Kinematic Effects of Gimbal Joints on a 3URU Parallel Manipulator

Gimbal transmissions are non-linear direct transmissions and can be used in robotic arms replacing the traditional revolute joints. They offer potential advantages for critical cases such as joint space and task space singularities or where a different mechanical advantage is needed compared to what traditional revolute joints provide. This can be obtained by properly adjusting the different parameters of Gimbal joints used in different joints of the manipulator (such as their offset angle and/or chamfer angle). In this paper the concept of Gimbal mechanism as a joint is investigated. Then, as an example, Gimbal joints are used to replace the basic revolute joints of a 3-UPU parallel manipulator and actuator velocities are obtained for a task space trajectory. The outcomes for a manipulator with traditional revolute joints and with Gimbal equipped joints are compared. Then the workspace and dexterity analyses are done on both manipulators.