Analysis of PMM data for underwater vehicles

The following thesis studies techniques for determining the manoeuvring performance of unmanned underwater vehicles (UUVs). The use of UUVs is increasing in both commercial and military applications. These craft, which are unmanned, are controlled and powered through an umbilical cable in the case of remotely operated vehicles; for autonomous UUVs, they are powered and controlled from suitable on-board equipment. Often the expense of operating UUVs over numerous scenarios and environmental conditions restricts opportunities for developing operational use of these craft. Hence the capability to simulate the manoeuvring performance of particular UUVs is desirable. The development of mathematical models and software functions to simulate a manoeuvring UUV are given in this work. The thesis also addresses the requirement of these mathematical models for hydrodynamic coefficients that characterise a vehicle's performance. Experimental techniques based on planar motion mechanism (PMM) measurements for determining hydrodynamic coefficients are considered here. The development of a horizontal planar motion mechanism (HPMM) by the Australian Maritime Engineering Cooperative Research Centre (AME) provided the basis for an extensive experimental program. The work reported here includes results from tests on a 1/3rd scale model of the Royal Australian Navy's Mine Disposal Vehicle, PAP104. The HPMM is an electromechanical device that is mounted in either a towing tank or a circulating water channel, enabling scale models to be oscillated in a water flow. Hydrodynamic loads are measured together with the displacement of the model, allowing the hydrodynamic coefficients to be determined. Techniques are reviewed for the analysis of HPMM data. The Systems Identification technique is developed into software routines that are used to determine hydrodynamic coefficients for the 1 /3rd PAP104 model. Experimental considerations for model testing are discussed together with the equipment and facilities used. Recommendations are proposed for the design of the model test program, which includes commentary on frequency and blockage related effects that occur with oscillatory testing. A circulating water channel (CWC) was used in conjunction with the HPMM for the continuous testing of the submerged models. An evaluation of this facility with respect to flow quality is given together with results of the work undertaken to improve the flow uniformity. Validation data was provided by independent vertical planar motion mechanism tests that were conducted on a full size PAP104 vehicle. These data show good agreement with the results obtained from the HPMM tests conducted on the 1/3rd scale model of the PAP104. An error analysis was conducted on the experimental procedure and HPMM data analysis method to determine accuracy of individual hydrodynamic coefficients. A sensitivity analysis was also conducted using the UUV simulation to investigate the effect of individual errors in the hydrodynamic coefficients on the navigational accuracy of a manoeuvring UUV.