An Actuation Mechanism for a Dual-Arm Robotic Manipulator

Abstract

An actuation mechanism for a dual-arm scara-type robot for automated pick-place operations in semiconductor and flatpanel-display manufacturing applications is described. The mechanism consists of a pivoting platform and two linkages coupled to the platform through a pair of revolute joints. The opposite ends of the linkages are connected to the upper arms of the robot by another pair of revolute joints, forming a pair of three-bar mechanisms coupled through the pivoting platform. When the platform is in its neutral position, both of the arms are retracted. The geometry of the components of the mechanism is selected so that rotation of the platform from the neutral position in one direction produces desirable radial motion of one arm while the other arm is kept almost stationary in the retracted position. The arms exchange their roles when the platform rotates from the neutral position in the opposite direction. Alternatively, to achieve absolutely no motion of the retracted arm while the other one extends, the pivoting motion of the platform can be replaced by a rocking arrangement with two pivot points. In this configuration, the locations of the two pivot points coincide with the locations of the revolute joints between the linkages and the upper arms when the platform is in the neutral position. As a result, rotation of the platform with respect to one of the pivot points produces no motion of the corresponding arm while the other one extends. Compared to a conventional design, which utilizes a pair of motors coupled to the robot arms through a pair of belt arrangements, the present mechanism eliminates one of the two motors, including its electronic circuitry, and replaces the belt drives with rigid linkages, thus reducing the complexity and cost, and improving the reliability and cleanliness of the robotic system.