Localization Of A Rigid Body With A Calibration Emitter In The Presence Of Rigid Body Sensor Uncertainties

With the rapid development of information technology,wireless sensor network(WSN)has become one of the most widely used wireless network technologies,due to its various applications including the military,medical,transportation,and home fields.In many applications of wireless sensor network technology,location-based service is the basis of all applications,and it is also one of the hot issues studied by researchers at home and abroad.Therefore,the WSN-based positioning technology is one of the key technologies in WSN application,which has high research significance and application value.In target localization based on WSN,the traditional localization models the object of interest as a point source or a single node whose location is defined by a unique position in the three-dimensional(3-D)or two-dimensional(2-D)space.However,in many applications based on localization,the object to be located has a certain geometric structure,fixed size and shape with negligible deformation once manufactured under the condition of no external force damage.In such a case,the object of interest is regarded as a rigid body localization(RBL)which is an extension of the traditional point positioning.The challenge is not only to determine the position as well as the orientation of a rigid body.This paper investigates the problem of RBL where a calibration emitter with noisy position is used to mitigate rigid body sensor position uncertainties.The main research works and contributions of this paper are summarized as follows:1.The RBL problem is a highly nonlinear constrained optimization problem as the rotation matrix defining orientation must belong to the special orthogonal group.Aiming at this problem,we propose the use of Euler angles instead to parameterize the rotation matrix,which not only satisfies the constraints of the special orthogonal group,but also reduces the optimization problem to an unconstrained one,thus the unconstrained Cramer-Rao Lower Bound(CRLB)can be derived.In addition,most of the research work on RBL problem assume that both anchor position and sensor position are known exactly,in this paper,a new RBL scenario is proposed: this paper focuses on RBL in the presence of rigid body sensor position errors and the absent of anchor position errors in monitoring area.2.To solve the problem that the presence of rigid body sensor position errors degrades the accuracy of both orientation and position considerably,a new idea of introducing a calibration emitter with location uncertainty has been proposed to improve rigid body sensor position errors.Starting from the derivation of the unconstrained CRLB in the presence of rigid body sensor position errors and a calibration emitter,we analyze the effect of rigid body sensor position errors on RBL and show that a calibration emitter,although has location uncertainty,can greatly improve and will not degrade the estimation performance in theory.The simulation experiment also verify the feasibility and validity of the proposed calibration emitter.3.On the basis of the existing Maximum Likelihood Estimate(MLE)methods for RBL,a new enhanced MLE methods with a noisy calibration emitter are designed and solved by Gauss-Newton iteration method to reduce rigid body sensor position errors.The theoretical analysis shows that the improved method can effectively reduce the degradation of location performance caused by rigid body sensor position errors when the sensor position noise is at a low level,and can achieve CRLB performance.4.In view of the high computational complexity of MLE iterative algorithm,based on the existed DAC algorithm,we extend the previous work that can mitigate the rigid body sensor position errors with the use of a calibration emitter.The simulation results show the effectiveness of the improved algorithm.