Design And Application Research On Linkage-based Multi-legged Carrying Platform With Whole Close-chain Mechanism

With the development of mobile robot technology,the ground unmanned mobile platforms have become more and more important,and they are widely used in logistics transportation,exploder eliminating,patrol,surveillance and so on.Especially the various unstructured terrains raise a higher demand for performances of the legged mobile platform,such as:mobility,reliability,carrying capability and durability.From the aspect of close-chain linkage in mechanisms,this paper focuses on the six-bar close-chain legged mechanism as the basic configuration to exert the characteristics of less drive number,higher integral rigidity and higher rotation frequency.With the design of layered architecture,the universal whole close-chain walking module is established,and the multi-legged carrying platform is constructed to satisfy the functional requirements.The multi-legged carrying platform has advantage in the walking stability,system reliability,carrying capability and cruising ability.According to the motion characteristics of the dual-and quad-quadrupted walking systems,the applied researches of equine-assisted therapy and mountainous transportation are carried out.To solve the problem of the monotonous gait and trajectory,the reconfigurable hip joint(joint element)and gluteus maximus(link element)are designed and developed to realize the adaptive regulation and strong climbing ability,and the reconfigurable innovation design gives consideration to both the multi-feet stability and multi-legged mobility.The specific research content is as follows:(1)The design procedure of whole close-chain multi-legged system is proposed.The layered architecture is proposed and described,which includes:close-chain single-leg mechanism,full close-chain dual-leg unit,whole close-chain walking module and multi-legged load-carrying platform.The creative designs of(6,7)type,(8,10)type and(10,13)type leg mechanism are presented,especially the design atlas of(6,7)type leg mechanism is presented as the configuration basis of this paper.With the analysis of development tendency and requirements of ground unmanned mobile platforms,the structures,properties,functions and applications of the walking system are described on the basis of the proposed whole close-chain walking module.(2)Full close-chain dual-leg unit and whole close-chain walking module are designed and developed.Based on the solution of movement parameters in vector loops,the characteristic analysis,trajectory comparison and requirements analysis of the full close-chain dual-leg unit are performed,and the loop parameters of leg mechanism are optimized and verified in the dynamic simulations.Whole close-chain leg mechanism is further constructed by integrating the non-bridging component,and the motion sequence,duty ratio and pitch attitude are adjustable through the phase configuration.In terms of the unit and module,the human-machine synergistic assisted platform is put forward for injured/material transport based on the dual-leg unit,and the quad-leg module itself can walk steadily by adding the folding wings.(3)The dual-and quad-quadrupted walking systems are constructed and analyzed.According to the locomotion characteristics and application requirements,two kinds of the multi-legged load-carrying platforms can be developed:the equine-assisted therapy platform("Hygieia horse")and the mountainous load-carrying platform("Iron horse")."Hygieia horse" based on dual-quadrupted walking systems can realize both the rehabilitation and transportation.With the established mathematic model,the form-position inversion method is used for the fluctuation analysis of the riding platform.Different fluctuation amplitudes canbe adjusted through the parameters variation."Iron horse"based on quad-quadrupted walking systems can realize material transportation and support in mountainous environment to exert the advantage of less motors and multiple supporting feet.The locomotive gait and mobility comparison are discussed with the platform structure.The prototypes of "Hygieia horse" and "Iron horse" are fabricated and constructed,including:walking system,control system,energy system and carrying system.(4)The close-chain leg mechanism with variable topologies is proposed.Two different walking modes(rotating mode and sliding mode)can be generated and switched through joint reconfiguration to give attention to the rapidity,smoothness and mobility.The kinematics of the single leg under two modes is analyzed using vector loop method,and the particular structure of the leg mechanism is designed with optimized parameters.The frame is designed with the integration of structure and function,and the transition between two modes is conducted by employing the special geometric constraints.On the basis of the joint codes and joint sequences,the topological states are represented with graphs and a matrix.In particular,to evaluate the crossing ability,this paper proposes the obstacle-surmounting probability.A series of dynamic walking simulations is conducted to support the obstacle-surmounting capability and mobility comparison.Experiments on prototypes of dual-quadruped walking system and single leg are performed to testify the prototype performance.(5)The reconfigurable close-chain leg mechanism with "gluteus maximus" is presented,and it can realize the efficient,continuous and large-scale adjustment of the trajectories.According to the sensitivity analysis and comparative analysis,the reconfigurable parameter is obtained.In terms of the whole vehicle,the reconfiguration assignments and strategies are analyzed to satisfy the different climbing requirements.With the development of "Iron Horse",the walking,steering and carrying experiments are conduced to verify the fundamental performances.Furthermore,the walking experiments in complicated environment are performed to testify the terrain adaptability and the obstacle-surmounting capability of the sixteen-legged platform.