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Abstract: The paper presents a PI tuning strategy for air handler discharge air temperature control in building comfort application. It recommends using a 5min settling time with no overshoot as the design criterion to select PI gain values, and recommends that a PI controller should be retuned when the settling time is larger than 20min. This tuning strategy avoids unnecessary tuning while providing acceptable control performance for building comfort control. The paper further concludes that PI tuning can be done by adjusting proportional gain only and keeping the reset time constant for air handler discharge air temperature control. The proportional gain can be calculated based on the system sum of time constant and delay, and system static gain in typical applications. Inclusion of the time constant in the equation is recommended for uncommon applications where the delay is large. Regression equations are given based on simulation results for both typical applications and uncommon applications. The PI tuning strategy proposed in the paper can be reliably used in PI auto tuning since it uses less model information and adjusts less gain values than existing tuning algorithms. [Copyright &y& Elsevier]

Abstract: In this paper, a simple method to find the minimum output variance (MOV) with proportional–integral-derivative (PID) controller is proposed. An assessment of improved achievable PID performance is important as PID controllers are the most commonly used in industries. The restriction on the controller structure e.g. PID (the case in this paper) results worst output variance compared to minimum variance (MV) benchmark. The problem in assessing the PID-MOV rises a non-convex problem and for non-convex problem, no direct and simple solution is possible. In this paper the non-convex problem is solved with simple ring of iterations. Several simulation examples are incorporated to show the usefulness of proposal algorithm. [Copyright &y& Elsevier]

Abstract: In this paper, comparative performance analysis of various binary coded PSO algorithms on optimal PI and PID controller design for multiple inputs multiple outputs (MIMO) process is stated. Four algorithms such as modified particle swarm optimization (MPSO), discrete binary PSO (DBPSO), modified discrete binary PSO (MBPSO) and probability based binary PSO (PBPSO) are independently realized using MATLAB. The MIMO process of binary distillation column plant, described by Wood and Berry, with and without a decoupler having two inputs and two outputs is considered. Simulations are carried out to minimize two objective functions, that is, time integral of absolute error (ITAE) and integral of absolute error (IAE) with single stopping criterion for each algorithm called maximum number of fitness evaluations. The simulation experiments are repeated 20 times with each algorithm in each case. The performance measures for comparison of various algorithms such as mean fitness, variance of fitness, and best fitness are computed. The transient performance indicators and computation time are also recorded. The inferences are made based on analysis of statistical data obtained from 20 trials of each algorithm and after having comparison with some recently reported results about same MIMO controller design employing real coded genetic algorithm (RGA) with SBX and multi-crossover approaches, covariance matrix adaptation evolution strategy (CMAES), differential evolution (DE), modified continuous PSO (MPSO) and biggest log modulus tuning (BLT). On the basis of simulation results PBPSO is identified as a comparatively better method in terms of its simplicity, consistency, search and computational efficiency. [Copyright &y& Elsevier]

Abstract: In this paper, the design of decentralized PID controller for interactive and delay time processes is proposed. Direct controller synthesis approach is used to obtain parameters of the multi-loop controllers. A detuning factor for each loop is specified based on the closed-loop time constant. Then appropriate controller settings are determined using the Maclaurin series expansion and the model of the process. The success of the proposed algorithm is based on the detuning parameter thus the selection of the desired closed-loop time constant is an important factor. The proposed method has no limitations regarding systems weak or strong interactions, multiple delays, and its operating behaviors such as monotonic or oscillatory. The proposed algorithm is simpler and improved performance of various processes are achieved as compared to some of the prevalent techniques. Simulation examples demonstrate the usefulness of the proposed method. [Copyright &y& Elsevier]

Abstract: Based on the baseline PI control structure, the control parameters of non-linear ALSTOM gasifier benchmark problem are optimized. Firstly, taking all the input and output limits under three load conditions as constraints, the relative IAE indices at six scenarios are calculated and optimized by using multi-objective optimization algorithm NSGA-II. A set of non-dominated solutions are obtained which facilitate the further improvement on the performance under coal quality change. Then among those non-dominated solutions, the solution with best coal quality flexibility comes to the fore through a selection procedure. The simulation results show that the optimization and selection procedure presented in this paper improves the baseline PI control performance with better dynamic responses and coal quality flexibility. [Copyright &y& Elsevier]