JPH10310074A - Steering controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect steering load without providing a power sensor and solve problems of wiring and durability, by providing a steering load arithmetic means calculating steering load based on the load state of a steering driving means. SOLUTION: Detection results of a steering angle sensor 13, a speed sensor 15, a stroke sensor 25 and a current sensor 26 are imparted to a control part C. Based on these detection results, the control part C performs a steering control and a reaction control. This control part C is provided with a steering control part 30 and a reaction control part 40. The steering control part 30 controls the steering location of a steering wheel 21 by driving and controlling a steering shaft motor 23 and the reaction control part 110 controls steering reaction imparted to a steering handle 11 by driving and controlling a steering shaft motor 14. Both of these control parts 30, 40 calculate steering load based on the load state of the steering shaft motor 23. Therefore, the load torque of the steering shaft motor 23 is determined as steering load and both of the control parts 30, 40 enforce each control based on the steering load determined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device for turning steered wheels in conjunction with a steering wheel.

[0002]

2. Description of the Related Art An example of a conventional steering control device is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-38270. In this steering control device, a steering angle of a steering wheel is detected by a steering angle sensor, a steering angle of a steered wheel is detected by a steering angle sensor, and steering control of the steered wheels is performed based on the detection results. ing. In addition, an axial force sensor is provided for a tie rod interposed between a steered wheel and a steered shaft to detect a steering load (steering reaction force) as an axial force applied to the tie rod during steering. The steering reaction force applied to the steering wheel is controlled based on the detection result.

[0003]

As described above, conventionally,
Although the steering load is detected by an axial force sensor, since this axial force sensor is provided for a movable tie rod, it is difficult to route wiring and the like, and the durability is low. I will.

Accordingly, an object of the present invention is to provide a steering control device capable of detecting a steering load without providing an axial force sensor and solving problems such as wiring and durability.

[0005]

According to a first aspect of the present invention, there is provided a steering control device for turning a steered wheel in conjunction with a steering wheel, wherein the steering control device is mechanically separated from the steering wheel and connected to the steered wheel. And a turning drive calculating means for calculating a turning load based on the load state of the turning drive means.

[0006] Since the turning load is an external force applied to the turning drive means, the turning load can be detected by detecting the load state of the turning drive means. For example, when the steering drive means is a DC motor, the load state of the motor can be detected by the applied voltage value to the motor and the number of rotations of the motor, and the load state of the motor can also be detected by the current value flowing through the motor. it can. The turning load calculating means calculates the turning load based on the load state of the motor detected in this way.

According to a second aspect of the present invention, there is provided a steering control device according to the first aspect, wherein the steering drive means is provided based on a deviation between a target steered position of the steered wheels and an actual steered position and a steered load. The vehicle is provided with a turning control amount calculating means for calculating the turning control amount to be given.

[0008] Such a turning control amount calculating means sets the deviation (steady deviation) between the target turning position and the actual turning position to zero when the turning control system goes through a transient state to a steady state. It is applied to the control method that performs The control amount based on the deviation between the target turning position and the actual turning position is a control amount corresponding to the kinetic energy required for the steered wheels to be displaced to the target turning position against the turning load. The control amount based on the rudder load is
After the steered wheel has moved to the target steered position, the control amount is equivalent to the energy (potential energy) required to stop at that position and is balanced with the steered load. The turning control amount calculation means calculates the turning control amount as the sum of these two control amounts.

A steering control device according to a third aspect of the present invention is the steering control device according to the first aspect, wherein a steering wheel is provided to a steering drive means based on a deviation between a target steering position of a steered wheel and an actual steering position. A steering control amount calculation means for calculating the control amount and correcting the calculated steering control amount based on the steering load is provided.

[0010] Such a steering control amount calculating means calculates a predetermined steady-state deviation as a deviation between the target turning position and the actual turning position when the turning control system is in a steady state after a transient state. Applied to the control method that remains. When such a control method is adopted, the steady-state deviation changes according to the magnitude of the steering load, and therefore, the steering control amount based on the deviation between the target steering position and the actual steering position is changed. By performing correction based on the steering load, the steady-state deviation can be made constant regardless of the steering load.

According to a fourth aspect of the present invention, there is provided a steering control device according to the first aspect, wherein a reaction force applying means for applying a steering reaction force to the steering wheel, and a target steering position of the steering wheel and an actual steering position. Based on the deviation and steering load,
A reaction force control amount calculating means for calculating a reaction force control amount to be applied to the reaction force applying means.

The reaction force control amount calculation means calculates the reaction force control amount based on not only the deviation between the target steering position and the actual steering position, but also the steering load, so that
A feeling of response according to the state of the steering load can be provided.

A steering control device according to a fifth aspect of the present invention is the steering control device according to the first aspect, wherein a steering control amount to be applied to the steering driving means is determined based on a deviation between a target yaw rate and an actual yaw rate and a steering load. A steering control amount calculating means for calculating is provided.

The turning control amount calculating means sets a deviation between a target yaw rate to be a control target and a detected actual yaw rate to zero when the turning control system is in a steady state after a transient state. It is applied to a four-wheel steering system of a yaw rate feedback system employing a control system. In this case, the turning load calculating means calculates the turning load on the rear wheel based on the load state of the turning driving means connected to the turning wheel serving as the rear wheel. Further, the turning control amount calculating means calculates a turning control amount to be applied to the rear wheel-side turning driving means based on the deviation between the target yaw rate and the actual yaw rate and the turning load. As a result, even when the present invention is applied to a four-wheel steering system, steering control according to the steering load state on the rear wheel side can be performed.

According to a sixth aspect of the present invention, there is provided the steering control device according to the first aspect, wherein a steering control amount to be applied to the steering drive means is calculated based on a deviation between the target yaw rate and the actual yaw rate. The vehicle is provided with a turning control amount calculating means for correcting the turned turning amount based on the turning load.

Such a steering control amount calculating means calculates a deviation between a target yaw rate to be a control target and a detected actual yaw rate when the steering control system goes through a transient state to a steady state. The present invention is applied to a four-wheel steering system of a yaw rate feedback system that employs a control system that leaves a steady-state deviation. In this case, the turning load calculating means calculates the turning load on the rear wheel based on the load state of the turning driving means connected to the turning wheel serving as the rear wheel. The steering control amount calculating means calculates a steering control amount to be applied to the rear-wheel-side steering drive means based on a deviation between the target yaw rate as a control target and the detected actual yaw rate. The steering control amount is corrected based on the steering load. As a result, the steady-state deviation between the target yaw rate and the actual yaw rate can be made constant irrespective of the steering load, and even when applied to a four-wheel steering system, the steering according to the steering load state on the rear wheel side can be performed. Control becomes possible.

The operation performed by the various operation means described in each claim is not limited to the case where the operation is performed using a mathematical expression. For example, the operation result is mapped in advance, and the detection result is added to each detection result. The case where a calculation result is obtained by searching this map based on the above is also included.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of a steering control device according to the first embodiment. This steering control device includes a master unit A operated by a driver, a slave unit B for steering the steered wheels 21, a master unit A and a slave unit B mechanically separated from each other.
And a control unit C for electrically controlling the above.

The master unit A includes a steering shaft 12 on which a steering handle 11 is mounted, and a steering shaft motor 14 for driving the steering shaft 12 to rotate.
Is composed of, for example, a DC motor. Also, the steering shaft 12
Is provided with a steering angle sensor 13 for detecting an actual steering position of the steering wheel 11.

The slave section B includes a steered shaft motor 23 serving as a drive source when the steered shaft 22 is displaced and driven. The steered shaft motor 23 is constituted by, for example, a DC motor. Between the steered shaft motor 23 and the steered shaft 22, the rotational motion of the steered shaft motor 23 is
Is displaced in the axial direction. Also,
The steered shaft motor 23 is provided with a current sensor 26 for detecting a current value flowing through the steered shaft motor 23. As described later in detail, based on the current value detected by the current sensor 26, The steering load as the axial force applied to the steering shaft 22 is obtained. On the other hand, the steered shaft 22 is provided with a stroke sensor 25 for detecting the displacement position of the steered shaft 22. Since the displaced position of the steered shaft 22 corresponds to the steered position of the steered wheels 21, By detecting the displacement position of the rudder shaft 22 with the stroke sensor 25, the steered position of the steered wheel 21 is detected.

The control section C is provided with detection results of the steering angle sensor 13, the vehicle speed sensor 15, the stroke sensor 25, and the current sensor 26, and performs steering control and reaction force control based on the detection results. The control unit C includes a steering control unit 3
0, and a reaction force control unit 40. The steering control unit 30 controls the steered position of the steered wheels 21 by performing drive control of the steering shaft motor 23, and the reaction force control unit 40 controls the steering shaft. Motor 14
By performing the drive control, the steering reaction force applied to the steering wheel 11 is controlled.

The two control units 30 and 40 are provided with a steering shaft 22.
The steering load is calculated based on the load state of the steering shaft motor 23 without providing an axial force sensor for detecting the axial force applied to the steering shaft. That is, the axial force applied to the steered shaft 22 is a steered load, and this steered load acts as a load on the steered shaft motor 23. Therefore, the load torque of the steered shaft motor 23 is determined as the steered load, and the two control units 30 and 40 perform each control based on the determined steered load.

Here, a description will be given of a calculation method for obtaining the turning load from the load state of the turning shaft motor 23. In FIG.
The basic characteristics of the DC motor constituting the steered shaft motor 23 are shown. When the voltage Vo is applied to the motor, the motor reaches a certain number of rotations and rotates at a constant speed when no load is applied to the motor. The rotation speed of the motor at this time is indicated by Ro, and the current flowing through the motor at this time is indicated by Io. When a load is applied to the motor from this state by an electromagnetic brake or the like, the number of revolutions decreases, the current increases, and eventually stops. The load torque of the motor at this time is represented by To, and the current is represented by In. FIG.
In the graph, the current I and the rotational speed R are plotted on the vertical axis, and the load torque T of the motor is plotted on the horizontal axis, and the RT characteristic and the IT characteristic are each represented by a straight line.

According to this graph, the voltage applied to the motor is V
At o, when the load torque of the motor is Ts, the value of the current flowing through the motor is Is, and the rotation speed of the motor is R1. Therefore, the steering load as the load torque of the motor can be obtained by detecting the rotational speed indicating the load state of the motor from the RT characteristic. Normally, the DC motor performs drive control by changing the applied voltage, and thus the applied voltage value is a known value.

The voltage applied to the motor is changed from Vo to V1.
, The rotation speed of the motor changes from R1 to R2, but the current value Is at that time does not change. Therefore, it is understood that the current value flowing through the motor is a value representing the load of the motor regardless of the applied voltage, and based on the IT characteristics,
By detecting the value of the current flowing through the motor, the steering load as the load torque of the motor can be obtained.

As an example, the load torque of the motor is actually obtained based on the rotation speed R2 and the applied voltage V1. At this time, assuming that the basic characteristics of the motor at a reference applied voltage V0, such as at the time of an applied voltage at 100% duty, are known, from the graph of FIG. − (To / Ro) · R + To. Since the characteristics of the motor change in proportion to the duty value of the applied voltage, Tx can be expressed as Tx = To · V1 / Vo from the graph. Since the slope of the straight line is the same as the basic characteristic, the straight line connecting Rx and Tx is T = − (To / Ro) · R + Tx = − (To / Ro) · R + To · V1 / Vo. Therefore, the load torque Ts of the motor at this time is
By substituting the rotation speed R2 for R in the above equation, it can be obtained as Ts = − (To / Ro) · R2 + To · V1 / Vo (1)

In order to determine the load torque Ts of the motor based on the current value Is flowing through the motor, T = a · I + b, where a and b are constants from the IT characteristic in the graph of FIG. be able to. Therefore, by substituting the detected current value Is for I in the above equation, the load torque Ts of the motor is obtained.
Can be obtained as Ts = a · Is + b (2)

The steering control unit 30 and the reaction force control unit 40, which constitute the control unit C, calculate the load torque of the motor as the steering load in this manner, and control each control amount based on the calculated steering load. Is calculated.

Hereinafter, the arithmetic processing performed by the steering control unit 30 will be described.

The turning control section 30 calculates the deviation (steady deviation) between the target turning position Xm of the steered wheels 21 and the actual turning position Xr when the turning control system goes through a transient state to a steady state. A control method for zeroing is adopted. As shown in the control block diagram of FIG.
2 and an applied voltage calculator 33.

In the target steered position calculating section 31, the steered wheels 21
Is calculated as the target steering position Xm. The target steered position Xm is calculated as Xm = F (θr, S) from a function F having the actual steering position θr of the steering wheel 11 and the vehicle speed S as variables.
The target steered position calculating unit 3
1 is provided with a two-dimensional map from which the target steering position Xm can be obtained from the values of the actual steering position θr and the vehicle speed S, and the actual steering position θr of the steering wheel 11 detected by the steering angle sensor 13.
Based on the vehicle speed S detected by the vehicle speed sensor 15, the target steered position Xm is searched on a map. Then, a deviation (Xm−Xr) from the actual turning position Xr, which is a detection result of the stroke sensor 25, is given to the applied voltage calculation unit 33.

In the load calculation section 32, as described above, the steering load is calculated from the detection result Is of the current sensor 26 as described in (2) above.
The calculated result is given to the applied voltage calculation unit 33.

The applied voltage calculator 33 calculates a control amount (steering) indicating the Duty value of the applied voltage applied to the steered shaft motor 23 based on the calculation results of the target steered position calculator 31 and the load calculator 32. The control amount V is calculated based on the following equation (3).

V = Kp1 · (Xm−Xr) + Vs (3) The first term on the right side of the equation (3) is the target steered position X of the steered wheels 21.
This is a term obtained by multiplying the deviation between m and the actual steered position Xr by a proportional gain Kp1, and a control amount proportional to the deviation is calculated, which is necessary when the steered wheels 21 are displaced to the target steered position. A control amount corresponding to the following kinetic energy is shown.
Vs in the second term on the right side is a term based on the steering load calculated by the load calculation unit 32, and is necessary for the steered wheels 21 to move to the target steering position Xm and then stop at that position. , The control amount corresponding to the energy (potential energy) balanced with the steering load. In other words, the voltage value Vs as the control amount is an applied voltage applied to the steered shaft motor 23 so that the steered wheel 21 is in balance with the steered load Ts and stops at the target steered position. According to the graph of FIG. 2 described above, this applied voltage Vs
Is the applied voltage value at which the rotation speed of the motor is zero and the motor load is Ts, and Vs is obtained by the following equation (4) from the relationship with the basic characteristics of the motor.

Vs = (Ts / To) · Vo (4) The turning control unit 30 thus operates the turning shaft motor 23.
The control amount V to be applied to the vehicle is calculated, and by adopting such a control method, the vehicle speed, the amount of turning, the road surface condition, the state of the tires, the number of passengers, etc., which affect the turning load, are changed. In this case, control can be performed with the same gain.

Further, since the characteristic of starting the motor, that is, the characteristic that a large current flows at the time of starting, can be used, the response delay can be sufficiently suppressed. More specifically, referring to FIGS. 4A and 4B, if the target steering position changes as shown in FIG. 4B by operating the steering wheel 11, the steering shaft motor 23 is a predetermined duty value (D
The rotation starts with the applied voltage of 1), and the number of rotations increases. Then, since the actual turning position of the steered wheels 21 approaches the target turning position, the turning control unit 30 shifts to control to decrease the rotation speed of the turning shaft motor 23, and the duty value of the applied voltage decreases to Ds. I do. At this Duty value Ds, the steered shaft motor 23 is balanced with the steered load, which is an external force, and the steered wheels 21 stop at that position. During this control operation, the load torque of the turning shaft motor 23 rapidly increases with the application of the voltage, and balances with the turning load as the rotation speed approaches R3. Also,
The load torque does not change even when the rotation speed of the motor is reduced. Therefore, by adopting such a control method,
A balance point that balances with the steering load can be estimated at an early stage. In addition, since the engine is quickly started at the time of starting, a response delay can be sufficiently suppressed.

Next, the arithmetic processing performed by the reaction force control unit 40 will be described.

As shown in FIG. 5, the reaction force controller 40 includes a target steering position calculator 41, a load calculator 42, and an applied voltage calculator 43.

The target steering position calculating section 41 calculates the target steering position θm of the steering wheel 11 as a control target based on the actual turning position Xr detected by the stroke sensor 25 and the detection result S of the vehicle speed sensor 15. It is calculating. In this calculation, an inverse function G of the function F used in the steering control unit 30 is used in order to give a unique correlation between the steering position and the steering position. The function F is the actual steering position θr and the vehicle speed S
By using a function G for calculating the target steering position θm from the actual steering position Xr and the vehicle speed S, which is the inverse function of this function F, the steered wheels 21 are calculated. The relationship between the steering position of the steering wheel 11 and the steering position of the steering wheel 11 can be uniquely correlated. Therefore, the target steering position θm can be obtained as θm = G (Xr, S) from the function G having the actual steering position Xr and the vehicle speed S as variables. X
A two-dimensional map is provided from which the target steering position θm can be obtained from the values of r and the vehicle speed S. Based on the actual turning position Xr detected by the stroke sensor 25 and the vehicle speed S detected by the vehicle speed sensor 15, A map search for the target steering position θm of the steering wheel 11 is performed. Then, a deviation (θm−θr) from the actual steering position θr, which is a detection result of the steering angle sensor 13, is given to the applied voltage calculation unit 43.

In the load calculating section 42, as described above, the steering load is calculated based on the detection result Is of the current sensor 26 as described in (2) above.
The calculation result is given to the applied voltage calculation unit 43 by the equation.

The applied voltage calculator 43 calculates the control amount (reaction force control amount) indicating the Duty value of the applied voltage applied to the steering shaft motor 14 based on the calculation results of the target steering position calculator 41 and the load calculator 42. ) V is calculated based on the following equation (5).

V = −Kp2 · (θm−θr) + Kp3 · Ts (5) In equation (5), the applied voltage for rotating the steering handle 11 in the return direction is set to +. The first term on the right side is proportional to the deviation between the target steering position θm and the actual steering position θr.
This is a term multiplied by 2. By this term, a control amount proportional to the deviation is calculated, and is a term corresponding to the weight given to the steering wheel 11. As a result, a torque proportional to the deviation between the actual steering position of the steering wheel 11 and the target steering position is given to the steering shaft motor 14. The second term on the right side is a term obtained by multiplying the turning load Ts detected by the turning shaft motor 23 by the proportional gain Kp3. According to the second term, the torque proportional to the turning load Ts is calculated by the steering wheel. 1
1 in the direction of returning to the neutral position.

The reaction force controller 40 calculates the control amount V to be applied to the steering shaft motor 14 in this manner. By adopting such a control method, the road surface has irregularities, collision with a curb, A change in the steering load caused by a change in the road surface state of the road μ, the state of the tires, the number of passengers, or the like can be realized by the driver as a difference in the weight applied to the steering wheel 11.

In the applied voltage calculation section 43, instead of the above equation (5), Kp4 and Kp5 are used as proportional gains, and V = −Kp4 · (θm−θr) + Kp5 · Ts (6) or V = −Kp5 · Ts · (θm−θr) (7) At this time, Kp5 = f
As (θr, S), Kp5 is set to the actual steering position θr and the vehicle speed S.
Set based on Thus, the steering handle 11
Can be corrected based on the actual steering position θr and the vehicle speed S. Particularly in the case of the equation (6), even if the steering load is zero, the steering wheel 11 Can be controlled to return to the neutral position.

Next, a second embodiment will be described.
In the second embodiment, in the steering control unit 30, when the steering control system is in a steady state after a transition state, the deviation between the target steering position Xm of the steered wheels 21 and the actual steering position Xr. A control method that leaves a predetermined steady-state error is adopted. In this case, the control block diagram is the same as that of FIG. 3 described above.
A control amount (steering control amount) V indicating a Duty value of the applied voltage applied to the turning shaft motor 23 is calculated based on the following equation (8), based on the calculation results of 1 and the load calculating unit 32. ing.

V = Kp6 · Ts · (Xm−Xr) (8) In the equation (8), Kp6 is a proportional gain represented by a predetermined constant, and is calculated as Kp6 · (Xm−Xr). The amount is corrected according to the steering load Ts calculated by the load calculation unit 32. By employing such an arithmetic expression, there is no inconvenience that the magnitude of the steady-state deviation between the target turning position Xm and the actual turning position Xr changes according to the magnitude of the turning load. In addition, the magnitude of the steady-state deviation can be constant regardless of the magnitude of the steering load. In other words, since the applied voltage is proportional to the motor load torque,
In a state where the steered shaft motor 23 is in balance with the steered load Ts, the equation (8) is expressed as k · Ts = Kp6, where k is a proportional coefficient.
Ts · (Xm−Xr) Therefore, 1 / (k · K
p6) = Xm-Xr = const., and the steady-state deviation Xm-Xr in the balanced state is constant regardless of the steering load. Further, according to the equation (8), since the applied voltage at a certain deviation changes in proportion to the steering load, for example, when the road surface condition suddenly changes to a low μ, the steering load changes accordingly. Since the duty value decreases as the duty value of the applied voltage as the control amount V decreases, the rotation speed of the steering shaft motor 23 decreases and the steering speed decreases. By such an operation, even when the turning load suddenly decreases, the sudden turning can be prevented.

Next, a third embodiment will be described. The control method of the steering control unit 30 in the first and second embodiments can be applied to a four-wheel steering system of a type in which the front wheel steering mechanism and the rear wheel steering mechanism are not mechanically connected. In the present embodiment, as an example, a case where the present invention is applied to a steering position control of a steered wheel on a rear wheel side in a front wheel drive system will be described.

FIG. 6 schematically shows the configuration of a steering control device according to the third embodiment. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the master unit A, a steering shaft 12 and a front wheel-side steering shaft 17 are connected via a gear box 18.
Steering actuator 19 adjacent to gearbox 18
Thus, an electric power steering system that generates a steering assist force is configured. The slave section B constitutes a rear-wheel-side steering mechanism, and the rear-wheel-side steering shaft 22 is driven to be displaced in the axial direction by a steering shaft motor 23, and a current sensor 26 is provided.
And the detection result of the stroke sensor 25 is
Given to. In addition, the turning control unit 30 is provided with the vehicle speed S detected by the vehicle speed sensor 15 and the actual steering position θr detected by the steering angle sensor 13.

The control block diagram of the turning control unit 30 is the same as that of FIG. 3 described above, but the target turning position calculating unit 31 calculates the target turning position of the turning wheel 21 on the rear wheel side. On this occasion,
The target steered position calculating unit 31 includes a two-dimensional map that can obtain the target steered position Xm of the steered wheel 21 on the rear wheel side from the values of the actual steering position θr and the vehicle speed S. Based on the values of the actual steering position θr and the vehicle speed S, the target steering position Xm of the rear-wheel steered wheels is searched on a map. A stroke sensor 25 provided on the steering shaft 22 on the rear wheel side is provided.
(Xm-X)
r) is given to the applied voltage calculation unit 33.

As described above, the load calculating section 32 obtains the steering load applied to the rear wheel-side steering shaft 22 from the detection result Is of the current sensor 26 by the above equation (2), and calculates the calculation result. The voltage is applied to the applied voltage calculator 33.

The applied voltage calculation unit 33 calculates the applied voltage to be applied to the rear wheel-side steering shaft motor by the above-mentioned equation (3) or (8).
The calculation is performed using the equation, and the control amount V obtained as a result of the calculation is applied to the rear-wheel-side steered shaft motor 23.

As described above, the control method of the steering control unit 30 in the first and second embodiments can be applied to the steering control on the rear wheel side in the four-wheel steering system. In this case, Thus, it is possible to perform the turning control according to the turning load on the rear wheel.

Next, as a fourth embodiment, the yaw rate control in a four-wheel steering system of a type in which the front wheel steering mechanism and the rear wheel steering mechanism are not mechanically connected,
A case where the control method adopted in the first embodiment is applied will be described.

FIG. 7 schematically shows the configuration of a steering control device according to the fourth embodiment. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the master unit A, the steering shaft 12 and the front wheel-side steering shaft 17 are connected via a gear box 18.
Steering actuator 19 adjacent to gearbox 18
Thus, an electric power steering system that generates a steering assist force is configured. The slave section B constitutes a rear-wheel-side steering mechanism, and drives a rear-wheel-side steering shaft 22 by a steering shaft motor 23. The current flowing through the steering shaft motor 23 is detected by the current sensor 26, and the detection result Is is given to the yaw rate control unit 50. Yaw rate control unit 5
0, the vehicle speed S detected by the vehicle speed sensor 15,
The actual yaw rate γr detected by the yaw rate sensor 16 is given. The yaw rate control unit 50 controls the steered position of the steered wheel 21 on the rear wheel side based on these detection results, thereby performing yaw rate control for generating a yaw rate corresponding to the actual steering position θr. .

As shown in the control block diagram of FIG. 8, the yaw rate controller 50 includes a target yaw rate calculator 51, a load calculator 52, and an applied voltage calculator 53. The target yaw rate calculation unit 51 has a two-dimensional map from which the target yaw rate γm can be obtained from the values of the actual steering position θr and the vehicle speed S, and the actual steering position θ detected by the steering angle sensor 13.
r and the vehicle speed S detected by the vehicle speed sensor 15,
A map search is performed for the target yaw rate γm. Then, a deviation (γm−γr) from the actual yaw rate γr, which is a detection result of the yaw rate sensor 16, is given to the applied voltage calculation unit 53.

As in the first embodiment, the load calculating section 52 obtains the steering load on the rear wheel from the detection result Is of the current sensor 26 by the above equation (2), and calculates the calculation result by the applied voltage. It is provided to the arithmetic unit 53.

The applied voltage calculation unit 53 employs a control method for setting the deviation between the target yaw rate γm and the actual yaw rate γr to zero when the steering control system goes through a transient state to a steady state. On the basis of the calculation results of the yaw rate calculation unit 51 and the load calculation unit 52, a control amount (steering control amount) V indicating the Duty value of the applied voltage applied to the turning shaft motor 23.
Is calculated based on the following equation (9). In addition,
Vs in the equation (9) is calculated from the above equation (4).

V = Kp7 · (γm−γr) + Vs (9) The yaw rate control unit 50 calculates the control amount V applied to the rear-wheel steering shaft motor 23 in this manner. By adopting a simple control method, control can be performed with the same gain even when the vehicle speed, the steering amount, the road surface condition, the tire condition, the number of occupants, and the like that affect the steering load change. In addition, since a characteristic that a large current flows at the time of starting, which is a starting characteristic of the motor, can be used, a response delay can be sufficiently suppressed.

Next, a fifth embodiment will be described. In the fifth embodiment, in the yaw rate control unit 50, when the turning control system is in a steady state after a transient state, a control is performed to leave a predetermined steady state deviation as a deviation between the target yaw rate γm and the actual yaw rate γr. The method is adopted.
In this case, the control block diagram is the same as that of FIG.
On the basis of the calculation result of 1 and the load calculation unit 52, a control amount (steering control amount) V indicating the Duty value of the applied voltage applied to the rear wheel-side steering shaft motor 23 is calculated by the following equation (10). It is calculated based on.

V = Kp8 · Ts · (γm−γr) (10) In the equation (10), Kp8 is a proportional gain represented by a predetermined constant, and is calculated as Kp8 · (γm−γr). The amount is corrected according to the steering load Ts calculated by the load calculation unit 52. By adopting such an arithmetic expression, the target yaw rate γ can be changed according to the magnitude of the steering load.
The magnitude of the steady-state deviation can be kept constant irrespective of the magnitude of the steering load, without the disadvantage that the magnitude of the steady-state deviation between m and the actual yaw rate γr changes.

In each of the embodiments described above, an example is shown in which the current sensor 26 is provided to detect the load state of the steered shaft motor 23. However, for example, the rotational speed of the steered shaft motor 23 is controlled by a rotational speed sensor. The load state of the steered shaft motor 23 may be detected based on the detected rotation speed and the known applied voltage value.

Further, in each embodiment, an example is shown in which the load calculation units 32, 42, and 52 are separately provided for each embodiment. However, one load calculation unit is used, and each control unit in each embodiment includes: Alternatively, a configuration may be adopted in which a predetermined calculation is performed using the calculation result of the load calculation unit.

Further, in each embodiment, the steering shaft motor 1
Although the DC motor 4 and the steering shaft motor 23 are exemplified as DC motors, other motors other than DC motors can be used. In this case, too, depending on the characteristics of the motor used, the applied voltage value, current value, The load state of the motor may be detected from the number of revolutions and the like, and the steering load may be calculated based on the detection result.

[0067]

As described above, according to the steering control device of the present invention, since the steering load calculating means for calculating the steering load based on the load state of the steering driving means is provided,
It is possible to detect a steering load without providing an axial force sensor as in the related art. In addition, since the steering driving means is usually provided at an immovable portion, it is possible to easily perform the wiring for detecting the steering load and obtain sufficient durability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a steering control device according to a first embodiment.

FIG. 2 is a graph showing rotation speed-load characteristics and current-load characteristics, which are basic characteristics of a DC motor.

FIG. 3 is a control block diagram of a steering control unit according to the first embodiment.

4A is a graph showing a relationship between a rotation speed and a load with respect to an applied voltage value, and FIG. 4B is a graph showing a relationship between a steering position, a rotation speed, a load torque, a current, and an applied voltage in the steering control. It is a graph which shows a transition.

FIG. 5 is a control block diagram of a reaction force control unit.

FIG. 6 is a configuration diagram schematically showing a steering control device according to a third embodiment.

FIG. 7 is a configuration diagram schematically showing a steering control device according to a fourth embodiment.

FIG. 8 is a control block diagram of a yaw rate control unit according to a fourth embodiment.

[Explanation of symbols]

A: Master unit, B: Slave unit, C: Control unit, 11: Steering handle, 12: Steering axis, 13: Steering angle sensor, 14
... Steering shaft motor (reaction force applying means), 15 ... Vehicle speed sensor,
16: yaw rate sensor, 22: steering shaft (steering means),
Reference numeral 23: turning shaft motor (turning driving means), 30: turning control unit, 32: load calculating unit (turning load calculating means), 33: applied voltage calculating unit (turning control amount calculating means), 40 ... Reaction force control unit, 42: load calculation unit (steering load calculation unit), 43: applied voltage calculation unit (reaction force control amount calculation unit), 50: yaw rate control unit, 52: load calculation unit (steering load calculation unit) ), 5
3. Applied voltage calculator (turning control amount calculator).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 119: 00 121: 00 137: 00

Claims (6)

[Claims] 1. A steering control device for steering a steered wheel in conjunction with a steering wheel, wherein the steering device is mechanically separated from the steering wheel and is connected to the steered wheel; A steering control device comprising: a steering drive unit; and a steering load calculation unit that calculates a steering load based on a load state of the steering drive unit. 2. A turning control amount calculating means for calculating a turning control amount to be applied to the turning drive means based on a deviation between a target turning position of a turning wheel and an actual turning position and the turning load. The steering control device according to claim 1 provided with. 3. A steering control amount to be applied to the steering drive means is calculated based on a deviation between a target steered position of the steered wheels and an actual steered position, and the calculated steering control amount is calculated based on the deviation. 2. The steering control device according to claim 1, further comprising a steering control amount calculating unit that corrects based on a steering load. 4. A reaction force applying means for applying a steering reaction force to a steering wheel, and a reaction force applying means for applying the steering reaction force to the steering wheel based on a deviation between a target steering position and an actual steering position of the steering wheel and the turning load. 2. The steering control device according to claim 1, further comprising a reaction force control amount calculating means for calculating the reaction force control amount. 5. The steering system according to claim 1, further comprising: a steering control amount calculating unit that calculates a steering control amount to be applied to the steering driving unit based on a deviation between a target yaw rate and an actual yaw rate and the steering load. Control device. 6. A steering control amount to be applied to the steering drive means is calculated based on a deviation between a target yaw rate and an actual yaw rate, and the calculated steering control amount is corrected based on the steering load. 2. A steering control amount calculating means, comprising:
The steering control device according to any one of the preceding claims.