Gyroscopes and Accelerometers: A Comparison
The gyroscope and the accelerometer are two examples of devices used to determine the position and orientation of an object. Though they are both considered sensory devices, and both similar in purpose, they measure different things.
A gyroscope is a device that uses the Earth’s gravity to determine orientation. Its simple design consists of a freely-rotating disk, called a rotor, mounted onto a spinning axis in the center of a larger and more stable wheel. As the axis turns, the rotor remains stationary to indicate the central gravitational pull, thereby denoting which direction is down. The gyroscope was invented in the 19th century and in 1909 was used to create the first auto-pilot. The accelerometer is a compact device used to measure non-gravitational acceleration. When the aircraft or other object it is integrated into goes from stationary to any velocity, the accelerometer responds to the vibrations coming from such movement. The device uses microscopic crystals that experience stress from these vibrations, and from that stress a voltage is generated to create a reading that denotes the acceleration.
The main difference between gyroscopes and accelerometers is simple: one senses rotations while the other cannot. In a sense, the accelerometer is able to gauge the orientation of a stationary item in relation to Earth's surface. When accelerating in a specific direction, the accelerometer is unable to distinguish between that and the acceleration resulting from Earth’s gravitational pull. This makes them less appealing for use in aircraft. The gyroscope maintains its effectiveness by measuring the rate of rotation around a given axis. When gauging the rate of rotation about the roll axis of an aircraft, the device identifies an actual value until the object stabilizes. This differs from the accelerometer, which measures linear acceleration based on vibration.
A typical two-axis accelerometer provides users with a direction of gravity in an aircraft, smartphone, car, or other device. Adversely, a gyroscope is intended to determine an angular position based on the principle of rigidity of space, which states that a gyroscope remains in a fixed position in the plane in which it is spinning. Despite the similar purposes of accelerometers and gyroscopes, their applications vary drastically. Gyroscopes are used in navigation of unmanned aerial vehicles, compasses, and boats, where they provide stability in navigation. Accelerometers have equally widespread uses and can be found in engineering, machinery, hardware monitoring, building, as well as structural monitoring, transport, and even consumer electronics.
The increased commonality of accelerometers in the consumer electronics market, thanks to the introduction of smartphones and other devices with built-in compass apps, has led to an increase in its popularity in all types of softwares. Smartphones rely on accelerometers for functions such as determining screen orientation, acting as a compass, and doing/undoing actions by shaking the phone. Recently, the use of accelerometers has even extended into laptops.
The practicality of gyroscopes or accelerometers ultimately depends on the intended end use of each device. Many devices benefit from the use of both, but most rely on the use of only one. Whether you need to determine acceleration or orientation, each device will provide different results.