Maneuvering through ice-covered waters requires a special ship design commonly known as an icebreaker. Before an icebreaker is constructed, the hull is rigorously tested for its ice breaking capabilities in an ice tank. An ice tank is a refrigerated water tank in which a scale model of the ship’s hull is pulled by a gantry carriage through a layer of formed ice.
Problems inherent in the design of the ice tank can distort test results or even prevent testing completely. This was the case when an engineer noted that the speed of the model ship became unstable when the gantry carriage was operating at low speeds. The engineers discovered that the force generated by the ship’s hull when breaking ice created backlash between the gears driving the gantry carriage. In an attempt to compensate for the backlash, the controller caused the speed of the model ship to overshoot and then undershoot, causing damage to the test rig.
The challenge: To model the dynamics of an ice tank carriage and identify a mechanism to alleviate the backlash inherent in the design of the gearbox.
The engineers use MapleSim to:
- Create a high-fidelity physical model of the ice tank system
- Add a preload torque component to the output shaft of the gearbox to minimize backlash
- Calculate the minimum required preload torque to achieve minimal chatter between gear teeth using the MapleSim Optimization template
- Validate the solution by simulating it in MapleSim before making changes to the testing facility
MapleSim’s graphical working environment allows engineers to easily mix components from different domains without having to worry about underlying equations. The proposed solution is validated quickly, efficiently, and with minimal cost. Since the design is verified in advance, engineers are confident that only a single facility shutdown is required to make the necessary modifications. The short time required for model formulation, solution validation, and implementation of modifications means that the testing facility is reopened sooner than would have been possible with other approaches.