A traveling wave fitting method for robotic fish with a multi-joint caudal fin

Aimed at the carangidae robotic fish with a multi-joint caudal fin, a circle threshold interval discretion (CTID) method is proposed to fit the traveling wave of the fish body. Firstly, a circle is established by using the known length of tail joint as a radius, and there is a intersection point between the circle and the traveling wave of fish body. Then, the values of error equation are respectively calculated by sampling a threshold interval which is close to the intersection point. As a result, a coordinate would be obtained at the point of the minimum value of error equation, thus the traveling wave could be perfectly fitted at one moment. Finally, all joints are fitted for a whole swing period by adopting this type of method. Simulation images show the fitting method could get perfect fitting effect, and it would improve the propulsion efficiency of robotic fish.