System and method to control regenerative braking

A braking system, comprising:

• a first wheel;
• a first friction brake coupled to the first wheel;
• a second wheel;
• a second friction brake coupled to the second wheel;
• an electric motor coupled to the first wheel;
• an electronic control unit electronically coupled to the electric motor;
• a first user-operated brake input device coupled to the first friction brake;
• a first sensor coupled to the first user-operated brake input device and electronically coupled to the electronic control unit;
• a second user-operated brake input device coupled to the second friction brake;
• and
• a second sensor coupled to the second user-operated brake input device and electronically coupled to the electronic control unit, wherein the electronic control unit commands the electric motor to operate as a generator when at least one of the first and second user-operated brake input devices is actuated;
• a hydraulic pressure sensor for use in conjunction with at least one of the first sensor and the second sensor, wherein the hydraulic pressure sensor, based on an amount of hydraulic pressure in a hydraulic line of at least one of the first friction brake and the second friction brake, being indicative of a desire for a braking torque;
• wherein the first sensor is a switch indicating whether the first brake input device is actuated and the electronic control unit commands the motor to generate electricity up to a first fraction of a maximum regeneration capacity of the motor when the first brake input device is actuated and the second brake input device is unactuated;
• wherein the second sensor is a switch indicating whether the second brake input device is actuated and the electronic control unit commands the motor to generate electricity up to a second fraction of the maximum regeneration capacity of the motor when the second brake input device is actuated and the first brake input device is unactuated;
• wherein the electronic control unit commands the motor to generate electricity at a third fraction of the maximum regeneration capacity of the motor when both the first and second brake input devices are actuated, the third fraction is greater than the first fraction, and the third fraction is greater than the second fraction;
• wherein a total braking torque is determined as a sum of a friction braking torque and a regenerative braking torque, the friction braking torque is generated by at least one of following:
• the first friction brake and the second friction brake, the regenerative braking torque is determined by a maximum available regenerative braking torque limited by at least one of the following:
• the first fraction, the second fraction, and the third fraction of the maximum regeneration capacity of the motor, wherein upon attaining the maximum available regenerative braking torque, at least one of the first friction brake and the second friction brake is actuated, wherein the braking torque increases monotonically until a maximum possible regenerative braking torque.

A method to brake an electric vehicle based on a vehicle operator's input, the electric vehicle having an electric generator coupled to a first wheel of the electric vehicle, the method comprising:

• determining actuation of a first brake lever based on a first sensor coupled to the first brake lever, the first brake lever being coupled to a brake provided on the first wheel;
• determining actuation of a second brake lever based on a second sensor coupled to the second brake lever, the second brake lever being coupled to a brake provided on a second wheel of the vehicle;
• wherein a hydraulic pressure sensor for use in conjunction with at least one of the first sensor and the second sensor, wherein the hydraulic pressure sensor, based on an amount of hydraulic pressure in a hydraulic line of at least one of the first friction brake and the second friction brake, being indicative of a desire for a braking torque;
• commanding the generator to generate electricity based on at least one of actuation of the first brake lever and actuation of the second brake lever;
• commanding the generator to generate electricity up to a first fraction of a maximum regeneration capacity of the generator when the first brake lever is actuated and the second brake lever is unactuated;
• commanding the generator to generate electricity up to a second fraction of the maximum regeneration capacity of the generator when the second brake lever is actuated and the first brake lever is unactuated;
• and
• commanding the generator to generate electricity at a third fraction of the maximum regeneration capacity of the generator when both the first and second brake levers are actuated, wherein the third fraction is greater than the first fraction, and the third fraction is greater than the second fraction;
• wherein a total braking torque is determined as a sum of a friction braking torque and a regenerative braking torque, the friction braking torque is generated by at least one of following:
• the first friction brake and the second friction brake, the regenerative braking torque is determined by a maximum available regenerative braking torque limited by at least one of the following:
• the first fraction, the second fraction, and the third fraction of the maximum regeneration capacity of the motor, wherein upon attaining the maximum available regenerative braking torque, at least one of the first friction brake and the second friction brake is actuated, wherein the braking torque increases monotonically until a maximum possible regenerative braking torque.