Indirect-Relay Autotuning: A Model-Free Approach to Robust PID Controller Design and Implementation
摘要
Model-free design approaches are favoured for controller design when dealing with complex process models or models that lack accurate mathematical representation. This article presents a relay autotuning method for the PID controller for stable processes. By conducting a single ideal relay test, a limit cycle output is generated to aid in the Proportional–Integral–Derivative (PID) controller design. The design process involves two steps: initially, a zero-phase PID controller is derived to ensure a minimum gain margin; subsequently, the phase margin criterion is achieved using the indirect design method (IDA2). The proposed IDA2-relay autotuning method enables users to design a PID controller and adjust its robustness using a single tunable variable, which exhibits a monotonic relationship with robustness. The efficacy of the IDA2-relay PID autotuner is validated through two different simulations on higher-order plants. The experimental validation is also investigated for speed control of the DC motor with IDA2-relay autotuner implemented on Arduino microcontroller board. Under nominal conditions, the proposed method provides enhanced tracking and disturbance rejection, achieving up to 42% reduction in IAE and 29% in ISE compared to existing methods, while maintaining improved robustness. Similarly, in the DC motor experiment, the performance is improved by 3.13% in the presence of load changes.