Towards a Discrete Snake-Like Robot Based on SMA-Actuated Tristable Modules for Follow the Leader Control Strategy

Snake-like robots applications include surveillance and exploration of confined environments where human presence is incompatible. The attractiveness of this type of mechatronic structure is notably linked to the modular character and the hyper-redundancy of their architecture, which gives it both mechanical robustness and great manoeuvrability. However, due to the large number of degrees-of-freedom, the use of advanced mathematical models are needed to asses the motion patterns and to simulate it. A new snake-like robot architecture is introduced in this paper together with the development methodology of a replicable multistable module. The interest of this contribution lies in the combination of the mechanical stability of the modules with an easy-to-use direct kinematic model, thus avoiding the need of complex control strategies. The design of one module exploiting the three stable states of a tristable flexible mechanism so as to orient the articulation of the module at three distinct stable angles is first presented. Then a prototype of a modular snake-like robot is built and experimentally evaluated. The prototype consists of 4 modules that can be individually oriented by $\pm$7.1 degrees. Each module measures 51.5 × 32 mm and weighs 2.5g. Thereby, this work provides the first results on the feasibility of this robotic architecture which consists of several multistable modules. A good agreement between the working space estimated with the direct kinematic model and experimental measurements is obtained. According to the fact that these are preliminary results, there is a 1.5% error between the experimental results and the models.