Advanced Parallel Actuation of a Serial Robotic Leg

Advanced actuation methods are needed in legged robots in order to build robust and efficient robotic systems. State of the art robots either consume much more energy than their biological counterparts or are dramatically less mobile. Advanced actuation methods are necessary to achieve both efficiency and mobility. Many highly mobile legged robots are actuated in serial, but serial actuation has many known weaknesses. This research explores a new and promising method of actuation that is a hybrid of serial and parallel actuation. This method is able to draw from the large body of research conducted on parallel manipulators over the last several decades. This research has shown that parallel manipulators can offer many advantages over serial arms including: smaller mobile mass, more rigidity, faster end effector speeds, and large force capacity. All of these advantages are well suited for the requirements of legged robots. In this paper, the authors detail the implementation of this advanced actuation method from conceptualization to the first stages of testing. It details the choice of configuration, which was important, and somewhat counter intuitive. It also walks through the kinematic solutions, showing relatively simple solutions to challenging problems. The goal of the work is to use multiple, small motors in parallel to actuate the hip and the knee. In this way, during the stance phase of gait, multiple motors can be used in parallel to provide a powerful burst for push-off. Our two-link parallel structure allows the motors to cross multiple joints and therefore can be used to actuate several joints at once. In addition, by mounting motors at the base, the inertia of the leg is greatly reduced.B@Creating a fast, efficient leg structure is the first step in our project. The higher level goal of this research is to create a quadruped robot that is designed for efficient and fast running. The novel leg structure described in this paper will be capable of the types of motions associated with high speed gait. The robot needs to be capable of both high speed motions and high force output, without being excessively heavy. It should also be capable of accurate three dimensional control, and meet certain manipulability criterion. In this paper we show a functional and promising 3D printed leg prototype. This paper will provide a detailed description of this unique approach to actuation. It will also show the solution to the kinematic equations. Finally, as a proof of concept, the leg was moved in a gait pattern over a treadmill.