JP2022159939A - Vehicular steering device - Google Patents

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 basic 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 current value of the electric motor, 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

The present invention relates to a vehicle steering system.

Rigid axle suspensions in which left and right wheels are connected by axle beams are widely used in large vehicles such as trucks and buses. Vehicles having a rigid axle suspension widely employ a steering system equipped with a ball screw hydraulic power steering mechanism. The steering system of such a large vehicle is equipped with a steering wheel, steering column, steering gear box, pitman arm, drag ring, knuckle arm, tie rod, etc. Compared to the steering system of a passenger car, which uses independent suspension, complex. Moreover, the steering system for a large vehicle has a longer steering shaft and the like than the steering system for a passenger car.

Patent Literature 1 discloses a technique in which an electric motor is added to the steering column of the steering system of a large vehicle as described above, and the electric motor is used to automatically travel along a target trajectory. Such automatic travel control (automatic steering control) is performed, for example, as follows. That is, first, the target steering angle of the steered wheels is calculated from the relationship between the target trajectory and the position of the vehicle. calculate. 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.

JP-A-2006-264622 JP 2016-135676 A

As mentioned above, the steering system of a large vehicle is more complicated than that of a passenger car, and the torsion and deflection of the steering shaft are relatively large, resulting in a large allowance between the steering wheel and the steered wheels. . Therefore, when the above-described automatic travel control is performed on the steering system of a large vehicle, even if the target steering angle is given, the steering angle of the steered wheels does not match the target steering angle. Trajectory followability deteriorates. Incidentally, passenger cars also have a similar problem because there is play between the steering wheel and the steered wheels, though not as much as in large vehicles.

Therefore, in Patent Document 2, in order to improve the trajectory followability, if the steering dead zone is ΔH, the target steering angle is corrected by adding ΔH/2 to the target steering angle at the start of steering, and at the time of turning back, A technique for correcting the target steering angle by adding ΔH to the target steering angle is disclosed.
However, the basic play (steering dead zone), which is the play between the steering wheel and the steered wheels, changes due to various factors such as aging. In particular, for large vehicles such as trucks and buses, the play of the sector gear portion of the hydraulic power steering mechanism can be adjusted during maintenance, so the adjustment also changes the basic play.

In this specification, "starting to turn" means that the steering angle starts to change from a state in which the steering angle does not change. "Turnback" means that the steering angle changes so that the steering direction is reversed.
SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle steering system capable of accurately calculating a basic play amount that changes with aging.

An embodiment of the present invention comprises a steering shaft connected to a steering wheel, a steering mechanism connected to the steering shaft for steering left and right steered wheels, and 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 is performed, the steering angle is stored as a first steering angle, it is determined whether or not the slack is closed after the turning back based on the current value of the electric motor, and when it is determined that the slack is closed, the Provided is a vehicle steering system that stores a steering angle as a second steering angle, and calculates an absolute value of a difference between the first steering angle and the second steering angle as the basic play amount.

With this configuration, since the basic play amount, which is the play amount between the steering wheel and the steered wheels, can be calculated while the vehicle is running, it is possible to accurately calculate the basic play amount that changes over time.
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 amount calculation unit calculates the basic play amount for each of a plurality of preset steering turns, and averages the obtained basic play amounts. is calculated as the final basic play amount.
In one embodiment of the present invention, the basic play amount calculation unit acquires the steering angle at time intervals, and after a value obtained by subtracting the previous steering angle from the current steering angle is positive, , when the value obtained by subtracting the previous steering angle from the current steering angle becomes negative for the first time, or after the value obtained by subtracting the previous steering angle from the current steering angle becomes negative. When the value obtained by subtracting the previous steering angle from the steering angle becomes positive for the first time, it is determined that the steering wheel has been turned back.

In one embodiment of the present invention, the basic play amount calculation unit acquires the current value at time intervals, and after a value obtained by subtracting the previous current value from the current current value is positive, , when the value obtained by subtracting the previous current value from the current current value becomes negative for the first time, or after the value obtained by subtracting the previous current value from the current current value becomes negative, the current value When the value obtained by subtracting the previous current value from the current value becomes positive for the first time, it is determined that the switching has been performed.

In one embodiment of the present invention, the basic play amount calculation unit acquires the current value at time intervals, and subtracts the previous current value from the current current value after the switching is performed. When the absolute value of the value obtained is equal to or greater than a predetermined threshold value, it is determined that the play is closed.
In one embodiment of the present invention, the electric motor control section controls the electric motor based on a given target steering angle, and the electric motor control section controls the electric motor based on the basic play amount. It includes a target steering angle corrector that corrects the target steering angle.

In one embodiment of the present invention, there are a first control mode and a second control mode as steering control modes of the vehicle. In the first control mode, the target steering angle is corrected by the target steering angle correction section. In the second control mode, the target steering angle correction unit calculates the basic play amount without calculating the basic play amount by the basic play amount calculation unit. The target steering angle is corrected by

FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering system. FIG. 2 is a block diagram showing the electrical configuration of the vehicle steering system. FIG. 3 is a block diagram showing the electrical configuration of the motor control ECU. FIG. 4 is a graph showing the relationship between the steering angle _θh and the steering angle δ. FIG. 5 is a flow chart showing the procedure of basic play amount calculation processing executed by the basic play amount calculation section. FIG. 6 shows an example of steering angle θ _h , steering angle change amount Δθ _h , q-axis current command value I _q,cmd , change amount ΔI _q,cmd of q-axis current command value I _q , and steering angle δ. It is a time chart showing. FIG. 7 is a flowchart showing a procedure of steering angle command value setting processing executed by the steering angle command value setting section.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments 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 vehicle steering system. In FIG. 1, the left side of the dashed line 29 is a side view of the vehicle viewed from the side, and the right side of the dashed line 29 is a plan view of the vehicle viewed from above.
This vehicle steering apparatus 1 includes a steering wheel (steering wheel) 2, a steering column 4 having a steering shaft 3, a bevel gear portion 5, a power transmission shaft 6, a ball screw type hydraulic power steering mechanism (hereinafter referred to as "hydraulic power steering mechanism 7"). ), a steering mechanism 8, an electric motor 9, and the like.

The steering wheel 2 is connected to the input shaft of the bevel gear portion 5 via the steering shaft 3 . An output shaft of the bevel gear portion 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 , tie rod arms 16 and tie rods 17 .

One end of the pitman arm 11 is connected to the sector shaft of the hydraulic power steering mechanism 7 . One end of the drag link 12 is connected to the other end of the pitman arm 11 . The other end of the drag link 12 is connected to one end of a knuckle arm 13 of a right steerable wheel (right front wheel) 22 . The other end of the knuckle arm 13 is connected to the kingpin shaft 14 of the right steerable wheel 22 . The kingpin shaft 14 of the right steerable wheel 22 and the kingpin shaft 15 of the left steerable 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 the axle beam.

The electric motor 9 is provided on the steering column 4 and is connected to the steering shaft 3 via a speed reducer (not shown). A reduction gear consists of a worm gear mechanism including a worm gear and a worm wheel that meshes with the worm gear. In the following, R represents the speed reduction ratio of the speed reducer. 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. A rotor rotation angle θ _m of the electric motor 9 is detected by a rotation angle sensor 25 .

When the handle 2 rotates, this 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. This rocking of the pitman arm 11 moves the drag link 12 in the longitudinal direction, rocks the knuckle arm 13, and turns the steerable wheels 21 and 22. As shown in FIG.

When the electric motor 9 rotates, this rotational torque is transmitted to the steering shaft 3, so that the steerable wheels 21 and 22 are steered through the same power transmission path as described above. That is, by rotating the steering shaft 3 with the electric motor 9, the steered wheels 21 and 22 can be steered.
FIG. 2 is a block diagram showing the electrical configuration of the vehicle steering system.

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 section of the present invention.
The automatic steering ECU 101 outputs a mode signal S _mode indicating whether the steering mode is the automatic steering mode or the manual steering mode. Further, the automatic steering ECU 101 generates a target steering angle θ _cmda for automatic steering in the automatic steering mode.

The target steering angle θ _cmda is a target value of the steering angle (the rotation angle of the steering shaft 3) θ _h in the automatic steering mode. In this embodiment, the steering angle _θh is the amount of rotation (rotation angle) in both forward and reverse directions of the steering shaft 3 from the neutral position of the steering wheel 2 (steering neutral position), and the amount of rotation to the right from the neutral steering position. is represented by a positive value, and the amount of leftward rotation from the steering neutral position is represented by a negative value. In this embodiment, the steering angle θ _h is calculated from the rotor rotation angle θ _m detected by the rotation angle sensor 25 .

The mode signal S _mode and the target steering angle θ _cmda are given to the motor control ECU 102 .
The motor control ECU 102 also receives a key switch state detection signal _SK representing the state of the key switch of the vehicle. In this embodiment, the vehicle key switch is, for example, an ignition key for starting an engine (not shown) or a drive motor (not shown). The key switch may be an ignition key, an electronic key equipped with an immobilizer that emits an electric signal when authentication is obtained, or a push button that emits an electric signal.

When the key switch is turned on, a key switch state detection signal S _K (hereinafter referred to as "key switch on state signal") indicating this 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 "key switch off state signal") indicating this is input to the motor control ECU 102 .

The motor control ECU 102 drives and controls the electric motor 9 in the automatic steering mode based on the key switch state detection signal S _K , the mode signal S _mode , the target steering angle θ _cmda and the output signal of the rotation angle sensor 25 .
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 detector 33 that detects the motor current flowing through the electric motor 9. It has

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

The rotation angle calculator 51 calculates the rotation angle θ _m of the rotor of the electric motor 9 (hereinafter referred to as “rotor rotation angle θ _m ”) based on the output signal of the rotation angle sensor 25 . The rotor rotation angle _θm calculated by the rotation angle calculator 51 is given to the dq/UVW converter 48 , the UVW/dq converter 50 and the reduction ratio divider 52 .
The reduction ratio dividing unit 52 calculates the steering angle _θh by dividing the rotor rotation angle _θm calculated by the rotation angle calculation unit 51 by the reduction ratio R. The steering angle θ _h is given to a basic play amount calculation section 41 , a steering angle command value setting section 42 and an angle deviation calculation section 43 . The rotation angle sensor 25, the rotation angle calculator 51, and the reduction ratio divider 52 are examples of the steering angle detector of the present invention.

In this embodiment, the basic play amount calculator 41 calculates the play amount generated between the steering wheel 2 and the steered wheels 21 and 22 based on the steering angle _θh and the q-axis current command value _Iq,cmd , which will be described later. A basic play amount α is calculated. The details of the basic play amount calculator 41 will be described later.
A steering angle command value setting unit 42 sets a steering angle command value θ _cmd used for angle feedback control. In this embodiment, the steering angle command value setting unit 42 normally sets the target steering angle θ _cmda as the steering angle command value θ _cmd . However, when the steering mode is the automatic steering mode and the automatic steering is turned back after the basic play amount α is given from the basic play amount calculation unit 41, the steering angle command value setting unit 42 sets the basic play amount. The target steering angle θ _cmda is corrected based on the amount α. Then, the steering angle command value setting unit 42 sets the corrected target steering angle θ _cmda as the steering angle command value θ _cmd . The steering angle command value setting section 42 is an example of the "target steering angle correction section" of the present invention.

Details of the steering angle command value setting unit 42 will be described later. The steering angle command value θ _cmd set by the steering angle command value setting section 42 is given to the angle deviation calculation section 43 .
The angular deviation calculator 43 calculates a deviation Δθ (θ _cmd −θ _h ) between the steering angle command value θ _cmd and the steering angle θ _h .
The PD control unit 44 calculates the torque command value T _cmd by performing PD calculation (proportional differential calculation) on the angular deviation Δθ calculated by the angular deviation calculating unit 43 .

Based on the torque command value T _cmd , the current command value setting unit 45 sets the d-axis current command values I _{d, cmd} and the q-axis current command values I _{q, cmd} (hereinafter collectively referred to as “two-phase current command values I _dq,cmd ”).
Specifically, the current command value setting unit 45 sets the q-axis current command value _Iq,cmd to a significant value, while setting the d-axis current command value _Id,cmd to zero. More specifically, the current command value setting unit 45 divides the torque command value _{T cmd} calculated by the PD control unit 44 by the torque constant KT of the electric motor 9 to obtain the q-axis current command value I _{q , cmd} . The two-phase current command values I _{dq and cmd} set by the current command value setting section 45 are given to the current deviation calculation section 46 . The q-axis current command value _Iq,cmd set by the current command value setting section 45 is also given to the basic play amount calculation section 41 . The q-axis current command value _Iq,cmd is an example of the "electric motor current value" and the "current command value" in the present invention.

The current detection unit 33 detects a _U -phase current IU, a _V -phase current IV, and a _W -phase current IW of the electric motor 9 (hereinafter collectively referred to as "three-phase detection current _IUVW "). do. The three-phase detection current I _UVW detected by the current detector 33 is applied to the UVW/dq converter 50 .
The UVW/dq conversion unit 50 converts the three-phase detection current _IUVW ( _U -phase current IU, _V -phase current IV and _W -phase current IW) in the UVW coordinate system detected by the current detection unit 33 to the dq coordinate system. are coordinate-transformed into two-phase detection currents I _d and I _q (hereinafter collectively referred to as “two-phase detection currents I _dq ”). The rotor rotation angle _θm calculated by the rotation angle calculator 51 is used for this coordinate conversion. The two-phase detection current I _dq (d-axis detection current I _d and q-axis detection current I _q ) calculated by the UVW/dq conversion section 50 is provided to the current deviation calculation section 46 .

The current deviation calculator 46 calculates the deviation between the two-phase current command values I _{dq and cmd} set by the current command value setting part 45 and the two-phase detected current I _dq given from the UVW/dq converter 50 . More specifically, the current deviation calculator 46 calculates the deviation of the d-axis detection current _{Id from the d-axis current command values Id, cmd and} the deviation of the _q -axis detection current Iq from the q-axis current command values _{Iq, cmd} . to calculate These deviations are given to the PI control section 47 .

The PI control unit 47 performs PI (proportional integral) calculation on the current deviation calculated by the current deviation calculation unit 46 to obtain two-phase voltage command values V _dq,cmd (d-axis voltage command A value V _d,cmd and a q-axis voltage command value V _q,cmd ) are generated. The two-phase voltage command values V _{dq, cmd} are given to the dq/UVW converter 48 .
The dq/UVW converter 48 coordinates-transforms the two-phase voltage command value _Vdq,cmd into the three-phase voltage command value _VUVW,cmd . The rotor rotation angle _θm calculated by the rotation angle calculator 51 is used for this coordinate conversion. The three-phase voltage command value _VUVW,cmd consists of a U-phase voltage command value _VU,cmd , a V-phase voltage command value VV _,cmd, and a W-phase voltage command value _VW,cmd . This three-phase voltage command value V _UVW,cmd is given to the PWM control section 49 .

PWM control unit 49 outputs a U-phase PWM control signal and a V-phase PWM control signal having duties corresponding to U-phase voltage command value _VU,cmd , V-phase voltage command value VV _,cmd, and W-phase voltage command value _VW,cmd , respectively. A control signal and a W-phase PWM control signal are generated and supplied to the drive circuit 32 .
The drive circuit 32 consists of a three-phase inverter circuit corresponding to the U-phase, V-phase and W-phase. The power elements constituting this inverter circuit are controlled by the PWM control signal given from the PWM control unit 49, so that the voltage corresponding to the three-phase voltage command value _VUVW,cmd is applied to the stator windings of each phase of the electric motor 9. will be applied to

The angle deviation calculator 43 and the PD controller 44 constitute angle feedback control means. The electric motor 9 is controlled by the action of the angle feedback control means so that the steering angle θ _h approaches the steering angle command value θ _cmd set by the steering angle command value setting section 42 .
The basic play amount calculator 41 and the steering angle command value setter 42 will be described in detail below.

FIG. 4 is a graph showing the relationship between the steering angle _θh and the steering angle (tire angle) δ.
FIG. 4 shows that after continuously changing the steering angle θ _h from the steering neutral position O to a predetermined positive steering angle θ _hp larger than zero, the steering angle θ _h is changed to a predetermined negative steering angle smaller than zero. The trajectory of the steering angle δ is shown when the steering angle θh is changed continuously up to _θhm , and the steering angle _θh is continuously changed toward the positive side steering angle _θhp .

There is play between the steering wheel 2 and the steered wheels 21 and 22 . Therefore, even if the steering angle _θh increases from 0°, the steering angle δ does not increase immediately. That is, in the steering start state, even if the steering angle _θh changes, the steering angle δ does not change immediately. When the steering angle _θh increases and the slack is reduced (point A), the steering angle δ begins to increase.
Then, when the steering angle _θh reaches the positive side steering angle _θhp (point B) and the steering operation is performed, the steering angle _θh is decreased. In this case also, there is play, so the steering angle δ does not decrease immediately. That is, in the steering-back state, even if the steering angle _θh changes, the steering angle δ does not change immediately. When the steering angle _θh decreases and the slack is reduced (point C), the steering angle δ begins to decrease. Therefore, when the steering angle δ becomes zero (point D), the steering angle _θh becomes zero or less.

When the steering angle _{θh reaches the negative side steering angle θhm (} point E) and the steering operation is performed, the steering angle _θh is increased. In this case, too, there is play, so the steering angle δ does not increase immediately. When the steering angle _θh increases and the slack is reduced (point F), the steering angle δ begins to increase.
The absolute value of the amount of change in the steering angle _θh between points A and D (or points B and C, or points F and E) is the basic play amount α.

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

Next, the basic play amount calculator 41 acquires the q-axis current command value _{Iq, cmd} and the steering angle _θh (step S3). Then, the basic play amount calculation unit 41 determines whether or not the steering wheel has been turned back (step S4).
Whether or not the switching has been performed is determined, for example, as follows. That _{is ,} the steering angle change _{amount Δθ Let h} . After the steering angle change amount Δθ _{h becomes negative for the first time after the steering angle change amount Δθ h is} positive, or after the steering angle change amount Δθ _h becomes negative, the basic play amount calculation unit 41 calculates , and when the steering angle change amount _Δθh becomes positive for the first time, it is determined that the steering has been performed.

The basic play amount calculation section 41 may determine whether or not the steering wheel has been turned back as follows. That is, the value (I q _, cmd( _{i )} −I _{q , cmd(i−1)} ) is the q-axis current command value change amount ΔI _{q, cmd} . The basic play amount calculation unit 41 calculates when the q-axis current command value change amount ΔI q,cmd becomes negative for the first time after the q-axis current command value change amount ΔI q, _cmd is positive, or when the q-axis current command value change amount ΔI _q,cmd becomes negative for the first time. When the q-axis current command value change amount ΔI _q,cmd becomes positive for the first time after the command value change amount ΔI _q,cmd has been negative, it is determined that the steering has been performed.

In this case, instead of the q-axis current command value change amount ΔI _{q, cmd} , the change amount of the q-axis detection current I _q (q-axis detection current change amount ΔI _q ) calculated by the UVW/dq conversion unit 50 is used. may In that case, in step S3, the q-axis detection current _Iq is obtained instead of the q-axis current command values _{Iq, cmd} .
If it is determined that the steering wheel has not been turned back (step S4: NO), the basic play amount calculation unit 41 returns to step S3.

If it is determined in step S4 that the steering wheel has been turned back (step S4: YES), the basic play amount calculation section 41 increments n by 1 (step S5). Then, the basic play amount calculation unit 41 stores the steering angle θ _h obtained most recently in step S3 as the first steering angle θ _ha (step S6).
Next, the basic play amount calculator 41 acquires the q-axis current command value _{Iq, cmd} and the steering angle _θh (step S7). Based on the q-axis current command value _Iq,cmd , the basic play amount calculation unit 41 determines whether or not the play is full (step S8).

Whether or not the play is full is determined, for example, as follows. The absolute value |I _{q, cmd} | of the q-axis current command value I _{q, cmd} maintains a relatively small value immediately after the steering wheel because there is a slack, and increases rapidly when the slack is closed because the load increases. . Therefore, the basic play amount calculation unit 41 subtracts the q-axis current command value _{Iq,cmd(i−1)} acquired last time from the q-axis current command value _Iq,cmd(i) acquired this time, and calculates the absolute value of the value. |I _q , _{cmd (i)} −I _{q, cmd (i−1)} | is equal to or greater than a threshold value A (A>0), it is determined that the play is full. However, in step S8 immediately after it is determined that the steering has been performed, the change amount absolute value |ΔI _q,cmd | of the q-axis current command value I _q,cmd is set to zero.

Note that instead of the absolute value of change |ΔI _{q, cmd} | of the _q -axis current command values I _{q, cmd} , the absolute value of change _| |(the absolute value of the value obtained by subtracting the q-axis detection current I _q(i−1) obtained last time from the q-axis detection current I _q(i) obtained this time) may be used. In that case, in step S7, the q-axis detection current _Iq is obtained instead of the q-axis current command values _{Iq, cmd} . In this case, the _q -axis detection current Iq is an example of the "current value of the electric motor" and the "actual current value flowing through the electric motor" in the present invention.

If it is determined that the slack is not full (step S8: NO), the basic slack amount computing section 41 returns to step S7. When the q-axis current command values _{Iq, cmd} and the steering angle _θh are repeatedly obtained by returning from step S8 to step S7, the cycle of obtaining the q-axis current command values _{Iq, cmd} and the steering angle _θh is constant.
In step S8, when it is determined that the play is full (step S8: YES), the basic play amount calculation unit 41 sets the steering angle θ _h acquired most recently in step S7 as the second steering angle θ _hb. Store (step S9). Then, the basic play amount calculation unit 41 calculates and stores the absolute value |θ _hb −θ _ha | of the difference between the first steering angle θ _ha and the second steering angle θ hb as the basic play amount _αn (step S10).

Next, the basic play amount calculation unit 41 determines whether or not 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 calculator 41 determines whether or not a key switch off state signal has been input (step S12). If the key switch off state signal has not been input (step S12: NO), the basic play amount calculation section 41 returns to step S3.

If it is determined in step S11 that n has reached N (step S11: YES), the basic play amount calculation section 41 calculates the N basic play amounts α ₁ to α _N calculated so far. , {(α _{1 +} α ₂ + . Then, the basic play amount calculation unit 41 ends the current basic play amount calculation process.

If it is determined in step S12 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 an example of steering angle θ _h , steering angle change amount Δθ _h , q-axis current command value I _q,cmd , change amount ΔI _q,cmd of q-axis current command value I _q , and steering angle δ. It is a time chart showing.

In the example of FIG. 6, after the steering angle _θh increases from time t0 to time t1, the steering angle _θh remains constant from time t1 to time t2. The steering angle θ _h decreases from time t2 to time t3, remains constant from time t3 to time t4, increases from time t4 to time t5, remains constant from time t5 to time t6, and decreases from time t6. is doing.
The steering angle change amount Δθ _h is substantially constant and positive from time t0 to time t1. At time t1, the steering angle change amount Δθ _h decreases to approximately zero, and this value is maintained until time t2. At time t2, the steering angle change amount _Δθh becomes a negative value, and this value is maintained until time t3. At time t3, the steering angle change amount _Δθh increases to zero, and this value is maintained until time t4. At time t4, the steering angle change amount _Δθh becomes a positive value, and this value is maintained until time t5. At time t5, the steering angle change amount Δθ _h decreases to zero, and this value is maintained until time t6. At time t6, the steering angle change amount Δθ becomes a negative value and holds that value.

Time t2 corresponds to when the steering angle change amount Δθ becomes negative for the first time after the steering angle change amount Δθ has been positive. Therefore, at time t2, it is determined that the vehicle has been switched back (see step S4 in FIG. 5). Therefore, the steering angle θ _h acquired at that time (more precisely, immediately before) is stored as the first steering angle θ _ha (see step S6 in FIG. 5).
The _q -axis current command value Iq holds a certain positive value from time t0 to time t1, and is substantially zero from time t1 to just before time t7, which is slightly after time t6. Then, after sharply decreasing near time t7, it increases slightly and reaches a constant value.

As a result, the amount of change ΔI _q,cmd in the q-axis current command value I _q abruptly drops below the threshold value −A at time t7 after the switchover. That is, at time t7, the absolute value of change |ΔI _{q,cmd |} Therefore, at time t7, it is determined that the slack is closed (see step S8), and the steering angle θ _h acquired at that time (more precisely, just before that) is stored as the second steering angle θ _hb (see step S8 in FIG. 5). See step S9). Then, the absolute value of the difference between the first steering angle _θha and the second steering angle _θhb is calculated as the basic play amount (see step S9 in FIG. 5).

The steering angle δ increases from time t0 to t1. Then, it becomes a constant value from time t1 to time t7. At time t2, the steering wheel is turned back, but the turning angle δ is a constant value until time t7 when the free play is closed. When the play becomes tight (time t7), the steering angle δ decreases.
FIG. 7 is a flow chart showing the procedure of the steering angle command value setting process executed by the steering angle command value setting section 42. As shown in FIG.

When the key switch ON state signal is input (step S21), the steering angle command value setting section 42 determines whether or not the basic play amount α is given from the basic play amount calculation section 41 (step S22).
If the basic play amount α is not given (step S22: NO), the steering angle command value setting unit 42 sets the target steering angle θ _cmda as the steering angle command value θ _cmd (step S23). As a result, the target steering angle θ _cmda is given to the angle deviation calculator 43 as it is as the steering angle command value θ _cmd .

After that, the steering angle command value setting unit 42 determines whether or not the key switch OFF state signal is input (step S24). If the key switch off state signal has not been input (step S24: NO), the steering angle command value setting section 42 returns to step S22.
If it is determined in step S24 that the key switch OFF state signal has been input (step S24: YES), the steering angle command value setting section 42 terminates the current steering angle command value setting process.

If it is determined in step S22 that the basic play amount α is given (step S22: YES), the steering angle command value setting unit 42 acquires the steering angle _θh (step S25). Then, it is determined whether or not switching has been performed (step S26). Determination as to whether or not the switching has been performed can be performed in the same manner as in step S4 in FIG. When determining whether or not the steering has been performed based on the q-axis current command values _{Iq, cmd} or the q-axis detection current _Iq , in step S25, in addition to the steering angle _θh , the q-axis The current command values _{Iq, cmd} or the _q -axis detection current Iq may be obtained.

When it is determined that the steering wheel is not turned back (step S26: NO), the steering angle command value setting unit 42 sets the target steering angle θ _cmda as the steering angle command value θ _cmd (step S27). As a result, the target steering angle θ _cmda is given to the angle deviation calculator 43 as it is as the steering angle command value θ _cmd . Then, the steering angle command value setting unit 42 proceeds to step S32.

At 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.
If it is determined in step S26 that the steering has been performed (step S26: YES), the steering angle command value setting unit 42 determines whether the steering mode is the automatic steering mode based on the mode signal S _mode . is determined (step S28).

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 as the steering angle command value θ _cmd . After that, the steering angle command value setting unit 42 proceeds to step S32 and determines whether or not the key switch off state signal is 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.

If it is determined in step S28 that the steering mode is the automatic steering mode (step S28: YES), the steering angle command value setting section 42 determines the planned steering direction (step S29). Specifically, the steering angle command value setting unit 42 determines that the planned steering direction is the right steering direction if θ _cmda −θ _h >0, and determines that the planned steering direction is the right steering direction if θ _cmda −θ _h <0. is determined as the left steering direction. If θ _cmda −θ _h =0, it is determined that the planned steering direction is the previous steering direction.

If it is determined that the planned steering direction is the right steering direction (step S29: YES), the steering angle command value setting section 42 uses the basic play amount α given from the basic play amount calculation section 41, A steering angle command value θ _cmd is set based on equation (1) (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. A steering angle command value θ _cmd that is the corrected target steering angle θ _cmda is provided to the angle deviation calculator 43 .

If it is determined in step S29 that the expected steering direction is the left steering direction (step S29: NO), the steering angle command value setting section 42 sets the basic play amount α is used to set the steering angle command value θ _cmd based on the following equation (2) (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. A steering angle command value θ _cmd that is the corrected target steering angle θ _cmda is provided to the angle deviation calculator 43 .

In step S32, if the key switch OFF state signal has not been input (step S32: NO), the steering angle command value setting section 42 returns to step S25.
If it is determined in step S32 that the key switch OFF state signal has been input (step S32: YES), the steering angle command value setting section 42 terminates the current steering angle command value setting process.

According to this embodiment, the basic play amount α, which is the play amount between the steering wheel 2 and the steered wheels 21 and 22, can be calculated while the vehicle is running. As a result, it is possible to accurately calculate the basic play amount that changes due to aging or the like. By correcting the target steering angle using the basic play obtained in this way, it becomes possible to improve the locus followability.

Although the embodiments of the present invention have been described above, the present invention can also be implemented in other forms. For example, in the above embodiment, the present invention is applied to a vehicle steering system provided with a hydraulic power steering mechanism 7, but the present invention is also applicable to a vehicle steering system having an electric power steering system. can do. In that case, automatic steering is performed using the electric motor of the electric power steering device.

In the above-described embodiment, the average value of a plurality of basic play amounts α calculated for each of a plurality of predetermined times of steering is set as the final basic play amount α. However, the basic play amount α calculated for one steering cycle may be set as the final basic play amount α.
In the above-described embodiment, when the key switch ON state signal is input, the basic play amount calculation processing is performed by the basic play amount calculation section 41, and the basic play amount calculation section 41 calculates the final basic play amount α. After that, the target steering angle θ _cmda is corrected using the basic play amount α.

However, there are a first control mode and a second control mode as the _steering control mode of the vehicle. In the second control mode, the target steering angle θ _cmda is calculated by the steering angle command value setting unit 42 without performing the basic play amount calculation processing by the basic play amount calculation unit 41 . You may make it correct|amend.

In this case, the second control form is, for example, a control form in which a precise docking control system of the automatic steering control is performed, and the first control form is a control form other than the precise docking control of the automatic steering control. It may be in a controlled form. Correct arrival control is control for stopping a vehicle such as a bus exactly at a predetermined place (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 sent from the automatic steering ECU 101 to the motor control ECU 102 .

When the vehicle is equipped with an electric power steering device and automatically steered using an electric motor of the electric power steering device, the first control mode is a control mode in which manual control is performed, and the second control mode is a control mode in which manual control is performed. The form may be a control form in which automatic operation is performed.
Further, the basic play amount calculation section 41 may calculate and store the basic play amount α in association with the vehicle speed. In this case, when correcting the target steering angle θ cmda, the steering angle command value setting unit 42 may correct the target steering angle θ _cmda using the basic _allowance α corresponding to the current vehicle speed.

In addition, the present invention can be modified in various ways within the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Power steering apparatus 2... Handle 3... Steering shaft 8... Steering mechanism 9... Electric motor 21, 22... Steering wheel 25... Rotation angle sensor 41... Basic play amount calculating part 42... Steering Angle command value setting unit 101 Automatic steering ECU 102 Motor control ECU

Claims (7)

a steering shaft connected to the steering wheel;
a steering mechanism connected to the steering shaft for steering left and right steerable wheels;
an electric motor for rotating the steering shaft;
a steering angle detection unit for detecting a steering angle;
an electric motor control unit that controls 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 the steering wheel is turned back, and determines whether or not the play is closed after the steering wheel is turned based on the current value of the electric motor, A steering system for a vehicle, which stores the steering angle as a second steering angle when it is determined that the play is full, and calculates an absolute value of a difference between the first steering angle and the second steering angle as the basic play amount. . 2. The vehicle steering system according to claim 1, wherein the current value of said electric motor is a current command value for said electric motor or an actual current value flowing through said electric motor. The basic play amount calculation unit calculates the basic play amount for each of a plurality of preset steering turns, and calculates an average value of the obtained plurality of basic play amounts as a final basic play amount. 3. The vehicle steering system according to claim 1, wherein the calculation is performed as follows. The basic play amount calculation unit obtains the steering angle at time intervals, and after a value obtained by subtracting the previous steering angle from the current steering angle is positive, calculates When the value obtained by subtracting the steering angle of becomes negative for the first time, or after the value obtained by subtracting the previous steering angle from the current steering angle becomes negative, the previous steering angle from the current steering angle 4. The vehicle steering system according to any one of claims 1 to 3, wherein when the value obtained by subtracting the angle becomes positive for the first time, it is determined that the steering has been performed. The basic play amount calculation unit acquires the current value at time intervals, and after a value obtained by subtracting the previous current value from the current current value is positive, subtracts the current value from the previous current value. When the value obtained by subtracting the current value of becomes negative for the first time, or after the value obtained by subtracting the previous current value from the current current value is negative, the previous current from the current value 4. The vehicle steering system according to any one of claims 1 to 3, wherein when the value obtained by subtracting the value becomes positive for the first time, it is determined that the steering has been performed. The basic play amount calculation unit acquires the current value at time intervals, and after the turning is performed, the absolute value of the value obtained by subtracting the previous current value from the current current value is a predetermined value. 6. The vehicle steering system according to any one of claims 1 to 5, wherein it is determined that the slack is full when the threshold value of is exceeded. The electric motor control unit controls the electric motor based on a given target steering angle,
The vehicle steering system according to any one of claims 1 to 6, wherein said electric motor control section includes a target steering angle correction section that corrects said target steering angle based on said basic amount of play.

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