Observer based adaptive fixed‐time control of flexible‐joint manipulators

Abstract This paper focuses on the adaptive practical fixed‐time control problem for flexible‐joint manipulators with unmeasurable states and unmodeled dynamics. A state observer is constructed to estimate the unmeasurable states. The unmodeled dynamic characteristics and the construction of first‐order dynamic signals are used to deal with dynamic uncertainties. Dynamic surface control (DSC) and command filtered backstepping (CFB) are integrated. The black‐box functions requiring mathematical induction to determine variables during the design process in traditional DSC are eliminated. A compensation mechanism is developed by introducing the compensation signals. The compensation errors, compensation signals, and state estimation errors are incorporated into the whole Lyapunov function. Based on fixed‐time control theory, all signals in the closed‐loop system are proven to be semi‐global practical fixed‐time stable (SGPFTS). Ultimately, the simulation results verify the feasibility of the proposed adaptive control strategy.