Ankle actuation for planar bipedal robots

This study focusses on ankle actuation of planar bipedal robots based on passive dynamic walkers. Simulations have been used to analyze the design characteristics which are necessary in robots fully powered by ankle actuation. The mass distribution between upper and lower and the shape of the foot have been found to be of major influence on the existence of a stable limit cycle. Simulation results show that pushing off before the swing leg collides with the floor is energetically more efficient than pushing off after the impact. The results were used to design and construct an ankle actuation system for the walking robot ’Dribbel’, which is developed at the Control Engineering group of the University of Twente. Mechanical requirements of the system were determined by means of simulations of a detailed 20-sim model. CAD tool packages were used to design the custom mechanical parts and electronics. The electronics interfaced to the TWI bus system already present at the robot. The realized system is not yet operational. This is due to several implementation issues which could not be resolved within the available time for this project. Possible solutions to the various problems are discussed and will be implemented in the near future. As soon as the system is fully operational experimental data will be gathered to validate the dynamic models used in the design process. A comparison will also be made to the previous configuration with respect to energy efficiency and robustness.