Slip control via active suspension for optimization of braking and accelerating of a vehicle
System and method for improving braking efficiency by increasing the magnitude of a frictional force between a tire of a vehicle wheel and a road surface. Braking efficiency may be improved by controlling the normal force applied on the wheel, with an active suspension actuator, based on the wheel's slip ratio.
1. A method for controlling an active suspension system of a vehicle, comprising:
calculating a first slip ratio for a first wheel of the vehicle based on information from at least one sensor;
comparing, by a processor, the first slip ratio to a threshold; and
when the first slip ratio exceeds the threshold, driving, based on a first command from the processor, a first actuator associated with the first wheel to reduce the first slip ratio to a level below the threshold.
2. The method of claim 1 , further comprising:
increasing, based on the first command, a normal force on the first wheel.
3. The method of claim 1 , further comprising:
determining, based on the first command, a command force based on the first slip ratio or a slip gain; and
applying the command force to the first wheel.
4. The method of claim 3 , wherein the slip gain is selected to control a sensitivity of the active suspension system to the first command.
5. The method of claim 1 ,
wherein reducing the first slip ratio below the threshold comprises increasing, by applying a command force to the first actuator, a magnitude of normal force by extending a length of the first actuator.
6. The method of claim 5 , wherein increasing the magnitude of the normal force comprises extending the length of the first actuator at a predetermined rate.
7. The method of claim 1 , further comprising:
calculating a second slip ratio for a second wheel based on information from the at least one sensor;
comparing, using the processor, the second slip ratio to the threshold; and
when the second slip ratio exceeds the threshold, driving, based on a second command from the processor, a second actuator associated with the second wheel to reduce the second slip ratio to a level below the threshold.
8. The method of claim 1 , wherein the threshold is a critical slip ratio.
9. The method of claim 1 , wherein the threshold is greater than a critical slip ratio.
10. A method for controlling an active suspension system of a vehicle having a plurality of actuators associated with a plurality of wheels respectively, the method comprising:
determining, based on at least one sensor, a plurality of slip ratios for each of the plurality of wheels;
based on the plurality of slip ratios, estimating variations in a distribution of a normal load on one or more wheels;
controlling, by a processor, a distribution of a plurality of normal loads on the plurality of wheels based on the plurality of slip ratios; and
providing, by the processor, a command to each of the plurality of actuators configured to reduce a variation in the distribution of a distribution of slip ratio magnitudes.
11. The method of claim 1 , further comprising controlling at least one actuator of the plurality of actuators based on one or more commands.
12. The method of claim 1 , wherein a variation in the distribution of the plurality of normal loads is reduced by increasing a normal force on at least one wheel associated with at least one actuator.
13. The method of claim 12 , wherein increasing the normal force reduces a slip ratio associated with the at least one wheel.
14. The method of claim 10 , further comprising predicting, based on at least one vehicle maneuver, the distribution of the plurality of normal loads.
15. The method of claim 14 , wherein the at least one vehicle maneuver is selected from the group consisting of: a braking maneuver, an acceleration maneuver, and a steering maneuver.
16. The method of claim 14 , wherein the predicting is based on an input of at least one sensor.
17. The method of claim 16 , wherein the at least one sensor is selected from the group consisting of: an accelerometer, a brake pedal position sensor, an acceleration pedal position, a brake pedal position rate of change sensor, and an acceleration pedal position rate of change sensor.