Regenerative brake control system of electric vehicle

1. A regenerative brake control system comprising:

an electric motor;

a detecting device for detecting a vehicle state; and

a control unit configured to set a regenerative torque of the electric motor;

wherein the control unit is configured to set a target regenerative torque based on the vehicle state detected by the detecting device when a predetermined regeneration condition is satisfied,

wherein when a predetermined asymptotic control condition is satisfied, the control unit is configured to perform an asymptotic control process in which a regenerative torque command provided to the electric motor approaches the target regenerative torque over time, and

wherein when the predetermined asymptotic control condition is not satisfied, the control unit is configured to immediately provide the target regenerative torque as the regenerative torque command to the electric motor;

wherein the target regenerative torque is a negative torque value, and

wherein the control unit is configured to:

calculate an asymptotic control amount in the asymptotic control process, the asymptotic control amount being a positive torque value that is smaller than an output torque of the electric motor just before the regeneration condition is met,

decrease the positive torque value of the asymptotic control amount over time, and

calculate the regenerative torque command by adding the asymptotic control amount to the target regenerative torque.

2. The regenerative brake control system according to claim 1 ,

wherein the predetermined asymptotic control condition is when a difference between a value of torque output from the electric motor and a value of the target regenerative torque is larger than a predetermined value, and

wherein the control unit is configured to provide a target regenerative torque command immediately when the difference between the value of the torque output from the electric motor and the value of the target regenerative torque is smaller than the predetermined value.

3. The regenerative brake control system according to claim 1 , wherein the predetermined asymptotic control condition is when a driving speed or a motor rotational speed is equal to or higher than a specified speed which is higher than a predetermined regeneration initiation speed, and

wherein the control unit is configured to provide a target regenerative torque command immediately when the driving speed or the motor rotational speed is lower than the specified speed.

4. The regenerative brake control system according to claim 1 ,

wherein the predetermined asymptotic control condition is when a change in an operation amount of an acceleration operation member which occurs before the regeneration condition is satisfied is equal to or larger than a predetermined value, and

wherein the control unit is configured to provide a target regenerative torque command immediately when the change in the operation amount of the acceleration operation member which occurs before the regeneration condition is satisfied is smaller than the predetermined value.

5. The regenerative brake control system according to claim 1 , being configured to transmit a driving power generated in the electric motor via a transmission, the regenerative brake control system further comprising:

a transmission detecting device for detecting a change gear ratio of the transmission,

wherein the control unit is configured to set the asymptotic control amount based on the change gear ratio in the asymptotic control process.

6. The regenerative brake control system according to claim 1 ,

wherein the vehicle is a two-wheeled vehicle.

7. The regenerative brake control system according to claim 1 , being applied to a motorcycle in which a rear wheel is mounted to a swing arm.

8. The regenerative brake control system according to claim 1 , further comprising:

a first regeneration operation member which is operated to adjust the regenerative torque of the electric motor,

wherein the control unit is configured to adjust the regenerative torque in response to an adjustment command of the regenerative torque, corresponding to an operation of the first regeneration operation member.

9. The regenerative brake control system according to claim 8 , further comprising:

a second regeneration operation member which is operated to adjust the regenerative torque of the electric motor;

wherein the control unit is configured to change an adjustment amount of the regenerative torque, in response to a change command of a regenerative mode selected by an operation of the second regeneration member.

10. The regenerative brake control system according to claim 1 ,

wherein when the regeneration condition is satisfied, the control unit is configured to provide a command indicating zero torque to the electric motor and performs the asymptotic control process such that a regeneration amount is gradually increased from the command indicating zero torque.

11. The regenerative brake control system according to claim 1 ,

wherein when a rotational speed of the electric motor is equal to or lower than a predetermined value in a middle of the asymptotic control process, the control unit is configured to make the regenerative torque approach zero.

12. The regenerative brake control system according to claim 1 , being configured to transmit a driving power generated in the electric motor via a transmission, the regenerative brake control system further comprising:

a transmission detecting device for detecting a change gear ratio of the transmission,

wherein the control unit is configured to set the asymptotic control amount based on a driving speed of a vehicle, a rotational speed of the electric motor, and the change gear ratio in the asymptotic control process.

13. The regenerative brake control system according to claim 1 ,

wherein a slip amount between a wheel and a road surface is detected at the wheel side, and the asymptotic control amount is set based on the detected slip amount in the asymptotic control process.