Operation of the Single-Grip Harvester: Motor-Sensory and Cognitive Work

Abstract

This article describes the interface between a one-grip harvester and its operator as it relates to motor-sensory and cognitive activities of the operator when carrying out thinning and regeneration harvesting in Sweden. Work tasks are described, as are operator data gathering, cognitive and motor-sensory processes. Descriptions of motor- sensory inputs and control manipulation are based on digital data gathering from machine controls combined with parallel, multi-camera video taping of work activities. Work element descriptions, data gathering and cognitive processes were inferred based on interviews with 20 operators and operator instructors. Work features found to limit an operator’s efficiency were: few breaks in the work; very intensive handling of controls (4000 control inputs per hour in our study) due to lack of automatic functions in the boom and harvester head; restricted view from the cab; lack of information about the stand and log; and skewed and twisted work postures. The main part of the operator’s cognitive work was found to be done through automated skills. The experienced operator acts upon the global situation and seldom analyses it explicitly. Their chunks of information (memory aggregates recognized in toto) guide them in what to do, and usually they see only one course of action to follow in a particular situation. Key future technical development needs and opportunities include additional automation to reduce operator control inputs, developing means of improving visibility such as 3-D laser scanning and additional use of stand inventory and historical data about log properties to improve automation of cross-cutting. One of the key future research areas regarding training and robotization is to determine the data contained in the ‘chunks’ of information used by operators in making machine location, harvesting and processing decisions.