Hill hold decay

A hill hold decay (HDD) system of a vehicle, the system comprising:

• a longitudinal acceleration sensor configured to detect the longitudinal acceleration of the vehicle;
• a wheel speed sensor configured to detect the speed of the vehicle;
• a brake pedal detector configured to detect a pressure applied to a brake pedal;
• a gas pedal detector configured to detect a pressure applied to a gas pedal;
• a gear sensor configured to sense a gear the vehicle is in;
• and
• a controller configured to receive an indication of the longitudinal acceleration of the vehicle from the longitudinal acceleration sensor, an indication of the speed of the vehicle from the wheel speed sensor, an indication of the pressure on the brake pedal from the brake pedal detector, an indication of the pressure on the gas pedal from the gas pedal sensor, and an indication of the gear the vehicle is in from the gear sensor, the controller further configured to
• determine the vehicle has come to a standstill;
• after determining the vehicle has come to a standstill
• determine a slope of the ground the vehicle is on;
• determine a direction of travel of the vehicle is downhill;
• detect a release of the brake pedal;
• release a brake force applied to a plurality of wheels of the vehicle at a constant first rate;
• determine a speed of the vehicle has reached a minimum threshold;
• after determining the speed of the vehicle has reached the minimum threshold
• release the brake force at a second rate as long as the speed of the vehicle is increasing;
• determine the speed of the vehicle has reached a maximum threshold;
• and
• after determining the speed of the vehicle has reached the maximum threshold, release the brake force.