Development of vision based position estimation system and its use on autonomous takeoff and landing of rotary aerial vehicles

2014 ◽  
Author(s):  
Ufuk Suat Aydin ◽  
Engin Esin
Keyword(s):  
Position Estimation ◽  
Aerial Vehicles ◽  
Estimation System

scholarly journals MULTILATERATION UNDER FLIP AMBIGUITY FOR UAV POSITIONING USING ULTRAWIDE-BAND

2020 ◽  
Vol V-1-2020 ◽  
pp. 317-323 ◽  
Author(s):  
K. Park ◽  
J. Kang ◽  
Z. Arjmandi ◽  
M. Shahbazi ◽  
G. Sohn
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Linear Optimization ◽  
Position Estimation ◽  
Recursive Least Squares ◽  
Algebraic Solution ◽  
Planar Surface ◽  
Positioning Accuracy ◽  
Operational Conditions ◽  
Aerial Vehicles ◽  
Symmetric Reflection

Abstract. Ultrawide-band (UWB) ranging technology and multilateration techniques have recently been emerging solutions for positioning unmanned aerial vehicles (UAVs) in GNSS-denied environments. This solution offers cm-level ranging accuracy and considerable robustness to multipath receptions. UWB modules are commonly used in an anchor-based configuration; i.e., one UWB tag is mounted on the UAV, and several UWB anchors are installed on the ground. In real-world operational conditions, anchors can form a planar or a near-planar surface. This causes a geometric ambiguity, called flip ambiguity, in position estimation. Flip ambiguity can lead to considerable errors in the estimated position by multilateration. In this paper, we present a multilateration approach, which automatically resolves the flip ambiguity for UAV-positioning using UWB ranging. The proposed multilateration method first computes an algebraic solution through recursive least squares. If the initially estimated position is found to be flipped, then it is corrected by a symmetric reflection with respect to the anchor plane. Finally, the estimated position is refined by non-linear optimization. Extensive experiments in a real environment show that the proposed algorithm can effectively tackle the issue of flip ambiguity in multilateration, leading to a significant improvement in positioning accuracy.

Optimal Configuration of Ultrasonic Sensors in a 3D Position Estimation System Using Genetic Algorithms

2001 ◽  
Author(s):  
Probir Kumar Ray ◽  
Nishant Unnikrishnan ◽  
Ajay Mahajan
Keyword(s):  
Autonomous Vehicles ◽  
Wave Theory ◽  
Position Estimation ◽  
Optimal Placement ◽  
Accurate Estimation ◽  
Delay Term ◽  
Electronic Circuitry ◽  
3D Space ◽  
The Difference ◽  
Estimation System

Abstract This paper provides a genetic algorithm based approach to calculate the optimal placement of receivers in a 3D position estimation system that uses the difference in the time-of-arrivals (TOA) of an ultrasonic wave from a transmitter to the different receivers fixed in 3D space. This is a different approach to traditional systems that use the actual time-of-flights (TOF) from the transmitter to the different receivers and triangulate the position of the transmitter. The new approach makes the system more accurate, makes the transmitter independent of the receivers and does not require the need of calculating the time delay term that is inherent in traditional systems due to delays caused by the electronic circuitry. This paper presents a thorough analysis of receiver configurations in the 2D and 3D system that lead to singularities, i.e. locations of receivers that lead to formulations that can not be solved due to a shortage of information. It provides guidelines of where not to place receivers, and further, presents a detailed analysis of locations that are optimal, i.e. locations that lead to the most accurate estimation of the transmitter positions. The results presented in this paper are not only applicable to ultrasonic systems, but all systems that use wave theory, e.g. infrared, laser, etc. This work finds applications in virtual reality cells, robotics, guidance of indoor autonomous vehicles and vibration analysis.

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