Emergency Braking Control Design for a Dual Cart-Trolley Overhead Crane

Overhead cranes are machines typically used in transportation industries for carrying heavy loads. The typical problem in overhead cranes, also known as the anti-swing control problem, deals with minimizing the payload swing during the travel of the overhead crane. However, recent literature has reported another problem keeping in view industrial safety requirements- namely, the emergency braking problem. This problem deals with the development of control laws to ensure sufficiently fast cart braking to avoid collisions with objects in the path of the crane or payload while maintaining minimal payload swing. This problem is difficult given its contradictory objectives, i.e. quick cart braking and minimization of payload swing. In this paper, we propose a dual cart-trolley system- i.e. a trolley inside a cart to which the payload is suspended and we demonstrate emergency braking to avoid collisions with objects for such a system. The system is modeled as a single pendulum ignoring effects of payload swing relative to the cable to maintain simplicity. A sliding mode controller is used to achieve emergency braking in the presence of external disturbances, parameter uncertainties and varying initial conditions. The future prospects of this work are enormous. Given that this system falls in the same class of systems as drones carrying payloads, and drones often require halting in emergency scenarios, this work may be applied to drones in the future.