Parallel Microrobot localised in a large workspace – micro-SPIDER

Recent developments in microrobotics have focused on increasing the accuracy and dexterity of micromanipulators. Nevertheless, these robots remain very bulky compared to the size of the handled objects that induces a very unfavorable transported mass/moving mass ratio. The mass of these robots does not allow them to reach industrial rates either. A major challenge therefore concerns the reduction of the moving mass of micromanipulators. In addition, their workspace is often reduced because, on one hand, the precision of required performances often leads to a limitation of the actuator strokes and, on the other hand, the required measurement resolutions are generally obtained by sensors with small measurement range.
The objective of the micro-SPIDER project is to develop a new generation of micromanipulator combining a great dexterity (6 degrees of freedom), very low masses in movement and a micrometric precision over very large strokes. For this purpose, we propose to combine the know-how of the ROBERVAL laboratory in the fields of actuation and non-contact measurement with those of the FEMTO-ST institute in parallel microrobotics. This new micromanipulator generation is based on the use of a parallel structure whose feet will be mounted on mobile pallets. These pallets will be placed on an electromagnetic smart surface to move them in two (XY) or three degrees (XY?) of freedom over very large strokes. Since the movements of the pallets are limited to the plane, they are not able to perform directly three-dimensional micromanipulation tasks. To increase dexterity and in particular to obtain out-of-plane rotation movements, we propose to use and combine the movements of three pallets to actuate the parallel structure. An adapted deformable parallel architecture would indeed make possible to generate the six degrees of freedom of space from planar translation movements. As the actuation is performed by the smart surface, the parallel structure will be very light. The approach proposed here is innovative compared to current approaches that use more massive moving structures. Finally, parallel robots are known to have relatively small workspaces however, associated with a long-stroke smart surface, a parallel structure could reach a very large operational volume. This large range feature requires the development of a dedicated position measuring system of the parallel structure regardless of its position on the smart surface. The partners of the micro-SPIDER project propose two measurement approaches having in common the ability to perform a high-resolution measurement over a large planar range: a network of Hall effect sensors integrated into the smart surface, taking advantage of the magnetic property of pallets and a non-contact optical localization and tracking system with little impact on moving parts. Both measurement means will be compared in terms of their respective performances and measurements from these two systems can also be merged to improve the overall performances of the micromanipulator and streamline the deployment of these sensors.
The design and development methodology proposed in the micro-SPIDER project is also original since it couples a system approach allowing optimizing the overall design and performances of the proposed micromanipulator as well as a disciplinary approach (parallel structure, actuation system and measuring system) allowing to developing precisely each sub-system.