Vision-based micro-manipulations in simulation

Manipulating micro-objects is needed in various applications such as micro-assembly, minimally invasive surgery and micro-organism manipulation, which refers to micro-manipulation in this paper. During such operations, controlling the gripping force is mandatory, in order to prevent damage or the breaking of the micro-parts being grasped and handled, given that they are often very fragile. The force sensing is frequently carried out by sensors embedded in the micro-gripper, but this produces strong design and manufacturing constraints consequently. In this paper, vision-based manipulation of micro-parts is investigated. Moreover, instead of working with real setups, this paper investigates micro-manipulations carried out in simulation. Working on simulators instead of real setups allows to easily and quickly implement different vision-based force measurement methods, different force control strategies and even different micro-gripper systems. Using the simulators, we are also able to compare the performance and limitations achieved in each manipulation, and to study the impact of certain parameters on manipulation performance. MATLAB-based simulators were designed in this paper. A vision-based force measurement method was then implemented and integrated into a closed-loop force control. In the end, successful grasp-hold-release manipulations of micro-parts (400–600 µm size) were achieved with a force-sensing resolution of less than 6 µN. Moreover, the manipulation was observed to be successful when softness variation is introduced on the micro-object (± 20% around the average value), and when pictures are degraded because of noise and blur effects.