Control method for electrically driven vehicle and control device for electrically driven vehicle

1. A control method for an electrically driven vehicle including a motor configured to supply the vehicle with a braking force or a driving force corresponding to an accelerator operation amount, the control method being for controlling the braking force when the accelerator operation amount is less than a predetermined value and controlling the driving force when the accelerator operation amount is the predetermined value or more, the control method comprising:

calculating a torque target value at which the motor is caused to output a braking torque or a driving torque corresponding to the accelerator operation amount;

estimating a disturbance torque acting on the motor as a resistance corresponding to a road surface gradient;

performing a correction to remove the disturbance torque from the torque target value;

controlling the motor in accordance with the torque target value subjected to the correction; and

reducing a correction amount in the correction on a downhill road only when the accelerator operation amount is less than the predetermined value and a vehicle speed is larger than a predetermined vehicle speed.

2. The control method for the electrically driven vehicle, according to claim 1 , wherein

the predetermined vehicle speed has a value an absolute value which is larger than zero.

3. The control method for the electrically driven vehicle, according to claim 1 , wherein,

on the downhill road, when the accelerator operation amount is less than the predetermined value and the vehicle speed is larger than the predetermined vehicle speed, a ratio to reduce the correction amount is decreased as the vehicle speed decreases.

4. The control method for the electrically driven vehicle, according to claim 1 , wherein:

a rotation speed of the motor or a speed parameter proportional to the rotation speed is detected; and

when the vehicle speed becomes a stop-control-start vehicle speed or less, the motor is controlled without reducing the correction amount so that a motor torque converges to the disturbance torque along with a decrease of the rotation speed of the motor or the speed parameter.

5. The control method for the electrically driven vehicle, according to claim 4 , wherein

that the vehicle speed is the stop-control-start vehicle speed or less indicates that the vehicle is just before a stop and the rotation speed of the motor or the speed parameter is smaller than a default value determined in advance.

6. A control device for an electrically driven vehicle, the control device being applied to the electrically driven vehicle including a motor configured to supply the vehicle with a braking force or a driving force corresponding to an accelerator operation amount, the control device being for controlling the braking force when the accelerator operation amount is less than a predetermined value and controlling the driving force when the accelerator operation amount is the predetermined value or more, the control device being configured to:

calculate a torque target value at which the motor is caused to output a braking torque or a driving torque corresponding to the accelerator operation amount;

estimate a disturbance torque acting on the motor as a resistance corresponding to a road surface gradient;

perform a correction to remove the disturbance torque from the torque target value;

control the motor in accordance with the torque target value subjected to the correction; and

reduce a correction amount in the correction on a downhill road only when the accelerator operation amount is less than the predetermined value and a vehicle speed is larger than a predetermined vehicle speed.