Controlling damper friction effects in a suspension
In some examples, a vehicle suspension for supporting, at least in part, a sprung mass, includes a damper connected to the sprung mass, the damper including a movable piston. The vehicle suspension further includes an actuator and a controller. The controller may be configured to determine a frequency of motion associated with the sprung mass. When the frequency of motion is below a first frequency threshold, the controller may send a control signal to cause the actuator to apply a deceleration force to the sprung mass. Further, when the frequency of motion associated with the sprung mass exceeds the first frequency threshold, the controller may send a control signal to cause the actuator to apply a compensatory force to the sprung mass. For instance, a magnitude of the compensatory force may be based on a friction force determined for the damper.
1. A vehicle suspension system for supporting, at least in part, a sprung mass, the system comprising:
a damper supporting the sprung mass, the damper including a movable piston; an actuator;
a controller configured to perform operations comprising:
determining a frequency of motion associated with the sprung mass;
when the frequency of motion associated with the sprung mass is below a first frequency threshold, sending a control signal to cause the actuator to apply a deceleration force to the sprung mass; and
when the frequency of motion associated with the sprung mass exceeds the first frequency threshold, sending a control signal to cause the actuator to apply a compensatory force to the sprung mass, wherein a magnitude of the compensatory force is based on a friction force determined for the damper.
2. The system as recited in claim 1 , the operations further comprising:
determining a lateral acceleration associated with the sprung mass;
when the lateral acceleration is below a lateral acceleration threshold, causing the actuator to apply the compensatory force to the sprung mass; and
when the lateral acceleration exceeds the lateral acceleration threshold, causing the actuator to apply the deceleration force to the sprung mass.
3. The system as recited in claim 2 , the operations further comprising:
determining that a steering wheel angle is less than a threshold steering wheel angle; and
based on the steering wheel angle determined to be less than the threshold steering wheel angle, determining the magnitude of the compensatory force to apply to the sprung mass or a magnitude of the deceleration force to apply to the sprung mass based on the frequency of motion associated with the sprung mass.
4. The system as recited in claim 2 , the operations further comprising:
determining that a steering wheel angle exceeds a threshold steering wheel angle; and
based on the steering wheel angle exceeding the threshold steering wheel angle, determining the lateral acceleration associated with the sprung mass.
5. The system as recited in claim 2 , the operations further comprising:
determining a gain for the frequency associated with the unsprung mass;
determining a gain for the lateral acceleration; and
determining the magnitude of the compensatory force and/or a magnitude of the deceleration force based on the friction force and at least one of the gain for the frequency or the gain for the lateral acceleration.
6. The system as recited in claim 1 , the operations further comprising:
determining a velocity associated with the piston; and
determining the friction force based on the velocity associated with the piston.
7. The system as recited in claim 6 , the operations further comprising:
receiving first sensor data from a first sensor associated with an unsprung mass including the damper and the actuator;
receiving second sensor data from a second sensor associated with the sprung mass;
and determining the velocity associated with the piston based on at least one of the first sensor data or the second sensor data.
8. The system as recited in claim 1 , wherein:
the friction force determined for the damper is determined at least in part based on at static friction between the piston and a cylinder of the damper and Coulomb friction between the piston and the cylinder; and
the magnitude of the compensatory force and a magnitude of the deceleration force are proportional to the friction force determined for the damper.
9. The system as recited in claim 1 , the operations further comprising:
determining a lateral acceleration associated with the sprung mass;
when the lateral acceleration is below a lateral acceleration threshold, causing the actuator to apply the compensatory force to the sprung mass; and
gradually decreasing the compensatory force as the lateral acceleration increases toward the lateral acceleration threshold.
10. The system as recited in claim 9 , the operations further comprising:
causing the actuator to cease applying the compensatory force before the lateral acceleration reaches the lateral acceleration threshold; and
when the lateral acceleration exceeds the lateral acceleration threshold, causing the actuator to apply a gradually increasing deceleration force to the sprung mass until reaching a deceleration force proportional to the friction force.
11. The system as recited in claim 1 , the operations further comprising:
causing the actuator to gradually decrease the deceleration force as the frequency of motion associated with the sprung mass increases toward the first frequency threshold; and
causing the actuator to apply the compensatory force as gradually increasing when the frequency of motion associated with the sprung mass exceeds the first frequency threshold until reaching the magnitude based on the friction force.
12. The system as recited in claim 1 , the operations further comprising causing the actuator to gradually decrease the compensatory force as the frequency of motion associated with the sprung mass increases toward a second frequency threshold.
13. A method of operating a vehicle suspension supporting, at least in part, a sprung mass, the vehicle suspension including a damper, the method comprising:
determining, by a controller, a frequency of motion associated with the sprung mass;
when the frequency of motion associated with the sprung mass is below a first frequency threshold, sending a control signal to cause an actuator to apply a deceleration force to the sprung mass; and
when the frequency of motion associated with the sprung mass exceeds the first frequency threshold, sending a control signal to cause the actuator to apply a compensatory force to the sprung mass, wherein a magnitude of the compensatory force is based on a friction force determined for the damper.
14. The method as recited in claim 13 , further comprising:
determining a lateral acceleration associated with the sprung mass;
when the lateral acceleration is below a lateral acceleration threshold, causing the actuator to apply the compensatory force to the sprung mass; and
when the lateral acceleration exceeds the lateral acceleration threshold, causing the actuator to apply the deceleration force to the sprung mass.
15. A non-transitory computer-readable medium storing instructions which, when executed by one or more processors associated with a vehicle suspension, program the one or more processors to perform operations comprising:
determining a frequency of motion associated with a sprung mass supported, at least partially, by the vehicle suspension;
when the frequency of motion associated with the sprung mass is below a first frequency threshold, sending a control signal to cause an actuator to apply a deceleration force to the sprung mass; and
when the frequency of motion associated with the sprung mass exceeds the first frequency threshold, sending a control signal to cause the actuator to apply a compensatory force to the sprung mass, wherein a magnitude of the compensatory force is based on a friction force determined for a damper included in the vehicle suspension.