It's stepper motor drive. Limited force feedback, so no doing "cobot" stuff.<p>Motors remain a headache in low-cost robotics. The good ones with good encoders and controllers cost too much. Steppers don't provide force feedback. Actuators based on R/C servos are too wimpy, usually lack good bearings, and have too much gear reduction.<p>This isn't fundamental. Brushless drone motors are really good 3-phase motors with good controllers and great power to weight ratios, and don't cost too much. But there's more volume in drones than in low-cost robot arms.<p>Take a look at what you can get on Alibaba for $3000 to $6000. The Annin thing costs somewhere about $3000, when you add up all the parts kits and consider the cost of 3D printing.
This is a really cool project, I have been meaning to build one of Annin's arms for a while. They appear to be well engineered and easy to work on, and I really appreciate the fact that many components are available in either a printed version or an aluminum version for when you want to be slightly more professional. I do wish he'd put the code and designs on Github but that's honestly such a minor complaint.