Adaptive anti-windup protection of cascaded inner and outer control loops
A method of adaptive anti-windup protection for a control system with cascaded inner control loop and an outer control loops. The method includes receiving an outer loop feedback signal indicative of the response of a plant controlled by the outer control loop and calculating an inner control loop request such that, it would cause saturation of the control device controlled by the inner control loop. The method also includes converting the calculated inner loop request to outer loop anti-windup request limits using kinematic relationships and transmitting the outer loop anti-windup request limits to a controller of the outer control loop. The method may also include applying the outer loop anti-windup request limits to a controller of the outer control loop to limit the inner loop request generated thereby, and executing an outer control loop control law and an inner control loop control law subject to the anti-windup request limits.
1. A method of adaptive anti-windup protection for a control system with cascaded inner control loop and an outer control loops, the method including:
receiving an inner control loop feedback signal indicative of a response of a control device controlled by an inner control loop;
calculating an inner control loop request such that, it would cause saturation of the control device controlled by the inner control loop;
determining outer loop anti-windup request limits based at least in part on the inner control loop request and kinematic relationships between the control device and a plant;
modifying the outer loop anti-windup request limits when the control device controlled by the inner control loop operates at saturation; and
providing the outer loop anti-windup request limits to a controller of the outer control loop.
2. The method of adaptive anti-windup protection of claim 1 , further including:
applying the outer loop anti-windup request limits to a controller of the outer control loop to limit the inner control loop request generated thereby;
receiving an outer loop feedback signal indicative of a response of the plant controlled by the outer control loop;
executing an outer control loop control law based on the outer loop anti-windup request limits; and
executing an inner control loop control law subject to the outer loop anti-windup request limits.
3. The method of adaptive anti-windup protection of claim 1 , wherein the control device controlled by the inner control loop is an actuator.
4. The method of adaptive anti-windup protection of claim 3 , wherein the inner control loop feedback signal is at least one of a position of the actuator, a rate of the actuator, and a current drawn by the actuator under selected conditions.
5. The method of adaptive anti-windup protection of claim 1 , wherein calculating the inner control loop request is based on at least one of the inner control loop feedback signal, a command of the control device controlled by the inner control loop that would result in saturation of the control device, and an inverse of a transfer function of a controller of the inner control loop.
6. The method of adaptive anti-windup protection of claim 1 , wherein the plant controlled by the outer control loop is a gas turbine engine.
7. The method of adaptive anti-windup protection of claim 6 , wherein the outer loop feedback signal is at least one of a pressure, a temperature, a fuel flow associated with the gas turbine engine under selected conditions.
8. The method of adaptive anti-windup protection of claim 1 , wherein the outer loop anti-windup request limits permit the control device controlled by the inner control loop faster response in operation than predetermined limits.
9. The method of adaptive anti-windup protection of claim 1 , wherein the outer loop anti-windup request limits permits more robust anti-windup protection under degraded operating conditions of the control device controlled by the inner control loop, wherein the degraded operation include sticking or sluggish operation compared to specified operation.
10. A control system with cascaded inner control loop and an outer control loops having adaptive anti-windup protection, the control system comprising:
a control system including a controller having an cascaded inner control loop and the outer control loop;
a control device responsive to the inner control loop;
a plant responsive to the control device and the outer control loop;
wherein the controller is configured to:
receive an inner control loop feedback signal indicative of a response of a device controlled by the inner control loop;
calculate an inner control loop request such that, it would cause saturation of the device controlled by the inner control loop;
determine outer loop anti-windup request limits based at least in part on the inner control loop request and kinematic relationships between the control device and the plant;
modify the outer loop anti-windup request limits if the device controlled by the inner control loop operates at saturation; and
provide the outer loop anti-windup request limits to a controller of the outer control loop.
11. The control system of claim 10 , wherein the controller is further configured to:
apply the outer loop anti-windup request limits to a controller of the outer control loop to limit the inner control loop request generated thereby;
receive an outer loop feedback signal indicative of a response of the plant controlled by the outer control loop;
execute an outer control loop control law based on the outer loop anti-windup request limits; and
execute an inner control loop control law subject to the outer loop anti-windup request limits.
12. The control system of claim 10 , wherein the control device controlled by the inner control loop is an actuator.
13. The control system of claim 12 , wherein the inner control loop feedback signal is at least one of a position of the actuator, a rate of the actuator, and a current drawn by the actuator under selected conditions.
14. The control system of claim 10 , wherein calculating the inner control loop request is based on at least one of the inner control loop feedback signal, a command of the device controlled by the inner control loop that would result in saturation of the device, and an inverse of a transfer function of a controller of the inner control loop.
15. The control system of claim 10 , wherein the plant controlled by the control device and the outer control loop is a gas turbine engine.
16. The control system of claim 15 , wherein the outer loop feedback signal is at least one of a pressure, a temperature, and a fuel flow associated with the gas turbine engine under selected conditions.
17. The control system of claim 10 , wherein the outer loop anti-windup request limits permit the control device controlled by the inner control loop faster response in operation than predetermined limits.
18. The control system of claim 10 , wherein the outer loop anti-windup request limits permits more robust anti-windup protection under degraded operating conditions of the control device controlled by the inner control loop, wherein the degraded operation include sticking or sluggish operation compared to specified operation.