On the undulating snow-capped mountain track, skiers gallop by, and the transmission of data information such as their location and state of movement needs to overcome challenges such as low temperatures and complex terrain. The research team of Beijing Institute of Technology used the "three-dimensional perception and reconstruction technology of winter project scenes" to develop a UAV on-board lidar scanning system suitable for low-temperature environment operation, realizing the real-time transmission of high-precision reconstruction snow fields and training data, and providing technical support for the national team to prepare for the Winter Olympics.
Zhang Haiyang and his research team
Tailor-made "simulated snow field"
"You see, athletes turn sideways on the slopes, curl up and squat, jump and undulate... Every subtle movement is clearly represented. Zhang Haiyang, associate professor of the School of Optoelectronics of Beijing Polytechnic Institute, is displaying the scene of Chongli Ski Resort built with a three-dimensional lidar scanning system on an electronic screen, and two drones equipped with lidar systems are placed next to him.
Drones equipped with lidar systems
By measuring the data of the three-dimensional scenes of ski jumping, alpine skiing, cross-country skiing and other projects, the scientific research team uses virtual reality technology to display the scene information, combined with the real-time tracking data of the athletes, and restores the real scene of the slope.
Since each project has its own technical characteristics, the team also needs to tailor a "simulated snow field" to the needs of the athletes and coaches. Zhang Haiyang gave an example: "The alpine ski team pays special attention to the speed and position change of athletes entering and leaving the flag gate, so we have to specifically measure the position of each flag gate and calculate the change in the speed of the athlete through the flag gate, so that the data is clearly presented in front of the coach." ”
Just measuring takes a lot of effort. When the temperature on the snowy mountain is too low, the drone fails. The researchers had to carry the lidar to measure section by section. "It is common for the snowy mountains to be windy, the temperature is low, the blowing makes people's bones hurt, and the legs and feet freeze unconscious." He said that the boys in the team were responsible for moving the equipment, and the girls were on the side to record, scanning one point and then the next point.
Look for signals that are "disappearing"
"No matter how hard it is, you have to stick to it." Zhang Haiyang explained that previously, once skiers entered the icy track, it was difficult for coaches to grasp their position, "even if a signal base station is set up on the snowy mountain and a transmitter is installed on the athlete, the signal is like playing 'hide-and-seek' with us, looming in the trees and peaks." ”
However, mastering the sports details of athletes, such as the distance between the snowboard and the flag gate when alpine skiers pass through the flag gate, the angle at which the bobsleigh enters the bend, and the relative position of the athletes with the ground when they vacate, are of great significance for athletes and coaches to fully grasp the situation of the track and carry out effective and scientific training and guidance. "The job we have to do is to restore the 'disappearing' signal." Zhang Haiyang said.
Finding signals is actually accurately locating athletes. "Skiing is fast, athletes can reach speeds of up to 140 kilometers per hour, and it is difficult to achieve positioning." He said that after repeated experiments, the scientific research team used high-speed cameras, high-frame-rate transmitters, and the Beidou positioning system to cooperate with fixed base stations to improve the positioning accuracy to about 5 centimeters.
Help prepare for the Winter Olympics
At present, the position information of athletes can be transmitted to the cloud server in real time through sensors with 5G modules, and directly obtained on the mobile terminal. "Communication efficiency has been greatly improved, and the slope, length, speed of athletes, acceleration, taxiing distance, turning radius and other data of the slope can be quickly calculated and presented to the coach in time."
Nowadays, the relevant achievements of "three-dimensional perception and reconstruction technology of winter project scenes" have been applied to the daily training of the national team and provided technical support for the national team's preparation for the Winter Olympics. "The three-dimensional construction of the snow field with the athlete's high-precision sports information can help the coach correct the training movements, improve the training efficiency of the athletes, and can also be used for indoor simulation training."
Zhang Haiyang revealed that the relevant technology is being continuously updated, and in the future, it will realize multiple uses such as synchronous measurement and accurate positioning, athlete training routes and playback control of actions.