Design and Control of SLIDER: An Ultra-lightweight, Knee-less, Low-cost Bipedal Walking Robot

Abstract

Most state-of-the-art bipedal robots are designed to be anthropomorphic and therefore possess legs with knees. Whilst this facilitates more human-like locomotion, there are implementation issues that make walking with straight or near-straight legs difficult. Most bipedal robots have to move with a constant bend in the legs to avoid singularities at the knee joints, and to keep the centre of mass at a constant height for control purposes. Furthermore, having a knee on the leg increases the design complexity as well as the weight of the leg, hindering the robot's performance in agile behaviours such as running and jumping. We present SLIDER, an ultra-lightweight, low-cost bipedal walking robot with a novel knee-less leg design. This non-anthropomorphic straight-legged design reduces the weight of the legs significantly whilst keeping the same functionality as anthropomorphic legs. Simulation results show that SLIDER's low-inertia legs contribute to less vertical motion in the center of mass (CoM) than anthropomorphic robots during walking, indicating that SLIDER's model is closer to the widely used Inverted Pendulum (IP) model. Finally, stable walking on flat terrain is demonstrated both in simulation and in the physical world, and feedback control is implemented to address challenges with the physical robot.