Abstract:In this paper, the discrete differentiation order functions of the variable, fractional-order PD controller (VFOPD) are considered. In the proposed VFOPD controller, a variable, fractional-order backward difference is applied to perform closed-loop, system error, discrete-time differentiation. The controller orders functions which may be related to the controller input or output signal or an input and output signal. An example of the VFOPD controller is applied to the robot arm closed-loop control due to system changes in moment of inertia. The close-loop system step responses are presented.
PACS
IntroductionPID control strategies, for over 60 years, have been a fundamental structure in the control with feedback field [1, 2]. The PD controller structure is used in electrical drives [3], in robotics [4][5][6] and where the robot arm has integration properties driven by DC motor systems [5].In such a closed-loop system (CLS) structure, a zero steady state is achieved fora stepwise reference input [7][8][9][10][11][12]. Additionally a PD controller improves the CLS sta- *