Ionic polymer metal composites (IPMCs), a new kind of electro-active polymer, can be used for micro robotic actuators, artificial muscles and dynamic sensors. However, IPMC actuators have the major drawbacks of a low generative blocking force and dependence on a humid environment, which limit their further application. Multiple process parameters for the fabrication of IPMCs were optimized to produce a maximum blocking force; the parameters included reducing agent concentration, platinum salt concentration in the initial compositing process, and tetraethyl orthosilicate (TEOS) content. An orthogonal array method was designed and a series of fabrication experiments were carried out to identify the optimum process parameters. The results show that the platinum salt concentration in the initial compositing process plays the most significant role in improving the blocking force of IPMCs, the TEOS content plays an important role, and the reducing agent concentration has no apparent effect on the blocking force. In the optimized conditions, the IPMC actuator exhibited maximum blocking force of 50 mN, and the corresponding displacement was 14 mm. Compared with normal conditions, the blocking force improved 2.4-fold without sacrificing the displacement, and the effective air-operating life was prolonged 5.8-fold for the blocking force and 5-fold for the displacement. This study lays a solid foundation for further applications of IPMCs.
The study of the movement behavior of geckos on a vertical surface, including the measurement and recording of the reaction forces as they move in different directions, plays an important role in understanding the mechanics of the animals' locomotion. This study provides inspiration for the design of a control system for a bionics robot. The three-dimensional reaction forces of vertical surface-climbing geckos (Gekko gecko) were measured using a three-dimensional force-sensors-array. The behavior of gecko as it moved on a vertical surface was recorded with a high speed camera at 215 fps and the function of each foot of a gecko are discussed in this paper. The results showed that the gecko increased its velocity of movement mainly by increasing the stride frequency in the upward, downward and leftward direction and that the speed had no significant relationship to the attachment and detachment times. The feet above the center-of-mass play a key role in supporting the body, driving locomotion and balancing overturning etc. The movement behavior and foot function of geckos change correspondingly for different conditions, which results in safe and effective free vertical locomotion. This research will be helpful in designing gecko-like robots including the selection of gait planning and its control.
WANG ZhouYiWANG JinTongJI AiHongZHANG YueYunDAI ZhenDong
Because of their outstanding climbing and motor coordination ability, geckos have provided the basis for a peculiar bionic model leading to the development of a geckorobot. A three-dimensional locomotion observation system was constructed to measure angular orientations of joints while geckos trotted (337.1 mm/s) and walked (66.7 mm/s) on horizontal surfaces, and trotted (241.5mm/s) and walked (30.6mm/s) on vertical surfaces. Moving over horizontal surfaces, the joints rotated more quickly the greater the speed, and the swinging scope of forelimbs stayed nearly at 59 degrees when swinging forward, but extended from 72 degrees to 79.2 degrees when swinging backward. The lifting angle of forelimbs was always positive to keep the center of mass close to the surface when moving up vertical surfaces, the scope of the forward swinging forelimbs forward extended from 33.7 degrees to 36.7 degrees with increasing speed, while the scope of backward swinging forelimbs remained almost the same at 87.5 degrees. Alternative gaits had little effect on the swing angle of hindlimbs of the geckos moving on both horizontal and vertical surfaces.
LI HongKaiDAI ZhenDongSHI AiJuZHANG HaoSUN JiuRong
离子聚合物金属复合材料(Ionic Polymer Metal Composite)作为新型的电致动材料具有巨大的应用潜力。但就目前国内外研究结果显示,现有的IPMC电致动材料仍具有一个显著的的缺点:非水工作时间短。本文通过用离子液体1-乙基-3-甲基咪唑硫氰酸盐(EMImSCN)替代水作为IPMC中的溶剂,以此来提高IPMC的非水工作时间。实验结果表明:在4V正弦交流电压下,当IPMC在空气中作用时间延长至320s时,以水为介质的IPMC位移减小了93%,位移大小几乎为0,而以[EMIm]SCN为介质的IPMC位移减小了63%,并长期处于一个稳定的位移值不变。
