Designing and Developing a 6-DOF Calibration Setup Based on the Gough-Stewart Platform Equipped by Potentiometer Sensors

This paper investigates the design and development of a novel 6 Degree-Of-Freedom parallel mechanism displacement sensor based on the Gough-Stewart platform with potentiometer sensors for calibration purposes. This platform is equipped by six potentiometer sensors which connect the fixed base to a moving plate, called the End-Effector (EE), in order to measure the displacement and rotation of its EE along the three Cartesian axes X, Y, and Z. Since the precision of the potentiometer is considerably high, thus this device can be used as a calibration setup to the end of calibrating other robots. The main objective of this paper consists in the design of a reliable calibration setup by investigating different architectures of the Gough-Stewart platform, workspace calculation, the manufacturing process, and the data acquisition circuit. In order to ensure the precision of the proposed setup, first a calibration procedure is carried out on one potentiometer which is done by a laser sensor which has a higher order of precision than the precision of the potentiometer. Then the EE of the setup is attached to a 3-DOF decoupled parallel robot, the so-called Tripteron robot, in order to actuate accurately the setup. Since three independent ball screws are used to actuate the Tripteron robot, thus the latter laser sensor is used separately to measure the displacement of each ball screw. Experimental results reveal that the mean Euclidean distance pose error in the EE of the designed calibration setup is 0.3886 mm, and the max Euclidean distance pose error became 0.6498 mm. Finally, it can be inferred that this setup is highly accurate in measuring displacement and can be attached to other robots to identify their kinematic parameters which is a definite asset in practice.