Kinematics of Spherical Multi-Lobe-Cams for The Design of a Pitch-Roll Wrist

Cam-roller mechanism can be used in transmissions and robotic devices as an alternative to their bevel-gear counterparts. Compared with gear transmissions, cam-roller mechanisms feature low friction, low backlash, and high strength. However, cam mechanisms may end up with a high pressure angle if negative action, a motion in which the cam is driven by rollers, occurs. This paper reports the design of transmissions with multi-lobe-cams (MLC), as a means to reduce the pressure angle. The kinematics problems associated to MLC, including profile generation and transmission errors, are studied. As an example, a pith-roll wrist designed with MLC is described