Haptic slave robot

Manual manipulation is presently the main method used in the assembly of small series of microproducts. However, human operators often lack the resolution in force application and positioning required by such tasks.

Tele-operated systems with force feedback become then a promising approach. The presence of the human operator gives flexibility to the system, the robotic actuators achieve the required resolution, and the haptic-feedback reduces the risk of damaging handled parts and limits the assembly time.  

This PhD project focuses on understanding how is it possible to support the human operator of such a system in order to improve his performance. Several operation modes are considered, spanning from semi-automation to full manual control, and including multimodal feedback channels (visual information, force feedback, auditory signals, etc.). System requirements are generated based on the intended operation mode, and on the constrains imposed both by the operator and the task. Following such requirements, two main hardware components of the slave system are being developed for this application.

Force sensing is a prerequisite of many force feedback schemes. Therefore, a silicon based 6DOF force and torque sensor was designed and fabricated. An asymmetric geometry was selected, leaving one side open for placing tools such as probes or micro grippers. Depending on the axis, the range of the sensor reaches 4 to 30mN in forces and 4 to 40 µNm in torques. Standard deviations up to 14 to 36 µN and 9 to 40 nNm have been observed in the measured data, respectively.

A second component been developed is the high resolution positioning stage. With the aim of minimizing play and achieving a resolution below the micrometer, designs based on flexures hinges and magnetic levitation have been considered. Additionally, the aforementioned principles can be operated with low stiffness or in direct force control, contributing to protect the fragile components and allowing for the implementation of different haptic teleoperation control schemes. Both designs have been optimized to cover a sub-millimeter range with sub-micrometer resolution, moving small payloads of a few grams and applying forces in the mN range.