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The ionic polymer metal composite (IPMC) actuator is a kind of soft actuator that can work for underwater applications. However, IPMC actuator control suffers from high nonlinearity due to the existence of inherent creep and hysteresis phenomena. Furthermore, for underwater applications, they are highly exposed to parametric uncertainties and external disturbances due to the inherent characteristics and working environment. Those factors significantly affect the positioning accuracy and reliability of IPMC actuators. Hence, feedback control techniques are vital in the control of IPMC actuators for suppressing the system uncertainty and external disturbance. In this paper, for the first time an adaptive full-order recursive terminal sliding-mode (AFORTSM) controller is proposed for the IPMC actuator to enhance the positioning accuracy and robustness against parametric uncertainties and external disturbances. The proposed controller incorporates an adaptive algorithm with terminal sliding mode method to release the need for any prerequisite bound of the disturbance. In addition, stability analysis proves that it can guarantee the tracking error to converge to zero in finite time in the presence of uncertainty and disturbance. Experiments are carried out on the IPMC actuator to verify the practical effectiveness of the AFORTSM controller in comparison with a conventional nonsingular terminal sliding mode (NTSM) controller in terms of smaller tracking error and faster disturbance rejection.

In the trend of the recent development of soft actuators, ionic polymer metal composite (IPMC) is considered as one of the new and innovative soft materials. The IPMC is suited to be utilised in medical micro robots and bio-inspired aquatic robotics. It is distinguished by nimble, soft, silent, flexible and lightweight properties. In fact, for the IPMC actuator, hysteresis and creep non-linearities are inevitable; and it is a great challenge to handle them and to achieve high-precision tracking in the control design, especially when the internal system morphology is complex and not fully understood. This study proposes a new model-free control approach for an underwater IPMC actuator to overcome the lack of its exact model and to achieve accurate trajectory tracking. This approach is synthesised based on a non-linear extended state observer technique to estimate lumped uncertainties and disturbances. Furthermore, a …

This study proposes a robust second-order terminal sliding mode control with perturbation estimation (2OTSMCPE) strategy with application to trajectory tracking control of the flexure-based nanopositioning system. The proposed controller advantages not only lie on its finite-time convergence but also can provide a high tracking precision with a chattering alleviation which is attend by employing a second-order sliding surface with the switching function. The model of the piezo-driven nanopositioning system is presented first. Second, the sliding variable is designed such as proportional–integral–derivative form to enhance the dynamic response of the control system. Then, a non-singular terminal sliding function (NTSM) is used to achieve the finite-time convergence of the linear sliding variable. Next, a perturbation estimation technique is integrated with the control structure for online estimation of the system …

The ionic polymer metal composite (IPMC) actuator is one of the most promising smart actuators that possesses unique advantages and is suitable for underwater applications. However, there are challenges to employ it directly in such applications for precise tracking. The IPMC suffers from high nonlinearity due to the existence of inherent creep and hysteresis phenomena. Furthermore, the IPMC actuator is always subject to uncertainty and external disturbance due to the working environment. Therefore, to cope with the aforementioned restrictions and to make the IPMC applicable for real-life applications, designing a high-accuracy tracking control technique is an urgent demand. In this article, a new integral nonlinear hyperplane-based sliding mode controller is dedicated for an underwater IPMC actuator. The proposed controller employs an adaptive tuning law in the discontinuous part to overcome any prerequisite for knowing the upper bound of the model uncertainty and external disturbance. Extensive experiments have been carried out to verify practical effectiveness of the proposed controller in comparison with conventional nonsingular terminal sliding mode in terms of fast convergence, accurate tracking, and the robust performance.

Ionic polymer metal composite (IPMC) is a highly innovative material that has recently gained attention in many fields such as medical, biomimetic, and micro/nano underwater applications. The main characteristic of IPMC lies in its ability to achieve a large deflection under a fairly low driving voltage. Moreover, its agile, light weight, noiseless and flexible features render it well suited for certain specific applications. Like other smart materials, such as piezoelectric ceramics, IPMC could be used in actuators or sensors. In this paper, we study the application of IPMC as an actuator for underwater use. The goal is to develop a robust feedback controller for the IPMC actuator to track a desired reference whilst dealing with the uncertainties due to the inherent actuator nonlinearity, external disturbance or the variations of working environment. To this end, we first present a nominal model of the IPMC actuator through experimental identification. Next, a nonsingular terminal sliding mode controller is proposed. Lastly, experimental studies are conducted to verify the tracking accuracy and robustness of the designed controller.

Ionic polymer metal composite (IPMC) material is one of the innovative smart materials that has recently gained attraction in many medical, industrial and biomimetic fields, especially for micro/nano underwater applications. It can achieve a large deflection under a relatively low driving voltage and also has the features of light weight, agile, noiseless and flexible. However, the performance of this material is significantly affected by its inherent creep behaviour and uncertainties due to internal and external factors such as working environment. These limitations impose challenges for using IPMC as actuators in precise tracking applications. Therefore, this paper proposes a robust tracking control for the IPMC actuator using nonsingular terminal sliding mode (NTSM) to improve the tracking performance. The proposed controller was designed based on an identified model of the IPMC when it is working in water. Experimental investigations demonstrate the efficiency of the designed controller in terms of robustness, tracking accuracy and disturbance rejection.

تم قبول بحثي الخاص بتصميم مسيطر متين لمشغل IPMC تحت الماء دون الاعتماد على الموديل الرياضي للمادة الذكية IPMC في المؤتمر الدولي للسيطرة الثامن والثلاثين والذي يقام في الصين لعام 2019