Following the unveiling of the iPhone 16 and growing disappointment with the lack of innovation, Steve Jobs-era technological innovations such as the gyro sensor are being revisited. First introduced in the iPhone 4, gyro sensors improved the user experience of smartphones and have become an integral part of today’s autonomous driving technology, not to mention their use in aircraft and spacecraft.
A few days ago, on 12 September 2024, the American company Apple unveiled a new iPhone model, the iPhone 16. Apple has always been known for its innovative products, but this time around, the focus was on performance improvements, and it lacked the revolutionary elements that many people expected. This has led some users to express disappointment and recall the memory of Apple’s former CEO, Steve Jobs. During his lifetime, Jobs revolutionised mobile technology with the iPhone series, and is widely credited with spearheading the success of the iPhone 4.
The iPhone 4 was more than just a smartphone. At the time, the concept of a smartphone was still new, and Apple succeeded in creating a new user experience with this product. The success of the iPhone 4 led to the explosive growth of the smartphone market and made people around the world recognise the device as an essential part of their daily lives. The iPhone 4 featured a number of technological innovations, one of which was the first time a gyro sensor was incorporated into a mobile phone. The gyro sensor enhanced augmented reality (AR) technology and enabled new ways of playing games. The gyro sensor was able to accurately measure the tilt and rotation of the phone, which could be used to revolutionise the user experience.
Before Steve Jobs unveiled the iPhone 4, many people were unfamiliar with the term gyro or gyroscope. Even those with a background in physics may not have thought that the principle of a gyroscope could be applied to a smartphone. In fact, gyroscopes are devices that detect how much an object has rotated in a certain direction and have been widely used in aerial vehicles such as aircraft and spacecraft for decades. Thanks to gyro sensors, planes and spacecraft are able to fly steadily, and the technology behind them has made its way into our mobile devices and into our daily lives.
In fact, the principle of the gyroscope was already invented in the mid-19th century, and it was mainly used for military and aeronautical purposes. During the Second World War, gyroscopes were essential tools for fighter jet control and missile guidance, and later played an important role in space exploration technology. With these technological breakthroughs, gyroscopes gradually began to find commercial applications. Later, gyro sensor technology became miniaturised and popular enough to be embedded in smartphones, greatly enhancing the user experience of smart devices.
A gyroscope is a type of spinning top that is designed to spin freely in space. Several circular moulds are wrapped around the spinning top, and once the spinning top inside starts spinning, it can be placed on a thin string and not fall off the string until it stops spinning. You may remember playing this game as a child with a toy that came with an iron spinning top and a piece of string.
How can a gyroscope not fall off a thin string? The law of conservation of momentum applies to objects in linear motion. The law of conservation of momentum states that momentum, defined as , is always conserved. Similarly, the law of conservation of angular momentum applies to rotating objects. Angular momentum is defined as , and is the momentum of a rotating object. A good example of how angular momentum is always conserved is the figure skating technique of Kim Yeon-ah.
So, when the innermost spinning top of the gyroscope starts to rotate, it generates its own angular momentum. This angular momentum must be conserved, so even if the circular frame surrounding the spinning top is arbitrarily rotated, the spinning top will still maintain the axis of rotation and the speed at which it is spinning. This is why a spinning top can be placed on a thin string and still maintain its axis of rotation and speed of rotation, preventing it from falling off the string.
Based on this gyroscopic principle, a gyro sensor was designed. Inside the sensor is a high-speed spinning top, such as the innermost spinning top. Due to the law of conservation of angular momentum, the spinning top acts as the centre of gravity, which remains unchanged no matter what happens (rotation). Surround it with three circular frames, each representing the X-Y-Z axis. If the object on which the sensor is mounted is rotated by 30° in the direction of the X axis, the circular frame inside the sensor that represents the X axis will also rotate by 30° with respect to the spinning top at the centre.
So how have these gyro sensors contributed to the development of aeroplanes and spacecraft? Drivers of cars on the ground can look at objects such as trees and buildings to see if the car can keep its wheels on the ground. However, the operator of an aerial vehicle does not have a reference object such as a tree or building to look at, so there is no way to tell if the vehicle is plummeting towards the ground, upside down, inverted, or spinning in circles. Before gyro sensors, the driver had to rely solely on his or her sense of gravity to determine whether the vehicle was travelling in the correct attitude, but with the invention of gyro sensors, it is now possible to determine the correct attitude by looking at the degree of rotation of the vehicle detected by the sensor.
Furthermore, as autonomous driving technology becomes more advanced, gyro sensors are playing an increasingly important role. Not only cars, but also drones, robot vacuum cleaners, and other machines have become essential for autonomous movement. As you can see, gyro sensor technology is finding its way into more and more applications, and there’s no end in sight.
