JP5014309B2 - Automatic vehicle steering system - Google Patents

Description

  The present invention relates to an apparatus for automatically steering a vehicle.

  Conventionally, an automatic steering apparatus for automatically steering a vehicle has been proposed. For example, it is desired to use an automatic steering apparatus when automatically placing a garage or parallel parking.

In the following Patent Document 1, an engine is instructed to perform a forward operation to a driver during automatic steering, and as a result, a predetermined steering is automatically performed according to the distance moved, and the vehicle speed is set to a predetermined value or less. An automatic steering system for controlling the vehicle is disclosed.
JP-A-9-193691

  In automatic steering control using a steering actuator realized by an electric motor, in order to make the actual rudder angle coincide with the target rudder angle, the electric motor is adjusted so that the actual current coincides with the command current (target current) corresponding to the target rudder angle. Control and thereby steer the wheels.

The electrical characteristics of the electric motor are simply expressed as follows. In this equation, the motor terminal voltage is VM, the inductance is L, the resistance is R, the induced voltage constant is k, the rotational speed is N, the current (actual current) is i, and the time is t.
VM = L · (di / dt) + R · i + k · N≈R · i + k · N
Therefore, the current i is expressed as i = (VM−k · N) / R.

  The inter-terminal voltage VM is up to the battery voltage (almost constant) even when applied to the maximum, and the resistance R can be regarded as an almost constant constant. Therefore, the current i that can be supplied to the motor is determined by the rotational speed N of the motor. . When the wheels are steered quickly by automatic steering, it is necessary to rotate the electric motor at a high speed. However, as shown in the above formula, the current i is limited as the motor speed N increases.

  Referring now to FIG. 9, there are shown examples of the transition of the target steering angle and the actual steering angle of the steering angle and the command current and the actual current of the electric motor in the conventional automatic steering control. With respect to the steering angle, turning right is positive with respect to a predetermined reference position, and turning left is negative. Regarding the current, the current for turning in the right direction is positive, and the current for turning in the left direction is negative.

  At time t1, a change in the target rudder angle is started to steer the wheels. The change speed of the target rudder angle is increased in order to perform fast turning. When the target rudder angle changes, a deviation occurs between the target rudder angle and the actual rudder angle. In order to converge this deviation, the magnitude (absolute value) of the command current increases. However, for the reasons described above, there is a limit to the actual current that can actually be supplied to the motor. Therefore, from time t1 to t2, the actual current can follow the command current, but after time t2, the actual current cannot follow the command current. As a result, the deviation between the target rudder angle and the actual rudder angle increases, and the magnitude of the command current is further increased as shown in region 201 in an attempt to reduce this deviation.

  However, the instruction current is determined to have an allowable value indicating a limit current value provided so as not to break the motor (in this embodiment, only an allowable current value for turning to the left is shown). Therefore, the instruction current is stuck to the allowable value as shown at times t3 to t4 due to this increase.

  When the target rudder angle changes to a value to be reached, the target rudder angle does not change, so that the deviation between the actual rudder angle and the target rudder angle becomes small as shown in the vicinity of time t4, and the actual rudder angle is reduced. The angle catches up with the target rudder angle. Therefore, as shown in the region 203, the magnitude of the instruction current also decreases, but the instruction current starts to decrease from the state where it sticks to the allowable value, so the magnitude of the actual current increases in an attempt to match the instruction current. to continue. That is, the magnitude of the actual current continues to increase despite the magnitude of the command current decreasing. For this reason, the magnitude (absolute value) of the actual rudder angle continues to increase.

  If the target rudder angle is set near a predetermined maximum rudder angle in order to turn the vehicle in a small turn, the actual rudder angle will increase as shown in region 205 due to the continuous increase of the actual current as described above. May exceed the target rudder angle and reach the maximum rudder angle (in this embodiment, only the maximum rudder angle when turning to the left is shown). The steering mechanism for turning the wheels is provided with a mechanical stopper according to the maximum steering angle, and steering beyond the maximum steering angle of the steering handle is prohibited. When the actual rudder angle reaches the maximum rudder angle, the turning mechanism comes into contact with the stopper. The greater the change speed of the actual rudder angle, the greater the impact force that abuts. Not only is there a possibility that impact noise is generated, thereby reducing the merchantability, but if the impact force is strong, the steering mechanism may be damaged.

  In order to prevent such an impact, conventionally, the maximum steering angle is controlled even if the change speed of the target rudder angle is controlled or the actual rudder angle exceeds the target rudder angle within a range where the actual current can follow the command current. Therefore, the range in which the target rudder angle changes needs to be set to a range away from the maximum rudder angle. In either case, the wheel is steered slowly or the steering angle itself to be changed is reduced, which can be an obstacle for turning the vehicle in a small turn.

  Therefore, there is a demand for an automatic steering control that enables the vehicle to turn in a small turn while more reliably preventing the above-described impact.

  According to one aspect of the present invention, an automatic steering device for a vehicle uses a steering actuator for steering a vehicle wheel and a steering actuator based on a target rudder angle set in advance according to a target movement locus of the vehicle to a target position. An instruction current calculation means for calculating an instruction current to be energized; and a control means for controlling the steering actuator so that the actual current supplied to the steering actuator converges to the instruction current. When the magnitude of the deviation is greater than or equal to a predetermined value, the control means holds the instruction current at the value previously calculated by the instruction current calculation means, and controls the steering actuator using the instruction current of the held value. .

  According to the present invention, when the magnitude of the deviation between the command current and the actual current becomes large, that is, in a state where the actual current does not follow the command current, the command current is not updated without the previous value. Therefore, it is possible to prevent the deviation from the actual current from further increasing due to a further change in the instruction current. Therefore, the actual current can coincide with the indicated current at an early stage. Since the actual current can follow the command current well, even if the target rudder angle is set near the maximum rudder angle, the actual rudder angle overshoots the target rudder angle and reaches the maximum rudder angle. Can be prevented. Therefore, it is possible to more reliably prevent impact sound and damage to the steering mechanism that may occur due to the actual steering angle reaching the maximum steering angle.

  In one embodiment of the present invention, whether or not the command current having the value calculated by the command current calculation means is changed in a direction to increase the magnitude of the deviation between the command current and the actual current. When the determination means determines that the indicated current of the value calculated this time by the determination means is to be changed in the direction of increasing the magnitude of the deviation, the control means is further calculated previously. The indicated current is held at the specified value.

  According to the present invention, when it is determined that the magnitude of the deviation between the command current and the actual current is increased, the command current is held at the previous value, and thus when the magnitude of the deviation is determined to be decreased. Can tolerate a change in the indicated current. Therefore, it is possible to control the instruction current so that the deviation does not increase when the magnitude of the deviation increases, and the deviation becomes smaller when the magnitude of the deviation decreases. Therefore, finer control can be realized.

  Other features and advantages of the present invention will be apparent from the detailed description that follows.

  Next, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an automatic steering apparatus for a vehicle according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of a back parking / left mode, and FIG. 3 is a mode selection switch and an automatic parking start switch. FIG.

  As shown in FIG. 1, the vehicle V includes a pair of front wheels Wf, Wf and a pair of rear wheels Wr, Wr. Steering handle 1 and front wheels Wf and Wf, which are steered wheels, are rotated integrally with steering handle 1, steering shaft 2, pinion 3 provided at the lower end of steering shaft 2, rack 4 meshing with pinion 3, and rack 4 Are connected by left and right tie rods 5, 5 provided at both ends, and left and right knuckles 6, 6 connected to tie rods 5, 5. A steering actuator 7 made of an electric motor is connected to the steering shaft 2 via a worm gear mechanism 8 in order to assist the driver to operate the steering handle 1 or to perform automatic steering for parking, which will be described later.

  The steering control device 21 includes a control unit 22 and a storage unit 23. The control unit 22 includes an actual steering angle sensor (detection means) Sa that detects an actual steering angle θ that is a rotation angle of the steering handle 1, and a steering. Steering torque sensor (detection means) Sb for detecting the steering torque T of the steering wheel 1, wheel rotation angle sensors (detection means) Sc for detecting the rotation angles of the wheels Wf, Wf; Wr, Wr, and operation of the brake pedal 9 Brake operation amount detection means Sd for detecting the amount, and shift range detection means for detecting the shift range (“D” range, “R” range, “N” range, “P” range, etc.) selected by the select lever 10 A signal from Se is input.

  The steering control device 21 can be realized by an electronic control unit (ECU) which is a computer including a central processing unit (CPU) and a memory. In this case, a computer program that realizes the function of the control unit 22 is stored in a memory, and the CPU reads and executes the program. The storage unit 23 can be realized in a memory. Alternatively, the steering control device 21 may be realized by a combination of hardware and software (computer program).

  As is apparent when referring to FIG. 3, the mode selection switch Sf and the automatic parking start switch Sg operated by the driver are connected to the control unit 22. The mode selection switch Sf has four types of parking modes to be described later: back parking / right mode (right back), back parking / left mode (left back), parallel parking / right mode (right vertical), and parallel parking / left mode. Four buttons that are operated when selecting one of (left column) are provided. The automatic parking start switch Sg is operated when starting automatic parking in any mode selected by the mode selection switch Sf. These switches can be provided, for example, on the instrument panel of the vehicle V so that the driver can operate the switches.

  In the storage unit 23, the relationship between the target rudder angle θref with respect to the movement distance X of the vehicle V according to the data for each of the four types of parking modes, that is, the target movement locus set for parking at the target position, It is stored in advance as a table (see (b) of FIG. 2). The moving distance X of the vehicle V is calculated by adding the rotation angles of the wheels Wf, Wf; Wr, Wr detected by the wheel rotation angle sensor Sc ... to the known outer peripheral lengths (tire radii) of the wheels Wf, Wf; Wr, Wr. It is obtained by multiplication. For the calculation of the movement distance X, the high selection value (maximum value), the low selection value (minimum value), or the average value of the outputs of the wheel rotation angle sensors Sc can be used.

  The control unit 22 controls the operation of the steering actuator 7 based on the signals from the detection means Sa to Se and the switches Sf and Sg and the parking mode data stored in the storage unit 23, and the liquid crystal monitor, The operation stage teaching device 11 is provided with a speaker, a lamp, a chime, a buzzer, etc., and performs various notifications to the driver.

    Next, the operation of the embodiment of the present invention having the above-described configuration will be described. In normal times when automatic parking is not performed (when the mode selection switch Sf is not operated), the steering control device 21 is in an electric power steering (EPS) mode in which it functions as a general power steering control device. Specifically, when the driver operates the steering handle 1 to turn the vehicle V, the steering torque sensor Sb detects the steering torque T input to the steering handle 1, and the control unit 22 determines the steering torque T. Used to control the driving of the steering actuator 7. As a result, the left and right front wheels Wf, Wf are steered by the driving force of the steering actuator 7, and the driver's steering operation is assisted.

    Next, the contents of the automatic steering control mode in which the steering control device 21 functions as an automatic steering device will be described by taking the back parking / left mode (the mode in which the vehicle V is parked while backing to the parking position on the left side of the vehicle V) as an example. When left-back parking is performed, the target parking position is the center of the parking space, so that the driver can move the vehicle to the end X1 of the entrance side Pe of the parking space P as shown at position A1 in FIG. The vehicle V is parked so that the start position mark M provided in advance in V is visually aligned and the entrance side Pe of the parking space P is perpendicular to the line in the vehicle width direction passing through the vehicle start position mark M. Let

  When the driver selects left back parking with the mode selection switch Sf, the selected switch is lit, and the teaching device 11 informs the driver that “left back parking is in progress”. If there is no mistake in the selected parking mode, the driver releases both hands from the steering wheel 1 and turns on the automatic steering start switch Sg. These switch inputs must satisfy the conditions that the vehicle speed is zero, the brake 9 is operated, and the actual steering angle of the steering wheel 1 is within a predetermined range (for example, ± 20 degrees). It will be ignored. If these conditions are satisfied, the switch input is accepted and the mode shifts from the electric power steering (EPS) mode to the automatic steering control mode. The steering actuator 7 that has been operating as the electric power steering is controlled by the control unit 22 so as to realize automatic steering until the automatic steering control mode ends.

  Since the automatic steering start switch Sg is lit and the teaching device 11 informs the user that “Please advance slowly” and displays the advance, the wheel rotation angle sensor Sc when the driver moves the vehicle forward by releasing the brake 9. The rotation angle Θ of the wheel is detected from the integration of the number of output pulses. From the wheel rotation angle Θ and the wheel tire radius r, the vehicle travel distance X = rΘ is calculated. The control unit 22 reads the target steering angle θref of the handle 1 corresponding to the movement distance X from the target movement locus table for the left back parking mode stored in the storage unit 23 as shown in FIG.

  The control unit 22 automatically controls the steering wheels Wf and Wf by controlling the steering actuator 7 so that the actual steering angle θ detected by the actual steering angle sensor Sa becomes equal to the read target steering angle θref. Steer.

  In the case of this left back parking, the target movement trajectory set in the table of FIG. 2 (b) is the forward straight traveling part of the distance a, the right steering part of the distance b (running while maintaining the state steered to the right). , A forward straight traveling portion at a distance c, a left steered portion at a distance d (running while maintaining a state steered to the left), and a backward straight traveling portion at a distance e.

  First, when the vehicle V moves forward from position A1 to A2, steering to the right side is performed. When the vehicle moves forward to a position where the traveling direction changes from forward to backward, that is, a shift change position (position A2 in FIG. 2A), the teaching device 11 notifies and shifts “Please stop and change gear”. There is a change indication. The driver stops the vehicle and changes the shift position from forward to backward. When this is detected by the shift range detection means Se, the teaching device 11 gives a notification and a reverse display of “Please move backward slowly”, so the driver starts moving backward. In addition, it is possible to store the distance that was actually overrun before the position where the shift change was made, and when the vehicle moves backward, the overrange distance is canceled and the shift change position is overrun A shift in the parking position can be prevented.

  When the vehicle V moves backward from the position A2 to the position A3, the steering to the left side is performed. When the vehicle is retracted to the parking position (position A3 in FIG. 2A) by automatic steering, a notification and a stop display are displayed from the teaching device, “Left back parking is complete, please stop”. When it is detected from the output of the wheel rotation angle sensor Sa that the vehicle has stopped by the driver, or when the shift range detecting means Se detects that the shift lever is operated from the reverse position, the automatic steering control mode is finish.

  In addition to the normal end as described above, when the automatic steering start switch Sg is turned off, when the vehicle speed satisfies the end determination condition, the driver operates the steering wheel 1 and the steering torque T satisfies the end determination condition. Even in such a case, after teaching that “automatic steering control is stopped”, automatic steering is immediately stopped. Accordingly, the electric power steering mode is entered, and the steering actuator 7 operates as an electric power steering to assist the driver's steering operation.

  In this embodiment, the start position of the automatic steering is such that the start position mark M is aligned with the end portion X1 of the entrance side Pe of the parking space P as in the position A1, but the position where the mark is aligned is the entrance of the parking space P. The other end X2 of the side Pe or the center of the entrance side Pe (the center of X1 and X2) may be set as the start position. In accordance with this start position, the target movement trajectory table stored in the storage unit 23 is created in advance. Further, a door mirror or the like may be used instead of the mark M.

  FIG. 4 shows a more detailed configuration of the steering control device 21. The control unit 22 includes an EPS command current calculation unit 51, a command current switching unit 53, and a current control unit 55. The EPS command current calculation unit 51 calculates a command current (target current) to be supplied to the steering actuator 7 composed of an electric motor for the electric power steering (EPS) mode. Specifically, the EPS command current calculation unit 51 is based on the steering torque T detected by the steering torque sensor Sb and the detected vehicle speed (which can be detected by a vehicle speed sensor (not shown)). The command current IT1 is calculated. The command current switching unit 53 selects the command current IT1 calculated by the EPS command current calculation unit 51 as the command current IT to be passed to the current control unit 55 while operating in the electric power steering (EPS) mode.

  On the other hand, the control unit 22 includes a movement distance calculation unit 61, a target rudder angle calculation unit 63, and a rudder angle control unit 65 for the automatic steering control mode. As described above, the storage unit 23 includes a table (target movement trajectory table) that defines the target rudder angle θref with respect to the movement distance X, which is set along the target movement trajectory for each of the parking modes that can be selected by the switch Sf. ) Is stored. As described above, the movement distance calculation unit 61 calculates the movement distance X = rΘ from the wheel rotation angle Θ detected by the wheel rotation angle sensor Sc and the tire radius r. The target rudder angle calculation unit 63 reads out the target movement locus table corresponding to the parking mode selected by the switch Sf from the storage unit 23, refers to the table based on the calculated movement distance X, and sets the movement distance X to A corresponding target rudder angle θref is obtained.

  The rudder angle control unit 65 uses a predetermined control method (in this embodiment, I-PD control, details will be described later), and calculates the actual rudder angle θ detected by the actual rudder angle sensor Sa. The command current IT2 for matching with the obtained target steering angle θref is calculated. Further, as will be described in detail later, the rudder angle control unit 65 does not increase the magnitude of the deviation between the actual current IM that is actually energized to the electric motor of the steering actuator 7 and the command current IT2. The indicated current IT2 is controlled.

  The command current switching unit 53 uses the steering angle as the command current IT to be passed to the current control unit 54 from when the automatic steering start switch Sg is turned ON to start the automatic steering control mode until the mode ends. The command current IT2 calculated by the control unit 65 is selected.

  The actual current IM that is actually energized to the electric motor of the steering actuator 7 is detected by a predetermined sensor. The current control unit 55 generates a control signal by performing feedback control so that the actual current IM matches the command current IT received from the command current switching unit 53, and drives the electric motor by the control signal. To do. Any appropriate control method (for example, PID control, PI control, etc.) can be used for feedback control.

  Thus, in the electric power steering (EPS) mode, the electric motor is controlled to converge the detected actual current IM to the command current IT1, and in the automatic steering control mode, the detected actual current IM is changed to the command current IT2. The electric motor is controlled to converge.

Next, a more detailed configuration of the rudder angle control unit 65 according to one embodiment of the present invention will be described with reference to FIG. In the figure, z ⁻¹ denotes a delay element.

In this embodiment, the velocity type algorithm of proportional / differential precedence type PID control (I-PD control) is used to calculate the instruction current IT2, and the IPD control unit 71 performs the following equations (1) to (4). ) Is performed. Here, k indicates a control time.
p (k) = θ (k−1) −θ (k) (1)
d (k) = p (k) −p (k−1) (2)
i (k) = θref (k) −θ (k) (3)
DIT2 (k) = Kp · p (k) + Kd · d (k) + Ki · i (k) (4)

  Specifically, the deviation p (k) between the previous value θ (k−1) of the actual steering angle and the current value (k) is calculated, and the current value p (k) of the deviation and the previous value are calculated. A current value d (k) of a deviation from p (k−1) (which is a differential value) is calculated. On the other hand, a deviation i (k) between the target rudder angle θref (k) and the actual rudder angle θ (k) is calculated. The current value DIT2 (k) corresponding to the change in the command current is calculated as shown in Expression (4) using a predetermined proportional gain Kp, differential gain Kd, and integral gain Ki.

  The command current holding unit 73 changes the output based on the magnitude of the deviation between the current value IM (k) of the actual current and the previous value IT2 (k−1) of the command current. Specifically, if the magnitude of the deviation is equal to or greater than a predetermined value, the value zero is output as the change amount DIT2 ′ (k) instead of the command current change amount DIT2 (k) calculated by the IPD control unit 71. To do. On the other hand, if the magnitude of the deviation is less than a predetermined value, the command current change DIT2 (k) calculated by the IPD control unit 71 is output as the change DIT2 '(k). Thus, when the magnitude of the deviation between the actual current and the command current is large, the command current is held at the previous value without being changed. Thereby, it can prevent that the magnitude | size of this deviation spreads more.

  The adder 75 adds the change DIT2 ′ (k) output from the command current holding unit 73 to the previous value IT2 (k−1) of the command current, and calculates the basic value IT2b (k) of the command current. .

  Preferably, a limiter 77 is provided. There is an upper limit to the magnitude of the current that can be passed through the electric motor, and as shown in FIG. 6, this is defined by the saturation value ± IT2th. The limiter 77 limits the basic value IT2b of the instruction current so as not to become larger than the saturation value, and outputs a final instruction current IT2.

  Specifically, if the command current basic value IT2b (k) calculated by the adder 75 is larger than the saturation value IT2th, the saturation value IT2th is output as the command current IT2 (k). If the calculated command current basic value IT2b (k) is smaller than the saturation value −IT2th, the saturation value −IT2th is output as the command current IT2 (k). If the calculated command current basic value IT2b (k) is equal to or greater than the saturation value −IT2th and equal to or less than the saturation value IT2th, the calculated command current basic value IT2b (k) is equal to the command current IT2. (K) is output.

  A difference from conventional steering angle control is that an instruction current holding unit 73 is provided. Conventionally, the command current change DIT2 (k) calculated by the predetermined control is added to the previous value IT2 (k-1) of the command current, and the limiter 77 is applied to the value obtained by the addition to provide the command. The current IT2 was calculated. With such a configuration, as described with reference to FIG. 9, even when the actual current cannot follow the command current due to the actual limit of the actual current, the deviation between the actual current and the command current is not possible. As a result, the actual rudder angle may overshoot the target rudder angle or hit the maximum rudder angle. This may lead to impact noise or damage to the steering mechanism.

  According to the present invention, the indicated current holding unit 73 is provided, and when the deviation between the actual current and the indicated current is large due to the action of the holding unit 73, that is, the actual current can follow the indicated current. If not, the indicated current is held without being updated. This prevents the command current from changing so that the deviation further increases. Therefore, it is possible to perform control such that the deviation between the actual current and the command current is within a predetermined range, and it is possible to prevent impact sound or damage due to the increase in the deviation.

  In this embodiment, a speed type algorithm of I-PD control is used as the control method of the rudder angle control unit 65, but any other appropriate control method may be used (for example, a normal PID). Control etc.). Further, in FIG. 5, the steering angle control unit 65 is represented as a block diagram of hardware components for easy understanding, but naturally, the IPD control unit 71 to the limiter 77 are replaced with software (computer program). Or may be realized by a combination of software and hardware.

  Next, with reference to FIG. 7, a flow of a process executed by the instruction current holding unit 73 will be described. In this embodiment, the instruction currents IT1 and IT2 are calculated at a predetermined time interval, and the actual current IM is also detected at the predetermined time interval. Therefore, the process of FIG. 7 is also executed at the predetermined time interval. As described above, k represents the control time.

  In step S701, a deviation (IT2 (k−1) −IM (k)) between the previous value IT2 (k−1) of the command current and the actual current IM (k) detected this time is calculated.

  In step S702, it is determined whether or not the absolute value | IT2 (k-1) -IM (k) | calculated in step S701 is equal to or greater than a predetermined value (for example, 3 amperes). When the determination in step S702 is No, that is, if the absolute value of the deviation is less than the predetermined value, it indicates that the deviation is small. This indicates that the actual current IM follows the command current IT2 within the predetermined range. Indicates that Therefore, in step S707, the instruction current change amount DIT2 (k) calculated by the predetermined control (I-PD control in this embodiment) as described with reference to FIG. 5 is changed to DIT2 ′ (k). Set. Thus, the command current IT2 is updated to the current value without being held at the previous value.

  On the other hand, if the determination in step S702 is Yes, that is, if the absolute value of the deviation is greater than or equal to the predetermined value, this indicates that the deviation is large. This indicates that the actual current IM is within the predetermined range to the indicated current IT2. Indicates not following. In this case, the process proceeds to step S703.

  In this embodiment, in order to make a determination of holding of the instruction current with better accuracy, in steps S703 to S705, the direction of the deviation and the direction of the instruction current change DIT2 are determined. That is, in step S703, it is determined whether the sign of the deviation (IT2 (k−1) −IM (k)) is plus (+) or minus (−). Here, a plus sign indicates a current direction for rotating the electric motor in a direction for turning the wheel to the right, and a minus sign indicates a current direction for rotating the electric motor in a direction for turning the wheel to the left. And If the sign indicates plus, that is, turning to the right, the process proceeds to step S704, and it is determined whether the sign of the current value DIT2 (k) for the indicated current change is plus or minus. The sign of the change DIT2 here is the same as the sign of the deviation, the plus sign indicates the current direction for rotating the electric motor in the direction of turning the wheel to the right, and the minus sign indicates that the wheel is left. It is assumed that the current direction for rotating the electric motor is shown in the direction of turning.

  When the sign of the current value DIT2 (k) corresponding to the indicated current change is positive (turned to the right) in step S704, the sign coincides with the sign of the deviation, so that the current value DIT2 (k ) Indicates that it acts to further increase the magnitude of the deviation between the current indicated current IT2 and the actual current IM. In order to prevent the deviation between the command current IT2 and the actual current IM from further spreading, in step S706, DIT2 '(k) is set to zero, and the command current IT2 is held at the previous value without being updated.

  When the sign of the current value DIT2 (k) corresponding to the indicated current change is negative (turned to the left) in step S704, this indicates the opposite direction to the sign of the deviation, so the current value DIT2 (k ) Indicates that the magnitude of the deviation between the current command current IT2 and the actual current IM acts to decrease. Accordingly, the process proceeds to step S707, where the change DIT2 (k) calculated this time is set in DIT2 '(k), and the command current IT2 is updated to the current value without being held at the previous value.

  Note that there may be a case where the calculated current value DIT2 (k) for the indicated current change has a zero value. In this case, the determination in step S704 may proceed to step S706 or may proceed to step S707. Since DIT2 (k) = 0, DIT2 ′ (k) = 0 is obtained regardless of which step is performed, and as a result, the value of the instruction current IT2 is not updated.

  Returning to step S703, when the sign of the deviation is negative (turning to the left), the process proceeds to step 705, and the sign of the current value DIT2 (k) for the indicated current change is determined in the same manner as in step S704. When the sign is negative (steering to the left), the direction of the instruction current change DIT2 (k) is equal to the current instruction current IT2 and the actual current IM since the direction of the deviation coincides with the direction. It shows that the magnitude of the deviation in between acts to further increase. In order to prevent the deviation between the command current IT2 and the actual current IM from further spreading, in step S706, DIT2 ′ (k) is set to zero, and the command current IT2 is held at the previous value without being updated. .

  In step S705, when the sign of the current value DIT2 (k) for the indicated current change is positive (turned to the right), this indicates the opposite direction to the sign of the deviation, so the current value DIT2 ( k) indicates that it acts to reduce the deviation between the current command current IT2 and the actual current IM. Accordingly, the process proceeds to step S707, where the change DIT2 (k) calculated this time is set in DIT2 '(k), and the command current IT2 is updated to the current value without being held at the previous value.

  Similarly to step S704, also in step S705, when the current value DIT2 (k) for the indicated current change has a zero value, the process may proceed to step S706 or may proceed to step S707. Since DIT2 (k) = 0, DIT2 ′ (k) = 0 is obtained regardless of which step is performed, and as a result, the value of the instruction current IT2 is not updated.

  In this way, the current supplied to the electric motor is controlled by the command current holding unit 73 so that the actual current IM follows the command current IT2 within a predetermined range. Further, as shown in steps S703 to S705 of FIG. 7, the instruction current is changed only when the sign of the deviation between the actual current IM and the instruction current IT2 matches the sign of the instruction current change DIT2. If it does not match, the indicated current is changed. Therefore, only when the deviation between the actual current and the command current is widened by updating the command current, the command current is held, and when the deviation between the real current and the command current is small by updating the command current, Update is allowed. In this way, the instruction current can be controlled more finely so that the actual current better follows the instruction current.

  FIG. 8 shows a simulation result of the automatic steering control according to the present invention. FIG. 9 shows the transition of the target steering angle and the actual steering angle with respect to the steering angle, and the transition of the command current and the actual current with respect to the electric motor current, as in FIG. 9 described above. The steering to the right is positive with respect to the predetermined reference position, and the steering to the left is negative. Regarding the current, the current for turning in the right direction is positive, and the current for turning in the left direction is negative. The effect of the present invention will be described with reference to FIG. 8 while comparing with FIG.

  When the target rudder angle θref starts to change at time t1 in FIG. 8, a deviation from the actual rudder angle θ occurs. In order to eliminate this deviation, the magnitude (absolute value) of the command current increases.

  As described above, the actual current has a limit. In the conventional automatic steering control of FIG. 9, even if the actual current cannot follow the command current due to this limit, the region 201 (time t <b> 2 to time t <b> 2) remains while the deviation between the target steering angle and the actual steering angle is not resolved. As indicated by t3), the magnitude of the indicated current continued to increase. As a result, the command current may stick to a predetermined allowable value, and the actual current cannot follow the command current (time t3 to t4).

  On the other hand, in the control according to the present invention of FIG. 8, as described above, the command current is controlled so that the magnitude of the deviation between the actual current and the command current does not spread beyond a predetermined value. That is, when the magnitude of the deviation between the command current and the actual current is greater than or equal to a predetermined value, the command current is held at the previous value and the increase in the command current is prohibited, and is less than the predetermined value For this, the magnitude of the instruction current is increased. Therefore, as shown in a region 301 at times t2 to t3, the instruction current is prevented from sticking to an allowable value, and the actual current (upper side of the two graphs shown in the region 301) is within a predetermined range. It is possible to follow the command current (the lower side of the two graphs) while maintaining the deviation.

  In FIG. 8, when the target rudder angle θref changes to a value to be reached, the target rudder angle θref does not change, and as shown in the vicinity of time t3, the deviation between the actual rudder angle θ and the target rudder angle θref. Becomes smaller. Accordingly, the magnitude of the instruction current decreases.

  Here, in the conventional control of FIG. 9, as described above with reference to the region 203, the instruction current decreases from the value after the increase (in the case of FIG. 9, the allowable value), Therefore, it takes time until the actual current matches the command current, and the magnitude of the actual current continues to increase until the actual current matches. As the actual current continues to increase, the actual steering angle (absolute value) also continues to increase. As a result, as shown in the region 205, an overshoot exceeding the target rudder angle may occur, thereby reaching the maximum rudder angle, which may cause an impact sound or damage the steering mechanism. is there.

  On the other hand, in the control of FIG. 8 of the present invention, the instruction current is controlled so as not to deviate from the actual current by a predetermined value or more, and does not stick to the allowable value. Therefore, the command current does not decrease from a value that has a large deviation from the actual current, such as an allowable value, and as shown in a region 303, a previous value (a previous value of the command current) that has a small deviation from the actual current. ), It can be matched with the actual current at an early stage (around time t3). If they match, the actual current magnitude begins to decrease with the indicated current. Since the reduction in the magnitude of the actual current is started early, the actual steering angle can also coincide with the target steering angle at an early stage.

  Further, in the conventional control of FIG. 9, there is a state in which the actual steering angle continues to increase as the actual current continues to increase in an attempt to match the command current. In this control, such an increase in actual current and actual steering angle is prevented. As a result, as shown in a region 305, the actual rudder angle can be converged to the target rudder angle without overshooting. Therefore, even if the target rudder angle is set to a value close to the maximum rudder angle, the actual rudder angle can be prevented from reaching the maximum rudder angle. Therefore, it is possible to more reliably prevent impact noise and damage in the steering mechanism.

  Thus, in the present invention, as described above, the limit that may be required in the conventional control, that is, the change speed of the target rudder angle is controlled within the range in which the actual current can follow the command current, or the actual rudder angle is the maximum. There is no need for such a restriction that the range in which the target rudder angle changes so as not to reach the rudder angle is set to a range away from the maximum rudder angle. Therefore, the vehicle can be turned in a small turn.

  As described above, specific embodiments of the present invention have been described. However, the present invention is not limited to these embodiments.

The figure which shows the whole structure of the automatic steering device of the vehicle according to one Example of this invention. The figure for demonstrating the effect | action of back parking / left mode according to one Example of this invention. The figure which shows the mode selection switch and automatic parking start switch according to one Example of this invention. 1 is a detailed block diagram of a steering control device according to one embodiment of the present invention. The detailed block diagram of the steering angle control part according to one Example of this invention. The figure for demonstrating operation | movement of a limiter according to one Example of this invention. The flowchart which shows the process by the instruction | indication electric current holding part according to one Example of this invention. The figure which shows transition of the steering angle and electric current by automatic steering control according to one Example of this invention. The figure which shows transition of the steering angle and electric current by the conventional automatic steering control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 7 Steering actuator 22 Control part 23 Storage part 65 Steering angle control part 73 Instruction electric current holding part Sa Actual steering angle sensor (detection means) V Vehicle

Claims (2)

A steering actuator for steering the wheels of the vehicle;
Based on the target steering angle set in advance according to the target movement locus of the vehicle to the target position and the current steering angle, the energization all come current value is repeatedly calculated at a predetermined timing to said steering actuator, the command current value Indicating current calculation means for outputting as
Control means for controlling the operation of the steering actuator so that the actual current value flowing through the steering actuator converges to the command current value ,
The command current calculation means maintains the command current value output last time as a first condition that a difference between the command current value output last time and the current actual current value is a predetermined value or more. Output as the indicated current value of
Automatic steering device for vehicles. Further, when outputting the current value, wherein the command current calculation means has calculated this time as the command current value, a judgment means for judging whether or not so that the difference between the actual current value and the command current value increases Prepared,
The command current calculation means further that it is determined so that the said difference is increased as the second condition by said determining means, when said first and second conditions are met, the previously output the Maintain the command current value and output it as the current command current value.
The automatic steering device for a vehicle according to claim 1.

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