Brake system with shift out of park support
A method for controlling brake pressure during a shift of a vehicle out of park may include determining that a first status condition is met when the vehicle is in park with an electric parking brake applied, determining that a second status condition is met when the vehicle is not moving, responsive to detecting a shift of the vehicle out of park when the first and second status conditions are both met, directing a build-up of brake pressure until a brake pressure target is reached, and holding the brake pressure at the brake pressure target until a release condition is met.
1. A method for controlling brake pressure during a shift of a vehicle out of park, the method comprising:
determining that a first status condition is met when the vehicle is in park with an electric parking brake applied;
determining that a second status condition is met when the vehicle is not moving;
responsive to detecting a shift of the vehicle out of park when the first and second status conditions are both met, directing a build-up of brake pressure until a brake pressure target is reached; and
holding the brake pressure at the brake pressure target until a release condition is met,
wherein the release condition comprises elapse of a predetermined period of time to enable handover to a hill start assist function.
2. The method of claim 1 , wherein the release condition comprises elapse of a predetermined period of time.
3. The method of claim 1 , wherein the release condition comprises receiving a driver input indicating a pressure release request.
4. A method for controlling brake pressure during a shift of a vehicle out of park, the method comprising:
determining that a first status condition is met when the vehicle is in park with an electric parking brake applied;
determining that a second status condition is met when the vehicle is not moving;
responsive to detecting a shift of the vehicle out of park when the first and second status conditions are both met, directing a build-up of brake pressure until a brake pressure target is reached; and
holding the brake pressure at the brake pressure target until a release condition is met,
wherein the brake pressure target is determined by:
determining a brake pressure requested by a driver of the vehicle based on a brake pedal input;
determining a hold pressure required to hold the vehicle based on a current vehicle state; and
obtaining a minimum brake pressure defined for wear prevention of the electric parking brake.
5. The method of claim 4 , wherein the release condition comprises an elapse of a predetermined period of time to enable handover to a hill start assist function.
6. The method of claim 4 , wherein the brake pressure target is a largest value among the brake pressure requested by the driver, the hold pressure and the minimum brake pressure defined for wear prevention.
7. The method of claim 4 , wherein the current vehicle state comprises an estimation of vehicle mass and a determination of an amount of slope of a surface on which the vehicle is parked.
8. The method of claim 7 , wherein the estimation of vehicle mass is determined based on vehicle weight and an estimation of vehicle load.
9. The method of claim 8 , wherein the hold pressure is determined from a table mapping the amount of slope and the estimation of vehicle mass to an estimated holding force.
10. The method of claim 4 , wherein the minimum brake pressure defined for wear prevention is a fixed value defined based on vehicle type.
11. A vehicle control system comprising:
a gear selector operably coupled to a transmission of the vehicle to shift the vehicle between various states including at least drive, reverse and park;
a braking torque module operably coupled to brake hardware of the vehicle to provide braking force or braking torque to the brake hardware based on a brake pedal position;
an electric park brake; and
a hold controller operably coupled to a sensor network of the vehicle to receive vehicle status information to:
determining that a first status condition is met when the vehicle is in park with the electric parking brake applied;
determining that a second status condition is met when the vehicle is not moving;
responsive to detecting a shift of the vehicle out of park when the first and second status conditions are both met, directing a build-up of brake pressure until a brake pressure target is reached; and
holding the brake pressure at the brake pressure target until a release condition is met,
wherein the release condition comprises an elapse of a predetermined period of time to enable handover to a hill start assist function.
12. The vehicle control system of claim 11 , wherein the release condition comprises receiving a driver input indicating a pressure release request.
13. A vehicle control system comprising:
a gear selector operably coupled to a transmission of the vehicle to shift the vehicle between various states including at least drive, reverse and park;
a braking torque module operably coupled to brake hardware of the vehicle to provide braking force or braking torque to the brake hardware based on a brake pedal position;
an electric park brake; and
a hold controller operably coupled to a sensor network of the vehicle to receive vehicle status information to:
determining that a first status condition is met when the vehicle is in park with the electric parking brake applied;
determining that a second status condition is met when the vehicle is not moving;
responsive to detecting a shift of the vehicle out of park when the first and second status conditions are both met, directing a build-up of brake pressure until a brake pressure target is reached; and
holding the brake pressure at the brake pressure target until a release condition is met,
wherein the brake pressure target is determined by:
determining a brake pressure requested by a driver of the vehicle based on a brake pedal input;
determining a hold pressure required to hold the vehicle based on a current vehicle state; and
obtaining a minimum brake pressure defined for wear prevention of the electric parking brake.
14. The vehicle control system of claim 13 , wherein the release condition comprises elapse of a predetermined period of time.
15. The vehicle control system of claim 14 , wherein the predetermined period of time is selected as a delay period to enable handover to a hill start assist function.
16. The vehicle control system of claim 13 , wherein the brake pressure target is a largest value among the brake pressure requested by the driver, the hold pressure and the minimum brake pressure defined for wear prevention.
17. The vehicle control system of claim 13 , wherein the current vehicle state comprises an estimation of vehicle mass and a determination of an amount of slope of a surface on which the vehicle is parked.
18. The vehicle control system of claim 17 , wherein the estimation of vehicle mass is determined based on vehicle weight and an estimation of vehicle load.
19. The vehicle control system of claim 18 , wherein the hold pressure is determined from a table mapping the amount of slope and the estimation of vehicle mass to an estimated holding force.
20. The vehicle control system of claim 13 , wherein the minimum brake pressure defined for wear prevention is a fixed value defined based on vehicle type.