CDP applications and components made for our customers 

AHC Platform

We made an Active Heave Compensated Platform for Odfjell, a highly sophisticated solution involving non-linear multivariable control.

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Concept design

It is the requirements for compensation accuracy and payload that is the foundation for the platform design. And, of course, cost also must be considered.
For payloads as high as 20 - 60 tons, the hydraulics get very power consuming and there are also safety related problems with having a platform both located and supported on active controlled cylinders.

So, we came up with a new concept, with 3 DOF (heave, roll, pitch) having 3 active controlled hydraulic cylinders supporting the weight, and control arms for location support. This is similar to the suspension system on cars, where fairly small trailing arms and springs form a very strong location for the wheels.

The result is a sturdy, safe and reasonably cost-efficient design, easily scaled to payloads up to around 100 tons if desired.

Mathematics and cybernetics

An obvious challenge must be the mathematics and cybernetics required to make the platform move as desired according to the main goal of eliminating all movement. This is fairly easily solved using the art of cybernetics, involving kinetics, signal processing and matrix transformations.

Advanced control algorithm

To achieve the level of performance required, the movement of the cylinders must be controlled very fast and very accurate. We designed a non-linear, multivariable, adaptive control algorithm for this purpose, where the algorithm itself and initial tuning of parameters were performed by extensive use of simulation.

CDP control system

The use of CDP allowed us to develop this signal-processing intensive application in very short time. The ability to do real-time signal analysis for regulator verification and tuning is very valuable, as is the possibility for accurate and fast signal processing.

And at the same time we can use standard off-the-shelf hardware.

Simulation

The ability to run simulations on the actual control system was very valuable in both design phase and during testing and tuning. This is commonly known as Hardware-In-The-Loop simulation.

At first, all mechanical parts were simulated, running only software simulation. In fact, the whole control system application was completely tested in our office before we put it on the vessel. Gradually enabling more physical parts, eventually we use simulated vessel movement to test active heave compensation on-shore.

This reduces risk and cost, and when we go out off-shore to do the first test, we know that the platform is working, and we can focus on doing the last of fine tuning.

User interface

We designed a multi-page graphical user interface, acting as a control panel for the platform. From the user interface it is easy to operate the platform, and essential signals such as cylinder motion can be real-time monitored.

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Fujitsu IOServer

For MMC Tendos we made support for the Fujitsu FRN55G11S-4EN frequency converter.

In two weeks, we implemented and tested the IOServer which runs on RS-485 multipoint. It features frequency control with  frequency, torque, output-current and alarm feedback.