Inverse Kinematic Control of a Dual Crane System Experiencing Base Motion

For over 30 years, many active and passive antipendulation concepts have been explored for use on cranes in the marine environment. These range from simple tension member restraints to command filtering strategies and advanced feedback control laws, where both measured ship/platform motion and payload swing are required. Single crane control systems that compensate for own ship or target ship motion and payload swing damping are well developed, and have been demonstrated. Cargo transfer control is more complex when multiple ship-mounted cranes are used, representing a closed kinematic chain. However, the potential benefits include larger capacity and better load control. In this brief, an inverse kinematic control strategy is presented that uses two cranes' actuation capability (hoist lengths and boom angles) to keep its load fixed in inertial space regardless of the motion of the ship on which the cranes are mounted. An underdetermined solution is developed. Unique crane commands can then be computed using a minimum norm solution. A dynamic simulation is described for use in algorithm development and initial validation. Final verification was performed using two cranes mounted on a motion controlled platform.