Inside GNSS Media & Research

JUL-AUG 2018

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26 InsideGNSS J U L Y / A U G U S T 2 0 1 8 example with video cameras and motion models (non-holonomic constraints). The webinar addresses several examples and features of consumer-grade IMUs, as well as chal- lenges such as large sensor errors, partially de- fined (undefined) specs and nonlinearities (head- ing drift). However, Soloviev adds, the bias (drift) stability and noise performance has improved significantly, enabling the use of consumer-grade IMUs for improved robustness of GNSS (coasting through outages and weak signal recovery). Examples of the use of GNSS carrier measure- ments/integration with GNSS carrier phase and a case study of performance results in urban can- yons in San Francisco highlighted how the use of consumer-grade IMUs can enhance robust- ness of GNSS signal processing, even in parking garages. Additionally, improved performance of consumer-grade MEMS IMUs allowing for deep integration with low-cost inertial sensors was shown, with a UAV demonstration as an example. GYRO TECHNOLOGY Gaber delivered an overview of gyro technology that includes the IMU evolution, Epson's IMU feature set, and background on the company's 20 years of R&D in the field. Key components include vertical integration, quartz cr ystal, Q MEMS and Q MEMS uses. Epson produces and utilizes 100% synthetic quartz crystal for all inertial sensing products. The company's Q MEMS elements are highly stable over temperature and the QMEMS gyro- scopes are designed to offer superior stability. The quartz MEMS fabrication process is used for many product lines, including timing products, real-time clocks and inertial sensors. The company controls the quartz basically from raw material all the way to sensor fabrica- tion, Gaber said. "Quartz crystal as a medium for inertial sen- sors is actually fairly fantastic because you have very efficient yielding," he said. "You also have a uniform size shape and quality. And this is of course different than the quartz found in nature; while beautiful and certainly very expensive, it's difficult to actually work with particularly the inertial sensors coming from them." The fabricated material itself is very stable and Epson can effectively store already pro- duced crystal for five to 10 years before you have any recognizable stability changes, according to Gaber. "We drive these sensors very hard. These are vibration sensors and quartz lends itself well to high vibration," he said. "You sim- ply don't break it and you don't lose vibration and even after many, many hours. Most impor- tantly for inertial sensing is that we talk about WEBINAR RECAP » OPTIMIZING GNSS+INS PERFORMANCE Visual results from a test scenario of extended GNSS outage at Calgary International Airport. NovAtel's OEM6 ® SPAN with a MEMS IMU (left) in standard mode; OEM7 ® Default SPAN (center); and OEM7 with SPAN Land Vehicle (right), where constraints are turned on. " WE HAVE GAINED additional performance for vehicles in tunnels, for mining equipment, agricultural equipment in fields or in the pit mines." Ryan Dixon, chief engineer of NovAtel's SPAN GNSS+INS products group

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