4 ms·
WRT 3: There is energy recovery, but it's very small and it's more like impedance matching. They've been used for outright storage (eg DURUS) but the springs a
by hwillis 9y ago
WRT 3: There is energy recovery, but it's very small and it's more like impedance matching. They've been used for outright storage (eg DURUS) but the springs are usually just too stiff. It still saves energy since there's a smaller initial current spike, but it doesn't save energy step-to-step. Unless you take really small steps, I guess.
- Animats 9y agoSoft spring systems are not usually considered series elastic actuators. There's a "soft actuator" branch of robotics, Shadow Robotics having been doing that for years. Disney has done some work in that space, because they want machines which are safe around people. As control techniques improve, that concept works better. There's a useful arrangement where you have two opposed springs powered by separate actuators. If you tighten up both springs, the system stiffens up; if you loosen both, you get better energy recovery but worse position control. This is a reasonable muscle model, and can recovery energy, but is bulky mechanically. Movement without load is cheap; changing the compliance is expensive from an energy standpoint. There's also a pneumatic version of this, where you pressurize an air cylinder from both ends. That works well if the valves are close to the cylinder. There are mechanical approaches to variable compliance, but they're complex mechanically and usually seem to involve string and pulleys.[1] The trend seems to be towards all-electric systems, rather than clever mechanics. [1] http://mime.oregonstate.edu/research/drl/publications/_documents/hurst_2010a.pdf http://mime.oregonstate.edu/research/drl/publications/_docum...