Effect of head swing motion on hydrodynamic performance of fishlike robot propulsion

This paper studies the effect of the head swing motion on the fishlike robot swimming performance numerically. Two critical parameters are employed in describing the kinematics of the head swing： the leading edge amplitude of the head and the trailing edge amplitude of the head. Three-dimensional Navier-Stokes equations are used to compute the viscous flow over the robot. The user-defined functions and the dynamic mesh technology are used to simulate the fishlike swimming with the head swing motion The results reveal that it is of great benefit for the fish to improve the thrust and also the propulsive efficiency by increasing the two amplitudes properly. Superior hydrodynamic performance can be achieved at the leading edge amplitudes of 0.05L （ L is the fish length） and the trailing edge amplitudes of 0.08L. The unsteady flow fields clearly indicate the evolution process of the flow structures along the swimming fish. Thrust-indicative flow structures with two pairs of pressure cores in a uniform mode are generated in the superior performance case with an appropriate head swing, rather than with one pair of pressure cores in the case of no head swing. The findings suggest that the swimming biological device design may improve its hydrodynamic performance through the head swing motion.

A Soft Robotic Fish Actuated by Artificial Muscle Modules(SoRoFAAM-1)

In this paper,we present the design,fabrication,locomotion and bionic analysis of a Soft Robotic Fish Actuated by Artificial Muscle(SoRoFAAM).As a carangiform swimmer,the most important part of SoRoFAAM-1,on the motion point of view,is its tail designed around a bidirectional flexible bending actuator by layered bonding technology.This actuator is made of two artificial muscle modules based on Shape Memory Alloy(SMA)wires.Each artificial muscle module has four independent SMA-wire channels and is therefore capable of producing four different actuations.This design allows us to implement an adaptive regulated control strategy based on resistance feedback of the SMA wires to prevent them from overheating.To improve the actuation frequency to 2 Hz and the heat-dissipation ratio by 60%,we developed a round-robin heating strategy.Furthermore,the thermomechanical model of actuator is built,and the thermal transformation is analysed.The relationships between the actuation parameters and SoRoFAAM-1’s kinematic parameters are analysed.The versatility of the actuator endows SoRoFAAM-1 with cruise straight and turning abilities.Moreover,SoRoFAAM-1 has a good bionic fidelity;in particular,a maneuverability of 0.15,a head swing factor of 0.38 and a Strouhal number of 0.61.

Design and development of a five-axis machine tool with high accuracy,stiffness and efficiency for aero-engine casing manufacturing

In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design,key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual drive swing head and a compact motorized spindle are designed with enough drive capability and stiffness, and related structure, assembly method, cooling technology, and performance simulation are given in detail. Next, a design method of supporting stiffness of guide is proposed through the deformation prediction of the spindle end. Based on above work, a prototype of machine tool is developed, and some experiments are carried out, including performance tests of swing head and motorized spindle, and machining of a simulated workpiece of aero-engine casing. All experimental results show that the machine tool has satisfactory accuracy, stiffness and efficiency, which meets the machining requirements of aero-engine casing. The main work can be used as references for engineers and technicians, which are meaningful in practice.