Research On Compliance Control Method Of Industrial Robot Surface Tracking

The compliance control of the contact force between the robot and the curved surface,has always been regarded as one of the important methods to improve the surface grinding and polishing quality of the robot.However,the current compliance control algorithms mainly rely on the past force feedback information to achieve,and it is difficult to compensate for future contour changes in time during the surface tracking process,which leads to sudden force changes and large force fluctuations.To solve above problems,an active compliance control method based on the prior knowledge of curved surfaces has been proposed,and the experiments has been executed.The results show that the method can effectively avoid the sudden change of the contact force under the convex/concave area,and the force variance is reduced by more than 50%.At the same time,a passive compliance device to assist the active compliance control algorithm has been designed.In the experiment,the compliant control method based on the combination of active and passive can effectively reduce the force fluctuation at the moment of contact and during the tracking process,and the amplitude of the force fluctuation is reduced by more than 40%.The main research contents and innovations of the paper are as follows.(1)A compliant control method for positional industrial robots based on impedance control is proposed.Firstly,a compliant contact model based on the impedance equation is established,and the mapping relationship between controlling velocity and contact force is established by solving the impedance equation.At the same time,in order to calculate the feeding velocity,an online pose generator is designed.Finally,the controlling velocity and the feeding velocity are converted into joint angle increments by using Jacobian matrix,so as to realize the compliant control of the positional industrial robot's surface tracking.(2)A compliant control method based on the correction of the controlling velocity,which is combined with the prior knowledge of the curved surface,is proposed.Firstly,the inclination angle of the priori contour of the curved surface is defined by the priori information point on the curved surface.Then the prior velocity is calculated by using the feeding velocity and the prior contour inclination.Finally,the velocity weight is defined to assign weights to the controlling velocity and the prior velocity,so as to realize the fusion of the prior knowledge of the surface and the compliance control algorithm.(3)In order to assist the active compliance control and reduce the fluctuation range of the contact force,a passive compliance device is designed,which is based on the far center compliance and the oblique wedge slider mechanism.The experimental show that the fluctuation range of the contact force is positively related to the overall elastic coefficient between the end tool and the force sensor,and the advantages of the combined active and passive compliance control are more obvious in areas where the curved surface is relatively flat.