Philip Chen

Trajectory planning for an unmanned ground vehicle group using augmented particle swarm optimization in a dynamic environment

Optimal path planning is a key problem for the control of autonomous unmanned ground vehicles. Particle swarm optimization has been used to solve the optimal problem in the static environment; however, optimal path planning for UGV groups in a dynamical environment has not been fully discussed. Accordingly, a dynamic obstacle-avoidance path planning for an unmanned ground vehicle group was considered as optimal problem for shortest path with formation constraints. The problem was formulated in Cartesian space with detectable velocity of both the vehicles and obstacles. The fitness function was defined by minimizing the trajectory of the group while keeping the V-shape formation of the group. Stable region of the parameters are determined by analyzing the convergence of the PSO algorithm. The simulation results demonstrated that the augmented particle swarm optimization could get the shortest path while keeping the V-formation and converged very fast.

Integrity monitoring and thresholding-based WLAN indoor positioning algorithm for mobile devices

The Global Positioning System (GPS) works well in outdoor areas, but the satellite signals are not strong enough to penetrate inside most indoor environments. 802.11 wireless LANs (WLAN) signals have been explored for more accurate positioning indoors. Contemporary WLAN positioning maintains the database of location-associated signal fingerprints which is used to identify the most statistically likely match of incoming signal data with those preliminary surveyed and saved in the database. An issue with these systems, however, is the operation robustness. This paper investigates the issue of deploying WLAN positioning software on Android mobile platforms and studies an integrity monitoring technique to account for fading signal characteristics, which are often observed in WLAN networks. Integrity monitoring algorithms exploit redundancy of access points and isolate those with corrupted characteristics to improve system robustness.

Remaining engine life estimation for a sensor-based aircraft engine

It is generally known that an engine component will accumulate damage (life usage) during its lifetime of use in a harsh operating environment. The commonly used cycle count for engine component usage monitoring has an inherent range of uncertainty that can be overly costly or potentially less safe from an operational standpoint. This paper describes an approach to quantify the effects of engine operating parameter uncertainties on the thermomechanical fatigue (TMF) life of a selected engine part. A closed-loop engine simulation with a TMF life model is used to calculate the life consumption of different mission cycles. A Monte Carlo simulation approach is used to generate the statistical life usage profile for different operating assumptions. The probabilities of failure of different operating conditions are compared to illustrate the importance of the engine component life calculation using sensor information. The results of this study clearly show that a sensor-based life cycle calculation can greatly reduce the risk of component failure as well as extend on-wing component life by avoiding unnecessary maintenance actions.

A received signal strength indication-based localization system

Localization using the received signal strength indication (RSSI) of wireless local area networks with a priori knowledge of the coordinates of the routers/access points is addressed in this paper. The proposed algorithm employs a path loss model that allows for the inclusion of the logarithmic measurements of the signal strength directly in the state of the nonlinear system that is designed. The nonlinear system is augmented in such a way that the resulting system structure may be regarded as linear time-varying for observability purposes, from which a Kalman filter follows naturally. Simulation results are included that illustrate the performance of the proposed solution.

A Survey of P2P Virtual World Infrastructure

With the development of computer science and virtual reality technology, virtual world evolves along the way of computer game development, from arcade games, console system games, LAN games, Internet connectivity games, unstructured games, games with player generation of content, worlds with designer-provided objectives, games with social networks, and open virtual worlds [1]. Traditional server-client structure does not scale well at least in the following three aspects which are limited number of players in each server, single point of failure risk, and unbalanced computation resource. This survey investigates another alternative, peer-to-peer (P2P) virtual world software infrastructure, to address these traditional architectural issues.

A signal strength priority based position estimation for mobile platforms

Global Positioning System (GPS) products help to navigate while driving, hiking, boating, and flying. GPS uses a combination of orbiting satellites to determine position coordinates. This works great in most outdoor areas, but the satellite signals are not strong enough to penetrate inside most indoor environments. As a result, a new strain of indoor positioning technologies that make use of 802.11 wireless LANs (WLAN) is beginning to appear on the market. In WLAN positioning the system either monitors propagation delays between wireless access points and wireless device users to apply trilateration techniques or it maintains the database of location-specific signal fingerprints which is used to identify the most likely match of incoming signal data with those preliminary surveyed and saved in the database. In this paper we investigate the issue of deploying WLAN positioning software on mobile platforms with typically limited computational resources. We suggest a novel received signal strength rank order based location estimation system to reduce computational loads with a robust performance. The proposed system performance is compared to conventional approaches.

Integrity monitoring in WLAN positioning systems

Indoor Positioning Systems using WLANs have become very popular in recent years. These systems are spawning a new class of applications like activity recognition, surveillance, context aware computing and location based services. While Global Positioning System (GPS) is the natural choice for providing navigation in outdoor environment, the urban environment places a significant challenge for positioning using GPS. The GPS signals can be significantly attenuated, and often completely blocked, inside buildings or in urban canyons. As the performance of GPS in indoor environments is not satisfactory, indoor positioning systems based on location fingerprinting of WLANs is being suggested as a viable alternative. The Indoor WLAN Positioning Systems suffer from several phenomena. One of the problems is the continual availability of access points, which directly affects the positioning accuracy. Integrity monitoring of WLAN localization, which computes WLAN positioning with different sets of access points is proposed as a solution for this problem. The positioning accuracy will be adequate for the sets which do not contain faulty or the access points which are offline, while the sets with such access points will fail and they will report random and inaccurate results. The proposed method identifies proper sets and identifies the rogue access points using prediction trajectories. The combination of prediction and correct access point set selection provides a more accurate result. This paper discusses about integrity monitoring method for WLAN devices and followed by how it monitors and developing the application on mobile platforms.

A land mobile channel modeling in LabVIEW

This paper presents a case study implementation of a fading channel model for a recently introduced Global Positioning System (GPS) simulator from National Instruments. Existing models are discussed and implementation aspects are presented for a model which combines statistical properties of different multipath channels. The NIs GPS simulator is implemented in an open development environment, LabVIEW, which allows an incorporation of user-defined models. Computational optimization issues are also discussed.

Fast Massive Preventive Security and Information Communication Systems

We present a fast massive information communication system for data collection from distributive sources such as cell phone users. As a very important application one can mention preventive notification systems when timely notification and evidence communication may help to improve safety and security through wide public involvement by ensuring easy-to-access and easy-to-communicate information systems. The technology significantly simplifies the response to the events and will help e.g. special agencies to gather crucial information in time and respond as quickly as possible. Cellular phones are nowadays affordable for most of the residents and became a common personal accessory. The paper describes several ways to design such systems including existing internet access capabilities of cell phones or downloadable specialized software. We provide examples of such designs. The main idea is in structuring information in predetermined way and communicating data through a centralized gate-server which will automatically process information and forward it to a proper destination. The gate-server eliminates a need in knowing contact data and specific local community infrastructure. All the cell phones will have self-localizing capability according to FCC E911 mandate, thus the communicated information can be further tagged automatically by location and time information.

Event-triggered course-tracking control of marine surface vessels

This paper proposes an event-triggered course-tracking control approach of marine surface vessels based on output reference tracking method. Throughout this work, a reference system, which consists in the continuously controlled version of the system understudy, is employed. Based on the difference between the state of the event-triggered system and that of the reference system, a Lyapunov-like function is defined to guarantee the boundedness of the tracking error. The proposed strategy reduces the amount of energy consumption and computation, thus results in less controller executions, and its feasibility is further verified by the exclusion of Zeno behavior. Effectiveness of the proposed algorithm is further illustrated by simulation results.