9 research outputs found
A holonic approach to dynamic manufacturing scheduling
Manufacturing scheduling is a complex combinatorial problem, particularly in distributed and dynamic environments. This paper presents a holonic approach to manufacturing scheduling, where the scheduling functions are distributed by several entities, combining their calculation power and local optimization capability. In this scheduling and control approach, the objective is to achieve fast and dynamic re-scheduling using a scheduling mechanism that evolves dynamically to combine centralized and distributed strategies, improving its responsiveness to emergence, instead of the complex and optimized scheduling algorithms found in traditional approaches
Internet based VRS Code Positioning
Absolute positioning – the real time satellite based positioning technique that relies solely on global navigation satellite systems – lacks accuracy for several real time application domains. To provide increased positioning quality, ground or satellite based augmentation systems can be devised, depending on the extent of the area to cover. The underlying technique – multiple reference station differential positioning – can, in the case of ground systems, be further enhanced through the implementation of the virtual reference station concept.
Our approach is a ground based system made of a small-sized network of three stations where the concept of virtual reference station was implemented. The stations provide code pseudorange corrections, which are combined using a measurement domain approach inversely proportional to the distance from source station to rover. All data links are established trough the Internet
Implementation of a Campus wide DGPS Data Server
Although the Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning
System (GPS) is, de facto, the standard positioning system used in outdoor navigation, it
does not provide, per se, all the features required to perform many outdoor navigational
tasks. The accuracy of the GPS measurements is the most critical issue. The quest for
higher position readings accuracy led to the development, in the late nineties, of the
Differential Global Positioning System (DGPS). The differential GPS method detects
the range errors of the GPS satellites received and broadcasts them. The DGPS/GPS
receivers correlate the DGPS data with the GPS satellite data they are receiving,
granting users increased accuracy. DGPS data is broadcasted using terrestrial radio
beacons, satellites and, more recently, the Internet. Our goal is to have access, within the
ISEP campus, to DGPS correction data.
To achieve this objective we designed and implemented a distributed system
composed of two main modules which are interconnected: a distributed application
responsible for the establishment of the data link over the Internet between the remote
DGPS stations and the campus, and the campus-wide DGPS data server application.
The DGPS data Internet link is provided by a two-tier client/server distributed
application where the server-side is connected to the DGPS station and the client-side is
located at the campus. The second unit, the campus DGPS data server application,
diffuses DGPS data received at the campus via the Intranet and via a wireless data link.
The wireless broadcast is intended for DGPS/GPS portable receivers equipped with an
air interface and the Intranet link is provided for DGPS/GPS receivers with just a RS232
DGPS data interface. While the DGPS data Internet link servers receive the DGPS data
from the DGPS base stations and forward it to the DGPS data Internet link client, the
DGPS data Internet link client outputs the received DGPS data to the campus DGPS
data server application. The distributed system is expected to provide adequate support
for accurate (sub-metric) outdoor campus navigation tasks. This paper describes in
detail the overall distributed application
Real Time Internet DGPS Service
The accuracy of the Navigation Satellite Timing and Ranging
(NAVSTAR) Global Positioning System (GPS) measurements is
insufficient for many outdoor navigation tasks. As a result, in
the late nineties, a new methodology – the Differential GPS
(DGPS) – was developed. The differential approach is based on
the calculation and dissemination of the range errors of the GPS
satellites received. GPS/DGPS receivers correlate the
broadcasted GPS data with the DGPS corrections, granting users
increased accuracy. DGPS data can be disseminated using
terrestrial radio beacons, satellites and, more recently, the
Internet.
Our goal is to provide mobile platforms within our campus
with DGPS data for precise outdoor navigation. To achieve this
objective, we designed and implemented a three-tier
client/server distributed system that establishes Internet links
with remote DGPS sources and performs campus-wide
dissemination of the obtained data. The Internet links are
established between data servers connected to remote DGPS
sources and the client, which is the data input module of the
campus-wide DGPS data provider. The campus DGPS data
provider allows the establishment of both Intranet and wireless
links within the campus. This distributed system is expected to
provide adequate support for accurate (submetric) outdoor
navigation tasks
Evaluation of a real time DGPS data server
The goal of the this paper is to show that the DGPS data Internet service we designed and developed provides campus-wide real time access to Differential GPS (DGPS) data and, thus, supports precise outdoor navigation.
First we describe the developed distributed system in terms of architecture (a three tier client/server application), services provided (real time DGPS data transportation from remote DGPS sources and campus wide data dissemination) and transmission modes implemented (raw and frame mode over TCP and UDP). Then we present and discuss the results obtained and, finally, we draw some conclusions
A formal validation approach for holonic control system specifications
The holonic manufacturing paradigm allows a new approach to the emergent requirements faced by the manufacturing world, through the concepts of modularity, decentralisation, autonomy, re-use of control software components. The formal modelling and validation of the structural and behavioural specifications of holonic control systems assumes a critical role. This paper discusses the formal validation of the Petri Net models designed to represent the behaviour and specifications of the holon classes defined at ADACOR architecture
Real Time Internet DGPS Service
The accuracy of the Navigation Satellite Timing and Ranging
(NAVSTAR) Global Positioning System (GPS) measurements is
insufficient for many outdoor navigation tasks. As a result, in
the late nineties, a new methodology – the Differential GPS
(DGPS) – was developed. The differential approach is based on
the calculation and dissemination of the range errors of the GPS
satellites received. GPS/DGPS receivers correlate the
broadcasted GPS data with the DGPS corrections, granting users
increased accuracy. DGPS data can be disseminated using
terrestrial radio beacons, satellites and, more recently, the
Internet.
Our goal is to provide mobile platforms within our campus
with DGPS data for precise outdoor navigation. To achieve this
objective, we designed and implemented a three-tier
client/server distributed system that establishes Internet links
with remote DGPS sources and performs campus-wide
dissemination of the obtained data. The Internet links are
established between data servers connected to remote DGPS
sources and the client, which is the data input module of the
campus-wide DGPS data provider. The campus DGPS data
provider allows the establishment of both Intranet and wireless
links within the campus. This distributed system is expected to
provide adequate support for accurate (submetric) outdoor
navigation tasks
Implementation of a Campus wide DGPS Data Server
Although the Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning
System (GPS) is, de facto, the standard positioning system used in outdoor navigation, it
does not provide, per se, all the features required to perform many outdoor navigational
tasks. The accuracy of the GPS measurements is the most critical issue. The quest for
higher position readings accuracy led to the development, in the late nineties, of the
Differential Global Positioning System (DGPS). The differential GPS method detects
the range errors of the GPS satellites received and broadcasts them. The DGPS/GPS
receivers correlate the DGPS data with the GPS satellite data they are receiving,
granting users increased accuracy. DGPS data is broadcasted using terrestrial radio
beacons, satellites and, more recently, the Internet. Our goal is to have access, within the
ISEP campus, to DGPS correction data.
To achieve this objective we designed and implemented a distributed system
composed of two main modules which are interconnected: a distributed application
responsible for the establishment of the data link over the Internet between the remote
DGPS stations and the campus, and the campus-wide DGPS data server application.
The DGPS data Internet link is provided by a two-tier client/server distributed
application where the server-side is connected to the DGPS station and the client-side is
located at the campus. The second unit, the campus DGPS data server application,
diffuses DGPS data received at the campus via the Intranet and via a wireless data link.
The wireless broadcast is intended for DGPS/GPS portable receivers equipped with an
air interface and the Intranet link is provided for DGPS/GPS receivers with just a RS232
DGPS data interface. While the DGPS data Internet link servers receive the DGPS data
from the DGPS base stations and forward it to the DGPS data Internet link client, the
DGPS data Internet link client outputs the received DGPS data to the campus DGPS
data server application. The distributed system is expected to provide adequate support
for accurate (sub-metric) outdoor campus navigation tasks. This paper describes in
detail the overall distributed application
An internet DGPS service for precise outdoor navigation
The goal of the work presented in this paper is to provide mobile platforms within our campus with a GPS based data service capable of supporting precise outdoor navigation. This can be achieved by providing campus-wide access to real time Differential GPS (DGPS) data. As a result, we designed and implemented a three-tier distributed system that provides Internet data links between remote DGPS sources and the campus and a campus-wide DGPS data dissemination service. The Internet data link service is a two-tier client/server where the server-side is connected to the DGPS station and the client-side is located at the campus. The campus-wide DGPS data provider disseminates the DGPS data received at the campus via the campus Intranet and via a wireless data link. The wireless broadcast is intended for portable receivers equipped with a DGPS wireless interface and the Intranet link is provided for receivers with a DGPS serial interface. The application is expected to provide adequate support for accurate outdoor campus navigation tasks