افزایش دقت ردیابی برداری سامانه موقعیت‌یاب جهانی (GPS) در شرایط سیگنال ضعیف مبتنی بر فیلتر کالمن تطبیقی ردیاب قوی

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی برق، دانشگاه علم و صنعت ایران

چکیده

در این مقاله یک روش جدید برای ردیابی برداری سیگنال­ ماهواره­های GPS در شرایطی که سیگنال ضعیف می‌باشد، ارائه شده است. در ردیابی برداری معمولاً از فیلتر کالمن توسعه یافته (EKF) استفاده می‌شود. یکی از مشکلات فیلتر کالمن مرسوم، واگرایی آن‌ است. برای جلوگیری از واگرایی فیلتر کالمن، از فیلتر کالمن تطبیقی استفاده می‌شود. روش مرسوم تطبیقی­کردن فیلتر کالمن در ردیابی برداری، استفاده از پنجره‌ای با طول محدود می‌باشد اما طول این پنجره نمی‌تواند از یک حدی بزرگتر باشد و از طرفی، بعد از گذشت مدت زمانی اندک، فیلتر کالمن دوباره واگرا می‌شود. همچنین، طول پنجره به­صورت تجربی و با توجه به خصوصیات آماری تعیین می‌شود که ممکن است به ازای یک مقدار خاص جواب ایده­آل حاصل شود و به ازای یک مقدار دیگر چنین نشود. از این‌رو، در این مقاله از فیلتر کالمن تطبیقی ردیاب قوی (STKF) استفاده شده است. نتایج شبیه­سازی‌ها نشان می­دهد که STKF تطبیقی نسبت به EKF تطبیقی در ردیابی برداری از دقت بالاتری برخوردار بوده و همچنین درصورتی­که پارامترهای STKF به­درستی تنظیم شوند، پیچیدگی محاسباتی ردیابی برداری پیشنهادی کمتر از روش مرسوم خواهد بود. همچنین، نتایج نشان می­دهد که در ردیابی برداری مبتنی بر STKF تطبیقی نسبت به ردیابی برداری مرسوم، خطای اندازه‌گیری فرکانس حامل، خطای اندازه­گیری موقعیت و سرعت به مقدار قابل توجهی کاهش یافته است.

کلیدواژه‌ها


عنوان مقاله [English]

Enhancing Vector Tracking Accuracy of GPS in Weak Signal Condition Based on Adaptive Strong Tracking Kalman Filter​

نویسندگان [English]

  • Milad Anar Farhad
  • Seyyed Mohammad Reza Mousavi Mirkalaei
  • Ali Asghar Abedi
چکیده [English]

"In this paper, a new method for vector tracking of GPS satellite signals in weak signal circumstances is presented. Extended Kalman Filter (EKF) is usually used in vector tracking. As divergence is one of the main problems in common Kalman filters, Adaptive Kalman filters are used to avoid divergence. Common adaptive Kalman filter in vector tracking is implemented using a window with limited length, which cannot be greater than a specified amount and so after a short while Kalman filter will become divergent again. Window length is specified empirically and in accordance to statistical characteristics which may lead to an ideal solution for one specific amount, but not the other. Therefore adaptive Strong Tracking Kalman Filter (STKF) is used in this paper. Simulation results show that adaptive STKF has high accuracy in relation to adaptive EKF, and in case of correctly arranged STKF parameters computing complexity of the proposed vector tracking will be less than the traditional method. Results show that in comparison to traditional vector tracking ,methods based on adaptive STKF have significantly reduced errors in measuring carrier frequency, position and of course velocity.
 

کلیدواژه‌ها [English]

  • GPS
  • Vector Tracking
  • Strong Tracking Kalman Filter
  • Weak Signal
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