Colibri's Micro-Gyro

A gyro is an angular rate sensor whose output signal corresponds to the speed of rotation.

Colibri's gyro sensor element

There is a wide spectrum of emerging markets for micro-gyros with different performance requirements, including automotive purposes (airbags, collision avoidance systems, navigation, anti-skid and active suspension systems, etc.), consumer products (navigation, rehabilitation, toys, sport equipment, stabilization systems for video cameras, etc.), and industrial applications (stabilized platforms, angular measurements, robotics, etc.).

Market analyses made in 2006 indicated a global need year 2009 of more than 65 million high and medium quality micro-gyros, with a high annual market growth that is fueled by competition and a continuous reduction in component price.

Conventional gyros, based on mechanical spinning rotors, laser technology or optical-fiber systems are too bulky, too expensive, or have a too modest reliability for these new mass-markets. Micromachined vibrating gyroscopes, including Colibri's, have a strong potential to meet the large market needs.

Gyro principle Colibri’s gyro is based on a micromachined tuning fork, a few mm long, for which a reference vibration (10-50 kHz) is excited in the plane of the tuning fork with typically a few µm in amplitude. The tines try to return to their original reference plane when the tuning fork, and thereby this plane, is rotated around an axis parallel to the tines. These inertial effects generate a vibration perpendicular to the plane of the tuning fork whose amplitude is proportional to the speed of rotation. Although this amplitude is only a few percent of an atomic radius at the tip of the tines at the resolution limit, it is possible to detect since its frequency and phase are known.

Colibri's sensor element is made of crystalline quartz. This is a material well suited for this type of sensor as it is an extremely inert micromachinable piezoelectric material that enables an unsurpassed signal stability over time and temperature, and for which vacuum packaging is not necessary except for the toughest high-performance levels. In fact, the commercial success rate for micromachined gyros based on quartz sensor elements is high compared to that for those using silicon sensor elements. The drawback of quartz is that it does not allow electronics to be integrated on the sensor element itself.

The production of the gyro’s sensor element takes advantage of the micromachining production technology developed by the watch crystal industry. They produce six-digit quantities of watch crystals each hour at a production cost of less than $0.20 apiece, including packaging and individual laser trimming. The requirements on the cleanroom are moderate as the geometry is ‘large’ and the process steps are few and fairly simple.

Colibri's gyro system As for all micro-gyros, performance is determined almost entirely by how well potential error sources are handled and only to a minor degree by noise and scale factor optimization. This sets tough requirements on the gyro system, both mechanically and electrically. Important is to design to cost and need, and to include error tolerance into the design.

Typical specification for future automotive safety systems, e.g. collision avoidance systems: 100°/s range, 3% scale factor stability, 0.01°/s/sqrt(Hz) noise, 0.3°/s long-term stability (temperature and aging), 0.05°/s short-term stability, 20Hz bandwidth, -40°C / +110°C temperature range, a shock survivability of 20,000g, and very low vibration sensitivity over a broad frequency range.

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