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.
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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.
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The given Drifter should be extended with a diving device, which is able to pull down the whole Drifter with its sensors 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.
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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 Diving procedure has contains a length of 1 Minute and is given to the divers logic, prior to the diving start signal. For the one minute time period, the diving procedure contains different water depths values which should be reached by the diving device 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 Procedure only contains vertical information, and 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. The diver should provide a matter to counteract these disturbances to follow the vertical path with an horizontal error of 0.2m for a vertical movement of 1m.
Implementation
For the implementation of the diving robot, Matlab Simulink should be used. The Test-Environment for the Diver will be provided by the institute of mechatronics in mechanics, so the simulation should only contain the system simulation of the diver. Every part that is used in the construction should also be included in the Simulink implementation, only the microcontroller can be represented with a simplification like Matlab Stateflow.