حداقل‌سازي خطای چندمسیری گیرنده ارزان‌قیمت GPS با استفاده از روش‌هاي ترکیبی PSO-SVM و GA-SVM
محورهای موضوعی : مهندسی برق و کامپیوترمحمد شمس اسفند آبادی 1 , محمدحسين رفان 2 , عادل دمشقي 3
1 - دانشگاه شهید رجایی
2 - دانشگاه تربیت دبیر شهيدرجايي
3 - دانشگاه تربیت دبیر شهيدرجايي
کلید واژه: GPSSVMGAPSOچندمسيري,
چکیده مقاله :
یکی از خطاهای بسیار تأثیرگذار بر مکان‌یابی دقیق GPS اثر چندمسیری مربوط به هر گیرنده است. چندمسیری، دریافت یک سیگنال توسط آنتن از بیش از یک مسیر است و این اثر یک منبع بزرگ خطای ناشناخته در مکان‌یابی است و با روش‌های تفاضلی حذف نمي‌شود. این اثر به طور گسترده‌ای وابسته به محیط‌های مختص هر گیرنده است و يک اثر فرکانس پايين است. هندسه بین ماهواره‌های GPS و مکان خاص هر گیرنده در روزهای نجومی تکرار می‌گردد و اثرات چندمسیری تمایل به رفتارهای مشابه در روزهای متوالی دارد. در این مقاله یک روش برای استخراج رفتار اثرات چندمسیری بر مشاهدات کد GPS اعمال شد و کاهش خطای چندمسيري موجب افزایش دقت مکان‌یابی مي‌شود. در روش پيشنهادي، سيگنال مانده بر اساس تفاضل دوگانه (DD) توليد شده و به عنوان ورودي الگوريتم پيشنهادي استفاده مي‌شود. برای تقریب و مدل‌سازی چندمسیری از مدل ماشین بردار پشتیبان (SVM) استفاده شده است. برای تعیین پارامترهای اساسی SVM و تابع کرنل آن از دو الگوریتم بهینه‌سازي گروهي ذرات (PSO) و الگوريتم ژنتيک (GA) استفاده شد. براي ارزيابي دقت روش پيشنهادي، شبیه‌سازي و آزمايشاتي بر اساس دو ايستگاه (مرجع و کاربر) و دو گيرنده ارزان‌قيمت طراحي شد، تست روش‌هاي پيشنهادي بر اساس داده واقعي انجام شد و آزمايشات نشان داد که خطای چندمسيري گيرنده ايستگاه کاربر بر اساس معيار RMS با این روش تا 70 درصد در حالت تست ايستا کاهش داشته است. مدل‌های این مقاله با برخی مدل‌های اخیر ارائه‌شده در زمینه کاهش خطای چندمسیری مقایسه شده‌اند. نتایج نشان داد که مدل پیشنهادی عملکرد بهتری نسبت به ساير روش‌ها داشته و از نتایج آن دقت بالا و پایداری نتایج در مکان‌یابی است. دقت مکان‌يابي سه‌بعدي پس از استفاده از روش پيشنهادي حدود 56% بهبود داشته و به 60/1 متر رسيده است
One of the major errors that affect GPS accurately is the multi-path effect of each receiver. Multi-paths is receiving an antenna signal from more than one path, multi-path effect is a major source of unknown error in positioning and is not eliminated by differential methods. This effect is largely dependent on the environment specific to each receiver and it is low-frequency effect. The geometry between GPS satellites and the specific location of each receiver is repeated on astronomical days, the multi-path effects tend to behave similarly on consecutive days. In this paper, a method for extracting the multi-path effects behavior was applied to the GPS-code observations, multi-path error mitigation increases the accuracy of positioning. In the proposed method, the residual signal is generated based on the dual difference (DD) and is used as the input of the proposed algorithm. Support Vector Machine (SVM) is used for multi-path approximation. To determine the basic parameters of SVM and its kernel function, particle optimization algorithms (PSO) and genetic algorithm (GA) were used. In order to evaluate the accuracy of the proposed method, simulation and experimental based on two stations (reference and user) and two low-cost receivers were designed. The proposed methods were tested based on practical data. The experiments showed that the multi-path error of the receiver of the user's station decreased by 70% in the static test based on the RMS criterion. Models of this paper have been compared with some recent models presented in the context of multi-path error reduction. The results showed that the proposed model had better performance than other methods. The result is high accuracy and stability in positioning results. Three-dimensional position accuracy improved by about 56% after using the proposed method, reaching 1.60 m.
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