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Energy harvesters based on vibrations are still not established in industrial environments. A main obstacle is the application specific characteristic of the physical principle: conventional vibration energy harvesters exhibit a fixed Eigen-frequency, which cannot be altered afterwards. If this Eigen-frequency coincides with a dominant frequency in the excitation spectrum, the energy harvester operates in resonance with maximum energy conversion effectiveness. In most applications however, the dominant frequency varies over time in accordance with the operating mode of the machine. In this case effective energy conversion becomes a random event.
Engineers at Hahn-Schickard developed a kinetic energy harvesting device, which can be adapted to the current vibration condition of a machine. The tuning mechanism is based on a magnetic principle and modifies the total stiffness of the vibrating energy converter structure. The adjustment of the Eigen-frequency is performed simply by rotating a tuning knob. Within a rotation angle of 180° a tunable frequency bandwidth of 32 Hz is achieved. The lower bound of the frequency band is 25 Hz, which corresponds to a rotation speed of nearly 1500 UPM. Together with an upper bound of 57 Hz (3420 UPM) the present device is ideal for harvesting energy from speed controlled power units driving pumps, grinding spindles or gear boxes.
In future, adaptive energy harvesting systems will be an important part of condition monitoring systems and embedded sensor systems (cyber physical systems) for achieving a more efficient and economic operation than it is the case today.
- Electromagnetic energy conversion
- Closed magnetic circuit
- Continuous tunable Eigen-frequency
- Integrated power management
- Signal selection
- Bandwidth: 32 Hz
- Lower Bound: 25 Hz
- Upper Bound: 57 Hz
- Voltage output: 3.3 V DC
- Power output: 2.5 mW @ 0.3g
- Size: 100 x 30 x 35 mm³
- Weight: 120g