In this paper, a novel adaptive fault-tolerant controller is proposed for a typical electrohydraulic rotary actuator in the presence of disturbances, internal leakage fault, and sensor fault simultaneously. To construct the suggested controller, a nonlinear unknown input observer is developed to effectively identify the sensor fault, which is unaffected by not only internal leakage fault but also mismatched disturbances/uncertainties. Furthermore, a radial basis function neural network is designed to compensate for the mismatched disturbances/uncertainties caused by payload variation and unknown friction nonlinearities. Besides, an adaptive law based on the projection mapping function is applied to tackle the effect of the internal leakage fault. The integration of the above-mentioned techniques into the adaptive backstepping terminal sliding mode is investigated to obtain high tracking performance, robustness as well as fast convergence. The stability of the closed-loop system is proven by the Lyapunov theory. Finally, the capability and effectiveness of the proposed approach are validated via simulation results under various faulty scenarios.

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Over the past few years, triboelectric nanogenerators (TENGs) have emerged as promising devices for energy harvesting and self-powered sensing owing to their miniaturized structural design, lack of material limitation, high stability, and ecofriendly nature. In this study, the membrane consisting of poly(vinylidene fluorideco-hexafluoropropylene) (PVDF-HFP) and ionic liquid (PIL) is fabricated as triboelectric material, namely PIL membrane. To further improve the hydrophobicity of the membrane and the output performance of the TENG, different PIL membranes are prepared using various IL concentrations and their structures are modified using the evaporation phase inversion technique. The PIL membranes with nanoporous structures and strong hydrophobicity are synthesized by blade coating and bent to generate circular tube shapes for use in PIL-TENG cells. Therefore, the PIL-TENG has a high output performance owing to the availability of more ions through the establishment of an electrical double layer and an increase in electronegativity properties by doping with more fluoride atoms. Under optimal conditions, a nanoporous PIL-TENG of 10 wt.% ionic liquid exhibited the maximum peak-to-peak with an output voltage of 16.95 V and current of 2.56 μA. Especially, the instantaneous peak power density of the PIL-TENG reached the highest value of 26.1 mW/m 2 , which was 212% higher than that of the pristine PVDF-HFP TENG (P-TENG). In this manner, a new material for the triboelectric layer is presented to effectively improve the output performance, stability, and durability of TENGs, which are promising for use in practical applications related to harvesting hydrokinetic energy, self-powered sensors, and other applications.

This paper develops a novel adaptive gain integral terminal sliding mode control with timedelay estimation to enhance the control performance of a pneumatic artificial muscle system. The main contribution of the paper is that the proposed control method can enable the benefits of both terminal sliding mode technique and an integral sliding mode approach. Thus, the controlled system not only achieves finite time convergence and robust performance but also attenuates the drawback of the reaching phase in the conventional sliding mode control approach. To develop the control algorithm, the mathematical of the pneumatic artificial muscle system is first design, which includes a nominal system and all uncertainties and disturbances in the system dynamics. Then, a backstepping terminal sliding mode is designed to achieve a finite time convergence of tracking errors in the nominal system. In addition, an integral terminal sliding mode approach is proposed to reject the uncertainties and disturbances. To enhance the control performance, a time-delay estimation is employed to approximate the nonlinearity and disturbance in the system and an adaptive gain scheme is coupled directly to estimate the ideal robust control gain, which can reduce the chattering phenomenon and increase the tracking accuracy. The stability of the controlled system is analyzed using Lyapunov theory. Moreover, the effectiveness of the proposed control algorithm is verified through a series of experimental tests on a developed pneumatic artificial muscle system.INDEX TERMS Integral terminal sliding mode control, pneumatic artificial muscle, adaptive gain scheme, time-delay estimation.

This paper presents a novel force sensorless reflecting controller for a haptic-enabled device driven by a bilateral pneumatic artificial muscle system, which proposed configuration for the first time the bilateral haptic teleoperation. For details, an adaptive force observer scheme considered to be an alternative to direct force measurement is proposed to estimate the interaction force with an unknown environment for the force reflecting control design. Meanwhile, the separately fast finite time nonsingular terminal sliding mode control schemes are developed based on the force estimation in both subsystems to achieve good tracking performance and fast response. Thus, the great transparency performance with both force feedback and position tracking can be achieved simultaneously by using our proposed method. The finite-time stability of the total controlled system is demonstrated by the Lyapunov approach. Moreover, the comparative experiments are carried out on the developed testbench to validate the effectiveness and advantages of our proposed control design in the different working conditions. INDEX TERMS Bilateral teleoperation system, pneumatic muscle actuator, force observer.

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