Millimeter-wave radar distance measurements in micro machining

Abstract

In production and automation engineering the need for highest precision distance sensors is ubiquitous especially in the field of micro-machining processes where an extremely accurate positioning is indispensable. Although the work pieces become smaller and smaller many machine tools stay big and heavy. The reason for this is that a high precision is necessary and in this way the machine tools must be robust and stiff in their rails to prevent positioning errors due to tilts or twists. By using accurate sensors integrated in the rails of the machine tool the positioning error increases since the distance between the measurement of the position and the machine tool itself is relatively large. For this reason it might be advantageous to measure as close as possible at the tool center point (TCP) which could also allow for a reduction in machine sizes. A radar system might be a promising approach for this measurement due to the progressive development in radar technology along with new and fast algorithms. In this paper an frequency modulated continuous wave (FMCW) radar system is presented working around a center frequency of 80 GHz with a modulation bandwidth of 10 GHz. In combination with an innovative signal processing concept that uses frequency and phase evaluation a sub-micrometer accuracy can be achieved over distances up to several meters. The high accuracy of ±0.5 μm is demonstrated in a novel measurement setup for a kinematic using compliant mechanisms with flexure hinges

Micrometer Accuracy Phase Modulated Radar for Distance Measurement and Monitoring

“…In Table. I, the proposed radar system is compared with other related works. FMCW radars with phase analysis giving ranges of several micrometers was proposed in [3][4][5], however, these radars fail to address interference when multiple radars are closely located. Interferometer-based radar can also deliver good distance accuracy however its unambiguity distance is limited to the carrier wavelength and complicated calibration is often required [6].…”

“…On the contrary, radar sensors can work in a multi-sensor scenario and do not require a smooth target surface and dust-free environment. Traditional FMCW radar uses a chirp signal which requires a certain bandwidth to achieve a high distance accuracy [3][4][5]. Typically, the FMCW radar cannot share the spectrum with other FMCW radars.…”

OFDM Radar Range Accuracy Enhancement Using Fractional Fourier Transformation and Phase Analysis Techniques

“…The authors in [11] have proposed a highly miniaturized and commercially available millimeter wave radar sensor working in the 121-127 GHz, which can be utilized for micrometer range accuracy. FMCW radars at 120 GHz band have achieved micrometer level range accuracy [12], [13], but the measurement rate is often limited by the frequency sweep speed. Interferometer techniques with single tone or dual tone can be used to measure targets at high rate, but range ambiguity appears when target moves out of a limited range window [14], [15].…”

AMCW Radar of Micrometer Accuracy Distance Measurement and Monitoring

“…Narrow band radars can operate next to each other when different RF channels are used, in addition radar can be used for target detection even in dusty environment. Traditional frequency modulated continuous wave (FMCW) radars require a certain bandwidth to achieve a high ranging accuracy [3] [4] [5]. This implies that with a limited available bandwidth, the amount of radars that can be used in the same area is also limited.…”