JP2004168150A - Electronic steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit and prevent the variation of steering reaction torque caused by disturbance such as kick-back. <P>SOLUTION: A characteristic line m1 indicating the correspondence of tire steering shaft torque Tt and basic steering reaction torque Tδ in a case free from the disturbance, and a characteristic line m2 wherein the variation of the basic steering reaction torque Tδ to the variation of the tire steering shaft torque Tt is smaller than that in the characteristic line m1, and the larger a steering angle is, the larger the basic steering reaction torque Tδ is, are determined. The basic steering reaction torque Tδ is determined on the basis of the characteristic line m1, when the disturbance is not found and the tire steering shaft torque Tt is less than the intersection of the characteristic lines m1 and m2, to generate the steering reaction torque corresponding to the tire steering shaft torque Tt, and is determined on the basis of the characteristic line m2, when the tire steering shaft torque Tt is larger than the intersection of the characteristic lines m1, m2 by the disturbance, to reduce the variation of the basic steering reaction torque Tδ to the tire steering shaft torque Tt, whereby the variation of the steering reaction torque in accompany with the variation of the tire steering shaft torque Tt caused by the disturbance is inhibited. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an electric motor in which a steering torque is generated by an actuator in accordance with an operation amount of a steering wheel to perform steering, and a steering reaction torque is generated in the steering wheel by the actuator in accordance with the steering torque. The present invention relates to a steering system.
[0002]
[Prior art]
Conventionally, a steering wheel steered by a driver and a steering mechanism of a steered wheel are mechanically separated, a steering angle of the steering wheel is detected by a detector such as an encoder, and an actuator is operated by an actuator according to the detected steering angle. 2. Description of the Related Art A steer-by-wire steering device is known as a steering device that generates torque to steer steered wheels.
[0003]
In this type of steering apparatus, a steering torque corresponding to a steering angle is generated, and a steering reaction torque corresponding to the steering torque is applied to the steering wheel by an actuator, so that the steering wheel and the steered wheels are mechanically connected to each other. This provides the driver with an operating environment equivalent to that when the vehicle is connected to the vehicle.
By the way, when the steering torque is detected and torque control is performed based on the steering torque, a method described in Japanese Patent Application Laid-Open No. 7-228263 may be used to perform torque correction in consideration of disturbance such as kickback. An electric power steering device described in Japanese Patent Application Laid-Open No. 2000-159135 has been proposed.
[0004]
Among them, the electric power steering apparatus described in Japanese Patent Application Laid-Open No. 7-228263 detects a torque generated on a steering shaft as a steering torque, and applies an assist torque according to the steering torque. When the change in the steering angle is small and the change in the steering torque is large, it is determined that kickback from the road surface has occurred, and the assist torque is corrected in consideration of the influence of the kickback. Further, the electric power steering apparatus described in Japanese Patent Application Laid-Open No. 2000-159135 calculates a target neutral position from steering angle information within a predetermined time in the past, adds an auxiliary steering torque, and calculates a target neutral position from the steering angle information at the neutral position. The target neutral position is calculated, an auxiliary steering torque is added, and the steering reaction force at the neutral position is biased to reduce the steering reaction torque due to a load change due to a road surface cant or the like.
[0005]
[Patent Document 1]
JP-A-7-228263
[Patent Document 2]
JP 2000-159135 A
[0006]
[Problems to be solved by the invention]
However, among the conventional electric power steering devices described in Japanese Patent Application Laid-Open No. 7-228263, kicking from a road surface when the steering angle change per unit time is small and the steering torque change amount is large. Since the configuration is such that it is determined that the back has occurred and the assist torque is corrected based on that, the steering torque change at least up to the kick back determination cannot be prevented or suppressed. Further, during steering, since the steering angle change per unit time is not small, even if kickback occurs, it cannot be detected and the assist torque cannot be corrected. In the case of a steady input such as a road cant, the assist torque cannot be corrected because the amount of change in the steering torque is not large. Further, in the electric power steering apparatus described in Japanese Patent Application Laid-Open No. 2000-159135, the steering reaction torque due to a load change due to a road surface cant or the like can be reduced. Can't improve.
[0007]
Therefore, in the steer-by-wire type steering device, the steering torque generated in the steering mechanism is detected, and the actuator for generating the steering reaction force is driven based on the detected torque to generate the steering reaction force on the steering wheel. At this time, when a process for disturbance such as kickback described in Patent Document 1 or 2 is performed, in this case as well, the suppression of the change in the steering reaction torque until the kickback determination is performed. In addition, there is a problem that it is not possible to improve the handling of the steering wheel due to a short-time disturbance or kickback.
[0008]
Therefore, the present invention has been made in view of the above-mentioned conventional unsolved problem, and an electric steering device capable of appropriately suppressing and preventing fluctuation of steering reaction torque due to disturbance such as kickback. It is intended to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an electric steering device according to the present invention controls the driving of a steering mechanism mechanically separated from the steering mechanism according to the steering amount of the steering mechanism, and controls the turning of the steering mechanism. A reaction torque corresponding to the rudder shaft torque is applied to the steering mechanism. At this time, the characteristic of the reaction torque against the turning shaft torque is changed according to the steering angle.
[0010]
【The invention's effect】
According to the electric steering apparatus of the present invention, the reaction torque corresponding to the turning shaft torque is applied to the steering mechanism, but the characteristic of the reaction torque with respect to the turning shaft torque is changed according to the steering angle. Therefore, for example, even when the turning shaft torque fluctuates due to disturbance or the like, the reaction force torque fluctuates according to the steering angle at this time. Therefore, for example, if the characteristic is set such that the reaction torque fluctuation with respect to the turning shaft torque fluctuation at a constant steering angle is smaller than the reaction torque fluctuation with respect to the turning shaft torque fluctuation accompanying the change in the steering angle, Reaction torque fluctuations can be reduced when steering shaft torque fluctuations occur due to disturbance or the like.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an example of an electric steering device according to the present invention.
In the figure, reference numeral 1 denotes a steering wheel steered by a driver, and a steering shaft 2 is connected to a rotation center of the steering wheel 1. The steering shaft 2 is provided with a steering angle sensor 3, a steering torque sensor 4, and a reaction force generating motor 5.
[0012]
The steering angle sensor 3 is composed of, for example, an encoder or the like, detects a rotation angle of the steering shaft 2, that is, a steering angle δ, and outputs this to the control unit 10. Further, the steering torque sensor 4 is configured by, for example, a known torque sensor, and detects a steering torque Ts generated in the steering shaft 2 and outputs the detected steering torque Ts to the control unit 10. The reaction force generating motor 5 is driven and controlled by the control unit 10 and generates a steering reaction force in a direction opposite to the steering force applied to the steering wheel 1 by the driver.
[0013]
In FIG. 1, reference numeral 11 denotes a rack shaft, and reference numeral 12 denotes a pinion gear that meshes with a rack gear of the rack shaft 11, and the rack shaft 11 and the pinion gear 12 constitute a rack and pinion mechanism. The pinion gear 12 is provided with a pinion shaft 13. The pinion shaft 13 is provided with a first steering motor 14, and the rotational motion of the first steering motor 14 is transmitted to the pinion gear 12 via the pinion shaft 13 and converted into a reciprocating motion of the rack shaft 11. It has become so. The rack shaft 11 is provided with a second steering motor 15, and the rack shaft 11 is reciprocated by driving the first steering motor 14 and the second steering motor 15. . The reciprocating linear motion of the rack shaft 11 is converted into a steering motion of the steered wheels 20 by the tie rods 16 and a knuckle arm (not shown), whereby the steered wheels 20 are steered. The drive of the first and second steering motors 14 and 15 is controlled by the control unit 10. Further, the reaction force generating motor 5, the first turning motor 14, and the second turning motor 15 are driven and controlled by, for example, duty ratio control, so that forward / reverse control is performed in any direction.
[0014]
The tie rod 16 is provided with an axial force sensor 21 for detecting a turning shaft torque Tt and a displacement sensor 22 such as a potentiometer for detecting the amount of movement of the rack shaft 11.
The vehicle is equipped with a vehicle speed sensor 23 that detects the vehicle speed of the host vehicle, and detection signals from these various sensors are supplied to the control unit 10.
[0015]
The control unit 10 drives the first and second steering motors 14 and 15 to steer the steered wheels 20, and drives the reaction force generation motor 5 to generate a steering reaction force. And a reaction force generation process.
FIG. 2 is a control block diagram illustrating a configuration of the control unit 10.
In the figure, reference numeral 31 denotes a reaction force generation processing unit that performs the reaction force generation processing, and reference numeral 32 denotes a turning control processing unit that performs the turning control processing.
[0016]
In the reaction force generation processing section 31, the counter determination section 31a determines whether or not the vehicle is in a counter steer state based on the steering angle δ detected by the steering angle sensor 3, and determines the result of the determination by the counter determination section 31a and the vehicle speed. Based on the vehicle speed V detected by the sensor 23, the tire turning shaft torque Tt detected by the axial force sensor 21, and the steering angle δ detected by the steering angle sensor 4, a target steering reaction force calculating unit 31 b calculates a target steering reaction force. Torque Tδ ^* Is calculated. Then, in the calculation unit 31c, the steering torque Ts detected by the steering torque sensor 4 and the target steering reaction force torque Tδ ^* , The steering torque Ts and the target steering reaction torque Tδ. ^* Is generated, and the motor driver 31d controls the drive of the reaction force generating motor 5 based on the drive control signal, thereby obtaining the target steering reaction torque Tδ. ^* Generate.
[0017]
In the turning control processing section 32, the target turning angle δt of the turning wheels 20 is determined in a known procedure based on the steering angle δ detected by the steering angle sensor 3 in the target tire turning angle calculation section 32a. ^* Is calculated. Then, in the calculation unit 32b, the target turning angle δt ^* A target steering torque to be applied to the tie rod 16 is calculated based on the displacement Xs detected by the displacement sensor 22 to generate drive control signals for the first and second steering motors. , The motor driver 32c drives the first and second steering motors 14 and 15 to cause the displacement Xs of the displacement sensor 22 to follow the steering angle δ of the steering wheel 1.
[0018]
FIG. 3 is a flowchart illustrating an example of a processing procedure of a reaction force generation process performed by the reaction force generation processing unit 31 of the control unit 10. In the control unit 10, a predetermined sampling time, for example, 10 msec. Each time, the arithmetic processing of FIG. 3 is performed. It should be noted that in this arithmetic processing, there is no particular step for communication, but the calculated information is updated and stored in the storage device as needed, and the information stored in the storage device is read into the arithmetic processing device as needed. .
[0019]
In this calculation process, first, in step S1, the vehicle speed V detected by the vehicle speed sensor 23, the tire turning shaft torque Tt detected by the axial force sensor 21, the steering angle δ detected by the steering angle sensor 3, and the steering torque. The steering torque Ts detected by the sensor 4 is read.
Next, the process proceeds to step S2 to calculate a time differential value of the steering angle δ read in step S1, that is, a steering angular velocity δ '.
[0020]
Next, the process proceeds to step S3, and the steering angle coefficient Ks is calculated based on the vehicle speed V read in step S1 according to the control map of FIG. In the control map of FIG. 4, the horizontal axis represents the vehicle speed V and the vertical axis represents the steering angle coefficient Ks. ₁ Hereinafter, the steering angle coefficient Ks becomes “0” and the predetermined vehicle speed v ₁ Vehicle speed v greater than ₂ In the above region, the steering angle coefficient Ks is set to “1” and the vehicle speed v ₁ To v ₂ During this period, the steering angle coefficient Ks increases from “0” to “1” in proportion to the increase in the vehicle speed V.
[0021]
Note that the predetermined vehicle speed v ₁ Is set, for example, to a vehicle speed range in which stationary stop at the time of stop or tire self-aligning torque is not sufficiently generated, for example, about 20 km / h. It is known that the tire steering load is high in this region.
Next, the process proceeds to step S4 to perform a known counter determination process shown in FIG. 5, for example, to determine whether or not the vehicle is in the counter steer state.
[0022]
In this counter determination process, as shown in FIG. 5, first, in step S21, the absolute value of the steering angle δ is compared with a counter determination value δs for determining whether or not countersteering is being performed. The counter determination value δs is set to a value near the neutral point, for example, about ± 10 °. This is the target steering reaction torque Tδ ^* Is set according to the steering angle, the target steering reaction torque Tδ ^* Is required to be switched in a very small range, that is, a range in which the absolute value | δ | of the steering angle is close to zero.
[0023]
When the absolute value | δ | of the steering angle δ is equal to the counter determination value δs in the process of step S21, the process proceeds to step S22, and the steering angle δ and the steering angle stored in the predetermined storage area during the previous execution of the process. The angular velocity δ ′ is updated and stored in a predetermined storage area as a previous value, and the steering angle δ and the steering angular velocity δ ′ at the time of execution of the current process are stored in a predetermined storage area as a current value.
[0024]
Next, the process proceeds to step S23, where the signs of the previous and current values of the steering angle δ and the steering angular velocity δ 'when the steering angle | δ | is the counter determination value δs are compared.
Here, at the time of rapid turning from near the neutral point, the relationship between the steering angle and the sideslip angle of the front wheels is maintained, so it is not necessary to stop the control for suppressing the steering reaction force. Therefore, it is necessary to distinguish between counter-steering and sudden turning from near the neutral point. In order to make this distinction, the signs of the previous value and the current value of the steering angle δ and the steering angular velocity δ ′ are compared. At the time of countersteering, the direction of steering, that is, the sign of the steering angle is different between the current value δn and the previous value δn-1. Also, the sign of the current value δn of the steering angle, the current value δ'n of the steering angular velocity, and the sign of the previous value δ'n-1 of the steering angular velocity match.
[0025]
Therefore, it is possible to distinguish between countersteer steering and sudden steering from near the neutral point based on these conditions.
Then, in the process of step S23, when the previous value and the current value of the steering angle and the steering angular velocity satisfy the sign condition that can be regarded as the counter steer steering, the process proceeds to step S24, and then, The current steering angular velocity δ 'and the threshold δ of the steering angular velocity δ' _TH '.
[0026]
Here, the steering angular velocity at the time of counter-steering steering is faster than that at the time of normal steering. _TH And the current value δ ′ of the steering angular velocity, and the current value δ ′ _TH If it is equal to or greater than ', the process proceeds to step S25, where it is determined that the vehicle is in the counter steer state, and the counter correction coefficient Kc is set to Kc = Kcmax.
[0027]
On the other hand, when the sign condition is not satisfied in the processing of the step S23, and when the steering angular velocity δ ′ is equal to the threshold δ in the processing of the step S24. _TH ', It is determined that the vehicle is not in the counter steer state, and the process ends.
If it is determined in step S21 that the absolute value | δ | of the steering angle δ is not equal to the counter determination value δs, the process proceeds to step S26, and if it is detected that the steering angle δ has become δ = 0. Then, the flow shifts to step S27, where the counter correction coefficient Kc is set to Kc = 1. Then, the counter determination processing ends. If it is not detected in step S26 that the steering angle δ has become δ = 0, the process is terminated.
[0028]
After the counter determination process is performed in the process of step S4, the process proceeds to step S5, where the steering angle coefficient Ks calculated in step S3 and the absolute value of the steering angle δ read in step S1 are calculated. , And the counter correction coefficient Kc to calculate the steering angle influence degree eδ.
Next, the process proceeds to step S6, where the steering angle influence eδ calculated in step S5 and the tire turning shaft torque Tt detected by the axial force sensor 21 read in step S1 are calculated according to the control map of FIG. Based on this, the basic steering reaction torque Tδ corresponding to the tire turning shaft torque Tt is calculated.
[0029]
In the control map of FIG. 6, the horizontal axis represents the tire turning shaft torque Tt, and the vertical axis represents the basic steering reaction torque Tδ. In FIG. 6, a characteristic line m1 consisting of a curve shown by a solid line is a generation range of the steering reaction torque when no disturbance is applied, which is estimated from the steering angle δ and the vehicle speed V. The basic steering reaction torque Tδ is set to increase as the torque Tt increases, and the change amount of the basic steering reaction torque Tδ with respect to the change amount of the tire turning shaft torque Tt decreases as the tire turning shaft torque Tt decreases. Is set so that the change amount of the basic steering reaction torque Tδ with respect to the change amount of the tire turning shaft torque Tt decreases as the tire turning shaft torque Tt increases.
[0030]
In FIG. 6, a characteristic line m2 composed of a straight line indicated by a broken line is set so that the inclination is constant and the basic steering reaction torque Tδ is smaller than the characteristic line m2. The intercept with the axis changes according to the steering angle influence eδ, and when the steering angle influence eδ is the minimum value, the intercept becomes the minimum value and the steering angle influence eδ becomes the threshold value eδ. _TH In this case, the maximum value of the basic steering reaction torque Tδ based on the characteristic line m2 approaches the maximum value of the basic steering reaction torque Tδ on the characteristic line m1 without limit.
[0031]
The basic steering reaction torque Tδ is set according to a characteristic line m1 indicated by a curve in FIG. 6 and a characteristic line m2 indicated by a straight line, and the tire turning shaft torque Tt is determined by the characteristic line m1 and the steering angle influence degree. When it is equal to or smaller than the tire turning shaft torque at the intersection with the characteristic line m2 corresponding to eδ, the basic steering reaction force torque Tδ is set based on the characteristic line m1, and the tire turning shaft torque Tt is set to the characteristic lines m1 and m2. When the torque exceeds the tire turning shaft torque at the intersection, it is set based on the characteristic line m2.
[0032]
In other words, assuming that the steering angle coefficient Ks is constant and the vehicle is in a non-counter-steer steering state, the smaller the steering angle | δ | Moving. The basic steering reaction torque Tδ is determined according to the characteristic line m1 and m2. In a region where the tire turning shaft torque Tt is smaller than the intersection between the two, the basic steering reaction torque Tδ is determined according to the characteristic line m1. Tδ is set, and in a region where the tire turning shaft torque Tt is larger than the intersection of the two, the basic steering reaction torque Tδ is set according to the characteristic line m2. Therefore, if the tire turning shaft torque increases in accordance with the increase in the steering angle δ, the basic steering reaction torque Tδ increases along the characteristic line m1 in accordance with the increase, and in a state where there is no disturbance such as kickback, As the tire turning shaft torque Tt increases, the basic steering reaction torque Tδ is set in accordance with the increase, and, for example, during a small steering angle such as during cant driving or a short-time disturbance or kickback during steering. When the tire turning shaft torque Tt becomes large due to, for example, the steering angle is constant, the characteristic line is switched from the characteristic line m1 to the characteristic line m2, and the basic steering reaction torque Tδ according to the characteristic line m1 is changed according to the characteristic line m2. Is set to a smaller basic steering reaction torque Tδ. Therefore, it is possible to prevent the fluctuation of the steering reaction torque due to the steering wheel being removed or the like.
[0033]
In a region where the vehicle speed V is relatively low, the steering angle coefficient is set to “0”, so that the basic steering reaction torque Tδ is set according to the characteristic line m2 having the minimum intercept. That is, when the vehicle is stationary or at a very low speed, the tire turning shaft torque is larger than that during traveling. Therefore, when the characteristic line m2 is changed according to the steering angle, the tire turning shaft torque becomes larger as the steering angle increases. When the vehicle speed V increases, the basic steering reaction torque Tδ also increases. ₂ If the steering angle coefficient is smaller than 0, the steering angle coefficient is set to a value smaller than “0” or “1”. An increase in the reaction torque Tδ is suppressed. Accordingly, an increase in the basic steering reaction torque Tδ due to an increase in the steering angle at the time of stationary steering or fine constant speed is prevented.
[0034]
When the vehicle is in the counter steer steering state, the basic steering reaction torque Tδ is set along the characteristic line m1 regardless of the steering angle influence degree eδ. That is, the counter correction coefficient Kcmax is such that the steering angle influence degree eδ (= Ks · | δ | · Kcmax) is equal to the threshold value eδ irrespective of the values of the steering angle δ and the steering angle coefficient Ks. _TH When the value is set to the above value and the steering is in the counter-steering state, the counter correction coefficient Kc is set to Kc = Kcmax. _TH As described above, since the characteristic line m2 approaches the characteristic line 1, the basic steering reaction torque Tδ is set along the characteristic line m1 regardless of the steering angle influence degree eδ.
[0035]
When the basic steering reaction torque Tδ is calculated in step S6 in this manner, the process proceeds to step S7, and the vehicle speed coefficient Kv corresponding to the vehicle speed V read in step S1 is calculated according to the control map of FIG. I do. In the control map of FIG. 7, the vehicle speed coefficient Kv is set to a relatively large constant value in a region where the vehicle speed V is small, and the speed coefficient Kv is set to a relatively small constant value in a region where the vehicle speed V is large. Is set so that the vehicle speed coefficient Kv decreases linearly as the vehicle speed V increases.
[0036]
Next, the process proceeds to step S8, and the damping torque Td is calculated based on the steering angular velocity δ ′ calculated in step S2 according to the control map of FIG. The damping torque Td is a weight or a damping force intentionally applied to the steering wheel 1. Therefore, the control map of FIG. 8 is set such that the higher the steering angular velocity δ ′, the linearly the damping torque Td increases.
[0037]
Next, the process proceeds to step S9, in which the damping torque Td calculated in step S8 is subtracted from the basic steering reaction torque Tδ calculated in step S6, and this is subtracted from the target steering reaction torque Tδ. ^* And
Next, the process proceeds to step S10, in which the target steering reaction torque Tδ calculated in step S9. ^* Is subtracted from the steering torque Ts read in step S1, and a drive control signal corresponding to the torque to be generated by the reaction force generating motor 5 is generated based on the subtraction, and is output to the motor driver 31d.
[0038]
As a result, the motor driver 31d controls the driving of the reaction force generating motor 5, and the target steering reaction force torque Tδ ^* Is generated.
Next, the operation of the above embodiment will be described.
Now, when the vehicle speed V is a predetermined value v ₂ If the steering angle coefficient is larger than the steering angle coefficient Ks, the steering angle coefficient Ks is set to Ks = 1.
[0039]
If no disturbance occurs, the steering is performed, and when the tire turning shaft torque Tt increases with this, the counter correction coefficient Kc is set to Kc = Kcmax because of the non-countersteer state. Then, in a region where the tire turning shaft torque Tt is relatively small, the intercept of the characteristic line m2 increases with an increase in the steering angle, and the basic steering reaction torque increases along the characteristic line m1 shown in the control map of FIG. Tδ is set. At this time, the characteristic line m1 in FIG. 6 is based on the basic steering reaction torque Tδ predicted to be generated according to the steering angle and the vehicle speed when the tire turning shaft torque Tt is generated in a state where there is no disturbance in advance. Since the setting is set, a steering reaction torque that does not give a sense of incongruity with the steering acts on the steering wheel 1. Further, since the basic steering reaction torque Tδ when the characteristic line m1 and the characteristic line m2 intersect increases as the steering angle increases, the characteristic line m2 changes as the steering angle increases. The intercept increases, and the basic steering reaction torque Tδ is set along the characteristic line m1 with the increase in the tire turning shaft torque Tt. The steering reaction torque Tδ can be set.
[0040]
If disturbance occurs due to kickback or cant running while turning at a constant steering angle, the tire turning shaft torque Tt fluctuates at a constant steering angle. The basic steering reaction torque Tδ is set based on the characteristic line m2 specified according to the degree of influence eδ.
Here, as shown in FIG. 6, the characteristic line m2 composed of a straight line is set so that the basic steering reaction torque Tδ is smaller than the characteristic line m1 composed of a curve. Therefore, the variation of the basic steering reaction torque Tδ based on the characteristic line m2 is smaller than the variation of the basic steering reaction torque Tδ based on the characteristic line m1 with respect to the variation of the tire turning shaft torque Tt. Therefore, it is possible to prevent the steering wheel from being pulled due to the fluctuation of the steering reaction torque due to the disturbance. At this time, the basic steering reaction torque Tt is detected based on the characteristic line m2 specified by the tire turning shaft torque Tt and the steering angle influence degree eδ. Therefore, the basic steering reaction torque Tδ can be suppressed by following the fluctuation of the tire turning shaft torque Tt due to the disturbance, and the fluctuation of the steering reaction torque can be reduced even in the early stage of kickback. Variations in steering reaction torque due to disturbance can be reduced quickly.
[0041]
Also, when the vehicle enters the cant road from a cant-free road surface, the tire turning shaft torque Tt fluctuates even at the same steering angle, but when the tire turning shaft torque Tt fluctuates, the tire turning shaft torque Tt changes. The basic steering reaction torque Tδ is specified based on Tt and the characteristic line m2 corresponding to the steering angle influence eδ. At this time, the amount of change in the basic steering reaction torque Tδ based on the characteristic line m2 is smaller than the amount of change in the basic steering reaction torque Tδ based on the characteristic line m1. Variations in the reaction torque can be reduced.
[0042]
In addition, when the driver performs counter-steer steering during turning, this is detected by the counter determination processing, and the counter correction coefficient Kc is set to Kc = Kcmax. Therefore, the steering angle influence degree eδ is equal to the threshold value eδ. _TH As described above, since the characteristic line m2 approaches the characteristic line 1, the basic steering reaction torque Tδ is set along the characteristic line m1 regardless of the steering angle influence degree eδ. Therefore, when counter steering is performed, the basic steering reaction torque Tδ is set to a value corresponding to the tire turning shaft torque Tt. Therefore, at the time of counter steer steering, the basic steering reaction torque Tδ is set based on the characteristic line m1 instead of the characteristic line m2 in which the fluctuation of the basic steering reaction torque Tδ is small with respect to the fluctuation of the tire turning shaft torque Tt. A steering reaction torque fluctuation corresponding to the fluctuation of the tire turning shaft torque Tt accompanying the counter steer steering is generated, and it is possible to prevent the steering reaction torque from becoming too light even during the counter steer steering. It is possible to avoid giving the driver an uncomfortable feeling due to the reduction of the steering reaction torque during the steer steering.
[0043]
On the other hand, when stationary steering is performed, the steering angle coefficient Ks is set to “0”, the steering angle influence eδ becomes zero, and the characteristic line m2 indicates the basic steering angle corresponding to the tire turning shaft torque Tt. The characteristic line is set such that the reaction torque Tδ is minimized. At this time, even when the characteristic line m2 is the minimum value, in a region where the tire turning shaft torque Tt is relatively small, the basic steering reaction force torque Tδ is set along the characteristic line m1. Accordingly, when the steering is started and the tire turning shaft torque Tt is small, the basic steering reaction force torque Tδ is set along the characteristic line m1, so that the steering reaction force according to the fluctuation of the tire turning shaft torque Tt is reduced. Therefore, a certain degree of steering reaction torque is generated at the start of stationary steering, and when the tire turning shaft torque Tt further increases, the basic steering reaction force is changed based on the characteristic line m2 instead of the characteristic line m1. The torque Tδ is set, and the fluctuation of the basic steering reaction torque Tδ with respect to the fluctuation of the tire turning shaft torque Tt is smaller than the characteristic line m1. Here, when the characteristic line m2 is changed in accordance with the increase in the steering angle without considering the steering angle coefficient Ks corresponding to the vehicle speed V, the steering reaction torque becomes larger as the steering amount increases during stationary operation. It will be bigger. However, since the characteristic line m2 is specified in accordance with the steering angle coefficient Ks corresponding to the vehicle speed V, the steering reaction torque does not increase significantly with the increase in the steering amount during stationary operation. It is possible to prevent the driver from feeling uncomfortable.
[0044]
When the vehicle speed V is v ₁ To v ₂ In the case where the steering angle coefficient is between the values, the steering angle coefficient is set to a value from “0” to “1”. For this reason, the steering angle influence degree eδ is determined by the vehicle speed V being v ₂ It is set to a smaller value than when it is larger than. Therefore, in the region where the vehicle speed is relatively low, or in the vehicle speed region where the self-aligning torque is not sufficiently generated as in the above-described stationary operation and the region where the tire turning load is high, the basic steering reaction along the characteristic line m1 is performed. By setting the force torque Tδ, a steering reaction torque corresponding to the increase of the tire turning shaft torque Tt is generated up to a certain tire turning shaft torque Tt, and thereafter, the basic steering reaction force along the characteristic line m2. By setting the torque Tδ to reduce the fluctuation of the basic steering reaction torque Tδ caused by the increase in the tire turning shaft torque Tt, it is possible to prevent the steering reaction torque Tδ from increasing in accordance with the increase in the steering amount. be able to.
[0045]
Therefore, an appropriate steering reaction torque can be generated over the entire vehicle speed range, and a good steering feeling can be given to the driver.
In the above embodiment, the case where the control unit is constructed by a microcomputer has been described. However, the present invention is not limited to this, and the control unit may be constructed by an equivalent arithmetic circuit or logic circuit.
[0046]
Here, in the above embodiment, the steering wheel 1 and the steering shaft 2 correspond to the steering mechanism, the rack shaft 11, the tie rod 16 and the steered wheels 20 correspond to the steering mechanism, and the steering angle sensor 3 is the steering angle detecting means. , The axial force sensor 21 corresponds to the steering shaft torque detecting means, the reaction force generating motor 5 and the reaction force generation processing of FIG. 3 correspond to the reaction force torque applying means, and the vehicle speed sensor 23 corresponds to the vehicle speed detecting means. Correspondingly, the counter determination processing in FIG. 5 corresponds to the counter steer operation detecting means, the characteristic line m1 in FIG. 6 corresponds to the first characteristic, and the characteristic line m2 corresponds to the second characteristic.
[Brief description of the drawings]
FIG. 1 is an overall schematic configuration diagram showing a position embodiment of an electric steering device of the present invention.
FIG. 2 is a control block diagram showing a configuration of a control unit 10 of FIG.
FIG. 3 is a flowchart illustrating an example of a processing procedure of a reaction force generation process executed by a control unit 10 of FIG. 1;
FIG. 4 is a control map showing a correspondence between a vehicle speed and a steering angle coefficient.
FIG. 5 is a flowchart illustrating an example of a processing procedure of a counter determination process of FIG. 3;
FIG. 6 is a control map showing a correspondence between a tire turning shaft torque Tt and a basic steering reaction torque Ts.
FIG. 7 is a control map showing a correspondence between a vehicle speed V and a vehicle speed coefficient Kv.
FIG. 8 is a control map showing a correspondence between a steering angular velocity δ ′ and a damping torque Td.
[Explanation of symbols]
1 Steering wheel
2 Steering shaft
3 Steering angle sensor
4 Steering torque sensor
5 Reaction force generating motor
10 Control unit
14 1st steering motor
15 Second steering motor
21 Axial force sensor
22 Displacement sensor
23 Vehicle speed sensor

Claims (9)

The steering mechanism mechanically separated from the steering mechanism is drive-controlled in accordance with the steering amount of the steering mechanism, and the reaction force torque accompanying the steering of the steering mechanism is applied to the steering mechanism. In an electric steering device,
A steering angle detecting means for detecting a steering angle; applying a reaction torque corresponding to a steering shaft torque of the steering mechanism to the steering mechanism; An electric steering apparatus characterized by changing according to a steering angle detected by an angle detecting means. The steering mechanism mechanically separated from the steering mechanism is drive-controlled in accordance with the steering amount of the steering mechanism, and the reaction force torque accompanying the steering of the steering mechanism is applied to the steering mechanism. In an electric steering device,
Steering angle detection means for detecting a steering angle;
Turning shaft torque detecting means for detecting a turning shaft torque of the turning mechanism;
Reaction torque applying means for applying to the steering mechanism a reaction torque corresponding to the turning shaft torque detected by the turning shaft torque detecting means,
The electric steering device, wherein the reaction torque applying means changes a characteristic of the reaction torque with respect to the turning shaft torque in accordance with the steering angle detected by the steering angle detection means. The electric steering apparatus according to claim 2, wherein the reaction torque applying means changes the characteristic such that the smaller the steering angle, the smaller the reaction torque with respect to the steered shaft torque. A vehicle speed detecting means for detecting a vehicle speed,
The electric steering apparatus according to claim 2, wherein the reaction torque applying unit changes the characteristic such that the smaller the vehicle speed, the smaller the reaction torque with respect to the steered shaft torque. 5. . A counter steer operation detecting means for determining whether or not a counter steer operation is being performed;
The reaction torque applying means uses a characteristic set according to a reaction torque corresponding to a turning shaft torque when no disturbance acts on the vehicle as a reference, and changes the characteristic in the reference characteristic. ,
5. The electric steering apparatus according to claim 2, wherein the characteristic is not changed when the counter steer operation is detected by the counter steer operation detecting means. The reaction torque applying means determines the reaction torque based on the first characteristic when the turning shaft torque is equal to or less than a threshold, and when the turning shaft torque is larger than the threshold, The reaction torque is determined based on a second characteristic in which the variation of the reaction torque with respect to the variation of the steering shaft torque is smaller than the first characteristic, and the reaction torque is detected by the steering angle detection means. The electric steering apparatus according to claim 2, wherein the threshold value is set to a larger value as the steering angle becomes larger. A vehicle speed detecting means for detecting a vehicle speed,
7. The electric steering apparatus according to claim 6, wherein the reaction torque applying unit sets the threshold value to a larger value as the vehicle speed increases. The electric steering apparatus according to claim 6, wherein the first characteristic is set according to a reaction torque corresponding to a steering shaft torque when no disturbance acts on the vehicle. 9. . A counter steer operation detecting means for determining whether or not a counter steer operation is being performed;
When the counter steer operation is detected by the counter steer operation detecting means, the reaction torque is set based on the first characteristic regardless of the magnitude of the turning shaft torque. An electric steering device according to any one of claims 6 to 8.

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