Accurate Guidance and Measurement for Excavators using a Laser Scanner

This project has successfully developed and demonstrated a proof-of-concept system that is able to simultaneously
track the bucket of a mining excavator and map the terrain under the boom.

Over a 12 month period, a number of trials were conducted at Blair Athol Mine to:

• install sensors to a Hitachi EX36000 excavator,
• verify the accuracy of the system, and
• collect production data.

In these trials, we were able to demonstrate that:

• the system is able to track the location of the bucket teeth to within 10cm;
• the system is able to generate dynamic Digital Terrain Maps (DTM); and
• the sensors are able to survive over extended periods in the mining environment.

However the systems was not able to

• reliably track the bucket whilst digging (due to a loss of features on the bucket), or
• account for losses in GPS FIX along the bench (appears to be related to vibration).

Fortunately, it is believed that both of these problems can be overcome with further investigation.

One of the key developments made during this project is a novel self calibration technique. This technique is based upon the ability to use the LMS (scanning laser) to simultaneously track the body and bucket of the excavator, and thus estimate the pose of the boom, stick and bucket joints, along with their respective angles. When coupled with the GPS data, it is possible to translate the DTM under the boom into the mine coordinate system. With this technique, it is feasible that the system could be installed and calibrated in less than one day— thus not disrupting the normal operation of an excavator whilst in production.

The most significant outcome of the project is the ability to provide dynamic DTMs underneath the excavator (maps that are updated in real-time). By subtracting the minimum DTM height from the initial DTM height it is possible to estimate how much material has been removed. When compared to the mine survey, it is possible to reconcile what is actually removed. This has an immediate benefit to the open-cut mining industry in that it improves the accuracy of productivity measurements and provides the ability to drill down on the production data to see what has been mined and what has been left behind. Once the bucket tracking technique has been perfected, it will be possible to overlay a “live” simulation of the excavator onto a “live” DTM, providing a valuable visualization tool. This technology, referred to as augmented virtualization, has application in Dig-to-Plan and Tele-Robotic control of the excavator.