How has gyroscope technology changed smartphones? We look at the innovation from the introduction of the gyro sensor in the iPhone 4 to its application in various fields.
On September 12, 2024, Apple introduced a new iPhone model, the iPhone 16. Apple has always introduced innovative products, but this product is also said to have focused on improving performance and lacked the innovative elements that many people expected. As a result, some users are expressing disappointment reminiscent of former Apple CEO Steve Jobs. He led the innovation of mobile technology through the iPhone series during his lifetime, and is widely known for spearheading the success of the iPhone 4.
The iPhone 4 was more than a smartphone. At the time, the concept of a smartphone was unheard of, and Apple was able to create a new user experience with this product. The success of iPhone 4 led to explosive growth in the smartphone market and helped people around the world see smartphones as a necessity in their daily lives. iPhone 4 featured a number of technological innovations, including the first gyro sensor in a mobile phone. This gyro sensor enhanced augmented reality (AR) technology and enabled new ways to play games. The gyro sensor allowed the phone to accurately measure the degree to which it was tilted or rotated, revolutionizing the user experience.
Until Steve Jobs unveiled the iPhone 4, many people were unfamiliar with the terms gyroscope or gyro sensor. Even people with a background in physics would not have thought that the principles of a gyroscope could be applied to a smartphone. In fact, gyroscopes are devices that detect how much an object has rotated in a given direction and have been widely used in aircraft and spacecraft for decades. Gyro sensors have made it possible for airplanes and spacecraft to fly stably, and technologies that apply this technology have advanced to mobile devices and become a part of our everyday lives.
In fact, the gyroscope principle was invented in the mid-19th century and was used primarily for military and aeronautical purposes. During World War II, gyroscopes were essential tools for controlling fighter planes and guiding missiles, and they later played an important role in space exploration technology. Through these technological innovations, gyroscopes gradually began to be used for commercial purposes. Later, the miniaturization of gyro sensor technology and its popularization to the point where it could be installed in smartphones led to a significant improvement in the user experience of smart devices.
A gyroscope is a kind of spinning top designed to rotate freely in space. Several circular frames surround the top, and when the inner top starts spinning, it will not fall off the frame until it stops spinning, even if it is placed on a thin string. You may remember playing with a toy that had an iron top and a string when you were a child.
How does a gyroscope not fall off a thin string? The conservation of momentum law applies to objects that move in a straight line. The conservation of momentum law states that momentum, defined as “the mass of an object times the velocity of the object,” is always conserved. Similarly, the conservation of angular momentum applies to objects that rotate. Angular momentum, defined as “the mass of a rotating object × the rotational speed of the object × the distance between the object and the axis of rotation,” refers to the momentum of a rotating object. A good example of how this angular momentum is always conserved is the figure skating technique of figure skater Yuna Kim.
Therefore, when the top of the spinning top begins to rotate, angular momentum is generated that is unique to the top. Since the angular momentum generated must be maintained, the top maintains its axis of rotation and speed even if the circular frame surrounding the top is rotated arbitrarily. Therefore, even if the spinning top’s axis of rotation is placed on a thin string, its axis of rotation and rotation speed will be maintained so that it will not fall off the string.
Based on the principle of such a gyroscope, a gyro sensor was invented. Inside the sensor, there is a top that rotates at high speed like a top. The top that rotates at high speed acts as a center that does not fluctuate (rotate) under any circumstances due to the conservation of angular momentum. The area is surrounded by three circular frames, each of which represents the X-Y-Z axes. If an object equipped with this sensor rotates 30° in the direction of the X axis, the circular frame representing the X axis inside the sensor also rotates 30° relative to the central spindle.
So how did these gyro sensors contribute to the development of airplanes and spacecraft? Drivers of cars moving on the ground can see objects such as trees and buildings and know whether the car is running smoothly with its wheels on the ground. However, because airborne vehicle operators cannot see reference objects such as trees and buildings, they have no way of knowing whether the vehicle is heading upside down, upside up, or spinning in a circle. In the days before gyroscopes, drivers had no choice but to rely entirely on their body’s sense of gravity to determine whether they were operating in the correct position. But after the invention of gyro sensors, drivers were able to operate in the correct position by looking at the degree of vehicle rotation detected by the sensor.
Furthermore, as autonomous driving technology continues to advance, gyro sensors are playing an increasingly important role. Gyro sensors have become an essential technology for the autonomous movement of various machines, including not only cars, but also drones and robot vacuum cleaners. As such, gyro sensor technology is being applied to more and more fields, and its scope is likely to expand indefinitely in the future.
