Upside down: an open-source motion platform for highly dynamic movement

Abstract:
Parallel robots are capable of high-speed manipulation and have become essential tools in the industry. The proximal placement of their motors and the low weight of their end effectors make them ideal for generating highly dynamic motion. Therefore, we can adopt parallel robots for motion platform designs if end effector loads are low. Traditional motion platforms can be large and powerful to generate multiple g accelerations. However, these designs tend to be expensive and large. Similar but smaller motion platforms feature a small work range with reduced degrees of freedom (DoFs) and a limited payload. Here we seek a medium-sized, affordable parallel robot capable of powerful, high-speed 6-DoF motion in a comparably large workspace. We explore the concept of a quadruped robot flipped upside-down, with the motion platform fixed between its feet. In particular, we exploit the high-power dynamic brushless actuation and the four-leg redundancy when moving the motion platform. We characterize the resulting motion platform by tracking sinusoidal and circular trajectories with varying loads. Dynamic motions in 6 DoFs up to 2 Hz and ± 20 mm amplitude are possible when moving a mass of 1.2 kg. For single-axis end-effector translations, we demonstrate up to 10 Hz and ± 10 mm amplitude for loads of 0.3 kg. The motion platform can be replicated easily by 3D printing and with off-the-shelf components. All hardware designs and custom-written software are open-source available.