JP4876432B2 - Steering control device - Google Patents

Description

  The present invention belongs to the technical field of a steering control device using a steer-by-wire system in which the steering unit and the steered unit are not mechanically coupled and the operation of the steering unit and the steered unit can be arbitrarily set. .

  The steer-by-wire system, which is not mechanically connected between the steering wheel and the tire and can arbitrarily set the operation of the steering wheel and the tire, has an actuator for operating the steering wheel and the tire, respectively. The vehicle is steered by controlling the actuator.

The general control flow of a steer-by-wire system is as follows.
1. For the input to the steering wheel, the command angle to the steered side is calculated and determined.
2. The actuator on the steered side operates according to this command angle, and follows the command angle by servo control.
3. The steering torque applied to the rack is detected by the movement of the tire, and the steering wheel actuator is operated from the command value obtained based on the signal to simulate the steering reaction force.
4. According to the road surface reaction force described above, the driver can perform driving operations according to the road surface condition.

In this steer-by-wire system, a system in which a torque sensor is set at a position corresponding to a pinion shaft is known as means for detecting information from the road surface (see, for example, Patent Document 1).
JP-A-11-78947

  However, in the conventional steering control device, when the reaction force actuator is controlled, a steering reaction force torque serving as a command is generated based on the torque sensor. However, since there is hysteresis in the output characteristics of the torque sensor, when the torque sensor output is used to control the steering reaction force, for example, the start of turning from the neutral position of the steering wheel becomes lighter, and the feeling of response is reduced. There was a problem that the steering feeling of the driver deteriorated.

  The present invention has been made paying attention to the above problem, and by correcting the steady deviation characteristic of the torque sensor, a desired steering reaction force is set, and the steering control that can improve the steering feeling by the driver. An object is to provide an apparatus.

In order to achieve the above object, in the present invention,
A steering unit that is mechanically separated from the steering unit and steers the steered wheels according to steering;
Steering torque detection means for detecting the steering torque of the steering unit;
Steering reaction force setting means for setting a steering reaction force according to the steering torque;
Steering reaction force applying means for applying a steering reaction force of the steering unit based on the steering reaction force setting value;
In a steering control device with
A steering torque estimation means for estimating the actual steering torque is provided,
The turning torque detection means has a predetermined steady deviation between the turning torque detection value and the actual turning torque,
The steering reaction force setting means, the steering torque detection value, have a steering reaction force correction unit for correcting in accordance with the occurrence of the predetermined steady-state error,
The steering reaction force correction unit calculates a steady-state deviation correction amount calculated in a previous calculation cycle based on the steady-state deviation correction amount according to the state of occurrence of the predetermined steady-state deviation when the steering angle is in a region where the steering angle changes from a neutral position. And based on the estimated steering torque value .

  Therefore, in the steering control device of the present invention, the steering torque detection value of the steering reaction force correction unit of the steering reaction force setting unit is determined according to the state of occurrence of the predetermined steady deviation of the steering torque detection unit. It is corrected. That is, since the steering reaction force setting value is generated based on the steering torque detection value from the steering torque detection means, the steering reaction force setting value is not output while the output of the steering torque detection value is not output. It will be. For this reason, while the output of the steering torque detection value is not output, a dead zone is obtained and the vicinity of the neutral lightens. On the other hand, in the steering reaction force correction unit, the steering reaction force torque is compensated when the steering wheel is turned off by compensating for the portion where the steering torque does not occur due to the steady deviation of the steering torque detection means, thereby reducing the rise dead zone. can do. As a result, by correcting the steady deviation characteristic of the torque sensor, a desired steering reaction force is set, and the steering feeling by the driver can be improved.

  Hereinafter, the best mode for carrying out the steering control device of the present invention will be described based on Examples 1 to 3 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall schematic diagram showing a steer-by-wire system to which the steering control device of the first embodiment is applied.
As shown in FIG. 1, the steering control device according to the first embodiment includes a steering wheel angle sensor 1 (steering angle detection means), a steering torque sensor 2, a steering reaction force actuator 3 (steering reaction force applying means), and a steering reaction force. Force motor angle sensor 4 (steering angle detection means), steering actuator 5, steering actuator angle sensor 6, turning torque sensor 7 (steering torque detection means), pinion angle sensor 8, and tie rod axial force A sensor 9, a mechanical backup 10, a controller & drive circuit 11, a steering wheel 12, a tire 13 (steering wheel), and a vehicle state parameter 14 (vehicle speed detection means, road surface friction coefficient estimation means) are provided. Yes.

  The vehicle state parameter 14 means a parameter obtained from the vehicle state based on the vehicle speed, the lateral acceleration, and the like as well as the vehicle speed and the lateral acceleration.

  The controller & drive circuit 11 performs steer-by-wire control. In normal steer-by-wire control, the handle angle generated by the rotation of the steering wheel 12 is detected by the handle angle sensor 1 installed on the shaft of the steering reaction force actuator 3, and the detected value is calculated and processed (for example, Variable steering angle ratio control, differential handle control, etc.), and generates a steering command to the steering actuator 5. A current (or voltage) command is sent to the drive circuit so that the steered side steering actuator angle sensor 6 installed on the shaft of the steered actuator 5 follows this steered command value, and the steered actuator 5 is driven. To do. At this time, the road surface condition is detected by the turning torque sensor 7, and a calculated signal or a current (or voltage) command by open loop control is given to the steering reaction force actuator 3.

Next, the operation will be described.
[Remarks of the present invention]
Conventionally, as described in Japanese Patent Application Laid-Open No. 11-78947, a command value is determined by detecting a road surface condition with a torque sensor installed at a location corresponding to a pinion shaft. The steering reaction force actuator is driven in accordance with the command to give the driver a road feeling.
However, when a torque sensor is used, since there is a hysteresis unique to the sensor, the driver's start of turning the steering wheel becomes light and a sufficient steering feeling cannot be obtained.

The present invention relates to the correction of the steering reaction force at the start of turning the steering wheel, and the focus of the present invention will be described below.
FIG. 2 shows the input / output characteristics of the torque sensor.
In simple terms, the torque sensor detects the amount of twist and outputs a value by twisting a relatively soft metal called a torsion bar inserted into the shaft. Ideally, it is desirable that the input / output characteristics of the torque sensor be 1: 1.
However, the torque sensor has a state in which no output is produced when it is changed from the zero input state ((1) to (2)). This is called output hysteresis with respect to input, and “hysteresis (= steady deviation)” appearing in the text after this indicates this. Incidentally, FIG. 2 moves in the order of (1) → (2) → (3) → (4) → (5).
When the input exceeds a certain hysteresis value (= predetermined steady-state deviation), output torque starts to appear, but is always lower than ideal torque and forward torsion (per Fig. 2: (1)) , It has a characteristic that rises to the torsion in the reverse direction (Fig. 2: (3) to (4)).

FIG. 3 is a diagram showing a sine wave of the input steering angle and the output torque. Attention is paid to the shaded area in FIG. 3 (FIG. 3: X).
The steering angle (which will be described using a steering wheel angle as a representative example) and the torque (solid line) actually output from the sensor are shown. A steering reaction force is generated based on the actually output sensor value. By the way, in general, when generating the steering reaction force, the characteristics of the spring are used as a basis, and the viscous reaction force and friction force are added to optimize the steering reaction force characteristics for the driver. In order to make it easy to understand, the above-mentioned forces such as the viscous force and the friction force are not considered here, and will be explained only by the term of the spring.
Since the viscous force and friction force are simply added to the spring term, they can be added in the same way as before even after the present invention is applied.

The dotted line shows an ideal output waveform (FIG. 3: a), and the solid line shows the torque (FIG. 3: b) that is actually output.
The handle angle is increased from the neutral position (the neutral position is assumed when the handle angle is zero) in the forward direction, switched back in the neutral direction, increased in the reverse direction, and switched back in the neutral direction. To work.
At this time, ideally, it is desirable that the torque rises at the same time as the start of cutting, but immediately after increasing from neutral, the actual torque sensor has no output due to hysteresis, and output occurs after a while ( FIG. 3: c).
Since the steering reaction force torque is generated based on the output of the torque sensor, the steering reaction force is not output while the output is not output. Therefore, it becomes a dead zone and becomes the characteristic that the neutral vicinity becomes light.
In the present invention, a configuration is shown in which the portion where the torque sensor does not come out is compensated for, so that the torque value is compensated when the handle is turned off and the dead zone is reduced.

FIG. 4 is an enlarged view of the portion X in FIG. These are time series waveforms of the steering wheel angle (considered as input torque) and output torque. Although the angle is shown in FIG. 3, if it is desirable that the torque rises simultaneously with the steering angle, it can be said that the input torque shown in FIG. Therefore, in FIG. 4, the input torque will be described.
Each of the two waveforms (FIG. 4: I and II) in FIG. 4 shows the case where the steering wheel is made faster and the case where it is made slower.
The input torque at the point where the input enters and the output torque comes out becomes hysteresis (FIG. 4: X).
When the steering wheel is quickly steered, the hysteresis immediately rises up to the hysteresis, so that the actual output torque also appears faster by that amount (FIG. 4: a, A). Further, in the case of slow steering, since it takes time to reach the hysteresis this time, it takes time until the actual torque is generated, and the dead zone state continues throughout that time (FIG. 4: b, B).

[Basic Concept of Steering Torque Correction in Example 1]
FIG. 5 shows a basic concept of steering torque correction in the first embodiment.
In the figure, an output value of the turning torque sensor 7 (FIG. 5: A) and a time series of values corrected for the output value (FIG. 5: B) are shown.
The hysteresis characteristic of the turning torque sensor 7 can be detected or specified in advance as a certain constant value.
The basic equation indicating the hysteresis correction amount ΔT (n) (= steady deviation correction amount) in the first embodiment is as follows.
ΔT (n) = ΔT (n−1) + sgn · ΔTo · G (φ, v, μ) · Δt (1)
To is the hysteresis value of the steering torque sensor 7 itself. It is set from the input / output characteristics of the steering torque sensor 7 to be used.
As shown in FIG. 5, ΔTo is a steering torque correction value corresponding to a change in steering torque when steering from neutral, and the steering angular speed (steering angular speed, steering angular speed, etc.) It is determined based on the characteristics of the steering system of the vehicle and the characteristics of the steering motor, as long as the steering angular speed at the steering system rotating shaft up to the torque sensor is sufficient.
G (φ, ν, μ) is a correction gain, and the magnitude of the steering torque correction value ΔTo is changed by the steering angle φ, the vehicle speed ν, and the road surface friction coefficient μ. This is also shown in the form of a map, which is shown in FIGS. 7, 8, and 9 as described above.
n is a count value indicating how many samplings have passed. n · Δt (Δt is a sampling time) represents an elapsed time from the round-up.
Sgn represents the sign of the hysteresis correction amount ΔT (n). This is set for adjustment when negative correction is performed at the time of switching back. When the rudder angular velocity is negative, sgn is also negative.

Using the above equation (1), the inclination is calculated for each period, and the hysteresis correction amount ΔT (n) is calculated at each sampling time point.
Further, the steering torque value after the hysteresis correction is positioned as an estimated value, and this value is fed back to the steering reaction torque. The calculated steered torque estimated value T? Trq is basically expressed by the following equation.
T? Trq = Tsensor + ΔT (n) (2)
Tsensor is a steering torque sensor value from the steering torque sensor 7. And if a certain condition is satisfied, it will transfer to the following formulas.
T? Trq = Tsensor + sgn × To (3)

Next, how the magnitude of the hysteresis correction amount ΔT (n) changes according to this parameter will be described below.
The hysteresis correction amount ΔT (n) increases as the turning torque estimated by the turning torque estimation means increases. Speaking of the above equation (1), the inclination to be corrected is increased.
For example, the following situations can be considered as situations where it can be estimated that the turning torque is large (increasing the slope of the hysteresis correction amount ΔT (n)).
1. When rudder angular velocity is high
2. When the rudder angle is large
3. When the vehicle speed is low or the vehicle speed is high
4. When the road friction coefficient is high

A description will be given below of what characteristics the map has when expressed on the basis of the characteristics of the above four conditions.
FIG. 6 shows a map of the steering torque correction value ΔTo using the absolute value of the steering angular velocity as a parameter.
This value is set from the characteristic of the change in turning torque when the steering is input from the traveling at the neutral / medium speed of the applied vehicle.
As described above, since the steering torque is small where the steering angular velocity is low, the change in the steering torque correction value ΔTo is also small (FIG. 6: a). In addition, since the steering torque is large where the steering angular velocity is high, the change in the steering torque correction value ΔTo is also increased (FIG. 6B).
Here, the steering angular velocity includes those corresponding to the angular velocity on the side of the steering wheel 12 with respect to the torsion bar of the steering torque sensor 7, such as the steering wheel angular velocity, the steering motor angular velocity, and the steering motor command angular velocity.

FIG. 7 shows a map of the steering angle correction gain Gφ using the steering angle as a parameter.
Here, the steering angle includes a steering wheel angle, a steering motor angle, a steering motor command angle, and the like corresponding to an angle at least on the steering wheel 12 side with respect to the torsion bar of the steering torque sensor 7.
The steering angle neutral is set to 1 (FIG. 7: b), and the gain is set to increase as the steering angle increases (FIG. 7: a). For example, when the vehicle is turned in a stopped state, the steering reaction force increases as the steering angle increases and the steering angle increases, so that the steering reaction force can be corrected accordingly.
Further, the supplement at the change point can be arbitrarily performed. For example, FIG. 7 also shows complementation by a curve (FIG. 7: c), a straight line (FIG. 7: e), and a function (FIG. 7: d).
Furthermore, change points (FIG. 7: f, g) can be moved to the left and right, respectively, and the position of the change point can be changed.

FIG. 8 shows a map of the vehicle speed correction gain Gv using the vehicle speed as a parameter.
The absolute value of the steering torque at the vehicle speed is highest when the vehicle speed is 0 [km / h] (stationary state), and when the vehicle speed starts to increase, the torque decreases and the vehicle speed increases and the vehicle runs at high speed. It can be said that the steering torque has a characteristic of increasing again in response to (Fig. 8: ad). Therefore, setting the vehicle speed correction gain map that changes with the vehicle speed always reflects the state of the vehicle speed, and is effective in increasing or decreasing the hysteresis correction amount ΔT (n).
There are at least two changing points, and linear interpolation is performed between the set vehicle speed correction gains. Although it is shown by a straight line in FIG. 8, there are naturally a method of smoothing the connection of each change point and a method of complementing with a curve.

FIG. 9 shows a map of the road surface friction coefficient correction gain Gμ using the road surface friction coefficient μ as a parameter.
When the road surface friction coefficient decreases, the reaction force generated in the tire decreases and the steering torque decreases. Therefore, basically, the road surface friction coefficient correction gain Gμ is set to 1 when the road surface friction coefficient is 1. (FIG. 9: a), the hysteresis correction amount ΔT (n) is also reduced (FIG. 9: b).
The correction gain map can be reflected in the hysteresis correction amount ΔT (n) by multiplying each.
G (φ, v, μ) = Gφ ・ Gv ・ Gμ

[Application Example of Steering Torque Correction in Example 1]
An application example of the steering torque correction in the first embodiment will be shown below. The following application examples each show an application of the steering torque correction value map corresponding to the steering angular speed of FIG.
FIG. 10 is a time series response of two steering angle waveforms (≈input torque waveform) and output torque waveforms having different steering angular velocities.
As described above, in the input torque waveforms having different steering angular velocities, the output torque from the sensor is not generated up to the points up to the respective hysteresis (FIG. 10: a, b).
Up to this point, no steering reaction torque is generated. Therefore, the steering reaction force is corrected by correcting this interval.
Here, correction is performed using a steering torque correction value map that changes in accordance with the steering angular speed, and the hysteresis correction amount ΔT (n) from the start of steering to the point at which the sensor value begins to be output is described by the following equation: it can.
ΔT (n) = ΔT (n-1) + ΔTo · Δt (4)
Therefore, the formula of the steering torque estimation value T? Trq including the hysteresis correction amount ΔT (n) is expressed by the following formula as described above.
T? Trq = Tsensor + ΔT (n) (5)
In addition, after the point at which the sensor value starts to be output, the process proceeds to the following formula in which the hysteresis value To is added to the turning torque detection value Tsensor based on the sensor value.
T? Trq = Tsensor + To (6)
That is, in the cutting start region, the sensor value that does not appear is corrected, and after the point at which the sensor value from the steering torque sensor 7 starts to be output, it is output in the form of adding the amount of steady deviation (= hysteresis value To).

[Turning torque correction processing]
FIG. 11 is a flowchart showing a turning torque correction process executed by the controller & drive circuit 11 of the first embodiment, and each step will be described below.

  In step S <b> 1, it is determined whether a constant steering angle is maintained including neutrality after the logic starts, or whether steering is performed to change the steering angle. If the vehicle is steered, the process proceeds to step S2. If the constant steering angle is maintained, the hysteresis correction amount ΔT (n) is not updated and the process proceeds to return.

  In step S2, following the determination that the steering is in step S1, it is determined whether or not the steering direction is reversed. If YES, the process proceeds to step S3, and if NO, the process proceeds to step S4. Here, the reversal of the steering direction is determined by the sign sgn of the steering angular speed. The initial value of sgn is set to the same sign as the steering direction (for example, left +, right-).

  In step S3, following the steering direction reversal determination in step S2, the sign of sgn is reversed and set, and the process proceeds to step S4.

In step S4, following the absence of reversal of the steering direction in step S2 or the sign reversal in step S3, a hysteresis correction amount ΔT (n) is calculated (equation (1)), and the process proceeds to step S5 (reverse steering). Force correction unit).
Here, the hysteresis correction amount ΔT (n) is calculated using the maps shown in FIGS. 6, 7, 8, and 9. In the case of inversion, since the value of the opposite sign is added from the previous time, the absolute value of the hysteresis correction amount ΔT (n) is updated in a smaller direction, and the hysteresis correction amount ΔT (n ).

  In step S5, following the calculation of the hysteresis correction amount ΔT (n) in step S4, it is determined whether or not the absolute value of the hysteresis correction amount ΔT (n) is smaller than the hysteresis value To of the steering torque sensor 7 that has been set. If YES, the process proceeds to step S6, and if NO, the process proceeds to step S7 (steady deviation determination means).

  In step S6, following the determination of | ΔT (n) | <To in step S5, a hysteresis correction amount ΔT (n) is added to the turning torque detection value Tsensor based on the sensor value from the turning torque sensor 7. The steered torque estimated value T? Trq is set (formula (2)), and the process proceeds to return.

  In step S7, following the determination of | ΔT (n) | ≧ To in step S5, the steering torque is estimated by adding the hysteresis value To to the turning torque detection value Tsensor based on the sensor value from the turning torque sensor 7. The value is set to T? Trq (formula (3)), and the process proceeds to return.

  A steering reaction force torque command is generated (steering reaction force setting means) based on the steering torque estimated value T? Trq calculated in step S6 or step S7, and the steering reaction force actuator 3 is driven.

[Turning torque correction]
For example, in the region where the steering operation is started from the neutral position of the rudder angle and the absolute value of the hysteresis correction amount ΔT (n) is smaller than the hysteresis value To of the turning torque sensor 7 set, the steps in the flowchart of FIG. The process proceeds from S1, step S2, step S4, step S5, and step S6. In step S6, the steering torque is estimated by adding the hysteresis correction amount ΔT (n) to the steering torque detection value Tsensor by the steering torque sensor 7. The value is T? Trq. In this region, since there is no output of the turning torque detection value Tsensor, the hysteresis correction amount ΔT (n) is directly used as the turning torque estimated value T? Trq.

  When the absolute value of the hysteresis correction amount ΔT (n) is greater than or equal to the hysteresis value To of the turning torque sensor 7 that has been set, in the flowchart of FIG. 11, step S1, step S2, step S4, step S5, step S7. In step S7, the hysteresis value To is added to the steering torque detection value Tsensor detected by the steering torque sensor 7 to obtain the steering torque estimated value T? Trq.

  As described above, in the steer-by-wire system in which the steering reaction force is applied according to the sensor value from the steering torque sensor 7, the steering reaction force is corrected according to the hysteresis of the steering torque sensor 7. Therefore, the input / output characteristics (FIG. 2) of the steering torque sensor 7 are corrected, a desired steering reaction torque can be generated, and the driver's steering feeling can be improved.

  Further, when the steering angle changes from neutral, the steering reaction force is corrected in accordance with the hysteresis of the turning torque sensor 7, so that the lightness of the steering reaction force near the neutral caused by the hysteresis of the turning torque sensor 7 is improved. This improves the steering feeling.

  Furthermore, the time until the actual output of the turning torque sensor 7 depends on the steering angular speed in order to take into account the characteristics corresponding to the steering angular speed, such as increasing the hysteresis correction amount ΔT (n) as the steering angular speed increases. Accordingly, appropriate correction can be made in response to changes in the steering angle, leading to an improvement in steering feeling.

  In addition, the steering torque is estimated based on the steering angle, the vehicle speed, and the road surface friction coefficient, and the hysteresis correction amount ΔT (n) is corrected to be higher as the estimated value of the steering torque near the neutral is larger. The amount not generated by the hysteresis characteristic can be appropriately corrected, and a desirable steering reaction force characteristic can be generated.

Next, the effect will be described.
In the steering control device of the first embodiment, the effects listed below can be obtained.

  (1) A steering unit that is mechanically separated from the steering unit and steers steered wheels according to steering, a steering torque sensor 7 that detects a steering torque of the steering unit, and the steering In a steering control device, comprising: a steering reaction force setting unit that sets a steering reaction force according to torque; and a steering reaction force actuator 3 that applies a steering reaction force of the steering unit based on the steering reaction force setting value. The turning torque sensor 7 has a predetermined hysteresis between the turning torque detection value and the actual turning torque, and the steering reaction force setting means sets the turning torque detection value Tsensor to the hysteresis. Since the steering reaction force correction unit (step S4) that corrects according to the occurrence state of the steering torque sensor 7 is corrected, a desired steering reaction force is set by correcting the hysteresis characteristic of the turning torque sensor 7, and the steering fee by the driver is set. To improve the ring it can.

  (2) The steering reaction force correction unit calculates the hysteresis correction amount ΔT (n) according to the state of occurrence of the hysteresis when the steering angle changes from the neutral position. It is possible to improve the lightness of the steering reaction force in the vicinity of the rudder angle neutrality caused by.

  (3) A steering torque estimating means for estimating an actual steering torque is provided, and the steering reaction force correction unit sets the steering steering force to the hysteresis correction amount ΔT (n−1) calculated in the previous calculation cycle. Since the amount of change in hysteresis correction amount ΔT (n) corresponding to the estimated torque value is added to obtain the hysteresis correction amount ΔT (n) in the current calculation cycle, the amount not generated by the hysteresis can be corrected appropriately, and the desired steering reaction can be corrected. Force characteristics can be generated.

  (4) As the steering torque estimating means, there is provided a steering angular speed detecting means for detecting a change speed of a steering angle equivalent value of a steering system from the steering section to a set position of the steering torque sensor 7, and the steering reaction force The correction unit increases the amount of change in the hysteresis correction amount ΔT (n) as the detected steering angular velocity value increases, so that the time until the actual output of the turning torque sensor 7 changes depending on the steering angular velocity. Correspondingly, appropriate correction is possible, and an improvement in steering feeling can be achieved.

  (5) As the turning torque estimation means, a steering angle detection means for detecting a steering angle equivalent value of a steering system from the steering part to a set position of the turning torque sensor 7 is provided, and the steering reaction force correction part is In order to increase the amount of change in the hysteresis correction amount ΔT (n) as the steering angle equivalent value increases, for example, when turning in a stopped state, the reaction force increases as the steering angle increases and the tire 13 is steered. On the other hand, a steering reaction force corresponding to this can be obtained.

  (6) A vehicle speed detecting means for detecting a vehicle speed is provided as the steered torque estimating means, and the steering reaction force correction unit changes a change in the hysteresis correction amount ΔT (n) according to the vehicle speed detection value. A steering reaction force reflecting the state of the vehicle speed can be obtained such that the steering reaction force is large in the stationary state and the steering reaction force increases as the vehicle travels at a high speed.

  (7) A road surface friction coefficient estimation unit that estimates a road surface friction coefficient is provided as the steering torque estimation unit, and the steering reaction force correction unit corrects the hysteresis as the road surface friction coefficient estimated value indicates a low road surface friction coefficient. In order to reduce the amount of change in the amount ΔT (n), for example, it is possible to obtain a steering reaction force reflecting a road surface friction coefficient state that a steering torque is small and a steering reaction force is small on a low road surface friction coefficient road.

  (8) There is provided a steady deviation determining means (step S5) for determining whether or not the hysteresis correction amount ΔT (n) between the steering torque detection value and the actual steering torque has reached the hysteresis value To, When it is determined that the hysteresis correction amount ΔT (n) is not equal to the hysteresis value To, the steering reaction force setting means adds the hysteresis correction amount ΔT (n) to the turning torque detection value Tsensor, thereby correcting the hysteresis correction. When it is determined that the amount ΔT (n) is equal to or greater than the hysteresis value To, the amount of hysteresis correction ΔT (n) generated is monitored in order to correct the steering torque detection value Tsensor by adding the hysteresis value To. Thus, it is possible to shift from the variable amount correction from the start of steering to the quantitative correction at an optimal timing.

  In the second embodiment, instead of the steering torque correction value ΔTo corresponding to the steering angular speed of the first embodiment, the turning torque correction time constant τo corresponding to the steering angular speed is used, and the detected steering torque detection value is output. In this example, the correction time is set in advance, and the shift from the variable amount correction from the start of steering to the quantitative correction is made. In addition, since the structure of Example 2 is the same as that of FIG. 1 of Example 1, illustration and description are abbreviate | omitted.

Next, the operation will be described.
In the second embodiment, the value of the steering torque correction time constant τo is changed according to the steering angular velocity (dφ / dt), and the hysteresis correction amount ΔT (n) is increased or decreased. ΔTo is equivalent. That is, in Example 2, the equation for obtaining the hysteresis correction amount ΔT (n) is expressed by the following equation.
ΔT (n) = ΔT (n−1) + sgn · {To / τo · G (φ, v, μ)} · Δt (1 ′)

FIG. 12 shows a map of the turning torque correction time constant τo using the absolute value of the steering angular velocity as a parameter.
As described above, when the steering angular velocity is small, the hysteresis correction amount ΔT (n) must be reduced, so that the value of the steering torque correction time constant τo increases. On the contrary, when the steering speed is high, the hysteresis correction amount ΔT (n) must be increased, so that the value of the turning torque correction time constant τo decreases.

FIG. 13 shows a map of the steering angle correction gain Gφ ′ using the steering angle as a parameter.
Here, the steering angle includes a steering wheel angle, a steering motor angle, a steering motor command angle, and the like corresponding to an angle at least on the steering wheel 12 side with respect to the torsion bar of the steering torque sensor 7.
Since the steering angle is set to 1 at a neutral steering angle (FIG. 11B), the gain is set to decrease as the steering angle increases (FIG. 11A), so the time constant decreases and the hysteresis correction amount ΔT (n) increases. . Further, the supplement at the change point can be arbitrarily performed. For example, also in FIG. 11, the complement by the curve (FIG. 11: c), the straight line (FIG. 11: e), and the function (FIG. 11: d) is shown.
Furthermore, change points (FIG. 11: f, g) can be moved to the left and right, respectively, and the position of the change point can be changed.

FIG. 14 shows a map of the vehicle speed correction gain Gv ′ using the vehicle speed as a parameter.
Since the turning torque correction time constant τo is set based on the medium speed range, the medium speed range gain is set to 1 and the vehicle speed becomes 0 [km / h] (stationary state). The gain decreases again as the vehicle speed increases and the vehicle travels at a high speed (FIG. 14: a to d). Therefore, the turning torque correction time constant τo decreases in the low speed range and the high speed range, and the hysteresis correction amount ΔT (n) increases, so that a correction value corresponding to the vehicle speed can be obtained.
There are at least two changing points, and linear interpolation is performed between the set vehicle speed correction gains. 14 shows a straight line, there are naturally a method of smoothing the connection between the change points and a method of complementing with a curve.

FIG. 15 shows a map of the road surface friction coefficient correction gain Gμ ′ using the road surface friction coefficient μ as a parameter.
When the road surface friction coefficient decreases, the reaction force generated in the tire decreases and the steering torque decreases. Therefore, basically, when the road surface friction coefficient is 1, the road surface friction coefficient correction gain Gμ ′ is set to 1. (FIG. 15: a), by setting the road surface friction coefficient correction gain Gμ ′ to be large, the turning torque correction time constant τo is increased, and the hysteresis correction amount ΔT (n) is decreased (FIG. 15: b).
The correction gain map can be reflected in the hysteresis correction amount ΔT (n) by multiplying each.
G (φ, v, μ) = Gφ '・ Gv' ・ Gμ '

[Turning torque correction processing]
FIG. 16 is a flowchart showing a turning torque correction process executed by the controller & drive circuit 11 of the second embodiment. Each step will be described below. Steps S21 to S23 are the same as steps S1 to S3 in FIG.

In step S24, following the absence of reversal of the steering direction in step S22 or the sign reversal in step S23, a hysteresis correction amount ΔT (n) is calculated (formula (1 ′)), and the process proceeds to step S25 (steering). Reaction force correction unit).
Here, the hysteresis correction amount ΔT (n) is calculated using the maps shown in FIGS. 12, 13, 14, and 15. In the case of inversion, since the value of the opposite sign is added from the previous time, the absolute value of the hysteresis correction amount ΔT (n) is updated in a smaller direction, and the hysteresis correction amount ΔT (n ).

In step S25, following the calculation of the hysteresis correction amount ΔT (n) in step S24, it is determined whether or not the elapsed time t from the start of steering or steering reversal has reached the set correction time. If YES, the process proceeds to step S29. If NO, the process proceeds to step S30 (correction time determination means).
Here, the correction time is set to the time until the turning torque is detected by the steering angular speed at the start of steering or at the time of steering reversal (at the time of turning back).

  In step S29, following the determination of t <correction time in step S25, the elapsed time t is set to t = t + Δt, and the process proceeds to step S26.

  In step S26, following the t = t + Δt set in step S29, a hysteresis correction amount ΔT (n) is added to the turning torque detection value Tsensor by the turning torque sensor 7 to obtain a turning torque estimated value T? Trq ( (Equation (2)), move to return.

  In step S30, following the determination of t ≧ correction time in step S25, the elapsed time t is reset to zero, and the process proceeds to step S27.

  In step S27, following the reset of the elapsed time t in step S30, the hysteresis value To is added to the turning torque detection value Tsensor detected by the turning torque sensor 7 to obtain a turning torque estimated value T? Trq (formula (3 )), Move to return.

  In step S28, following the determination that the steering angle is constant in step S21, the elapsed time t is reset to zero, and the process proceeds to return.

  A steering reaction force torque command is generated (steering reaction force setting means) based on the steering torque estimated value T? Trq calculated in step S26 or step S27, and the steering reaction force actuator 3 is driven.

[Turning torque correction]
For example, when the steering operation is started from the neutral position of the rudder angle and the elapsed time t from the start has not reached the set correction time, in the flowchart of FIG. 16, step S21 → step S22 → step S24 → step S25 → Proceeding from step S29 to step S26, in step S26, the steering torque estimated value T? Trq is obtained by adding the hysteresis correction amount ΔT (n) to the steering torque detection value Tsensor by the steering torque sensor 7. In this region, since there is no output of the turning torque detection value Tsensor, the hysteresis correction amount ΔT (n) is directly used as the turning torque estimated value T? Trq.

  Then, when the elapsed time t from the start of steering reaches the set correction time, in the flowchart of FIG. 16, the process proceeds from step S21 → step S22 → step S24 → step S25 → step S30 → step S27. A hysteresis value To is added to the detected steering torque value Tsensor by the steering torque sensor 7 to obtain the estimated steering torque value T? Trq. Since other operations are the same as those in the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the steering control device of the second embodiment, in addition to the effects (1) to (7) of the first embodiment, the following effects can be obtained.

(9) Correction time determination means for setting a correction time until the steering torque detection value is output and determining whether or not an elapsed time t from the start of steering or the start of steering reversal has reached the correction time ( Step S25) is provided, and when the steering reaction force setting means determines that the elapsed time t from the start of steering or the start of steering reversal has not reached the correction time, a hysteresis correction amount is added to the turning torque detection value Tsensor. When ΔT (n) is added and it is determined that the elapsed time t from the start of steering or the start of steering reversal has reached the correction time, the steering torque detection value Tsensor is corrected by adding a hysteresis value To. Further, by monitoring the elapsed time t from the start of the steering reversal, it is possible to shift from the variable amount correction to the quantitative correction from the start of the steering at an optimal timing.
Note that this correction time can be substituted by a count value from the start of cutting or when it is inverted.

  The third embodiment is an example in which the hysteresis correction amount ΔT (n) is gradually decreased and used for the steering reaction force control when the torque sensor output value appears from the turning torque sensor 7 as compared with the first and second embodiments. It is. In addition, since the structure of Example 2 is the same as that of FIG. 1 of Example 1, illustration and description are abbreviate | omitted.

Next, the operation will be described.
In Embodiment 3, the correction is made by adjusting the hysteresis correction amount ΔT (n) of the equation (2) as it is without shifting to the above equation (3), and the estimated turning torque T? Trq is
T? Trq = Tsensor + ΔT (n) × G _T (2 ')
It is calculated by the following formula. Here, G _T is a sensor value correction gain, as shown in FIG. 19, gradually according to the torque sensor output Tsensor (= steering torque detection value) is set to 1 when the zero torque sensor output Tsensor increases Is given as a smaller value.
Therefore, as shown in FIGS. 17 and 18, in the region where there is no torque sensor output Tsensor due to the occurrence of hysteresis, the steering torque is corrected by the hysteresis correction amount ΔT (n) as in the first and second embodiments. In the region where the torque sensor output Tsensor appears, the hysteresis correction amount ΔT (n) is gradually weakened.

[Turning torque correction processing]
FIG. 20 is a flowchart showing a turning torque correction process executed by the controller & drive circuit 11 of the third embodiment, and each step will be described below. Steps S31 to S33 are the same as steps S1 to S3 in FIG.

  In step S34, following the absence of reversal of the steering direction in step S32 or the sign reversal in step S33, a hysteresis correction amount ΔT (n) is calculated (expression (1) or expression (1 ′)), and step S35. (Steering reaction force correction unit).

At step S36, subsequent to the hysteresis correction quantity [Delta] T (n) calculated at the step S34, the turning torque detection value Tsensor by turning torque sensor 7, by multiplying the hysteresis correction quantity [Delta] T (n) and the sensor value correction gain G _T The value is added to obtain a steered torque estimated value T? Trq (formula (2 ')), and the process proceeds to return.

  Then, based on the estimated steering torque T? Trq calculated in step S36, a steering reaction force torque command is generated (steering reaction force setting means), and the steering reaction force actuator 3 is driven.

[Turning torque correction]
When steering or steering reversal is started, in the flowchart of FIG. 20, the process proceeds from step S31 → step S32 → (step S33 →) step S34 → step S36. In step S36, the detected steering torque value Tsensor by the steering torque sensor 7 is reached. to be a hysteresis correction quantity [Delta] T (n) and the sensor value correction gain G _T a by adding the multiplied value steered torque estimate T? trq. Since other operations are the same as those in the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the steering control device of the third embodiment, in addition to the effects (1) to (7) of the first embodiment, the following effects can be obtained.

(10) The steering reaction force correction unit adds a hysteresis correction amount ΔT (n) to the turning torque detection value Tsensor until the turning torque detection value comes out from the start of steering or steering reversal. When the torque detection value Tsensor begins to appear, the hysteresis correction amount ΔT (n) is gradually weakened, so that it is a simple process that does not perform correction switching determination as in the first and second embodiments, and the operation. It is possible to correct the hysteresis characteristic of the turning torque sensor 7 without giving the person a feeling of strangeness in the steering reaction force.

  As mentioned above, although the steering control apparatus of this invention has been demonstrated based on Example 1-Example 3, it is not restricted to these Examples 1-Example 3 about a concrete structure, Claim of Claims Design changes and additions are allowed without departing from the spirit of the invention according to each claim.

  The first embodiment shows an example in which the amount of hysteresis correction amount ΔT (n) generated is monitored to shift from the variable amount correction to the quantitative correction from the start of steering. In the second embodiment, the start of steering or steering reversal is shown. The example of shifting from the variable amount correction from the start of steering to the quantitative correction is shown by monitoring the elapsed time t from the start. For example, when the torque sensor value from the steering torque sensor 7 is output, or After the steering reversal, when the torque sensor value from the steering torque sensor 7 changes, the variable amount correction may be shifted to the quantitative correction.

  In the first to third embodiments, the steering control device by the steer-by-wire system having the mechanical backup is shown. In short, the tire turning angle can be freely set for the steering wheel operation, and the tire state is steered. A steer-by-wire system that can be freely set as a steering reaction force on the wheel according to the intention of the designer can be applied.

1 is an overall schematic diagram showing a steer-by-wire system to which a steering control device of Embodiment 1 is applied. It is a figure which shows the hysteresis characteristic which a torque sensor has. It is a steering angle and steering torque characteristic figure showing the solution subject 1 in this invention. It is a figure which shows the input torque waveform and steering torque waveform in case the steering speeds which represent the solution subject 2 in this invention differ. It is a figure which shows the steering torque correction | amendment outline | summary in Example 1. FIG. It is a figure which shows the steering torque correction value map with respect to the absolute value of the steering angular velocity used when determining the hysteresis correction amount in Example 1. FIG. It is a figure which shows the steering angle correction gain map with respect to the steering angle used when determining the hysteresis correction amount in Example 1. FIG. It is a figure which shows the vehicle speed correction gain map with respect to the vehicle speed used when determining a hysteresis correction amount in Example 1. FIG. It is a figure which shows the road surface friction coefficient correction gain map with respect to the road surface friction coefficient used when determining a hysteresis correction amount in Example 1. FIG. It is a figure which shows the input torque waveform at the time of applying the hysteresis correction of Example 1 in the situation where steering speed differs, and an output torque waveform. 3 is a flowchart illustrating a turning torque correction process executed by the controller and drive circuit according to the first embodiment. It is a figure which shows the turning torque correction time constant map with respect to the absolute value of the steering angular velocity used when determining the hysteresis correction amount in Example 2. FIG. It is a figure which shows the steering angle correction gain map with respect to the steering angle used when determining the hysteresis correction amount in Example 2. FIG. It is a figure which shows the vehicle speed correction gain map with respect to the vehicle speed used when determining a hysteresis correction amount in Example 2. FIG. It is a figure which shows the road surface friction coefficient correction gain map with respect to the road surface friction coefficient used when determining a hysteresis correction amount in Example 2. FIG. It is a flowchart which shows the steering torque correction process performed in the controller & drive circuit of Example 2. FIG. It is a figure which shows the input torque waveform at the time of applying the hysteresis correction of Example 3 in the situation where steering speed differs, and an output torque waveform. It is a steering angle and steering torque characteristic figure at the time of applying the hysteresis correction of Example 3. It is a figure which shows the sensor value correction | amendment gain map with respect to the torque sensor output used when determining the hysteresis correction amount in Example 3. FIG. 10 is a flowchart illustrating a turning torque correction process executed by a controller and drive circuit according to a third embodiment.

Explanation of symbols

1 Handle angle sensor (steering angle detection means)
2 Steering torque sensor 3 Steering reaction force actuator (steering reaction force applying means)
4 Steering reaction force motor angle sensor 5 Steering actuator 6 Steering actuator angle sensor 7 Steering torque sensor (steering torque detection means)
8 Pinion angle sensor 9 Tie rod axial force sensor 10 Mechanical backup 11 Controller & drive circuit 12 Steering wheel 13 Tire 14 Vehicle condition parameters (vehicle speed detection means, road surface friction coefficient estimation means)

Claims (9)

A steering unit that is mechanically separated from the steering unit and steers the steered wheels according to steering;
Steering torque detection means for detecting the steering torque of the steering unit;
Steering reaction force setting means for setting a steering reaction force according to the steering torque;
Steering reaction force applying means for applying a steering reaction force of the steering unit based on the steering reaction force setting value;
In a steering control device with
A steering torque estimation means for estimating the actual steering torque is provided,
The turning torque detection means has a predetermined steady deviation between the turning torque detection value and the actual turning torque,
The steering reaction force setting means, the steering torque detection value, have a steering reaction force correction unit for correcting in accordance with the occurrence of the predetermined steady-state error,
The steering reaction force correction unit calculates a steady-state deviation correction amount calculated in a previous calculation cycle based on the steady-state deviation correction amount according to the state of occurrence of the predetermined steady-state deviation when the steering angle is in a region where the steering angle changes from a neutral position. And a steering control device that calculates based on the estimated steering torque . In the steering control device according to claim 1,
The steering reaction force correction unit adds a change in the steady deviation correction amount according to the steered torque estimated value to the steady deviation correction amount calculated in the previous calculation cycle, thereby correcting the steady deviation in the current calculation cycle. A steering control device characterized in that it is a quantity. In the steering control device according to claim 2 ,
As the turning torque estimation means, there is provided a steering angular speed detection means for detecting a change speed of a steering angle equivalent value of a steering system from the steering section to a setting position of the steering torque detection means,
The steering control device, wherein the steering reaction force correction unit increases the change amount of the steady-state deviation correction amount as the steering angular velocity detection value increases. In the steering control device according to claim 2 or 3,
As the steering torque estimation means, a steering angle detection means for detecting a steering angle equivalent value of a steering system from the steering section to a setting position of the steering torque detection means is provided,
The steering control device, wherein the steering reaction force correction unit increases the change in the steady-state deviation correction amount as the steering angle equivalent value increases. The steering control device according to any one of claims 2 to 4,
As the steering torque estimating means, a vehicle speed detecting means for detecting a vehicle speed is provided,
The steering control device, wherein the steering reaction force correction unit changes a change amount of a steady deviation correction amount according to the vehicle speed detection value. The steering control device according to any one of claims 2 to 5,
As the turning torque estimating means, a road surface friction coefficient estimating means for estimating a road surface friction coefficient is provided,
The steering control device, wherein the steering reaction force correction unit decreases the change amount of the steady deviation correction amount as the estimated value of the road surface friction coefficient indicates a low road surface friction coefficient. The steering control device according to any one of claims 1 to 6,
Before Kijo normal deviation correction amount provided steady-state deviation determining means determines whether it is the predetermined steady-state error,
When it is determined that the steady deviation correction amount is not the predetermined steady deviation, the steering reaction force setting unit adds the steady deviation correction amount to the turning torque detection value, and the steady deviation correction amount is When it is determined that the deviation is equal to or greater than a predetermined steady-state deviation, the steering control device corrects the steering torque detection value by adding the predetermined steady-state deviation.

The steering control device according to any one of claims 1 to 6 ,
A correction time determining means for setting a correction time until the detected steering torque detection value is output and determining whether an elapsed time from the start of steering or the start of steering reversal has reached the correction time;
When it is determined that the elapsed time from the start of steering or the start of steering reversal has not reached the correction time, the steering reaction force setting means adds a steady deviation correction amount to the steering torque detection value to start steering or steering When it is determined that the elapsed time from the start of reversal has reached the correction time, the steering control device corrects the steering torque detection value by adding the predetermined steady-state deviation. The steering control device according to any one of claims 1 to 6 ,
The steering reaction force correction unit adds a steady deviation correction amount to the steered torque detection value until the steered torque detection value comes out from the start of steering or steering reversal, and when the steered torque detection value starts to appear. A steering control device characterized by gradually decreasing the steady-state deviation correction amount.

Images