Semi-autonomous Shared Control for Redundant Forwarder Cranes

Semi–autonomous operation with shared control between the human operator and an autonomous control system has been developed and examined for a forwarder crane. Shared control gives the operator and the autonomous control system simultaneous control over the same task. It also enables smooth transitions between manual and autonomous operation. Operators with professional experience of forwarder crane control as well as inexperienced operators have been engaged in experiments where performance was measured. The experiments were conducted on a forwarder crane of reduced size at Smart Crane Lab, Umeå University. Three levels of automation were evaluated: pure manual operation, semi–autonomous operation with traded control and semi–autonomous operation with shared control. The semi–autonomous operation were examined along with two methods for manual operation: conventional joint control and boom–tip control. The time–efficiency of log loading as well as smoothness of transitions between autonomous and manual operation were examined. The experiments show that with the aid of shared control the performance of the inexperienced operators increases with a factor two as compared to manual joint control. The performance of the professional operators decreases somewhat with shared control as compared to manual joint control. With shared control both professional and inexperienced operators experience a reduction in workload. Smoothness of transitions were found satisfactory.

Related publications and simulation scripts.

• Hansson A. and Servin M. Semi-autonomous shared control of large-scale manipulator arms. Control Engineering Practice 18(9):1069-1076 (2010)
• Hansson A. Shared Control of Mechanical Systems in Virtual Environments. MSc thesis, Umeå University (2009)
• Simulation scripts: grippingBoxes, craneSimulation, monitorControl (zip)