Abstract
This article presents the locomotion analysis and optimization of actinomorphic soft robots, which are composed of soft arms actuated by shape memory alloy wires. The soft arm that is a composite modular structure is actuated by a self-sensing feedback control strategy. A theoretical model was established to describe the deformation of the soft arm, combining the Euler–Bernoulli beam model of the soft arm with the constitutive model and the heat transfer model of the shape memory alloy wire. The kinematics of the actinomorphic soft robot was analyzed using the modified Denavit–Hartenberg method, and the motion equation of the actinomorphic soft robot was presented based on the quasi-static hypothesis. Results show that the actinomorphic soft robot moves with a zig-zag pattern. The locomotion of four actinomorphic soft robots with three to six arms was analyzed, and the gait parameters of each locomotion type were optimized. The optimization results indicate that the three-arm actinomorphic robot with certain gait parameters has the best performance and achieves a maximum stride length of 75 mm. A series of experiments were conducted to investigate the movement performance of the three-arm actinomorphic robot in various environments.
Highlights
Robots are employed in an extensive range of applications from manufacturing to domestic service
Three assumptions are made in the model: (i) the soft arm behaves as a Euler beam throughout the bending deformation, and its bending shape is approximated as a circular arc; (ii) the polyvinyl chloride (PVC) surface is the neutral plane of the soft arm, and the distance d between the shape memory alloy (SMA) wire as well as the PVC surface is constant during actuation; and (iii) the temperature variation of the PDMS is negligible if the heating time is short
These results indicate that the gait parameters affect the performance of actinomorphic soft robots with multiple arms
Summary
Robots are employed in an extensive range of applications from manufacturing to domestic service. A fluidic elastomer robotic snake has been developed to synthesize the interesting locomotion gait of snakes.[30] An inchworminspired robot has been designed to achieve both twoway linear and turning movement.[31] A turtle mimetic soft robot driven by flipper actuators has been proposed to produce distinct motions corresponding to different swimming gaits.[32] A miniature jellyfish-inspired robot can achieve a diversity of propulsion modes using jet propulsion.[33] In the biological locomotion field, symmetry is one of the typical features, such as the bilateria and the radiata Among these creatures, the radiata (e.g. brittle star and starfish) achieves a high mobility for the radial symmetry of its body. A series of experiments were conducted on a three-arm actinomorphic soft robot to investigate its basic movements and performance in various environments
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