JP2010208490A - Vehicle steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a deviation between a neutral position of a steering wheel and a vehicle straight advance position of a steered wheel while reducing a load on a battery, when a battery voltage drops. <P>SOLUTION: A vehicle steering control device 10 is provided on a steering shaft 14 connected to the steering wheel 12, and includes a VGRS actuator 20 which gives a turning angle to the steered wheel 18. A VGRS-ECU 22 fixes a rotation angle of the VGRS actuator 20, when it is detected that a voltage of the battery 28 is lowered less than a specific first threshold voltage. The deviation between the neutral position of the steering wheel 12 and the vehicle straight advance position of the steered wheel 18, which is caused when a rotation angle of the VGRS actuator 20 is fixed, is corrected while the steering wheel 12 is returned. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering control device, and more particularly to a vehicle steering control device capable of controlling a steering gear ratio.

  Conventionally, in a vehicle such as an automobile, a transmission ratio (steering gear ratio) of a steered wheel to a steered angle input to a steering wheel by a driver using a driving unit such as an actuator that rotates a steering shaft. A variable staying gear ratio variable control (VGRS: Variable Gear Ratio Steering) system is known.

  In such a VGRS system, the steering gear ratio is increased at low vehicle speeds so that the steered wheels are steered greatly by a small steering wheel operation (quick state). Conversely, at high vehicle speeds, the steering gear ratio is reduced to prevent the steered wheels from being steered greatly even when a large steering wheel operation is performed (slow state).

  By the way, the actuator in the VGRS is driven by receiving power from a battery mounted on the vehicle. The battery supplies power not only to the VGRS actuator but also to an engine, an electric power steering device, and the like. Yes. Therefore, the VGRS system needs to prevent the occurrence of an undesirable situation in which the engine stops when the battery voltage drops. Therefore, for example, Patent Document 1 discloses a technique in which VGRS is shifted to a slow state and stopped when the power supply voltage becomes a predetermined voltage or lower.

JP 2001-287657 A

  However, as in the VGRS system described in Patent Document 1, if the VGRS system is stopped due to a decrease in battery voltage while the actuator is rotating at a certain angle, the neutral position of the steering wheel and the vehicle straight position of the steered wheel There is a problem that a gap occurs between them. When this deviation occurs, the driver may feel uncomfortable with the steering wheel operation. If it is attempted to supply current to the actuator in order to eliminate this deviation in a state where the battery voltage is decreasing, the load on the battery will increase and the battery voltage will decrease further.

  The present invention has been made in view of such circumstances, and its purpose is to reduce the load applied to the battery when the battery voltage is reduced, and between the neutral position of the steering wheel and the straight traveling position of the steered wheels. An object of the present invention is to provide a vehicle steering control device capable of correcting a deviation.

  In order to solve the above-described problem, a vehicle steering control device according to an aspect of the present invention includes a drive unit that is provided on a steering shaft that is coupled to a steering handle and that provides a turning angle to a steered wheel. A steering control unit for detecting a steering state of the steering handle; a voltage detection unit for detecting a voltage of a battery for supplying power to the driving unit; and a voltage of the battery for a predetermined drive. It is detected that the steering wheel is turned back by the rotation angle fixing means for fixing the rotation angle of the driving means and the steering state detecting means when it is detected that the voltage is lower than the means fixing voltage. And a correction means for correcting a deviation between a neutral position of the steering wheel and a straight traveling position of the steered wheel, which is generated when the rotation angle of the driving means is fixed.

  According to this aspect, when it is detected that the steering wheel is turned back, the position between the neutral position of the steering wheel that is generated when the rotation angle of the driving unit is fixed and the straight traveling position of the steered wheel is between The deviation is corrected. In general, since the self-aligning torque acts on the steered wheels, the load torque necessary for the steered wheels in the turning-back direction is smaller than that in the case of the steered-in direction. That is, the electric power required for turning in the turning-back direction of the steered wheels is smaller than in the case of turning in the turning-up direction. Therefore, according to this aspect, it is possible to correct the shift between the neutral position of the steering wheel and the straight traveling position of the steered wheel while suppressing the load on the battery.

  The correction means may change the shift correction speed in accordance with a steering angular speed of the steering wheel. The correction means may increase the shift correction speed as the steering angular speed of the steering wheel increases. In this way, by changing the correction speed in accordance with the steering state of the steering wheel, it is possible to quickly correct the deviation between the neutral position of the steering wheel and the straight traveling position of the steered wheels.

  You may further provide the estimation means which estimates the load torque of the said drive means. The correction means may increase the shift correction speed when the load torque is estimated to be small. When it is estimated that the load torque is small, the power consumption can be suppressed even if the correction speed of deviation is increased. Therefore, in this case, the shift can be corrected quickly while suppressing the load on the battery.

  When the voltage of the battery recovers to a return voltage higher than the driving means fixed voltage, the rotation angle of the driving means may be released and the normal control may be restored. If normal control is restored when the driving voltage of the battery reaches the driving means fixed voltage, the battery voltage again falls below the driving means fixing voltage by supplying current to the driving means, and the rotation angle of the driving means is fixed. . That is, the rotation angle fixing of the driving means and the normal control are repeated. Thus, normal control can be performed in a stable state by returning to normal control when the battery voltage recovers to a return voltage higher than the drive means fixed voltage.

  ADVANTAGE OF THE INVENTION According to this invention, when battery voltage falls, the shift | offset | difference between the neutral position of a steering wheel and the vehicle straight drive position of a steered wheel can be correct | amended, suppressing the load concerning a battery.

It is a figure for demonstrating the steering control apparatus for vehicles which concerns on embodiment of this invention. It is a figure which shows the flowchart for demonstrating the flow of control of the steering control apparatus for vehicles which concerns on this Embodiment. FIG. 3 is a flowchart for explaining control for correcting a deviation between a neutral position of a steering wheel and a straight traveling position of a steered wheel generated in the control flow of FIG. 2. 10 is a flowchart for explaining a modified example of control for correcting a deviation between a neutral position of a steering wheel and a straight traveling position of a steered wheel. It is a figure for demonstrating switching of the control mode of the steering control apparatus for vehicles which concerns on this Embodiment.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining a vehicle steering control apparatus 10 according to an embodiment of the present invention.

  The steering handle 12 is a steering input means that is rotated by the driver, and transmits the rotation to the connected steering shaft 14. The steering shaft 14 further transmits the steering angle input to the steering handle 12 to the rack shaft 16 by a well-known rack and pinion method. The input steering angle is transmitted to the rack shaft 16 as a lateral movement by a pinion mechanism (not shown), thereby turning the steered wheels 18.

  The steering shaft 14 is provided with a VGRS actuator 20 as drive means for rotating the steering shaft 14 independently of the steering by the driver and in addition to the steering.

  The VGRS actuator 20 is driven and controlled by a VGRS control device (hereinafter referred to as VGRS-ECU) 22. The VGRS-ECU 22 is configured as a microprocessor including a CPU, and includes a ROM that stores various programs, a RAM that temporarily stores data, an input / output port, a communication port, and the like in addition to the CPU.

  For example, the VGRS actuator 20 rotates the steering shaft 14 based on the steering angle detected by the steering angle sensor 24 that detects the steering angle input to the steering handle 12 and the vehicle speed acquired from the vehicle speed sensor 26. The VGRS-ECU 22 communicates information on the rotation angle of the VGRS actuator 20 with the VGRS actuator 20.

  The VGRS-ECU 22 is supplied with electric power from a battery 28 mounted on the vehicle. The VGRS-ECU 22 has a voltage detection unit that detects a voltage input from the VGRS-ECU 22. The battery 28 is also supplied with power to an engine, an electric power steering device, and the like not shown in FIG.

  FIG. 2 is a flowchart illustrating the control flow of the vehicle steering control apparatus 10 according to the present embodiment. The control according to the flowchart shown in FIG. 2 is repeatedly executed at predetermined time intervals.

  First, the VGRS-ECU 22 reads the battery voltage Vpig of the battery 28 from the voltage detector, the steering angle MA from the steering angle sensor 24, and the current rotation angle θact of the VGRS actuator 20 from the VGRS actuator 20 (S10).

  Next, the VGRS-ECU 22 determines whether or not the battery voltage Vpig is greater than the first threshold voltage Va (S12). When the battery voltage Vpig falls below this first threshold voltage Va, each control means (for example, engine control) that controls equipment mounted on the vehicle when the vehicle steering control device 10 is to be normally operated. The voltage that causes trouble in the operation of the device and the electric power steering control device), for example, is set to about 10V.

  When the battery voltage Vpig is larger than the first threshold voltage Va (Y in S12), the VGRS-ECU 22 performs normal VGRS control. In the normal VGRS control, first, the VGRS-ECU 22 calculates the target angle θref of the VGRS actuator 20 as the product of the steering angle MA and the VGRS acceleration rate Kv (S14). Note that the VGRS acceleration rate Kv is calculated according to the vehicle speed based on a map indicating the relationship between the vehicle speed and the acceleration rate stored in advance. Next, the VGRS-ECU 22 calculates the target voltage Vref by multiplying the target angle θref by a predetermined voltage conversion coefficient K (S16). Thereafter, the VGRS-ECU 22 drives the VGRS actuator 20 by applying the target voltage Vref to the VGRS actuator 20 (S18).

  On the other hand, when the battery voltage Vpig is equal to or lower than the first threshold voltage Va (N in S12), the VGRS-ECU 22 determines whether or not the battery voltage Vpig is larger than the second threshold voltage Vb (S20). The second threshold voltage Vb has a problem in the operation of each control means of the vehicle when the normal VGRS control is performed. However, the second threshold voltage Vb is a control that supplies power sufficient to maintain the current rotation angle θact of the VGRS actuator 20. This is a voltage that does not hinder the operation of each control means, and is set to about 9 V, for example.

  When the battery voltage Vpig is greater than the second threshold voltage Vb (Y in S20), the VGRS-ECU 22 sets the voltage suppression control flag to 1 (S21). This voltage suppression control flag is a flag for control described later in FIG. 3 or FIG. Next, the VGRS-ECU 22 sets the target angle θref of the VGRS actuator 20 to the current rotation angle θact (S22). That is, the target angle θref is set so that the current rotation angle θact is fixed. Thereafter, the VGRS-ECU 22 calculates the target voltage Vref by multiplying the target angle θref by a predetermined voltage conversion coefficient K (S16), and applies the target voltage Vref to the VGRS actuator 20, whereby the rotation angle θact is calculated. It is fixed (S18).

  In the case where the battery voltage Vpig is smaller than the second threshold voltage Vb (N in S20), if current is supplied to the VGRS actuator 20, the operation of each control unit of the vehicle is hindered due to the voltage drop. The locking device that has not been operated is activated, and the rotation of the VGRS actuator 20 is mechanically blocked (S24).

  As described above, the control flow shown in FIG. 2 is configured such that when a decrease in the battery voltage Vpig is detected, the rotation angle θact of the VGRS actuator 20 at that time is fixed. Thereby, the increase in the shift | offset | difference between the neutral position of the steering handle 12 and the vehicle straight drive position of the steered wheel 18 can be suppressed. Further, the electric power required for maintaining the current rotation angle θact may be smaller than that required when the rotation angle of the VGRS actuator 20 is changed. Therefore, the load applied to the battery 28 can be minimized.

  FIG. 3 is a flowchart for explaining the control for correcting the shift between the neutral position of the steering wheel and the straight traveling position of the steered wheels that occurs in the control flow of FIG. The control according to the flowchart shown in FIG. 3 is repeatedly executed every predetermined time.

  First, the VGRS-ECU 22 determines whether or not the voltage suppression control flag is 1 (S30). When the voltage suppression control flag is not 1 (N in S30), the VGRS-ECU 22 waits until the voltage suppression control flag becomes 1.

  When the voltage suppression control flag is 1 (Y in S30), the battery voltage Vpig of the battery 28 from the voltage detection unit, the steering angle MA and the steering angular velocity dMA from the steering angle sensor 24, and the current VGRS actuator 20 from the VGRS actuator 20 Is read (S32).

  When the voltage suppression control flag is 1, as described in the flowchart of FIG. 2, the rotation angle θact of the VGRS actuator 20 rotates when the battery voltage Vpig is equal to or lower than the first threshold voltage and higher than the second threshold voltage. It is fixed at an angle (referred to as a fixed rotation angle θact (0)). In the control flow of FIG. 3, this fixed rotation angle θact (0) is preferably corrected, that is, the fixed rotation angle θact (0) is brought close to zero, and the neutral position of the steering wheel 12 and the straight wheel of the steered wheels 18 travel straight. Eliminate deviations from the position.

  Next, the VGRS-ECU 22 determines whether or not the steering angle MA is greater than 0 (S34). In the present embodiment, the steering angle sensor 24 outputs a positive value when the steering handle 12 is turned to the right, and outputs a negative value when the steering wheel 12 is turned to the left. .

  When the steering angle MA is greater than 0, that is, when the steering handle 12 is turned to the right (Y in S34), the VGRS-ECU 22 determines whether the steering angular velocity dMA of the steering handle 12 is greater than 0 (S36). ). The steering angular velocity may be read directly from the steering angle sensor 24, or may be calculated by the VGRS-ECU 22 based on the steering angle MA read from the steering angle sensor 24.

  When the steering angular velocity dMA is greater than 0, that is, when the steering angular velocity dMA is increased toward the steering wheel end (Y in S36), the VGRS-ECU 22 sets the target angle θref of the VGRS actuator 20 to the fixed rotation angle θact (0). (S38). On the other hand, when the steering angular speed dMA is smaller than 0, that is, when the steering angular speed dMA is turned back toward the neutral position of the steering handle 12 (N in S36), the VGRS-ECU 22 determines the predetermined rotation angle θact of the VGRS actuator 20 A value obtained by subtracting the correction angle θoff is set as the target angle θref of the VGRS actuator 20 (S44). In the present embodiment, the correction angle θoff is a constant and is set to about 10 °, for example. Thus, by setting the value obtained by subtracting the correction angle θoff from the rotation angle θact as the target angle θref, the rotation angle of the fixed VGRS actuator 20 can be reduced. That is, it is possible to reduce the deviation between the neutral position of the steering wheel 12 and the straight traveling position of the steered wheels 18. After the target angle θref of the VGRS actuator 20 is set, the VGRS-ECU 22 calculates the target voltage Vref by multiplying the target angle θref by a predetermined voltage conversion coefficient K (S40), and the VGRS actuator 20 receives the target voltage. By applying Vref, the rotation angle of the VGRS actuator 20 is controlled (S42).

  On the other hand, when the steering angle MA is smaller than 0, that is, when the steering wheel 12 is turned to the left (N in S34), the VGRS-ECU 22 determines whether or not the steering angular velocity dMA of the steering wheel 12 is smaller than 0. (S46).

  When the steering angular velocity dMA is smaller than 0, that is, when the steering angular velocity dMA is increased toward the steering wheel end (Y in S46), the VGRS-ECU 22 sets the target angle θref of the VGRS actuator 20 to the fixed rotation angle θact (0). (S48). On the other hand, when the steering angular velocity dMA is larger than 0, that is, when the steering wheel 12 is turned back toward the neutral position of the steering handle 12 (N in S46), the VGRS-ECU 22 determines a predetermined value from the current rotation angle θact of the VGRS actuator 20. A value obtained by subtracting the correction angle θoff is set as the target angle θref of the VGRS actuator 20 (S50). After the target angle θref of the VGRS actuator 20 is set, the VGRS-ECU 22 calculates the target voltage Vref by multiplying the target angle θref by a predetermined voltage conversion coefficient K (S40), and the VGRS actuator 20 receives the target voltage. By applying Vref, the rotation angle of the VGRS actuator 20 is controlled (S42).

  Thus, in the control flow shown in FIG. 3, the neutral position of the steering handle 12 generated when the rotation angle of the VGRS actuator 20 is fixed when the steering handle 12 is turned back toward the neutral position. And the deviation of the steered wheel 18 from the straight vehicle position is corrected. In general, since the self-aligning torque acts on the steered wheels 18, the load torque required to steer the steered wheels 18 in the switchback direction is smaller than that in the case of steering in the additional direction. That is, the electric power required for the turning of the steered wheels 18 in the switchback direction is smaller than that in the case of the steering in the additional turning direction. Therefore, according to the control flow shown in FIG. 3, it is possible to correct the deviation between the neutral position of the steering wheel 12 and the straight traveling position of the steered wheel 18 while suppressing the load on the battery 28.

  FIG. 4 is a flowchart for explaining a modified example of the control for correcting the deviation between the neutral position of the steering wheel and the straight traveling position of the steered wheels. The flowchart in FIG. 4 is the same as the flowchart shown in FIG. 3 except for S44 and S50, so only S44 and S50 will be described.

  In the control flow of FIG. 3, the correction angle θoff subtracted from the current rotation angle θact of the VGRS actuator 20 is a constant in S44 and S50. However, in the control flow of FIG. The variable varies depending on dMA. Specifically, a value obtained by multiplying the steering angular velocity dMA by a predetermined offset correction coefficient Kst is subtracted from the current rotation angle θact, and this is set as the target angle θref.

  By setting the target angle θref in this way, the speed for correcting the deviation between the neutral position of the steering wheel 12 and the straight traveling position of the steered wheel 18 is changed according to the steering angular speed dMA of the steering wheel 12. Can do. More specifically, by setting the target angle θref in this manner, the deviation correction speed can be increased as the steering angular speed dMA of the steering handle 12 is higher. In this way, by changing the correction speed according to the steering state of the steering handle 12, the deviation between the neutral position of the steering handle 12 and the straight traveling position of the steered wheels 18 can be quickly corrected.

  As a modification of the control flow shown in FIG. 4, the VGRS-ECU 22 estimates the load torque of the VGRS actuator 20 from the torque sensor value in the electric power steering device, and when the load torque is estimated to be small, the steering handle 12 The correction speed of the deviation between the neutral position and the straight traveling position of the steered wheel 18 may be increased. That is, when it is estimated that the load torque is small, the value of the correction angle θoff that is subtracted from the current rotation angle θact is set high. When it is estimated that the load torque of the VGRS actuator 20 is small, the power consumption can be suppressed even if the correction speed of deviation is increased. Therefore, in this case, the shift can be corrected quickly while suppressing the load on the battery 28.

  FIG. 5 is a diagram for explaining switching of the control mode of the vehicle steering control apparatus 10 according to the present embodiment.

  As described above, in the vehicle steering control device 10, when the battery voltage Vpig becomes equal to or lower than the first threshold voltage Va, the normal control is switched to the control for fixing the target angle θref of the VGRS actuator 20. When the battery voltage Vpig becomes equal to or lower than the second threshold voltage Vb, the lock device is activated and the system is mechanically stopped.

  Here, consideration will be given to switching to normal control when the battery voltage Vpig is recovered. If the normal control is restored when the battery voltage Vpig reaches the first threshold voltage Va, the battery voltage Vpig again falls below the first threshold voltage Va due to the current supply to the VGRS actuator 20, and the rotation angle of the VGRS actuator 20 Will be fixed. That is, the rotation angle fixing of the VGRS actuator 20 and the normal control are repeated. Therefore, as shown in FIG. 5, normal control can be performed in a stable state by returning to normal control when the battery voltage Vpig recovers to a recovery voltage Vc higher than the first threshold voltage Va. Since the appropriate return voltage Vc differs from vehicle to vehicle, it can be set as appropriate through experiments and simulations. For example, when the first threshold voltage Va is set to 10V and the second threshold voltage Vb is set to 9V, the return voltage Vc can be set to about 11V.

  The present invention has been described above based on the embodiment. It should be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 Steering control apparatus for vehicles, 12 Steering handle, 14 Steering shaft, 16 Rack shaft, 18 Steering wheel, 20 VGRS actuator, 22 VGRS-ECU, 24 Steering angle sensor, 26 Vehicle speed sensor, 28 Battery

Claims (5)

A vehicle steering control device provided on a steering shaft connected to a steering handle and provided with a driving means for giving a turning angle to a steered wheel,
Steering state detection means for detecting the steering state of the steering wheel;
Voltage detecting means for detecting a voltage of a battery for supplying power to the driving means;
A rotation angle fixing means for fixing a rotation angle of the driving means when it is detected that the voltage of the battery is equal to or lower than a predetermined driving means fixing voltage;
When the steering state detecting means detects that the steering handle is turned back, the neutral position of the steering handle that is generated when the rotation angle of the drive means is fixed and the vehicle of the steered wheels goes straight on the vehicle. Correction means for correcting the deviation between the position,
A vehicle steering control device comprising:   2. The vehicle steering control device according to claim 1, wherein the correction unit changes a correction speed of the shift in accordance with a steering angular speed of the steering handle.   The vehicle steering control device according to claim 2, wherein the correction means increases the shift correction speed as the steering angular speed of the steering wheel increases. An estimation unit for estimating a load torque of the driving unit;
2. The vehicle steering control device according to claim 1, wherein when the load torque is estimated to be small, the correction unit increases the shift correction speed. 3.   5. The system according to claim 1, wherein when the voltage of the battery recovers to a return voltage higher than the fixed voltage of the driving means, the rotation angle of the driving means is released and the normal control is restored. The vehicle steering control device described in 1.

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