Four Legged Guará Robot: From Inspiration to Implementation

Design of legged robots is still an open problem with several implementation challenges and there is little material available to guide new designs. Moreover, usually the actuator sets of the robot are heavy and bulky and are placed near the joints, which increases the weight and inertia of the legs and consequently results in instability, slower movement and high energy consumption. This paper presents the design, modeling, and control of the Guará, a sixteen-degree-of-freedom (DOF) legged robot, covering all stages of development of a quadruped robot, including experiments with a prototype. The system is composed by four legs, each one with 4 DOF. To reduce the leg’s weight and inertia, here we present a design concept for the legs where the actuators are positioned on the robot platform and timing belt transmissions are used to drive the joints. Moreover, the design of the legs mimics the human leg by presenting the knees faced forward and its locomotion pattern mimics the quadruped wave gait. With this configuration, the robot is able to walk on straight lines or free curved paths. The control system of the robot consists of a high-level state machine and a lower level PID position controller. The electronics are embedded over a flat platform coupled to the legs. The kinematics of the robot was studied and an integrated environment was provided for walking simulation, adjustment, and diagnosis of operation. The experimental results are focused on the kinematics of the legs and the stability of the robot and show a good agreement between the designed and executed movements. This paper is presented as a framework that can be generalized to other systems and can be a useful reference for the design of other legged robots