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Sea-Keeping & Manouvering Basin (MMC)

C133 - MMC (Multi Motion Carriage)

The objective of a Cussons MMC (Multi Motion Carriage) with integrated PMM (Planar Motion Mechanism) is to reproduce with high precision the horizontal motion of a ship-model being towed in a Towing Tank following a prescribed trajectory.

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Description

MMC (Multi Motion Carriage) for 37m wide tank and towing speed of 6m/s.

Includes:

  • Main carriage running on four bogey assemblies and complete with drive system
  • Sway carriage with drive system
  • Yaw mechanism with drive system
  • Towpost including a motorised height adjustment mechanism for 1m adjustment range.
  • Model restraining clamp for accelerating/decelerating the model for free sailing tests
  • Air conditioned control cabin
  • Carriage computer control system with all necessary control software for the control of the above drives – this does not include the PMM motion definition, analysis or simulation software unless otherwise quoted.
  • Please Note: This description and the General arrangement drawing are based on the standard C133.

TECHNICAL DATA

The objective of a MMC (Multi Motion Carriage) with integrated PMM is to reproduce with high precision the horizontal motion of a ship-model being towed in a Towing Tank following a prescribed trajectory. The collected force and moment data can then be used for deriving the coefficients used in the equations of motion, necessary for determining the manoeuvring characteristics of the ship-model. This provides the basis for superior predictions of the manoeuvring and course keeping qualities of surface ships and the evaluation and determination of design criteria, leading to the assessment of almost all aspects of ship manoeuvring.

MMC Specifications (Suitable for models up to length 4m):

(Design modifications to the following technical specifications may be considered, depending upon a clients particular requirements)

Main Carriage:

Max Speed of Travel – X Direction: 6.0 m/s

Reverse Speed in X Direction: >4.0 m/s

Acceleration – X Direction: 0.8 m/s2

Width: 38m

PMM:

Y- (Sway) movement amplitude: Up to 17 m

Φ -(Yaw) movement amplitude: up to 90 degrees

Max. Speed for the Yo-movement: 4.0 m/s

Max. Acceleration for the Yo-movement: 1.0 m/s2

Max. Speed for the Φ -(Yaw) movement: 30 degrees/sec

Speed Accuracy (X, Y and Optional Δx): <0.1 % of set speed

Acceleration Y Direction: 0.8 m/s2

Max Emergency-stop Deceleration: 3.0 m/s2

Optional Δx:

Max Speed of Travel Δx Surge Carriage: 1.5 m/sec

Δx Surge movement travel: 1.5m

Key:

X Movement in longitudinal direction of the tank

Y Movement in transverse direction

Φ Angles around the vertical axis of the ship model

Construction:

The MMC consists of a Planar Motion Mechanism (PMM) integrated onto a separate self-propelled Towing Carriage, with computer controlled servo motor operated mechanisms for producing longitudinal, transversal and rotating motions in a connected ship-model. These combined motions are superimposed on the normal motion of the MMC as it travels along the tank.

The ship-model is attached to the PMM by way of a telescopic tow post and multi-component balance that allows free heave and trim motion along with free and forced roll. Software controls the functioning of the PMM, monitors the model movement, acquires data and carries out evaluations of the model tests. The PMM can produce sinusoidal motion of surge, sway, yaw and roll plus combinations of all motions. The ship-model is free to rise, fall and trim, and is towed in a predetermined curvilinear path at predetermined speeds, whilst the resulting hydrodynamic forces and moments are measured as functions of time. This is especially useful for research purposes and for validation of CFD results, as well as for the direct determination of hydrodynamic coefficients of manoeuvring equations of motion.

Scope of Supply:

The MMC consists of:

  • A self-propelled Carriage with an integrated Planar Motion Mechanism;
  • An integrated system capable of towing models up to a defined displacement and length, in free heave and pitch modes;
  • A model attachment system to enable forces and moments acting on the model to be measured both in body fixed and inertial frames of references, transducers for measuring roll torque, roll and heel angles and heave motion:
  • Surge, swaying and yawing apparatus including necessary servo-motors and associated control units;
  • A data acquisition and processing system with necessary signal conditioning amplifier units;
  • A Carriage and PMM Control System located aboard the CMMC.
  • Software for data acquisition, reduction, analysis and prediction of overall directional stability and manoeuvring characteristics of the ship and to generate a database for development of handling quality criteria for various types of ships;
  • Software package for simulation of trajectory of ships under various manoeuvres;
  • Calibration rigs / tables for calibrating the force gauges.

(Note: The standard supply of the MMC does not include main and current collector rails, which are charged separately depending on the length of tank)

The PC Based Control and Data Acquisition System provides the following capability:

  • A dynamic force analysis programme, which determines magnitude of forces in phase with sway and yaw velocities and accelerations;
  • An analysis programme, which creates files of non-dimensional forces and moments;
  • Coefficients and propeller propulsion ratios as function of non-dimensional state variables;
  • A plotting programme, which creates plots of non-dimensional force vs. non-dimensional state variables;
  • A programme for extracting the hydrodynamic coefficients from the non-dimensional and motions data sets;
  • A programme that compares coefficients determined from the test data with empirically predicted coefficients to provide rapid confirmation of data quality;
  • A programme that uses these hydrodynamic coefficients and ship mass properties to simulate standard manoeuvres including turns, zigzag and crash stops;
  • A programme that stores results of simulation together with ship characteristics data in a ship manoeuvring performance database.
    MMC (Multi Motion Carriage) Uses:

The MMC (Multi Motion Carriage) is designed to carry out the following:

  • Analysis to develop techniques for evaluating loss of directional stability and degradation of manoeuvring performance in waves;
  • Optimisation of ships designs from dynamic point of view.
  • Theoretical and experimental works in the field of ocean engineering.
  • Tests in regular and irregular waves of ships and structures offshore.
  • Manoeuvring tests and other measurements related with dynamics of ships and floating structures.
  • Tests of stability after ship damage.
  • Free model self-propulsion tests using the PMM to track the model while supporting cables and services etc.
SMB (CPMC)