Question

Task 1: (preferably not hand written)

a) Describe briefly (about 250 words) a method of tuning a PID controlled system that would NOT be suitable for tuning a critical system such as a power plant, and explain why.

b) Describe briefly (about 250 words) a method of tuning a PID controlled system that is suitable for tuning a critical system such as a power plant, and explain why.

Thanks

Answer 1

a) Trial and Error method:

=>This is simple method for tuning a pid controller. The trial and error method become relatively easy.

=>Set integral and derivative terms to zero first and then increase the proportional gain until the output of the control loop oscillates at a constant rate.

=>This increase of proportional gain should be in such that response the system becomes faster provided it should not make system unstabe. Once the P response is fast enough .

=>so that the oscillations will be gradually reduced. Change this Integral value untill the state error is reduced. but it may increase overshoot.

=>Once P and integral parameters have been set to a desired values with minimal steadty state error, increase the derivative term decrease the overshoot of the controller response

Thats way it is not suitable method for tunning a critial system such as a power plant and etc.

b)Zeiger-Nichols method:

=>Ziegler and Nichols presented two classical methods for determining values of proportional gain ,Integral time and derivative timebased on transient response characteristics of a given plant or system.

=>It is performed by setting the integral and derivative gains to zero.

=>The proportional gain Kp is then increased until reaches the ultimate gain Ku at which the output of the control loop has stable and consisent oscillations.Ku ans the oscillation period are used to set the P,I,and D gains depending on thetype of xontroller used.

=>The ziegler -Nicholas tuning creates a 'quater wave decay". This is an acceptable result for some purposes ,but not optimal for all applications.

=>Best method for tuning of PID controlled system is Ziegler -Nichols Method.