The Analysis Of Locomotion Mechanism And Research On Kinematics And Dynamics In Chinese Mitten Crab (eriocheir Sinensis Milne-edwards)

The bionic robots are widely used in safeguard health, military reconnaissance, deepspace exploration, transportation and so on. The inspiration of manufacturing new robotscomes from natural field, which is the foundation of bionic research process. Chinese mittencrab (Eriocheir sinensis Milne-Edwards), as a topic arthropod, has excellent capability oflocomotion, because they can travel from inland to seaside for reproduction or migration.Therefore, Chinese mitten crab has a well adaption to complex terrain environment andshows triphibian features. The studies of Chinese mitten crab’s habits and characteristics canoffer the bionic prototype and theory foundation to manufacturing bionic crab-like robot ormoblile platform. Moreover, Chinese mitten crab is expert in excavating hole for habitationwith its two chelas, which can offer a new insight into the design and improvement onexcavating meachinery and bionic theories for manufacturing bionic excavating robots.In order to define the roughness of tested terrains quantitative, we used a distance lasersensor to measure the morphology of digital surfaces of six particle sizes of quartz sandpaved in the pint-sized soil bin flatly. And then the filtered data was converted with FFT fordrawing curves of space discrete power spectral density (PSD). The statistical results showedthat there were good correlations between the peak estimate of space discrete PSD, the areaof curves of space discrete PSD surrounded with frequency axis and the average particle sizeof quartz sand, which indicated that the energy terrains contained had good relationship withthe average quartz particle size of quartz sand. On the basis of average root mean-squaredheight RMS, we proposed terrain energy as a parameter for evaluating the terrain roughness.Experiments and analyzed results showed that terrain energy increased with the value ofRMS increasing. Therefore, it is reliable to use terrain energy to evaluate terrain energy.From the power function expression of space discrete PSD, we proposed another methodto evaluate terrain roughness by fitting the curves of space discrete PSD in double logarithmcoordinate system. Results showed that with the average particle size increasing, the slopesof fitting linear equations increased. From the relationship between terrain roughness andaverage root mean-squared height RMS, we can concluded that analyzing the relative positions of fitting linears and slopes for evaluating terrain roughness was dependable.By using a high speed3D video recording system, the video images of Chinese mittencrab moving on smooth terrain were recorded. The video images were analyzed using frameby frame method to analyze the gaits of Chinese mitten crab. The results showed thatChinese mitten crab used a metachronal wave pattern called alternating tetrapod. The dutyfactors of the rows of the leading legs were greater than those of the rows of the trailing legs,which indicated that the pulling period of the rows of the leading legs contacting with terrainwas longer than pushing period of the rows of the trailing legs. The stride frequencyincreased with the average velocity. The video images were analyzed with a3D motionanalysis system in order to obtain the kinematic parameters of the center of mass of Chinesemitten crab. The results indicated that the average velocity of Chinese mitten crab decreasedwith the mass of Chinese mitten crab increasing, and these results were consisted with ghostcrab moving on treadmill. Chinese mitten crab used a bouncing gait as the mainenergy-conserving and-releasing pattern of mechanical energy. Besides, they occasionallyused inverted pendulum gait. The percentage recovery of Chinese mitten crab was lowerthan that of ghost crab (Ocypode quadrata,55%~70%) and different from death-headcockroach (Blaberus discoidalis, the mean value is15.7%), did not vary as a function ofaverage velocity. The mass-specific rate of mechanical power increased with averagevelocity increasing linearly. On the basis of Heglund’s experimental equation, we deducedanother equation about the relationship between the mass-specific rate of total mechanicalpower and average velocity through introducing the mass-specific rate of total mechanical ofChinese mitten crab. The mass-specific rate of horizontal kinetic power was the maincomponent of the mass-specific rate of total kinetic power required to accelerate Chinesemitten crab. The mass-specific of gravitational potential power was the main component ofthe mass-specific rate of total mechanical power required to lift Chinese mitten crab.Motion video images of Chinese mitten crab locomotion on five types of terrains(including one smooth terrain and four kinds of rough terrains) were recorded. Frame byframe analysis indicated that Chinese mitten crab used random gaits instead of thealternating tetrapod gait with the terrain roughness increasing. The duty factors of the rowsof the leading legs were greater than those of the rows of the trailing legs, which meant thatthe pulling period of the rows of the leading legs contacting with terrain was longer than thepushing period of the rows of the trailing legs. The duty factors of the rows of the leadinglegs were almost the same for all terrains, and those of the rows of the trailing legs weregreater over the four types of rough terrains than over smooth terrain. For all five kinds ofterrains, the duty factors of L-2leg and L-3leg were greater than those of T-2leg and T-3leg, which indicated L-2leg and L-3leg produced pulling force and were used to explore thesituation of terrain. When moving on four kinds of rough terrains, the average velocity ofChinese mitten crab was less than that of moving on smooth terrain. When Chinese mittencrabs over four kinds of rough terrains, with the body mass of crabs less than about61.99g,the average velocity decreased with the body mass of crabs increasing, however, with thebody mass of crabs more than about61.99g, the average velocity increased with the bodymass of crabs increased. Chinese mitten crab used two fundamental gaits to save mechanicalenergy: the inverted pendulum gait and the bouncing gait. The bouncing gait was the mainpattern of mechanical energy conservation, however, in order to adapt to complex terrains,Chinese mitten crab occasionally used inverted pendulum gait. Horizontal kinetic energywas the major component of total kinetic energy for all terrains. Thus, horizontal kineticenergy can determine the trend of undulation in total kinetic energy. Gravitational potentialenergy was the major component of total mechanical energy, which determined the trend ofthe undulation in total mechanical energy. The mass-specific rate of total mechanical powerincreased with average velocity increasing linearly. The mass-specific rates of energyconsumption increased with the mass-specific rate of total mechanical power increasing,which indicated that the mechanical energy came from the energy metabolism produced.Besides, we investigated the structures of Chinese mitten crab with the methods ofmorphology. The statistical results indicated that the mass and length of segments of Chinesemitten crab had an increasing relationship with body mass. For chelas, the chiopodite masswas minimum and the chela mass was maximum. The basipodite length was minimum andthe chela length was maximum. For legs, the dactylopodite mass was minimum and themetropodite mass was maximum. The basipodite length was minimum and the metropoditelength was maximum. Paired t-test showed that the structure of Chinese mitten crab had asymmetrical structure.We developed the simple physical models and calculated the moment of inertia of eachsegment of chelas, legs and trunk. The calculated results of the moment of inertia showedthat the moment of inertia of basipodite of chela was minimum and chela was maximum.The moment of inertia of metropodites of L-2leg and L-3leg was greater than that of L-1leg and L-4leg respectively and there were no prominent different between the othersegments of L-2leg and L-3leg and the other segments of L-1leg and L-4leg. By referenceto the D-H method, we deduced kinematics and inverse kinematics equations. By referenceto the Lagrange method, we deduced the dynamics and inverse dynamics equations.