Disturbance rejectionGoal: To demonstrate disturbance rejection of the controlled system. Demonstrations: Using fan as a disturbance source and for down – down position, (a) The controller is able to stabilize the pendulum in perpendicular position by rejecting disturbance, for example, i. Pulse disturbance, and ii. Step disturbance Whereas if the controller is turned off for pulse disturbance, it takes a long time to track the reference. And for step, it never tracks the reference. (b) As the disturbance level becomes higher, controller will take more time. Using fan as a disturbance source and for down – up position, (c) The controller is able to stabilize the pendulum in perpendicular position by rejecting disturbance, for example, i. Pulse disturbance, and ii. Step disturbance If the controller is off, system without disturbance itself cannot track the reference. (d) As the disturbance level becomes higher, system is disturbed more and it puts more effort to reject the same (this will be visible in controller output). And after a range allowed by the controller, The controller would fail as the disturbance is high. Inputs: (a) Disturbance type: user can select either of pulse or step disturbance. (b) Disturbance level: user can select either of three disturbance levels and see how the system behaves. One low, second medium and third high. Outputs: (a) Disturbance level: this can be pre-calibrated and stored in the computer. (b) Angle between pendulum and ground or error signal i.e. angle between pendulum and normal line to ground. (c) Settling time: time taken to reject the disturbance. First objective: Take up the simplest objective demonstration (a) then implement and integrate all required elements. This includes rotational pendulum set up, computer, user interface on computer screen and joystick. This would serve as a framework for remaining demonstrations (b), (c) and (d).