JP5543906B2 - Vehicle power steering control device - Google Patents

Description

  The present invention relates to a vehicle power steering control device that appropriately controls an assist torque of a steering torque of a driver.

  In recent years, various power steering control devices for appropriately controlling the assist torque of a driver's steering torque have been proposed for vehicles. For example, in Japanese Patent Laid-Open No. 2008-87763 (hereinafter referred to as Patent Document 1), in a power steering control device that sets an assist torque in accordance with a steering torque and a vehicle speed, a yaw rate deviation or a lateral acceleration deviation is not stable in a vehicle. Or increase in response to an increase in oversteer) to reduce the reaction feedback due to the road surface felt by the driver before the actual vehicle stability is lost, A technique of an electric power steering device that generates a correction torque to be added to the assist torque based on the yaw rate deviation or the lateral acceleration deviation so that the correction can be appropriately made at the time is disclosed.

JP 2008-87763 A

  In general, the driver steers while feeding back the rudder force, and feels the grip state of the steered wheel as rudder force information with the rudder force, and as compared to the region of understeer or oversteer as disclosed in Patent Document 1 described above. If the driver can operate in a wide area, the driver can perform an appropriate operation with peace of mind. However, in general steering, since the self-aligning torque is saturated before the steering wheel grip is saturated, there is a problem that it is difficult to sense the steering wheel grip state with the steering force in a wide driving range.

  The present invention has been made in view of the above circumstances, and the power steering of a vehicle that allows a driver to perform appropriate driving with peace of mind while sensing the grip state of the steered wheels as steering information in a wide driving area. The object is to provide a control device.

According to one aspect of the vehicle power steering control device of the present invention, there is provided basic assist torque setting means for setting an assist torque of a steering torque as a basic assist torque in accordance with a driving state of the vehicle, and a current steering state of the vehicle is a steering speed. setting the driver and the determining feedback steering judging means are steered by feeding back the steering force, the grip condition of the steering wheel advance when in the steering area has been set in advance in accordance with the absolute value and the vehicle speed A grip state determining means for determining whether or not the vehicle is in a non-linear region and a feedback steering determining means for determining that the steering force is fed back and steering is performed, and the grip state determining means determines that the grip state of the steered wheel is An assist torque that corrects the basic assist torque in a direction to increase when it is determined that the current position is in a preset non-linear region. A correction unit, and a steering control means for driving and controlling the actuator for assisting the steering torque corrected basic assist torque by the assist torque correcting means.

  According to the power steering control device for a vehicle according to the present invention, it is possible for the driver to perform an appropriate driving with peace of mind while sensing the grip state of the steered wheels as steering information in a wide driving area.

1 is a configuration explanatory diagram of a vehicle steering system according to an embodiment of the present invention. FIG. It is a flowchart of the power steering control program which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the characteristic of the basic assist torque which concerns on one Embodiment of this invention. It is explanatory drawing of the feedback steering area | region which concerns on one Embodiment of this invention. It is explanatory drawing of the assist torque correction gain which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes an electric power steering apparatus. In the electric power steering apparatus 1, a steering shaft 2 is rotatably supported on a vehicle body frame (not shown) via a steering column 3, and one end thereof is It extends to the driver's seat side, and the other end extends to the engine room side. A steering wheel 4 is fixed to an end portion of the steering shaft 2 on the driver's seat side, and a pinion shaft 5 is connected to an end portion extending to the engine room side.

  A steering gear box 6 extending in the vehicle width direction is disposed in the engine room, and a rack shaft 7 is inserted into and supported by the steering gear box 6 so as to be reciprocally movable. A rack (not shown) formed on the rack shaft 7 is engaged with a pinion (not shown) formed on the pinion shaft 5 to form a rack and pinion type steering gear mechanism.

  The left and right ends of the rack shaft 7 protrude from the end of the steering gear box 6, and a front knuckle 9 is connected to the end via a tie rod 8. The front knuckle 9 rotatably supports left and right wheels 10L and 10R as steering wheels, and is supported by a vehicle body frame via a king pin (not shown) so as to be steerable.

  Accordingly, when the steering wheel 4 is operated and the steering shaft 2 and the pinion shaft 5 are rotated, the rack shaft 7 is moved in the left-right direction by the rotation of the pinion shaft 5, and the front knuckle 9 is moved to the king pin (not shown). ) And the left and right wheels 10L, 10R are steered in the left-right direction.

  An electric motor 12 is connected to the pinion shaft 5 via an assist transmission mechanism 11, and the electric motor 12 assists the steering torque applied to the steering wheel 4. The electric motor 12 is drive-controlled via a motor drive unit 21 with a control amount (assist torque Ta in the present embodiment) set by a steering control unit 20 described later. Note that the control amount may be a current value corresponding to the assist torque Ta.

  The steering control unit 20 includes a vehicle speed sensor 31 that detects the vehicle speed V, a handle angle sensor 32 that detects the steering wheel angle θH, a steering torque sensor 33 that detects the steering torque Ts applied to the steering wheel 4, and a lateral acceleration Gys. A lateral acceleration sensor 34 is connected.

  Then, the steering control unit 20 calculates the target lateral acceleration Gyt based on the vehicle motion model according to the steering wheel angle θH and the vehicle speed V, and the deviation (lateral acceleration deviation) ΔGy between the actual lateral acceleration Gys and the target lateral acceleration Gyt. Is calculated based on the absolute value | dθH / dt | of the steering speed and the vehicle speed V, and it is determined whether or not the current steering state is a state in which the driver is steering by feeding back the steering force. When it is determined that the vehicle is steered by feedback and the lateral acceleration deviation ΔGy is equal to or larger than a preset value CG, the basic assist torque Tb set based on the vehicle speed V and the steering torque Ts is increased. The corrected basic assist torque Tb is output to the motor drive unit 21 as a control amount (assist torque Ta). Thus, the steering control unit 20 is configured to have functions as basic assist torque setting means, feedback steering determination means, grip state determination means, assist torque correction means, and steering control means.

Next, power steering control executed by the steering control unit 20 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) 101, necessary parameters, that is, vehicle speed V, steering wheel angle θH, steering torque Ts, and lateral acceleration Gys are read.

  Next, the process proceeds to S102, and a basic assist torque Tb is set based on the vehicle speed V and the steering torque Ts with reference to a preset map (for example, shown in FIG. 3).

Next, the process proceeds to S103, and the target lateral acceleration Gyt based on the vehicle motion model is calculated by the following equation (1), for example.
Gyt = (1 / (1 + A · V ² )) · (V ² / B) · (θH / n) (1)
Here, A and B are parameters specific to the vehicle, and n is a steering gear ratio.

Next, proceeding to S104, the deviation (lateral acceleration deviation) ΔGy between the actual lateral acceleration Gys and the target lateral acceleration Gyt is calculated by the following equation (2).
ΔGy = Gyt−Gys (2)
Next, the process proceeds to S105, and a current steering is performed according to the absolute value | dθH / dt | of the steering speed and the vehicle speed V with reference to a map (for example, shown in FIG. 4) of the feedback steering area set in advance. It is determined whether or not the state is a state in which the driver is steering by feeding back the steering force.

  As shown in FIG. 4, in the feedback steering area, the driver feeds back the steering force in an extremely low speed area where the vehicle speed V is lower than LV and in an area where the absolute value | dθH / dt | of the steering speed is larger than LθH. It is set to the area that is not in operation.

  In addition, you may make it determine with the other method whether the driver is driving | running | feeding back steering force. For example, a special device such as a camera may be provided, and the determination may be made by comparing a driver model set in advance with a steering wheel angle, steering torque, course information, and the like.

  Then, when the process proceeds to S106, it is determined whether the result of the feedback determination process in S105 is execution of feedback steering. As a result of the determination in S106, if it is determined that the feedback steering is to be executed, the process proceeds to S107, and whether or not the lateral acceleration deviation ΔGy is equal to or larger than a preset value CG (ΔGy ≧ CG) set in advance by experiment, calculation, or the like. Determined.

  As a result of the determination in S107, if ΔGy ≧ CG and it is determined that the grip state of the steered wheel is in a non-linear region, the driver can feel the grip state of the steered wheel with the steering force when steering. In step S108, the assist torque correction gain Ga is set according to the lateral acceleration Gys and the vehicle speed V with reference to a preset map (for example, shown in FIG. 5). .

  As will be described later, the assist torque correction gain Ga is a gain for correcting the assist force to increase as the value increases. As shown in FIG. 5, in the region where the vehicle speed V is low, the assist force is increased. Since no increase correction is required, the value is set to approximately zero. In addition, in a high-speed region of a predetermined level or more, if the assist force is excessively increased, instability may occur on the contrary, and thus the increase of the assist force is suppressed.

Next, in S109, the assist torque correction amount ΔTa is calculated by the following equation (3).
ΔTa = Ga · ΔGy (3)
On the other hand, if it is determined in S106 that the feedback steering is not executed, or if it is determined in S107 that ΔGy <CG and the grip of the steered wheel has a margin, the process proceeds to S110. ΔTa = 0.

Then, after setting the assist torque correction amount ΔTa in S109 or S110, the process proceeds to S111, where the assist torque Ta is calculated by the following equation (4), and is output to the motor drive unit 21 to exit the program.
Ta = Tb + ΔTa (4)
As described above, according to the embodiment of the present invention, the target lateral acceleration Gyt is calculated based on the vehicle motion model according to the steering wheel angle θH and the vehicle speed V, and the deviation between the actual lateral acceleration Gys and the target lateral acceleration Gyt ( Lateral acceleration deviation) ΔGy is calculated, and it is determined whether or not the current steering state is a state in which the driver is steering by feeding back the steering force according to the absolute value | dθH / dt | of the steering speed and the vehicle speed V. When the driver determines that the steering force is fed back and the vehicle is steered, and the lateral acceleration deviation ΔGy is greater than or equal to a preset value CG, the basic setting is based on the vehicle speed V and the steering torque Ts. The assist torque Tb is corrected in the increasing direction. For this reason, it becomes possible for the driver to perform appropriate driving with peace of mind while sensing the grip state of the steered wheels as the steering force information in a wide driving region.

  That is, in general steering, since the self-aligning torque is saturated before the steering wheel grip is saturated, it is difficult to sense the steering wheel grip state with the steering force. On the other hand, a steering feeling with a sense of security can be obtained by increasing the assist force of the electric power steering in accordance with the grip saturation condition and extracting (lightening) the steering force. However, this is only when the driver is steering while feeding back the rudder force. When performing feed-forward steering, turning the steering wheel too much may disturb the behavior of the car and conversely reduce the sense of security. There is also.

  In the embodiment of the present invention, the assist torque Ta is calculated by adding the assist torque correction amount ΔTa to the basic assist torque Tb, but the correction of the basic assist torque Tb is performed in this way. For example, the correction may be made by multiplying the basic assist torque Tb by a correction coefficient.

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 4 Steering wheel 5 Pinion shaft 11 Assist transmission mechanism 12 Electric motor 20 Steering control part (Basic assist torque setting means, feedback steering determination means, grip state determination means, assist torque correction means, steering control means)
21 Motor drive unit 31 Vehicle speed sensor 32 Handle angle sensor 33 Steering torque sensor 34 Lateral acceleration sensor

Claims (4)

Basic assist torque setting means for setting the assist torque of the steering torque as the basic assist torque according to the driving state of the vehicle;
Steering state of the current vehicle, steering speed of the absolute value and the vehicle speed and determining feedback steering judging means and driver when in the steering region that is set in advance is steered by feeding back the steering force according to When,
Grip state determination means for determining whether the grip state of the steered wheel is in a preset non-linear region;
When the feedback steering determination means determines that the steering force is fed back and the steering state is determined and the grip state determination means determines that the grip state of the steered wheel is in a preset non-linear region, the basic assist torque Assist torque correction means for correcting in the increasing direction,
Steering control means for driving and controlling an actuator that assists the steering torque with the basic assist torque corrected by the assist torque correction means;
A vehicle power steering control device. The grip state determination means determines the grip state of the steered wheel when the deviation between the target lateral acceleration calculated based on the vehicle motion model according to the driving state of the vehicle and the actual lateral acceleration is equal to or greater than a preset threshold. The vehicle power steering control device according to claim 1, wherein the power steering control device is determined to be in a preset non-linear region . The assist torque correction means corrects the basic assist torque according to a deviation between a target lateral acceleration calculated based on a vehicle motion model and an actual lateral acceleration according to at least a driving state of the vehicle. The power steering control device for a vehicle according to claim 1 or 2. Said assist torque correcting means that sets the gain in response to the actual lateral acceleration and the vehicle speed, correcting the basic assist torque by multiplying the gain deviation of the target lateral acceleration and the actual lateral acceleration power steering control apparatus for a vehicle according to claim 3, wherein you characterized.

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