Research On Key Technologies Of Automatic Assembling For Segment Assembly Robot Used In Rectangular Shield

Due to high space utilization rate,rectangular shield is widely used in the tunnel construction where the underground space is limited.As an important tool of shield machine,segment assembly robot plays a vital role in the quality and efficiency of shield construction.Serial robot 2P5 R is a new type of robot applied to segment assembly in rectangular shield construction.In this paper,researches on kinematics,trajectory planning,motion control and experimental test of the new robot are conducted.These provide theoretical basis and technical support for achieving a fast and smooth automatic segment assembly process.In kinematics,the transformation between actuator space and Cartesian space of this seven DOF robot is derived.The kinematics model of this robot is established by using the modified DH parameters.Then,the forward kinematics solution from the actuator space to the Cartesian space can be obtained.The end posture of the assembly robot is represented through the fixed angle parameters.Aiming at solving the kinematic redundancy problem,two different motion modes,i.e.,rotary mode and translation mode,are proposed,and the corresponding inverse kinematics solutions are deduced.Finally,the construction scope of this robot is determined by analyzing its workspace.In trajectory planning,a safe and smooth trajectory planning method is presented.Line laser sensors are utilized to detect segment grasping pose and assembly pose.The corresponding algorithm and its accuracy are also given.Based on contour key points,the optimization model of the space allowance is established to calculate the safe and collision-avoidance path.Different safe paths are planned for the segment grasping,segment delivering and segment assembly.The smooth path is interpolated with Bspline curve,and the path time rate is optimized by cycloidal velocity profile.On this basis,safe and smooth trajectories are obtained.In motion control,the dynamics model including hydraulic system and multibody of the robot is established.Traditional PID and velocity acceleration feedforward PID(FFPID)are adopted for the motion control simulation of the dynamics model,and results show that FFPID has better performance of trajectory tracking.A control scheme based on contour error compensation is proposed,and the end contour deviation is converted to the compensation in actuator space by Jacobin matrix.Simulation results show that the proposed control algorithm can effectively weaken the vibration and eliminate the motion deviation.In experiment,the RMC controller of American Delta Company is employed to build the motion control system of segment assembly robot.all The control modes of single motion,multi-axis motion and trajectory tracking are implemented.Experiments are conducted to verify the trajectory tracking control and contour error compensation control method,which show that the motion accuracy of the robot meets the requirements.