| Introduction
For most people who hear about motion capture for the first time, motion capture sounds like an "advanced" and "indistinct" term. As a communication bridge between virtual and reality, it is used in a wide range of fields such as scientific research, film and television production, virtual anchor, sports, gait analysis, etc., providing a solution for virtual reality applications. In recent years, with the introduction of the metaverse concept, more and more users are involved in motion capture, and the core highlights of motion capture have undoubtedly become the focus of attention. How to give full play to the advantages of motion capture and let users understand its characteristics more clearly is the purpose of this article.
Motion capture topic
First of all, when it comes to inertial motion capture systems, there will be questions. What is inertial motion capture? Inertial motion capture is a new type of human motion capture technology. It uses inertial sensors to capture the motion data of the target object, and uses wireless transmission to present the data in the upper computer software, and finally establishes a 3D model, and makes the 3D model follow the movement. Objects move. It is precisely because of the low cost, convenient use and high adaptability of the inertial motion capture system that it is favored by users.
Composition of inertial motion capture system
inertial sensor
The inertial sensors are connected wirelessly, avoiding the constraints of wires. Using 400mAh polymer lithium-ion battery, the battery life is about 3 hours. Each sensor adopts 2.4GHz/5.8GHz dual-frequency communication, which solves the problem of communication congestion well, avoids the loss of a large number of key data frames, and the movement accuracy will not decrease after working for a long time.
Each inertial sensor is added with a barometer so that the motion capture system can capture the human body's feet off the ground at the same time, jumping and other actions. The data fusion uses the EKF (Extended Kalman Filter) algorithm to perform in-depth data fusion of acceleration, angular velocity, and magnetic force values, thereby outputting high-precision attitude data. And each inertial sensor also adds anti-magnetic interference algorithm to make it adapt to a certain magnetic field interference environment.
Each inertial sensor has gone through processes such as temperature compensation, vibration test, and zero point calibration, so that the quality is guaranteed.
| serial number | name | parameter |
| 1 | static precision | Roll/Pitch≤0.5° Yaw≤1° |
| 2 | Acceleration measurement range | ±16g |
| 3 | Angular velocity range | ±2000dps |
| 4 | Angular measurement resolution | 0.02° |
| 5 | Attitude measurement range | Three axis 360deg |
| 6 | Maximum update rate | 100fps |
| 7 | Wireless transmission frequency band | 2.4GHz/5.8GHz |
| 8 | size | Diameter: 44mm Height: 16mm |
| 9 | weight | 20g |
charging strip
The charging strip can charge 17 inertial sensors at the same time. When using it, first insert the plug of the power adapter into the charging base, then insert the power plug at the other end, and then press the "round" switch button of the socket. When the button and the inertial sensor light are on at the same time, it means that the sensor starts to charge normally, and it takes about 2 hours to fully charge.
Actual drawing of charging socket
| serial number | name | parameter |
| 1 | weight | 670g |
| 2 | size | Diameter: 230mm Thickness: 37mm |
| 3 | Input voltage | 12V |
| 4 | Input Current | Minimum 3A |
router
The router serves as a hub for receiving inertial sensor signals, synchronizing inertial sensor time, managing data retransmission, synchronizing third-party equipment, and communicating with PC-side software. It supports wireless time synchronization with the inertial sensor, and the synchronization accuracy is less than 10 microseconds. When the inertial sensor is turned on, it will automatically search for the wireless synchronization signal of the router to synchronize its own clock.
| serial number | name | parameter | Remark |
| 1 | Communication method with sensor | 2.4GHz/5.8GHz wireless dual frequency |
Custom wireless protocol Non-standard WiFi protocol |
| 2 | Communication Interface | 10/100Mbps Ethernet category 6 or above network cable |
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| 3 | Power supply | 5A 3A adapter for IEEB 802.3af/at-2003 POE or Typc-C interface |
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| 4 | Synchronization input interface | 1 way BNC interface | Isolated input interface |
| 5 | Synchronous output interface | 4 BNC ports | Non-isolated output interface |
| 6 | weight | 350g | |
| 7 | size | 260×100×41mm |
MotionVenus® software
MotionVenus® is the upper computer software system of FOHEART MAGIC. Its main functions include equipment management, data processing, posture fitting, data forwarding, data fusion of third-party equipment, video recording, real-time display of 3D characters, real-time display of various data and forwarding data.
new features
01/Router and sensor support data synchronization
Wireless time synchronization is supported between the router and the inertial sensor, and the synchronization accuracy is less than 10 microseconds. When the inertial sensor is turned on, it will automatically search for the wireless synchronization signal of the receiver to synchronize its own clock. And the receiver provides two BNC interfaces: isolated synchronous input and non-isolated synchronous output.
02/Dual frequency communication
The router and the sensor support 2.4GHz/5.8GHz dual-frequency data communication, and support manual/automatic channel switching. There are a total of 39 wireless channels that can be used (please refer to local laws and regulations for specific allowed channels). Among them, channels 1~13 are 2.4GHz channels, and channels 14~39 are 5.8GHz channels. The mapping table between the channel number value and the real physical channel is as follows:
03/Third-party devices can be connected
Third-party equipment can be connected, such as: data gloves, surface electromyography, plantar pressure plates, etc.
04/Support multiple sets of simultaneous display
One MotionVenus® host computer software supports multiple sets of motion capture devices to be used at the same time, and multiple sets do not need to open multiple software. The software shows that the theory of the number of 3D characters is not online, but the number of motion capture devices connected to the router. When multiple sets of equipment are used at the same time, the corresponding character models will be displayed on the screen, and each set of equipment can be operated independently.
05/Video synchronous recording
The host computer software can be connected to an external camera and can record video at the same time.
06/Firmware upgrade
After the firmware program of the inertial sensor or router is upgraded, the hardware firmware can be upgraded through the function module. This is very helpful for hardware and software optimization and debugging.
Application field
Finally, with the rise of the metaverse concept, virtual reality technology is booming, and inertial motion capture technology has shown its unique flash points in emerging industries. In the future, Fuxin will definitely create more surprises for everyone in terms of motion capture~
Source of some pictures: Internet
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