University System of Maryland

United Parcel Service of America, Inc.

Sun-Lai Chang

Lung-Wen Tsai

A semi-active compliance device forms part of a robot used to stack packages. The semi-active compliance device has an X-Y motion mechanism and a remote center compliance mechanism. The X-Y motion mechanism provides active open-loop control of the forces of a package along the X and Y axes so that the X- and Y-axis positions of the package will be passively controlled by the environment (e.g., walls and/or adjacent stacks of packages). The X-Y motion mechanism has two linear actuators and two pantographs. The remote center compliance mechanism provides passive orientation of the package about the Z axis. The semi-active compliance device also has a mechanism to return the remote center compliance mechanism to a home position.

Semi-active compliance device

A new and innovative concept for the control of backlash in gear-coupled transmission mechanisms. The concept utilizes redundant unidirectional drives to assure positive coupling of gear meshes at all times. Based on this concept, a methodology for the enumeration of admissible redundant-drive backlash-free robotic mechanisms has been established. Some typical two- and three-DOF mechanisms are disclosed. Furthermore, actuator torques have been derived as functions of either joint torques or end-effector dynamic performance requirements. A redundantly driven gear coupled transmission mechanism manipulator has a fail-safe advantage in that, except of the loss of backlash control, it can continue to function when one of its actuators fails. A two-DOF backlash-free arm has been reduced to practice to demonstrate the principle.

Growing community of inventors

Hyattsville, MD, United States of America

Sun-Lai Chang