Proportional control

About: Proportional control is a research topic. Over the lifetime, 3756 publications have been published within this topic receiving 49050 citations.

Robust Control of PM Spherical Stepper Motor Based on Neural Networks

Abstract: There are many uncertainties and disturbances in the real dynamic system of a spherical stepper motor that make traditional control methods with lower precision, such as uncertain changes of magnetic field, load, and friction that generate speed ripple and deteriorate the 3-D tracking performance of the spherical motor system. In this paper, an available method is proposed to solve them by using neural networks (NNs) and a robust control scheme for improving the performance. First, a simplified torque calculation model based on finite-element method results can guarantee quick prediction of electromagnetic torque with lower error. Thus, the system model considering the friction, load, and disturbances is developed. Second, a robust NN (RNN) control scheme is presented to eliminate uncertainties to improve the tracking robust stability and overcome the undesired influence of uncertainties based on the nonlinear system dynamic model under continuous-trajectory tracking mode. Finally, as an example, the step-response and continuous-tracking processes of the motor using an RNN controller are simulated, and experiments, including the tracking using RNN proportional-differential control, are carried out to confirm the usefulness of the proposed control scheme. The simulation and experimental results of the proposed control scheme on the spherical stepper motor system demonstrate the effectiveness on satisfactory tracking performance.

Online tuning of controllers for an unstable FOPDT process

Abstract: A single-relay feedback test can be used to identify exact model parameters of an unstable first-order plus delay (FOPDT) transfer function when a limit cycle exists. This is only true if the ratio of time delay to unstable time constant is less than 0.693. It is shown how adding an internal proportional (P) feedback can increase this value. The P controller parameter for the identification is set in terms of the steady-state gain of the process, which is assumed to be known a priori. The tuning of two types of controller is discussed: PI and PI-PD. Two methods of controller tuning are proposed; tuning formulas in terms of the plant model parameters; simple auto-tuning rules based on the single-relay feedback test, where necessary with the P feedback controller. It is also shown that a PD in the inner feedback loop gives a better control than a P controller suggested for controlling unstable process. The proposed identification and control methods are simple and give better performance than previous methods for unstable FOPDT processes.

Application of fuzzy logic control for continuous casting mold level control

Abstract: This paper deals with the problem of molten metal level control in continuous casting. Under normal circumstances, proportional integral derivative (PID) control performs quite well, but abnormal conditions (in particular nozzle clogging/unclogging) require manual intervention. Indeed, when the flow of matter into the mold increases suddenly, the PID controller is not always able to prevent large level variations that can even lead to mold overflow. So, a fuzzy controller has been designed using the expert knowledge of the operators for controlling the process during disturbed phases. The paper discusses both the design of the fuzzy logic controller and its integration with the PID in a global control architecture. Results from simulation and successful online implementation are presented.

Robust Model-Following Control of Parallel UPS Single-Phase Inverters

Abstract: This paper presents a robust control technique applied to modular uninterruptible power-supply (UPS) inverters operating in parallel. When compared to conventional proportional-integral (PI) control, the proposed technique improves the response of the output voltage to load steps and to high distorted output currents, reducing the distortion of the output voltage. Furthermore, an excellent distribution of currents between modules is achieved, resulting in fine power equalization between the inverters on stream. The crossover frequency of the different loop gains involved is moderate, so that robustness to variations of the operation point and to modeling uncertainties is achieved. A comparative study with a two-loop conventional PI control scheme is presented. Experimental results on a 1-kVA modular online UPS system confirm the viability of the proposed scheme.