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  1. Free, publicly-accessible full text available October 27, 2024
  2. Madden, John D. ; Anderson, Iain A. ; Shea, Herbert R. (Ed.)
    Wearable dielectric elastomer actuators (DEAs) have been greatly considered for development of biomedical devices. In particular, a DEA cuff device has the capability of minimizing venous system disorders that occur in the lower limbs such as orthostatic intolerance (OI) and deep-vein thrombosis which are a result of substantial blood pooling. Recent works have shown that DEAs could regulate and even enhance venous blood flow return. This wearable technology orders a new light, low-cost, compliant, and simple countermeasure which could be safely and comfortably worn that includes mobility. In addition, it may supplement or even provide an alternative solution to exercise and medication. This work presents the design, model, and characterization of the DEA cuff device design that is capable of generating significant pressure change. A rolled DEA strip was actuated over a simulated muscle-artery apparatus using a periodic voltage input, and fluid pressure change was directly observed. A force sensitive resistor sensor was used to achieve a more precise pressure measurement. Performance analysis was conducted through frequency response analysis. The results provide a framework for implementing dynamic modelling and control to allow various forms of actuation input. 
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  3. Dielectric elastomers (DEs) deform and change shape when an electric field is applied across them. They are flexible, resilient, lightweight, and durable and as such are suitable for use as soft actuators. In this paper a physics-based and control-oriented model is developed for a DE tubular actuator using a physics-lumped parameter modeling approach. The model derives from the nonlinear partial differential equations (PDE) which govern the nonlinear elasticity of the DE actuator and the ordinary differential equation (ODE) that governs the electrical dynamics of the DE actuator. With the boundary conditions for the tubular actuator, the nonlinear PDEs are numerically solved and a quasi-static nonlinear model is obtained and validated by experiments. The full nonlinear model is then linearized around an operating point with an analytically derived Hessian matrix. The analytically linearized model is validated by experiments. Proportional–Integral–Derivative (PID) and H∞ control are developed and implemented to perform position reference tracking of the DEA and the controllers’ performances are evaluated according to control energy and tracking error. 
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  4. Dielectric elastomers (DEs) are electro-active polymers that deform and change their shape when an electric field is applied across them. They are used as soft actuators since they are flexible, resilient, lightweight, and durable. Many models have been proposed to describe and capture the behavior of these actuators such as circuit representation, lumped parameter modeling, and physics-based modeling. In this paper, a hybrid between the physics and lumped parameter model is presented which is used to control the actuator. The focus of this paper is on a tubular dielectric elastomer actuator (DEA). The model proposed is validated with experimental data to evaluate its approximation to the physical actuator. The physics model offers the ability to describe how the material properties and actuator's geometry affect the dynamics and behavior of the actuator under different states. The lumped parameter model accounts for physical quantities that may not be fully expressed when formulating the physics-based equations. The discussed model performance is found to have an error less than 10% for the sinusoidal signals discussed. 
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  5. null (Ed.)
    Dielectric elastomer (DE) materials, a category of electroactive polymers, can be used to design actuators that are flexible, resilient, lightweight, and durable. However, due to the uncertainties in its actuation dynamics, DE actuators always rely on feedback control to perform accurate and safe operations. In this paper, a tubular dielectric elastomer actuator (DEA) with self-sensing capability is developed. It does not require external devices to measure displacement for feedback control. The displacement of the actuator is controlled using a proportional-integral controller with the capacitance measured at high probing frequency as the self-sensing mechanism component of the actuator. By superimposing actuation and probing voltage and applying them to the DE tube, the actuation voltage activates the movement of the DE tube and the probing voltage is used for self-sensing. Fast Fourier Transform (FFT) is then used to filter a given frequency of the probing current and voltage and then calculate the capacitance from the probing current and voltage during each time window. With the relationship between capacitance and displacement of the DE tube, the displacement output is estimated online and self-sensing without an external sensor is achieved. The self-sensing signal is then used as a feedback signal in a closed-loop design to follow a reference signal for tracking. The experimental results validate the self-sensing of the DE actuator in feedback control. 
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  6. In optical systems, reflectors are commonly used for directing light beams to desired directions. In this paper, a dielectric elastomer (DE) based optical manipulator is developed for two degrees-of-freedom (2-DOF) manipulation. The DE manipulator consists of a diaphragm with four segments that are controlled in two pairs, thus generating 2-DOF tilting motions. Due to its soft and gear-less moving structure, the DE manipulator is lightweight and naturally resistant to mechanical vibrations. Moreover, its nonelectromagnetic-driven mechanism allows it to work under the environments that are exposed to strong magnetic fields. To design a robust control strategy for the actuator, a physics-based and control-oriented nonlinear model is then developed and linearized around the equilibrium point. A feedback control system, which consists of two H-infinity controls, is developed to track two tilting angles along two axes. Experimental results have shown that this manipulator is able to track 0.3° 2-DOF tilting angle with 0.03° accuracy. 
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