Ali Haddi Nasser Al-Ghanimi

Piezoelectric actuators (PEAs) are the key devices in micro/nano positioning system. However, the PEA performance is significantly degraded by the inherent non-linear behaviour. This behaviour is a consequence of the hysteresis properties contained within PEAs. Therefore, in micro/nano positioning applications, a robust control system has to be adopted for such actuators. This paper proposes a systematic control method that utilises a fast non-singular terminal sliding mode (FNTSM) based on online perturbation estimation technique for PEAs. Unlike other sliding mode methods, the FNTSM control method is characterised by chatter free. Besides, a zero error convergence can be guaranteed in finite time in the presence of disturbance and system uncertainties (i.e., hysteresis and gain changes). The design of the FNTSM control based on perturbation estimation (FNTSMPE) is presented. A model-free robust

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

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

This study proposes a non-linear saturation-aware controller for dual-stage micro–nano actuators. Dual-stage motion systems use two actuators in series in order to achieve an improved performance: a micro actuator responsible for a large range of actuation, and a nano actuator (NA) able to achieve a high bandwidth. The NA is commonly driven by flexure-based piezoelectric actuators subject to a limited range which presents large oscillations in the presence of output saturation. In order to avoid these oscillations, a non-linear smooth switching function that limits the actuation of the NA to only track references within its range is proposed. Experimental results demonstrate the effectiveness of the proposed approach, which is able to reduce oscillations and energy consumption without compromising settling time performance.

This paper proposes a discrete time terminal sliding mode with enhanced repetitive controller (DTSMERC) for nano-positioning system. The hybrid control structure incorporated the desirable features of enhanced repetitive control (ERC) and discrete terminal sliding mode control (DSMC) to accomplish a high precision performance for periodic reference tracking in the presence of system perturbation for PEA applications. The repetitive component is to cope with periodic error at steady state, hence, tracking of periodic reference signals can be improved. While, the DTSMC controller is design to speed up the settling time and achieve the baseline servo performance. In addition, the hysteresis effect is considered as an external disturbance. Moreover, the issue of non periodic disturbance amplification with conventional repetitive control (CRC) is considerably alleviated by adopting the ERC. The system stability is

Ionic Polymer Metal Composite (IPMC) actuators have recently attracted significant attentions in many industrial, medical and biomedical applications, especially for those that require an aqueous medium. IPMC actuators can produce a large deflection under a low driving voltage. Moreover, they are soft and flexible which make them suitable to be used to hold and pick up different species of tiny living objects or handle biological material. As a matter of fact, these tasks require accurate path tracking which motivates us to develop an IMPC tracking control system for its tip displacement to perform micro-positioning for underwater applications. In this paper, we carry out the modeling of the IPMC actuator under study and also design a simple but effective tracking controller for the IPMC to follow desired tracking profiles. Experiments were performed to verify the control design for the IPMC actuator and the results show …