Method and apparatus for controlling an actuator
At least one controller configured to control an actuator of an active suspension system. The at least one controller includes circuitry configured to determine an actuator state, and apply the actuator state and a commanded state to an inverse model of the actuator to produce an actuator command. The circuitry is configured to produce the actuator command by a process that includes performing low pass filtering and phase compensation to correct a phase introduced by the low pass filtering.
1. A method for controlling an actuator, with a first point of attachment attached to a first element of a structure and a second point of attachment attached to a second element of the structure, wherein the actuator includes an electric machine operatively coupled to a hydraulic machine, said method comprising:
(a) utilizing at least one motion sensor to sense a relative motion between the first point of attachment and the second point of attachment, wherein the relative motion is induced by an external stimulus applied to the second element;
(b) with a predetermined transfer function, that relates force applied by the actuator at the first and the second attachment points to relative motion between the attachment points when the electric machine is commanded not to produce a torque, determining a value of a first force, based on the relative motion in (a);
(c) determining a desired output force to be applied to the first element by the actuator in response to the external stimulus;
(d) based at least in part on the value of the first force determined in (b) and the desired output force, providing a command to the electric machine with the controller; and
(e) in response to the command in (d), operating the electric machine, to apply the desired output force, to the first element, with the actuator.
2. The method of claim 1 , wherein the electric machine is an electric motor, wherein the hydraulic machine is a hydraulic pump, wherein providing the command to the electric machine in (d) comprises applying the commanded torque to the hydraulic pump of the actuator with the electric motor.
3. The method of claim 1 , wherein the electric machine is an electric motor, wherein the hydraulic machine is a hydraulic pump, wherein providing the command to the electric machine in (d) comprises applying a commanded current to one or more windings of the electric motor.
4. The method of claim 1 , wherein (d) comprises:
subtracting the determined value of the first force from the desired output force determined in (c) to obtain a differential force; and
inputting the differential force into an inverse transfer function of the actuator to determine the command.
5. The method of claim 1 , wherein the first element is part of a sprung mass of a vehicle and the second element is part of an unsprung mass of the vehicle.
6. The method of claim 1 , wherein the at least one motion sensor includes an accelerometer, a velocity sensor, and/or a position sensor.
7. The method of claim 6 , wherein utilizing at least one motion sensor to sense relative motion between the first element and the second element comprises sensing an acceleration of the first element relative to the second element, a velocity of the first element relative to the second element, and/or a change in position of the first element relative to the second element.
8. The method of claim 5 , wherein the external stimulus is a road surface induced perturbation.
9. The method of claim 8 , wherein the road surface induced perturbation is a velocity of a wheel induced by a road surface irregularity.
10. The method of claim 1 , wherein the predetermined transfer function is at least partially empirically based.
11. The method of claim 1 , wherein the predetermined transfer function is at least partially based on a model of at least one component of the actuator.