Design, Modeling, and Prototyping of a Simple Semi-Modular Biped Actuated by Shape Memory Alloys

Abstract

In this article, a prototype of a biped robot actuated by SMA springs with minimum degrees of freedom is presented. SMA springs are a class of smart materials that are known for their high energy to weight ratios. It is shown that utilizing spring type SMAs has many advantages as large deformation, smooth and silent motion compared to ordinary type of actuators. A modular concept is applied for the development of the proposed biped robot where the SMA springs are utilized as actuators. A module with proper DOF is developed, that is its position and stiffness is controllable and makes the biped stable with five DOFs. Walking trajectory is generated validating the ZMP criteria and it is shown that this criterion can be simplified to the COG criteria due to slow response nature of the SMAs. To verify the design, a complete model of the biped actuated with SMA is developed through simulation with the help of MATLAB and Visual.Nastaran software. Finally to validate the results, a prototype is manufactured and tested. Experimental results show reasonable agreement with simulation results which resulted in stable walking of the proposed biped.