Research On Workpiece Positioning In Array Type Flexible Fixture And Industrial Robot Integrated System

Flexible fixtures and industrial robots are key equipment for flexible production lines.Integrating flexible fixtures with industrial robots can effectively reduce the cost of workpiece clamping and reduce production preparation time.However,the key to ensuring the quality of the integrated system is the workpiece accurate positioning.On the one hand,flexible fixture are required to accurately and reliably position the workpiece.On the other hand,the robot needs to accurately obtain the position and orientation of the workpiece.Therefore,this paper integrates the designed array type flexible fixture with the industrial robot,proposing the generation method of the reliable positioning scheme,establishing the model of the accuracy analysis of the positioning scheme,and gives the method of the relative position calibration of the robot and the workiece.The main contents of the study are as follows:1.The integration scheme of array type flexible fixture and industrial robot is discussed.An array type flexible fixture that used to surface positioning was developed,and the pneumatic system of the fixture was designed.The pneumatic system is controlled by the General-pur:pose signal of the robot.This can achieve clamping and relaxation of the workpiece.The mounting platform of robot was designed,the fixture was integrated witih the robot,and two different integration schemes were discussed,fixture in hand and fixture on side.2.The generation method and reliability analysis method of array type flexible fixture's positioning scheme are proposed.The projection method is used to transform the positioning problem of workpiece and array type flexible fixture into the positioning problem between planar graphics.The positioning pillar is regarded as the array point,and multiple groups of positioning schemes are generated through the inclusion relationship between the maximum projection surface of workpiece and the point.The mathematical model of positioning principle is established,and the process of judging the correctness of positioning is analyzed.The reliability analysis method of the positioning scheme is explained,and the reliability experiment of the positioning scheme was carried out for the melamine tableware plate model and the fruit plate cover model.3.The accuracy analysis model and calculation steps of flexible fixture positioning scheme are established.The transfer model of manufacturing errors of workpiece,installation and manufacturing errors of positioning elements to workpiece positioning errors is established.Based on the reliable positioning scheme,the positioning error is calculated,and the most accurate positioning scheme is selected according to the criterion of minimizing the maximum positioning deviation.Based on the reliable positioning scheme of melamine tableware plate and fruit plate cover,the accuracy experiment of the positioning scheme was carried out.4.The calibration method of the relative position of the robot and the workpiece is proposed.In the robot integrated system with the fixture on side,the calibration of the tool coordinate system was carried out according to the five-point method.Based on this,the calibration of the fixture coordinate system was carried out by using the three-point method.Then the calibration experiment of the tool coordinate system and the fixture coordinate system was carried out.Finally,the positioning accuracy of the workpiece was tested in the integrated systemIn this paper,an array type flexible fixtures is designed,and the scheme of integrating fixtures with industrial robots is discussed.The reliability and accuracy of the fixture positioning scheme were studied.The experiment shows that the fixture can accurately and reliably position the workpiece.Then,in the robot integrated system of the fixture on side,the tool and the fixture are jointly calibrated.The experiment shows that the robot can accurately obtain the position and orientation of the workpiece.