When is one arm better than two? When you’re trying to build a mobile-manipulator robot that somebody can actually afford to buy.
One of the problems that kept PR2, a humanoid robot developed by Menlo Park, CA-based Willow Garage, from succeeding commercially was its $400,000 price tag. And one of the things that made PR2 so expensive was that it had two arms, each replete with a complex series of joints, motors, and sensors. But as it turned out, most of the university labs and other institutions that bought PR2s never came up with applications that required both arms.