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Low-Cost INS/GPS Integration: Concepts and Testing
- M. E. Cannon, R. Nayak, G. Lachapelle, O. S. Salychev, V. V. Voronov
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- Journal:
- The Journal of Navigation / Volume 54 / Issue 1 / January 2001
- Published online by Cambridge University Press:
- 20 February 2001, pp. 119-134
- Print publication:
- January 2001
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The high cost of inertial units is the main obstacle for their inclusion in precision navigation systems to support a variety of application areas. Standard inertial navigation systems (INS) use precise gyro and accelerometer sensors; however, newer inertial devices with compact, lower precision sensors have become available in recent years. This group of instruments, called motion sensors, is six to eight times less costly than a standard INS. Given their weak stand-alone accuracy and poor run-to-run stability, such devices are not usable as sole navigation systems. Even the integration of a motion sensor into a navigation system as a supporting device requires the development of non-traditional approaches and algorithms. The objective of this paper is to assess the feasibility of using a motion sensor, specifically the MotionPak™, integrated with DGPS and DGLONASS information, to provide accurate position and attitude information, and to assess its capability to bridge satellite outages for up to 20 seconds. The motion sensor has three orthogonally mounted ‘solid-state’ micro- machined quartz angular rate sensors, and three high performance linear servo accelerometers mounted in a compact, rugged package. Advanced algorithms are used to integrate the GPS and motion sensor data. These include INS error damping, calculated platform corrections using DGPS (or DGPS/DGLONASS) output, velocity correction, attitude correction and error model estimation for prediction. This multi-loop algorithm structure is very robust, which guarantees a high level of software reliability. Vehicular and aircraft test trials were conducted with the system in land vehicle mode and the results are discussed. Simulated outages in GPS availability were made to assess the bridging accuracy of the system. Results show that a bridging accuracy of up to 3 m after 10 seconds in vehicular mode and a corresponding accuracy of 6 m after 20 seconds in aircraft mode can be obtained, depending on vehicle dynamics and the specific MotionPak™ unit used. The attitude accuracy was on the order of 22 to 25 arcmin for roll and pitch, and about 44 arcmin for heading.
Structure of Interfaces in Multilayers
- A. I. Fedorenko, Yu.P. Pershin, O. V. Poltseva, A. G. Ponomarenko, D. L. Voronov, S. A. Yulin
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- Journal:
- MRS Online Proceedings Library Archive / Volume 458 / 1996
- Published online by Cambridge University Press:
- 10 February 2011, 249
- Print publication:
- 1996
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Structure of interfaces in as-deposited state and after annealling at elevated temperatures was studied in variety of dc-magnetron sputtered multilayers by X-ray diffraction and high resolution electron microscopy. Interfaces in multilayers from materials without phase equilibrium (Mo/Si, W/Si, MO/B4C, Cr/C, Mo/(B+C)) are unstable and has the trend to evolution due to interlayer redistribution of chemical elements. Formation of the extended intermixed transition zones at interfaces is characteristic for multilayers from materials without phase equilibrium with each other. Unhomogeneous structure of materials along and across layers is responsible for nonuni-form proceeding of layer intermixing, development of interface roughness and differences of neighbour interfaces. It was shown that thickness asymmetry of intermixed transition zones at Mo/Si and Si/Mo interfaces in large-period Mo/Si multilayers is caused by different mechanisms of growth of Mo and Si on each other and by different structure of lower and upper parts of polycrystalline Mo-layers. Interfaces in multilayers from materials with phase equilibrium MoSi2/Si, WSi2/Si, OB2/C, TiC/C, Ni/C, MO2B5/B4C) are sharp and stable at elevated temperatures which gives the possibility to treat them for modification of their structure (smoothening, restoring sharp profiles of chemical elements). Multilayers W/Ti and W/TiN showed trend to formation of epitaxial superlattices with coherent or partially coherent (with misfit dislocations) interfaces and pseudomorphic state of layers.