Miniature low-power pan/tilt actuator for the pointing of small sensors

This paper presents a miniature pan/tilt pointing mechanism designed to point small sensors and other payloads anywhere within a +/- 45 degree(s) range at high speeds. Unlike other pan/tilt actuators, which predominantly use a motor-on-motor design to achieve two degrees of freedom motion, this device has only one moving part mounted on a ring-in-ring gimbal that is driven by a single 2D motor. Angular positioning of the payload, which is attached to the front side of the gimbal, is achieved by the interaction between a high energy samarium cobalt magnet, mounted on the back side of the gimbal, and the fields produced by four stationary coils. The coils are arranged on the sides of a pyramid structure that encloses the magnet and gives the payload an unobstructed 180 degree(s) field of view. This scheme allows the device to be much smaller, lighter, and inherently more efficient than traditional motor-on-motor pointing mechanisms. Miniature, non-contacting capacitive angular position sensors are integrated into each of the two axes to provide instantaneous position feedback to a controller. The magnetic and mechanical design of the device will be discussed along with the derivation of the various transfer equations and control laws. Open-loop performance data will also be presented.