Recursive model free controller: Application to friction compensation and trajectory tracking

Transactions of the Institute of Measurement and Control

2018

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This paper addresses the sampled and unknown time-varying delayed output problem of the continuous-time linear system with unknown input disturbance and measurement noise. Based on the piecewise continuous hybrid system and extended functional observer, a robust hybrid extended observer is proposed to estimate the non-delayed continuous state from the sampled and delayed measurements when the time delay is unknown time-varying. The advantages of the designed observer are the quite simple structure, robustness to dealing with measurement noise, and ability to estimate the system state with accuracy under the influence of unknown input disturbance. Furthermore, the proposed observer is able to estimate the non-delayed continuous state and unknown input disturbance, in particular for the issue of fault estimation and perturbation disturbance simultaneously. The stability of the robust hybrid extended observer is illustrated and analyzed. Moreover, to show the effectiveness of the proposed observer, a comparison with the delayed Luenberger observer is performed via a numerical example. Finally, the simulation results are demonstrated.

Section: Resultsmentioning

confidence: 99%

State observer for linear system with unknown input disturbance and sampled and delayed output with measurement noise

Mohammed

Wang²,

Transactions of the Institute of Measurement and Control

2018

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“…(Van et al., 2013; Ahmed et al., 2016), whereas the model-free control technique does not rely on the dynamic model or where plant dynamics are completely unknown such as proportional–integral–derivative control (PID) and recursive model free control, etc. (Belforte et al., 2011; Wang et al., 2011). The abovementioned model-free schemes are easy to implement and model-independent, but these are sensitive and not robust to parameter variations and external disturbances.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the model-free approach is preferred, and it has a capability to control the unknown uncertain dynamics of the exoskeleton. In literature, various model-free techniques have been proposed such as extended state observer, time delay estimation (TDE), recursive model-free control, intelligent proportional-integral (PI)/ (PD)/ (PID), and so on (Wang et al., 2011; Fliess and Join, 2013; Zhao et al., 2015; Jin et al., 2017). However, the TDE method has a simple structure, is easy to implement, and is robust to estimate the unknown uncertain system’s dynamics by using time delayed systems (Youcef-Toumi and Ito, 1988; Hsia et al., 1991).…”

Section: Introductionmentioning

confidence: 99%

Model-free control using time delay estimation and fractional-order nonsingular fast terminal sliding mode for uncertain lower-limb exoskeleton

Ahmed

Wang

Journal of Vibration and Control

2018

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A robotic exoskeleton is a nonlinear system, which is subjected to parametric uncertainties and external disturbances. Due to this reason, it is difficult to obtain the exact model of the system, and without knowledge of the system, it cannot be compensated accurately. In this study, time delay estimation (TDE)-based model-free fractional-order nonsingular fast terminal sliding mode control (MFF-TSM) is proposed for the lower-limb robotic exoskeleton in the existence of uncertainties and external disturbance. The main characteristic of the proposed scheme is that it controls the system without relying on the knowledge of exoskeleton dynamics. At first, the fractional-order (FO) with nonsingular fast terminal sliding mode control (NFTSM) is adopted to provide a precise trajectory tracking performance, fast finite-time speed of convergence, singularity-free and chatter-free control inputs. And then, the proposed controller employs TDE, to make the controller model independent, which directly estimates the uncertain exoskeleton dynamics with external disturbances. Later, asymptotical stability analysis of the overall system and finite-time convergence are investigated and ensured using Lyapunov theorem. Finally, the simulation results are conducted to validate the efficacy of the proposed control method.

“…It plays a particularly important role in improving the quality and precision of machine products. The XY table can move along the X axis and Y axis respectively . In the process of each axis movement, nonlinear friction effects are more apparent, especially at low start speeds, stop, or changing speed direction.…”

Section: Introductionmentioning

confidence: 99%

Trajectory Tracking Control of XY Table Using Sliding Mode Adaptive Control Based on Fast Double Power Reaching Law

Wang

Zhao

Asian Journal of Control

2016

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Currently, high velocity and precision are the main developing directions of the XY table. However, the nonlinear effects of friction at low speed deteriorate the precision of the XY table servo system. As a result, it is very important to design a control method to carry out friction compensation and trajectory tracking. In this paper, dual sliding mode state observers are used to estimate these immeasurable parameters in the dynamic LuGre model, and the Lyapunov function is used to design the adaptive update law. In addition, fast double power reaching law has the advantage of improving the global asymptotic convergence rate and overcoming these disadvantages where traditional sliding mode control reaching law causes severe chattering. Simulation results that compare the proposed method with exponent sliding mode control and PID control, demonstrate that the fast double power sliding mode control guarantees position and speed signals, tracking the desired references asymptotically.