Robotic fish. Picture credit score: Tsam Lung You
The robotic fish was fitted with a twisted and coiled polymer (TCP) to drive it ahead, a lightweight low value system that depends on temperature change to generate motion, which additionally limits its pace.
A TCP works by contracting like muscle groups when heated, changing the power into mechanical movement. The TCP used on this work is warmed by Joule heating – the go of present by {an electrical} conductor produces thermal power and heats up the conductor. By minimising the gap between the TCP on one aspect of the robotic fish and the spring on the opposite, this prompts the fin on the rear, enabling the robotic fish to succeed in new speeds. The undulating flapping of its rear fin was measured at a frequency of 2Hz, two waves per second. The frequency of the electrical present is identical because the frequency of tail flap.
The findings, printed on the sixth IEEE-RAS Worldwide Convention on Gentle Robotics (RoboSoft 2023), present a brand new path to elevating the actuation – the motion of inflicting a machine or system to function – frequency of TCPs by thermomechanical design and exhibits the potential for utilizing TCPs at excessive frequency in aqueous environments.
Lead writer Tsam Lung You from Bristol’s Department of Engineering Mathematics stated: “Twisted and coiled polymer (TCP) actuator is a promising novel actuator, exhibiting enticing properties of sunshine weight, low-cost excessive power density and easy fabrication course of.
“They are often constructed from very simply assessable supplies equivalent to a fishing line they usually contract and supply linear actuation when heated up. Nevertheless, due to the time wanted for warmth dissipation in the course of the rest section, this makes them gradual.”
By optimising the structural design of the TCP-spring antagonistic muscle pair and bringing their anchor factors nearer collectively, it allowed the posterior fin to swing at a bigger angle for a similar quantity of TCP actuation.
Antagonistic muscle groups. Picture credit score: Tsam Lung You
Though this requires larger drive, TCP is a robust actuator with excessive work power density, and continues to be capable of drive the fin.
Till now, TCPs have been largely used for functions equivalent to wearable units and robotic fingers. This work opens up extra areas of software the place TCP can be utilized, equivalent to marine robots for underwater exploration and monitoring.
Tsam Lung You added: “Our robotic fish swam on the quickest actuation frequency present in an actual TCP software and likewise the very best locomotion pace of a TCP software thus far.
“That is actually thrilling because it opens up extra alternatives of TCP software in numerous areas.”
The crew now plan to increase the size and develop a knifefish-inspired TCP-driven ribbon fin robotic that may swim agilely in water.
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