Gyro sensors - How they work and what's ahead
Gyro sensors, also known as angular rate sensors or angular velocity sensors, are devices that sense angular velocity.
In simple terms, angular velocity is the change in rotational angle per unit of time.
Angular velocity is generally expressed in deg/s (degrees per second).
Gyro Sensor Types
Gyro sensors come in a variety of types. Here, different types are plotted by size and performance.
In recent years vibration gyro sensors have found their way into camera-shake detection systems for compact video and still cameras, motion sensing for video games, and vehicle electronic stability control (anti-skid) systems, among other things.
Moving forward, demand for vibration gyros is expected to grow in areas such as vehicle driver safety and support systems, and in robot motion control.
Vibration Gyro Sensors
Vibration gyro sensors sense angular velocity from the Coriolis force applied to a vibrating element. For this reason, the accuracy with which angular velocity is measured differs significantly depending on element material and structural differences. Here, we briefly describe the main types of elements used in vibration gyro sensors.
Types of elements used in vibration gyro sensors
Vibration gyro sensor manufacturers are using a variety of materials and structures in an effort to devise compact, high-accuracy gyro sensors that have good characteristics, including:
• scale factor
• temperature-frequency coefficient
• compact size
• shock resistance
• noise characteristics
|Silicon transducer||Silicon||Si MEMS
NOTE: Every company uses a different structure.
How Angular Velocity Sensing Works (in Vibration Gyro Sensors)
Vibration gyro sensors sense angular velocity from the Coriolis force applied to a vibrating object.
Here, we explain how this works, using as an example Epson 's double-T structure crystal element.
|1. Normally, a drive arm vibrates in a certain direction.||2. Direction of rotation||3. When the gyro is rotated, the Coriolis force acts on the drive arms, producing vertical vibration.|
|5. The motion of a pair of sensing arms produces a potential difference from which angular velocity is sensed. The angular velocity is converted to, and output as, an electrical signal.||4. The stationary part bends due to vertical drive arm vibration, producing a sensing motion in the sensing arms.|
Gyro Sensor Applications
There are three main applications for gyro sensors.
|Angular velocity sensing|
|Sense the amount of angular velocity produced.
Used in measuring the amount of motion itself.
Ex.) Checking athletic movement
|Senses angular velocity produced by the sensor's own movement. Angles are detected via integration operations by a CPU.
The angle moved is fed to and reflected in an application.
Ex.) Car navigation systems
|Senses vibration produced by external factors, and transmits vibration data as electrical signals to a CPU.
Used in correcting the orientation or balance of an object.
Ex.) Camera-shake correction
Examples of angular velocity in applications:
• Car navigation systems: ~10 deg/s
• Vehicle control: ~30 deg/s
• Camera-shake correction: ~100 deg/s
• Game controllers: ~300 deg/s
• Sensing the swing of golf's top players: ~3,000 deg/s
Gyro sensors are used in products all around us.