Unknown input observer‐based robust adaptive funnel motion control for nonlinear servomechanisms

Abstract

Summary In this paper, an unknown input observer is proposed for servomechanisms with unknown dynamics (eg, nonlinear friction, parameter uncertainties, and external disturbance). An unknown input observer is developed by introducing auxiliary filtered variables in terms of first‐order low‐pass filters, where only one constant (filter parameter) needs to be tuned. A modified funnel variable is developed by using the tracking error to replace the scaling factor to improve the transient and steady‐state performance of the control systems. Then, a sliding mode surface with the new transformed error is defined and used to design a funnel nonsingular terminal sliding mode controller to achieve finite‐time convergence. In addition, the proposed funnel nonsingular terminal sliding mode controller method avoids the singularity problem in the conventional sliding mode control via modifying the terminal sliding manifold. Finally, experimental results are given to illustrate the effectiveness of the suggested control scheme.

Adaptive practical preassigned finite‐time stability for a class of pure‐feedback systems with full state constraints

“…Remark The traditional performance functions in other works are designed as follows: where ρ 0 , ρ ∞ , β , μ , and ι are positive design parameters. Although the pregiven performances, such as the convergence rate, the maximum overshoot, and the steady‐state error, can be achieved by ρ 1 ( t ) and ρ 2 ( t ), the convergent time is infinite.…”

“…Remark 2. The traditional performance functions in other works [40][41][42][43][44] are designed as follows:…”

Echo State Network for Extended State Observer and Sliding Mode Control of Vehicle Drive Motor with Unknown Hysteresis Nonlinearity

“…In order to precisely control the tracking errors, Na et al [2] utilized the prescribed performance function to control the vehicles suspensions. Wang et al [3,4] designed an adaptive controller to precisely control the model of PMSM with funnel motion control that is similar to that in literature [2]. Huang et al [5] proposed an approximation-free control strategy which does not need function approximators (e.g., neural networks and fuzzy logic systems) for the vehicles suspension [2].…”

“…Many real electric vehicle systems cannot obtain all the model states directly, and then the observer will be utilized to estimate the unknown states or parameters. In general, the observer is utilized to estimate two categories of unknowns in controlled systems: disturbances and states [4,[20][21][22][23][24]. Many different observers have been applied to approximate the states or disturbances for many years.…”

Trajectory tracking control for manned submersible system with disturbances via disturbance characterization index approach

“…Furthermore, some DOBC methods are proposed to attenuate and reject the disturbances for stochastic Markovian jump system . In addition, the DOBC methods have also been applied to various engineering systems, such as unmanned helicopter system, DC motor system, servomechanisms system, underwater robot system, distillation column system, and so on.…”