Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, TN 397, 1992 Apr; :1-4
Objective: Develop and evaluate a mechanical position and heading system (MPHS) that provides information about underground mining machine position and heading to aid in the remote positioning of mining machines during face maneuvers. Background: While great improvements have been made in mineworker safety, progressive technology continues to create a safer, better working environment for miners by keeping them away from the dangerous face area. In maintaining such high standards of safety, the Bureau is investigating remote, computer-assisted operation of mining systems for underground, high wall, and surface mining applications. A key component of computer-assisted operation is a guidance system. Since there are no guidance systems on any commercial continuous mining machines, the Bureau itself developed and tested the mechanical position and heading system (MPHS). The MPHS is based on linear position transducers (LPT's), and operates on principles of triangulation to provide machine position (xy coordinate), and orientation in the xy plane (yaw or heading). These data are needed in order to keep the continuous mining machine in proper alignment before and during the cutting cycle. The MPHS theory development is in three parts: characterize the sensors used and their configuration; select and define the navigation reference frames; and derive a closed-form solution for determining the position and heading from sensor information. Application of the MPHS theory required the development of hardware, software, and system interfaces. The Bureau's MPHS measurement hardware configuration consists of mounts, LPT's, cabling, a computer enclosure, and a data collection computer. The MPHS software was written in computer languages PL/M-51 and ASM-51. The MPHS system interfaces to a distributed computer network that the Bureau integrated to a mining machine for computer-assisted control. Approach: The Bureau, in cooperation with a West Virginia mine, tested the MPHS underground on a commercially-available continuous mining machine. The MPHS's sensory system had four LPT's in stationary positions on the machine tested. The wires of these LPT's attached to two points on the continuous mining machine. The MPHS controller processes the linear distance sensor data in the computer enclosure, giving the continuous mining machines position and heading. During the underground mine experiment, the LPT was wired to a mounting system setup in the entry behind the mining machine and connected to anchor points on the mining machine. Intrinsically safe cables connected the LPT's to the computer enclosure located in fresh air. Then a communication cable connected the computer enclosure to the control room where the data collection computer resided. The experimental procedure examined a four-pass advance. The entry width and depth were 6 m and 9.75 m, respectively. The mining machine operator directed the mining machine to mine this block of coal with the radio control pendant. The data collection computer took MPHS data during the mining operation at 1-s intervals. A laser transit took the mining machine position data during each pause in operation by sighting reflectors on the attachment posts. Using the' time stamps on both the MPHS and the transit data, the researchers compared the data to confirm the MPHS's accuracy. Test Results: The two graphs show the results of the forward advance experiment during the second cut. The top graph shows the position and heading information provided by the MPHS during the cut.. The bottom figure shows the MPHS calculated confidence. Another figure shows the MPHS vs. Transit position and heading accuracy for the first two cuts. The accuracy of data resulting from the experiments shows several interesting results: 1. The x and y values change slightly during pivots due to slippage and the uncertain location of the continuous mining machine's center of rotation. 2. The confidence supplied by the MPHS for the first two cuts averaged 86%, a much better accuracy than the allowable tolerances of +/- 76.2 mm for x and y position and +/- 0.026 rad for heading. 3. Table 1 shows the transit verified accuracy for the first two-pass cuts which support the high confidence levels supplied by the MPHS. The Bureau-developed MPHS works reliably under field conditions. The MPHS yields position, heading, status, and confidence data in response to linear position transducer (LPT) data. The confidence supplied with each position and heading calculation reflects the actual system accuracy. The system accuracy, obtained by transit measurement, is better than 35.2 mm in X, 52.5 mm in y, and 0.0106 rad in heading. While errors incurred by the MPHS are acceptable in a mining environment, there exist better LPT transducers that could further improve accuracy.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, TN 397