Construction-Vessel

This demo simulates a marine vessel doing crane operations while dynamically positioned. System plants and controllers are modularized according to responsibility and to preserve numerical stability.

FMUs are listed in Table 1.

Table 1: List of FMUs in the Construction Vessel demo.

System Overview

Thrusters

The simulated vessel has five thrusters: two azimuth thrusters and three tunnel thrusters. Their location with respect to midships is listed in Table 2

Table 2: Thruster Layout

Power Plant

The power plant is responsible for providing power to the thruster, crane and hotel loads. Its topology is shown in Figure 1.

Connections

Connections between FMUs are defined using CSE’s internal system structure format. An equivalent simulator topology is shown in the Simulink diagram in Figure 2

FMUS

Every model in the demo is implemented as a Functional Mockup Unit (FMU). FMUs are a common framework for sharing models generated from different tools such as Simulink, SimulationX etc. All FMUs in this demo is compiled for Windows only.

Winch

The winch FMU combines winch dynamics and control. Inside is a PID controller producing torque commands for the winch model with load depth as the control objective. Users interact with the controller by specifying the load depth setpoint.

The winch model calculates load depth by modelling the winch as a second order dynamic system. Vessel position is necessary to adjust load depth for heave motions. The model outputs load depth, motor speed and power consumption for use in the power plant FMU.

Interface descriptions are given in Table 3 and Table 4.

Table 3: Winch model inputs and outputs (I/O).

Table 4: Winch model’s OSP-IS variable groups

Reference Model

The reference model produces a smooth setpoint signal based on the desired vessel position. This is achieved by passing the setpoint through a rate limited second order system.

Lists of inputs and outputs are given in Table 5 and Table 6.

Table 5: Reference model inputs and outputs (I/O).

Table 6: Reference model’s OSP-IS variable groups

Vessel Model

The vessel model FMU simulates vessel dynamics. Its inputs are environmental forces produced by the wind and wave models and the thruster states from the thruster model. The resultant thrust force is calculated using the thruster layout in Table 2.

The output is the vessel’s velocity expressed in the BODY frame and position expressed in NED.

Lists of inputs and outputs are given in Table 7 and Table 8.

Table 7: Vessel model inputs and outputs (I/O).

Table 8: Vessel model’s OSP-IS variable groups

Thrust Allocation

The thrust allocation FMU transforms the force commands from DP to thruster setpoints. The setpoints are passed to the thruster model which calculates the resultant force.

Lists of inputs and outputs are given in Table 9 and Table 10.

Table 9: Thrust allocation inputs and outputs (I/O).

Table 10: Thrust Allocation’s OSP-IS variable groups

Thruster Model

The thruster model simulates thruster dynamics using setpoints produced by the thrust allocator. The output is a thruster state structure consisting of power consumption, thrust and, for azimuth thrusters, azimuth angle.

Lists of inputs and outputs are given in Table 11 and Table 12.

Table 11: Thruster model inputs and outputs (I/O).

Table 12: Thruster Model’s OSP-IS variable groups

DP Controller

The DP controller FMU calculates the forces necessary to keep the vessel at a desired position. The position setpoint is provided by the reference model and the current position by the vessel model. The forces calculated by DP is used as input the thrust allocation FMU. The control algorithm is simple and consists only of a PID controller for each degree of freedom.

Lists of inputs and outputs are given in Table 13 and Table 14.

Table 13: DP controller inputs and outputs (I/O).

Table 14: DP controllers’s OSP-IS variable groups

Wind Model

The wind model is responsible for modelling external wind forces acting on the vessel.

Lists of inputs and outputs are given Table 15 and Table 16.

Table 15: Wind model inputs and outputs (I/O).

Table 16: Wind model’s OSP-IS variable groups

Wave Model

The wave model simulates first and second order wave forces acting on the vessel. The model is implemented as a linearized wave spectrum producing position disturbances. Meaning that wave disturbances are added directly to the vessel position calculated by the vessel model FMU.

A complete list of outputs is given in Table 17. ‘ The sea state and response magnitude can be tuned by changing the parameters listed in Table 18.

Table 17: Wave model inputs and outputs (I/O).

Table 18: Wave model parameters

Power System

The power system simulates the power plant shown in Figure 4. There is no feedback from the plant to the thruster and the crane. Meaning that both act as if they have unlimited available power. However, power consumption is fed to the power system which calculates bus frequency, voltage and produced power

List of inputs and outputs is given in Table 19 and Table 20.

Table 19: Wave model inputs and outputs (I/O).

Table 20: Power System’s OSP-IS variable groups

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