Vehicle control method and vehicle control apparatus

1. A control method for controlling a vehicle which includes a control force generating apparatus configured to generate control force in a vertical direction for damping vibration of a sprung portion of the vehicle, the control force being applied between at least one wheel and a portion of a body of the vehicle, which portion corresponds to a position of the wheel, and a control unit for controlling the control force generating apparatus,

the control method comprising:

a step in which the control unit computes a predicted route that the wheel is predicted to pass;

a step in which the control unit obtains first data from road surface information which is data in which a relationship is established between position information representing a position on a road surface and a road surface displacement related value which relates to a vertical displacement of the road surface at the position represented by the position information, the first data representing a time series change of the road surface displacement related value on the predicted route;

a step in which the control unit obtains, from the first data, the road surface displacement related value at a predicted passage position that the wheel is predicted to pass when a predetermined time elapses from a present point in time;

a step in which the control unit computes a target control force by using the road surface displacement related value at the predicted passage position; and

a step in which the control unit executes preview vibration damping control for controlling the control force generating apparatus in such a manner that the control force becomes equal to the target control force when the wheel passes the predicted passage position,

wherein the control method further comprising:

a step in which the control unit determines whether or not a predetermined condition is satisfied on a basis of the first data, the predetermined condition being satisfied when the time series change of the road surface displacement related value on the predicted route falls within a controllable range of the control force generating apparatus; and

a step in which the control unit executes a particular process for reducing a magnitude of the road surface displacement related value at the predicted passage position when the predetermined condition is not satisfied.

2. A control method according to claim 1 , wherein the step of executing the particular process includes executing a high-pass filter process on the first data.

3. A control method according to claim 1 , wherein the step of computing the target control force includes computing the target control force by using the road surface displacement related value at the predicted passage position and a gain for the road surface displacement related value at the predicted passage position; and

the step of executing the particular process includes reducing the gain in a case where the predetermined condition is not satisfied, so that the gain becomes smaller as compared with a case where the predetermined condition is satisfied.

4. A control method according to claim 1 , wherein the step of executing the particular process includes:

computing an index value which represents a degree of deviation of the road surface displacement related value in the first data from the controllable range, and

executing a process of reducing the magnitude of the road surface displacement related value at the predicted passage position to a degree that increases with the index value.

5. A control method according to claim 1 , wherein the step of determining whether or not the predetermined condition is satisfied includes:

determining that the predetermined condition is satisfied when a maximum value of the magnitude of the road surface displacement related value in the first data is equal to or less than a threshold set on a basis of the controllable range of the control force generating apparatus, and

determining that the predetermined condition is not satisfied when the maximum value is greater than the threshold.

6. A control method according to claim 5 ,

wherein the control force generating apparatus includes an active stabilizer apparatus, and the wheel includes a first wheel on a left side of the vehicle and a second wheel on a right side of the vehicle, and

wherein the step of determining whether or not the predetermined condition is satisfied includes:

setting the threshold to a first value in the case where a first waveform represented by the first data for the first wheel and a second waveform represented by the first data for the second wheel are in phase relative to each other, and

setting the threshold to a second value greater than the first value in the case where the first waveform and the second waveform are in anti-phase relative to each other.

7. A control method according to claim 1 , wherein the road surface displacement related value includes at least one of road surface displacement representing displacement of the road surface in the vertical direction, road surface displacement speed representing a derivative value of the road surface displacement with respect to time, unsprung displacement representing displacement of an unsprung portion of the vehicle in the vertical direction, and unsprung speed representing a derivative value of the unsprung displacement with respect to time.

8. A vehicle control apparatus comprising:

a control force generating apparatus configured to generate control force in a vertical direction for damping vibration of a sprung portion of a vehicle, the control force being applied between at least one wheel and a portion of a body of the vehicle, which portion corresponds to a position of the wheel; and

a control unit for controlling the control force generating apparatus,

the control unit being configured

to determine a predicted route that the wheel is predicted to pass,

to obtain first data from road surface information which is data in which a relationship is established between position information representing a position on a road surface and a road surface displacement related value which relates to a vertical displacement of the road surface at the position represented by the position information, the first data representing a time series change of the road surface displacement related value on the predicted route,

to obtain, from the first data, the road surface displacement related value at a predicted passage position that the wheel is predicted to pass when a predetermined time elapses from a present point in time,

to compute a target control force by using the road surface displacement related value at the predicted passage position, and

to execute preview vibration damping control for controlling the control force generating apparatus in such a manner that the control force becomes equal to the target control force when the wheel passes the predicted passage position,

wherein the control unit is further configured

to determine whether or not a predetermined condition is satisfied on a basis of the first data, the predetermined condition being satisfied when the time series change of the road surface displacement related value on the predicted route falls within a controllable range of the control force generating apparatus, and

to execute a particular process for reducing the road surface displacement related value at the predicted passage position when the predetermined condition is not satisfied.