The proportional–integral plus Clegg integrator (PI + CI) controller is a hybrid extension of the proportional–integral (PI) controller that is able to overcome fundamental limitations of the linear and time-invariant control systems, potentially obtaining faster responses without increasing overshooting. This work focused on the analysis and design of PI + CI controllers and reset controllers in general, for the case of parallel multiple-input single-output (MISO) systems, extending previous design methods developed for the single-input single-output (SISO) case. Several design strategies were developed: one for first-order MISO plants achieving a flat response with a finite settling time, and for second-order MISO plants obtaining a fast response with a reduced overshoot and settling time in comparison with non-hybrid strategies. Several case studies were also developed to illustrate the potential of the proposed methods.

Hybrid control systems are able to go beyond fundamental limitations inherent to linear and time-invariant control systems. In this work, we employ a parallel control strategy based on a hybrid enhancement of the proportional-integral (PI) controller, the proportional-integral plus Clegg integrator (PI+CI) controller, in conjunction with a novel hybrid control approach (reset-and-hold strategy) to virtually eliminate overshooting in multiple-input single-output (MISO) first order LTI plants with time delay, all the while maintaining response velocity. This goes beyond earlier findings for both single-input systems with delay and MISO systems without delay. In an experimental case study, the developed method was successfully used to control the temperature of a heat exchanger in a pilot plant for food processing.