This thesis studies the operation of a large hydraulic excavator (an O&K RH200) from data obtained by monitoring the machine during a regular operation period. The objective of the work is to build an understanding of how machine usage affects performance, extending across both productivity and maintenance issues.
The results suggest that operator digging style is a significant factor in determining machine performance. Two dominant digging styles are identified, characterized by the trajectory of the bucket teeth. In the first style, the operator commands the bucket along the pit-floor, teeth pointing downward, the full face of the bucket exposed to the dig material. The net effect is a 'scooping' action on the material, forcing it into the bucket. This approach was found to result in higher bucket fills at the expense of higher machine duty. In the alternative style, the bucket enters higher in the muck-pile. After
initial penetration, the bucket is rolled as it is lifted, so that rilling of the dig material assists the fill. This approach was found to yield lower fills but cause less damage.
Four operators worked on the machine during the monitoring period. Their philosophy towards machine use was found to be linked to a digging technique. One operator set out to achieve high per-pass productivity and did so at the cost of high per-cycle damage. He used the first style almost exclusively. Two operators were sympathetic to the trade-off between performance and duty. They used the second style. They had lower per-pass productivity, but compensated for this by lower per-cycle damage. The fourth operator was a trainee. His inexperience manifested itself in low productivity, high variability, and high rates of machine damage. He favored the second style.
These findings shed fight on machine operation and contribute towards the development of a
performance and duty monitor for large hydraulic excavators.