An electromagnetically actuated mesoscale ball and socket joint for applications in 3-D metrology and electrical characterization
Micro-robotics is concerned with development of robotic systems to manipulate micro-meter sized objects. To develop functional micro-robotic manipulators, it is necessary to develop joints that possess large motion range and move in a precise manner. This thesis is devoted to the design, evaluation and applications of an active meso-scale ball and socket joint that possesses these properties. The joint employs magnetic actuation for purposes of rotation of the ball. Dither-based excitation is employed during rotation to eliminate the effect of static friction. After rotation, the dither signal is switched off and the joint is firmly held in its new orientation. In the first part of the thesis, the design of the ball and socket joint would be described, followed by its dynamic modelling. The dynamic model is developed by taking into consideration the different magnetic and mechanical forces experienced by the ball. Subsequently, the overall model is employed to perform simulations that validate the feasibility of the proposed actuation strategy. The second part of the thesis discusses the fabrication and evaluation of the joint. In particular, the development of the joint and integration of a conductive tip to it would be first described. Subsequently, the experimental setup and measurement strategy for characterization of the ball’s rotation will be discussed. The experimental results demonstrate large rotation range, of about 70◦, for the joint with negligible hysteresis and low cross-axis rotation of about 8%. The third part of the thesis describes two applications of the developed ball and socket joint. In the first application, the joint was employed to develop a probe for a Coordinate Measurement Machine (CMM). The entire CMM system was also developed subsequently and employed for performing 3-D metrology. In particular, the instrument has been demonstrated to simultaneously access the vertical faces and the horizontal floor of a cuboidal corner and to reconstruct its geometry. In the second application, the electrically conductive nature of the tip of the CMM probe has been demonstrated to enable it to detect conductive surfaces. These results showcase the potential of the probe to be employed in 3-D Kelvin Probe Force Microscopy (KPFM).