Nine-axis sensor, nine-axis somatosensory tracking and sensing chip. More and more VR are promoting the concept of "nine-axis sensors", which seems to be the new standard for VR hardware. What exactly is a nine-axis sensor? How does it work?

What is a nine-axis sensor

A sensor is a detection device that can sense the information being measured and convert the information into electrical signals according to a certain rule for transmission, processing, storage, display, recording, etc. There are many types of sensors, such as sound sensors (common voice-activated lights), temperature sensors (electric kettles), etc., which are widely used in various electronic products.

The so-called nine-axis sensor is actually a combination of three types of sensors: a 3-axis acceleration sensor, a 3-axis gyroscope, and a 3-axis electronic compass (geomagnetic sensor). The three parts have different functions and cooperate with each other. They are motion sensing and tracking components commonly used in electronic products such as mobile phones, tablets, and game consoles. They are used for interactive control in various software and games.

Acceleration sensor

Acceleration sensors measure acceleration in all directions in space. It uses the inertia of a "gravity block". When the sensor is moving, the "gravity block" will generate pressure in the X, Y, and Z directions (front, back, left, up, down), and then use a piezoelectric crystal to convert this pressure into With the change of the motion, the pressure in each direction is different, and the electrical signal is also changing, so as to determine the acceleration direction and speed of the mobile phone. For example, if you suddenly push the phone forward, the sensor knows that you are accelerating forward.

Gyro

A gyroscope is a device used to measure angles and maintain direction. In flying games, sports games, and first-angle shooting games, you can completely monitor the player's hand displacement to achieve various game operation effects. The figure below is a most basic model of a mechanical gyroscope. In the movement of the entire instrument, the gold rotor in the middle is not affected by the inertia effect, and the three "steel rims" around it will change due to the change of attitude of the device.

To detect the current rotation state of the device.

In fact, the gyroscope in our electronic products such as mobile phones does not look like this. It is also a microelectronic component like the acceleration sensor. It uses Coriolis force to change the state of the circuit by the movement of the vibrator in the continuous vibration of the rotating system, causing changes in related electrical parameters, which can reflect the left and right tilt, Exercises such as tilting back and forth and swinging left and right.

Electronic compass (geomagnetic sensor)
Using acceleration sensors and gyroscopes, the complete motion state of the device can be basically described. However, with long-term exercise, cumulative deviations will also occur, which cannot accurately describe the movement posture, such as the tilt of the control screen. The electronic compass (geomagnetic sensor) uses the measurement of the earth's magnetic field and corrects and compensates through the absolute pointing function, which can effectively solve the cumulative deviation, thereby correcting the human's movement direction, attitude angle, movement intensity and speed.
The sensor needs to cooperate with the algorithm program

As an integrated sensor module, the nine-axis sensor reduces the circuit board and the overall space, and is more suitable for lightweight and portable electronic devices and wearable products. In addition to the accuracy of the device itself, the accuracy of the integrated sensor's data also involves correction after welding and assembly, and supporting algorithms for different applications. Appropriate algorithms can fuse data from multiple sensors, and make up for the shortcomings of a single sensor in calculating accurate positions and directions, thereby achieving high-precision motion detection.

Application of nine-axis sensor in VR

Nine-axis sensor has been used in high-end mobile VR products such as Dodore H1. It is different from the Carboard toy VR with dozens of yuan on the market. It has its own sensor and real-time sampling, and uses complex fusion operations to improve accuracy and reduce errors , Greatly improving the experience of VR, especially in terms of somatosensory interaction, gaming and other advantages. Today, sensors as the threshold for mobile VR have become an important selection criterion for consumers to buy VR products.