Solar Testbed for Energy Harvesting Sensor Nodes

In the field of Wireless Sensor Networks (WSNs), regenerative energy supplies getting more and more import to enable autonomous operation of sensor nodes. In outdoor usage, solar harvesting provides high power density enabling reliable power supply for many applications. Algorithms relying on the harvested energy hamper comparison accuracy due to changing weather conditions and thus harvesting profile. Creating equal realistic environmental conditions instead of current traces is therefore mandatory for accurate comparison of algorithms, e.g. prediction of expected energy income. Using a Raspberry Pi and a Arduino, a flexible illumination control for small solar cells is developed. Inside a light-tight box, the solar panel is illuminated by a high power LED, which is controlled by software via Pulse Width Modulation (PWM).

Poster, Publication

GPS-enabled Surface Vehicle for Underwater Range Sensing

Localization is a mandatory prerequisite for swarms of micro AUVs (autonomous underwater vehicles). The latter have recently drawn considerable research attention, as they can be used in scenarios stretching from dam inspections over localization of pollution sources to scientific experiments. In this context an acoustic underwater modem has been developed at our institute. Based on range-based distance estimations localization algorithms are now being developed and have to be tested against a GPS ground truth. Since range estimation dramatically changes with movement of communicating parties, further research on moving objects is needed. For this a pre-defined track consisting of multiple waypoints has to be followed, simulation an autonomous underwater vehicle.

Poster

Low-Cost Speed-Of-Sound Measuring in Underwater Environments

Localization is a mandatory prerequisite for swarms of micro AUVs (autonomous underwater vehicles). Low-power underwater communication is a mandatory prerequisite for swarms of micro AUVs (autonomous underwater vehicles). The latter have recently drawn considerable research attention, as they can be used in scenarios stretching from dam inspections over localization of pollution sources to scientific experiments. In this context an acoustic underwater modem has been developed at our institute. It uses a Time-Of-Flight approach to measure distances between two AUVs based on ranging. The speed of sound underwater is mainly influenced by the three parameters depth, temperature and salinity. Measuring these parameters is therefore mandatory for accurate distance calculations based on the transmission time. Commercial CTD probes are available for this problem, but quite expensive.

Poster

Cloud Cover based Power Efficient Scheduling of LED Controller

The spreading of Wireless Sensor Networks (WSN) brings new tasks of the energy supply of sensor nodes. To avoid maintenance intensive power supplies, e.g. batteries, regenerative energy resources can be used to enable self-sustaining operation. For outdoor usage, solar cells offer high power density but hamper harvesting consistency. Due to changing weather conditions or day and night rhythm, harvested energy varies. Thus, careful usage of energy resources is mandatory. Weather forecasts help to improve the demand planning: if cloudy conditions are expected, the activity of the sensor node has to be reduced. Important aspects include the fulfillment of the designated task, e.g. offering a fixed blink interval of a signaling LED.

Poster