[gene-h]

The main cost is the actuators. The servos they use are the only ones out there with integrated feed back from the sensors which is required so they can calculate hardware safety. They also have, albeit pretty bad, torque control which is necessary for many approaches to controlling legged robots and manipulators.

[contingencies]

According to a Chinese SCARA motor producer, Tamagawa is a notable Japanese manufacturer of servos used in SCARA robots. http://www.tamagawa-seiki.com/products/servomotor/

[lnsru]

Wouldn’t stepper motor with encoder and current sensor be cheaper?

[gene-h]

I'm skeptical that a stepper motor would be able to support it's own weight and more without a gearbox. This is especially important for making serial manipulators. Also keep in mind that what they're aiming for here is repeatability so that researchers can easily compare their algorithms. That means using parts that don't vary too much and minimizing the amount of assembly researchers have to do. There are much cheaper knock off versions of these actuators, although they may not be as repeatable. At the very least they aren't as well documented.

[Iv]

Steppers are highly repeatable.

[tastroder]

This is more about repeatable experiments than particular movements.

Regarding the price, the actuators seem to be ~240USD. A good stepper motor with the appropriate feedback mechanism to make it suitable for servo-like control plus a modern stepper motor controller that is suited for the robotics context will likely not be (much) cheaper and you have to hack together the servo functionality, tune settings, etc. - which seems detrimental if the goal is repeatability accross teams. I'm not in the target audience for these robots either but from the perspective of robustness and repeatable research they don't look too shabby.

[codesushi42]

That wouldn't work for a robotic hand.