Research On Key Questions Of Bionic Mechanical Leg Based On The Stiffness Of TSLJCS Model

Considering that legged robots play an increasingly important role in the field of national security such as anti-terror and anti-explosion and people's livelihood like operations in mountainous regions,running speeds and payload capacity for legged robots have to be improved.However,there still exsits a considerable gap between the motion performance(running speeds and payload capacity)of animlas and the corresponding biological legged robots at present.One of the critical factors is strongly in relation to the distinct difference on mechanism action of their leg stiffness.Therefore,according to the biological research,this paper proposes the Two-Segment Leg with “J”-Curve Spring Model(TSLJCS model).Next,influence of the stiffness of the proposed model on running speeds and payload capacity is investigated.Finally,the motion performance of the mechanical leg based on the stiffness of TSLJCS model is discussed,and the controllability of the prototype stiffness is analyzed.This is to improve running speeds and payload capacity for legged robots and provide technical support and theoretical basis for the study of high performance mechanical leg.Firstly,this thesis analyzes the related research status and tendency,which contains the influence of mechanical leg stiffness and the stiffness of running models on the motion performance,respectively.Based on the current problem,Two-Segment Leg with “J”-Curve Spring Model(TSLJCS model)is presented.Mathematical formulation of the relationship between the virtual leg force and the virtual leg compression is established by using of the interpolation method.Moreover,TSLJCS model force-elongation curve is sensitive for nominal joint angle variations,but it is insensitive for the ratio of leg length variations.Secondly,a generalized SLIP model is constructed according to leg stiffness of SLIP(the Spring-Loaded Inverted Pendulum),TSL model(Two-Segment Leg model)and TSLJCS model,and its equation of motion and apex return map during a running period is established,respectively.Running speed-leg stiffness,running speed-landing angle and running speed-the stability region simulation model is constructed and analyzed,respectively;simulation results reveal that both the largest tolerated range of running speeds and the tolerated maximum running speed are found and both the tolerated range of landing angle and the stability region are the largest in the TSLJCS model,and TSLJCS model is the most insensitive for speed variation in all three models.It is suggested that TSLJCS model is more advantageous for high-speed running compared with the SLIP model and with the TSL model.Thirdly,in the generalized SLIP model,payload-leg stiffness and other simulation model is constructed and analyzed,respectively;in the TSLJCS model,the influence of reference stiffness,nominal joint angle,angle of attack and payload on fixed point are found.Simulation results reveal that TSLJCS model is the most insensitive for speed and payload variation in all three models.It is suggested that TSLJCS model is the most propitious for high-payload at high running speed in all three models.Finally,the force-length curve equation inspired by human leg stiffness is established.The motion performance of the mechanical leg inspired by human leg stiffness is analyzed,and its high running speeds and high payload capacity is verified.On the other hand,the prototype is designed;its operational principle,the kinetic equation and dynamic equation is constructed,respectively;the workspace of the foot is analyzed.The variable stiffness experiment of the mechanical leg is established,and the corresponding experiment is made.The experimental results reveal that the stiffness of the mechanical leg is variable during the stance phase,its variation trend is controllable,and its stiffness is controllable.