Adaptive Robust Tracker Design for Nonlinear Sandwich Systems Subject to Saturation Nonlinearities

Abstract

SUMMARY This paper addresses the tracking problem for uncertain nonlinear sandwich systems that consist of two nonlinear subsystems and saturation nonlinearity, which is sandwiched between the subsystems. The considered sandwich system is also subject to a nonsymmetric input saturation constraint. Due to the nonsmooth characteristics of sandwiched saturation nonlinearity and also the input saturation function, the design procedure deals with hard challenges. To overcome these difficulties, a recursive approach is suggested that consists of two phases. For the implementation of the proposed approach, a tracking problem is solved in each phase. In the first phase, the second subsystem with sandwiched saturation nonlinearity is considered and the output tracking problem of the desired time-varying reference signal is solved using backstepping method. The outcome of the first phase is the desired reference signal that should be tracked by the first subsystem in the next phase. In the second phase, the robust control input is designed for the first subsystem by employing adaptive sliding mode technique such that, despite the nonsymmetric input saturation constraint, model uncertainty and external disturbances, the output of the first subsystem follows the desired signal that is obtained in the previous phase. The simulation results for a mechanical sandwich system are illustrated to verify the effectiveness of the proposed control method.

Uniformly ultimately bounded tracking control of sandwich systems with nonsymmetric sandwiched dead-zone nonlinearity and input saturation constraint

“…The tracking problem of sandwich systems with dead-zone nonlinearity has been solved by Song et al (2017) and Azhdari and Binazadeh (2020a). Solving the time-varying output tracking problem for sandwich systems with sandwiched saturation function has been investigated by Azhdari and Binazadeh (2020b; 2020c).…”

Robust Stable Limit Cycle Generation in Multi-Input Mechanical Systems

“…Several solutions have been proposed according to this approach. [11][12][13][14] One of these approach drawbacks is the need for generation of the reference signal and its derivatives up to the relative degree of the system. Therefore, another approach was proposed.…”

Robust output tracking of nonlinear systems with transient improvement via funnel-based sliding mode control

“…The most important control objectives that have been considered in the control of dynamic systems are improving the robustness of systems, improving transient responses, and reducing the steady-state error. To achieve the desired characteristic of the control system, there are several control methods such as sliding mode control (Binazadeh and Shafiei, 2013, 2014; Dastaviz and Binazadeh, 2019, 2020; Mohammadpour and Binazadeh, 2018; Shtessel et al, 2014), Lyapunov redesign (Binazadeh and Rahgoshay, 2016; Kamarudin et al, 2019), H ∞ control (Gholami and Binazadeh, 2019; Aidoud and Sedraoui 2018; Saravanakumar et al, 2018), adaptive control (Adloo and Shafiei 2019; Azhdari and Binazadeh, 2020; Guo and Wen, 2011) and Linear matrix inequality (LMI)-based control (Asadinia and Binazadeh, 2019; Baleghi and Shafiei, 2018; Motahhari and Shafiei, 2020) that focus on the robustness of the closed-loop systems in the presence of uncertain terms and/or external disturbances. These methods have usually been designed based on Lyapunov analysis to meet the desired system performances that lead to the elimination of steady-state error in tracking or regulation problems.…”