GPS Equipamento de Mina

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Journal of Safety Research 34 (2003) 175 – 181 Preventing collisions involving surface mining equipment: a GPS-based approach Todd M. Ruff a,*, Thomas P. Holden b a Spokane Research Laboratory, National Institute for Occupational Safety and Health, 315 East Montgometry Avenue, Spokane, WA 99207, USA b Trimble, Sunnyvale, 645 N. Mary Ave. 94088, CA, USA Received 28 June 2002; accepted 30 September 2002 Abstract Problem: An average of three workers a year
  Preventing collisions involving surface mining equipment:a GPS-based approach Todd M. Ruff   a, *, Thomas P. Holden  b a  Spokane Research Laboratory, National Institute for Occupational Safety and Health, 315 East Montgometry Avenue, Spokane, WA 99207, USA  b Trimble, Sunnyvale, 645 N. Mary Ave. 94088, CA, USA Received 28 June 2002; accepted 30 September 2002 Abstract  Problem : An average of three workers a year are killed in surface mining operations when a piece of haulage equipment collides withanother smaller vehicle or a worker on foot. Another three workers are killed each year when haulage equipment backs over the edge of a dump point or stockpile. Devices to monitor the blind areas of mining equipment are needed to provide a warning to operators when a vehicle, person, or change in terrain is near the equipment.  Method  : A proximity warning system (PWS) based on the global positioning system (GPS)and peer-to-peer communication has been developed to prevent collisions between mining equipment, small vehicles, and stationarystructures.  Results : A final system was demonstrated using one off-highway haul truck, three smaller vehicles, and various stationary structuresat a surface mining operation. The system successfully displayed the location of nearby vehicles and stationary structures and provided visualand audible warnings to the equipment operator when they were within a preset distance.  Summary : Many surface mining operations alreadyuse GPS technology on their mobile equipment for tracking and dispatch. Our tests have shown that it is feasible to add proximity warning tothese existing systems as a safety feature. Larger scale and long-term tests are needed to prove the technology adequately.  Impact on Industry :A PWSs that incorporates a combination of technologies could significantly reduce accidents that involve collisions or driving over an edge at surface mining operations. D  2002 National Safety Council and Elsevier Science Ltd. All rights reserved.  Keywords:  Proximity warning system; Collision; Global positioning system; Haulage equipment; Surface mining; Blind spots 1. Introduction Each year, there are an average of 20 accidents and threefatalities involving collisions between a piece of surfacemining haulage equipment and either a smaller vehicle or aworker on foot or some other object. Another 21 accidentsoccur and three mining equipment operators are killed eachyearwhentheirequipmentbacksovertheedgeofanembank-ment, stockpile, or dump point  (Fesak, Breland, & Spadaro,1996; Mine Safety and Health Administration [MSHA],2002). These accidents are caused by the operator’s limitedvisibility from the cab of the equipment. In mining opera-tions, these accidents most often involve large, off-highwaydumptrucks.Theareasthatanequipmentoperatorcannotseewhile seated in the cab of these trucks can be extensive,dependingonthesizeandtypeofequipment.Fig.1showsthe blind areas around a 50-ton-capacity dump truck common inconstructionandsandandgraveloperations.Thegrayshadedarea outside of the truck outline shows those areas where thetruckoperatorcannotseea1.8-m-tallperson.Largertrucks— upto360-toncapacity—arecommoninmining,andtheblindareas for these trucks can extend 12 m in front of the truck.Blind areas to the rear and right side can be even larger.Researchers at the National Institute for OccupationalSafety and Health (NIOSH) are investigating methods toreduce accidents attributed to the lack of visibility aroundmining equipment. Many technologies exist that can pro-vide an operator with information on unseen objects or workers near the equipment, including video cameras,sensors, and mirrors. Many of these technologies have been popular in other industries, such as ultrasonic sensors in theautomotive industry and video cameras on recreationalvehicles, but very few have been successfully applied tomining equipment. Other technologies are being developedto address this problem and include electromagnetic signal 0022-4375/02/$ - see front matter   D  2002 National Safety Council and Elsevier Science Ltd. All rights reserved.doi:10.1016/S0022-4375(02)00074-9* Corresponding author. Tel.: +1-509-354-8053; fax: +1-509-354-8099.  E-mail address: (T.M. Ruff) www.nsc.orgJournal of Safety Research 34 (2003) 175–181  detection and radar  (Ruff, 2001). All of these technologies show promise for use on mining equipment; however,further development is needed to overcome the challengesassociated with the harsh environment of mining and thesize of the equipment being used.Global positioning system (GPS) technology also shows promise for this application. Many surface mines already useGPS on equipment for tracking, dispatch, and control. Alogical next step for this technology is to use it to track equipment, workers, and stationary structures and provide awarning when the possibility of a collision exists. The NIOSH Spokane Research Laboratory, Spokane, WA, incooperation with Trimble, 1 Sunnyvale, CA, has developeda new system based on GPS technology that will provide anequipment operator with information on all other vehicles,stationary obstacles, and dump points near the machine. 2. System concept The concept for GPS-based proximity warning for min-ing equipment entails the use of differential GPS receiversand radios on all equipment having reduced visibility, allsmaller vehicles on the mine site, and all workers on foot.As illustrated in Fig. 2, the location of all moving objects must be determined and updated in real time, and thisinformation must be transmitted to all nearby equipment  Fig. 1. Gray areas indicate where driver cannot see a 1.8-m-tall person from cab of a 50-ton-capacity dump truck. 1 Mention of specific products or manufacturers does not implyendorsement by NIOSH. Fig. 2. The PWS concept. T.M. Ruff, T.P. Holden / Journal of Safety Research 34 (2003) 175–181 176  so that the equipment operators are aware of other vehiclesor workers nearby. In addition, the location of stationarystructures, such as buildings, utility poles, and dump points,are stored in a database of potential obstacles. An alarminterface in the cab is required to provide a visual andaudible warning when another vehicle, worker, or stationaryobstacle is within a preset danger zone around the equip-ment.The advantages of using GPS technology for proximitywarnings at mining facilities include (a) the ability to use theexisting GPS infrastructure at many mines, (b) the system’saccurate location and tracking abilities, (c) low-to-zerooccurrence of false alarms, (d) the capability of the systemto identify obstacles, and (e) the ability to customize the user interface and warning zones.Development of a GPS-based proximity warning system(PWS) by NIOSH and Trimble began in 2000. Prototypeswere tested in an outdoor laboratory setting on passenger vehicles (Holden & Ruff, 2001). Development has pro- gressed over the last 2 years, resulting in a mine-readysystem that was demonstrated at the Phelps Dodge Morenci,copper mining operation in April of 2002. 3. Prototype system 3.1. System description A prototype system was constructed to demonstrate that the idea of GPS-based proximity warning was feasible.Readily available components were used to keep costs at aminimum. Each system consisted of a laptop computer to:(a) collect, process, and transmit data, (b) run the PWSsoftware, and (c) provide a display for the vehicle operator.A PCMCIAwireless network card (IEEE 802.11b) was usedto communicate between laptops. An off-the-shelf, 12-channel, differential GPS receiver and antenna were usedto determine location. A Coast Guard beacon was used to provide differential correction. Two complete systems weremounted in two different passenger cars for dynamic tests. 3.2. Test description and results As described in Holden and Ruff (2001), the prototype system went through a series of operational and perform-ance tests using two vehicles—a local vehicle and a remoteroving vehicle. The goal of the operational tests was toverify the operation of the various pieces as compared to thedefined specifications of the system. These specificationsincluded the ability to set up, control, and monitor the GPSreceiver properly, and the ability to send and receiveinformation over a wireless local area network (LAN)connection.One key factor was to determine the reliable transmissionrange of the wireless LAN. Maximum (11 Mbps) andminimum (1 Mbps) signaling rates were tested using thePWS software running on two laptops with wireless LANcards installed. Each LAN card had a dual-patch diversityantenna directly mounted on it. The system functioned verywell and had no packet losses when the two vehicles wereseparated by distances under 60 m. Beyond 60 m, perform-ance declined. The ranges where transmission completelystopped were 120 m for the 11-Mbps signal and 220 m for the 1-Mbps signal. It was evident that the quality of signalreception was a function of range, antenna properties, andline-of-sight to the transceiver. Note that the wireless net-work antennas were connected to the PCMCIA cards, soantenna type and placement was limited. Signal receptioncan be made more reliable by using a better antennamounted on the exterior of the vehicle.Another important test of the wireless communicationswas the time-to-associate measure for a new vehicle enter-ing a local area. At ranges of up to 60 m, the new vehicleassociated, or was recognized by the PWS, in less than 1 s.Outside 60 m, the vehicle’s time-to-associate was related tosignal quality.A second set of tests evaluated the performance of thesystem and covered the following items:1. ability of the PWS to transfer information accurately,which was measured by matching received data from aremote vehicle and data from the local vehicle using GPStime tags,2. latency of the remote vehicle information,3. accuracy of the real-time vehicle position,4. response to various dynamics of the remote vehicle, and5. response to various dynamics of the local vehicle.Provided that the communications link between thevehicles was functioning, the local vehicle’s PWS was ableto follow the trajectory of the remote vehicle according tothe transmitted information. Errors were determined bymatching real-time data stored by the remote system withthe perceived remote data recorded by the local PWS usinga GPS time mark corresponding to the transmitted informa-tion. Essentially, the information was matched in time so alllatency errors were removed. These results showed that theerrors introduced to the system by corrupt data transmis-sions were negligible, as no errors of significance wereobserved.The latency of the information presented to an operator corresponds to errors in the actual position of the remotevehicle. Latency-induced error is dependent upon the veloc-ity of the remote vehicle. Latency can be determined byspecial methods to roughly 0.2 s, assuming a broadcast rateof 4 Hz. In the tests, observed latency correlated well withthis value. Additional sources of latency could be attributedto radio and processing delay. Overall, the system wasmeasured to have a latency of less than 0.5 s.Fig. 3 shows that radio coverage for these particular wireless network cards was excellent within a 100-m range.The position of the stationary local vehicle is near the T.M. Ruff, T.P. Holden / Journal of Safety Research 34 (2003) 175–181  177  middle right of the figure (black dot). The thin line is theactual trajectory of the remote vehicle, and the dots are the perceived positions. Areas where the line is not coveredresulted from communications interference from largeobstacles. This demonstrates the line-of-sight nature of theshort-range radios. Note that the communication gapsoccurred over 100 m from the srcin of the grid.Fig. 4 shows the computed position errors of the movingremote vehicle as perceived by the stationary local vehicle.Errors of less than 2 m are evident. The graphs show that theerrors were very small when the remote vehicle was sta-tionary (flat line), but larger when it was in motion. Theerrors can be attributed to position update latency, but arewithin the desired specifications. 4. Mine-ready system 4.1. System description Tests of the prototype system showed that the concept of a GPS-based PWS was feasible; however, the system had to be redesigned using components that could be used onmining equipment. The mine-ready PWS consisted of thefollowing Trimble components: (a) a GPS antenna, (b) aWindows CE-based computer with LCD display to run thePWS software, (c) an eight-channel, single-frequency, dif-ferential GPS receiver (integrated into the computer enclo-sure), and (d) a SiteNet 900-MHz Internet Protocol (IP)radio. All of these components were designed for mountingon heavy equipment.The mine-ready PWS operates in a similar manner to the prototype system, but with a few modifications. As before,GPS is used to determine the location of the vehicle onwhich a system is mounted. Differential correction informa-tion from a base station is also received by the PWS. Thecorrected location of that vehicle is then transmitted once per second via the IP radio to all other vehicles in the areaequipped with a PWS. The locations of other vehicles arealso received by the IP radio and shown on the computer’sdisplay if they are within a specified range. The location of stationary obstacles, such as dump points, power lines, andmine buildings, does not have to be transmitted. Their coordinates can be entered into the system database so that they show up on the vehicle’s display. 4.2. Test description and results For tests at the Phelps Dodge Morenci Copper Mine, acomplete PWS was installed on each of the followingequipment: Caterpillar 797 360-ton capacity haul truck (Fig. 5), Caterpillar rubber-tire dozer  (Fig. 5), and two service trucks (pickups). A base station was also installed Fig. 4. Geodetic position error of moving vehicle computed at local vehicle. Fig. 5. PWS equipment installed on a Caterpillar haul truck and dozer.Fig. 3. Top view of remote vehicle’s path as perceived by local stationaryvehicle. T.M. Ruff, T.P. Holden / Journal of Safety Research 34 (2003) 175–181 178
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