The Industrial Control of Tower Cranes: An Operator-in-the-Loop Approach [Applications in Control]

This article reports on the development of a controller for the real-time assistance of crane operators in the field of construction, in partnership with Manitowoc (Potain Cranes), a crane manufacturer. Owing to the complexity of construction sites, which notably involve men at work, full automation is deemed undesirable, and operators must be kept in the loop. The goal of the controller is then to track the velocity reference from the operator while guaranteeing the absence of sway (that is, undesirable, residual oscillations). The method uses only built-in crane sensors, and as a result, the state is unobservable and the method is largely open loop. It builds on the celebrated flatness theory coupled with a hierarchical control architecture based on a time-scale separation, where modern variable-speed drives ensure the fast closed-loop control of motor speeds (whereas the method allows for the generation of feedforward, feasible antisway trajectories for the slower mechanical part). The approach is tested on a mockup as well as various cranes, including a 40-m-high tower crane. Tests conducted on crane operators with various levels of experience and one crane instructor confirm the benefits of the controller. Presently, regulatory laws seem to be the main impediment to commercialization.