Research On Robot Shaft Hole Precision Assembly Strategy And Compliance Control

At present,robots have been more and more widely used in industrial production,replacing or assisting workers to complete tasks with high risk,high labor intensity and poor working environment.For different tasks,robots are required to have high-precision position control,and should have the function of flexible interaction with external constraints.Aiming at the task of precision assembly of shaft and hole,the following research is carried out on robot trajectory planning,hole search strategy and compliance control method :Firstly,the shaft hole precision assembly system is built,and the trajectory planning of the robot shaft hole assembly task space is analyzed.The kinematics modeling and inverse kinematics simulation verification of the assembly robot are carried out by D-H method.The fifth-order polynomial interpolation method is used to interpolate the robot joint space trajectory planning to ensure the smoothness of the robot joint motion speed and acceleration.At the same time,the cubic B-spline curve is used to plan the Cartesian space end trajectory to improve the end jitter during the robot joint motion.Secondly,inspired by the characteristics of artificial assembly behavior,the robot shaft hole precision assembly process is divided into two stages : hole search stage and adjustment insertion stage.Based on the analysis of the conventional hole search strategy in the search phase,a tilted hole search strategy based on Archimedes spiral is proposed to achieve accurate alignment of shaft holes.For the adjustment insertion stage,the shaft hole assembly model is analyzed.According to the number of contact points,one-point contact and twopoint contact assembly models are established respectively,and the force analysis is carried out on the characteristics of each contact state,and the simulation analysis of the change of assembly force / torque in the process of simulating shaft hole assembly is carried out.Then,aiming at the zero drift of the force sensor and the influence of the tool gravity,the gravity compensation method based on the least square method is used to process the force sensing information,and the calibration of the force sensor is completed.An admittance control strategy based on equivalent mass-damping-spring is proposed.The compliance control experiment of robot shaft-hole assembly is carried out,and the feasibility of gravity compensation and admittance control method is verified.Finally,the experimental platform for the precision assembly task of the shaft hole is built,and the regular circular shaft hole is selected to carry out the robot assembly task experiment.Experiments show that the inclined hole search strategy based on Archimedes spiral can achieve accurate alignment of shaft holes,and the admittance control method can enable the robot to achieve compliant jack.