Design of Reset Control Systems: The PI + CI Compensator

Abstract

Reset compensation has been used to overcome limitations of linear and time invariant (LTI) compensation. In this work, a new reset compensator, referred to as proportional and integral (PI) + CI (Clegg integrator), is introduced. It basically consists of adding a Clegg integrator to a PI compensator, with the goal of improving the closed loop response by using the nonlinear characteristic of this element. It turns out that by resetting a percentage of the integral term in a PI compensator, a significant improvement can be obtained over a well-tuned PI compensator in some relevant practical cases, such as systems with dominant lag and integrating systems. The work is devoted to the development of PI + CI tuning rules for basic dynamic systems in a wide range of applications, including first and higher order plus dead time systems.

Performance analysis of PI and PI+CI compensation for an IPDT process

“…Reset compensation has been successfully applied in several experimental works [5]- [9]. It has been shown that PI compensation may be improved without increasing the cost of feedback (sensitivity to sensor noise) by simply adding in parallel a reset element, known as Clegg integrator (CI) [10], [11], resulting in a reset compensator known as PI+CI [12]. This compensator has been shown to be highly effective in lag dominant processes, and specially in integrating processes.…”

Reset Control for Vibration Disturbance Rejection

“…Some methods exist in literature as both means to tune reset elements and reduce these harmonics. Partial reset, PI+CI [Baños and Vidal (2012)], reset band [Vidal and Banos (2008)], time regularization [Zheng et al (2007)] provide means to counter this issue, but rather as a trade-off between linear and reset control. Further, tuning for these methods is not clear and they are ineffective regarding improvement to disturbance rejection.…”

Stabilization of Magnetic Suspension System by Using Only a First-Order Reset Element without a Derivative Element

“…He used a nonlinear integrator whose output was reset to zero when the input to the integrator crossed zero. Clegg's integrator (CI) is used solely or combined with other control elements, such as a proportional-integralcontroller [3,4]. Then, a first-order reset element (FORE) was proposed for the improvement of transient characteristics in 1975 [5].…”