Gait Planning And Stability Analysis Of Hexapod Robot With Rotatable Trunk

Legged robots are characterized by scattered landing sites,strong fault-tolerance and varied terrain adaptation.Hexapod robots have gradually become a hot topic in the research of legged robots because of their good stability and more explosibility of trunk,legs and foot structures.Most traditional hexapod robots adopt rigid bodies,while from the nature,hexapods generally have segmented bodies that can move independently,which can be used to realize a series of movements,such as running,rotating,jumping and climbing.The forms of movement include pitching movement,twisting movement and pitching torsion mixed movement.Inspired by this phenomenon,this paper proposes a hexapod robot with autonomous movement of the torso,and builds an experimental platform to study the basic problems of kinematics,gait and stability of the robot in the process of movement.At the same time,the influence of the movable torso on the robot movement is considered.The main content is divided into the following four aspects.Firstly,starting from the movement behavior of hexapods,based on the principle of bionics,the movement form is summarized,and a three-dimensional model of a hexapod robot with movable torso is designed.Based on D-H kinematics analysis method and vector kinematics modeling method,two kinds of forward and inverse kinematics solution expressions were established respectively.Based on the vector modeling,the influence of the segment structure on the stride length was analyzed,and the relationship between the maximum stride length and the Angle of the movable trunk was given.The leg lifting height is calculated based on the single leg swing cyclotron theory.On the basis of D-H kinematics,the trajectory planning and optimization of the foot motion curve were carried out,and the relationship between the robot foot motion curve and the joint Angle was established.The MATLAB numerical calculation results were compared with the ADAMS dynamic simulation to verify its correctness.Secondly,the gait planning of hexapod robot with movable trunk is studied.Firstly,three basic motion forms are simulated by ADAMS software to verify the reliability of the structure design.Aiming at steering gait and fault-tolerant gait,the two degrees of freedom of rotation of the trunk were used to design the motion mode,and the superiority of the motion over the rigid trunk was obtained through simulation.Thirdly,the stability of hexapod robot with movable trunk is studied.The stability determination problem of the robot is studied when the robot is moving fast,slow and carrying objects.Based on the zero moment point method,considering the gravity,heavy moment,inertia force and inertia moment of each leg of the robot,the zero moment point of the robot body is calculated.The force of the robot in the slow state is simplified,and the relationship between the centroid projection and the supporting triangle is considered to analyze the static stability margin.By using the method of force-angle stabilization cone,considering the Angle between the combined force of gravity and inertia force and the supporting triangle,the robot carrying object state is analyzed.The influence of hip joint deflection Angle on the stability margin was studied,and the relationship between them was solved by cubic polynomial.ADAMS-MATLAB co-simulation was built based on the results of static stability margin,the state variables in the robot ADAMS motion simulation were extracted,and the visual simulation model of static stability margin was established by using SIMULINK simulation module in MATLAB to output the stability of the robot in the process of motion in real time.Finally,the control system of the movable torso hexapod robot is designed,and the physical prototype is built.The theory of gait planning and stability analysis in this paper are experimentally studied,and position data are obtained by attitude sensor to verify the correctness of theoretical analysis.