Design And Research On A Compliant Leg Walking Platform With Series Elastic Actuators

Legged robot obtains support and traction force via discrete supporting points,so that it can actively or passively select the optimal position on the reachable surface to maximize its supporting and traction capacity,it has much higher adaptability than wheeled or tracked robots,and has been greatly developed in recent years.Legged robot's technical route can be divided into two types: open chain with multi-degree of freedom and close chain with few-degree of freedom.Close-chain leg mechanism with fewer degrees of freedom is of low adaptability,but the complexity of the control system is replaced by complex mechanism design,and high bearing capacity and high stiffness are obtained.Existing robots based on close-chain single degree-of-freedom leg mechanism still have shortcomings and defects which hinder their practical application and development.Including:(1)leg mechanism is subjected to impact load,(2)driving system is subjected to impact torque,(3)the movement speed of the whole machine fluctuates periodically.To deal with the above three problems,this thesis presents solutions from two aspects.Firstly,a new type of elastic leg mechanism is constructed based on planar closed-chain single-degree-of-freedom linkage mechanism to solve the problem of impact load on leg parts.Secondly,by introducing a series flexible drive spring,the problem of impact torque of the driving unit is solved,and at the same time,the speed fluctuation of the whole machine under high speed driving is improved.The main research contents of this thesis are as follows:(1)A Stephenson-I type elastic leg mechanism is proposed in the order of designing rigid mechanism first and then completing the elastic design.After type synthesis of rigid leg mechanism,the existence condition of six-link crank and the influence analysis of bar length are given,and the size optimization of the leg mechanism is carried out by manually selecting and optimization function solving.The elastic parameters are selected according to the influence of the length of the links in rigid mechanism.The virtual displacement principle is used to analyze the crank load and the relationship between the deformation of the elastic part and the force on the foot of the elastic leg mechanism.The software ADAMS^TM is used to analyze the influence of elasticization on quadruped module's walking performance,to complete the design of torsional spring stiffness,to analyze the leg changing phase of the closed-chain elastic leg mechanism in stationary gait,and to present the improvement measures.(2)The application of series flexible drive is analyzed and designed.The necessity of introducing series flexible drive is demonstrated.The ideal deformation of the flexible drive spring is calculated by interpolation,and the preliminary design of the flexible drive is completed.The effectiveness of the design is verified by simulation experiments.(3)The whole assembly of compliant leg carrying platform of series elastic actuators is designed,a prototype is developed.Complete leg-layer design and joint design,check the key parts,compile technical documents and project assembly steps,complete the assembly and experiment of the prototype,the feasibility of the design is designed.