In designing the ALS and conducting experimental trials, the ALS team used a combination of hardware, software and algorithms for perception, planning and control.

The ALS hardware subsystem consists of the servo-controlled excavator, on-board computing system, perception sensors and associated electronics. During development of the system, the NREC team developed a laser-based scanning system that would be able to penetrate a reasonable amount of dust and smoke in the air. Additionally, the team developed two different time-of-flight scanning ladar systems that are impervious to ambient dust conditions.

The NREC team designed the software subsystem with several modules to process sensor data, recognize the truck, select digging and dumping locations, move the excavator’s joints, and guard against collision.

Planning and control algorithms decide how to work the dig face, deposit material in the truck, and move the bucket between the two. Perception algorithms process the sensor data and provide information about the work environment to the system’s planning algorithms.

Expert operator knowledge was encoded into templates called scripts, which were adjusted using simple kinematic and dynamic rules to generate very fast machine motions. The system was fully implemented and demonstrated on a 25-ton hydraulic excavator and succeeded in loading trucks at about 80% of the speed of an expert human operator.