development of a steering system has been underway that does not rely on the driver's operating force applied to the steering wheel or other operating components. Instead, it uses a steering mechanism with a drive source to achieve wheel turning corresponding to the operation of the operating components. This type of steering system is known as a steer-by-wire system. In a steer-by-wire system, a reaction force applying device is provided to apply an operating reaction force, which is a reaction force relative to the operation of the operating components, to the operating components. This device generates an applied force to apply force to the operating components. As for the applied force used to apply the operating reaction force, for example, as described in the following patent document, the application device has been studied to generate an applied force consisting of several components, and the ratio of these components is varied depending on the situation.

[0003] Existing technical documents

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5994868. Summary of the Invention

[0006] In steering systems, such as when automatically parking a vehicle, there are times when the wheels are automatically turned without the operation of the control components; this is known as automatic steering. In steer-by-wire systems, the turned wheels are not mechanically connected to the control components. Therefore, during automatic steering, a force can be applied using the aforementioned force-applying device to achieve the action of the control components corresponding to the wheel's turn. However, this force-applying device is designed to generate the applied force to provide a reaction force. Therefore, it can be predicted that if the applied force consists of several components, the appropriate action of the control components corresponding to the wheel's turn will not occur during automatic steering. In other words, the control components may move unnaturally. Such movement of the control components may reduce the practicality of the steer-by-wire system. The present invention was made in view of this actual situation, and its objective is to provide a steer-by-wire system with high practicality.

[0007] To address the aforementioned problems, the steering system of the present invention is a steer-by-wire type steering system mounted on a vehicle, comprising: an operating member operated by a driver; a force-applying device that generates an applied force to apply force to the operating member; a steering mechanism for turning the wheels; and a controller for controlling the force-applying device and the steering mechanism, wherein the controller is configured to: in normal operation, realize the turning of the wheels corresponding to the operation of the operating member, and make the applied force function as an operational reaction force relative to the operation of the operating member; and in automatic steering operation where the wheels are turned independently of the operating member, realize the operation of the operating member corresponding to the turning of the wheels through the applied force, and prevent at least a portion of the applied force from being generated in the normal operation.

[0008] Invention Effects

[0009] According to the steer-by-wire type steering system of the present invention, during automatic steering operation, at least one component of the applied force generated by the force-applying device, which normally functions as an operating reaction force, is not generated, thus ensuring the operation of the appropriate operating components corresponding to the steering of the wheels.

[0010] [Invention Scheme]

[0011] Regarding the automatic steering operation of the steering system of the present invention, its application is not particularly limited, but the vehicle is suitable for automatic parking where the wheels are automatically turned without relying on the operation of the driver's operating components. Furthermore, it has been studied that the automatic steering operation of the steering system of the present invention is also suitable for transporting vehicles within factories such as vehicle manufacturing plants (hereinafter sometimes referred to as "automatic driving transport") by enabling the vehicle to drive automatically.

[0012] As mentioned above, the applied force can be configured to consist of a variety of components. Under normal operating conditions, for example, the applied force can be configured to include: an auxiliary component for assisting the operation of the control components by the driver; a compensation component for compensating for the driver's operating feel of the control components; and a steering load-based component based on the steering load of the steering device relative to the wheels.

[0013] In addition, the assist component is a component similar to the assist force in so-called power steering. For example, the assist component can be defined as a component in which the greater the operating force applied by the driver to the control components, the greater the assist component.

[0014] The compensation components may include, for example, a return-to-center compensation component, a hysteresis compensation component, a damping compensation component, and an inertia compensation component. The return-to-center compensation component is the component that restores and maintains the operating component in the operating position (hereinafter sometimes referred to as the "neutral position") when the vehicle is traveling straight. The hysteresis compensation component is the component used to simulate the hysteresis characteristics caused by mechanical friction during the operation of the operating component. The damping compensation component is the component used to viscously suppress the micro-vibrations generated in the operating component. The inertia compensation component is the component used to suppress the feeling of sticking at the beginning of the operation of the operating component and the feeling of flow at the end of the operation.

[0015] The steering load basis component can be considered the core component of the operating reaction force, the component of the steering force that the driver feels as the force required to turn the wheels. The steering load basis component can be considered as the component of the axial force acting on the steering column (sometimes called the "rack") connecting the left and right wheels in a so-called standard steering system. This concept includes not only the aforementioned steering force but also, more broadly, the forces acting on the wheels from the road surface. Compared to the auxiliary components described earlier, the steering load basis component acts in roughly the opposite direction. In short, the auxiliary components act in the same direction as the operating direction of the control components, while the steering load basis component acts in the opposite direction.

[0016] The steering load basis component can include several components such as theoretical component, actual load basis component, steering-end-dependent component, and steering hysteresis basis component. Among them, the theoretical component is a theoretical component based on the operation amount of the operating component and the steering amount of the wheel. The actual load basis component is a component that represents the actual load that can be calculated based on the current supplied to the electric motor when the steering device has an electric motor as the drive source. The steering-end-dependent component is a component used to make the driver feel the steering end. The steering hysteresis basis component is a component based on the hysteresis characteristics of the steering device.

[0017] The components described above are those generated during normal operation. However, in autopilot operation, in order to achieve the movement of the operating components corresponding to the wheel's rotation, an active motion component can be generated as the component used to actively move the operating components according to the wheel's rotation. Ideally, this active motion component becomes the main applied force during autopilot operation. In view of this, the aforementioned auxiliary components, compensation components, steering load-based components, etc., constituting the operating reaction force may hinder the proper movement of the operating components during autopilot operation. Therefore, it is ideal to designate at least a portion of these components, in other words, at least a portion of all components other than the active motion component, as "non-generated components during autopilot operation," and to ensure that these non-generated components do not generate during autopilot operation.

[0018] Regarding the active action component, for example, based on the steering wheel rotation amount, the operation amount of the corresponding operating component is determined as the target operation amount, and the deviation of the actual operation amount from the target operation amount is determined according to the feedback control rule.

[0019] When the active motion component only occurs during autopilot operation, it is anticipated that the operating mechanism will abruptly actuate during the switching between the presence and absence of the active motion component. In view of this, it is ideal to gradually increase the active motion component at the beginning of autopilot operation and gradually decrease it during the return to normal operation, that is, at the end of autopilot operation. On the other hand, if the non-active motion component changes abruptly at the beginning of autopilot operation, it is anticipated that the operating mechanism will abruptly actuate due to this abrupt change. Considering this, it is ideal to gradually decrease the non-active motion component at the beginning of autopilot operation.

[0020] As a solution to prevent at least a portion of the non-generating components during autopilot operation from being generated during autopilot operation, for example, it can be configured such that, during autopilot operation, at least a portion of the non-generating components during autopilot operation remain unchanged, and a component used to cancel out this at least a portion of the components (hereinafter, sometimes referred to as the "canceling component") is added to the active action component. To explain a more specific solution, regarding the non-generating components during autopilot operation, for the action of the operating member, that is, for the direction of the operating member's action, it can be distinguished into a same-direction component and an opposite-direction component. The same-direction component is the component acting in the same direction as the active action component, and the opposite-direction component is the component acting in the opposite direction to the active action component. If the opposite-direction component is designed not to be generated during autopilot operation, for example, it can be canceled out by adding a component of the same magnitude as the opposite-direction component to the active action component.

[0021] In the scheme of adding the aforementioned offsetting component, at the end of the automatic steering operation, the offsetting component, along with at least a portion of the offsetting component, is immediately disconnected; in other words, it is drastically reduced. This sufficiently mitigates or prevents inappropriate operation of the operating mechanism at the end of the automatic steering operation caused by the residue of this at least a portion of the component. If the offsetting component is the aforementioned component in the opposite direction, at the end of the automatic steering operation, this opposite-direction component, along with the aforementioned component of the same magnitude, is immediately disconnected; in other words, it is drastically reduced. This sufficiently mitigates or prevents inappropriate operation of the operating mechanism at the end of the automatic steering operation caused by the residue of this opposite-direction component. Since the aforementioned steering load-based component is in the opposite direction, and there is a high probability that it will remain even after the automatic steering operation has ended, the benefit of immediately disconnecting the steering load-based component is significant. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the hardware configuration of the steering system of the present invention.

[0023] Figure 2 This is a functional block diagram illustrating the functional configuration of the controller of the steering system of the present invention.

[0024] Figure 3 This is a block diagram representing the first to third switches included in the functional configuration of the controller.

[0025] Figure 4 It is a table that shows the generation of various components of force applied to the operating components during normal operation and automatic steering operation.

[0026] Figure 5 It is a graph showing the force applied to the operating components and the changes in several components of the applied force during the switching between normal operation and automatic steering operation.

[0027] Explanation of reference numerals in the attached figures:

[0028] 10: Steering wheel [operating component] 12: Reaction force actuator [force application device] 14: Operating part 16: Wheel 18: Steering actuator [steering device] 20: Steering part 22: Steering electronic control unit (steering ECU) [controller] 32: Reaction force motor 40: Motor rotation angle sensor 44: Operating torque sensor 50: Steering stick 58: Steering motor 68: Motor rotation angle sensor 70: Automatic parking controller 72: Vehicle speed sensor 100: Reaction force control unit 102: Steering control unit 104: Auxiliary component determination unit 106: Compensation component determination unit 108: Active action component determination unit 110: Steering load basis component determination unit 112: Operating angle conversion unit; 114: Target operating angle determination unit; 116: Adder; 118: First switcher; 120: Second switcher; 122: Preparatory adder; 124: Third switcher; 126: Final adder; 128: Operating mode determiner; 130: Gain switching switch; 132: Bidirectional variation limiter; 134: Multiplier; 136: Gain switching switch; 138: Increase direction variation limiter; 140: Resetter; 142: Reaction force energizing control unit; 150: Target steering angle determination unit; 152: Target steering angle switching switch; 154: Steering torque determination unit; 156: Steering energizing control unit; 158: Steering angle conversion unit; 160: Current sensor. Detailed Implementation

[0029] Hereinafter, as specific embodiments, a steer-by-wire type steering system, as an embodiment of the present invention, will be described in detail with reference to the accompanying drawings. It should be noted that, in addition to the embodiments described below, the present invention can also be implemented with various modifications and improvements based on the knowledge of those skilled in the art, represented by the solutions described in the section on "Inventive Solutions".

[0030] [Example]

[0031] [A] Hardware configuration of the steering system

[0032] like Figure 1 As schematically shown, the steering system of the embodiment is a steer-by-wire type steering system, generally configured to include: an operation unit 14 having a steering wheel 10 as an operation member operated by the driver and a reaction force actuator 12 for imparting an operation reaction force to the steering wheel 10; a steering unit 20 having a steering actuator 18 as a steering device for turning the wheels 16; and a steering electronic control unit (hereinafter, sometimes simply referred to as "steering ECU") 22 as a controller for controlling the reaction force actuator 12 and the steering actuator 18.

[0033] The operating unit 14 is described below. The steering wheel 10 is fixed to the top end of the steering shaft 30. The reaction force actuator 12 has a reaction force motor 32 as a force source and a reduction mechanism 38 consisting of a worm 34 and a worm wheel 36 mounted on the motor shaft of the reaction force motor 32. The worm wheel 36 is mounted on the steering shaft 30. The reaction force actuator 12 generates an applied torque (a lower-level concept of "applied force") Tq that depends on the motor torque of the reaction force motor 32. C And through the force-applying device that applies force to the steering wheel 10 via the steering shaft 30, the force-applying torque Tq is made C The reaction torque (a sub-concept of "operational reaction force") relative to the operation of the steering wheel 10 is Tq. C The force exerted acts as a reaction force, enabling the device to perform its function. It should be noted that the applied torque Tq... C Primarily functioning as a reaction torque, it is therefore sometimes referred to as the reaction torque Tq in this specification. C .

[0034] The reaction motor 32 is a three-phase brushless motor with a rotational phase for 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 motor rotation angle sensor 40 is used for detection. Furthermore, the steering shaft 30 is configured with upper and lower shafts connected by a torsion bar 42. An operating torque sensor 44 is provided in the operating section 14. This operating torque sensor 44 detects the operating torque (a lower-level concept of "operating force") applied by the driver to the steering wheel 10 by detecting the amount of torsion of the torsion bar 42. O The reaction force motor rotation angle θ detected by motor rotation angle sensor 40. MC The signal and the operating torque Tq detected by the operating torque sensor 44 O The signal is sent to the steering ECU22.

[0035] The steering unit 20 is described below. The steering actuator 18 includes a steering rod 50 extending to the left and right, and a housing 52 that holds the steering rod 50 so that it can move left and right. A threaded groove 54 forming a ball screw mechanism is formed on the steering rod 50. A nut 56, which holds the bearing balls, is screwed into the threaded groove 54 and held in a rotatable but non-rotating manner by the housing 52. A steering motor 58, serving as a drive source, is disposed in the housing 52. A timing belt 62 is wound around the outer periphery of a pulley 60 mounted on the motor shaft of the steering motor 58 and the nut 56, which functions as another pulley. Due to the rotation of the motor shaft of the steering motor 58, i.e., due to the rotation of the steering motor 58, the nut 56 rotates, and the steering rod 50 moves left and right. The left and right ends of the steering rod 50 are respectively connected to steering knuckle arms, which hold the left and right wheels 16 rotatable, via connecting rods (not shown). As the rudder stick 50 moves left and right, the left and right wheels 16 are turned, that is, the left and right wheels 16 are turned.

[0036] A rack 64 is formed in the rudder stick 50, and a pinion shaft 66 is held rotatably by the housing 52 in engagement with the rack 64. The rack 64 and pinion shaft 66 do not need to be specifically provided in the rudder actuator 18 constituting the steer-by-wire type of this steering system. For ease of understanding, if the pinion shaft 66 is connected to the steering shaft 30 of the operating unit 14, a general power steering system is realized. That is, this steering system is constructed by making slight structural modifications to a general power steering system. It should be noted that the rudder stick 50, because it has a rack 64, can also be called a rack and pinion.

[0037] The steering motor 58 is a three-phase brushless motor with a rotational phase for 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. MS The motor rotation angle sensor 68 is used for detection. The steering motor rotation angle θ detected by the motor rotation angle sensor 68. MS The signal is sent to the steering ECU22.

[0038] The steering ECU 22 is configured to include a computer consisting of a CPU (Central Processing Unit), ROM (Read-Only Memory), and RAM (Random Access Memory), a converter for the drive circuit of the reaction force motor 32, and a converter for the drive circuit of the steering wheel motor 58. As will be explained in detail later, this steering system performs automatic steering operation when the vehicle is automatically parked, automatically turning the wheels 16 without relying on the driver's steering wheel 10. To perform this automatic steering operation, the steering ECU 22 is connected to the automatic parking controller 70. Furthermore, the steering ECU 22 obtains a signal related to the vehicle speed v from the vehicle speed sensor 72, which detects the vehicle's travel speed (hereinafter sometimes simply referred to as "vehicle speed").

[0039] [B] Controller Functions

[0040] The steering ECU22, which serves as the controller of this steering system, has Figure 2 The functional configuration is shown in the functional block diagram. This functional configuration is implemented by a computer executing a prescribed program, but it can also be implemented by a dedicated circuit such as an ASIC (Application Specific Integrated Circuit). The steering ECU 22 can be broadly divided into a reaction force control unit 100 and a steering control unit 102. The signals input to or output from the various components shown in the diagram are mostly signals representing values ​​of torque, torque components, steering angle, operating angle, etc. However, to avoid making the explanation lengthy, in the following description, it will be shown that only torque, torque components, steering angle, operating angle, etc. are input to or output from the various components.

[0041] (a) Reaction force control unit

[0042] The reaction force control unit 100 controls the applied torque Tq generated by the reaction force actuator 12, which serves as a force application device. C (reaction torque Tq) C The control unit has the function of determining the applied torque Tq respectively. C The auxiliary component Tq of the component C-A Compensation component Tq C-C , active action component Tq C-M Steering load based on component Tq C-L The auxiliary component determination unit 104, the compensation component determination unit 106, the active action component determination unit 108, and the steering load basis component determination unit 110.

[0043] In the control of this steering system, the operating angle θ is used as the operating amount of the steering wheel 10. O Therefore, the reaction force control unit 100 has an operating angle conversion unit 112, which converts the reaction force motor rotation angle θ detected by the motor rotation angle sensor 40 of the reaction force motor 32 into an operating angle conversion unit. MC Converted to operating angle θ O Operating angle θ O and the rotation angle θ of the reaction force motor MC The cumulative amount satisfies the relationship with the reduction ratio of the reduction mechanism 38, and therefore the conversion is performed based on this reduction ratio. Although detailed descriptions are omitted, this steering system has an operating angle θ for the steering wheel 10 from the neutral position (the position when the vehicle is traveling straight). O The sensor used for detection (not shown) performs the operation angle calculation (θ) based on the sensor's detection value, and executes the calculation at a predetermined time interval using the operation angle conversion unit 112. O Calibration.

[0044] Furthermore, the reaction force control unit 100 has a target operating angle determination unit 114 for automatic steering operation, which determines the steering angle θ, which is the steering amount of the wheel 16. S and operating angle θ O The steering angle θ at the current time point under a specific steering gear ratio γ0. S The corresponding operating angle θ O Determine the target operating angle θ O * .

[0045] The applied torque Tq is applied sequentially as described above. C The determination of each component is explained, and the auxiliary component Tq is also explained. C-A It is a component similar to the auxiliary force in so-called power steering, and the auxiliary component determination unit 104 is based on the operating torque Tq detected by the operating torque sensor 44. O The vehicle speed v determines the auxiliary component Tq. C-A In short, the auxiliary component Tq C-A The operating torque Tq is determined. O The larger the auxiliary component Tq is, the better. C-A The larger the value, and at higher vehicle speeds v, the greater the driver's sense of steering input (hereinafter sometimes referred to as "steering input" or simply "input"), the greater the auxiliary component Tq. C-A The assist component Tq is set to a small value at low vehicle speeds (v) to reduce the feeling of instability during maneuvering. C-A It is determined to be a large value, thus becoming an auxiliary component Tq. C-AThe orientation is the same as the steering operation direction, which is the direction of operation of the steering wheel 10, and is the same component of the orientation.

[0046] Compensation component Tq C-C The compensation component includes a return-to-center compensation component for restoring and maintaining the steering wheel 10 in a neutral position, a hysteresis compensation component for mimicking the hysteresis characteristics caused by mechanical friction during the operation of the steering wheel 10, a damping compensation component for viscously suppressing micro-vibrations generated in the steering wheel 10, and an inertia compensation component for suppressing the sticking sensation at the start of the operation of the steering wheel 10 and the flowing sensation at the end of the operation. The compensation component determination unit 106 determines these components and adds the determined components to determine the compensation component Tq. C-C .

[0047] Specifically, the homing compensation component is based on the operating torque Tq. O Vehicle speed v, operating angle θ O Regarding the operating angle θ O The operating speed θ obtained by differentiation O To determine, specifically, the alignment compensation component is determined by the operating angle θ. O The further a value is from the neutral position, the larger the hysteresis compensation component becomes. O The damping compensation component is determined based on the vehicle speed v and the operating angle θ, in a way that optimizes the aforementioned hysteresis characteristics. O The operating speed θ obtained by differentiation O ', to be specific, is determined by the operating speed θ O The higher the value, the larger the damping compensation component. The inertia compensation component is based on the vehicle speed v, and further adjusted for the operating speed θ. O The operational acceleration θ obtained by differentiation O To be more specific, it is determined to be the operating acceleration θ. O "The higher the value, the larger the inertial compensation component. The compensation component Tq is obtained by adding these components together." C-C The orientation can be either the same as or opposite to the steering direction.

[0048] Steering load based on component Tq C-L This can be considered the core component of the reaction torque; roughly speaking, it is the component of the steering force that the driver feels as the force required to turn the wheel 16. The steering load is based on component Tq. C-L Alternatively, it can be considered as the component of the force (axial force) acting on the rudder stick 50 of the rudder actuator 18 along its axis, with the rudder load based on the component Tq. C-L In addition to the aforementioned steering force, this is also used to allow the driver to widely feel the components of the force acting on the wheels 16 from the road surface. The steering load is based on the component Tq.C-L It is the component that is roughly opposite to the direction of steering operation.

[0049] In detail, the steering load is based on the component Tq C-L This includes the operating angle θ based on the steering wheel 10. O , the steering angle θ of the wheel S The steering load basis component determination unit 110 determines the theoretical component of the steering load, the actual load basis component based on the actual load of the steering actuator 18, the steering end basis component for making the driver feel the steering end of the wheel 16, and the steering hysteresis basis component based on the hysteresis characteristics of the mechanical friction of the steering actuator 18. The determined components are summed to determine the steering load basis component Tq. C-L .

[0050] Specifically, the theoretical component is the component that does not consider the friction between the road surface and the wheel 16, and is based on the steering angle θ that the wheel 16 should be turned by. S Target steering angle θ S * In short, considering the self-aligning torque of wheel 16, it is determined as the target steering angle θ. S * The larger the value and the higher the vehicle speed v, the larger the theoretical component. It can be considered that the load on the steering actuator 18 is related to the steering current I supplied to the steering motor 58. S Proportional, therefore the actual load is based on the component of the steering current I. S And determined as the steering current I S The larger the value, the greater the actual load based on the component. The steering end is based on the target steering angle θ based on the component. S * The rudder angle θ of the target was determined. S * Ascend rapidly towards the end of the steering input. Steering hysteresis is based on a component derived from the operating angle θ. O The vehicle speed v is determined in a way that optimizes the hysteresis characteristics.

[0051] Active action component Tq C-M This is the component used to actively move the steering wheel 10. In this steering system, it corresponds to the automatic steering operation during automatic parking. The active movement component determination unit 108 is based on the operating angle deviation Δθ. O The positive action component Tq is determined according to the feedback control rule. C-M The operating angle deviation Δθ O The operating angle θ at the current time point O The target operating angle θ determined by the target operating angle determination unit 114 described above.O * The deviation. Specifically, the active action component Tq C-M The value is determined by proportional control, specifically by the deviation of the operating angle Δθ. O The size of the component corresponding to the size of the action component. That is, the active action component Tq C-M Determined as operating angle deviation Δθ O The larger the value, the greater the active action component Tq. C-M The larger the value. It should be noted that the active action component Tq... C-M It is the component in the same direction as the direction that causes the steering wheel 10 to move, and is approximately relative to the auxiliary component Tq. C-A The same directional component and the component Tq relative to the rudder load C-L The component in the opposite direction.

[0052] The auxiliary component Tq determined by the auxiliary component determination unit 104 C-A The compensation component Tq is input to adder 116 and determined by compensation component determination unit 106. C-C The input is sent to the adder 116 via the first switch 118. The active motion component Tq is determined by the active motion component determination unit 108. C-M The steering load basis component Tq, determined by the steering load basis component determination unit 110, is input to the pre-adder via the second switch 120. C-L The input is sent to the pre-adder 122 via the third switch 124. In the pre-adder 122, the input active motion component Tq is... C-M And the steering load based on component Tq C-L The components are added together, and the resulting component is input to adder 116. In adder 116, the input auxiliary component Tq is... C-A Compensation component Tq C-C And the positive action component Tq C-M And the steering load based on component Tq C-L The summed components are then aggregated, and this aggregated component is input to the final adder 126. The steering load basis component Tq, determined by the steering load basis component determination unit 110, is... C-L The input is also sent to the final adder 126 via the third switch 124. In the final adder 126, the steering load component Tq input from the third switch 124 is subtracted from the component input from the adder 116. C-L The result is that the applied torque Tq C The decision is made. In short, the first switcher 118, the second switcher 120, and the third switcher 124 are functional units used to switch the generation of the present or absent component during the switching between normal operation and automatic steering operation.

[0053] The first switcher 118 has Figure 3 The functional configuration is as shown in (a). Specifically, the first switch 118 is configured to include an operating mode determiner 128, a gain switching switch 130, a bidirectional change limiter 132, and a multiplier 134. The automatic parking controller 70 inputs the flag value of the automatic steering flag ASF and the operating torque Tq detected by the operating torque sensor 44 to the operating mode determiner 128. O Regarding the automatic steering flag ASF, the flag value is set to "1" (hereinafter, sometimes referred to as "ASF='1'") when automatic steering is indicated, and set to "0" (hereinafter, sometimes referred to as "ASF='0'") when automatic steering is not indicated. The operating mode determiner 128 is set to ASF="1" and the operating torque Tq is... O Less than the threshold operating torque Tq O-TH If the steering wheel 10 is not operated by the driver, the steering system is determined to be in automatic steering mode. If at least one of these two conditions is not met, the steering system is determined to be in normal operation.

[0054] The gain switching switch 130 outputs 0 when the automatic steering is in operation, and outputs 1 when the operating mode determiner 128 is in operation. The bidirectional change limiter 132 prevents abrupt changes in the gain G during switching from 1 to 0 and from 0 to 1. Specifically, if the value of gain G changes by more than a predetermined value after a specified time interval has elapsed compared to its value before the interval, the change in gain G is set to the predetermined value. The gain G after passing through the bidirectional change limiter 132 is input to the multiplier 134. The compensation component Tq determined by the compensation component determination unit 106 is also input to the multiplier 134. C-C In this multiplier 134, the gain G is multiplied by the compensation component Tq. C-C Multiply, and output the compensated component Tq after multiplication from the first switch 118. C-C .

[0055] The second switch 120 has Figure 3 The second switch 120 is configured to include the same operating mode determiner 128, bidirectional change limiter 132, and multiplier 134 as the first switch 118. The second switch 120 also has a gain switching switch 136, but this gain switching switch 136 differs from the gain switching switch 130 of the first switch 118; it outputs 1 when the automatic steering is in operation and 0 when in normal operation. The active motion component Tq is determined by the active motion component determination unit 108.C-M After processing by the second switch 120, the output is from the second switch 120.

[0056] The third switch 124 has Figure 3 The function is configured as shown in (c). Specifically, the third switch 124 is configured to include the same operating mode determiner 128, multiplier 134, and gain switching switch 136 as the second switch 120, as the first switch 118. The third switch 124 also has a change limiter, but the increase direction change limiter 138 of the third switch 124 is set to prevent abrupt changes in the value of the gain G during switching from 0 to 1, while allowing abrupt changes in the value of the gain G during switching from 1 to 0.

[0057] The third switch 124 also has a resetter 140. The resetter 140 is input with the steering load basis component Tq determined by the steering load basis component determination unit 110. C-L And the flag value of the automatic steering flag ASF. When the reset device 140 is set to ASF = "0", that is, when automatic steering is not indicated, the steering load is adjusted according to the component Tq. C-L Temporarily reset to 0, and at the start of subsequent normal operation, set the rudder load according to component Tq. C-L It gradually increases from 0. The steering load, which has been processed by the resetter 140, is based on the component Tq. C-L In addition to being output from resetter 140 to multiplier 134, it is also directly output from resetter 140 to final adder 126.

[0058] The applied torque Tq output from the final adder 126 C The input is sent to the reaction force energizing control unit 142. The reaction force energizing control unit 142 is configured to include a converter that serves as a drive circuit (driver) for the reaction force motor 32. The reaction force energizing control unit 142 is based on the input applied force torque Tq. C To determine the reaction current I that should be supplied to the reaction motor 32. C And from the converter, the reaction force current I C Supply to reaction motor 32.

[0059] (b) Steering control unit

[0060] Steering control unit 102 controls the steering angle θ of the wheel 16 that is steered by steering actuator 18, which is a steering device. S The control function includes a target steering angle determination unit 150, a target steering angle switching switch 152, a steering torque determination unit 154, and a steering power control unit 156.

[0061] In the control of this steering system, the steering angle θ is used as the steering amount of wheel 16. S Therefore, the steering control unit 102 has a steering angle conversion unit 158, which converts the steering motor rotation angle θ detected by the motor rotation angle sensor 68 of the steering motor 58 into a steering motor rotation angle. MS Converted to rudder angle θ S Incidentally, the rudder angle θ S The toe angle of wheel 16 can also be used, but the rotation angle of the aforementioned pinion shaft 66 is used in the control of this steering system. Steering angle θ S and the rotation angle θ of the steering motor MS The cumulative amount is related to a predetermined reduction ratio. Specifically, it is related to the reduction ratio determined by the reducer included in the steering motor 58, the lead angle of the ball screw mechanism of the steering actuator 18, and the diameter of the pinion shaft 66. Therefore, the conversion is performed based on this reduction ratio. Although detailed description is omitted, this steering system has a sensor (not shown) for detecting the rotation angle of the wheel 16 from the rotational position of the pinion shaft 66 when the wheel 16 is in a straight-line state. Based on the detection value of this sensor, the steering angle θ calculated by the steering angle conversion unit 158 ​​is executed at a predetermined time. S Calibration.

[0062] The target steering angle determination unit 150 is based on the operating angle θ calculated by the operating angle conversion unit 112 of the reaction force control unit 100. O To determine the rudder angle θ S The target steering angle θ of the control target S * This steering system can change the steering gear ratio γ, i.e., the steering angle θ, according to the vehicle speed v. S With operating angle θ O The system, with a target steering angle determination unit of 150 based on the operating angle θ, is a ratio system. O The target steering angle θ is determined by referring to the stored mapping data, along with the vehicle speed v. S * Incidentally, the method for changing the steering gear ratio γ is a general one, and its explanation here is omitted.

[0063] The target steering angle θ is determined by the target steering angle determining unit 150. S * This is used in normal operations, but in the automatic steering operation described above, the target steering angle θ is... S * In contrast, the target steering angle θ is based on the signal sent from the automatic parking controller 70. S *The target steering angle switching switch 152 is used to select the target steering angle θ. S * The target steering angle switching switch 152, although detailed description omitted, has the same operating mode determiner 128 as the first switch 118 of the reaction force control unit 100, and selects the target steering angle θ according to the determination made by this determiner. S * Switch to another device.

[0064] The steering torque determination unit 154 determines the steering torque Tq required to turn the wheel 16. S Functional section. Steering torque Tq S For example, it can be considered as the torque that the steering motor 58 should produce. Specifically, it is based on the actual steering angle θ at the current time point calculated by the steering angle conversion unit 158. S and target steering angle θ S * To determine the rudder angle θ S relative to the target steering angle θ S * The deviation of the rudder angle Δθ S And according to the rudder angle deviation Δθ S The PID (Proportional-Integral-Derivative) feedback control rule is used to determine the steering torque Tq. S The method according to this feedback control rule is a general approach, and its explanation is omitted here.

[0065] The rudder energizing control unit 156 is configured to include a converter that serves as a drive circuit (driver) for the rudder motor 58. The rudder energizing control unit 156 is based on the determined rudder torque Tq. S To determine the steering current I that should be supplied to the steering motor 58. S and the steering current I S The power supply is from the converter to the steering motor 58. It should be noted that the steering ECU 22 has a function for controlling the supplied steering current I. S The current sensor 160 performs the detection, and the steering current I detected by the current sensor 160 is... S The rudder load used in the above-mentioned component Tq C-L The decision.

[0066] [C] Applying force and switching between normal operation and autopilot operation.

[0067] In detail, the steering ECU22, which has the functions described above, controls the applied torque Tq through its reaction force control unit 100. C As explained above, this steering system switches between operating modes during normal operation and automatic steering in automatic parking, and with this switching, the applied torque Tq... C It was also switched.

[0068] To explain in detail, the functions of the first switch 118, the second switch 120, the third switch 124, the pre-adder 122, the adder 116, and the final adder 126, as described above, are roughly as follows: Figure 4 The table shows the effect of the applied torque Tq during normal operation and automatic steering. C Auxiliary components Tq of each component C-A Compensation component Tq C-C , active action component Tq C-M Steering load based on component Tq C-L The generation of [something] is switched. Specifically, the auxiliary component Tq is [made to switch]. C-A It is generated in both normal operation and automatic steering operation, but the compensation component Tq is affected. C-C Steering load based on component Tq C-L It is generated during normal operation, but not during automatic steering; conversely, it causes the active motion component Tq to be generated. C-M It is not generated during normal operation, but is generated during automatic steering.

[0069] It should be noted that the steering load is based on component Tq C-L It is at least a portion of the non-generating component during automatic steering, and is relative to the active action component Tq. C-M The component in the opposite direction. This rudder load is based on component Tq. C-L The steering load is not simply not generated during automatic steering operation, but is input to the final adder 126 according to the component Tq during normal operation. C-L via pre-adder 122 and active motion component Tq C-M Together they are added to adder 116, thereby adjusting the rudder load according to component Tq. C-L The load is canceled out, resulting in no longer generating steering load based on component Tq. C-L .

[0070] from Figure 4 As can be seen from the table, in normal operation, based on the auxiliary component Tq C-A Compensation component Tq C-C Steering load based on component Tq C-L Torque Tq CThe reaction torque Tq relative to the driver's operation of the steering wheel 10 C To function appropriately. In contrast, during automatic steering operation, based on the active motion component Tq... C-M The applied torque Tq C So as to become the steering angle θ of wheel 16 S The corresponding operating angle θ O This allows the steering wheel 10 to move appropriately. Furthermore, it allows the compensation component Tq to... C-C Steering load based on component Tq C-L This does not produce [a certain effect], thus not hindering the proper operation of the steering wheel 10. Conversely, it prevents [the occurrence of] compensation component Tq. C-C Steering load based on component Tq C-L This causes inappropriate movements of the steering wheel 10. It should be noted that during automatic steering operation, although an auxiliary component Tq remains... C-A But the auxiliary component Tq C-A Based on the operating torque Tq applied by the driver to the steering wheel 10 O In automatic steering without driver input of the steering wheel 10, the auxiliary component Tq... C-A Movement of the steering wheel 10 will have almost no adverse effect. In summary, this steering system is configured to make the active action component Tq... C-M This torque Tq is generated only during automatic steering. C In addition to the active action component Tq, the other components are also included in the total number of components. C-M At least a portion of the components other than those are designated as non-generated components during automatic steering, and such non-generated components are not generated during automatic steering.

[0071] Furthermore, when switching from normal operation to automatic steering operation via the bidirectional change limiter 132 of the first switcher 118 and the second switcher 120, that is, at the start of automatic steering operation, the active motion component Tq is... C-M Gradually increase, and make the compensation component Tq C-C Gradually reduce. Similarly, when switching from automatic steering to normal operation, i.e., at the end of automatic steering, reduce the active motion component Tq. C-M Gradually reduce, and make the compensation component Tq C-C Gradually increasing. Thus, during these switching processes, the applied torque Tq is prevented or suppressed. C The sudden change in the steering wheel 10 caused by the sudden movement of the steering wheel.

[0072] Furthermore, when switching from normal operation to automatic steering operation via the action of the third switch 124's increased direction change limiter 138, that is, at the start of automatic steering operation, the active motion component Tq... C-M Similarly, the rudder load input to the pre-adder 122 for the purpose of the above-mentioned cancellation is based on the component Tq. C-L Gradually increasing. Conversely, when switching from automatic steering operation to normal operation via the reset unit 140 of the third switcher 124, i.e., at the end of automatic steering operation, the steering load input to the pre-adder 122 to offset the load is based on the component Tq. C-L The steering load input to the final adder 126 is based on the component Tq. C-L All are immediately disconnected, i.e., reset to 0. Specifically, the steering loads, relative to the elapsed time t, are input to the final adder 126 and the pre-adder 122 according to the component Tq. C-L Changes, positive action components Tq C-M The change, the total applied torque Tq obtained by summing these components C Changes such as Figure 5 The curve is like that. Incidentally, the rudder load input to the final adder 126 is based on the component Tq. C-L For ease of understanding, the components representing opposite directions are represented by negative values. Furthermore, the active motion component Tq during automatic steering operation... C-M The steering load basis component Tq is set to a value that is necessary and sufficient for the steering wheel 10 to move, and is determined by the steering load basis component determination unit 110. C-L A considerable value remains even at the end of the automatic steering operation.

[0073] Reference Figure 5 The graph illustrates this; during automatic steering operation, the steering load is based on the component Tq. C-L As explained above, this is offset, and the rudder load is determined according to component Tq. C-L Changes in Tq based on active action components C-M The movement of the steering wheel 10 will not cause any adverse effects. For example, even when the wheel 16 is in a neutral position during automatic parking, the steering load determination component Tq determined by the steering load determination unit 110 will not cause any adverse effects. C-L There is a high possibility of some residual material due to tire deformation, etc. Because of this residual component, when switching from automatic steering to normal operation, unwanted, or rather, inappropriate, movements may occur on the steering wheel 10. In this steering system, at the end of automatic steering operation, the steering load is adjusted according to the component Tq. C-L Reset to 0, therefore no load will be generated due to the steering load based on component Tq. C-LThe aforementioned unwanted actions are caused by residual torque. It should be noted that during automatic steering operation, the applied torque Tq is neutralized through the above-mentioned cancellation. C The steering load in the middle is based on the component Tq C-L Therefore, even at the end of the automatic steering operation, the steering load is set according to the component Tq. C-L Immediately reset to 0, this reset will not affect the applied torque Tq. C This has an impact.

Claims

1. A steering system, a steer-by-wire type steering system mounted on a vehicle, the steering system comprising: an operating member operated by a driver; a force application device that generates and applies a force to the operating member; a steering mechanism for turning the wheels; and a controller for controlling the force application device and the steering mechanism. in, The controller is configured to: In normal operation, the wheel turns in accordance with the operation of the operating member, and the applied force functions as an operating reaction force relative to the operation of the operating member. as well as In automatic steering operation where the wheels are turned tactilely without relying on the operating member, the applied force is used to actuate the operating member corresponding to the wheel's turning, and at least a portion of the applied force that would occur during normal operation is not generated. At least a portion of the applied force includes a steering load-based component, which is based on the axial force acting on the steering rod or rack, including the force acting on the wheel from the road surface, and the steering load-based component acts in the opposite direction to the operating direction of the operating member.

2. The steering system according to claim 1, wherein, The automatic steering operation refers to the operation of the steering system during automatic parking of the vehicle.

3. The steering system according to claim 1, wherein, The applied force comprises multiple components, one of which is an active action component for actively actuating the operating member in response to the turning of the wheel. The controller is configured to cause the active action component to be generated only during the automatic steering operation, and to prevent the automatic steering non-generating component, which is at least a part of the components other than the active action component, from being generated during the automatic steering operation.

4. The steering system according to claim 3, wherein, The plurality of components includes: an auxiliary component for assisting the operation of the control components performed by the driver; a compensation component for compensating the driver for the operational feel of the control components; and a steering load-based component based on the steering load of the steering device relative to the wheels.

5. The steering system according to claim 3 or 4, wherein, The controller is configured to gradually increase the active motion component at the start of the automatic steering operation and gradually decrease it at the end of the automatic steering operation.

6. The steering system according to claim 3 or 4, wherein, The controller is configured to gradually reduce the non-generating component during automatic steering at the start of automatic steering operation.

7. The steering system according to claim 3 or 4, wherein, The controller is configured to: maintain at least a portion of the non-generating components during the automatic steering operation, and add a component to counteract the at least a portion of the components to the active steering components.

8. The steering system according to claim 7, wherein, The controller is configured to immediately disconnect the component used to counteract the at least part of the component at the end time of the automatic steering operation.

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