FlegX Characterization and Control of a Flexible Robotic Leg

The purpose of this master thesis is to carry on a study on the effects induced by the structural elasticity in robotics systems. New challenges are oriented towards bioinspired, safe and energy efficient solutions. For instance nowadays advanced robots are not confined anymore to factories and manufacturing tasks, they have been designed to help humans in a vast variety of daily tasks. The introduction of elastic components could be a solution, if robots are conceived as structurally flexible they become lighter, this means that they need less energy to perform the same tasks with respect to their rigid counterparts. In addiction elastic components can store energy and release it in a later time, this brings to an increasing of the efficiency of the whole system. Furthermore, flexible components can be a solution to problems induced by the interaction with unstructured environment, because they can handle impulsive forces caused by both desired and/or accidental contact with either the surroundings or objects. To reach this achievement a test rig has been used composed by an already-made two links robotic leg with one of them conceived as flexible. Then the goal of this work is to design a suitable controller for its actuation as a first step in the design a new concept of a jumping humanoid robot as well as industrial robots. First an accurate characterization of the prototype is made in order to either measure or estimate all its electro-mechanical properties. Experimental results are compared to the simulations performed during the mechanical design phase. Afterwards the leg mathematical model is derived through the bond graph approach for both the flight and the stance phases. Once planned the closed loop system the friction disturbance effect is examined, then a controller for each phase is designed through the loop shaping technique and experimentally tuned. Finally, the achieved results are discussed along with the prototype structural, electronic and computer problems and limitations and future improvements are proposed.