Requirements and system design for a robot performing selective cleaning in young forest stands

Cleaning is a silvicultural tending operation, primarily aimed at improving the growing conditions of the remaining trees in young stands (ca. 3 m of height). The cost of cleaning has increased in comparison to other forest operations, and the annually cleaned area has decreased in Sweden. Therefore, cleaning with robots might be the key to improve profitability. This paper aims at assessing some design requirements, and suggesting an architecture for a robot cleaning in young forest stands, based on reviewed literature and our own research. The results of cleaning performed by robots have to reach acceptable results and be done at a competitive cost. The robot has to find, select, and handle trees in the whole assigned area according to given instructions. Furthermore, it must be safe for humans, capable of moving safely within the forest environment, and be able to handle snow and other prevalent boreal weather conditions. The vehicle’s size and mass are of importance, and bear on its ability to manoeuvre among remaining stems. Generally, the robot must be capable of operating independently and unattended for several hours in a dynamic and non-deterministic environment. Obstacle avoidance and target identification are identified as the most difficult problems. Machine vision, radar, and laser scanners are promising techniques for both obstacle avoidance, tree identification, and tool control. The proposed architecture is based on a hybrid between the reactive and the hierarchical robot paradigms.