Control of uncertainly multi-variable system with fractional PID

This paper proposes a novel method to design fractional order controller with robust stability and disturbance attenuation. The Fractional PID problem is formulated as an H_∞ problem with a controller structure constraint and the controller parameters are optimized to achieve both user-specified robust stability and performance. This problem is solved by Optimization with constraints to minimize a cost function subject to H_∞-norm. Which permit to design a robust fractional order PID technique with robust performances. Better performances using fractional order PID controller can be obtained and is validated through multi-variable process. A comparison to the classical integer order PID controllers for controlling systems with multiple delays is achieved.