Research On Active Compliant Constant-force Control For Robotic Grinding

With the advancement of industrial robotic grinding technology,industrial robots are increasingly being utilized for automating the grinding process of small and medium-sized workpieces.However,this application faces several challenges,such as the inadequate adaptive adjustment ability of the robotic compliant constant-force grinding,and the influence of force fluctuations of non-linear system grinding on the expected force tracking effect.To address these problems,this paper studies the active compliance and constant-force grinding control of the robotic.The primary research objectives of this paper are as follows:A robotic force-controlled end-effector is designed to construct a closed-loop force control system,which can decouple the translational and rotational motions about the axial direction the axis of the end-effector.The effectiveness of the designed end-effector structure is verified through static,dynamic,and modal analyses using a finite element simulation platform.Meanwhile,the forward and inverse kinematics analysis of the robotic is completed,through an analysis of the homogeneous transformation matrix in space and the relative phase-attitude relationship between different coordinate systems.This part establishes the structural and kinematic theoretical basis for establishing and planning trajectories in the robotic grinding control system.A material removal function model for grinding operation is established to analyze the factors affecting the consistency of workpiece material removal rate and the response speed of the control system during robotic grinding operations,and the corresponding parameters of material removal depth of workpiece for constant-force grinding are taken.Meanwhile,the limitations of polynomial interpolation trajectory method and material removal characteristics in robotic grinding are analyzed,and the look-ahead interpolation trajectory planning of crosssection grinding trajectory is designed and completed.This part of the study lays the basis of the material removal theoretical model and the theoretical basis of trajectory planning for the proposal of compliance constant-force control method.A position-based impedance control model and an active disturbance rejection controller based on second-order nonlinear system are established.Meanwhile,the convergence and closed-loop stability of the active disturbance rejection controller are guaranteed by Lyapunov stability theory.For different grinding environments and demands,a robotic active disturbance rejection fuzzy variable impedance control method is proposed to address the influence of nonlinear system force fluctuations on the expected force tracking effect during grinding,and the large impact of dynamic changes in grinding force on control accuracy.Meanwhile,a robotic active compliance constant-force control method with adaptive variable impedance is proposed to address the issue of insufficient adaptive regulation of robotic compliance constant-force grinding due to complex time-varying non-linear coupling and uncertain disturbance in the process of robotic grinding.A robotic grinding system virtual prototype joint simulation platform is established.Static and dynamic expected grinding force tracking experiments and grinding force tracking experiments under different grinding conditions are carried out to verify the effectiveness of the proposed method.An experimental platform for robotic grinding is established.Comparison experiments of the robotic active disturbance rejection fuzzy variable impedance control method and the robotic active compliance constant-force control method,static and dynamic tracking experiments of desired grinding force,and displacement comparison experiments of endeffector grinding tool in stable grinding stage are carried out on the experimental platform of robotic grinding.The validity of the proposed methods is verified by experiments.This paper provides a beneficial exploration for compliance constant-force control of robotic grinding operations.