Editor's Note: Author GZ, Gina Micro Technology Director, Master of Xi'an University of Electronic Science and Technology, majoring in Control Theory and Control Engineering. He has participated in the important topic of national inertial navigation products as a backbone, and the research results have been successfully applied to the military industry. Currently responsible for the team's technical route and product technology research and development, for the spatial positioning of the inertial navigation, ultra-wideband, laser, visual SLAM are slightly involved. In this article, the author talks about the micro-inertial positioning scheme with his own work experience, and why the reason behind choosing this scheme.
When it comes to positioning navigation, the first thing that people think of is GPS. China has also launched its own satellite positioning system Beidou satellite positioning system. However, satellite positioning can only be used in outdoor environments. Once indoors, satellite positioning cannot be used because the navigation signal decays too fast.
So, is there any “just need†for indoor positioning? The answer is yes. Today we are not talking about the very busy consumer market applications. We talk about the application of indoor positioning technology in some special but important scenarios - fire rescue, counter-terrorism, emergency rescue and other emergency tasks.
Special requirements for indoor positioning technology for emergency tasks such as fire rescueImagine a scene like this: At the scene of the fire, firefighters rushed into the building in the fire to try to search for survivors. The fire was getting more and more fierce, the smog was filled, the firefighters lost their way to the exit, the oxygen was not enough, and they eventually lost their lives...
If the position of the firefighter can be accurately located, the rear commander grasps the real-time movement of the firefighters who enter the fire field to rescue the field personnel, and provides accurate command to the field personnel through the communication equipment to prevent the firefighters from getting lost in the fire field, which can minimize the casualties. This is also a merit for indoor positioning technology.
At present, mainstream indoor positioning technology generally requires external facilities or a priori database, such as UWB, WiFi, Bluetooth, geomagnetic, etc., and emergency tasks such as fire rescue are usually too late or the environment does not allow external positioning of base stations or beacons, so there is no one. It can meet the requirements of autonomous positioning under emergency tasks, so the use of inertial navigation technology that does not depend on any external equipment or a priori database is a relatively safe means. Inertial navigation technology is a completely autonomous navigation technology. Unlike ordinary positioning technology, it does not rely on any auxiliary equipment and a priori database such as navigation satellites, wireless base stations, and electronic tags.
For the indoor positioning requirements of emergency missions, whether the positioning products can achieve actual combat effects should be evaluated or actually tested from the following aspects:
1. Whether it can adapt to a variety of gaits, typical gait has small steps, trotting, side shifting, retreating, going up and down, etc.;
2. Walk more than 50 meters along the long straight line, turn to more than 5 circles at the end (with a radius of 2 meters or more), and then walk back along the original straight line to evaluate the offset. If the offset is controlled within 1%, it is an excellent product. Inertial navigation has fixed angles and positional drift that cannot be eliminated, and can only be reduced as much as possible;
3, repeatedly up and down the stairs, to assess the high accuracy, especially the floor judgment, to see if there will be floor errors, small errors can be accepted, but the floor error will delay the rescue or even cause fatal errors;
4. Perform field tests in buildings. The magnetic field is an important information for the positioning of the inertial navigation system and can be used to control the drift of the inertial navigation. However, it is also susceptible to external influences, especially when the building is relatively compact, the metal structure is relatively large, and there is a large display environment, and the magnetic field anti-interference characteristics of the positioning product should be evaluated;
5. The ignition test can be carried out under conditions. The fire will cause a sharp change in temperature and airflow. If the data fusion of the barometer is not handled well, the height will be greatly deviated. The simple test method is to adjust the indoor and outdoor temperature difference through the air conditioner. Stability of external test positioning;
6. Whether it is convenient to use, whether it needs external base station assistance, it can be evaluated. In emergency tasks such as fire rescue, it cannot rely completely on any external base station. Our micro-inert navigation positioning product GNW-FOEM can maintain 45 without the assistance of external base station. The accuracy of about a minute is available, and it is superior in similar products;
7, the advantages and disadvantages of the map fusion algorithm, no map and map use situation assessment, our iNav intelligent positioning engine provides a map input interface, in the presence of indoor map information, can maintain high precision without drift for a long time, do The typical test was in the mall, the accuracy was stable at 2 meters in 1 hour;
8. The choice of data communication methods is roughly divided into two types. One is to use the carrier network to transmit (using the coverage redundancy of the basic network and its robust communication mechanism), and the other is to use the private network, but currently There is no one that can be quickly deployed and is easy to wear. It can cover the dedicated communication network of fire rescue (usually it can achieve the performance standard when it covers the underground floor). If the product is compatible with the carrier network and the private network, it is already a kind. A better way.
A more feasible product configuration scheme is 1 master + 4-8 individual node configurations, as shown in the figure:
Figure 1 Emergency mission site command system plan
Each individual soldier is equipped with a positioning module (foot) and a handheld terminal. After acquiring the personnel motion data, the module transmits the data to the handheld terminal through Bluetooth communication, and the handheld terminal transmits the data to the command center through the far field communication device. The system can be integrated into the indoor map with a horizontal accuracy of 0.3% and accurate floor recognition. On-site and back-field multiple command terminals can be displayed simultaneously, which is conducive to firefighters on-site command and dispatch, reduce the number of casualties, and can realize task playback afterwards, and carry out teaching and experience summary.
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