Method and micro power generator for generating electrical power from low frequency vibrational energy

• US 7,579,757 B2
• Filed: 01/21/2005
• Issued: 08/25/2009
• Est. Priority Date: 01/21/2004
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Najafi, Khalil, Kulah, Haluk
• Primary Examiner(s): Dougherty; Thomas M
• Application Number:
  US10/597,321
• Publication Number:
  US 20080136562A1
• Time in Patent Office: 1,677 Days
• Field of Search: 310/339
• US Class Current: 310/339
• CPC Class Codes: F03G 7/08 recovering energy derived from swinging, rolling, pitching or like movements, e.g. from the vibrations of a machine
• CPC Class Codes: H02K 35/02 with moving magnets and stationary coil systems
• CPC Class Codes: H02N 1/06 Influence generators
• CPC Class Codes: H02N 2/186 Vibration harvesters
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A method and a micro power generator for generating electrical power from low frequency, vibrational energy includes a frequency up-conversion process. The generator is preferably an electromagnetic, vibration-to-electrical power generator which can efficiently scavenge energy from low frequency external vibrations. The generator up-converts low frequency environmental vibrations to a much higher frequency through a mechanical frequency up-converter, and hence provides efficient energy conversion even at low frequencies. This mechanical frequency up-conversion process can be realized in a number of ways. A magnetic method is described as an example. After frequency up-conversion, voltage is induced on coils mounted on resonators by electromagnetic induction. Due to the movement of the coils on their respective resonating cantilevers with respect to the magnet, voltage is generated on the coils and energy conversion is realized.

Claims

1. A method for generating electrical power from low frequency, vibrational energy, the method comprising:

receiving vibrational energy having a low frequency wherein the step of receiving includes the step of providing a micromechanical first resonator device, the first resonator device resonating in response to the received vibrational energy and including an element which is supported to vibrate inertially at a low frequency by inertial forces;

converting the low frequency, vibrational energy to vibrational energy having a high frequency greater than the low frequency wherein the step of converting includes the step of providing a micromechanical second resonator device, the second resonator device resonating at the high frequency greater than the low frequency in response to the resonating first resonator device wherein the second resonator device has a mechanical spring force;

generating a magnetic force between the devices wherein the magnetic force between the devices is larger than the spring force at a catch point at which the second resonator device is magnetically pulled towards the vibrating element; and

converting the high frequency, vibrational energy to electrical power wherein the step of converting the high frequency, vibrational energy is performed electromagnetically.

2. The method as claimed in claim 1, wherein the low frequency is in the range of 1to 100 Hz.

3. The method as claimed in claim 2, wherein the low frequency is in the range of 1to 10 Hz.

4. The method as claimed in claim 1, wherein the second resonator device has a mechanical resonance frequency in the range of 1 to 10 kHz.

5. The method as claimed in claim 1, wherein the second resonator device includes an array of micromechanical resonators.

6. A micro power generator for generating electrical power from low frequency, vibrational energy, the generator comprising:

a micromechanical first resonator device which resonates in response to the vibrational energy, the first resonator device including an element which is supported to vibrate inertially at a low frequency by inertial forces;

a micromechanical second resonator device having a mechanical spring force; and

a circuit including a magnet for generating a magnetic force between the devices and being mechanically coupled to the resonator devices for magnetically coupling the resonator devices together so that the second resonator device resonates at a high frequency greater than the low frequency when the first resonator device resonates wherein the magnet has catch and release points and wherein the magnetic force between the devices is larger than the spring force at the catch point at which the second resonator device is pulled towards the vibrating element, the circuit also converting the high frequency, vibrational energy to electrical power.

7. The generator as claimed in claim 6, wherein the high frequency, vibrational energy is converted electromagnetically.

8. The generator as claimed in claim 6, wherein the low frequency is in the range of 1 to 100 Hz.

9. The generator as claimed in claim 8, wherein the low frequency is in the range of 1 to 10 Hz.

10. The generator as claimed in claim 6, wherein the conversion of the low frequency, vibrational energy is performed mechanically.

11. The generator as claimed in claim 6, wherein the circuit includes at least one coil which moves relative to the magnet and wherein voltage is induced on the at least one coil by electromagnetic induction.

12. The generator as claimed in claim 11, wherein the first resonator device has a mechanical resonance frequency in the range of 1 to 100 Hz.

13. The generator as claimed in claim 11, wherein at least one of the magnet and the at least one coil is mechanically coupled to the resonator devices so that the magnet and the at least one coil move relative to one another to generate voltage on the at least one coil.

14. The generator as claimed in claim 12, wherein the second resonator device has a mechanical resonance frequency in the range of 1 to 10 kHz.

15. The generator as claimed in claim 13, wherein the second resonator device includes an array of micromechanical resonators and wherein each of the resonators has a coil formed thereon.