Design And Kinematic Characteristics Analysis Of The Imitated Crab Walking Structure

With the continuous development of modern technology culture, the research on the moving mechanisms of the various forms of motion has become a hot topic in the developed countries. The research of bionic walking mechanism has the great significance for the development of walking mechanisms on complex terrain. Compared with wheeled, crawler mechanism, walking mechanism has the good trafficability and adaptability to the complex terrain, so that it can play a better role in the extreme environment. That’s why it is widely used in disaster rescue, and military reconnaissance, deep space exploration, transportation and other fields. There are many animals in nature with outstanding athletic ability, which can come and go freely in a variety of complex environments. Researchers around the world hope they can find the successful physical mechanisms of the biological system and control mechanism, and apply it to the walking mechanisms, in order to improve the motion performance of the walking mechanisms.This study is based on Chinese mitten crab which lived in the soft ground. According to the characteristics of unstructured ground, combining with the analysis of the gait characteristics and the motion performance of the Chinese mitten crab, and using bionics principle, this paper make a research about the walking mechanism which adapt to unconventional ground environment, aiming at improving the trafficability and stability of the walking mechanism. Based on the observation and analysis of the walking characteristics of the Chinese mitten crab in different ground and state, combining the characteristics of the physiological structure of the Eriocheir sinensis, starting from simplifying structure and controlling system, a six legged bionic walking mechanisms with superior performance and simple structure is developed by imitating the walking way of the Eriocheir sinensis. At the same time, the paper also make some research on the motion characteristics of bionic walking mechanisms. The paper mainly carries on the following several aspects of work:(1) Analyzing the movement characteristics of the single foot of the Chinese mitten crab, and combining with the end trajectory characteristics of the rod mechanism, the study put out several feasible leg mechanisms of walking mechanism. In addition, the study ultimately select a six-bar linkage mechanisms as the leg structure of the walking mechanisms by simulation analysis of the single leg mechanisms, which is carried out in the multi-body dynamics software ADAMS.(2) Removing the two foot in the front of the crab which is not involved in walking, basing on the kinetic characteristic of the two pereiopod in the end of the crab, the walking mechanism is simply designed into six foot type, and the leg movement is realized by six link mechanism. Because the crab body is symmetrical structure, in this study, six feet are evenly distributed to the both sides of the body,and is drived by DC motor. Based on this, the whole mechanisms was built using three-dimensional modeling software CATIA.(3) Motion simulation video is obtained by ADAMS, and then using the 2D / 3D motion analysis system Simi motion to analyze the motion picture of the walking mechanism frame by frame, In a full cycle, the support phase and swing phase and the load factor of each leg of the walking mechanism are obtained. Compared with the gait sequence diagram of the Eriocheir sinensis in the smooth hard road surface, results show that the the two have very high similarity, and the similarity is 75% while the fourth pairs of feet(L4, R4) are removed.(4) The bionic crab walking mechanisms is produced, which was is tested under load. The results show that the walking mechanism can walk normally in 5.5kg iron load conditions, In order to get the walking characteristics of the bionic crab walking mechanism, comparing the walking mechanism with wheeled vehicle model on different roughness ground and using the motion image processing software Simi motion to complete the test data processing, the results reflect that The bionic walking mechanism has strong adaptability to different terrain, and has good performance on the large roughness hard ground(Ra=4.54) and loose dry sand ground(Ra=2.10).On the rough ground involved in agricultural production activities, the bionic walking mechanism is better than the wheeled model car. The kinematic parameters of the bionic walking mechanism are very close to the wheeled model car along the X axis in the small rough hard ground. Compared with the wheeled model car, the maximum fluctuation range and the absolute maximum value of acceleration of the bionic walking mechanism decrease by 5% and 7% respectively. Along the direction of the Z axis, the difference is bigger, the maximum fluctuation range and the maximum acceleration rate of the bionic crab walking mechanism are decreased 75% and 26% respectively compared to the wheeled car model.(5) By changing the size of the leg members of the bionic crab walking mechanism, the running smoothness of the walking mechanisms is improved. This paper attain the optimal leg member dimensions by using CATIA to establish a different leg bar size of the bionic crab walking mechanism, completing the kinematics simulation in ADAMS, exporting each leg joint displacement and angle data of the bionic crab walking mechanisms, and calculating the volatility characteristic parameters of the feature points, as GF=31.6mm, EF=36mm, EH=115mm.(6) It was conducted that comparative tests of the optimized imitated crab walking mechanism and the initial prototype in four species of ground, using 3D motion image analysis software Simi motion to analyze the motion video information, deriving kinematic parameters and calculating each performance index and the value of the objective function. The results show that the objective function value of the optimized bionic crab walking mechanism is better than initial prototype in four kinds of ground, part of the objective function value is reduced more than 50%, Fully emboding the excellent performance of the optimized crab walking mechanism.