  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, parallel robots can be adopted for motion platform designs,
as long as end effector loads are low. Traditional motion platforms can be
large and powerful to generate multiple g acceleration. 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 and
high-speed 6-DoF motion in a comparably large workspace. This work explores 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
10 Hz and ~10 mm amplitude are possible when moving a mass of 300 grams. We
demonstrate single-axis end-effector translations up to ~20 mm at 10 Hz for
higher loads of 1.2 kg. The motion platform can be replicated easily by 3D
printing and off-the-shelf components. All motion platform-related hardware and
the custom-written software required to replicate are open-source.
