Parallel Jaw Mechanism

During my time at the Space Systems Laboratory at the University of Maryland, I worked on a team of four undergraduates to develop a parallel jaw mechanism (PJM) to be used with Ranger, a satellite servicing robotic system. Our research was centered around creating a PJM  that employs a torque limiter to combat repeated breaking seen in past designs.

Ranger

Ranger RTSX or Ranger Telerobotic Shuttle Experiment is a spaceflight qualified robotic system currently used for satellite servicing research at the University of Maryland's Space Systems Laboratory. It is capable of operating on land in 1G and in neutral buoyancy. The parallel jaw mechanism is designed to interface with the interchangeable end effector mechanism (IEEM) on Ranger's left dexterous manipulator (DXL). 

Parallel Jaw mechanism design

The PJM is designed to operate both on land and in neutral buoyancy to match the capabilities of Ranger. It is the first PJM design in the history of the lab to include a torque limiter. The device interfaces with two tool drives on the IEEM. One is a 7/16" socket wrench tool drive that is protected from overloading by the torque limiter. A second tool drive operates the jaws which allows for the robot to grasp a satellite while maintenance is being conducted. Much of my contribution to the design dealt with the jaws. 

Rotational motion is converted to linear motion via a plate with a two spiral cutouts. Inside these cutouts, track rollers which are screwed into the bottom of the jaws move along the spiral. Any horizontal motion of the rollers is eliminated by means of a guiding plate resulting in jaws that move linearly as the spiral plate is spun. The jaws themselves are constrained to linear motion further by linear guide rails mounted to the outside of the guide plate.