Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model's Motions and Loads Measurement in Realistic Sea Waves

Abstract

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship's navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign.

Keywords: GPS/INS system; fiber optic sensor; marine physical sensors; motions and loads measurement; remote control and telemetry system; ship seakeeping test.

Figure 1

Conceptual view of the models: (a) the small-scale model; and (b) the large-scale model.

Figure 2

Definition of global motions and loads: (a) motion components; and (b) sectional load components.

Figure 3

View of the physical small model: (a) the model hull; (b) backbone beams; and (c) propellers and rudders.

Figure 4

Sensor arrangement on the small-scale model.

Figure 5

Backbone beams: (a) strain gauges on beam; (b) cylinder beam; and (c) beam stress calibration.

Figure 6

Stress measure scheme: (a) rectangular backbone for VBM and HBM; (b) circular backbone for VBM, HBM and TM; and (c) full-bridge circuit.

Figure 7

Measurement sensor or equipment: (a) pressure sensor; (b) accelerometer; and (c) the DH5902 data collectors.

Figure 8

View of the 5-DOF seaworthiness instrument: (a) overview of the device; (b) longitudinal slip frame; (c) heave stick and angular pivot.

Figure 9

Towing tank facilities: (a) towing tank; (b) high speed tank; and (c) deep ocean basin.

Figure 10

Sketch of tank measurement system.

Figure 11

Result of a test condition in regular head waves: (a) wave elevation; (b) heave motion; (c) pitch motion; (d) bow vertical acceleration; (e) vertical bending stress (VBS) amidships; and (f) wave impact pressure.

Figure 11

Result of a test condition in regular head waves: (a) wave elevation; (b) heave motion; (c) pitch motion; (d) bow vertical acceleration; (e) vertical bending stress (VBS) amidships; and (f) wave impact pressure.

Figure 12

Conceptual design of the large-scale model arrangement.

Figure 13

Sensors arrangement on the large-scale model.

Figure 14

Large-scale physical model: (a) model overview; (b) backbone beam; and (c) propulsion system.

Figure 15

Equipment for environment measurement: (a) anemometer; (b) wave buoy; and (c) tachometer.

Figure 16

Interface of the 3D wave analysis software: (a) time series of wave surface elevation; (b) frequency spectrum and direction distribution; and (c) directional spectrum.

Figure 17

The structural safety monitoring system: (a) arrangement of sensors; (b) the fiber optic sensor on the backbone surface; and (c) interface of monitoring software.

Figure 18

The GPS/INS system: (a) device components; (b) the INS core unit; and (c) onboard installation.

Figure 19

Interface of the GPS/INS software: (a) system initialization; (b) satellite communication; and (c) model state monitoring on escort yacht.

Figure 20

The autopilot system: (a) drive mechanism; (b) components interconnection; and (c) interface of the user control handle.

Figure 21

User interface of remote control and monitoring system: (a) on the model; and (b) on the escort yacht.

Figure 22

Framework of the remote control system.

Figure 23

Framework of the telemetry system.

Figure 24

Video recording: (a) the on deck video camera; (b) view from the model; and (c) view from the yacht.

Figure 25

Experimental procedure.

Figure 26

Examples of measured sea trial data: (a) model speeds; (b) model azimuth; (c) pitch motion; (d) roll motion; (e) vertical speed at COG; (f) sectional VBF at #2; (g) sectional VBF at #12; (h) wave impact pressure at sensor 4; (i) bow vertical acceleration; and (j) model navigation trace.

Figure 26

Examples of measured sea trial data: (a) model speeds; (b) model azimuth; (c) pitch motion; (d) roll motion; (e) vertical speed at COG; (f) sectional VBF at #2; (g) sectional VBF at #12; (h) wave impact pressure at sensor 4; (i) bow vertical acceleration; and (j) model navigation trace.

Figure 26

Examples of measured sea trial data: (a) model speeds; (b) model azimuth; (c) pitch motion; (d) roll motion; (e) vertical speed at COG; (f) sectional VBF at #2; (g) sectional VBF at #12; (h) wave impact pressure at sensor 4; (i) bow vertical acceleration; and (j) model navigation trace.

Figure 27

Wave data for small-scale model test: (a) the design sea state; and (b) the extreme sea state.

Figure 28

Wave data for large-scale model test: (a) the design sea state; and (b) the extreme sea state.

Figure 29

Comparison of ship response results: (a) ratio of small/large model results; and (b) ratio of small/large model responses under unit wave height.