<p>Four-legged robots are multiplying in labs around the world, and a number of projects are drawing inspiration from one particular family of animals: big cats. This new breed includes Boston Dynamics's Cheetah, MIT's Cheetah Robot, Osaka University's Pneupard, and EPFL's CheetahCub. The latest specimen comes from South Korea and is called Cheetaroid.</p><p>Now, you may be asking why we need quadruped robots and, in particular, cat-inspired ones. The creators of the Cheetaroid, a team from Sogang University's Robotic Systems Control Laboratory, led by Professor Kyoungchul Kong, are envisioning different applications. They illustrate those in the image below, which shows how Cheetaroid could be used to assist firefighters, soldiers, disabled individuals, andwell, we're not exactly sure what's going on in the lower right image but we wouldn't want to be the guy in the bite suit.</p><p>Lately, most quadruped projects have focused on building faster and more efficient robots. One of the design challenges is choosing which actuators to use in place of the leg muscles. The actuators, which can take the form of electric motors, hydraulics, or even air-powered pneumatics, have to be relatively small and lightweight, yet also fast and powerful. That's a difficult combination to achieve, leading some teams to design their own hybrid systems in an attempt to get the best of both worlds.</p><p>For its robot, the Cheetaroid team decided to build its own direct-drive DC linear actuator. The idea is that this kind of actuator has lower friction and backlash than geared motors, and since it doesn't require gear reducers (which are used to amplify torque) they are more energy efficient and precise. The challenge is that by using linear actuators, the control system must account for changes in overall joint torque, which depends on the joint's angle, during locomotion.</p><p><a href="http://spectrum.ieee.org/automaton/robotics/robotics-hardware/south-korea-cheetaroid-quadruped-robot">Keep reading...</a></p>