Development of an onsite calibration device for robot manipulators

A novel in-contact three-dimensional(3D)measuring device,called MultiCal,is proposed as a convenient,low-cost(less than US$5000),and robust facility for onsite kinematic calibration and online measurement of robot manipulator accuracy.The device hasμm-level accuracy and can be easily embedded in robot cells.During the calibration procedure,the robot manipulator first moves automatically to multiple end-effector orientations with its tool center point(TCP)constrained on a fixed point by a 3D displacement measuring device(single point constraint),and the corresponding joint angles are recorded.Then,the measuring device is precisely mounted at different positions using a well-designed fixture,and the above measurement process is repeated to implement a multi-point constraint.The relative mounting positions are accurately measured and used as prior information to improve calibration accuracy and robustness.The results of theoretical analysis indicate that MultiCal reduces calibration accuracy by 10%to 20%in contrast to traditional non-contact 3D or six-dimensional(6D)measuring devices(such as laser trackers)when subject to the same level of artificial measurement noise.The results of a calibration experiment conducted on a Staubli TX90 robot show that MultiCal has only 7%to 14%lower calibration accuracy compared to a measuring arm with a laser scanner,and 21%to 30%lower time efficiency compared to a 6D binocular vision measuring system,yielding maximum and mean absolute position errors of 0.831 mm and 0.339 mm,respectively.

Study on the Drift Calibration Method and Device for the Tin Oxide pH Electrode

Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabrication process to improve the properties of the front-ended device.Another is to compensate the drift phenomenon by adding extra drift compensation circuit or software in the back-ended readout circuit.In this study,a drift calibration method for the potentiometric sensor was presented and the drift calibration method was performed by using the circuit.According to experimental results,the drift phenomenon of the SnO_2 pH electrode was reduced by the drift calibration device.

Calibration and Application of Actual Tension of Low Precision 20 High Mill

The rolling production of metal thin strips,especially the production of stainless steel and copper thin strips with high yield strength,due to the limitation of the minimum rolling thickness,multi roll mills with small working roll diameter are mostly used,and the 20 roll mill is the most common.Aiming at the problem that the actual tension of some 20 high rolling mills with long service time and low assembly accuracy has a large deviation from the set tension and is not accurate enough,this paper first designs the tension calibration device of the low precision 20 high rolling mill.Secondly,the calibration principle of the tension calibration device designed in this paper is described.Then,according to the calibration principle and specific implementation scheme,the actual tension tact of the strip steel is comprehensively determined,and the mapping relationship between the set tension tset and the actual tension tact of the 20 high mill is established,so as to improve the tension control accuracy of the 20 high mill and ensure the shape quality of the strip steel.