JPH0686218B2 - Steering reaction force control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering reaction force control device that controls a steering reaction force of a steering wheel in response to a turning motion of a vehicle.

(Prior Art) In recent years, many vehicles have a power steering device mounted on a steering device. This power steering device works to assist steering by adding an assist torque to a steering force of a steering wheel by a driver by a hydraulic booster or the like.

Further, as the power steering device, in addition to the conventional hydraulic power steering device, for example, an electric power steering device as disclosed in JP-A-59-63264 has been proposed.

This electric power steering device has a structure as shown in FIG.

A first steering shaft 2 is connected to the steering handle 1, and the first steering shaft 2 is connected to a second steering shaft 5 via a first universal joint 4.

A DC servomotor DM is attached to the second steering shaft 5 via a speed reducer 9. The torque applied to the steering wheel 1 (hereinafter referred to as "steering wheel steering torque") T _C is applied to the second steering shaft 5.
A steering torque sensor 8 for detecting the is attached.

A third steering shaft 7 is connected to the second steering shaft 5 via a second universal joint 6. The tip of the third steering shaft 7 is a rack and pinion type gear box 3.
It is connected to the.

The inclination γ between the first steering shaft 2 and the second steering shaft 5 and the inclination γ between the second steering shaft 5 and the third steering shaft 7 are set to be equal.

The gear box 3 is connected to a tie rod 17, and the tie rod 17 is connected to a knuckle arm 16 of a wheel 12.

Then, the controller 10 detects the steering torque detection value T _{C of the} steering wheel 1 detected by the steering torque sensor 8.
Is inputted as an electric signal, and the drive current I _P of the servo motor DM is controlled so as to generate the assist torque T _PS corresponding to the detected value T _C of the steering torque.

(Problems to be Solved by the Invention) However, in the conventional power steering system as described above, since it is mainly intended to reduce the burden of the steering force of the steering wheel for the driver, the turning operation of the vehicle is avoided. For the driver who obtains information from the steering reaction force of the steering wheel, there is a feeling of dissatisfaction that the driver cannot obtain sufficient information.

That is, in general, a driver feels a steering reaction force when steering a steering wheel, and also feels a change in a vehicle driving state amount such as a yaw rate or lateral acceleration, and based on these feelings, the driver can easily drive. Is being evaluated.

In addition, the driver generally performs a driving operation that emphasizes the yaw rate of the vehicle in the medium and low speed range and lateral acceleration in the high speed range.

As described above, although the driver needs the turning motion information such as the yaw rate and the lateral acceleration, the information is inevitably dependent on the driver's own sense.

(Means for Solving Problems) In order to solve the above problems, the present invention includes means shown in FIG.

The motion state quantity estimating means 100 estimates at least one motion state quantity exhibited by the vehicle model at the time of steering, based on a vehicle model 103 that mathematically models a vehicle having desired motion performance.

The steering reaction force target value determining means 101 is a motion state quantity estimating means 100.
The target value _C of the steering reaction force of the steering wheel 109 is determined on the basis of the estimated value M ^* of the motion state quantity estimated in.

The road surface input torque estimating means 102 estimates the road surface input torque input from the road surface to the steering system using the vehicle model 103.

The assist torque ratio determining means 104 subtracts the steering reaction force target value _C from the torque transmitted to the steering wheel 109 associated with the road surface input torque T _L ^* estimated by the road surface input torque estimating means 102, and calculates the difference value. , The power steering device 108 for obtaining the steering reaction force target value _C
This assist torque calculation value is obtained as the calculation value of the assist torque to be provided by the vehicle, and the assist torque ratio K _PS , which is the ratio of the assist torque calculation value to the steering reaction force target value _C , is determined.

The assist torque target value determining means 105 multiplies the assist torque ratio K _PS by the detected value T _C of the steering torque generated in the steering wheel 109 detected by the steering torque detecting means 106 to obtain the power steering device. To determine the assist torque.

The drive control means 107 sets the power steering device according to the target value _PS of the determined assist torque.
Control the drive of 108.

(Operation) According to the present invention, the steering wheel 109 is operated according to the estimated value M ^* of the motion state quantity estimated by the motion state quantity estimating means 100.
By adjusting the steering reaction force of (1), it becomes possible to generate the turning motion information such as the yaw rate and the lateral acceleration in the steering handle operating system as described above, and the maneuverability can be improved.

Further, since the motion state quantity of the vehicle is obtained by estimation using the above vehicle model, it is possible to obtain a stable motion state quantity with less error than in the case of actually measuring the motion state quantity. . In particular, since it is difficult to measure the motion state quantity during the turning transient motion of the vehicle, it is effective to use the vehicle model as in the present invention.

By the way, in order to adjust the steering reaction force, this steering reaction force, that is, the steering torque T generated in the steering wheel 106 is generated.
_C is detected by the torque sensor, and the detected steering torque value T _C
Is generally considered to be a servo system forming a feedback loop that drives and controls the power steering device 105 so as to match the steering reaction force target value _C.

However, in the case of performing such feedback loop control, since the power steering device 108 and the steering system are included in the loop, the loop becomes large, and
As described below, the control of the servo control becomes unstable and the steering reaction force control does not match the actual vehicle behavior due to the influence of the change of the running condition such as the change of the road surface friction coefficient μ and the change of the aerodynamic force.

That is, the motion state quantity estimated value M ^* and the steering reaction force target value _C based on this estimated value M ^*
Assuming that the vehicle is traveling on a road, the determination is made based on the gain and dynamic characteristics of the controlled object (vehicle and its steering system) at this time, but the traveling condition cannot be constant and changes every moment. The case where the road surface μ is significantly different from the above assumed μ road will be described as an example. As described above, the steering torque detection value T _C
In the feedback control that only makes the steering reaction force target value _C coincide with the steering reaction force target value _C , hunting or the like of the control occurs due to the change of the gain or dynamic characteristics of the control target due to the road surface μ, and the steering torque T _C is increased or decreased to the target value _C It vibrates forever, causing a situation where the target value is not met. This tendency is particularly remarkable in the vicinity of the limit region where the linearity of the vehicle motion characteristics is lost.

Further, even if the steering torque T _C can be made to match the target value _C , the steering reaction force target value _C is determined based on the vehicle motion state amount M ^* estimated on the assumption of a certain running condition. Since the change does not follow the change of the running condition, the feedback control of only matching the steering torque T _C with the target value _C does not reflect the change of the running condition in the controlled steering torque. However, it is impossible to accurately sense from the steering operation system the actual amount of motion state of the vehicle, which changes depending on the driving conditions. For example, assuming that the assumed traveling condition is a dry high μ road and the vehicle motion state quantity M ^* is estimated based on this to determine the steering reaction force target value _C , the steering torque T _C is simply made to match the target value _C. In feedback control, even if the actual road is a low μ road, steering reaction force control corresponding to the vehicle motion state quantity that occurs on a dry high μ road will be performed, and the vehicle motion state quantity on the current low μ road will be controlled. You can't feel it from the steering operation system, which is uncomfortable.

In the present invention, the steering reaction force target value _C obtained as described above is used as it is, but in determining the assist torque target value based on this, the detected value T _C of the steering torque that changes according to the traveling condition is used. By making the above determination so that the assist torque target value will eventually generate a steering reaction force corresponding to the actual vehicle motion state quantity, despite the change in the running condition, Avoid problems with feedback control.

Road surface torque estimating means 102, assist torque ratio determining means 104, assist torque target value determining means 10 provided for that purpose.
5. Of the steering torque detecting means 106, the means 102 estimates the road surface input torque T _L ^* from the vehicle model 103, and the means 104 steers from the torque transmitted to the steering wheel 109 according to the road surface input torque estimated value T _L ^*. This reaction torque target value _C is subtracted, and the difference value is used as the calculated value of the assist torque to be provided by the power steering device 108 in order to obtain the steering reaction force target value _C. Steering reaction force target value _{C of} assist torque calculation value
The assist torque ratio K _PS , which is the ratio to The means 105 then multiplies the assist torque ratio K _PS by the steering torque T _C detected by the means 106 to obtain the assist torque target value.
After determining _PS , the drive control means 107 supplies a drive signal uniquely corresponding to the assist torque target value _PS to the power steering device 108 to power assist the steering handle 109.

It should be noted that, when the steering torque value T _C detected by the means 106 is used in the above-mentioned control, instead of using the steering torque detection value T _C to match the steering reaction force target value _C , the assist torque target value is not used. _{In order} to reflect the change in the driving condition in _PS as described later, the assist torque target value _PS does not correspond only to the steering reaction force target value _C, but is matched with the actual vehicle operating state amount according to the change in the driving condition. Used. Therefore, when the steering torque detection value T _C is used, the above control is feedforward control instead of feedback control, and the control system becomes a large-scale one including a steering system like a feedback loop. In addition, the control does not become unstable due to changes in running conditions.

According to the drive control of the power steering device 108 described above, when determining the assist torque target value _PS for steering reaction force control, the steering reaction force corresponding to the vehicle motion state quantity estimation amount M ^* under the specific traveling condition is temporarily determined. The assist torque ratio K _PS for achieving the target value _C is obtained, and the assist torque target value _PS is determined by multiplying the assist torque ratio K _PS by the steering torque detection value T _C that changes according to changes in the driving conditions. The target value does not simply correspond to the steering reaction force target value _C , and the steering reaction force corresponding to the actual vehicle operating state quantity is generated despite the change in the traveling condition. Therefore, the steering reaction force control that always matches the actual vehicle driving state quantity that changes according to the running conditions is always performed, and the driver can always accurately sense the actual vehicle driving state quantity from the steering reaction force. it can.

(Embodiment) FIG. 2 shows the configuration of an embodiment of the present invention. In the figure, the same components as those of the conventional example shown in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, the steering reaction force of the steering wheel 1 is adjusted according to the lateral acceleration α of the vehicle.

It is the controller 30 composed of a microcomputer or other electric circuit that controls the steering reaction force.

The controller 30 includes a detected value T _C of the steering torque of the steering wheel 1 detected by a steering torque sensor 8 corresponding to steering torque detection means mounted on the second steering shaft 5, and the first steering shaft 2. The detected value θ _S of the steering angle of the steering wheel 1 detected by the steering angle sensor 21 attached to the vehicle and the detected value V of the vehicle speed detected by the vehicle speed sensor 22 are input.

Then, the controller 30 controls the input information T _C , θ _S , V
Based on the above, a predetermined calculation is performed to output the driving current I _P of the servo motor DM required to generate the steering reaction force according to the lateral acceleration α of the vehicle.

The controller 30 is functionally configured as shown in FIG.

The motion state quantity estimating unit 31 corresponds to a motion state quantity estimating means, and is provided with a numerical model (hereinafter, referred to as “vehicle model”) for simulating the motion state of the own vehicle. When θ _S and the vehicle speed V are given, the lateral acceleration exhibited by the vehicle model is estimated under certain traveling conditions. The estimated lateral acceleration value α ^* estimated at this time is a value corresponding to the lateral acceleration α actually occurring in the vehicle.

The motion state quantity estimating unit 31 obtains the lateral acceleration estimated value α ^* by the following calculation.

Vy ＝ ∫ydt… (2) C _F = eK _F・ β _F … (5) C _R ＝ K _R・ β _R … (6) α ^* = (2C _F + 2C _R ) / M (8) here, Vy: lateral velocity of vehicle model y: time derivative of lateral velocity of vehicle model L _F : distance between front axis and center of gravity of vehicle model L _R : distance between rear axis and center of gravity of vehicle model β _F : vehicle Model front wheel side slip angle β _R : Vehicle model rear wheel side slip angle C _F : Vehicle model front wheel cornering force C _R : Vehicle model rear wheel cornering force eK _F : Vehicle model front wheel equivalent cornering power K _R : Vehicle Model rear wheel cornering power I _Z : Vehicle model yaw inertia M: Vehicle model body mass N: Vehicle model steering gear ratio.

Further, in the motion state quantity estimating unit 31, the front wheel cornering force estimation amount C _F ^* given to the assist torque ratio determining unit 33 is given ^.
Ask for. This is the formula (7), obtained by clearing a rear wheel cornering off Orth C _R (8). That is, However, L is the wheelbase of the vehicle model, and L = L _F
+ L _R.

The lateral acceleration estimated value α ^* thus obtained is given to the steering reaction force target value determination unit 32 as the steering reaction force target value determination means. The steering reaction force target value determination unit 32 multiplies the given lateral acceleration α ^* by a preset proportional constant K, and sets this value as the steering reaction force target value _C. That is, _C = Kα ^* (11). This proportionality constant K is calculated in advance by experiments and calculations.
This value is set in the controller 30 by obtaining a value such that the correlation between the lateral acceleration and the steering reaction force is most appropriate.

The assist torque ratio determining unit 33 corresponds to assist torque ratio determining means, and calculates the assist torque ratio K from the steering reaction force target value _C and the front wheel cornering force estimated value _CF ^*.
_Ask for _PS . This assist torque ratio K _PS is calculated by the following arithmetic expression.

Here, T _PS ^* is the assist torque calculation unit that should be provided by the power steering system shown in FIG. 2 in order to achieve the steering reaction force target value _C.
PS ^* is calculated by the following formula, where ξ is the trail of the vehicle specifications and N is the steering gear ratio.

Here, the reason why the assist torque calculation value T _PS ^* is obtained by the above equation will be described. First, considering the balance model of the steering system, this is the steering torque T input from the steering wheel 1 to the column system as shown in FIG. 4 when the viscosity term and the inertia term around the kingpin axis are ignored.
_C (the driver feels this as steering reaction force and obtains turning motion information), the power steering assist torque T _PS that is also input to the column system, and the cornering force of the front wheels 12 caused by the turning of the vehicle. steering system from併I front wheel 12 to C _F represented as a balance system of the road surface input torque T _R to be inputted to the (rack), if expressed by the formula, the steering gear ratio is assumed to be N, as follows become.

By the way, in this example, T _C in the above equation is set as the steering reaction force target value _C , and T _PS is also the assist torque calculation value T _{PS to} be obtained in order to achieve the steering reaction force target value _C. ^Since it can be replaced with ^* , With the calculation of, the assist torque calculation value T _PS ^* for achieving the steering reaction force target value _C can be calculated.

However, it is almost difficult to actually measure the road surface input torque T _R in the above equation, and the assist torque calculation value T _PS ^* cannot be calculated with the above equation.

Meanwhile, the road surface input torque T _R are known to be expressed by T _R = 2ξC _F from the front wheel cornering force C _F, also the front wheel cornering force C _F is the the estimating unit 31 of FIG. 3 (10) from being calculated as the estimated value C _F ^* by calculating the road surface input torque T _R is the road surface input torque estimation value
T _L ^* as ^{_{T R = T L * = 2ξC}} F * ... can be obtained by calculation of (15). Considering this situation (1
By substituting the equation (5) into the equation (14), the above equation (13) is obtained,
As described above, it was proved that the assist torque calculation value T _PS ^* can be obtained by the calculation of the equation (13). here,
The first term on the right side of the equation (13) represents the torque transmitted to the steering wheel due to the road surface input torque.

By substituting the equation (13) into T _PS ^* of the equation (12), the equation (12) for obtaining the assist torque ratio K _PS is obtained. Therefore, the assist torque ratio determination unit 33 first determines (15) The road surface input torque T _R is estimated by the formula, and the assist torque calculation value T _PS ^* is calculated by the calculation of the formula (14) using the estimated value T _L ^* , that is, the calculation of the formula (13). Ratio of T _PS ^* and steering reaction force target value _C , that is, assist torque ratio K
_PS is _calculated as in equation (12).

Therefore, the assist torque ratio determination unit 33 also serves as a road surface input torque estimation unit in addition to the assist torque ratio determination unit as described above.

The assist torque ratio K _PS thus obtained is multiplied by the steering torque detection value T _C in the assist torque determination unit 34 that is the assist torque target value determination means to determine the assist torque target value _PS . This assist torque target value _PS
Is sent to the motor control unit 35 as drive control means.

The assist torque determination unit 34, when the actual motion characteristics of the vehicle change due to traveling under a condition different from the traveling condition such as the road surface μ determined when obtaining the steering reaction force target value _C using the vehicle model. , Assist torque target value _PS
Is determined as follows.

That is, the assist torque ratio K _PS, as shown above formula (12) is a value determined by the estimated value T _L ^* City of steering reaction force target value _C and the road surface input torque, these _C and T _L ^* is Both are estimated values obtained using a vehicle model traveling under specific traveling conditions, and K _PS is an assist torque ratio determined based on these estimated values. Therefore, in addition to equation (12), Information about some actual changes in vehicle motion characteristics according to changes in conditions must be included. Therefore, the assist torque determination unit 34 determines the actual detected value T _C of the steering torque detected by the steering torque sensor 8 because the change in the traveling condition (the actual vehicle motion state amount) appears as the change in the steering torque. The assist torque target value _PS determined by the above equation (12) is multiplied by the following equation. _PS = K _PS · T _C (16) The assist torque target value _PS thus determined is input to the motor control unit 35, is amplified by a predetermined gain K _I , and becomes the current target value _P , and further the current controller 36. Is converted into the drive current I _P of the servo motor DM. This drive current
I _P is controlled to a current value required to generate an assist torque T _PS equal to the assist torque target value _PS .

By the way, the assist torque target value _PS
In determining the steering reaction force target value _C , the assist torque ratio K _PS corresponding to the steering reaction force target value _C is once obtained, and this value is multiplied by the steering torque detection value T _C to determine the assist torque target value _{PS. Since} the vehicle is traveling under a condition different from the traveling condition specified when determining _C , the actual vehicle motion state quantity and the estimated vehicle motion state quantity (lateral acceleration) α ^* used in determining the steering reaction force target value _C Even if there is a difference,
The assist torque target value is determined by the detected steering torque value T _C, which indicates the difference in the driving conditions (difference in the vehicle motion state amount).
_{The PS} is made to generate a steering reaction force corresponding to the actual vehicle motion state quantity. Therefore, the driver can accurately sense the actual vehicle driving state amount from the steering reaction force, and the steering reaction force generated by the control that simply matches the steering torque T _C with the steering reaction force target value _C A mismatch with the actual amount of motion of the vehicle can be avoided.

Since the above control is feedforward control, when the steering torque detection value T _C is used for the above purpose, the 雖 also does not have a large steering loop due to the steering system entering the control loop. Control instability such as hunting does not occur due to any change in running conditions.

The motion state quantity estimating unit 31 and the steering reaction force target value determining unit
32, the assist torque ratio determination unit 33, and the assist torque determination unit 34 can be configured by an arithmetic circuit using a microcomputer, and in this case, according to the flow chart shown in FIG. The above calculation is performed.

In Step 42, the calculation performed by the motion state quantity estimating unit 31 is executed, in Step 43, the calculation performed by the steering reaction force target value determining unit 32 is executed, and in Steps 44 and 45,
The calculation performed by the assist torque ratio determination unit 33 is executed, and in step 47, the calculation performed by the assist torque determination unit 34 is executed.

In the above-described embodiment, the present invention is applied to the vehicle equipped with the electric power steering. However, the present invention can be similarly applied to the vehicle equipped with the hydraulic power steering.

Further, in the above-described embodiment, an example is shown in which the steering reaction force is adjusted in accordance with the estimated lateral acceleration value α ^* obtained using the vehicle model. However, the present invention is not limited to this, and other motions are also possible. State quantity,
For example, the yaw rate, the lateral speed, and the like may be estimated using a vehicle model, and the steering reaction force may be adjusted according to the estimated value.

Further, not only the steering reaction force is associated with one motion state quantity, but the steering reaction force can be adjusted in association with the estimated value of two or more motion state quantities. In this case, weighting is applied to the estimated value of the motion state quantity obtained by two or more,
It is also possible to increase the weight of the estimated value of the motion state quantity for which importance should be attached to the correspondence with the steering reaction force.

(Effects of the Invention) As described in detail above, the present invention uses a vehicle model for estimating vehicle motion to estimate at least one motion state quantity exhibited by the vehicle model during steering, and at the same time, estimates this motion state quantity. By adjusting the steering reaction force of the steering wheel according to the estimated value of the steering wheel, it becomes possible to generate turning motion information such as yaw rate and lateral acceleration in the steering wheel operation system, improving maneuverability. It is possible to let

Further, by using the vehicle model to obtain the motion state quantity of the vehicle by estimation, it is possible to obtain a stable motion state quantity with less error than in the case of actually measuring the motion state quantity. . In particular, since it is difficult to measure the motion state quantity during the turning transient motion of the vehicle, it is effective to use the vehicle model as in the present invention.

Further, in determining the assist torque target value for steering reaction force control, the present invention does not suddenly determine the assist torque target value to a value corresponding to the steering reaction force target value, but instead determines the steering reaction force target value once. Since the corresponding assist torque ratio is calculated and the steering torque detection value is multiplied to calculate the assist torque target value, feedforward control with a small control loop and without causing control instability such as hunting is performed. The actual vehicle motion state quantity is the estimated value of the vehicle driving state quantity used when determining the steering reaction force target value because the vehicle is running while the traveling conditions differ from those specified when determining the steering reaction force target value. Even if it is different from this, the assist torque target value in the detected steering torque value causes the steering reaction force corresponding to the actual vehicle operating state quantity. Becomes to be such things, it is possible to eliminate the so-called modeling error.

Therefore, even while traveling under conditions different from the traveling conditions such as the road surface μ specified when estimating the vehicle operating state amount using the vehicle model and determining the steering reaction force target value corresponding thereto,
The steering reaction force can be made to correspond to the actual vehicle driving state quantity, and the driver can accurately sense the actual behavior of the vehicle from the steering reaction force under any driving condition, and the discomfort can be eliminated. .

[Brief description of drawings]

1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the controller in FIG. 2, and FIG. 4 is a model of a steering system. And a road surface input torque. FIG. 5 is a flow chart showing processing executed when the controller in FIG. 2 is configured by using a microcomputer, and FIG. 6 is a conventional electric power steering apparatus. It is a block diagram. 100 ... Motion state quantity estimating means 101 ... Steering reaction force target value determining means 102 ... Road surface input torque estimating means 103 ... Vehicle model 104 ... Assist torque ratio determining means 105 ... Assist torque target value determining means 106 ... Steering torque detecting means 107 Drive control means 108 Power steering device 109 Steering handle 1 Steering handle 2 First steering shaft 5 Second steering shaft 8 Steering torque sensor 9 ... Reducer 21 ... Steering angle sensor, 22 ... Vehicle speed sensor 30 ... Controller, 31 ... Motion state quantity estimation unit 32 ... Steering reaction force target value determination unit 33 ... Assist torque ratio determination unit 34 ... ... assist torque determining section 35 ...... motor control unit T _C ...... steering torque, _{C ......} steering reaction force target value theta _{S ......} steering angle, V ...... vehicle speed alpha ^{* ......} lateral acceleration estimated value, T _PS ...... Shisutotoruku T _L ^{* ......} road surface input torque estimation value C _F ^{* ......} front cornering off Orth estimate _PS ...... assist torque target value K _PS ...... assist torque ratio

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B62D 121: 00

Claims (1)

[Claims] 1. A steering reaction force control device for controlling a steering reaction force of a steering wheel of a vehicle equipped with a power steering device, wherein the steering reaction force control device controls the steering reaction force of a vehicle having a desired motion performance based on a vehicle model which is mathematically modeled. A motion state quantity estimating means for estimating at least one motion state quantity presented by the vehicle model, and a target value of the steering reaction force of the steering wheel based on the estimated value of the motion state quantity estimated by the motion state quantity estimating means. Steering reaction force target value deciding means for deciding, road surface input torque estimating means for estimating a road surface input torque input to the steering system from the road surface using the vehicle model, and steering for detecting a steering torque generated in the steering wheel. The torque detection means and the steering torque based on the torque transmitted to the steering wheel due to the road surface input torque. The difference value obtained by subtracting the force target value,
An assist torque ratio determination unit that determines the assist torque calculation value as a calculation value of the assist torque by the power steering device, and determines an assist torque ratio that is a ratio of the assist torque calculation value to the steering reaction force target value. Assist torque target value determining means for determining a target value of assist torque by the power steering device by multiplying the detected value of steering torque detected by the steering torque detecting means by the assist torque ratio; A steering reaction force control device, comprising: drive control means for controlling the drive of the power steering device according to the target value of the assist torque determined by the value determination means.