Nutation motion generator

Abstract

A nutation motion generator which transforms linear motion into nutation motion. The device employs a spherical, four-bar linkage mechanism. Three four-bar linkage mechanisms are sandwiched between a stationary support surface and a drive plate and arranged at 120.degree. intervals about the support surface. Each four-bar linkage mechanism is constructed of four planar sections which are hinged along their edges, the four hinged planar sections being essentially triangular in shape so that they would join at a point in the center of the device if they extended to the apex of their respective triangles. A universal joint is located at the center of the device to provide stability. The four-bar linkage mechanism can be collapsed to a substantially flatten configuration, opened and then collapsed to a substantially flattened configuration at an angle 90.degree. to that of the first flattened configuration. Since each four-bar linkage mechanism has this capacity, the drive plate can be positioned at any angle relative to the support surface. The movement of the four-bar linkage mechanisms is generated by an actuator consisting of three reciprocal-motion drivers connected between the hinged edges of adjacent four-bar linkage mechanisms which are driven by a controlled electric pulse. The reciprocal-motion drivers, for micro applications, are piezoceramic stacks. If the drive plate is circular and its outer perimeter is fitted with beveled gear teeth, a second gear (the 'driven' gear), with a smaller diameter than the drive gear, can be meshed with the drive gear to drive the driven gear at a reduced speed and at a relatively high torque. The three-dimensional motion of the mechanism makes the device very compact, and amplification is improved as the device is made flatter. In addition, the interaction between the nutating element and the top of the support surface creates a very large gear reduction.