Development of a high resolution radar-based position sensor

A new algorithm for precise position measurement based on microwave/radar technology has been developed. The new radar sensor has several differences in capability over conventional non-contact position sensors such as eddy current proximity probes, capacitive gauges, and laser-based systems. Microwaves have particular utility in measurement tasks that require performance: (1) in hostile environments-high temperature or where interference of nonmetallic materials, such as plastics, fluids, and dirt are present, (2) at high bandwidth-where the frequency response of capacitive and eddy current systems are limited, and (3) at greater standoffs-at greater ranges than eddy current or capacitance gauges can support. In this paper, the derivations an algorithm for position measurement using radar are shown and implemented using 35.4 GHz Ka band discrete component radar system. The measurements were compared with an encoder from a linear motor to illustrate performance. The microwave sensor provided measurements of a moving metal target over a range 100 mm within an error of ±0.1 mm at an approximate 50mm minimum standoff. The system was also tested and discussed in applications: (1) measuring runout of turbine blades and (2) measuring road terrain ahead of a moving vehicle. The strengths and limitations are discussed.