Learning-based Uncertainty-aware Navigation in 3D Off-Road Terrains

This paper presents a safe, efficient, and agile ground vehicle navigation algorithm for 3D off-road terrain environments. Off-road navigation is subject to uncertain vehicle-terrain interactions caused by different terrain conditions on top of 3D terrain topology. The existing works are limited to adopt overly simplified vehicle-terrain models. The proposed algorithm learns the terrain-induced uncertainties from driving data and encodes the learned uncertainty distribution into the traversability cost for path evaluation. The navigation path is then designed to optimize the uncertainty-aware traversability cost, resulting in a safe and agile vehicle maneuver. Assuring real-time execution, the algorithm is further implemented within parallel computation architecture running on Graphics Processing Units (GPU).Comment: 6 pages, 6 figures, submitted to International Conference on Robotics and Automation (ICRA 2023

Decentralized Multi-Subgroup Formation Control With Connectivity Preservation and Collision Avoidance

This paper proposes a formation control algorithm to create separated multiple formations for an undirected networked multi-agent system while preserving the network connectivity and avoiding collision among agents. Through the modified multi-consensus technique, the proposed algorithm can simultaneously divide a group of multiple agents into any arbitrary number of desired formations in a decentralized manner. Furthermore, the agents assigned to each formation group can be easily reallocated to other formation groups without network topological constraints as long as the entire network is initially connected; an operator can freely partition agents even if there is no spanning tree within each subgroup. Besides, the system can avoid collision without loosing the connectivity even during the transient period of formation by applying the existing potential function based on the network connectivity estimation. If the estimation is correct, the potential function not only guarantees the connectivity maintenance but also allows some extra edges to be broken if the network remains connected. Numerical simulations are performed to verify the feasibility and performance of the proposed multi-subgroup formation control

Survey on the state-of-the-art in device-to-device communication: A resource allocation perspective

Device to Device (D2D) communication takes advantage of the proximity between the communicating devices in order to achieve efficient resource utilization, improved throughput and energy efficiency, simultaneous serviceability and reduced latency. One of the main characteristics of D2D communication is reuse of the frequency resource in order to improve spectral efficiency of the system. Nevertheless, frequency reuse introduces significantly high interference levels thus necessitating efficient resource allocation algorithms that can enable simultaneous communication sessions through effective channel and/or power allocation. This survey paper presents a comprehensive investigation of the state-of-the-art resource allocation algorithms in D2D communication underlaying cellular networks. The surveyed algorithms are evaluated based on heterogeneous parameters which constitute the elementary features of a resource allocation algorithm in D2D paradigm. Additionally, in order to familiarize the readers with the basic design of the surveyed resource allocation algorithms, brief description of the mode of operation of each algorithm is presented. The surveyed algorithms are divided into four categories based on their technical doctrine i.e., conventional optimization based, Non-Orthogonal-MultipleAccess (NOMA) based, game theory based and machine learning based techniques. Towards the end, several open challenges are remarked as the future research directions in resource allocation for D2D communication

Adaptive Second-Order Sliding Mode Algorithm-Based Modified Function Projective Synchronization of Uncertain Hyperchaotic Systems

This article proposes a synchronization technique for uncertain hyperchaotic systems in the modified function projective manner using integral fast terminal sliding mode (I-FTSM) and adaptive second-order sliding mode algorithm. The new I-FTSM manifolds are introduced with the aim of having the fast convergence speed. The proposed continuous controller not only results in the robustness and high-accuracy synchronization in the presence of unknown external disturbances and/or model uncertainties but also helps alleviating the chattering effect significantly. Numerical simulation results are provided to illustrate the effectiveness of the proposed control design technique and verify the theoretical analysis

Distributed estimation of stochastic multiagent systems for cooperative control with a virtual network

This article proposes a distributed estimation algorithm that uses local information about the neighbors through sensing or communication to design an estimation-based cooperative control of the stochastic multiagent system (MAS). The proposed distributed estimation algorithm solely relies on local sensing information rather than exchanging estimated state information from other agents, as is commonly required in conventional distributed estimation methods, reducing communication overhead. Furthermore, the proposed method allows interactions between all agents, including non-neighboring agents, by establishing a virtual fully connected network with the MAS state information independently estimated by each agent. The stability of the proposed distributed estimation algorithm is theoretically verified. Numerical simulations demonstrate the enhanced performance of the estimation-based linear and nonlinear control. In particular, using the virtual fully connected network concept in the MAS with the sensing/communication range, the flock configuration can be tightly controlled within the desired boundary, which cannot be achieved through the conventional flocking methods

Cyber attack analysis on cyber-physical systems: Detectability, severity, and attenuation strategy

Security of Cyber-Physical Systems (CPS) against malicious cyber attacks is an important yet challenging problem. Since most cyber attacks happen in erratic ways, it is usually intractable to describe and diagnose them systematically. Motivated by such difficulties, this thesis presents a set of theories and algorithms for a cyber-secure architecture of the CPS within the control theoretic perspective. Here, instead of identifying a specific cyber attack model, we are focused on analyzing the system\u27s response during cyber attacks. Firstly, we investigate the detectability of the cyber attacks from the system\u27s behavior under cyber attacks. Specifically, we conduct a study on the vulnerabilities in the CPS\u27s monitoring system against the stealthy cyber attack that is carefully designed to avoid being detected by its detection scheme. After classifying three kinds of cyber attacks according to the attacker\u27s ability to compromise the system, we derive the necessary and sufficient conditions under which such stealthy cyber attacks can be designed to cause the unbounded estimation error while not being detected. Then, the analytical design method of the optimal stealthy cyber attack that maximizes the estimation error is developed. The proposed stealthy cyber attack analysis is demonstrated with illustrative examples on Air Traffic Control (ATC) system and Unmanned Aerial Vehicle (UAV) navigation system applications. Secondly, in an attempt to study the CPSs\u27 vulnerabilities in more detail, we further discuss a methodology to identify potential cyber threats inherent in the given CPSs and quantify the attack severity accordingly. We then develop an analytical algorithm to test the behavior of the CPS under various cyber attack combinations. Compared to a numerical approach, the analytical algorithm enables the prediction of the most effective cyber attack combinations without computing the severity of all possible attack combinations, thereby greatly reducing the computational cost. The proposed algorithm is validated through a linearized longitudinal motion of a UAV example. Finally, we propose an attack attenuation strategy via the controller design for CPSs that are robust to various types of cyber attacks. While the previous studies have investigated a secure control by assuming a specific attack strategy, in this research we propose a hybrid robust control scheme that contains multiple sub-controllers, each matched to a specific type of cyber attacks. Then the system can be adapted to various cyber attacks (including those that are not assumed for sub-controller design) by switching its sub-controllers to achieve the best performance. Then, a method for designing a secure switching logic to counter all possible cyber attacks is proposed and it verifies mathematically the system\u27s performance and stability as well. The performance of the proposed control scheme is demonstrated by an example with the hybrid H2 - H-infinity controller applied to a UAV example

High Assurance Control of Cyber-Physical Systems with Application to Unmanned Aircraft Systems

With recent progress in the networked embedded control technology, cyber attacks have become one of the major threats to Cyber-Physical Systems (CPSs) due to their close integration of physical processes, computational resources, and communication capabilities. While CPSs have various applications in both military and civilian uses, their on-board automation and communication afford significant advantages over a system without such abilities, but these benefits come at the cost of possible vulnerability to cyber attacks. Traditionally, most cyber security studies in CPSs are mainly based on the computer security perspective, focusing on issues such as the trustworthiness of data flow, without rigorously considering the system’s physical processes such as real-time dynamic behaviors. While computer security components are key elements in the hardware/software layer, these methods alone are not sufficient for diagnosing the healthiness of the CPSs’ physical behavior. In seeking to address this problem, this research work proposes a control theoretic perspective approach which can accurately represent the interactions between the physical behavior and the logical behavior (computing resources) of the CPS. Then a controls domain aspect is explored extending beyond just the logical process of the CPS to include the underlying physical behavior. This approach will allow the CPS whose physical operations are robust/resilient to the damage caused by cyber attacks, successfully complementing the existing CPS security architecture. It is important to note that traditional fault-tolerant/robust control methods could not be directly applicable to achieve resiliency against malicious cyber attacks which can be designed sophisticatedly to spoof the security/safety monitoring system (note this is different from common faults). Thus, security issues at this layer require different risk management to detect cyber attacks and mitigate their impact within the context of a unified physical and logical process model of the CPS. Specifically, three main tasks are discussed in this presentation: (i) we first investigate diverse granularity of the interactions inside the CPS and propose feasible cyber attack models to characterize the compromised behavior of the CPS with various measures, from its severity to detectability; (ii) based on this risk information, our approach to securing the CPS addresses both monitoring of and high assurance control design against cyber attacks by developing on-line safety assessment and mitigation algorithms; and (iii) by extending the developed theories and methods from a single CPS to multiple CPSs, we examine the security and safety of multi-CPS network that are strongly dependent on the network topology, cooperation protocols between individual CPSs, etc. The effectiveness of the analytical findings is demonstrated and validated with illustrative examples, especially unmanned aircraft system (UAS) applications