JP5052480B2 - Automatic steering control device - Google Patents

Description

  The present invention relates to an automatic steering control device that automatically steers steered wheels by using an electric power steering motor.

  In the conventional automatic steering control device, the steering angle of the steered wheels is controlled using a motor of electric power steering (for example, see Patent Documents 1 to 3).

  That is, in Patent Document 1, the vehicle speed limit value is set so that the turning angular velocity is equal to or less than a predetermined value. Further, in Patent Document 2, automatic steering control is continued when the factor that the steering angle deviation is larger than the threshold is insufficient motor output, and automatic steering control is canceled when the steering angle deviation is larger than the threshold and the current is not the maximum current. It is the composition to do. The maximum steering speed is set from the vehicle speed, the road surface friction coefficient, and the battery voltage. Further, Patent Document 3 includes a steering speed limiting unit that limits the steering speed when the steering torque is equal to or higher than the threshold value and the steering speed is equal to or higher than the threshold value during automatic operation control.

JP 2001-138941 (paragraphs 0027 to 0036, FIG. 5) JP 2007-331480 A (paragraphs 0028-0030, FIG. 3) JP 2007-326453 A (paragraph 0016, FIG. 3)

  Such an automatic steering control device is a low-cost, low-voltage power supply system that uses an electric power steering motor, so that voltage saturation is likely to occur. When voltage saturation occurs, there is a problem that current tracking error increases. Moreover, even if a vehicle speed limit value is set as in Patent Document 1, voltage saturation may occur if the driver operates at a vehicle speed that is equal to or higher than the limit value.

  Also, when current follow-up error and rudder angle follow-up error are large due to voltage saturation, when the motor load is lightened and released from voltage saturation due to changes in road surface condition, the angular velocity changes suddenly in an attempt to reduce the deviation. There are challenges.

  Further, when voltage saturation occurs, the current may not reach the maximum current, and in the configuration of Patent Document 2, automatic steering control may be easily released due to voltage saturation. Also in Patent Document 3, the steering speed cannot be limited with respect to voltage saturation.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an automatic steering control device that prevents voltage saturation.

  An automatic steering control device according to the present invention includes a motor that steers a steered wheel, motor current detection means that detects a current of the motor, a target steer angle of the steered wheel based on calculation or reception from the outside. Target steering angle setting means for setting the steering angle, steering angle detection means for detecting the steering angle of the steered wheels, and calculation of the target current of the motor so that the steering angle follows the target steering angle Motor control means for controlling the motor, and the motor control means sets a motor rotation speed limit value based on the motor current detected by the motor current detection means to limit the rotation speed of the motor. It is characterized by.

  According to the present invention, since the motor rotation speed can be directly limited based on the motor current, voltage saturation can be prevented even when the vehicle speed is high, and the current tracking error can be reduced. Is. In addition, voltage saturation can be prevented and current tracking error can be reduced, so that the angle change when the motor load becomes light due to a change in the road surface condition, etc., from a high motor load that causes voltage saturation. Can be smooth.

Embodiment 1 FIG.
1 is a block diagram showing an automatic steering control apparatus according to Embodiment 1 of the present invention. The left and right steered wheels 3 are steered according to the rotation of the steering shaft 2 connected to the steering wheel 1. A torque sensor 4 is disposed on the steering shaft 2 and detects a steering torque acting on the steering shaft 2. The motor 5 is connected to the steering shaft 2 via the speed reduction mechanism 6 and can apply torque generated by the motor 5 to the steering shaft 2. The motor 5 is provided with an angle sensor (steering angle detection means) 7 that detects the rotation angle of the rotor of the motor 5. The vehicle speed of the vehicle is detected by a vehicle speed sensor 8. The current flowing through the motor 5 is detected by a current sensor 9 as motor current detection means.

  The control unit 10 serves as motor control means, and an automatic steering control unit 101 that calculates a target current for automatic steering, which is a target current of the motor 5 necessary for executing automatic steering control for controlling the position of the steered wheels 3. And an electric power assist control unit 102 for calculating a target current for electric power assist, which is a target current of the motor 5 necessary for performing electric power assist control for assisting the steering of the driver, and detection by a current sensor 9 A current control unit 103 is provided for controlling the current of the motor 5 so that the obtained current matches the electric power assist target current or the automatic steering target current. The control unit 10 includes a microcomputer provided with a memory including a ROM and a RAM, and a drive circuit that drives a motor current.

  The target rudder angle calculator 11 serves as target rudder angle setting means, calculates a target rudder angle during automatic steering control, and transmits the calculated target rudder angle to the control unit 10. The battery voltage sensor 12 detects a battery voltage that is a motor-driven power supply voltage. When automatic steering control is not performed and the driver manually operates the steering wheel 1, the current is adjusted so that the current of the motor 5 matches the target current for electric power assist calculated by the electric power assist controller 102. The control unit 103 is driven. Thereby, at the time of manual steering, a steering control device equivalent to the conventional electric power steering is obtained.

  Next, automatic steering will be described. During automatic steering, the steering shaft 2 is rotated using the motor 5 and the steered wheels 3 are automatically steered while the driver is not performing steering operation. For example, when the driver selects automatic steering at the time of parking or traveling on a highway, the target rudder angle calculator 11 calculates the vehicle state quantity such as the vehicle speed detected by the vehicle speed sensor 8 and the target travel locus of the vehicle. The target rudder angle for following the target travel locus is calculated, and the calculated target rudder angle is transmitted to the control unit 10. The automatic steering control unit 101 of the control unit 10 calculates the target current for automatic steering so that the steering shaft 2 follows the target steering angle from the acquired target steering angle and the rotor rotation angle detected by the angle sensor 7. The target current for automatic steering is output to the current control unit 103.

  During automatic steering, the current control unit 103 performs current control so that the current of the motor 5 follows the target current for automatic steering calculated by the automatic steering control unit 101. As a result, when the driver selects automatic steering, the motor 5 performs a steering operation, so that the driver can park or travel on the highway only by operating the accelerator and brake without steering operation.

  Next, the automatic steering control unit 101 which is a main part of the present invention will be described with reference to the flowchart shown in FIG. The operation shown in the flowchart is repeatedly executed at a control period of a predetermined time. First, in step S1, a target rudder angle is received from an external automatic steering main controller and stored in a memory. In step S2, the rotation angle detected by the angle sensor 6, the motor current detected by the current sensor 9, and the battery voltage detected by the battery voltage sensor 12 are read and stored in the memory.

  In step S3, a motor rotation speed limit value is calculated from the motor current detected by the current sensor 9 and the battery voltage detected by the battery voltage sensor 12. In the first embodiment, the motor 5 is a brushless DC motor, and the angle sensor 7 uses a resolver. However, the motor 5 and the angle sensor 7 are not limited to this, and may be any suitable for electric power steering and automatic steering. For example, the motor 7 may be a DC motor with a brush, the angle sensor may be an encoder, or an angle sensor disposed on the steering shaft 2 may be used. Here, the voltage equation expressed on the dq axis of the brushless DC motor is the equation (1), and the torque calculation equation is the equation (2).

However, Ψ _a = √ (3 / 2Ψ _f ), Ψ _f is the maximum value of the armature linkage flux by the permanent magnet, V _d and V _q are the dq axis components of the armature voltage, and i _d and i _q are Dq axis component of armature current, L _d and L _q are inductances of dq axis, _Ra is armature winding resistance, p = d / dt is a differential operator, P _n is the number of pole pairs, and ω is an electrical angular velocity. .

When the dq-axis inductances L _d and L _q are equal, the torque generated by the motor 5 is proportional to the q-axis current i _{q according} to equation (2). As a steady characteristic, when the term of the differential operator p is 0, Expression (1) becomes Expression (3).

Since the maximum value of the magnitude √ (V _d ² + V _q ² ) of the armature voltage is proportional to the magnitude of the battery voltage supplied to the motor, assuming that the battery voltage is a substantially constant value, the equation (3) It can be seen that the q-axis current i _q , that is, the torque generated by the motor 5 is limited by the induced voltage generated by the motor rotation speed. In other words, the motor rotation speed that can be generated is limited by the q-axis current _iq . Therefore, for example, the relationship between the motor current and the motor rotation speed when the alternator normally generates power and the battery voltage is approximately 14V is stored in a memory as a map, and the motor rotation corresponding to the detected q-axis current i _q is stored. Set the angular speed as the motor speed limit value. Here, the rotational speed limit value may be set from the target current of the motor instead of the detected motor current.

  Further, since the maximum voltage supplied to the motor 5 changes due to a change in the battery voltage due to the failure of the alternator, etc., as shown in FIG. 3, the relationship between the motor current and the motor rotation speed limit value for each battery voltage is represented as a map. The rotation speed limit value corresponding to the detected motor current and the detected battery voltage may be set in a memory. With this configuration, the rotation speed limit value can be appropriately set even when the battery voltage changes.

Further, the rotational speed limit value may be calculated from the dq-axis components i _d and i _{q of} the armature current and the battery voltage using Equation (3).

Next, in step S4, a new target rudder angle 2 (θ _ref2 ) is calculated from the target rudder angle and the motor rotation speed limit value. The operation of step S4 is shown in the flowchart of FIG. Here, the target rudder angle is the target rudder angle θ _ref of the steered wheels 3 in terms of the steering axis. In consideration of reduction ratio of the reduction mechanism 6 calculates the steering angle theta _p of the steered wheels 3 converted steering shaft from the motor rotation angle, converted steering shaft from the motor rotation speed limit value the motor rotational speed limit value

Is calculated.

In the flowchart shown in FIG. 4, in step S21, the target rudder angular velocity is _{calculated from} the deviation between the target rudder angle and the target rudder angle 2 (θ _ref2 ) received from the external automatic steering main controller and the sampling time T _s for repeatedly executing the flowchart. Calculate. However, the initial value of the target steering angle 2 (θ _ref2 ) when the flowchart is first executed is the steering angle θ _p of the steered wheels. As described above, by setting the initial value of the target steering angle 2 (θ _ref2 ) as the steering angle θ _p of the steered wheels, even when there is a deviation between the received target rudder angle and the steered angle when the automatic steering control is executed. Smooth automatic steering control can be realized.

  In step S22, the calculated absolute value of the target rudder angular velocity is the motor rotation speed limit value set in step S3.

If larger, set the target rudder angular speed to the motor speed limit value.

Limit with. In step S23, a new target rudder angle 2 (θ _ref2 ) is calculated by time-integrating the target rudder angular velocity.

With the above operation, the change rate of the target rudder angle 2 (θ _ref2 ) is the motor rotation speed limit value.

In due to restriction, by controlling the motor 5 as the steering angle theta _p to the target steering angle 2 (theta _ref2) to follow, it is possible to prevent voltage saturation by the induced voltage of the motor 5.

In step S5, it calculates a target current of the motor 5 required for turning angle theta _p to the target steering angle 2 (theta _ref2) to follow. FIG. 5 shows a block diagram of position control. s is a Laplace operator. PID control is performed on the deviation between the target rudder angle 2 (θ _ref2 ) and the steered angle θ _p to calculate a target current for automatic steering. K _p is a proportional gain, K _i is an integral gain, and K _d is a differential gain.

  In addition, the current control unit 103 in FIG. 1 controls the current so that the calculated automatic steering target current matches the current detected by the current sensor 9. For example, a voltage command signal such as a PWM signal is calculated from the deviation between the target current for automatic steering and the current detected by the current sensor 9, output to the drive circuit, and driven by the motor 5, which is necessary for angle tracking. The correct motor torque.

  Furthermore, the current control unit 103 includes a current controller abnormality determination unit that determines abnormality of the current control unit 103 when the deviation between the target current for automatic steering and the current detected by the current sensor 9 is larger than the current deviation threshold. Prepare.

  With the configuration described above, the vehicle speed limit value is not set as in Patent Document 1, but the motor rotation speed is directly limited based on the motor current, so that voltage saturation can be reliably prevented. Therefore, it is possible to realize a motor control means with a small motor current tracking error. Since the motor speed is directly limited, voltage saturation can be reliably prevented, and it can be applied to a system that controls the angle by receiving only the target rudder angle from the external controller, even when the vehicle movement amount and the target rudder angle do not correspond Voltage saturation can be prevented.

  Further, since the motor rotation speed is limited based on the motor current, an appropriate motor rotation speed limit corresponding to the motor load can be realized. When the motor load is high, such as stationary, the motor rotation speed limit value is set low, and when the vehicle speed is at a certain level, the motor load is low, so the motor rotation speed limit value can be set high.

  Furthermore, voltage saturation can be prevented even when the battery voltage fluctuates by detecting the battery voltage and setting the motor rotation speed limit value based on the battery voltage.

  When the motor load is lightened due to changes in road surface conditions, etc., when the current deviation is increased due to voltage saturation, and the motor is released from voltage saturation, the rudder angle or rudder angular speed will be reduced to reduce the deviation. With respect to the problem of sudden change, according to the present embodiment, the motor rotation speed is limited and the current deviation can be kept small in a situation where voltage saturation occurs, so that a sudden change in the steering angle and the steering angular speed can be prevented.

  Furthermore, as shown in FIG. 5, in the position control regardless of the presence or absence of speed control, the rotational speed of the motor can be limited based on the motor current, and voltage saturation can be prevented. Therefore, it is possible to realize a motor control means with a small motor current tracking error. In addition, since the current follow-up error of the motor can be reduced, the current deviation threshold value for determining the abnormality of the current controller can be set small, and the current control abnormality can be determined early.

  The motor control means corresponds to the automatic steering control unit 101 and the current control unit 103 having the operation contents shown in the flowchart of FIG. Further, steps S2 to S4 of the flowchart shown in FIG. 2 or the speed limiter of FIG. 5 corresponds to the motor rotation speed limiting means.

Embodiment 2. FIG.
The second embodiment has the same configuration as that of the first embodiment shown in FIG. However, here, only the differences from the first embodiment will be described in the flowchart shown in FIG. 2 showing the operation content of the automatic steering control unit 101 in the control unit 10.

In the second embodiment, in step S3, the rotation angle detected by the angle sensor 7 is second-order differentiated, the rotation angular acceleration is calculated, and the motor inertia torque is calculated by multiplying the motor rotor inertia moment. Next, the calculated inertia torque is divided by the motor torque constant (P _n Ψ _a )) to calculate the motor current conversion value of the inertia torque. The corrected motor current is obtained by subtracting the motor current converted value of the inertia torque from the motor current. The motor rotational speed limit value is calculated from the corrected motor current and the map shown in FIG. That is, the automatic steering control unit 101 is provided with a turning angular acceleration detecting means for calculating (or detecting) the turning angular acceleration of the turning wheel 3, and the motor rotation speed based on the motor current and the turning angular acceleration. Set a limit value to limit the motor speed.

  With the above configuration, the motor rotation speed is limited based on the motor current and the turning angular acceleration, so that voltage saturation is prevented, and when the rotation angular acceleration of the motor is large, the speed limit can be relaxed. it can. Therefore, it becomes difficult to limit the speed for the transient response that requires the acceleration of the motor, and it is compatible with the response.

  In step S3, the map may be changed in consideration of the battery voltage. In the second embodiment, the rotational angular acceleration is calculated by second-order differentiation of the rotational angle detected by the angle sensor 7. However, the present invention is not limited to this, and the motor angular speed estimated from the back electromotive voltage of the motor, the steering shaft It may be calculated from the angle sensor 7 arranged in FIG.

Embodiment 3 FIG.
The third embodiment has a configuration similar to that of the first embodiment shown in FIG. However, here, in the flowchart shown in FIG. 2 showing the operation content of the automatic steering control unit 101 in the control unit 10, the operations after step S4 are different. A flowchart of the third embodiment is shown in FIG.

In the third embodiment, the target rudder angular velocity is calculated from the deviation between the target rudder angle and the steered angle in step S34. _Kpp is a proportional gain. In step S35, the calculated target rudder angular velocity is limited by the motor rotation speed limit value calculated in step S3.

At step S36, turning angular velocity obtained by differentiating the target steering angular velocity limit and the turning angle theta _p

Is calculated, PI control is performed on the deviation, and a target current for automatic steering is calculated.

  With this configuration, it is possible to set a target rudder angular speed that can reliably prevent voltage saturation, and to realize position speed control that prevents an increase in current error due to voltage saturation.

  In addition, when the motor load is lightened due to changes in road surface conditions, etc. when the current deviation is large due to voltage saturation, and the motor is released from voltage saturation, the rudder angle or rudder angular speed will decrease. With respect to the problem of sudden change, according to the present embodiment, the motor rotation speed is limited and the current deviation can be kept small in a situation where voltage saturation occurs, so that a sudden change in the steering angle and the steering angular speed can be prevented.

  In the position control configuration of the third embodiment, as shown in FIG. 5, it is naturally possible to provide a speed limiter after the target rudder angle, calculate a new target rudder angle 2, and perform position control. is there.

  In the third embodiment, the motor control means corresponds to the automatic steering control unit 101 and the current control unit 103 having the operation contents shown in the flowchart of FIG. Further, steps S2 to S4 of the flowchart shown in FIG. 6 or the speed limiter of FIG. 5 corresponds to the motor rotation speed limiting means.

It is a block diagram which shows the automatic steering control apparatus by Embodiment 1 of this invention. It is a flowchart which shows the operation | movement content of the principal part of the automatic steering control part 101 by Embodiment 1 of this invention. It is a map of the motor current and rotation speed limit value by Embodiment 1 of this invention. It is a flowchart which shows the detailed content of step S4 by Embodiment 1 of this invention. It is a block diagram of position control by Embodiment 1 of this invention. It is a flowchart which shows the operation | movement content of the principal part of the automatic steering control part 101 by Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Steering wheel, 2 Steering shaft, 3 Steering wheel, 4 Torque sensor, 5 Motor, 6 Deceleration mechanism, 7 Angle sensor, 8 Vehicle speed sensor, 9 Current sensor, 10 Control unit, 11 Target steering angle calculator, 12 Battery voltage sensor , 101 automatic steering control unit, 102 electric power assist control unit, 103 current control unit.

Claims (7)

A motor for turning the steered wheels;
Motor current detecting means for detecting the current of the motor;
A target rudder angle setting means for setting a target rudder angle based on calculation of a target rudder angle of the steered wheels or reception from the outside;
A turning angle detection means for detecting a turning angle of the turning wheel;
Motor control means for controlling the motor 5 by calculating a target current of the motor so that the turning angle follows the target steering angle;
The automatic steering control device, wherein the motor control means sets a motor rotation speed limit value based on the motor current detected by the motor current detection means to limit the rotation speed of the motor. The automatic steering control device according to claim 1,
Battery voltage detecting means for detecting a battery voltage that is a power supply voltage for driving the motor;
The automatic steering control device, wherein the motor control means sets a motor rotation speed limit value based on the motor current and the battery voltage to limit the rotation speed of the motor. The automatic steering control device according to claim 1,
A steering angular acceleration detecting means for detecting or calculating a steering angular acceleration of the steered wheels;
An automatic steering control device, wherein the motor control means sets a motor rotation speed limit value based on the motor current and the turning angular acceleration to limit the rotation speed of the motor. In the automatic steering control device according to any one of claims 1 to 3,
The motor control means calculates a target rudder angular velocity from the target rudder angle and the previous value of the target rudder angle 2, limits the target rudder angular velocity with the motor rotation speed limit value, and calculates the target rudder from the limited target rudder angular velocity. An automatic steering control device that calculates a steering angle 2 and controls a motor so that the turning angle follows the target steering angle 2. In the automatic steering control device according to claim 4,
The automatic steering control device, wherein the motor control means makes an initial value of the target steering angle 2 coincide with the turning angle when automatic steering control is started. In the automatic steering control device according to any one of claims 1 to 3,
The motor control means calculates a target rudder angular speed based on the target rudder angle and the steered angle, limits the calculated target rudder angular speed with the motor rotation speed limit value, and based on the steered angle. A steering angular velocity is calculated, a target current is calculated from a deviation between the limited target steering angular velocity and the steering angular velocity, and the motor is controlled so that the steering angular velocity follows the target steering angular velocity. Automatic steering control device. In the automatic steering control device according to any one of claims 1 to 6,
An automatic steering control device, wherein the motor control means determines an abnormality in current control based on a deviation between a target current of the motor and a motor current detected by the motor current detection means.

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