Knuckle Boom Crane

Cranes are extensively used in offshore for complex lifting operations. In this example, a control system for a knuckle boom crane has been developed. The crane has to lift various loads from the ship deck and drop them into the sea. Because of the sea swell the crane will move up and down. As a results the load, when under water will move up and down heavily.

To prevent this heave compensation is required. Traditional heave compensation will use the winch system to compensate for the swell. However, the repeated motion will wear off the hoisting cable. Modern heave compensation methods will use the crane itself to compensate for the swell. This requires a complex control system with inverse kinematics of the crane. For the testing of this controller a HIL simulator has been developed, which was extended with an operator unit and a visualization module to work as a training simulator. 

Setup

The crane control system is running on a Bachmann M1 controller. The controller is steered using a radio controlled operator terminal that is connected to the control system using a CAN bus. The controller is connected via Ethernet (using an open Bachmann bus protocol) with a windows PC. On the PC the package 20-sim is running the plant model. The visualization engine of 20-sim has been used to display a 3D view of the crane and ship. 

Plant Model

The crane was modeled in 20-sim using the 3D Mechanics editor to develop the 3D parts of the crane. Standard libraries were used to model the hydraulic drive system of the crane and the ships movement. An addtional component was used in 20-sim to support the visualization.

Test

The HIL simulator has been extensively used to detect errors in the control system and test the proper operation. Extension with the operator unit showed that the crane can be operated safely from all locations.