| A novel planar robot is used to demonstrate that large numbers of axes are not required for effective manipulation, and that there can be strong advantages to eliminating excess degrees-of-freedom. This robot combines sub-micron precision with a meter-sized workspace, motions with velocities above 1 m/s, and accelerations several times that of gravity. It combines planar stepping motor (Sawyer motor) actuation technology with a compact, high-precision, high-bandwidth position sensor developed at Carnegie Mellon University.; The actuator operation is experimentally characterized over the closed-loop operating regime using an automated experimental setup that incorporates a laser interferometer and load cell. Parametric models are constructed based on these experiments that allow autonomous calibration of the actuators and sensors. This calibration enables on-site calibration, improving the precision of both positioning and force output without requiring external measuring devices.; Coupled with software-based calibrated models and commutation, the stepping motor actuators can be operated as servo motors, simplifying the controller design and eliminating the underdamped oscillation modes that limit the robustness of open-loop stepping operation. PD and PID controllers are used to demonstrate the performance improvements from closed-loop operation, which include improved repeatability (to sub-micron levels), fast settling times (20 ms), and a four-fold decrease in energy usage.; The main application of interest for this robot is conveyance and fine motion control of subproducts in a rapidly-deployable assembly system called minifactory. This system requires low-DOF robotic agents to cooperatively perform higher-DOF tasks, coordinating their actions through optical endpoint sensing, networked communications, or the task dynamics. It also requires each robotic agent to be trustworthy to ensure system reliability. The performance and robustness of closed-loop operation is demonstrated with a high-speed wall-following task, a high-precision visually guided positioning task, and a dynamic visual tracking task.; A mobile parts feeder is also presented. This application exploits the dynamic range of the planar robot, which allows for gross motion and precision positioning of the feeder as well as a high enough bandwidth to generate 30 Hz vibratory waveforms. This application makes good use of the limited travel rotational axis of the robot. |
