Arctuator modules are modular actuators that provide translational motion along an arc. A motor mounted on one link of a parallelogram four-bar linkage directly drives the opposite link via a cable, gear, or friction drive. Any of the four links can be used as the base or output link, depending on whether relatively high force translational motion, relatively high motion range translational motion, or rotational motion is desired. Appropriately combining multiple modules yields devices that can provide planar or spatial translational motions. Concept designs that combine multiple Arctuator modules depict how the modules can be used for manipulation, fabrication, locomotion, and other applications. Experimental results demonstrate that a prototype Arctuator module is capable of accelerating a cantilevered load of double its own mass upward at 1 g.

We propose the use of robotic and haptic technology to develop haptic information displays for computer-assisted surgery applications. Such devices provide force and/or tactile feedback to a surgeon to communicate information that is difficult or impossible to communicate via a graphical display alone. Haptic information displays differ from autonomous robots and teleoperators used in surgical applications, and have different requirements than the haptic devices designed for training and simulation of surgical procedures. A haptic information display based on Barrett Technology's Whole-Arm Manipulator is introduced and early experiments for two different classes of medical applications are discussed. This new application area raises open research questions in the areas of haptic robotic systems and human machine interaction.

An existing hybrid control strategy is extended and applied to the control of a novel courier robot based on planar (Sawyer) motor technology augmented with integral sensing. The controller is designed to accommodate actuator limits and the desired motion characteristics, eliminating the need for careful matching of trajectory parameters with controller gains. Controller extensions allow for the unusual actuator constraints of the planar motors and independent adjustment of the parameters for each axis. Simulation results are presented for several cases to demonstrate the diversity of situations within the capability of the controller.

A miniature mobile vibratory parts feeder is proposed. This feeder, exploiting the unique capabilities of a closed-loop planar linear motor, is designed to reorient, separate, and position parts using only horizontal vibrations. The actuators used for generating the feed vibrations are also capable of large planar motions, allowing the feeder to serve multiple overhead robots. This feeder is designed with a minimum of critical physical dimensions, allowing different parts to be fed with only software changes. The basic feed principle is presented, followed by experimental verification. Although a prototype has not yet been fabricated, a model for the motion of parts on the complete feeder is derived and simulation results are presented.

Planar linear motors (Sawyer motors) have been used in industry as open-loop stepping motors, but their robustness and versatility has been limited. Using a sensor integrated into such a motor, a closed-loop 3-DOF controller has been implemented. The software-based control system consists of a commutator for computing amplifier currents from actuator forces, a force resolution function for solving the redundant actuation and saturation problems, and an observer for producing a velocity estimate, together with a PID controller. Experiments are performed using a 2-axis laser interferometer to show that the controller has sub-micron resolution, 2 /spl mu/m peak-to-peak repeatability, and settling times after trajectories of about 20 ms. Limitations of the PID controller are discussed and ideas for improvements are presented.

This work examines force modeling and software-based commutation for closed-loop control of planar linear motors, motivated by the need for a robust and versatile planar robot for precision assembly. The approach taken is to make measurements of the static and dynamic force capabilities of the motor as directly as possible, and determine the applicability of simple models commonly used. Measurements of force ripple, linearity with current, force reduction with skew angle, and eddy current damping forces are presented. The high-frequency current changes required for high-speed motion are shown to make the system sensitive to both the latency and update rate of the commutator and to limit the force generation capabilities at high velocities. Although this effect is caused by multiple sources, it is shown that it is well modeled as a scalar with units of time.

A new configuration of cooperative 2-DOF robots is presented for use in precision assembly applications. This configuration consists of direct drive planar linear motors traveling on a tabletop platen stator surface combined with overhead 2-DOF manipulators. We outline desirable features of a precision assembly system and use them to compare the proposed configuration to typical configurations that use 4-DOF robots. Advantages of the new approach are used to motivate further research needed to fully develop precision assembly systems based on this concept.