Analysis And Design Of Quadruped Robot Mechanism Based On Serial-parallel Hybrid Mechanical Leg

At present,the mechanical legs of the quadruped robot mainly includes the series mechanism,the parallel mechanism,and the serial-parallel hybrid mechanism.The mechanical mechanism with the serial mechanism has many advantages,such as flexible movement and large movement space,but it also has the disadvantages of small bearing capacity and poor rigidity.The mechanical leg with the parallel mechanism has the advantage of large carrying capacity,but the movement flexibility is worse than the serial mechanism legs.The mechanical legs using the serial-parallel hybrid mechanism combine the advantages of the series and parallel mechanisms,and have been well developed,but the quadruped robot with strong carrying capacity and fast walking can be less.Therefore,the paper proposes a mechanical leg that can realize the fast walking and large carrying capacity of the serial-parallel hybrid mechanism,completes the design and research of the whole machine,and finally develops a quadruped robot prototype.The main contents of the paper are as follows:According to the type of quadruped,the overall layout and configuration of the quadruped robot are summarized,and the comparative analysis and selection are carried out to determine the degree of freedom and the mechanical form of the mechanical leg.A travel mechanism using a stroke amplifying mechanism as a mechanical leg is proposed,and a travel mechanism and a drive input layout are designed.Using the spiral theory,a variety of mechanical leg drive branches are constructed,and a plurality of mechanical leg configurations based on the stroke amplifying mechanism are synthesized.The complexity of the configuration manufacturing is used as the preferred criterion to determine the implementation of the mechanical leg mechanism.The position inverse solution equation of parallel stroke amplification mechanism is established.The velocity Jacobian matrix of parallel stroke amplification mechanism is derived,and the working space of mechanical leg is analyzed.The kinematics and static performance indexes of the parallel stroke amplification mechanism are defined,and the influence law of structural dimension parameters on performance indexes is revealed.Combined with the defined mechanism performance index,the multi-objective optimization method is used to determine the dimension parameters of the parallel stroke amplifier mechanism with better overall performance.The major dimension parameter is optimized for the side pendulum mechanism.The preliminary leg models are designed,which lays the foundation for the dynamic analysis of the robot.The inverse solution equation of the quadruped robot is established,and the inverse solution of the velocity and acceleration of the quadruped robot are derived.The dynamic equation of the legs of the quadruped robot is established by Lagrange method.The theoretical models of kinematics and dynamics of the quadruped robot are verified by simulation examples.Through the dynamics analysis,the influence law of the stride length on the driving force of the mechanical leg is revealed,which lays a foundation for the dynamic parameter estimates of the prototype.A variety of foot-end trajectories for meeting the requirements of mechanical leg walking are planned,and the kinematics characteristics of various foot trajectories are compared and analyzed.Based on the comprehensive consideration of the stability of the system,two kinds of good foot-end trajectories are selected.A new energy consumption index is proposed.The energy consumption of the quadruped robot under different gait parameters of the foot trajectory of spline function and modified cycloidal function is studied respectively,and the influence laws of different gait parameters on the energy consumption of the quadruped robot are revealed,which provides a reference for the energy-saving walking of the robot.In order to realize stable and continuous walking,a new method of center of gravity trajectory adjustment is proposed,and the walking gait of the robot is planned.The feasibility of the scheme is verified by an example simulation.The error model of parallel stroke amplification mechanism is established by using the whole differential theory,and the mapping relationship between each error source and the end position error is derived.The sensitivity model and evaluation index of the position error of the mechanism are established and the influence degree of each geometric error source on the end position accuracy is revealed.According to the3? principle and the sensitivity evaluation index,the manufacturing tolerances of the parts of each error source are determined.The actual component manufacturing error value is measured by a three-coordinate measuring instrument.The distribution of the end position accuracy in the working space is estimated according to the error model,and the correctness of the error model and the accuracy of the precision estimation are verified.The parameters of the hydraulic system are estimated and the structural dimensional parameters of the hydraulic cylinder are designed to lay a foundation for the implementation of the hydraulic system.The detailed design of the quadruped robot and the prototype are completed.