JP2011005928A - Toe-angle control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable proper control in a toe-angle control device for a vehicle, even when the power supply voltage of an actuator fluctuates.SOLUTION: The toe-angle control device including an actuator 8 changing the toe-angle of each wheel of an automobile, and various sensors 10, 11, 14, 17 detecting a moving state amount of the automobile, sets a target control amount of the electric actuator 8 on the basis of a steering angle, a vehicle speed and a yaw rate, and drive-controls the electric actuator 8 on the basis of the target control amount. The toe-angle control device further includes a battery voltage sensor 16 detecting the battery voltage Vb of a battery, and a target driving current correcting portion 26 increasing/decreasing the target control amount on the basis of the battery voltage Vb detected by the battery voltage sensor 16.

Description

  The present invention relates to a toe angle control device that performs toe angle control of a vehicle using an electric actuator, and more particularly to a technique that enables appropriate control even when a power supply voltage fluctuates.

  Some four-wheel vehicles include a rear wheel toe angle control device that changes the toe angles (steering angles) of the left and right rear wheels for the purpose of improving the running stability of the vehicle. In this type of rear wheel toe angle control device, a direct-acting electric actuator is interposed between the knuckle that supports the left and right rear wheels and the vehicle body, and the toe angles of both the left and right wheels are extended and retracted. What changes individually is known (for example, patent document 1). A rear wheel toe angle control device according to Patent Document 1 sets a target toe angle of a rear wheel based on a vehicle speed, a steering angle, a steering angular speed, and the like, and performs an electric actuator by position feedback control based on the target toe angle and an actual toe angle. The drive is controlled.

Japanese Patent Laid-Open No. 9-30438

  However, when only the position feedback control is performed, there is a problem that when the power supply voltage of the electric actuator fluctuates, the output of the electric actuator also fluctuates and the toe angle control performance deteriorates. For this reason, it is conceivable to detect the drive current supplied to the electric actuator by a current sensor and perform current feedback control based on the current value. However, when current feedback control is performed, there is a problem in that if the current sensor fails, the toe angle control performance deteriorates.

  The present invention has been made in view of the above problems, and an object thereof is to provide a toe angle control device for a vehicle that enables appropriate control even when the power supply voltage of an electric actuator varies.

  In order to solve the above-mentioned problem, a first aspect of the present invention is an actuator (8) that changes a toe angle of each wheel (3) of a vehicle (100), and a motion state that detects a motion state amount of the vehicle. A vehicle control unit configured to set a target control amount of the actuator based on the motion state amount, and to drive and control the actuator based on the target control amount. An angle control device (6), comprising: a power supply voltage detecting means (16) for detecting a power supply voltage of the actuator; and a target control for increasing or decreasing the target control amount based on the power supply voltage detected by the power supply voltage detecting means. And an amount correction means (26, 27).

  According to this configuration, the target control amount of the actuator is corrected according to the power supply voltage of the actuator, so that it is possible to perform appropriate toe angle control even when the power supply voltage varies.

  According to a second aspect, in the first aspect, the target control amount correction means increases the target control amount as the power supply voltage decreases.

  According to a third aspect of the present invention, there is provided an actuator (8) for changing a toe angle of each wheel (3) of a vehicle (100) and a motion state quantity detecting means (10, 11, 14, 17 for detecting a motion state quantity of the vehicle. A toe angle control device (6) for a vehicle that sets a target control amount of the actuator based on the amount of motion state and duty-controls the actuator based on the target control amount, Power supply voltage detection means (16) for detecting the power supply voltage of the actuator; and duty correction means (26, 27) for increasing or decreasing the duty ratio based on the target control amount based on the power supply voltage detected by the power supply voltage detection means; It is characterized by having.

  According to this configuration, since the duty ratio of the actuator is corrected according to the power supply voltage of the actuator, appropriate toe angle control can be performed even when the power supply voltage fluctuates.

  In a fourth aspect based on the third aspect, the duty correction means increases the duty ratio as the power supply voltage decreases.

  According to this configuration, even when the output of the actuator decreases due to a decrease in the power supply voltage, the decrease in the output of the actuator is suppressed and appropriate toe angle control can be performed.

  According to the above configuration, the toe angle control device for a vehicle can perform appropriate control even when the power supply voltage fluctuates.

Schematic configuration diagram of a four-wheeled vehicle including a rear wheel toe angle control device according to an embodiment The block diagram which shows the principal part of ECU which concerns on embodiment Map showing target current correction factor according to battery voltage The flowchart which shows the procedure of the rear steering control which concerns on embodiment

  Hereinafter, an embodiment in which the present invention is applied to a rear wheel toe angle control device for a four-wheeled vehicle will be described in detail with reference to the drawings. In the description, for the four wheels and members disposed therewith, that is, tires, suspensions, and the like, subscripts indicating front, rear, left, and right are attached to the numerals, respectively, for example, left front wheel 3fl, right front wheel 3fr. The left rear wheel 3 rl and the right rear wheel 3 rr are referred to as “wheel 3”.

<Schematic configuration of automobile>
As shown in FIG. 1, a vehicle body 1 of an automobile 100 is provided with wheels 3 with tires 2 mounted on the front, rear, left and right. Each wheel 3 is pivotally supported by a knuckle 7 and is suspended on the vehicle body 1 by a suspension 5 including a suspension arm, a spring, a damper 4 and the like.

  The vehicle 100 includes a front wheel steering device 9 that directly steers the left and right front wheels 3fl and 3fr via a rack and pinion mechanism by steering the steering wheel 19, and left and right rear suspensions 5rl and 5rr. And a pair of left and right rear wheel toe angle control devices 6l and 6r for individually changing the toe angles of the rear wheels 3rl and 3rr by driving the electric actuators 8l and 8r.

  The electric actuators 8l and 8r are direct acting electric actuators including a DC motor (not shown) and an output rod that is moved forward and backward in the axial direction by the DC motor. The tips of the output rods are connected to the knuckles 7rl and 7rr, respectively, and the toe angles of the rear wheels 3rl and 3rr change as the electric actuators 8l and 8r expand and contract. The DC motors of the electric actuators 8l and 8r include a switching circuit used for PWM control, and are PWM controlled by the ECU 20 described later using the vehicle-mounted battery 15 as a power source.

  The rear wheel toe angle control devices 6l and 6r freely control the toe-in / to-out of the left and right rear wheels 3rl and 3rr under appropriate conditions by displacing the left and right electric actuators 8l and 8r symmetrically at the same time. In addition, if one of the left and right electric actuators 8l and 8r is extended and the other is contracted, the left and right rear wheels 3rl and 3rr can be steered left and right.

  Various systems including the rear wheel toe angle control device 6 are controlled by an ECU (Electronic Control Unit) 20 provided in the automobile 100. The ECU 20 includes a CPU, ROM, RAM, peripheral circuit, input / output interface, various drivers, and the like, and is connected to each sensor, the damper 4, the electric actuator 8, and the like which will be described later via a communication line.

  The automobile 100 includes a steering angle sensor 10 that detects the steering angle δ of the steering wheel 19, a vehicle speed sensor 11 that detects the vehicle speed v, a yaw rate sensor 14 that detects the yaw rate γ, and a battery voltage sensor that detects the voltage Vb of the battery 15 ( (Power supply voltage detection means) 16 and the like are installed at appropriate positions of the vehicle body 1. In addition, each electric actuator 8 is provided with a position sensor (linear encoder) 17 for detecting its expansion / contraction position P. The steering angle δ, the vehicle speed v, the yaw rate γ, the expansion / contraction position P and the like are referred to as the vehicle motion state quantity, and the steering angle sensor 10, the vehicle speed sensor 11, the yaw rate sensor 14, the position sensor 17 and the like are referred to as the motion state quantity detection means.

<Configuration of ECU>
FIG. 2 is a block diagram illustrating a main part of the ECU 20 according to the first embodiment. The ECU 20 includes an input interface 21, a target toe angle setting unit 23, a target drive amount setting unit 24, a target drive current setting unit 25, and a target drive current correction unit that receive detection signals from the sensors 10, 11, 14, 16, and 17. 26, a current correction coefficient setting unit 27, a drive current output unit 28, and an output interface 29.

  The target toe angle setting unit 23 sets a rear wheel target toe angle At by a known method based on detection signals from the steering angle sensor 10, the vehicle speed sensor 11, and the yaw rate sensor 14. The target drive amount setting unit 24 calculates an actual rear wheel toe angle (hereinafter referred to as an actual toe angle) Ar from the detection signal of the position sensor 17, and performs a predetermined control on the difference between the target toe angle At and the actual toe angle Ar. The target drive amount Dt of the electric actuator 8 is set by multiplying the gain G (feedback gain). Note that the target toe angle At and the actual toe angle Ar may be expressed as a target expansion / contraction position and an actual expansion / contraction position of the electric actuator.

  The target drive current setting unit 25 sets the drive current base value Ib based on the target drive amount Dt. In the present embodiment, the drive current base value Ib is represented by a duty ratio (0 to 100%).

  The current correction coefficient setting unit 27 sets the current correction coefficient K with reference to the map shown in FIG. 3 based on the battery voltage Vb of the battery 15 detected by the battery voltage sensor 16. FIG. 3 is a map showing the current correction coefficient K corresponding to the battery voltage Vb. In the map shown in FIG. 3, when the reference voltage V0 is a normal voltage (for example, 12 to 16 V for a passenger car battery (lead storage battery)), the current correction coefficient K is 1, and the battery voltage Vb is The current correction coefficient K increases stepwise as it decreases. In the present embodiment, the battery voltage Vb is a performance limit voltage V1 (a voltage at which the ECU 20 feels a decrease in performance), a performance guarantee voltage V2 (a voltage that can drive the electric actuator 8, for example, 10V for a battery for a passenger car) The correction coefficient increases every time the battery voltage Vb decreases after a certain). As a measure against noise, a hysteresis is provided between the lower side and the higher side of the battery voltage Vb so that the current correction coefficient K does not change immediately even if the performance limit voltage V1 or the performance guarantee voltage V2 is exceeded. Is set.

  The target drive current correction unit 26 calculates the target drive current It by multiplying the drive current base value Ib by the current correction coefficient K. In the present embodiment, the target drive current It is represented by a duty ratio (0 to 100%), and is set to 100 when the value obtained by multiplying the drive current base value Ib by the current correction coefficient K exceeds 100.

  The drive current output unit 28 controls the drive current supplied to the electric actuator 8 based on the target drive current It.

<Rear wheel toe angle control procedure>
Next, a procedure for rear wheel toe angle control according to the embodiment will be described with reference to the flowchart of FIG. FIG. 4 is a flowchart showing a procedure of rear wheel toe angle control according to the embodiment. When the automobile 100 starts driving, the ECU 20 executes the rear wheel toe angle control shown in FIG. 4 at a predetermined control interval (for example, 2 ms). Note that the rear wheel toe angle control is performed on the left and right rear wheels 3rl and 3rr in exactly the same procedure, and therefore only the left rear wheel 3rl will be referred to here.

  First, the ECU 20 sets the current correction coefficient K in the current correction coefficient setting unit 27 with reference to the current correction coefficient map shown in FIG. 3 based on the battery voltage Vb detected by the battery voltage sensor 16 (ST1).

  Next, in the target toe angle setting unit 23, the ECU 20 sets the target toe angle At based on the steering angle θ, the vehicle speed v, and the yaw rate γ (ST2). Then, the ECU 20 sets the target drive amount Dt by multiplying the difference between the target toe angle At and the actual toe angle Ar by the control gain G in the target drive amount setting unit 24 (ST3).

  Subsequently, the ECU 20 sets the drive current base value Ib based on the target drive amount Dt in the target drive current setting unit 25, and sets the drive current base value Ib and the current correction coefficient K in the target drive current correction unit 26. Based on this, the target drive current It is set. Then, the ECU 20 supplies the drive current to the electric actuator 8l at the drive current output unit 28 based on the target drive current It (ST6).

<Effect>
In the above-described embodiment, since the drive current supplied to the electric actuator 8 is corrected based on the battery voltage Vb of the electric actuator 8, the electric actuator 8 is changed even when the battery voltage Vb fluctuates from the predetermined reference voltage V0. It can be controlled appropriately.

  When controlling the electric actuator 8 by changing the duty ratio, if the battery voltage Vb fluctuates, even if the duty ratio does not change (even if it is the same value), the voltage and current supplied to the electric actuator 8 are Since it changes, the drive amount and drive speed of the electric actuator 8 change. For example, when the battery voltage Vb is lower than the reference voltage V0, the voltage and current supplied to the electric actuator 8 are reduced even if the duty ratio is the same, so that the torque and rotational speed of the DC motor of the electric actuator 8 are reduced. Decreases, and the drive amount and drive speed of the electric actuator 8 decrease. That is, the followability and response speed with respect to the target drive amount of the electric actuator 8 are reduced.

  In the present embodiment, the target drive current It is corrected by multiplying the drive current base value Ib set based on the target drive amount Dt by the current correction coefficient K that increases as the battery voltage Vb decreases. It is possible to suppress a decrease in follow-up performance and response speed with respect to the target drive amount of the electric actuator 8 due to a decrease in the voltage Vb. That is, the robustness of the toe angle control device 6 with respect to fluctuations in the power supply voltage is improved.

  In addition, since the target drive current It is set by multiplying the drive current base value Ib by the current correction coefficient K, the current correction coefficient K is stored in advance in the map even when the battery voltage sensor 16 outputs an abnormal value. Since it fluctuates only within the set range, fluctuations in the drive current supplied to the electric actuator 8 are relatively limited, and abnormal operation of the electric actuator 8 can be suppressed. In this respect, it can be said that the stability is high compared to the case where the motor current sensor detects the motor current and performs the current feedback control.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the embodiment, the correction is performed by multiplying the drive current base value Ib set based on the target drive amount Dt by the current correction coefficient K, but the correction coefficient based on the battery voltage Vb is added to the target drive amount Dt. The target drive current may be set based on the corrected target drive amount. Alternatively, a correction amount may be set from a predetermined map based on the battery voltage Vb, and the correction amount may be added to the target drive amount Dt or the drive current base value Ib.

  The map shown in FIG. 3 is an example, and the relationship between the battery voltage Vb and the current correction coefficient K can be arbitrarily set. For example, the current correction coefficient K may be set to increase linearly as the battery voltage Vb decreases. Further, by setting the current correction coefficient K to be constant at the performance guarantee voltage V2 or lower and the reference voltage V0 or higher, the current correction coefficient can be prevented from changing greatly even when the battery voltage sensor 16 fails. .

  1 .... Car body, 3 .... Wheel, 6 .... Rear wheel toe angle control device, 8 .... Electric actuator, 10 .... Steering angle sensor, 11 .... Vehicle speed sensor, 14 .... Yaw rate sensor, 15 .... Battery ( ··· Battery voltage sensor (power supply voltage detection means), ··· Position sensor, ··· ECU, 23 ··· Target toe angle setting unit, ··· Target drive amount setting unit, 25 ··· Target drive Current setting unit, 26... Target drive current correction unit (target control amount correction means), 27... Current correction coefficient setting unit, 28... Drive current output unit, 100.

Claims (4)

An actuator for changing a toe angle of each wheel of the vehicle; and a motion state amount detecting means for detecting a motion state amount of the vehicle; setting a target control amount of the actuator based on the motion state amount; A toe angle control device for a vehicle that drives and controls the actuator based on a target control amount,
Power supply voltage detection means for detecting the power supply voltage of the actuator;
A toe angle control device for a vehicle, comprising: target control amount correction means for increasing or decreasing the target control amount based on the power supply voltage detected by the power supply voltage detection means.   2. The toe angle control device for a vehicle according to claim 1, wherein the target control amount correcting means increases the target control amount as the power supply voltage decreases. An actuator for changing a toe angle of each wheel of the vehicle; and a motion state amount detecting means for detecting a motion state amount of the vehicle; setting a target control amount of the actuator based on the motion state amount; A toe angle control device for a vehicle that performs duty control of the actuator based on a target control amount,
Power supply voltage detection means for detecting the power supply voltage of the actuator;
A toe angle control apparatus for a vehicle, comprising: duty correction means for increasing or decreasing a duty ratio based on the target control amount based on a power supply voltage detected by the power supply voltage detection means.   The toe angle control device for a vehicle according to claim 3, wherein the duty correction means increases the duty ratio as the power supply voltage decreases.

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