Angular rate sensors

A vibrating structure angular rate sensor has an annular member flexibly supported on a substrate so that the member can move elastically relative to the substrate. The member is driven at large amplitudes with the restoring force of the supports depending nonlinearly on the amplitude of motion. The number of supports is selected to ensure that the frequencies of the driven (primary) mode and the sense (secondary) mode are identical. This may be achieved by choosing the number p of supports to ensure that kn/p is not an integer, where k is between 1 and 6 and n is the wave number of the driven mode. In the case where n=2, so that the driven mode is cos(n theta), the number of supports may be selected as p=16+8m, where m is a non-negative integer. The supports may be fixed to the substrate at a central support inside the annular member.