For robotic systems that use on/off (solenoid) pneumatic actuators, a sliding mode control law for precise position control and low switching (open-close) activity of the valves is presented in this paper. Given a pneumatic actuator with two chambers and four solenoid valves, there are sixteen possible input combinations defined directly from the state of the four on/off valves present in the system; however, only seven of these discrete operating modes are considered both functional and unique. Therefore, we introduce a novel seven-mode sliding controller that minimizes the position tracking error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closed-loop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator setup comprising of two chambers with four on/off valves.
We
describe herein, a general, efficient, and scalable process
to design magneto-responsive thermoplastic elastomer-based (nano)composites
that can be repeatedly healed in a few tens of seconds by triggering
polymer melting upon exposure to a high-frequency magnetic field.
Three series of composites loaded with 1–15 vol % of Fe3O4 nanoparticles, Fe nanoparticles, or Fe microparticles
were produced and characterized in depth with the aim to identify
the physical properties required for two applications: (1) material
healing, which we evaluate through the rewelding of precut samples
and subsequent tensile tests, and (2) surface smoothening of 3D-printed
objects, serving to remove superficial defects and improve their appearance.
The optimal formulation consisting of a composite reinforced with
5 vol % of Fe nanoparticles ensures a high ability to heat while keeping
a low viscosity in the molten state being ideal for polymer processing.
The development of steerable guide wire or catheter designs has been strongly limited by the lack of enabling actuator technologies. This paper presents the properties of an electrostrive actuator technology for steerable actuation. By carefully tailoring material properties and the actuator design, which can be integrated in devices, this technology should realistically make it possible to obtain a steerable guide wire design with considerable latitude. Electromechanical characteristics are described, and their impact on a steerable design is discussed.
This work aims at providing a complete analysis of the effect of plasticizers on the electrostrictive terpolymer performance. To achieve this, several plasticizing agents such as 2-ethylhexyl phtalate (DEHP), diisononyl phtalate (DINP), and palamoll 652 have been incorporated in the polymer matrix. Experimental results demonstrate that the proposed novel materials exhibited excellent electromechanical enhancement in terms of transverse strain and mechanical energy density under a moderate electric field, which is definitively critical in recent microscale actuation. Another objective of this article was to explore material characteristics as a function of the DINP content, and it was found that the plasticizer weigh fraction was the key parameter determining performance of the modified fluorinate terpolymer blends. Accordingly, it was revealed that high performance flexible actuators can be achieved merely by employing a simple and cheap plasticizer, thus making it possible to overcome the current technological barrier of conventional electroactive polymers that suffer from the high applied electric field usually required to reach sufficient strain.
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