Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, TN 425, 1993 Nov; :1-2
Objective: Develop computer software that can aid in improving the visibility and illumination in underground mines by providing quick analysis of existing equipment and conditions and the effects of potential modifications. Background: Poor visibility and illumination are common problems in underground mining. Mining equipment often restricts operators' fields of vision. Also, lighting systems are often positioned where they cause excessive glare, which restricts the visibility around the machines even further. To help address these problems, the U.S. Bureau of Mines (USBM) has developed a PC-based software package to analyze certain human engineering aspects (ergonomics) of mining equipment design. The software is available for use by equipment manufacturers and mining companies for design work on new machines, as well as for evaluating proposed modifications to existing machines. Approach: The Crewstation Analysis Programs (CAP) package includes assessments of visibility, illumination, and glare in the surrounding work area. The advantage of using computers for these types of analyses is that numerous design iterations can be tested quickly and efficiently to determine the effects of changes on visibility. This cuts down the need for expensive testing using physical mockups. Another advantage is that design ideas can be tested in situations where testing would not normally be possible. For instance, the effects of modifications to a lighting system or canopy design could be tested while the machine remained in service. How CAP Works: Visibility to quantify visual requirements for underground mining equipment, the USBM has developed a methodology that defines specific points in the fore-aft, lateral, and vertical planes that must be visible to the operator. These points, called visual attention locations (VALS), are defined in reference to specific locations on the machine or in relation to the operator. This approach allows the VALS to be applied to all configurations of a particular equipment class. For instance, a shuttle car operator must have an unobstructed view of the front edge of the car when lining up under the tail boom of a continuous mining machine to load coal. The location of the VAL associated with this requirement can be described as the front edge of the machine, along the machine center line, at the operator's eye height. With this methodology, the procedure to compute a VAL location remains the same regardless of the length and height of the equipment or the operator's position. Therefore, the VAL is applicable to all equipment in the shuttle car class. The CAP visibility model automates the task of determining whether the required VALS are visible to a selected human operator. The output is a relative visibility rating for the machine, which can be compared with results of alternative machine designs. CAP also provides both graphical and tabular output to pinpoint any machine parts that obstruct visibility. Illumination and glare: Because of the perpetual darkness of the underground environment, illumination is a factor that must be considered when designing equipment for optimal visibility. Accordingly, Federal regulations specify that certain surfaces within a miner's normal field of vision must be illuminated to 0.06 footlambert (0.2 candela per square meter) while self-propelled mining equipment is being operated. Unfortunately, in attempting to meet these illumination standards, mine equipment designers often aggravate another mine lighting problem-glare. There are currently no standards related to glare in underground mining. Regulations state only that designers should attempt to minimize glare when developing machine illumination systems. Obviously, performing all of the calculations required to compute glare for a multitude of machine and lamp types, with the possible combinations running into the thousands, is too tedious and costly to be practical using manual methods. The result is that the designer is impeded significantly in solving for an optimal illumination system that minimizes glare. The CAP illumination model eliminates these problems by turning the computational portion of the lighting design task over to the computer. The software allows the lighting designer to concentrate on adjusting the configuration of the illumination system to minimize the potential for glare while still providing enough illumination to conform to Federal regulations. Specifically, CAP displays a three-dimensional representation of the mining machine, allows the user to input a lighting system, and then calculates the level of illumination in designated areas surrounding the machine. Using these values of illumination, the user may perform "disability glare" comparisons by calculating the luminance contrast of objects of interest along selected lines of sight. The luminance contrast is the relationship of the luminance of an object to its immediate background. In an underground coal mine, the background is usually the walls, floor, or roof of the tunnel being mined, which has a known luminance value.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, TN 425