Integrated vehicle braking system
A vehicle control system for a vehicle having a braking system and active suspension system is provided. The vehicle control system may be configured to adjust a normal component of a wheel force at one or more wheels of the vehicle to increase an average traction force at the one or more wheels during a braking event. The vehicle control system may adjust a normal component of a wheel force at one or more wheels based on reference road information, forward-looking road information, and/or vehicle sensor data.
1 . A vehicle comprising:
a first wheel;
a second wheel;
a braking system configured to apply braking force to the first wheel and the second wheel;
an active suspension system operatively coupled to the first wheel and the second wheel, wherein the active suspension system is configured to apply active forces to the first wheel and the second wheel in at least one mode of operation to adjust a normal component of a first wheel contact force between the first wheel and a road surface and to adjust a normal component of a second wheel contact force between the second wheel and the road surface, wherein the first wheel is a front wheel of the vehicle, the second wheel is a rear wheel of the vehicle, and the first wheel and second wheel are positioned at opposite corners of the vehicle;
a forward-looking road information system configured to receive forward-looking road information; and
at least one processor configured to control the braking system and the active suspension system, wherein the at least one processor is configured to:
receive the forward-looking road information from the forward-looking road information system,
detect a road disturbance based on the forward-looking road information received from the forward-looking road information system, the road disturbance comprising a change in friction of the road surface relative to a nominal road friction,
control the braking system and the active suspension system based at least partially on the detected road disturbance, and
control the active suspension system to increase the normal component of the first wheel and the normal component of the second wheel based at least partially on the detected road disturbance, such that a twist force is applied to the vehicle during braking.
2 . The vehicle of claim 1 , wherein the forward-looking road information includes a turn.
3 . The vehicle of claim 1 , wherein the first wheel is a first front wheel of the vehicle, the second wheel is a second front wheel of the vehicle, and the at least one processor is configured to control the active suspension system to adjust a pitch of the vehicle.
4 . The vehicle of claim 3 , wherein the forward-looking road information includes a road disturbance, and wherein the at least one processor is configured to control the active suspension system to temporarily increase the normal component of the first wheel contact force and the normal component of the second wheel contact force based on the road disturbance.
5 . The vehicle of claim 3 , wherein the at least one processor is configured to determine a braking event is in progress, wherein the at least one processor is configured to determine a pitch frequency of the vehicle based on the braking event, and wherein the at least one processor is configured to control the active suspension system to adjust the pitch of the vehicle based on the determined pitch frequency.
6 . The vehicle of claim 1 , wherein the first wheel is a first side wheel of the vehicle, the second wheel is a second side wheel of the vehicle positioned on a same side of the vehicle, and the at least one processor is configured to control the active suspension system to adjust a roll of the vehicle.
7 . The vehicle of claim 6 , wherein the forward-looking road information includes a road disturbance, and wherein the at least one processor is configured to control the active suspension system to temporarily increase the normal component of the first wheel contact force and the normal component of the second wheel contact force based on the road disturbance.
8 . The vehicle of claim 1 , wherein the at least one processor is configured to:
determine a braking event is in progress;
determine an expected response of the vehicle during the braking event; and
control the braking system and the active suspension system based on the expected response.
9 . The vehicle of claim 1 , wherein the forward-looking road information includes a road disturbance having a disturbance size, wherein the at least one processor is configured to determine whether the disturbance size exceeds an activation threshold, wherein the at least one processor is configured to disable the active suspension system if the disturbance size does not exceed the activation threshold for a duration of a braking event.
10 . The vehicle of claim 1 , wherein the forward-looking road information system is a LIDAR.
11 . The vehicle of claim 1 , wherein the forward-looking road information system is at least one camera.
12 . The vehicle of claim 1 , wherein the forward-looking road information system comprises one or more forward-looking sensors and/or a system that receives information about a road ahead of the vehicle from a cloud service, server, or other vehicle.
13 . A method of controlling a vehicle including a braking system and an active suspension system, wherein the active suspension system is operatively coupled to a first wheel and a second wheel, wherein the first wheel is a front wheel of the vehicle and the second wheel is a rear wheel of the vehicle, and the first wheel and the second wheel are positioned at opposite corners of the vehicle, the method comprising:
receiving forward-looking road information with a forward-looking road information system;
determining a presence of a road disturbance based on the forward-looking road information, wherein a friction of the road disturbance is less than a nominal road friction;
controlling the braking system and the active suspension system based at least partially on the road disturbance, wherein controlling the active suspension system includes applying active forces to the first wheel and the second wheel to adjust a normal component of a first wheel contact force between the first wheel and a road surface and to adjust a normal component of a second wheel contact force between the second wheel and the road surface; and
during braking, controlling the active suspension system to apply a twist force to the vehicle by increasing the normal component of the first wheel contact force and the normal component of the second wheel contact force.
14 . The method of claim 13 , wherein the forward-looking road information system comprises one or more forward-looking sensors and/or a system that receives road information about a road ahead of the vehicle from a cloud service, server, or another vehicle.
15 . The method of claim 13 , wherein the forward-looking road information includes a turn.
16 . The method of claim 13 , further comprising determining that a braking force demand for a first wheel during a braking event exceeds a threshold braking force, and, upon determining that the braking force demand exceeds the threshold braking force, adjusting the normal component of a wheel force at the first and second wheels of the vehicle with the active suspension system to increase an average traction force at the first wheel during the braking event.
17 . The method of claim 13 , further comprising determining if a yaw metric exceeds a threshold and controlling the braking system and the active suspension system in order to reduce the yaw metric below the threshold.
18 . The method of claim 13 , further comprising determining an absolute value of wheel slip based on wheel torque, wheel speed, and vehicle speed for the wheels of the vehicle and if the wheel slip for one wheel exceeds a threshold, the twist force may be applied to increase a normal force load on that wheel.