SUMMARY

Cranes are widely used in material-handling and transportation applications, e.g. in shipyards, construction sites, and warehouses. They are critical to the economic vitality of modern-day industries. Therefore, improving crane performance and ease of use are important contributors to industrial productivity, low production costs, and workplace safety. In a typical crane operation, a payload is lifted, moved to its destination, and then lowered into place. This dissertation aims to improve crane performance and reduce task difficulty for the human operator in the movements mentioned above, namely, 1) Moving the payload in the horizontal plane, 2) Lifting the payload off the ground/floor, and 3) Lowering or laying down the payload at its destination. The design of a novel and intuitive human-machine control interface is the focus for improving operations that involve laterally moving the payload. The interface allows operators to drive a crane by simply moving a hand-held device through the desired path. The position of the device, which is tracked by sensors, is used to generate a command signal to drive the crane. This command is then shaped such that payload oscillations are greatly reduced, making it much easier for the operator to drive the crane. Facets of this new mode of crane control are examined, e.g. control structure and stability, usability contexts, modes of operation, and quantitative measures (by means of human operator studies) of improvement over standard crane control interfaces. Lifting up a payload can be extremely difficult if the hoist is not properly centered above the payload. In these potentially dangerous and costly situations (called off-centered lifts), the payload may slide on the ground and/or oscillate in the air after it is hoisted. Newtonian-based models that focus on the contact dynamics (stiction-sliding-separation) were derived and experimentally verified to study off-centered lifts. Then, with the goal of aiding operators, simple but practical, automated, self-centering control solutions are proposed and implemented. Laying down or lowering a payload can also be very challenging for operators in certain situations, e.g. laying down a long, distributed payload (e.g. a 30' aluminum ingot) from a vertical orientation to a horizontal position. Newtonian-based models were derived to describe this lay-down scenario. The forces and motions experienced by the payload are then used to guide the process of determining proper trajectories and motions that the crane and payload should follow.