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A novel double‐loop control configuration with two controllers is suggested for double integrating processes with dead‐time. The stabilizing range of the inner‐loop proportional‐derivative (PD) controller is obtained using the Routh stability criteria. From this range, the exact PD settings are obtained by following a graphical approach where the integration of absolute error (IAE) is plotted for different PD settings. The PD settings resulting in the minimum IAE are chosen. In addition to stabilizing the plant, the inner‐loop also rejects the disturbances. A fractional‐order internal model controller (FOIMC) is designed for satisfactory set‐point tracking response in the outer‐loop. The suggested strategy has four adjustable parameters (proportional and derivative time constants, outer closed‐loop adjustment parameter, and fractional‐order of the FOIMC low‐pass filter). Based on extensive simulations, the tuning ranges for the above‐mentioned adjustable parameters are specified. The simulation study is done with the help of benchmark double integrating plant models with large dead‐time. Quantitative performance measures are also computed for comparing the suggested and previously reported schemes. The suggested FOIMC‐PD control architecture yields enhanced control performance than some recently reported techniques.

A novel multi-loop control configuration with two controllers is suggested for integrating processes having large dead-time. The inner-loop consists of a Smith predictor having proportional (P)/proportional-derivative (PD) controller for first/second-order integrating processes, respectively. Once the dead-time is compensated by the inner-loop Smith predictor, a fractionalorder internal model controller (FOIMC) is designed in the outer-loop. The P/PD controllers are tuned using direct synthesis methodology. The proposed control architecture has three adjustable parameters (inner and outer closedloop adjustment parameters, fractional-order of the FOIMC low-pass filter).Based on extensive simulations, the tuning ranges for the above-mentioned adjustable parameters are specified. Suitable justification is also provided for the suggested range of tuning parameters. Several benchmark examples of plant models are used to study the set-point following and disturbance elimination capabilities of the proposed control architecture. Quantitative performance measures are also computed for comparing the suggested and previously reported schemes. It is evident that the suggested FOIMC based Smith predictor yields enhanced control performance than some recently reported techniques.

Controlling unstable and integrating type continuously stirred tank reactors (CSTRs) are more difficult due to the presence of poles in the right half and at the origin of the s-plane respectively. The existence of dead-time needs more efficient control requirements for CSTRs. In this work, a modified indirect fractional-order internal model control proportional-derivative (MIFOIMC-PD) decoupled dual-loop control strategy is suggested for unstable and integrating plants with dead time. The external-loop controller is designed using the MIFOIMC strategy for obtaining adequate servo performance. PD controller is designed such that it stabilizes the plant while disturbances occur. Decoupled nature of the suggested strategy allows this PD controller to be designed without considering the external-loop dynamics. Reference tracking and disturbance elimination capabilities of the suggested method are also quantitatively compared with reported methods. It is established that the suggested MIFOIMC-PD control architecture controls CSTRs more effectively than some lately reported schemes.

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Unstable processes are hard to stabilize as they contain one or more positive poles which result in unbounded dynamic behavior. The occurrence of the delay and positive zeros often creates more difficulty in controlling such unstable plants. Most control strategies meant for first-order unstable processes fail to stabilize and control the higher-order unstable processes. Hence, a new dual-loop hybrid control structure is suggested for dead-time unbounded second-order processes with positive/negative zeros. Inner-loop has a stabilizing PID controller. The PID controller parameters are derived by comparing the numerator and characteristic polynomial coefficients in the transfer function for internal-loop servo action. A fractional-order internal model controller (FOIMC) is used in the external-loop. Methods for the selection of outer-loop tuning parameter and fractional-order are also discussed. By comparing the simulation results with a contemporary single-loop scheme, the usefulness of the suggested scheme is proved. The suggested scheme is capable of minimizing the overshoot and improving the overall dynamic performance. Finally, the usefulness of the suggested scheme is also demonstrated by a case study on temperature control of a continuous stirred tank reactor (CSTR) during a first-order irrevocable exothermic reaction.

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In this paper three preferable reference frame used in the simulation of field oriented control of induction machines using d,q two axis theory is discussed. Different reference frames are studied as the variables involved are sinusoidal but to design the compensator for control of these variables it is required to convert them in dc variables because it is easy to analyze the linear equations involving these dc variables. This can be done by assuming the reference frame which is revolving at the same speed as that of the sinusoidal variables so that the net relative speed becomes zero and they behave as dc variables. Keeping in view of the above said need the different reference frames for Field Oriented Control of an Induction Motor are studied and analyzed. The whole system is modeled and simulated in MATLAB/Simulink environment.