Method and system for collecting regenerative braking energy in a parallel hybrid electric vehicle

A method of controlling regenerative braking energy in a vehicle having an engine and a motor, the method comprising:

• transitioning the vehicle from a non-regenerative braking state to a first regenerative braking state when a vehicle system controller requests a regenerative braking state and the engine is connected to the motor;
• transitioning the vehicle from a non-regenerative braking state to a second regenerative braking state when the vehicle system controller requests a regenerative braking state and the engine is disconnected from the motor;
• determining whether to transition the vehicle from the first regenerative braking state to the second regenerative braking state after the vehicle is transitioned to the first regenerative braking state from a non-regenerative braking state;
• disconnecting the engine from the motor when a determination is made to transition the vehicle from the first regenerative braking state to the second regenerative braking state;
• and
• increasing braking torque from the motor when the engine is being disconnected from the motor during a transition from the first regenerative braking state to the second regenerative braking state, the increase in braking torque being based on a braking torque reduction from the engine.

A method of controlling regenerative braking energy in a vehicle having an engine and a motor, the engine being connected to the motor with a disconnect clutch, the method comprising:

• transitioning the vehicle from a non-regenerative braking state to a first regenerative braking state when a vehicle system controller requests a regenerative braking state and the disconnect clutch is closed;
• transitioning the vehicle from a non-regenerative braking state to a second regenerative braking state when the vehicle system controller requests a regenerative braking state and the disconnect clutch is open;
• determining whether to transition the vehicle from the first regenerative braking state to the second regenerative braking state after the vehicle is transitioned to the first regenerative braking state from a non-regenerative braking state;
• opening the disconnect clutch when a determination is made to transition the vehicle from the first regenerative braking state to the second regenerative braking state;
• and
• increasing braking torque from the motor when the disconnect clutch is being opened during a transition from the first regenerative braking state to the second regenerative braking state, the increase in braking torque being based on a braking torque reduction from the engine.