In the wave of the continuous evolution of smart wearable devices, the 6 DOF IMU sensor has become the core force driving the development of this field with its excellent performance and wide applicability, bringing users unprecedented experience improvement and function expansion.
Analysis of the working principle of the 6 DOF IMU sensor
The 6-DOF IMU sensor comprises three single-axis accelerometers and three single-axis gyroscopes working closely together.
The accelerometer’s working mechanism works according to Newton’s second law. When an object moves, the mass block inside the accelerometer will generate a force due to acceleration. By detecting the force exerted on the mass block on the three independent axes of the carrier coordinate system, it is converted into a corresponding acceleration signal. These acceleration signals can be integrated to obtain the speed change of the object, and the position information of the object can be obtained by integrating again. For example, when the wearer of the smart wearable device starts running, the accelerometer can keenly capture the acceleration changes of the body in the front, back, left, right, and up and down directions, providing a basis for subsequent motion data calculations.
Working principle of gyroscope: The gyroscope operates based on the principle of conservation of angular momentum. When the carrier rotates, the rotating element inside the gyroscope will maintain its angular momentum. By detecting the change of this angular momentum, the angular velocity signal of the carrier relative to the navigation coordinate system can be measured. After the integration operation, the carrier’s attitude information, such as rotation angle, direction, etc., can be obtained. Taking smart glasses as an example, when the user turns his head, the gyroscope can quickly sense the angular velocity of the head, thereby providing accurate data for operations such as adjusting the screen display direction.
The two complement each other. The accelerometer is responsible for measuring linear acceleration, and the gyroscope is responsible for measuring angular velocity, so that the 6-DOF IMU sensor can measure the motion state of objects in three-dimensional space in an all-round and accurate manner, providing accurate perception data support for smart wearable devices.
Multiple applications in smart wearable devices
Deep insights into motion monitoring and analysis
- Accurate motion data recording: In smartwatches, sports bracelets, and other devices, the 6-DOF IMU sensor is an “expert” in motion data recording. In running, it can accurately record the frequency of steps, calculate the time interval of each step by analyzing the changes in acceleration and angular velocity between adjacent steps, and then obtain an accurate step frequency. At the same time, according to the displacement and acceleration information of the body during exercise, the stride size can also be accurately measured. For cycling, IMU sensors can monitor the inclination angle, turning speed, etc. of the bicycle, and provide the rider with riding posture and route information.
- Sports posture evaluation and correction: With the help of IMU sensors to monitor sports posture in real-time, smart wearable devices can provide users with sports posture evaluation. For example, when swimming, the sensor can analyze the angle, strength, and frequency of arm strokes and leg kicks to determine whether the user’s swimming posture is standard. If it is found that the user’s arm stroke angle is too large during freestyle or the leg kicking action is not standardized during breaststroke, the device will issue a reminder in time to help the user correct the exercise posture, improve the exercise effect, and reduce the risk of injury.
- Sports goal setting and achievement analysis: Based on the large amount of exercise data collected by IMU sensors, smart wearable devices can develop personalized exercise plans for users based on their sports ability and goals. For example, a plan to gradually increase exercise intensity and distance is set for running enthusiasts who want to improve their endurance, and feedback on the user’s exercise progress through real-time monitoring of exercise data to motivate users to achieve their exercise goals.
Innovative experience of posture detection and interaction
- Natural interaction of smart glasses: In the application of smart glasses, the 6-DOF IMU sensor makes the interaction between users and devices more natural and smooth. When users wear smart glasses to view maps, the rotation of their heads will be accurately captured by the IMU sensor. The device automatically adjusts the display direction of the map based on the posture information transmitted by the sensor to keep the direction of the map consistent with the direction of the user’s line of sight. When browsing web pages or viewing documents, users can turn pages and scroll pages through simple actions such as nodding and shaking their heads, without manually touching the screen, providing a more convenient user experience.
- Enhanced immersive experience of AR/VR headsets: In the field of AR/VR, IMU sensors are the key to creating an immersive experience. When users wear AR/VR headsets, every subtle movement of their heads will be quickly sensed by the IMU sensor and converted into electrical signals. When users turn their heads in a virtual environment, the sensor will transmit the head’s rotation angle and direction information to the device in real-time, allowing the virtual scene to be updated at an extremely fast speed, making users feel that they are really in the virtual world.
Intimate protection assisted by health monitoring
- Daily activity status monitoring: The 6-DOF IMU sensor can accurately identify the user’s daily activity status. By analyzing the changing characteristics of acceleration and angular velocity, the device can accurately determine whether the user is standing, sitting, walking, or running. In addition, based on the duration and activity intensity of the user in different states, the user’s daily exercise volume is evaluated, and a comprehensive activity report is provided to the user to help the user understand whether their lifestyle is healthy.
- Sleep quality assessment: In terms of sleep monitoring, IMU sensors play an important role. During the user’s sleep, the sensor monitors information such as the body’s micro-movements and the frequency of turning over. When the user is in a light sleep state, the body’s movements are relatively more and the frequency of turning over is higher; while in a deep sleep state, the body’s movements will be significantly reduced. By analyzing these data, smart wearable devices can accurately determine the user’s sleep stage and provide users with detailed sleep quality reports, including light sleep time, deep sleep time, number of awakenings, etc., to help users better understand their sleep conditions and adjust their sleep habits.
- Fall detection and emergency rescue: For the elderly or people with limited mobility, the IMU sensor in smart wearable devices can monitor the body’s movement status and posture changes in real-time. When it detects that the user may fall, the sensor will quickly transmit the relevant data to the device’s processing chip. After algorithm analysis and confirmation, the device will automatically sound an alarm and send a distress message and the user’s location information to the preset emergency contact to buy time for timely rescue.
Precise guidance with enhanced navigation and positioning
- Indoor positioning assistance: In indoor environments, GPS signals are often limited and the positioning accuracy is low. At this time, the 6-DOF IMU sensor can be combined with other indoor positioning technologies (such as Bluetooth positioning, Wi-Fi positioning, etc.) to achieve more accurate indoor positioning. The IMU sensor monitors the user’s walking steps, stride length, and direction changes in real-time, calculates the user’s approximate position and movement trajectory indoors, and provides navigation services for users in large indoor places such as shopping malls, hospitals, and airports, helping users quickly find their destination.
- Outdoor sports navigation optimization: In outdoor sports, the IMU sensor can detect the user’s movement direction and posture changes in real-time, providing more accurate information for the navigation system. When users are hiking or climbing in mountainous areas or places with weak signals, IMU sensors can assist GPS positioning and improve positioning accuracy and stability. Even if the GPS signal is temporarily interrupted, the IMU sensor can continue to provide users with approximate location and direction guidance based on the previously acquired location and motion data to ensure that users do not get lost.
Future Development Trend Outlook
- Continuous breakthroughs in technical performance: With the continuous advancement of technology, the accuracy of 6-DOF IMU sensors will continue to improve, and they will be able to more accurately measure tiny changes in acceleration and angular velocity, providing more accurate data support for smart wearable devices. At the same time, the size of the sensor will be further reduced, and the power consumption will be lower, which enables smart wearable devices to integrate more advanced sensor technology without increasing the volume and weight, thereby improving the overall performance and user experience of the device.
- Deep integration with other technologies: In the future, 6-DOF IMU sensors will be deeply integrated with technologies such as artificial intelligence, big data, and 5G. By analyzing and learning the large amount of data collected by IMU sensors through artificial intelligence algorithms, smart wearable devices will be able to more intelligently understand users’ behavioral habits, health conditions, and needs, and provide users with more personalized and intelligent services.
The 6 DOF IMU sensor has become an indispensable key technology in the field of smart wearable devices due to its multi-dimensional applications and excellent performance. The continuous innovation and development of technology, it will bring more possibilities to smart wearable devices, bring more convenient, intelligent, and healthy experiences to people’s lives, and lead smart wearable technology to a new height.
