Vehicle steering device

Abstract

To provide a vehicular steering device capable of accurately calculating a basic play amount to be changed by secular change, etc.SOLUTION: A vehicular steering device includes: an electric motor for rotating a steering shaft; a steering angle detection part for detecting a steering angle; a motor control part for controlling the electric motor; and a play amount calculation part for calculating a basic play amount. The basic play amount calculation part stores a steering angle as a first steering angle when turning-back is performed, determines whether or not the play is blocked up after the turning-back on the basis of a steering angle speed, stores a steering angle as the second steering angle when it is determined that the play is blocked up, and calculates an absolute value of a difference between the first steering angle and the second steering angle as a basic play amount.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a vehicle steering system. [Background technology]

[0002] In large vehicles such as trucks and buses, a rigid axle suspension in which the left and right wheels are connected by an axle beam is widely used. In vehicles having a rigid axle suspension, a steering device equipped with a ball screw type hydraulic power steering mechanism is widely adopted. The steering device of such a large vehicle is equipped with a steering wheel, a steering column, a steering gear box, a pitman arm, a drag ring, a knuckle arm, a tie rod, etc., and is more complicated than the steering device of a passenger car in which an independent suspension is used. In addition, the steering device of a large vehicle has a longer length of a steering shaft, etc., compared to the steering device of a passenger car.

[0003] Patent Document 1 discloses a technique in which an electric motor is added to the steering column of the steering device of a large vehicle as described above, and the electric motor is used to automatically drive the vehicle along a target trajectory. Such automatic driving control (automatic steering control) is performed, for example, as follows. That is, first, a target steering angle of the steered wheels is calculated from the relationship between the target trajectory and the vehicle's position, and the target steering angle is calculated by multiplying this value by a steering gear ratio (ratio of steering angle to steering angle). Then, angle feedback control is performed on the electric motor so that the deviation between the target steering angle and the actual steering angle becomes zero. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-264622 A [Patent Document 2] JP 2016-135676 A Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, the steering device of a large vehicle is more complicated than that of a passenger vehicle, and the torsion and bending of the steering shaft are relatively large, so that the allowance between the steering wheel and the steered wheels is large. Therefore, when the above-mentioned automatic driving control is performed on the steering device of a large vehicle, even if a target steering angle is given, the steering angle of the steered wheels does not match the target steering angle, so the trajectory tracking performance is poor. Note that, although not as much as in a large vehicle, there is also a similar problem in passenger vehicles because there is allowance between the steering wheel and the steered wheels.

[0006] Therefore, Patent Document 2 discloses a technology in which, in order to improve trajectory tracking performance, a steering dead zone is defined as ΔH, and when starting to turn the vehicle, the target steering angle is corrected by adding ΔH / 2 to the target steering angle, and when changing direction, the target steering angle is corrected by adding ΔH to the target steering angle. However, the basic amount of play (steering dead zone), which is the amount of play between the steering wheel and the steered wheels, changes due to various factors such as aging. In particular, in large vehicles such as trucks and buses, the play of the sector gear of the hydraulic power steering mechanism can be adjusted during maintenance, and such adjustments also change the basic amount of play.

[0007] In this specification, the term "start of turning" refers to the state in which the steering angle starts to change from a state in which the steering angle is not changing, and the term "returning" refers to the state in which the steering angle changes so that the steering direction is reversed. SUMMARY OF THE PRESENT INVETION An object of the present invention is to provide a vehicle steering system capable of accurately calculating a basic amount of play which changes due to aging or the like. [Means for solving the problem]

[0008] One embodiment of the present invention provides a vehicle steering device including a steering shaft connected to a steering wheel, a steering mechanism connected to the steering shaft for steering left and right steered wheels, an electric motor for rotating the steering shaft, a steering angle detection unit for detecting a steering angle, an electric motor control unit for controlling the electric motor, and a basic play amount calculation unit for calculating a basic play amount, wherein the basic play amount calculation unit stores the steering angle as a first steering angle when a turn is made, determines whether or not the play is reduced after the turn based on the steering angular velocity, and stores the steering angle as a second steering angle when it is determined that the play is reduced, and calculates the absolute value of the difference between the first steering angle and the second steering angle as the basic play amount.

[0009] In this configuration, the basic amount of play, which is the amount of play between the steering wheel and the steered wheels, can be calculated while the vehicle is running, so that the basic amount of play which changes due to aging and the like can be accurately calculated. In one embodiment of the present invention, the basic play amount calculation unit calculates the basic play amount for each of a predetermined number of turns, and calculates the average value of the obtained multiple basic play amounts as the final basic play amount.

[0010] In one embodiment of the present invention, the basic play calculation unit acquires the current value at time intervals, and determines that a turn has occurred when the value obtained by subtracting the previous current value from the current current value becomes negative for the first time after the value obtained by subtracting the previous current value from the current current value was positive, or when the value obtained by subtracting the previous current value from the current current value becomes positive for the first time after the value obtained by subtracting the previous current value from the current current value was negative.

[0011] In one embodiment of the present invention, the current value of the electric motor is a current command value for the electric motor or an actual current value flowing through the electric motor. In one embodiment of the present invention, the basic play calculation unit acquires the steering angle at time intervals, and determines that a turn has been performed when the value obtained by subtracting the previous steering angle from the current steering angle becomes negative for the first time after the value obtained by subtracting the previous steering angle from the current steering angle was positive, or when the value obtained by subtracting the previous steering angle from the current steering angle becomes positive for the first time after the value obtained by subtracting the previous steering angle from the current steering angle was negative.

[0012] In one embodiment of the present invention, the basic play amount calculation unit calculates the steering angular velocity at time intervals, and determines that play has been eliminated when, after the turning is performed, the absolute value of the steering angular velocity becomes greater than a predetermined first threshold value, and then the absolute value of the steering angular velocity becomes less than a predetermined second threshold value that is less than the first threshold value. In one embodiment of the present invention, the electric motor control unit controls the electric motor based on a given target steering angle, and the electric motor control unit includes a target steering angle correction unit that corrects the target steering angle based on the basic play amount.

[0013] One embodiment of the present invention has a first control form and a second control form as steering control forms for a vehicle. In the first control form, the basic play amount is calculated by the basic play amount calculation unit without correcting the target steering angle by the target steering angle correction unit. In the second control form, the target steering angle is corrected by the target steering angle correction unit without calculating the basic play amount by the basic play amount calculation unit. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering device. [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of the vehicle steering device. [Diagram 3] FIG. 3 is a block diagram showing the electrical configuration of the motor control ECU. [Figure 4]FIG. 4 is a graph showing the relationship between the steering angle θh and the turning angle δ. [Diagram 5] FIG. 5 is a flowchart showing the procedure of the basic play amount calculation process executed by the basic play amount calculation unit. [Figure 6] FIG. 6 is a time chart showing an example of changes in the q-axis current command value Iq,cmd, the amount of change ΔIq,cmd in the q-axis current command value Iq,cmd, the steering angular velocity dθh / dt, and the steering angle θh. [Figure 7] FIG. 7 is a flowchart showing the procedure of the steering angle command value setting process executed by the steering angle command value setting unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing a schematic configuration of a steering device for a vehicle, in which the left side of a dashed line 29 is a side view of the vehicle as seen from the side, and the right side of the dashed line 29 is a plan view of the vehicle as seen from above. This vehicle steering device 1 includes a handle (steering wheel) 2, a steering column 4 having a steering shaft 3, a bevel gear section 5, a power transmission shaft 6, a ball screw type hydraulic power steering mechanism (hereinafter referred to as the "hydraulic power steering mechanism 7"), a steering mechanism 8, an electric motor 9, etc.

[0016] The steering wheel 2 is connected to an input shaft of a bevel gear unit 5 via a steering shaft 3. The output shaft of the bevel gear unit 5 is connected to an input shaft of a hydraulic power steering mechanism 7 via a power transmission shaft 6. The steering mechanism 8 includes a pitman arm 11, a drag link 12, a knuckle arm 13, kingpin shafts 14 and 15, a tie rod arm 16 and a tie rod 17.

[0017] One end of the pitman arm 11 is connected to a sector shaft of the hydraulic power steering mechanism 7. The other end of the pitman arm 11 is connected to one end of a drag link 12. The other end of the drag link 12 is connected to one end of a knuckle arm 13 of the right steered wheel (right front wheel) 22. The other end of the knuckle arm 13 is connected to a kingpin shaft 14 of the right steered wheel 22. The kingpin shaft 14 of the right steered wheel 22 and the kingpin shaft 15 of the left steered wheel (left front wheel) 21 are connected by a tie rod arm 16 and a tie rod 17. The dashed line 18 in the figure is an axle beam.

[0018] The electric motor 9 is provided on the steering column 4 and is connected to the steering shaft 3 via a reduction gear (not shown). The reduction gear is a worm gear mechanism including a worm gear and a worm wheel that meshes with the worm gear. In the following, the reduction ratio of the reduction gear is represented by R. The reduction ratio R is defined as the ratio of the worm gear angle, which is the rotation angle of the worm gear, to the worm wheel angle, which is the rotation angle of the worm wheel. The rotor rotation angle θ of the electric motor 9 m is detected by the rotation angle sensor 25.

[0019] When the steering wheel 2 is rotated, the rotational torque is transmitted to the steering shaft 3, the bevel gear portion 5, the power transmission shaft 6, and the ball screw type hydraulic power steering mechanism 7, causing the pitman arm 11 to swing. Due to the swing of the pitman arm 11, the drag link 12 is moved in the front-rear direction, the knuckle arm 13 is swingable, and the steered wheels 21, 22 are turned.

[0020] When the electric motor 9 is rotated, the rotational torque is transmitted to the steering shaft 3, so that the steered wheels 21, 22 are steered via the same power transmission path as described above. In other words, by rotating the steering shaft 3 with the electric motor 9, the steered wheels 21, 22 can be steered. FIG. 2 is a block diagram showing the electrical configuration of the vehicle steering device.

[0021] The vehicle is provided with an automatic steering ECU 101 and a motor control ECU 102. The motor control ECU 102 is an example of an electric motor control unit of the present invention. The automatic steering ECU 101 outputs a mode signal S indicating whether the steering mode is the automatic steering mode or the manual steering mode. mode In addition, the automatic steering ECU 101 outputs a target steering angle θ for automatic steering during the automatic steering mode. cmda Generate.

[0022] Target steering angle θ cmda is the steering angle (rotation angle of the steering shaft 3) θ in the automatic steering mode h In this embodiment, the steering angle θ h is the amount of rotation (rotation angle) in both forward and reverse directions of the steering shaft 3 from the neutral position (neutral steering position) of the steering wheel 2, and the amount of rotation to the right from the neutral steering position is represented by a positive value, and the amount of rotation to the left from the neutral steering position is represented by a negative value. In this embodiment, the steering angle θ h is the rotor rotation angle θ detected by the rotation angle sensor 25. m It is calculated from

[0023] Mode signal S mode and the target steering angle θ cmda is provided to the motor control ECU 102. In addition, the motor control ECU 102 receives a key switch state detection signal S K is input. In this embodiment, the key switch of the vehicle is, for example, an ignition key for starting an engine (not shown) or a driving motor (not shown). The key switch may be an ignition key or may be one that emits an electric signal when authentication is obtained using an electronic key equipped with an immobilizer, or one that emits an electric signal by pressing a push button.

[0024] When the key switch is turned on, a key switch state detection signal S K(hereinafter referred to as the "key switch on state signal") is input to the motor control ECU 102. When the key switch is turned off, a key switch state detection signal S K (hereinafter referred to as the “key switch off state signal”) is input to the motor control ECU 102.

[0025] The motor control ECU 102 receives a key switch state detection signal S K , mode signal S mode , target steering angle θ cmda Based on the output signal of the rotation angle sensor 25, the control circuit 24 controls the driving of the electric motor 9 in the automatic steering mode. FIG. 3 is a block diagram showing the electrical configuration of the motor control ECU 102. As shown in FIG. The motor control ECU 102 controls the electric motor 9 by angle feedback control. The motor control ECU 102 includes a microcomputer 31, a drive circuit (inverter circuit) 32 that is controlled by the microcomputer 31 and supplies power to the electric motor 9, and a current detection unit 33 that detects the motor current flowing through the electric motor 9.

[0026] The microcomputer 31 includes a CPU and memory (ROM, RAM, non-volatile memory, etc.), and functions as a plurality of functional processing sections by executing a predetermined program. The plurality of functional processing sections include a basic play amount calculation section 41, a steering angle command value setting section 42, an angle deviation calculation section 43, a PD control section 44, a current command value setting section 45, a current deviation calculation section 46, a PI (proportional integral) control section 47, a dq / UVW conversion section 48, a PWM (Pulse Width Modulation) control section 49, a UVW / dq conversion section 50, a rotation angle calculation section 51, and a reduction ratio division section 52.

[0027] The rotation angle calculation unit 51 calculates the rotation angle θ of the rotor of the electric motor 9 based on the output signal of the rotation angle sensor 25. m (Hereinafter, "rotor rotation angle θ m The rotor rotation angle θ calculated by the rotation angle calculation unit 51 is mis provided to a dq / UVW conversion unit 48, a UVW / dq conversion unit 50, and a reduction ratio division unit 52. The reduction ratio division unit 52 divides the rotor rotation angle θ m By dividing by the reduction ratio R, the steering angle θ h Calculate the steering angle θ h is provided to a basic play amount calculation unit 41, a steering angle command value setting unit 42, and an angle deviation calculation unit 43. The rotation angle sensor 25, the rotation angle calculation unit 51, and the reduction ratio division unit 52 are an example of a steering angle detection unit of the present invention.

[0028] In this embodiment, the basic play amount calculation unit 41 calculates the steering angle θ h and the q-axis current command value I q,cmd Based on this, a basic amount of play α, which is the amount of play occurring between the steering wheel 2 and the steered wheels 21, 22, is calculated. The basic amount of play calculation unit 41 will be described in detail later. The steering angle command value setting unit 42 sets a steering angle command value θ cmd In this embodiment, the steering angle command value setting unit 42 normally sets the target steering angle θ cmda The steering angle command value θ cmd However, after the basic play amount α is given from the basic play amount calculation unit 41, when the steering mode is the automatic steering mode and turning is performed by the automatic steering, the steering angle command value setting unit 42 sets the target steering angle θ based on the basic play amount α. cmda Then, the steering angle command value setting unit 42 corrects the corrected target steering angle θ cmda The steering angle command value θ cmd The steering angle command value setting unit 42 is an example of the "target steering angle correcting unit" of the present invention.

[0029] The steering angle command value θ cmd is provided to the angle deviation calculation unit 43. The angle deviation calculation unit 43 calculates the steering angle command value θ cmd and steering angle θ h Deviation Δθ(θcmd -θ h ) is calculated. The PD control unit 44 performs a PD calculation (proportional differential calculation) on the angle deviation Δθ calculated by the angle deviation calculation unit 43 to obtain a torque command value T cmd Calculate the following.

[0030] The current command value setting unit 45 sets the torque command value T cmd Based on this, the d-axis current command value I d,cmd and the q-axis current command value I q,cmd (Hereinafter, these will be referred to collectively as "two-phase current command value I dq,cmd ") is set. Specifically, the current command value setting unit 45 sets the q-axis current command value I q,cmd is a significant value, while the d-axis current command value I d,cmd More specifically, the current command value setting unit 45 sets the torque command value T cmd , the torque constant K of the electric motor 9 T By dividing by, the q-axis current command value I q,cmd The two-phase current command value I dq,cmd is given to the current deviation calculation unit 46. The q-axis current command value I q,cmd is also given to the basic play amount calculation unit 41. The q-axis current command value I q,cmd are examples of the "electric motor current value" and the "current command value" in the present invention.

[0031] The current detection unit 33 detects the U-phase current I U , V phase current I V and W-phase current I W (Hereinafter, these will be referred to collectively as "three-phase detection current I UVW The three-phase detection current I UVW is provided to the UVW / dq conversion unit 50. The UVW / dq conversion unit 50 converts the three-phase detected current I UVW (U phase current I U , V phase current IV and W-phase current I W ) into the two-phase detection current I d and I q (Hereinafter, the two-phase detection current I dq This coordinate conversion is performed by converting the rotor rotation angle θ m The two-phase detection current I dq (d-axis detection current I d and q-axis detected current I q ) is provided to the current deviation calculation unit 46.

[0032] The current deviation calculation unit 46 calculates the two-phase current command value I dq,cmd and the two-phase detection current I given by the UVW / dq conversion unit 50. dq More specifically, the current deviation calculation unit 46 calculates the deviation between the d-axis current command value I d,cmd d-axis detection current I d and the q-axis current command value I q,cmd q-axis detected current I q These deviations are provided to the PI control unit 47.

[0033] The PI control unit 47 performs a PI (proportional integral) calculation on the current deviation calculated by the current deviation calculation unit 46 to calculate a two-phase voltage command value V dq,cmd (d-axis voltage command value V d,cmd and the q-axis voltage command value V q,cmd ) is generated. dq,cmd is provided to the dq / UVW conversion unit 48. The dq / UVW conversion unit 48 converts the two-phase voltage command value V dq,cmd The three-phase voltage command value V UVW,cmd This coordinate conversion is performed using the rotor rotation angle θ m The three-phase voltage command value V UVW,cmd is the U-phase voltage command value V U,cmd , V-phase voltage command value V V,cmd and W-phase voltage command value VW,cmd This three-phase voltage command value V UVW,cmd is provided to the PWM control unit 49.

[0034] The PWM control unit 49 controls the U-phase voltage command value V U,cmd , V-phase voltage command value V V,cmd and W-phase voltage command value V W,cmd The PWM control signal generator 32 generates a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM control signal having duties corresponding to the respective phases, and supplies the signals to the drive circuit 32. The drive circuit 32 is composed of a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting this inverter circuit are controlled by a PWM control signal provided by a PWM control unit 49, thereby generating a three-phase voltage command value V UVW,cmd A voltage equivalent to the above is applied to the stator windings of each phase of the electric motor 9.

[0035] The angle deviation calculation unit 43 and the PD control unit 44 constitute an angle feedback control means. h is set by the steering angle command value setting unit 42. cmd The electric motor 9 is controlled so that the rotational speed approaches the rotational speed φ. The basic play amount calculation unit 41 and the steering angle command value setting unit 42 will be described in detail below.

[0036] FIG. 4 shows the steering angle θ h 4 is a graph showing the relationship between the steering angle (tire angle) δ and FIG. 4 shows a state where the steering angle θ is greater than zero and is set to a predetermined positive side from the steering neutral position O. hp Steering angle θ h After continuously changing the steering angle θ h A predetermined negative steering angle θ that is smaller than zero hm and then the steering angle θ h The positive steering angle θ hp 4 shows the locus of the steering angle δ when the steering angle δ is continuously changed toward

[0037] There is a play between the steering wheel 2 and the steered wheels 21 and 22. For this reason, the steering angle θ h Even if the steering angle θ increases from 0°, the turning angle δ does not increase immediately. h Even if the steering angle θ changes, the steering angle δ does not change immediately. h When the play is reduced due to an increase in (point A), the steering angle δ begins to increase. And the steering angle θ h is the positive steering angle θ hp When the steering angle reaches point B and the steering operation is performed, the steering angle θ h In this case, the steering angle δ does not decrease immediately because of the play. h Even if the steering angle θ changes, the steering angle δ does not change immediately. h When the play is eliminated by the reduction of , the steering angle δ starts to decrease (point C). Therefore, when the steering angle δ becomes zero (point D), the steering angle θ h will be a value less than or equal to 0.

[0038] Steering angle θ h is the negative steering angle θ hm When the steering angle reaches point E and the steering operation is performed, the steering angle θ h In this case, the steering angle δ does not increase immediately because of the play. h When the play is reduced due to an increase in , the steering angle δ starts to increase (point F). Steering angle θ between points A and D (or points B and C, or points F and E) h The absolute value of the change in the amount of play is the basic amount of play α.

[0039] FIG. 5 is a flowchart showing the procedure of the basic play amount calculation process executed by the basic play amount calculation unit 41. When a key switch ON state signal is input (step S1), the basic play amount calculation unit 41 sets a variable n for storing the number of calculations of the basic play amount α to 0 (step S2).

[0040] Next, the basic play amount calculation unit 41 calculates the q-axis current command value I q,cmd and steering angle θ h (Step S3). Then, the basic play amount calculation unit 41 determines whether or not a turning motion has been performed (Step S4). Whether or not the steering has been performed is determined, for example, as follows. That is, the currently acquired q-axis current command value I q,cmd(i) The previously acquired q-axis current command value I q,cmd(i-1) The value obtained by subtracting (I q,cmd(i) -I q,cmd(i-1) ) is the q-axis current command change amount ΔI q,cmd The basic play calculation unit 41 calculates the q-axis current command value change amount ΔI q,cmd After the q-axis current command value change amount ΔI q,cmd becomes negative for the first time, or the q-axis current command change amount ΔI q,cmd After the q-axis current command value change amount ΔI q,cmd When becomes positive for the first time, it is determined that a turn has been made.

[0041] q-axis current command value change amount ΔI q,cmd Instead, the q-axis detected current I q Change in q-axis detected current ΔI q In that case, in step S3, the q-axis current command value I q,cmd Instead of the q-axis detected current I q is obtained. The basic play amount calculation unit 41 may determine whether or not a turning motion has been performed as follows. That is, the currently acquired steering angle θ h(i) The steering angle θ obtained last time h(i-1) The value obtained by subtracting (θ h(i) -θ h(i-1) ) is the steering angle change amount Δθ h The basic play amount calculation unit 41 calculates the steering angle change amount Δθ h After the steering angle change amount Δθ h becomes negative for the first time, or when the steering angle change amount Δθ h After the steering angle change amount Δθ hWhen it first becomes positive, it is determined that the switching has occurred.

[0042] If it is determined that the switching has not occurred (step S4: NO), the basic play amount calculation unit 41 returns to step S3. In step S4, if it is determined that the switching has occurred (step S4: YES), the basic play amount calculation unit 41 increments n by 1 (step S5). Then, the basic play amount calculation unit 41 uses the steering angle θ h obtained most recently in step S3 ha as the first steering angle θ

[0043] and stores it (step S6). h Next, the basic play amount calculation unit 41 acquires the steering angle θ h (step S7). Then, the basic play amount calculation unit 41 determines whether or not the play is jammed based on the steering angular velocity (the time derivative value dθ h / dt of the steering angle θ) (step S8). Whether or not the play is jammed is determined as follows, for example. The absolute value of the steering angular velocity dθ h / dt (hereinafter referred to as "the absolute value of the steering angular velocity |dθ h / dt|") increases because there is play when the switching occurs, and decreases (decreases) because the load increases when the play is jammed. Therefore, the basic play amount calculation unit 41 subtracts the previously acquired steering angle θ h(i) from the currently acquired steering angle θ h(i―1) to calculate the steering angular velocity dθ h / dt. Then, after the switching, the basic play amount calculation unit 41 determines that the play is jammed when the absolute value of the steering angular velocity |dθ h / dt| becomes less than or equal to the second threshold value B (0 < B ≤ A) that is less than or equal to the first threshold value A after the absolute value of the steering angular velocity |dθ h / dt| becomes greater than the first threshold value A (A > 0). In this embodiment, B = A. However, in step S8 immediately after it is determined that the return has occurred, the absolute value of the steering angular velocity |dθ h / dt| is set to zero.

[0044] If it is determined that the play is not eliminated (step S8: NO), the basic play amount calculation unit 41 returns to step S7. By returning from step S8 to step S7, the steering angle θ h When the steering angle θ h The period during which the signal is acquired is constant. In step S8, when it is determined that the play is eliminated (step S8: YES), the basic play amount calculation unit 41 calculates the steering angle θ h The second steering angle θ hb (Step S9). Then, the basic play amount calculation unit 41 stores the first steering angle θ ha and the second steering angle θ hb Absolute value of difference with |θ hb -θ ha | is calculated as the basic amount of play αn and stored (step S10).

[0045] Next, the basic play amount calculation unit 41 determines whether n has reached a predetermined value N (N is an integer equal to or greater than 2) (step S11). If n is less than N (step S11: NO), the basic play amount calculation unit 41 determines whether a key switch OFF state signal has been input (step S12). If a key switch OFF state signal has not been input (step S12: NO), the basic play amount calculation unit 41 returns to step S3.

[0046] In step S11, when it is determined that n has reached N (step S11: YES), the basic play amount calculation unit 41 calculates the N basic play amounts α1 to α N The average value of {(α1+α2+...+α N ) / N} is calculated as the final basic play amount α and is given to the steering angle command value setting unit 42 (step S13). Then, the basic play amount calculation unit 41 ends the current basic play amount calculation process.

[0047] In step S12, when it is determined that the key switch OFF state signal has been input (step S12: YES), the basic play amount calculation unit 41 ends the current basic play amount calculation process. Fig. 6 shows the q-axis current command value I q,cmd , q-axis current command value I q,cmd The change in ΔI q,cmd , steering angular velocity dθ h / dt and steering angle θ h 1 is a time chart showing an example of a change in

[0048] In the example of Fig. 6, the q-axis current command value I q,cmd After increasing, the q-axis current command value I q,cmd becomes constant, and the q-axis current command value I q,cmd decreases, and from time t4, the q-axis current command value I q,cmd is constant. q-axis current command value I q,cmd The change in ΔI q,cmd is a substantially constant positive value from time t0 to time t1. And the q-axis current command value I q,cmd The change in ΔI q,cmd At time t1, the q-axis current command value I q,cmd The change in ΔI q,cmd becomes a negative value and is maintained at that value until time t4. Then, the q-axis current command value I q,cmd The change in ΔI q,cmd increases to zero at time t4 and maintains that value.

[0049] At time t2, the q-axis current command change amount ΔI q,cmd After the q-axis current command value change amount ΔI q,cmd This corresponds to the first time when the steering angle θ becomes negative. Therefore, at time t2, it is determined that the steering has been performed (see step S4 in FIG. 5). Therefore, the steering angle θ h is the first steering angle θ ha (see step S6 in FIG. 5).

[0050] Steering angular velocity dθ h / dt increases gradually from time t0 to time t1, and is a constant positive value from time t1 to time t2. h / dt gradually decreases from time t2 to time t3, and then rapidly decreases from time t3 to become a negative first value at time t5. h / dt keeps the negative first value until time t6, and then increases rapidly to a negative second value at time t7. h / dt is a constant value.

[0051] As shown in FIG. 6, after turning, the absolute value of the steering angular velocity |dθ h / dt| becomes greater than the first threshold A, and at time t7, the absolute value of the steering angular velocity |dθ h / dt| is equal to the second threshold value B (B=A in this embodiment). Therefore, it is determined that the play is eliminated at time t7 (see step S8), and the steering angle θ h is the second steering angle θ hb (see step S9 in FIG. 5). Then, the first steering angle θ ha and the second steering angle θ hb The absolute value of the difference between these values ​​is calculated as the basic play amount (see step S9 in FIG. 5).

[0052] FIG. 7 is a flowchart showing the procedure of the steering angle command value setting process executed by the steering angle command value setting unit 42. When a key switch ON state signal is input (step S21), the steering angle command value setting unit 42 determines whether or not the basic play amount α has been given from the basic play amount calculation unit 41 (step S22).

[0053] When the basic amount of play α is not given (step S22: NO), the steering angle command value setting unit 42 sets the target steering angle θ cmda The steering angle command value θ cmd (Step S23). As a result, the target steering angle θcmda is the steering angle command value θ cmd is given to the angle deviation calculation unit 43. Thereafter, the steering angle command value setting unit 42 determines whether or not a key switch off state signal has been input (step S24). If the key switch off state signal has not been input (step S24: NO), the steering angle command value setting unit 42 returns to step S22.

[0054] In step S24, when it is determined that the key switch off state signal has been input (step S24: YES), the steering angle command value setting unit 42 ends the current steering angle command value setting process. In step S22, when it is determined that the basic play amount α has been given (step S22: YES), the steering angle command value setting unit 42 sets the steering angle θ h (Step S25). Then, it is determined whether or not a turning has been performed (Step S26). The determination whether or not a turning has been performed can be performed in the same manner as in Step S4 of FIG. 5. Note that the determination whether or not a turning has been performed is performed based on the q-axis current command value I q,cmd or q-axis detected current I q In the case where the steering angle θ h In addition, the q-axis current command value I q,cmd or q-axis detected current I q It is sufficient to obtain the above.

[0055] When it is determined that the steering is not being performed (step S26: NO), the steering angle command value setting unit 42 sets the target steering angle θ cmda The steering angle command value θ cmd (Step S27). As a result, the target steering angle θ cmda is the steering angle command value θ cmd to the angle deviation calculation unit 43. Then, the steering angle command value setting unit 42 proceeds to step S32.

[0056] In step S32, the steering angle command value setting unit 42 determines whether or not a key switch off state signal has been input. If the key switch off state signal has not been input (step S32: NO), the steering angle command value setting unit 42 returns to step S25. In step S26, when it is determined that the steering has been performed (step S26: YES), the steering angle command value setting unit 42 sets the mode signal S mode Based on this, it is determined whether the steering mode is the automatic steering mode or not (step S28).

[0057] If the steering mode is not the automatic steering mode (step S28: NO), the steering angle command value setting unit 42 proceeds to step S27 and sets the target steering angle θ cmda The steering angle command value θ cmd Thereafter, the steering angle command value setting unit 42 proceeds to step S32 and determines whether or not a key switch off state signal has been input. If the key switch off state signal has not been input (step S32: NO), the steering angle command value setting unit 42 returns to step S25.

[0058] In step S28, when it is determined that the steering mode is the automatic steering mode (step S28: YES), the steering angle command value setting unit 42 determines the planned steering direction (step S29). cmda -θ h If θ is greater than 0, the planned steering direction is determined to be a right steering direction. cmda -θ h If θ is less than 0, the planned steering direction is determined to be the left steering direction. cmda -θ h If it is 0, the planned steering direction is determined to be the previous steering direction.

[0059] When it is determined that the planned steering direction is a right steering direction (step S29: YES), the steering angle command value setting unit 42 uses the basic play amount α provided by the basic play amount calculation unit 41 and calculates the steering angle command value θ based on the following equation (1). cmd(Step S30). Then, the steering angle command value setting unit 42 proceeds to Step S32. θ cmd =θ cmda +α …(1) As a result, the target steering angle θ cmda is corrected using the basic play amount α. The corrected target steering angle θ cmda The steering angle command value θ cmd is given to the angle deviation calculation unit 43.

[0060] In step S29, when it is determined that the planned steering direction is a left steering direction (step S29: NO), the steering angle command value setting unit 42 uses the basic play amount α provided from the basic play amount calculation unit 41 and calculates the steering angle command value θ based on the following equation (2). cmd (Step S31). Then, the steering angle command value setting unit 42 proceeds to Step S32. θ cmd =θ cmda -α …(2) As a result, the target steering angle θ cmda is corrected using the basic play amount α. The corrected target steering angle θ cmda The steering angle command value θ cmd is given to the angle deviation calculation unit 43.

[0061] In step S32, if the key switch off state signal has not been input (step S32: NO), the steering angle command value setting unit 42 returns to step S25. In step S32, when it is determined that the key switch off state signal has been input (step S32: YES), the steering angle command value setting unit 42 ends the current steering angle command value setting process.

[0062] According to this embodiment, the basic play amount α, which is the amount of play occurring between the steering wheel 2 and the steered wheels 21, 22, can be calculated while the vehicle is traveling. This makes it possible to accurately calculate the basic play amount that changes due to aging and other factors. By correcting the target steering angle using the basic play amount obtained in this manner, it becomes possible to improve the trajectory tracking ability.

[0063] Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms. For example, the above embodiment has been described as being applied to a vehicle steering device provided with a hydraulic power steering mechanism 7, but the present invention can also be applied to a vehicle steering device equipped with an electric power steering device. In that case, automatic steering is performed using the electric motor of the electric power steering device.

[0064] In the above embodiment, the average value of the multiple basic play amounts α calculated for each of the multiple preset turns is set as the final basic play amount α. However, the basic play amount α calculated for one turn may be set as the final basic play amount α. In the above embodiment, when the key switch ON state signal is input, the basic play amount calculation unit 41 performs a basic play amount calculation process, and after the final basic play amount α is calculated by the basic play amount calculation unit 41, the target steering angle θ using the basic play amount α is calculated. cmda Corrections are being made to the following:

[0065] However, there are a first control mode and a second control mode as the steering control mode of the vehicle. In the first control mode, the target steering angle θ cmda In the second control mode, the basic play amount calculation unit 41 performs the basic play amount calculation process without correcting the target steering angle θ cmda The above correction may be performed.

[0066] In this case, the second control mode is, for example, a control mode in which a precise docking control (precise docking control system) of the automatic steering control is performed, and the first control mode may be a control mode of the automatic steering control other than the precise docking control. The precise docking control is a control for stopping a vehicle such as a bus precisely at a predetermined location (for example, a bus stop). In this case, a mode signal indicating whether the current control mode is the first control mode or the second control mode is provided from the automatic steering ECU 101 to the motor control ECU 102.

[0067] In the case of a vehicle equipped with an electric power steering device in which automatic steering is performed using an electric motor of the electric power steering device, the first control mode may be a control mode in which manual control is performed, and the second control mode may be a control mode in which automatic driving is performed. The basic play amount calculation unit 41 may calculate and store the basic play amount α in association with the vehicle speed. In this case, the steering angle command value setting unit 42 calculates and stores the basic play amount α in association with the target steering angle θ cmda When correcting the target steering angle θ, a basic play amount α according to the current vehicle speed is used. cmda may be corrected.

[0068] In addition, the present invention can be modified in various ways within the scope of the claims. [Explanation of symbols]

[0069] 1... power steering device, 2... steering wheel, 3... steering shaft, 8... steering mechanism, 9... electric motor, 21, 22... steered wheels, 25... rotation angle sensor, 41... basic play amount calculation unit, 42... steering angle command value setting unit, 101... automatic steering ECU, 102... motor control ECU

Claims

1. A steering shaft connected to the handlebars; A steering mechanism connected to the steering shaft for steering the left and right steered wheels; an electric motor for rotating the steering shaft; a steering angle detection unit for detecting a steering angle; an electric motor control unit for controlling the electric motor; A basic play amount calculation unit that calculates a basic play amount, The basic play amount calculation unit stores the steering angle as a first steering angle when a turn is made, determines whether or not the play is eliminated after the turn based on the steering angular velocity, stores the steering angle as a second steering angle when it is determined that the play is eliminated, and calculates the absolute value of the difference between the first steering angle and the second steering angle as the basic play amount.

2. 2. The vehicle steering device according to claim 1, wherein the basic play amount calculation unit calculates the basic play amount for each of a preset number of turning operations, and calculates an average value of the obtained multiple basic play amounts as a final basic play amount.

3. 3. The vehicle steering device according to claim 1 or 2, wherein the basic play amount calculation unit acquires a current value of the electric motor at time intervals, and determines that a turn has been performed when the value obtained by subtracting the previous current value from the current current value becomes negative for the first time after the value obtained by subtracting the previous current value from the current current value is positive, or when the value obtained by subtracting the previous current value from the current current value becomes positive for the first time after the value obtained by subtracting the previous current value from the current current value is negative.

4. 4. The vehicle steering system according to claim 3, wherein the current value of the electric motor is a current command value for the electric motor or an actual current value flowing through the electric motor.

5. 3. The vehicle steering device according to claim 1 or 2, wherein the basic play amount calculation unit acquires the steering angle at time intervals, and determines that a turn has been performed when the value obtained by subtracting the previous steering angle from the current steering angle becomes negative for the first time after the value obtained by subtracting the previous steering angle from the current steering angle becomes positive, or when the value obtained by subtracting the previous steering angle from the current steering angle becomes positive for the first time after the value obtained by subtracting the previous steering angle from the current steering angle becomes negative.

6. The vehicle steering device according to any one of claims 1 to 5, wherein the basic play amount calculation unit calculates the steering angular velocity at time intervals, and determines that the play has been eliminated when, after the turning is performed, the absolute value of the steering angular velocity becomes greater than a predetermined first threshold value, and then the absolute value of the steering angular velocity becomes equal to or less than a predetermined second threshold value that is equal to or less than the first threshold value.

7. the electric motor control unit controls the electric motor based on a given target steering angle, 7. The vehicle steering device according to claim 1, wherein the electric motor control unit includes a target steering angle correction unit that corrects the target steering angle based on the basic amount of play.

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