A compact, high precision rotation sensor and a method for its fabrication
|611 - Abstract:|
|Rotation sensors based on the so-called sagnac effect already exist today, but involve large coils of optic fiber with diameters of a several decimeters. For many applications these sensors are too large to be practical. The technology described here offers sensors based on the same measurement principle but with the size of a silicon chip. It also describes an efficient method of producing such sensors at lenient manufacturing tolerances, allowing large production series at low cost. License agreements are sought.|
Angular velocities can be measured to resolutions of at least 0.001 degrees per hour by means of the Sagnac effect in fibre optic loops. This measurement principle is based on the fact that the speed of light is constant, so that two light pulses sent in opposite directions through a non-rotating fibre loop arrive simultaneously at the opposite end. A rotation of the coil around its longitudinal axis reduces the travel path for one of the pulses, while extending the path for the other pulse. This effect can be accurately measured from a shift in phase or in resonance frequency between the two beams.
Existing sensors based on this principle require large coils in which several kilometers of glass fiber are rolled into a coil of about 20 cm diameter. The current technology exploits the same measurement principle but uses a “one-dimensional photonic ring resonator” integrated in a chip. This is in essence a hollow ring of the smallest possible size that still conducts light in the intended circular path. It can be efficiently manufactured by cutting out a letter “o” shape in the middle layer of three stacked silicate substrates or similar carriers, in which the measurement electronics can also be integrated.
Applications of small, cheap but highly accurate rotation sensors are numerous. Such sensors may be integrated in drive shafts of machinery, turntables, rotational accelerometers, attitude sensors for mobile phones or tablet computers, and any other industrial machinery or consumer level appliances that involve rotational motions.
Innovations and advantages
In comparison to existing sensors based on the same principle, the main innovations of this technology are:
- Miniaturization of a cumbersome (large) sensor to chip level
- New, robust measurement principle for the resonance shift at small scales
- Easy manufacturing by integration of the sensor in standard silicon or germanium wafers
The key advantages of this offer are:
- Miniature size and weight, allowing installation of rotational sensors in applications where existing sensors are too large
- Highly robust against mechanical, chemical, thermal disturbances
- Easy integration with other electronics or sensors such as linear accelerometer chips or inertial measurement units
- Low cost, especially if manufactured in large series
Domain of application
- Mechanical appliances involving rotating parts: engines, actuators, cars and other transport
- Control circuits for accurate rotational motions (e.g. controlling constant RPM of CD players, medical equipment, etc.)
- All kinds of machinery involving electric motors can be accurately monitored for malfunction or overloading
- Accurate measurement of angular velocity of e.g. car wheels can improve safety critical systems like ABS, airbags etc.
- Other applications involving three-dimensional motions
- Hand-held devices such as smart remotes, Wii actuators, sports equipment
- Medical aids such as biomechanical suits, hospital equipment
- Attitude control of airplanes, ships, robots
Last update: 3 December 2014