Semi-global observer for multi-output nonlinear systems

Unmanned aerial vehicles (UAVs) have recently rapidly grown to facilitate a wide range of innovative applications that can fundamentally change the way cyber-physical systems (CPSs) are designed. CPSs are a modern generation of systems with synergic cooperation between computational and physical potentials that can interact with humans through several new mechanisms. The main advantages of using UAVs in CPS application is their exceptional features, including their mobility, dynamism, effortless deployment, adaptive altitude, agility, adjustability, and effective appraisal of real-world functions anytime and anywhere. Furthermore, from the technology perspective, UAVs are predicted to be a vital element of the development of advanced CPSs. Therefore, in this survey, we aim to pinpoint the most fundamental and important design challenges of multi-UAV systems for CPS applications. We highlight key and versatile aspects that span the coverage and tracking of targets and infrastructure objects, energy-efficient navigation, and image analysis using machine learning for fine-grained CPS applications. Key prototypes and testbeds are also investigated to show how these practical technologies can facilitate CPS applications. We present and propose state-of-the-art algorithms to address design challenges with both quantitative and qualitative methods and map these challenges with important CPS applications to draw insightful conclusions on the challenges of each application. Finally, we summarize potential new directions and ideas that could shape future research in these areas.

Design Challenges of Multi-UAV Systems in Cyber-Physical Applications: A Comprehensive Survey and Future Directions

Moving towards autonomy, unmanned vehicles rely heavily on state-of-the-art collision avoidance systems (CAS). A lot of work is being done to make the CAS as safe and reliable as possible, necessit ...

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Unmanned Aerial Vehicles (UAVs) : Collision Avoidance Systems and Approaches

This is the fourth part of a series of papers that provide a comprehensive survey of techniques for tracking maneuvering targets without addressing the so-called measurement-origin uncertainty. Part I [1] and Part II [2] deal with target motion models. Part III [3] covers the measurement models and the associated techniques. This part surveys tracking techniques that are based on decisions regarding target maneuver. Three classes of techniques are identified and described: equivalent noise, input detection and estimation, and switching model. Maneuver detection methods are also included.

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A Survey of Maneuvering Target Tracking—Part IV: Decision-Based Methods

This is a part of Part VI (nonlinear filtering) of a series of papers that provide a comprehensive survey of techniques for tracking maneuvering targets without addressing the so-called measurement-origin uncertainty. Part I [52] and Part II [48] deal with target motion models. Part III [49], Part IV [50], and Part V [51] cover measurement models, maneuver detection based techniques, and multiple-model methods, respectively. This part surveys approximation techniques for point estimation of nonlinear dynamic systems that are general, applicable to a wide spectrum of nonlinear filtering problems, especially those in the context of maneuvering target tracking. Three classes of such techniques are survey here: function approximation, moment approximation, and stochastic model approximation.

A survey of maneuvering target tracking: approximation techniques for nonlinear filtering

Collision avoidance strategies for multiple unmanned aerial vehicles (UAVs) based on geometry are investigated in this study. The proposed strategies allow a group of UAVs to avoid obstacles and separate if necessary through a simple algorithm with low computation by expanding the collision-cone approach to formation of UAVs. The geometric approach uses line-of-sight vectors and relative velocity vectors where dynamic constraints are included in the formation. Each UAV can determine which plane and direction are available for collision avoidance. An analysis is performed to define an envelope for collision avoidance, where angular rate limits and obstacle detection range limits are considered. Based on the collision avoidance envelope, each UAV in a formation determines whether the formation can be maintained or not while avoiding obstacles. Numerical simulations are performed to demonstrate the performance of the proposed strategies.

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Collision Avoidance Strategies for Unmanned Aerial Vehicles in Formation Flight

An improved method for tracking a maneuvering target is proposed. The proposed tracking filter is constructed by combining the recursive formulation of the input estimation approach with the variable-dimension filtering approach. In the proposed approach, the filter also provides the estimate of time instant at which a target starts to maneuver, when a target maneuver is detected. Using this estimated starting time of the maneuver, the maneuver input is also estimated and the tracking system changes to the maneuvering model. The computational load of the proposed procedure is comparable to that of the input estimation approach. Simulations are performed to demonstrate the efficiency of the proposed tracking filter, and comparisons with the interacting multiple model (IMM) filter, the input estimation filter and the variable-dimension filter are made. >

Tracking using the variable-dimension filter with input estimation

A consensus-based feedback linearization method is proposed to maintain a specified time-varying geometric configuration for formation flight of multiple autonomous vehicles. In this approach, any explicit leader does not exist in the formation team, and therefore the proposed control strategy requires only the local neighbor-to-neighbor information between vehicles. The information flow topologies between the vehicles can be defined by Graph Laplacian matrix, and the formation flight can be achieved by the proposed feedback linearization with consensus algorithm. The stability analysis of the proposed controller is also performed. Numerical simulation is performed for the rotary type unmanned aerial vehicles to validate the performance of the proposed controller.

Controller Design for UAV Formation Flight Using Consensus based Decentralized Approach

We propose a recursive design scheme of state observer for lower triangular nonlinear systems. The design begins from the bottom dynamics and propagates to upper dynamics recalling the backstepping scheme for nonlinear control, The proposed class of systems is fairly general since it includes non-uniformly observable or detectable multi-output systems. The error convergence to zero is proved assuming the boundedness of input a posteriori, which is preferable whereas most results in the literature assume the boundedness a priori. A global observer is proposed with the global Lipschitz condition of the system. However, this condition is removed via the Lipschitz extension technique when the semi-global observer is of interest.

J.H. Seo

Papers

Collision Avoidance Strategies for Unmanned Aerial Vehicles in Formation Flight

Tracking using the variable-dimension filter with input estimation

Controller Design for UAV Formation Flight Using Consensus based Decentralized Approach

Recursive observer design beyond the uniform observability

Differential Geometry based Collision Avoidance Guidance for Multiple UAVs