Research On Industrial Robot Grinding Based On Force Control

With the development of manufacturing industry, the market demand continues to growfor grinding process. In traditional grinding process, labor-grinding is time-consuming andlaborious, harmful to worker’s physical and mental health, and greatly depended on worker’sskill and experience. Compared to robotic grinding, a grinding machine’s workspace,machinable workpiece range and flexible upgrade space is relatively smaller. Besides, agrinding machine is more expensive. Therefore, the use of industrial robots for grindingoperation is an important alternative in manufacturing industry. In constant force grindingmanner, the quality of grinding depends largely on the level of the stability of normal grindingforce. Therefore, this paper studied the control strategies of industrial robot grinding underconstant force.Firstly, this paper modifys the playback method of RB086-DOF industrial robot,presents a method of adjusting the end-effector’s trajectory. By defining the adjustingdisplacement or adjusting velocity for each coarse interpolation points obtained by teachmode, this method can calculate the desired pose matrix and joint angle. This method makes afoundation of the realization of grinding control strategies.After that, this paper analyses and processes the force/torque information acquisited byforce sensor. After static calibration of the measuring force/torque signal, the zero shift of thesignal is eliminated and the linear relationship between the voltage signal and the force/torque amplitude is determined. Using the gravity force/torque compensation algorithm, theinfluence of the tool gravity is decreased. By the filtering processing method, the effectof noise on the measured values is diminished and stable signals are obtained.Then, this paper analyses the contact transition control problem when robot moving fromfree space to constrained space, puts forward a segmented deceleration strategy suitable forposition-controlled mode industrial robot. The rigid deformation of robot grinding processsystem is analyzed and classified into two types: rigid deformation of robot body and forcesensor–tool deformation. The theoretical derivation and compensation method ofdeformation are conducted.Finally, the mechanism and characteristics of grinding are summarized and analyzed. Based on the analysis of grinding force measurement, the method of estimating the contournormal direction is proposed and verified. The hybrid force/position control strategies forgrinding and its implementation on industrial robot are proposed. Force control method arevalidated by simulation and experiments. To overcome the difficulty to adjust the controlparameters, fuzzy adaptive adjusting method is adopted. The simulation and experimentsshow the effectiveness of the fuzzy adaptive adjusting method.