Abstract
In this paper, we applied the Taguchi method to evaluate the maximum swimming speed of a robotic fish under the limitation of the output of the motor. Four factors were considered in the optimization: the caudal-fin aspect ratio, the caudal fin stiffness, the oscillating frequency and the stiffness of the spring that transmits forces from the actuators to the foil. Because of the power limitations, the parameter's space was irregular. Since the Taguchi method requires a regular parameter space, we divided the parameter space into a regular space and the remaining irregular spaces. Within only 25 trials, the frequency and the spring stiffness were determined as the main factors in the regular space by the orthogonal design. Six more trials were carried out in the remaining irregular space with a higher frequency and spring stiffness. The fastest swimming speed of 870 mm/s, approximately 2.6 BL ( Body Lengths)/ s, was acquired, when the frequency reached 12 Hz and with infinite spring stiffness. This method is efficient for exploring the maximum locomotor capabilities of robotic fish and may also be useful for other robots as no modelling is required.
Highlights
After millions of years of evolution, fish are endowed with amazing locomotor capabilities in aquatic environments [1]
According to the classification and nomenclature proposed by Breder, fish swimming types are divided into two parts: body and/or caudal fin (BCF) propulsion and median and/or paired fin (MPF) movements
We considered four main factors that may determine the speed of our robotic fish: the shape of the caudal fin indicated by the aspect ratio Aspect Ratio (AR), the stiffness of the caudal fin defined by the diameter of the carbon rod D, the elastic flexibility of the spring connecting the joints k and the undulation frequency f
Summary
After millions of years of evolution, fish are endowed with amazing locomotor capabilities in aquatic environments [1]. Yu et al applied Particle Swarm Optimization (PSO) to find the highest backward swimming speed It will improve the efficiency if we can find the maximum locomotor capabilities with a few experiments [23]. The main contribution of this paper is our exploration of an efficiency method to evaluate the maximum swimming speed of robotic fish based on the Taguchi method. This method can be extended to find the loco‐ motor capabilities of various other robotic fish because it does not require modelling.
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