NON-INVASIVE SPEED SENSOR
TECHNICAL FIELD
The invention relates to shaft speed sensing for various applications such as wind turbine monitoring.
BACKGROUND OF THE INVENTIQN
Wind turbines are machines used to convert wind power to electrical power. Often, wind turbines use propellers or turbine blades to drive a gearbox, rotor shaft, and a generator (or other mechanical elements) that ultimately produces electricity. After a period of operation, the mechanical elements used by wind turbines may need to be monitored for abnormal behavior, predictive maintenance, or warranty checks. Condition monitoring (CM) equipment can be installed that provides feedback about the operational condition of the wind turbines. However, linking CM equipment to wind turbines can be a labor-intensive task that involves equipment having a wide range of components. This equipment can typically include a processor, non-volatile memory, as well as various sensors that are coupled to the wind turbine- or specific conqjonents hereof. These sensors can include a speed sensor for measuring turbine speed, accelerometers for measuring vibration, and a current monitor for determining turbine load.
BRIEF DESCRIPTION OF THE DRAWINGS
—Preferred exen^lary embodiments of the invention will hereinafter be described in conjimction with the appended drawings, wherein hke designations denote like elements, and wherein:
FIG. 1 is a photo depicting portions of a wind turbine and diagrammatically depicts the internal wind turbine shaft in broken lines;
FIG. 2 is a diagram showing an internal speed sensor and optical pickup for monitoring pulses of an indicator LED of the speed sensor; and
FIG. 3 depicts examples of speed sensors.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the present inventioii can be utilized in conjunction with a wide variety of machines to detect rotational speed of a shaft or other element, one exemplary embodiment is described below as it would be used as a part of condition monitoring (CM) equipment for wind turbines.
A section of one wind turbine design is generally shown at in FIG. 1. The wind turbine includes a drive shaft 12 that carries turbine blades 14. The drive shaft 12 connects at one end to a generator (not shown). As wind acts on the blades 14, the shaft 12 rotates powering the generator and creating electricity. Referring now also to FIG. 2, the wind turbine includes a wind turbine speed sensor 16 that monitors the speed of the drive shaft 12 as part of wind turbine operation. This sensor 16 is an existing sensor onboard the wind turbine and is not a part of the CM equipment itself which will be described below. The speed sensor 16 can be of the type that includes a light-emitting diode (LED) 18 that outputs light pulses with a frequency equal or proportional to the rotational speed of the drive shaft 12.
The CM equipment 10 can be temporarily or permanently installed on the wind turbine to gather data about the turbine over a period of time. For temporary installations, the equipment is installed for a period of time and then removed by a technician. As shown in FIG. 2, the CM equipment 10 includes a processes, digital memory (e.g., RAM), a pliuality of accelerometers, and an optical pickup 20. Other components can be included as well. As will be appreciated by those skilled in the art, the processor, memory, and accelerometers can all be hardware components that are conmiercially available and can be intercoimected and controlled via software to obtain vibration and other such acceleration data from various points or components on the wind turbine. When installing the CM equipment 10, tiie optical sensor 20 is located adjacent the LED indicator 18 such that it can detect light pulses emitted fit>m the LED and commxmicate that information to the processor (CPU).
As is known, the speed sensor 16 sends an electronic signal each time the drive shaft 12 rotates a predetermined distance. In one example, the drive shaft 12 includes a plurality of ferrous teeth (not shown) that encircle the shaft 12. The ferrous tooth/teeth can be bxunps or locations on the drive shaft 12 that have an increased
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amount of material relative to the area(s) next to the tooth. Each tooth is an equally-
•r spaced and predetermined distance from the nearest tooth. As the drive shaft 12
rotates about an axis 22, the teeth rotate as well. When one of the teeth passes the
speed sensor 16 it generates a detectable inductive current pulse, which is used by the
wind turbine itself as a part of its electricity generating function. By knowing the
amount of distance between die teeth and the amount of time passed between sensing
the presence of teeth, the wind turbine circuitry can determine the rotational speed of
the shaft 12.
The speed sensor 16 also uses the detected inductive pulses to pulse the LED 18. The optical pickup 20 is positioned to detect the light pulses emitted by the LED. Each time the speed sensor 16 activates the LED 18, the optical pickup 20 detects it and generates a signal of its own. Thus, based on the pulse rate, the CM equipment processor can determine and record the rotational speed of shaft 12. As shown in FIG. 2, the pickup can be mounted in close proximity to the LED 18 in such a way to accurately receive the light emitted from the LED. Turning to FIG. 3, examples of ■ optical pickups 20 and speed sensors 16 are shown. Optical pickup 20 can be, for example, a glass fiber optic sensor, a convergent-mode sensor, or any other suitable sensor as known to those skilled in the art. The speed sensor 16 can be one that provides a detectable optical output that pulses at a rate dependent on the rotational speed of shaft 12. In one particular embodiment, the optical sensor 20 includes M12 connectors and a plurality of LEDs 18 located on the exterior of the sensor 16.
By incorporating an optical pickiq) in sight of the visiially-confirmed output of the speed sensor, the CM equipment can monitor turbine shaft speed without any physical interconnection to the shaft itself. This can help reduce the cost of the CM equipment and can help expedite the installation and removal of the CM equipment. The optical pickup also can monitor and diagnose problems with the wind turbine speed sensor.
It is to be imderstood that the foregoing description is not a definition of the invention, but is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but ratfier is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to
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be construed as limitations on the scope of the invention or on the definition of terms
■r used in the claims, except where a term or phrase is expressly defined above. Various
other embodiments and various changes and modifications to the disclosed
embodiment(s) will become apparent to those Skilled in the ait For example, any
suitable shaft speed sensor can be used as long as it provides an optical indication of
the shaft rotational speed that can be detected by the optical pickup. All such other
embodiments, changes, and modifications are intended to come within the scope of
the appended claims.
As used in this specification and claims, the terms "for example," "for instance," and "such as," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning diat lliat the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.
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CLAIMS
1. A method of measuring rotational speed of a shaft, comprising the steps of:
coupling an optical pickup to a shaft speed sensor having an indicator light
that pulses proportionally to rotational speed of a shaft being measiu-ed by the speed
sensor;
receiving light pulses fi"om the indicator light of the speed sensor; and determining the rotational speed based on the rate of received light pulses.
2. The method of claim 1, wherein the coupling step further comprises coupling
the optical pickup to an existing speed sensor at a shaft of a wind turbine.
3. A wind turbine condition monitoring system, comprising:
* a processor;
a digital memory having a program stored thereon and being accessible by the processor; and
a plurality of sensors that provide data to the processor, the sensors including accelerometers and an optical pickup, wherein the processor is operable under control of the program to determine a rotational speed of the wind turbine based on light pulses received by the optical pickup.
Dated this ||/05/2012 l/^~\/
(HRISHIK^H RA^pH^M^HURY)
OF REMFRV^ SAGAR
ATTORNEY FOR THE AP^CANT[S]
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