Benefits of assessing line-of-sight from a LHD vehicle in a virtual environment
Load-haul-dump vehicles (LHDs) are extensively used in underground mining, however, equipment design and operating conditions contribute to restricted operator sight lines. The inability to clearly see people, objects, or hazards around the machine has contributed to a number of accidents including fatal injuries. In order to identify vehicle design characteristics resulting in restricted and blocked sightlines, line-of-sight assessments are traditionally completed in the field. However, field methods are unable to evaluate line-of-sight under dynamic operating conditions, and are limited in their ability to provide feedback on the impact of various operator characteristics such as sitting height. Results of this research show computer simulation and virtual reality can be successfully used to evaluate line-of-sight during the operation of LHD vehicles. In order to benefit from virtual reality applications, the work environment, LHD vehicle, and human posture need to be represented as accurately as possible. A computer simulation program with ergonomic analysis features, Classic JACK 3.1, was successfully used. Three-dimensional CAD models of LHDs were developed from manufacturer specifications and pictures taken from LHDs currently in use. The LHD models were imported into the JACK environment, a digital human was positioned in the cab of the LHD vehicle, and the vehicle and human where driven over a typical mine route. Real-time feedback in the JACK program was used to identify what the operator could see under different operating conditions. Machine characteristics and operating scenarios resulting in impaired line-of-sight were successfully identified with this method.Based on the results of the line-of-sight improvements pre/post LHD vehicle modifications, the following design recommendations were identified:
Orient cab post to open sight lines to the left front corner of the LHD vehicle.
Decrease thickness of lights and light brackets.
Utilize a round light and light bracket design on a single post.
Round the cylinders covering the boom and hoses.
Lower the height of the engine profile and/or provide a negative slope to the rear.
Redesign the engine/radiator to angle away at the corners.
Eliminate bucket teeth.
Redesign the bucket to angle away slightly at the corners.
Lower the profile of the mud guards.
Avoid placing remote boxes in areas that restrict line of sight.
Move vents and cylinders that protrude from the top of the machine.
Increase operator sitting height in the cab (if possible).
Allow seat rotation to improve operator sitting comfort
The JACK program could also provide real-time feedback on the human’s joint forces and torques, strength requirements, postural comfort, and metabolic energy expenditure. As a result, this method could also be used to successfully evaluate musculoskeletal injury risk factors along with system design recommendations to improve workplace safety and productivity.The LHD vehicles evaluated with the JACK software package were also combined with mine models and imported into other VR software packages (e.g. Blender) in order to enable viewing in Laurentian University’s virtual reality laboratory (VRL). The VRL enabled the research team to view LHD vehicles operating in simulated underground mining environments in stereo, which provided a better appreciation of spatial vision issues. This approach has proven beneficial when conducting workshops with equipment manufacturers, LHD operators, union representatives, health and safety trainers, and mine planners in an effort to improve awareness of line-of-sight issues during the operation of mobile mining equipment. The feasibility of equipment design modifications and mine layout changes have also been successfully discussed in the virtual reality laboratory.