Dielectric elastomer minimum energy structures (DEMES) can realize large angular deformations by small voltage-induced strains, which make them an attractive candidate for use as soft actuators. If the task only needs binary action, the bistable structure will be an efficient solution and can save energy because it requires only a very short duration of voltage to switch its state. To obtain bistable DEMES, a method to realize the two stable states of traditional DEMES is provided in this paper. Based on this, a type of symmetrical bistable DEMES is proposed, and the required actuation pulse duration is shorter than 0.1 s. When a suitable mass is attached to end of the DEMES, or two layers of dielectric elastomer are affixed to both sides of the primary frame, the DEMES can realize two stable states and can be switched by a suitable pulse duration. To calculate the required minimum pulse duration, a mathematical model is provided and validated by experiment.
The dielectric elastomer minimum energy structure (DEMES) can realize large angular deformations by a small voltage-induced strain of the dielectric elastomer (DE), so it is a suitable candidate to make a rotary joint for a soft robot. Dynamic analysis is necessary for some applications, but the dynamic response of DEMESs is difficult to model because of the complicated morphology and viscoelasticity of the DE film. In this paper, a method composed of theoretical analysis and experimental measurement is presented to model the dynamic response of a DEMES rotary joint under an alternating voltage. Based on measurements of equivalent driving force and damping of the DEMES, the model can be derived. Some experiments were carried out to validate the equivalent dynamic model. The maximum angle error between model and experiment is greater than ten degrees, but it is acceptable to predict angular velocity of the DEMES, therefore, it can be applied in feedforward-feedback compound control.
Microwaves have become a promising wireless driving strategy due to the advantages of transmissivity through obstacles, fast energy targeting, and selective heating. Although there are some studies on microwave powered artificial muscles based on different structures, the lack of studies on microwave control has limited the development of microwave‐driven (MWD) robots. Here, a far‐field MWD parallel robot controlled by adjusting energy distribution via changing the polarization direction of microwaves at 2.47 GHz is first reported. The parallel robot is based on three double‐layer bending actuators composed of wave‐absorbing sheets and bimetallic sheets, and it can implement circular and triangular path at a distance of 0.4 m under 700 W transmitting power. The thermal response rate of the actuator under microwaves is studied, and it is found that the electric‐field components can provide a faster thermal response at the optimal length of actuator than magnetic‐field components. The work of the parallel robot is demonstrated in an enclosed space composed of microwave‐transparent materials. This developed method demonstrates the multi‐degree‐of‐freedom controllability for robots using microwaves and offers potential solutions for some engineering cases, such as pipeline/reactors inspection and medical applications.
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