Optimal Fractional Order IMC-Based Series Cascade Control Strategy with Dead-Time Compensator for Unstable Processes
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Optimal Fractional Order IMC-Based Series Cascade Control Strategy with Dead-Time Compensator for Unstable Processes Deep Mukherjee1 · G. Lloyds Raja2 · Palash Kundu3 Received: 29 April 2020 / Revised: 22 July 2020 / Accepted: 7 September 2020 © Brazilian Society for Automatics--SBA 2020
Abstract In industrial unstable processes, disturbance rejection is more challenging task than setpoint tracking. So, cascade control structure is widely used in many chemical processes to reject disturbances. In this work, an advanced dead-time compensatorbased series cascade control structure (SCCS) is suggested for unstable processes. The suggested SCCS has three controllers (named as primary, secondary and stabilizing controllers). Both primary and secondary controllers are designed using fractional order-based internal model control (IMC) approach. The stabilizing proportional–derivative controller is designed using maximum sensitivity considerations and Routh–Hurwitz stability criteria. Optimal values of the closed-loop time constants and fractional orders of IMC filters are obtained using constrained artificial bee colony (ABC) algorithm. This ABC algorithm uses a multi-objective function involving minimization of integral of absolute error, integral of time weighted absolute error and integral of squared error. Simulation studies are conducted using some benchmark plant models used in literature for illustrating the advantages of the proposed strategy compared to the state of the art. Moreover, robust stability of the proposed design is analysed and quantitative performance measures are also computed. Keywords Fractional calculus · IMC · ABC algorithm · Series cascade control · Dead-time compensator · Unstable processes
1 Introduction Series cascade control structure (SCCS) shown in Fig. 1 enhances the performance of unity feedback scheme by including an additional sensor and controller (Seborg et al. 2010). In the basic block diagram of SCCS given in Fig. 1, P1 and P2 indicate the primary and secondary plants. C1 and C2 are the primary and secondary controllers, respectively. Setpoints of the primary and secondary loops are represented by r1 and r2 , respectively. Load disturbances
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Deep Mukherjee [email protected] G. Lloyds Raja [email protected] Palash Kundu [email protected]
1
School of Electronics Engineering, Kalinga Institute of Industrial Technology (DU), Bhubaneswar, India
2
Department of Electrical Engineering, National Institute of Technology Patna, Patna, India
3
Department of Electrical Engineering, Jadavpur University, Kolkata, India
are denoted by d1 and d2 . Temperature control of a stirred chemical reactor and temperature control of natural draft furnace are two practical scenarios where series cascade control is employed (Seborg et al. 2010). A brief review of recent series cascade control methodologies is given by Raja and Ali (2017a). Accordingly, the SCCS and its variants (Lee et al. 2002; Veronesi and Visioli 2011; Jeng and Lee 2012; Jeng 2014; Jeng and Liao 2013; Liu et
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