MEMS Gyroscope Basics and Operation

This page covers MEMS Gyroscope basics and its working operation. It outlines technical specifications, applications, and different types of gyroscopes.

Definition: A Gyroscope is a device used for navigation and angular velocity measurement. A MEMS (Micro-Electro-Mechanical System) gyroscope utilizes a very small vibrating mechanism to detect changes in orientation. These gyroscopes can measure rotational velocity along one, two, or three axes. A 3-axis accelerometer can be used to implement a 3-axis gyroscope.

Sensors are integral to gyroscope implementation. Figure 1 illustrates a simple gyroscope.

The following technical specifications are crucial for determining the performance of a gyroscope. Selecting the right gyroscope depends on the intended applications:

• Size and Mass
• Cost
• Operating Temperature Range
• Shock Survivability
• Range of Measurement
• Number of Sensing Axes
• Nonlinearity
• Bandwidth
• ARW (Angular Random Walk)
• Bias, Bias Drift, and Bias Instability

Image alt: MEMS gyroscope

What is a Gyroscope?

A Gyroscope is a device used to measure or maintain orientation. It operates on the principles of angular momentum, where the initial axis of rotation is conserved. It generally consists of a spinning mass on an axle. The following sections detail how common mechanical and electronic gyroscopes function.

Mechanical Gyroscope

A mechanical gyroscope uses a spinning mass mounted on gimbals and sensors on an axis to detect rotation.

Electronic Gyroscope

Also known as a Coriolis Vibratory Gyroscope, it uses a proof mass fed with oscillating current to induce vibrations. The vibrating mass tends to oscillate in its initial plane of reference. When rotated, oscillations in the orthogonal plane are detected by the circuitry.

Types of Gyroscopes

Here are some of the most common types of gyroscopes:

• Rotary gyroscope: A rotor suspended in a gimbal spins independently to conserve angular momentum. These are mostly unused in modern systems.

• Fiber optic gyroscope: A fiber optic coil determines changes in orientation by analyzing the path of light within the coil. A beam traveling against the rotation has a slightly shorter path.

Other types of gyroscopes include the Draper Tuning Fork Gyroscope, Piezoelectric Plate Gyroscope, Laser Ring Gyroscope, and Micro Laser Gyroscope.

Applications of Gyroscopes

Gyroscopes have a wide range of applications:

• Used in gyrocompasses on ships to determine the true north direction.

• Used in bicycles and Hubble Space Telescopes to provide stability assistance.

• Used in inertial guidance systems for guided missiles to measure angular velocity in an inertial reference frame and to detect changes in orientation.

• Used in consumer electronics for various purposes, such as free-fall detection in laptops and screen orientation in smartphones.