Windup refers to the phenomenon where a control system operates in a nonlinear region when the controller's output exceeds the input limits of the plant being controlled. Windup can lead to performance degradation in terms of overshoot, settling time and even system stability. Many anti‐windup strategies involve switching and manipulating the integral control component in various ways when saturation occurs aiming to bring control back into the linear region. For better insight into windup, the proportional–integral (PI) plane is now used as a means to explain the phenomenon in terms of the controller's signals. A PI controller with a built‐in closed‐loop integral controller that has a reference set based on the input command and external torque is proposed. The performance for this proposed method is compared against existing conditional integration, tracking back calculation and integral state prediction schemes on second and third order systems using MATLAB/SIMULINK simulations of an induction motor and a DC motor respectively. The proposed controller showed promising potential with its ability to eliminate overshoot in both no load and full load conditions due to the decoupling of its parameters from its response and has the shortest settling time when compared against existing schemes, even in the presence of noise.
The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional-integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.
Proportional‐integral (PI) controller is still a widely used closed‐loop controller in industrial applications due to its simplicity. PI controllers experience difficulty in having both non‐overshoot with short rise time. Such unfavorable response is due to its coupled tuning‐gains and the integral windup, which eventually leads to system instability. Various anti‐windup techniques have been proposed. However, similar to the conventional PI controllers, most of these techniques have coupled proportional and integral tuning gains that affect one another. The controllers contain adaptive switching between the conventional and its designated integral control depending on the saturation state. This paper proposes a robust non‐switching anti‐windup PI controller with semi‐decoupling tuning gain. Speed control simulation and experimental testing are conducted to investigate the impact of the various tuning gain dependency. The proposed controller shows a fast response with no overshoot as compared to the conventional and other non‐switching anti‐windup PI controllers with coupling and decoupling tuning gain at certain loading conditions.
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