Electro-ionic soft actuators have the advantages of being possible to drive at low voltage and to operate in the air by using ionic liquid. However, they have a disadvantage of slow response. This paper proposes to accelerate electro-ionic soft actuators by feedforward control. Feedforward control can automatically generate online pulse-shaped input signals from any reference signals and is easy to implement. The experimental results show that the feedforward control can automatically generate control inputs for any references and achieve 2 times faster than the no-control case. In addition, it was found that the control performance was significantly degraded when a voltage limit was set to protect the actuator.
This paper discusses a time-domain analysis of the exact transfer function of Zhu’s multiphysics model of IPMC sensors. The authors recently derived the exact transfer function that describes the output voltage of Zhu’s IPMC sensor model. This paper shows that some time-domain constants such as the peak voltage and the steady-state voltage of a step response can be derived from the transfer function. It is shown that the values estimated from the exact transfer function agree with the numerical simulation in the time domain by COMSOL.
This study proposes a vibration excitation technique using a dielectric elastomer actuator (DEA) that can attach to a conductive structure based on an electro adhesion technique. Vibration responses of mechanical structures are experimentally analyzed to assess their mechanical characteristics. Conventionally, impulse hammers, heavy and rigid exciters, and lead zirconate titanate (PZT) actuators are applied to excite the vibration of the structure in a vibration experiment. However, the other vibration excitation technique should be applied for flexible structures with curved surface to evaluate their vibration response accurately without damages on them. Herein, a DEA can be applied to the vibration excitation taking advantage of its features of high flexibility, stretchability, and fast response. Conventional DEAs are attached to the target structures with adhesives degrading DEAs’ reusability. In this study, the electro adhesion technique, which can generate an attraction force were applied to the DEA. The proposed DEA can attach to the target without adhesives. The proposed DEA was fabricated by stacking layers that can generate the excitation force and that can generate the attraction force of the electro adhesion. Then, a vibration experiment for an aluminum pipe structure was conducted applying the DEA excitation. Finally, the effectiveness of the proposed vibration excitation technique was evaluated based on vibration responses of the target structure.
The quality of pear fruits is correlated with their firmness, which is assessed by a firmness index derived from the resonance frequency and mass. Postharvest pear fruits ripen during storage, which affects the firmness. A nondestructive measurement technique is necessary to predict fruit firmness without causing any damage. Thus, this study proposes a vibration experiment technique based on dielectric elastomer actuator (DEA) excitation to determine the resonance frequency of pear fruits without any damage. Therefore, DEAs can be attached directly on fruits with curved surfaces because of their stretchability, light weight, and responsiveness and can be used to transfer the excitation force effectively. For our experiments, thin laminated DEAs were fabricated to obtain sufficient vibration excitation force, and resonance frequencies of the pear fruits were confirmed. Subsequently, the firmness indices of each target fruit were calculated and assessed. Finally, the variations in firmness indices of pear fruits during storage were confirmed, and the effectiveness of the proposed technique was validated.
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