Soft actuators are a promising option for the advancing fields of human-machine interaction and dexterous robots in complex environments. Shape memory alloy wire actuators can be integrated into fiber rubber composites for highly deformable structures. For autonomous, closed-loop control of such systems, additional integrated sensors are necessary. In this work, a soft actuator is presented that incorporates fiber-based actuators and sensors to monitor both deformation and temperature. The soft actuator showed considerable deformation around two solid body joints, which was then compared to the sensor signals, and their correlation was analyzed. Both, the actuator as well as the sensor materials were processed by braiding and tailored fiber placement before molding with silicone rubber. Finally, the novel fiber-rubber composite material was used to implement closed-loop control of the actuator with a maximum error of 0.5°.

This paper develops the mathematical modeling and deflection control of a textile-reinforced composite integrated with shape memory actuators. The mathematical model of the system is derived using the identification method and an unstructured uncertainty approach. Based on this model and a robust stability analysis, a robust proportional–integral controller is designed for controlling the deflection of the composite. We showed that the robust controller depends significantly on the modeling of the uncertainty. The performance of the proposed controller is compared with a classical one through experimental analysis. Experimental results show that the proposed controller has a better performance as it reduces the overshoot and provide robustness to uncertainty. Due to the robust design, the controller also has a wide operating range, which is advantageous for practical applications.

This paper presents a penalty-based sliding mode control (SMC) law for flexible bar system, which uses shape memory alloy (SMA) as actuator. SMA actuators are lightweight, compact and flexible which facilitate their integration into flexible structures. The proposed control law manipulates SMA current to exert the necessary force for deflecting the flexible bar into the desired state. Numerical simulations demonstrate that this new method can control the one-input, multi-output under-actuated system of the flexible bar efficiently. The mathematical model of the flexible system is obtained using physical discretization. The bar is modeled as a combination of rigid rods connected by joints without elasticity and friction. This model demonstrates the flexibility of the system in an effective way. The numerical simulation illustrates the feasibility of the proposed model for analyzing the oscillations of the system and the effectivness of proposed control algorithms.

This contribution describes the position control of textile reinforced composites actuated by shape memory alloys. The system exhibits highly nonlinear behaviour including hysteresis due to the mechanical properties of the actuator. From experimental data and system identification an uncertainty model is derived. A classical controller based on the nominal model and a robust controller using the uncertainty model are designed. The performance of the controllers is examined experimentally.