Abstract
Although an analytical design approach-based digital controller—which is essentially a deadbeat controller—shows zero steady-state error and no intersampling oscillations, it takes a finite number of sampling periods to settle down to a steady-state value. This paper describes the application of a derivative-free Nelder–Mead (N–M) simplex method to the digital controller for retuning of its coefficients intelligently to ensure improved settling and rise times without disturbing the deadbeat controller characteristics (i.e., no ripples between the sampling periods and no steady-state error). A switching-mode buck regulator working at 1 MHz in continuous conduction mode (CCM) is considered as a plant. Numerical simulation results depict that the N–M algorithm-based optimized digital controller not only shows improved steady-state and transient performance but also guarantees rigorous robustness against model uncertainty and disturbance as compared to its traditional counterpart, as well as the other optimized digital controller fine-tuned through other derivative-free metaheuristic optimization techniques, such as the genetic algorithm (GA). A system generator-based hardware software co-simulation is also performed to validate the simulation results.
Highlights
Regulated DC-to-DC switching regulators are a requirement of modern low-power high-frequency digital devices.Perturbations in input voltage or load current may keep the output voltage unregulated, reducing the devices life
One of the direct search methods (DRMs), named the Nelder–Mead (N–M) simplex method is employed for fine-tuning of the digital compensator, designed on the basis of an analytical design approach
By taking the initial point as a real vector or real array of the coefficients of the digital controller computed through analytical design approach, the algorithm starts minimizing the cost function (the integral of the squared error (ISE)) at each iteration and comes up with the updated coefficients of the digital controller
Summary
Regulated DC-to-DC switching regulators are a requirement of modern low-power high-frequency (for enhancing the integration of devices and passive components) digital devices. PSO (dPSO)-based optimization of digital fractional order PID (FO-PID) controller applied to the buck converter fed DC motor for optimal speed control Optimization techniques such as PSO was employed for optimizing the parameters of the fuzzy controller applied to the Quasi-Z Source converter [14] and for fine-tuning digital PID controller parameters [15]; the magnitude optimum criterion for developing explicit analytical tuning rules for digital PID controllers [16]; the genetic optimization scheme for improving a single-input fuzzy PID controller for the buck regulator [17]; the election campaign optimization algorithm for tuning digital PID controllers for the discrete-time system [18]; the gradient descent method for refining the digital control law for ac-to-dc converters to achieve unity power factor [19].
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