HEAP - The autonomous walking excavator

TLDR

Automation demand in construction is unmatched, driven by sustainability, safety, and labor shortages. The article describes converting an off‑the‑shelf excavator into an autonomous robotic system and outlines its potential for trench digging, stone wall assembly, forestry work, and semi‑autonomous teleoperation. The system integrates leg actuation, sensor suites including GNSS‑RTK, solves state estimation for a wheeled‑legged robot, and implements controllers for driving, balancing, and arm motion to achieve full autonomy. An autonomous walking excavator was successfully developed, illustrating the feasibility of such conversion, and the authors provide development insights and future research directions.

Abstract

The demand and the potential for automation in the construction sector is unmatched, particularly for increasing environmental sustainability, improving worker safety and reducing labor shortages. We have developed an autonomous walking excavator - based one of the most versatile machines found on construction sites - as one way to begin fulfilling this potential. This article describes the process of converting an off-the-shelf construction machine into an autonomous robotic system. First we outline the necessary sensing equipment for full autonomy and the novel actuation of the legs, and compare three different complementary actuation principles for the excavator's arm. Second, we solve the state estimation problem for a general wheeled-legged robot. Beside kinematic measurements, it includes GNSS-RTK, to absolutely reference the machine on a construction site. Third, we developed individual controllers for driving, chassis balancing and arm motions allowing for fully autonomous operation. Lastly, we highlight the machine's potential in four different real-world applications, e.g. autonomous trench digging, autonomous assembly of dry stone walls, autonomous forestry work and semi-autonomous teleoperation. On top, we also share some development insights and possible future research directions.