Active knee-lock release for passive-dynamic walking machines

Passive-dynamic walkers are mechanical devices that can walk down a slope without motors or controllers. Here we present a design improvement to the construction of these machines. We have built a classical passive-dynamic walking machine, but we have replaced the original suction cups knee-locking mechanism with two new designs: one with passive magnetic lock, and another that features an active release. We are doing experiments with both designs and with each design we do a set of a hundred trials and we try to setup the walker in such a way so it is able to achieve maximum number of steps. At the end of this paper we compare the experimental results and we try to show that the new knee-lock mechanism with active release is not only simpler, but also more effective than the magnetic one, which we eventually dismiss as an unsuccessful, and also the original suction cup one. We also describe in detail the design of the walker, including both knee designs, the feet and a new external bearing holder for the hip, which allows easy replacement and use of upper legs with different length and shape.