JP2011121444A - Power steering control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering control device with high reliability and excellent sense of security, capable of properly reducing steering force according to a traveling state of a vehicle and surely conveying information such as a grip limit of a tire to a driver. <P>SOLUTION: A basic assist instruction value Ip is set based on steering torque Tq and vehicle speed V. Lateral acceleration generated in the vehicle based on a motion model of the vehicle is calculated as norm lateral acceleration (d<SP>2</SP>y/dt<SP>2</SP>)0. A deviation Δ(d<SP>2</SP>y/dt<SP>2</SP>) between the norm lateral acceleration (d<SP>2</SP>y/dt<SP>2</SP>)0 and actually generated lateral acceleration (d<SP>2</SP>y/dt<SP>2</SP>) is calculated. Correction amount (correction instruction value)Is of the basic assist instruction value Ip is calculated according to at least the lateral acceleration deviation Δ(d<SP>2</SP>y/dt<SP>2</SP>) and a yaw rate γ. The basic assist instruction value Ip is corrected by the correction instruction value Is, the corrected assist instruction value Ips is output to a motor driving part 21, an electric motor 12 is driven and steering force is assisted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Generally, a power steering device is a system that adds a steering assist force according to a driver's steering torque for the purpose of reducing the steering force, and is effective in reducing a steering force at a low speed such as a stationary stop. As such a power steering control device, various devices have been conventionally proposed. For example, in Japanese Patent Application Laid-Open No. 2002-145099 (hereinafter referred to as Patent Document 1), the yaw rate generated in the vehicle according to the turning angle and The steering reaction force increases as the steering angle increases up to the set steering angle when the lateral acceleration starts to increase proportionally. After the set steering angle is exceeded, the steering reaction force decreases as the steering angle increases. The control amount based on the steering angle is set so that the steering reaction force increases as the yaw rate and the lateral acceleration increase, and the control amount based on the yaw rate and the control amount based on the lateral acceleration are set, and these controls are performed. A technique of a steering control device that sets a steering reaction force from a combination of amounts is disclosed.

JP 2002-145099 A

  However, in the case of the control for increasing the steering reaction force according to the yaw rate and the lateral acceleration as disclosed in the above-mentioned Patent Document 1, the yaw rate and the lateral acceleration are saturated up to the grip limit region of the tire, and basically the steering reaction force is reduced. Although the force does not increase any more, it is assumed that the steering force will become heavier if the vehicle tends to spin and excessive yaw rate occurs, so there is a problem that it is difficult for the driver to understand the tire grip limit .

  The present invention has been made in view of the above circumstances, and appropriately reduces the steering force in accordance with the traveling state of the vehicle, and can reliably convey information such as the grip limit of the tire to the driver, and is reliable. The object is to provide a power steering control device for a vehicle that is high in safety and excellent in safety.

  The present invention calculates basic assist force setting means for setting an assist force of a steering force as a basic assist force according to a driving state of the vehicle, and calculates a lateral acceleration generated in the vehicle as a reference lateral acceleration based on a vehicle motion model. Reference lateral acceleration calculation means, lateral acceleration deviation calculation means for calculating a deviation between the reference lateral acceleration and the actually generated lateral acceleration, and a correction amount of the basic assist force according to at least the lateral acceleration deviation and the yaw rate The basic assist force set by the basic assist force setting unit is corrected by the assist force correction amount calculated by the assist force correction amount calculating unit, and the corrected assist force is used. And a steering control means for driving and controlling an actuator for assisting the steering force.

  According to the power steering control device for a vehicle according to the present invention, it is possible to appropriately reduce the steering force in accordance with the traveling state of the vehicle, and to reliably transmit information such as the grip limit of the tire to the driver. The effect is high and excellent in security.

1 is a configuration explanatory diagram of a vehicle steering system according to a first embodiment of the present invention. FIG. It is a functional block diagram of the steering control part which concerns on 1st Embodiment of this invention. It is a flowchart of the power steering control program which concerns on 1st Embodiment of this invention. It is a flowchart of the correction instruction value calculation routine which concerns on 1st Embodiment of this invention. It is explanatory drawing of the map of the basic assistance instruction | indication value which concerns on 1st Embodiment of this invention. It is explanatory drawing of the characteristic map of the lateral acceleration deviation sensitive gain which concerns on 1st Embodiment of this invention. It is explanatory drawing of the characteristic map of the vehicle speed sensitive gain which concerns on 1st Embodiment of this invention. It is explanatory drawing of the characteristic map of the steering torque sensitive gain which concerns on 1st Embodiment of this invention. Δ relative to the handle angle according to the first embodiment of the present invention ^{(d 2 y / dt 2)} , (Gy · Gv · Gt), γ, TSA, is an explanatory diagram showing an example of the value of the steering force. It is a flowchart of the correction instruction value calculation routine which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows an example of the value of (1-Gy), TSB, and steering force with respect to the steering wheel angle which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 9 show a first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes an electric power steering apparatus. In this electric power steering apparatus 1, a steering shaft 2 is rotatably supported by a 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 instruction value Ips (current value)) set by a steering control unit 20 described later.

The steering control unit 20 includes a vehicle speed sensor 31 that detects the vehicle speed V of the vehicle, a handle angle sensor 32 that detects the handle angle θH, a lateral acceleration sensor 33 that detects lateral acceleration (d ² y / dt ² ), and a yaw rate γ. A yaw rate sensor 34 for detecting and a steering torque sensor 35 for detecting a steering torque Tq applied to the steering wheel 4 are connected.

The steering control unit 20 sets a basic assist instruction value Ip based on, for example, the steering torque Tq and the vehicle speed V, and determines the lateral acceleration generated in the vehicle based on the vehicle motion model as a reference lateral acceleration (d ² y / dt ² ) is calculated as 0, calculating the norm lateral acceleration ^(d 2 y / ^dt 2) 0 actually lateral acceleration that occurs when ^(d 2 y / dt ²⁾ deviation between the delta ^(d 2 y / dt ²⁾ Then, the correction amount (correction instruction value) Is of the basic assist instruction value Ip is calculated according to at least the lateral acceleration deviation Δ (d ² y / dt ² ) and the yaw rate γ, and the basic assist instruction value Ip is calculated as the correction instruction value Is. The corrected assist instruction value Ips is output to the motor drive unit 21 to drive the electric motor 12 and assist the steering force.

  That is, as shown in FIG. 2, the steering control unit 20 includes a basic assist instruction value setting unit 20a, a reference lateral acceleration calculation unit 20b, a lateral acceleration deviation calculation unit 20c, a lateral acceleration deviation sensitive gain setting unit 20d, and a vehicle speed sensitive gain setting. It mainly comprises a unit 20e, a steering torque sensitive gain setting unit 20f, an assist torque correction value calculation unit 20g, a correction instruction value calculation unit 20h, and an assist instruction value calculation output unit 20i.

  The basic assist instruction value setting unit 20 a receives the vehicle speed V from the vehicle speed sensor 31 and the steering torque Tq from the steering torque sensor 35. Then, a basic assist instruction value Ip (current value) is set with reference to a preset map (for example, shown in FIG. 5), and is output to the assist instruction value calculation output unit 20i. That is, in the present embodiment, the basic assist instruction value Ip is set to a larger value (so that the assist force increases) as the steering torque Tq is larger and the vehicle speed V is lower, based on the map shown in FIG. It has come to be. The setting of the basic assist instruction value Ip is not limited to the setting shown in the present embodiment, and may be set by another known method. Thus, the basic assist instruction value setting unit 20a is provided as basic assist force setting means.

The reference lateral acceleration calculation unit 20 b receives the vehicle speed V from the vehicle speed sensor 31 and the handle angle θH from the handle angle sensor 32. Then, based on the following equation (1) derived from the vehicle motion model, the lateral acceleration generated in the vehicle is calculated as a reference lateral acceleration (d ² y / dt ² ) 0, and the lateral acceleration deviation calculating unit 20c Output. That is, the standard lateral acceleration calculation unit 20b is provided as a standard lateral acceleration calculation unit.
(D ² y / dt ² ) 0 = | θH · G1 | (1)
Here, G1 is a lateral acceleration gain, and is calculated by the following equation (2).
G1 = (1 / (1 + A · V ² )) · (V ² / (l · n)) (2)
Here, A is a stability factor, l is a wheel base, and n is a steering gear ratio.

Lateral acceleration deviation calculator 20c receives lateral acceleration (d ² y / dt ² ) from lateral acceleration sensor 33 and receives normative lateral acceleration (d ² y / dt ² ) 0 from normative lateral acceleration calculator 20b. . Then, the lateral acceleration deviation Δ (d ² y / dt ² ) is calculated by the following equation (3) and output to the lateral acceleration deviation sensitive gain setting unit 20d. That is, the lateral acceleration deviation computing unit 20c is provided as lateral acceleration deviation computing means.
Δ (d ² y / dt ² ) = (d ² y / dt ² ) 0− | (d ² y / dt ² ) | (3)

Lateral acceleration deviation sensitive gain setting unit 20d receives lateral acceleration deviation Δ (d ² y / dt ² ) from lateral acceleration deviation calculation unit 20c. Then, referring to a characteristic map of the lateral acceleration deviation sensitive gain Gy with respect to the lateral acceleration deviation Δ (d ² y / dt ² ) as shown in FIG. The gain Gy is set and output to the assist torque correction value calculator 20g. Here, as shown in FIG. 6, the lateral acceleration deviation sensitive gain Gy according to the present embodiment has a value of 1 or less and becomes smaller as the lateral acceleration deviation Δ (d ² y / dt ² ) becomes larger. It has become. The significance of setting the lateral acceleration deviation sensitive gain Gy with such characteristics will be described in detail in the description of the assist torque correction value calculation unit 20g described later.

  The vehicle speed sensitive gain setting unit 20 e receives the vehicle speed V from the vehicle speed sensor 31. Then, the vehicle speed sensitive gain Gv is set with reference to the characteristic map of the vehicle speed sensitive gain Gv with respect to the vehicle speed V as shown in FIG. Output. Here, the vehicle speed sensitive gain Gv according to the present embodiment has a characteristic that increases in a preset high-speed traveling region, as shown in FIG. The significance of setting the vehicle speed sensitive gain Gv with such characteristics will be described in detail in the description of the assist torque correction value calculation unit 20g described later.

  The steering torque sensitive gain setting unit 20 f receives the steering torque Tq from the steering torque sensor 35. Then, referring to a characteristic map of the steering torque sensitive gain Gt with respect to the steering torque Tq as shown in FIG. 8, which has been previously set by experiments and calculations, the steering torque sensitive gain Gt is set and the assist torque correction value is calculated. Output to the unit 20g. Here, as shown in FIG. 8, the steering torque sensitive gain Gt according to the present embodiment has a value of 1 or less and has a characteristic such that the steering torque Tq becomes 0 in a region near 0. The significance of setting the steering torque sensitive gain Gt with such characteristics will be described in detail in the description of the assist torque correction value calculation unit 20g described later.

The assist torque correction value calculator 20g receives the yaw rate γ from the yaw rate sensor 34, the lateral acceleration deviation sensitive gain setting unit 20d from the lateral acceleration deviation sensitive gain setting unit 20d, and the vehicle speed sensitive gain Gv from the vehicle speed sensitive gain setting unit 20e. The steering torque sensitive gain Gt is inputted from the steering torque sensitive gain setting unit 20f. Then, the assist torque correction value TSA is calculated according to the following equation (4) and output to the correction instruction value calculation unit 20h.
TSA = Gy · Gv · Gt · γ (4)

  In other words, in the first embodiment, the assist torque correction value TSA is calculated by multiplying the yaw rate γ by the respective gains Gy, Gv, and Gt. This is a value that is a source of the subtraction correction amount from the instruction value Ip.

  Therefore, as the assist torque correction value TSA increases, the basic assist instruction value Ip becomes smaller, the assist amount decreases, and the driver's steering force is required more.

  Conversely, the smaller the assist torque correction value TSA, the larger the basic assist instruction value Ip, the greater the assist amount, and the smaller the driver's steering force.

Here, as described above, the lateral acceleration deviation sensitive gain setting unit 20d sets the lateral acceleration deviation sensitive gain Gy to a value equal to or less than 1 as shown in FIG. 6, and the lateral acceleration deviation Δ (d ² y / dt ² ) Is larger, the smaller the characteristic is. Therefore, as the lateral acceleration deviation Δ (d ² y / dt ² ) increases, the assist torque correction value TSA decreases, the basic assist instruction value Ip increases, and the assist amount increases. The driver's steering force is reduced. That is, when the lateral acceleration deviation Δ (d ² y / dt ² ) increases, the lateral acceleration (d ² y / dt ² ) that actually occurs even when the steering wheel is steered is small and approaches the grip limit. In such a state, the driver's steering force should be reduced so that the driver feels that the steering force is lost and that the driver is close to the grip limit. To do.

  Further, as shown in FIG. 7, the vehicle speed sensitive gain Gv has a characteristic that increases in a preset high-speed traveling region by the vehicle speed sensitive gain setting unit 20e. This is to eliminate the influence of the yaw rate γ generated with respect to the steering wheel angle θH in the high-speed traveling region.

  Further, as shown in FIG. 8, the steering torque sensitive gain setting unit 20f has a characteristic that the steering torque sensitive gain Gt is a value of 1 or less and the steering torque Tq becomes 0 in the vicinity of 0, as shown in FIG. . This is because the assist torque correction value TSA is set based on the abnormal signal even if the yaw rate sensor 34 or the like is abnormal and a signal is output when the hand is released. This is to reliably prevent the steering wheel from being turned by the electric motor 12.

  The correction instruction value calculation unit 20h receives the assist torque correction value TSA as a subtraction correction amount from the basic assist instruction value Ip from the assist torque correction value calculation unit 20g. The assist torque correction value TSA is converted into a current value, such as by multiplying a predetermined gain, and the correction instruction value Is is calculated and output to the assist instruction value calculation output unit 20i. Thus, in the present embodiment, the lateral acceleration deviation sensitive gain setting unit 20d, the vehicle speed sensitive gain setting unit 20e, the steering torque sensitive gain setting unit 20f, the assist torque correction value calculation unit 20g, and the correction instruction value calculation unit 20h Assist force correction amount calculation means is configured.

The assist instruction value calculation output unit 20i is provided as a steering control unit. The basic instruction instruction value Ip is input from the basic assist instruction value setting unit 20a, and the correction instruction value Is is input from the correction instruction value calculation unit 20h. . Then, the assist instruction value Ips is calculated by the following equation (5), and is output to the motor drive unit 21 to drive the electric motor 12 to assist the steering force.
Ips = Ip−Is (5)
Next, the steering assist 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, lateral acceleration (d ² y / dt ² ), yaw rate γ, and steering torque Tq are read.

  Next, in S102, the basic assist instruction value setting unit 20a sets a basic assist instruction value Ip (current value) with reference to a preset map (for example, shown in FIG. 5).

  Next, proceeding to S103, the correction instruction value Is is calculated as described later according to the flowchart of the correction instruction value calculation routine shown in FIG.

  Next, the process proceeds to S104, where the assist instruction value calculation output unit 20i calculates the assist instruction value Ips according to the above-described equation (5) and outputs it to the motor drive unit 21 to drive the electric motor 12 and assist the steering force. To do.

Next, the calculation process of the correction instruction value Is executed in S103 described above will be described with reference to the flowchart of FIG.
First, in S201, the reference lateral acceleration calculation unit 20b calculates the reference lateral acceleration (d ² y / dt ² ) 0 by the above-described equation (1).

Next, the process proceeds to S202, where the lateral acceleration deviation calculation unit 20c calculates the lateral acceleration deviation Δ (d ² y / dt ² ) according to the above-described equation (3).

Next, the process proceeds to S203, and the lateral acceleration deviation Δ (d ² y / dt ² ) as shown in FIG. 6 set in advance by experiments and calculations in the lateral acceleration deviation sensitive gain setting unit 20d is shown. The lateral acceleration deviation sensitive gain Gy is set with reference to the characteristic map of the acceleration deviation sensitive gain Gy.

  Next, in S204, the vehicle speed sensitive gain Gv with reference to a characteristic map of the vehicle speed sensitive gain Gv with respect to the vehicle speed V as shown in FIG. Set.

  Next, proceeding to S205, refer to the characteristic map of the steering torque sensitive gain Gt with respect to the steering torque Tq as shown in FIG. To set the steering torque sensitive gain Gt.

  Next, the process proceeds to S206, where the assist torque correction value calculation unit 20g calculates the assist torque correction value TSA, which is the basis of the subtraction correction amount from the basic assist instruction value Ip, according to the above-described equation (4).

  In step S207, the correction instruction value calculation unit 20h calculates the correction instruction value Is and exits the routine.

An example of each parameter set by the steering assist control executed by the steering control unit 20 will be described with reference to FIG.
First, as shown in FIG. 9 (a), the reference lateral acceleration (d ² y / dt ² ) 0 with respect to the steering wheel angle θH is calculated as shown by the broken line. The lateral acceleration (d ² y / dt ² ) generated is suppressed from rising. Thus, the lateral acceleration deviation Δ (d ² y / dt ² ) increases as the steering wheel angle θH increases.

  The value obtained by multiplying the gains Gy, Gv, and Gt of the assist torque correction value TSA that is the base of the subtraction correction amount from the basic assist instruction value Ip is as shown in FIG. In the region below θHl, the influence of the steering torque sensitive gain Gt appears, and when the steering wheel angle θH is near zero, the steering torque Tq is near zero, the steering torque sensitive gain Gt is set to zero, and (Gy · Gv -The value of Gt is 0. Further, in the region where the steering wheel angle θH is equal to or larger than θHh, the influence of the lateral acceleration deviation sensitive gain Gy appears, and the value of (Gy · Gv · Gt) is set smaller as the steering wheel angle θH increases.

On the other hand, the yaw rate γ detected by the yaw rate sensor 34, as shown by the solid line in FIG. 9C, increases the handle angle θH and increases the grip limit, similarly to the lateral acceleration (d ² y / dt ² ) described above. As you get closer to, the rise will be suppressed.

  Thus, by multiplying the values obtained by multiplying the gains Gy, Gv, and Gt obtained as shown in FIG. 9B and the detected yaw rate γ as shown in FIG. 9C, FIG. As shown in FIG. 5, an assist torque correction value TSA that is a source of a subtraction correction amount from the basic assist instruction value Ip is calculated.

  A current value corresponding to the assist torque correction value TSA is subtracted from the basic assist instruction value Ip to calculate an assist instruction value Ips, which is output to the motor drive unit 21 to drive the electric motor 12 to assist the steering force. As a result, the steering force required for the driver is drastically reduced near the grip limit as compared with the conventional required steering force (shown by a broken line in the figure) as shown in FIG. The wheel 4 is designed to give the driver easy-to-understand information.

As described above, according to the first embodiment of the present invention, the basic assist instruction value Ip is set based on the steering torque Tq and the vehicle speed V, and the lateral acceleration generated in the vehicle is determined based on the vehicle motion model. The lateral acceleration (d ² y / dt ² ) is calculated as 0, and the deviation Δ () between the standard lateral acceleration (d ² y / dt ² ) 0 and the actually generated lateral acceleration (d ² y / dt ² ) d ² y / dt ² ) is calculated, and the correction amount (correction instruction value) Is of the basic assist instruction value Ip is calculated according to at least the lateral acceleration deviation Δ (d ² y / dt ² ) and the yaw rate γ. The assist instruction value Ip is corrected with the correction instruction value Is, and the corrected assist instruction value Ips is output to the motor drive unit 21 to drive the electric motor 12 to assist the steering force.

For this reason, in the traveling state in which the linearity of the lateral acceleration (d ² y / dt ² ) with respect to the steering wheel angle θH is maintained, a steering force corresponding to the yaw rate γ is added to improve the response of the steering wheel 4, If the nonlinearity of the lateral acceleration (d ² y / dt ² ) with respect to the steering wheel angle θH increases due to the grip limit of the tire, the above-mentioned additional steering force is reduced and corrected, and the driver is informed of the steering wheel 4 being missed. Can be given. Thus, the steering force can be appropriately reduced according to the running state of the vehicle, and information such as the grip limit of the tire can be reliably transmitted to the driver, so that the reliability is high and the sense of security is excellent.

Next, FIGS. 10 and 11 show a second embodiment of the present invention.
In the first embodiment described above, the assist torque correction value calculation unit 20g calculates the assist torque correction value TSA that is the source of the subtraction correction amount from the basic assist instruction value Ip to calculate the correction instruction value Is. However, in the second embodiment of the present invention, the correction instruction value Is is calculated by calculating the assist torque correction value TSB that is the source of the addition correction amount with respect to the basic assist instruction value Ip. Unlike the first embodiment, the other components and functions are the same as those of the first embodiment. The same components are denoted by the same reference numerals, and description thereof is omitted.

That is, as in the first embodiment, the assist torque correction value calculation unit 20g according to the second embodiment receives the yaw rate γ from the yaw rate sensor 34 and the lateral acceleration deviation sensitivity gain setting unit 20d from the lateral acceleration deviation sensitivity gain Gy. Is input, a vehicle speed sensitive gain Gv is input from the vehicle speed sensitive gain setting unit 20e, and a steering torque sensitive gain Gt is input from the steering torque sensitive gain setting unit 20f. Then, the assist torque correction value TSB is calculated by the following equation (6), and is output to the correction instruction value calculation unit 20h.
TSB = (1-Gy) · Gv · Gt · γ (6)

  That is, in the second embodiment, the assist torque correction value TSB is calculated by multiplying the yaw rate γ by (1−Gy) and the gains Gv and Gt. The value TSB is a value that is a source of the addition correction amount with respect to the basic assist instruction value Ip.

  Therefore, as the assist torque correction value TSB increases, the basic assist instruction value Ip increases, the assist amount increases, and the driver's steering force decreases.

  Conversely, the smaller the assist torque correction value TSB is, the smaller the basic assist instruction value Ip is, the smaller the assist amount, and the greater the driver's steering force is required.

Here, as described above, the lateral acceleration deviation sensitive gain setting unit 20d sets the lateral acceleration deviation sensitive gain Gy to a value equal to or less than 1 as shown in FIG. 6, and the lateral acceleration deviation Δ (d ² y / dt ² ) Increases, the characteristic decreases, and (1-Gy) increases. Therefore, as the lateral acceleration deviation Δ (d ² y / dt ² ) increases, the assist torque correction value TSB increases, the basic assist instruction value Ip increases, and the assist amount increases. The driver's steering force is reduced. That is, when the lateral acceleration deviation Δ (d ² y / dt ² ) increases, the lateral acceleration (d ² y / dt ² ) that actually occurs even when the steering wheel is steered is small and approaches the grip limit. In such a state, the driver's steering force should be reduced so that the driver feels that the steering force is lost and that the driver is close to the grip limit. To do.

  The correction instruction value calculation unit 20h receives the assist torque correction value TSB as an addition correction amount for the basic assist instruction value Ip from the assist torque correction value calculation unit 20g. The assist torque correction value TSB is converted into a current value, such as by multiplying the assist torque correction value TSB by a predetermined gain, the correction instruction value Is is calculated, and output to the assist instruction value calculation output unit 20i.

Next, the calculation process of the correction instruction value Is according to the second embodiment executed in S103 described above will be described with reference to the flowchart of FIG.
As in the first embodiment, the normal lateral acceleration (d ² y / dt ² ) 0 is calculated in S201, the lateral acceleration deviation Δ (d ² y / dt ² ) is calculated in S202, and the lateral acceleration deviation response is detected in S203. A gain Gy is set, a vehicle speed sensitive gain Gv is set in S204, and a steering torque sensitive gain Gt is set in S205.

  In step S301, the assist torque correction value calculation unit 20g calculates the assist torque correction value TSB that is the basis of the addition correction amount with respect to the basic assist instruction value Ip using the above-described equation (6).

  Thereafter, the process proceeds to S207, where the correction instruction value calculation unit 20h calculates the correction instruction value Is and exits the routine.

In the second embodiment, an example of each parameter set by the steering assist control executed by the steering control unit 20 will be described with reference to FIG.
As shown in FIG. 11A, when the handle angle θH increases and approaches the grip limit, the lateral acceleration deviation Δ (d ² y / dt ² ) increases and the lateral acceleration deviation sensitive gain Gy decreases. , (1-Gy) becomes larger.

  For this reason, as shown in FIG. 11B, the assist torque correction value TSB calculated by the above-described equation (6) becomes (1-Gy) when the handle angle θH increases and approaches the grip limit. A large value is affected.

  A current value corresponding to the assist torque correction value TSB is added to the basic assist instruction value Ip to calculate an assist instruction value Ips, which is output to the motor drive unit 21 to drive the electric motor 12 to assist the steering force. To do. Thereby, as shown in FIG. 11C, the steering force required for the driver becomes smaller near the grip limit than the conventional required steering force (indicated by a broken line in the figure), and the steering wheel 4 Information is given to the driver as a missed response.

Therefore, also in the second embodiment, as in the first embodiment, the yaw rate γ is reduced in the traveling state in which the linearity of the lateral acceleration (d ² y / dt ² ) with respect to the steering wheel angle θH is maintained. When the response of the steering wheel 4 is improved by adding a corresponding steering force, and the nonlinearity of the lateral acceleration (d ² y / dt ² ) with respect to the steering wheel angle θH increases due to the grip limit of the tire, The additional rudder force can be reduced and corrected, and information can be given to the driver in an easy-to-understand manner as the steering wheel 4 is suddenly missed. Thus, the steering force is appropriately reduced according to the running state of the vehicle, and information such as the grip limit of the tire can be reliably transmitted to the driver, so that the reliability is high and the sense of security is excellent.

  In the first and second embodiments of the present invention, it is described that the vehicle speed sensitive gain Gv and the steering torque sensitive gain Gt are taken into account when calculating the assist torque correction values TSA and TSB. May be calculated without considering either of the assist torque correction values TSA and TSB or both of these gains.

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 4 Steering wheel 12 Electric motor (actuator)
20 Steering control unit 20a Basic assist instruction value setting unit (basic assist force setting means)
20b Standard lateral acceleration calculation unit (standard lateral acceleration calculation means)
20c Lateral acceleration deviation computing unit (lateral acceleration deviation computing means)
20d Lateral acceleration deviation sensitive gain setting unit (assist force correction amount calculation means)
20e Vehicle speed sensitive gain setting unit (assist force correction amount calculation means)
20f Steering torque sensitive gain setting unit (assist force correction amount calculation means)
20g assist torque correction value calculation unit (assist force correction amount calculation means)
20h Correction instruction value calculation unit (assist force correction amount calculation means)
20i Assist instruction value calculation output unit (steering control means)
DESCRIPTION OF SYMBOLS 21 Motor drive part 31 Vehicle speed sensor 32 Handle angle sensor 33 Lateral acceleration sensor 34 Yaw rate sensor 35 Steering torque sensor

Claims (5)

Basic assist force setting means for setting the assist force of the steering force as a basic assist force according to the driving state of the vehicle;
A reference lateral acceleration calculating means for calculating a lateral acceleration generated in the vehicle as a reference lateral acceleration based on a vehicle motion model;
Lateral acceleration deviation calculating means for calculating a deviation between the reference lateral acceleration and the lateral acceleration actually generated;
Assist force correction amount calculating means for calculating a correction amount of the basic assist force according to at least the lateral acceleration deviation and the yaw rate;
Steering for driving and controlling the actuator for assisting the steering force with the corrected assist force by correcting the basic assist force set by the basic assist force setting means with the assist force correction amount calculated by the assist force correction amount calculating means. Control means;
A vehicle power steering control device.   The assist force correction amount calculated by the assist force correction amount calculation means is a subtraction correction amount from the basic assist force, and is calculated so that the assist force correction amount decreases as the lateral acceleration deviation increases. The power steering control device for a vehicle according to claim 1.   The assist force correction amount calculated by the assist force correction amount calculation means is an addition correction amount for the basic assist force, and is calculated so that the assist force correction amount increases as the lateral acceleration deviation increases. The power steering control device for a vehicle according to claim 1.   4. The vehicle according to claim 1, wherein the assist force correction amount calculating unit sets the basic assist force correction amount to 0 in a region where the steering torque is close to 0. 5. Power steering control device.   5. The vehicle according to claim 1, wherein the assist force correction amount calculating unit sets the assist force correction amount in a direction in which the assist force correction amount increases in a preset high-speed traveling region. Power steering control device.

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