Control, Simulation, and Testbed Development for Improving Maritime Launch and Recovery Operations

Abstract

Improvements to launch and recovery operations at sea are driven by the desire to increase safety and operational availability. This thesis presents various tools to improve motion compensation strategies in maritime launch and recovery: a 3D computer simulator to examine wave synchronization, a signal prediction algorithm for Go-NoGo states and a hardware setup to simulate ship and wave motion. The 3D simulator of towed body dynamics was advanced to model the wave interactions with the cable and towed body as the body exits the water. Small scale simulations were run to investigate the inclusion of wave synchronization in established active heave compensation strategies where the hypothesis that wave synchronization would reduce variations in cable tension was not supported; the simulations demonstrated that wave synchronization increased variations in cable tension compared to simulations not using motion compensation. The use of a signal prediction method that forecasts a periodic signal based only on historic data of the signal was explored. The method is a means to predict safe breach events where the prediction algorithm was advanced and tuned to determine Go-NoGo states. A Go scenario identified by the mean and one standard deviation of the predicted signal was found to produce a Go-NoGo signal that agreed most with the desired Go-NoGo signal for forecasts up to 10 s. For the development of laboratory equipment for the Carleton University flume tank, a ship motion simulator was designed and built to emulate 5 degrees-of-freedom of ship motion and a kinematic analysis was performed to characterize the system workspace. For producing waves in the flume tank, a design methodology was developed for the design of a plunger-type wavemaker. A numerical model for determining the wave amplitude to actuator stroke length ratio was advanced to include the effects of a flow current. The design methodology enables the designer to select an appropriate actuator and plunger shape based on an operating point that incorporates multiple design variables.

Sensitivity Analysis and Experimental Validation of Plunger-type Wavemakers Modelled with a Steady Flow

“…The wave profiles produced by a plunger-type wavemaker were studied by Ellix and Arumugam [EA84] which Wu [Wu88,Wu91] referenced for comparison to the theoretical model; however, both theory and experiment were only applied to the still water case and did not include the effect of a steady flow. The plunger-type wavemaker theory was advanced by McPhee [McP19], who proposed that the uniform flow in a water channel be taken into account, but experimental validation was outside the scope of the study. Unlike the moveable-wall wavemakers, the motion of the plunger allows for flow across the lateral boundary while also not requiring any submerged mechanical components.…”

“…A disadvantage of the plunger-type wavemaker is the requirement for relatively long wave channels to achieve wave stabilization. However, in McPhee's [McP19] study on the design of the plunger-type wavemaker, it was determined that it is theoretically possible to achieve stable waves in the water channel at Carleton University.…”

“…For the plungertype wavemaker theory, only fully developed progressive waves are desired in the area of interest. McPhee [McP19] determined for distances that are double or triple the water depth h of the water channel, standing waves can be considered negligible compared to progressive waves. Thus, sensors for measuring the surface elevation should be placed at a distance of x ≥ 2h relative to the positioning of the wavemaker where x is the distance from the wavemaker.…”

“…A photograph of the wave absorber, whose base structure had been previously constructed by McPhee [McP19], is displayed in Fig. 3.9 with its slope pointing towards the test section.…”

“…The theoretical model of a plunger-type wavemaker has been developed for the still water case [Wu88] and flow case [McP19]; however, further research into the model and the parameters on which it is dependent is limited. Therefore, the second objective of this thesis is to quantify the influence of the input parameters on the output of both the conductive wave gauge and the wavemaker models through variancebased global sensitivity analyses for design applications.…”