What Is a MEMS Gyroscope?
A MEMS gyroscope is a device created using MEMS technology.
MEMS stands for ‘Micro Electro Mechanical Systems.’ A Gyroscope, also called a gyroscope sensor or gyro, is a sensor that detects the motion of an object and measures the change in angle per unit of time.
Applications of MEMS Gyroscopes
MEMS gyroscopes are electronic devices used in ship attitude heading control, construction equipment control, and automotive navigation and body stability systems. In these applications, the attitude and azimuth angles of objects are detected.
Devices familiar to us include smartphones, digital cameras, and game consoles. There are many applications that move according to the movements of smartphones, and MEMS detects these movements.
MEMS gyroscopes are used in the motion detection of game console controllers and in the image stabilization function of digital cameras. Drones, which have become popular in recent years, are another typical device which relies on MEMS Gyroscopes for its function.
In reality, however, attitude is controlled by an inertial measurement unit (IMU), which also includes a gyro sensor.
MEMS Gyroscope Principle
Most MEMS gyroscopes use the Coriolis force. The Coriolis force is a force acting orthogonally to the direction of vibration and the axis of rotation of a vibrating object when the object is rotated.
For example, if an object of mass m moving at each velocity ω tries to move at velocity V, a Coriolis force of magnitude 2mVω acts in the direction orthogonal to the axis of rotation and velocity. m is a very small machine in MEMS, so the mass m is also very small, but the velocity V can be a large value because the resonance frequency is high. Velocity V can be large because of the high resonance frequency.
In a vibrating MEMS gyroscope, the MEMS element is subjected to vibration and the Coriolis force is detected when ω is applied externally as a rotational motion. For example, a capacitive MEMS gyroscope captures the change in capacitance that occurs when the Coriolis force acts on the electrodes of a comb structure.
While mechanical gyroscopes that are not MEMS gyroscopes use the “Koma principle,” MEMS gyroscopes are predominantly vibration-based.
Types of MEMS Gyroscopes
MEMS gyroscopes are chosen based on the application and conditions of use, but there are four types of gyroscopes in terms of structure. These can be classified into four types according to the structure of what receives the Coriolis force: beams, sounders, plates, and rings.
Other Information on MEMS Gyroscopes
Differences from IMUs
MEMS gyroscopes are used in our everyday devices such as smartphones, but recent technology uses an inertial measurement unit called an IMU. In addition to drones, which are listed in the “uses” section, IMUs are also being used in areas such as automated vehicle driving, agriculture, and remote control of construction equipment.
In addition to gyros, IMUs incorporate acceleration and temperature sensors. Our three-dimensional world can be generally described by translational and rotational motions of three orthogonal axes, represented by x, y, and z, respectively. A gyroscope is a sensor unit that detects rotational motion of these three axes.
An accelerometer is a sensor unit that detects the translational motion of the three axes. The IMU integrates these sensor units and performs various corrections among the sensors. The IMU provides more stable and accurate control than when single sensor units are used independently.