sentences:  However, in order to have a realistic response to the control system of the pitch angle, the actuator uses the time constant Tservo, an integrator and limiters so as the pitch angle to be from 0° to 30° with a rate of change (± 10° per sec).From the figure at the right, the reference pitch angle is compared with the actual pitch angle b and then the error is corrected by the actuator.The reference pitch angle, which comes from the PI controller, goes through a limiter.