Background

A drifting sensor platform for ocean research is a small and cheap device which is able to measure water temperature and salinity on the waters surface. Oceanographers need these information to build models to investigate on water densities and ocean currents. Since the properties of the water strongly change in the upper water layer, not only surface information but also measurements in the first meter depths are of great interest. So far those kind of measurements bring a simple and cheap drifter to its limitations and much larger and more expensive tools have to be used.  

With the availability of a smaller and cheaper device to measure water density and temperature also below the waters surface, an acquisition of much higher quantity and therefore a much higher data resolution would be possible. The institute for mechatronics in mechanics would like to extend the cheap and simple surface drifter with a device, which allows to dive vertically and acquire measurement data with the drifters existing sensors.

Example Images show the deployment of a Carthe Drifter

Task Description

Given is a Drifter, which already has the implementations for measuring Temperature and Salinity on the waters surface. The Drifters dimensions are shown in the figure below.

The given Drifter should be extended with a diving device, which is able to pull down the whole Drifter to a minimum depths of two meters. Fully emerged, the drifter has an upwards bouyant force of 50N. Of course, the drifter should still be able to float, after applying the extension.

 The diving device shall be designed as an extension and therefore should function independently of the drifter, only the power supply and the sensor signals of the drifter can be used. The Drifter has a 12 Volt battery which is able to store 20 Wh of energy. With this amount of energy, the diver should be able to reach a total diving time of 5 minutes.

Battery Data:

Voltage: 12V
Capacity: 20Wh
Max. Discharge Current: 25A
Internal Resistance: 120mOhm

To keep the Drifter a low-cost device, the total costs of the diving device should be less than 100€.

Diving Procedure

The diving procedures are determined by the drifters logic and the divers logic needs to process the given instructions to control the diving process. A Diving procedure contains a set of three different water depths (up to a maximum of 10meters) which should be reached within a time frame of 2 minutes. Each target depths should be hold for 10 seconds with an accuracy of +/-0.1m.  The diver should keep its horizontal position at the moment of the start diving signal. Due to currents in the water, the divers downwards path might be disturbed in horizontal directions. 

Environment

You can use "environment.slx" file for making different connections between your model and environment. It has some input and output ports. As an example, a simple system connecting to the environment in the "sample.slx" file is shown.  Some items such as, the water flow velocity, density, and gravity are defined inside of the environment. You need to only put the inserting forces from drifter to the environment as input and connect the poles of battery to your model. As can be seen in "sample.slx" you can show the X, Y, Z place, current, and voltage by scope blocks.