Agile Quadruped Robot Unveiled By Italian Roboticists 45
An anonymous reader writes "Italian roboticists have built a quadruped robot called HyQ that can walk, trot, jump, and rear. Unlike with another quadruped project, the famous BigDog from Boston Dynamics, the Italian team wants to make their design 'as open as possible,' so other research groups can use it to collaborate. HyQ is a hydraulic system with torque-controlled, compliant legs. It's currently tethered, but the researchers plan to make the robot self-contained with an on-board pump, add a head with cameras and laser-range finder, and take it for tests outdoors."
Nice mechanics (Score:5, Informative)
The mechanics of the thing are nice. They have variable compliance in the legs, like real muscles. A muscle can be thought of as a spring/damper system where the spring constant and zero point of the spring are adjustable. This provides energy recovery from stride to stride. Humans get about 70% of the energy back from stride to stride when running efficiently. Cheetahs, 90%. This is a nice model for force control, but hard to realize with real machinery.
I've seen this done mechanically (the design was bulky, complex, and had way too many cables and pulleys) and pneumatically (at CWRU, a nice design, but needs external air power). Pneumatics are nice for this; with a cylinder you can pressurize from both ends, you really can create a spring with a settable spring constant and zero point.
There's a way to fake it with electric motors called "series elastic actuators", with a stiff spring in series with a fast electric-powered leadscrew, but there's no energy recovery. Hydraulic systems tend not to have energy recovery, although there are things you can do with hydraulic accumulators. The original BIgDog has almost no elastic energy recovery; there is a hydraulic accumulator in the system, but it's just to smooth out noise from the pump lobes.
I look forward to seeing more detail on this.