TAILIEUCHUNG - Sensor Fusion and its Applications Part 10

Tham khảo tài liệu 'sensor fusion and its applications part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 264 Sensor Fusion and Its Applications CONVERGENCE RESULTS FOR TRUST REGION METHOD Fig. 6. Percentage of convergence test depending on network size and goodness of initial guess for TR approach. approach of More 1983 the smoothed version of the cost function is obtained by means of the Gaussian transform For a function f Rn R the Gaussian transform is defined as V x f a x -L2 ỉ f x Au exp - w 2 du. 14 nn 2 R Intuitively v x is the average value of f z in the neighborhood of x computed with respect to a Gaussian probability density. The parameter A controls the degree of smoothing large A implies a high degree of smoothing whereas for A 0 the original function f is recovered. The Gaussian transform of the cost function in 1 can be computed explicitly see Theorem on More 1983 . Proposition 1 Gaussian transform of localization cost . Let f be given by 1 . Then the Gaussian transform off is given by VA p f p Y 8A2 L IIpi - Pj II2 15 ij GE where Y 8mA4 4A2 L d2j. ij KE It is interesting to observe that for suitably large value of A the transformed function Va p is convex. This fact is stated in the following proposition. Proposition 2 Convexification of localization cost . Let f p be given by 1 and let Va p be the Gaussian transform off p . If A max di 16 2 Gj eE tj v then VA p is convex. Proof. From 1 and 15 we have that VA p Y L 8A2r2j p r2j p d2 2 ij eE Sensor Fusion for Position Estimation in Networked Systems 265 where we defined ĩịj p IIPi Pj . Let hij rij 8 2 r2 d2j 2. Then dh hij . p 4r j r2 d2 4A rij d2 h hij dr2 4 3r2j d2 4A2 . rij Note that hj 0 if 4A2 d2j r2 and hj 0 if 4A2 d2j 3r2j. Since rij 0 it follows that for 4A2 dj both hj and hij are positive. Therefore if A i max dij 17 2 j 1 then functions hij are increasing and convex for all i j . Observe next that function rij p is convex in p it is the norm of an affine function of p therefore by applying the composition rules to hij rij p see Section of Boyd 2004 we conclude that this latter function

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