| With its non-full-time contact walking form,quadruped robots have better adaptability and stronger maneuverability than wheeled and tracked robots when facing non-continuous roads.Quadruped robots have better performance and stronger load capacity than bipedal robots.At the same time,compared with the multi-footed robot,its structure is simple and easy to control,which has become one of the current research hotspots.With the development of technology,when facing the rescue search environment or aerospace and other fields with narrow space,most robots with practical application values tend to have large masses,high energy consumption,and relatively small loads,which is difficult to meet the needs of work.In response to these requirements,this paper proposes a leg configuration based on a closed-chain five-bar mechanism.Based on this,a lightweight,low-inertia,low-energy-consumption,and large-load quadruped robot is designed.The specific research contents are as follows:(1)The single-leg configuration of the quadruped robot was designed and optimized.Designed a leg configuration based on a five-bar mechanism and selected the electric drive method,which focused the drive system on the fuselage to reduce the leg joint inertia,at the same time introduced a closed-chain mechanism to improve its load capacity.The method of combining virtual prototype and orthogonal experiment was used to analyze the influence of the length of each lever of the mechanism on the swing height and length of the leg,and the best matching combination was selected to increase the range of foot end motion.The lightweight design of the leg parts was integrated.The single-leg module was integrated into a four-legged robot with an overall mass of 1.876 kg.The projection on the horizontal plane was within the range of an A4 paper.(2)The mathematical model of the leg configuration was established and the performance analysis was performed.The algebraic method was used to establish its forward and inverse kinematics model,and the function mapping relationship between the driving angle input space and the foot end trajectory space was obtained.The Lagrangian equation of the open-chain mechanism was used in conjunction with the constraint equation of the hinge to obtain its dynamic model.Based on this,the mechanical performance,dexterity and singularity of the mechanism were analyzed,which showed that the mechanism had good load capacity and dexterity,at the same time got its high speed and dexterity range of motion and singularity,which provided theoretical basis for foot end trajectory planning and gait research.(3)The foot trajectory planning and gait research was conducted.Based on the established mathematical model,the sine trajectory,ellipse trajectory and improved compound cycloid trajectory planning were designed,and the appropriate initial attitude was selected to plan it within the range of the dexterous foot end.A single-leg virtual prototype was established and used to select the improved composite cycloid with the lowest energy consumption and the best speed performance as the foot end trajectory for diagonal gait research.A virtual prototype of the robot was established.The counterweight method was used to overcome the motion commutation.The overturning moment of the robot was verified by gait simulation that this method effectively improved the motion stability of the robot.(4)The physical prototype of the quadruped robot was processed and the single leg trajectory tracking experiment and gait experiment were carried out.A three-layer decision-coordination-execution control system was built.The rationality of the mechanism design and the effectiveness of the foot-end trajectory planning were verified by the single-leg trajectory tracking experiment.At the same time,the optimal PID control parameters were selected to conduct motion experiment of the overall robot,which verified the correctness of the gait planning?the effectiveness of the control system construction and the stability of the robot movement. |
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