Modelling and adaptive control of nanowire-driven micromanipulators

The design problem of an adaptive controller for a robotic micromanipulator is considered in this article. The micromanipulator's dynamic model is appropriately modified in order to include the interaction of the attractive Van der Waals (VdW) forces that are typically encountered in the microworld. For modelling purposes every link is decomposed into a series of elementary particles (e.g. spheres), each one interacting with the robot's neighboring objects during its motion. This interaction induces nonlinear additive terms in the model, attributed primarily to the overall effect of the VdW-forces and secondarily by the nanoscale friction. Sparked by recent advancements in nanowires the actuation is achieved by a nanowire-driven system in a tendon-like configuartion. At each joint, a pair of nanowires are attached and act in a passive antagonistic manner. The kinematic and dynamic analysis of the nanowire-driven actuationmechanism is offered. Consequently, the microrobot's model is shown to be linearly parameterizable. Subject to this observation, a globally stabilizable adaptive control scheme is derived, estimating the unknown parameters (masses, generalized VdW-forces) and compensating any variations of those. Simulation studies on a 2-DOF and a 10-DOF planar micromanipulator are offered to highlight the effectiveness of the proposed scheme.