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Draw-wire sensor for measuring steering angle

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The Solar Boat Team of TU Delft has been working on pushing the maritime industry to a more sustainable future for the past 15 years. This year the team had an additional challenge on top of that; they wanted to race with their first hydrogen powered boat in Monaco during the Energy Boat Challenge 2021.

The Hydro Motion boat was designed and built to propel on hydrogen. This year a lot of effort and attention went into the implementation of a hydrogen propulsion system. In addition, the boat is meant to fly with the help of two L- and one T-shaped wings underneath the boat. The position of the wings must be adjusted for the Solar Boat to function optimally. To do this the solar boat uses a draw-wire sensor connected to a steering plate that measures the steering angle. This angle is then used to determine the differential pitch.

Draw-wire sensors
Draw-wire sensors (also called string pot displacement sensors) can measure distances at up to 0.01 mm accuracy. They measure the position and movement of an object by means of a flexible steel cable that is fed from a spring-loaded spool. The linear movement at the end of the cable is thus transformed into a rotational movement.

About the TU Delft Solar Boat Team

The TU Delft Solar Boat Team is a Dreamteam from the TU Delft. The team consists of ambitious students of different faculties from the TU Delft. Each year the students take up the challenge to design, produce and race with a fully functioning boat. In the last few years the students built solar-powered boats, but in 2021 they built a hydro motion boat. 

 

 

Flying a hydrogen powered boat

This is a noteworthy design for many reasons. Project Manager Bouwe Theijse explains how the system works: "Just like an airplane, we need enough speed to generate lift. We will be going fast enough at 22 kilometers an hour, our take-off velocity. From then on, our wings, the hydrofoils, will push the boat out of the water and the entire 1100Kg vehicle will be flying above the water!" Solar Boat Team vehicles have flown before, but this year the team designed the wings so they can carry the full weight of this big boat. A bigger size boat is needed as the team wanted it to take it out to open sea in the Energy Boat Challenge of 2021 in Monaco, competing in the Open Sea Class races. 

When the solar boat flies above the water, it maneuvers by using a differential pitch with the front wings. This principle can be visualized as a motorcycle that has to lean sideways in order to turn. The position of the wings must be adjusted for the Solar Boat to function optimally. To do this the solar boat uses a draw-wire sensor connected to a steering plate that measures the steering angle. This angle is then used to determine the differential pitch.

Draw-Wire for Steering calculations

Together with Althen engineers, the TU Delft team selected the FD60-500-SR-P Draw Wire (string pot) for this application. The string pot has a stroke lenght of 500 mm and potentiometric output. 

The sensor is mounted on the transom of the Solar Boat. The clip of the draw-wire is attached to the far end of the steering plate. The value of the sensor is read by the EMS, the controller board onboard the Solar Boat. The clip of the draw-wire is connected to a point that does not move linearly in one direction. Because of that, simple mathematical calculations are applied to convert the readings of the sensor into the equivalent steering angle. Because of this, the steering angle is calculated very precisely and barely fluctuates. 

Althen is very proud to be part of this effort to bring sustainable developments closer.

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