The intelligent ball-picking robot made by Beijing No.4 Middle School Robot Group relies on camera, infrared sensor and photoelectric sensor to perceive the surrounding environment, and comprehensively uses PC image recognition, 805 1 single chip microcomputer programming, serial communication and other technologies, so that the robot can completely replace people to pick up the ball all the time during table tennis player training.
The positioning of the robot's working range of the ball is mainly accomplished by image recognition. Although the title is "Ball Inspection Robot", it is more appropriate to call it "Ball Suction Robot". Because the action of "picking up" is actually done by the negative pressure of the fan. When the ping-pong ball approaches the suction nozzle, a set of photoelectric sensors will be triggered. After the microcontroller senses the signal, it will start the fan to pump out the air in the ball collection box, and the table tennis is sucked into the ball collection box under the action of air pressure. In addition to the negative pressure ball suction system, the hardware part of the robot also includes: camera with adjustable elevation angle through electromagnetic relay, two sets of driving DC motors, a notebook computer, an 805 1 chip, and circuit parts.
Through the experience gained in joining the robot group in the past two years, we think that whether the robot can be practical, in addition to successfully completing the formulaic work, it should also be able to deal with various complicated practical situations at random. In order to make progress in practicality, in addition to accurately positioning table tennis through image recognition technology, we have made further development in the following aspects:
1. The graphic processing technology of "digital wall" is created in the program, and the area where the robot picks up the ball can be delineated by ribbon. Before each step of work, the robot will first judge whether it has stepped out of the circle, and if so, it will automatically return to the circle. Doing so can prevent the robot from going far to search for table tennis. It is called "digital wall" because the graphics processing program can make the robot ignore all objects outside the range delineated by the fading zone, just like building a wall in front of the robot. "Digital Wall" technology is the most important innovation and technical point of this work.
We put a shallow ball box with special color on the corner of the ribbon. Once the robot thinks that there is no ball in the circle after extensive search, or the ball storage bin is full, it will advance along the ribbon and finally find the carton and spit the ball into the carton.
3. There are five infrared sensors and two microswitches at the front end of the robot, which are constantly monitored by the single chip microcomputer. Once a component is triggered, the microcontroller immediately calls the corresponding obstacle avoidance program, thus realizing the force of the robot.
4. In order to meet the actual needs of various occasions, we set up two working modes when programming: the first working mode is to be in standby state after starting, and only when table tennis appears in the field of vision will it start to work normally, and then it will enter standby state again after picking up the ball, which is suitable for small venues and few table tennis; In the second working mode, there is no standby state, and the robot will continue to search for a wide range of venues at the beginning and after each release, which is suitable for situations with large venues and many table tennis.
In specific use, you will see that the intelligent ball-picking robot works as follows: If it is set to work mode 1, the robot will first enter the standby state after starting. In the standby state, the robot will alternately search for nearby and distant ping-pong balls by "bow down" and "head up", and once it finds ping-pong balls, it will enter the normal working state. Under normal working conditions, the PC can handle the position and angle of the ribbon and table tennis at any time through the camera, and send the instructions of turning and advancing to the single chip microcomputer, and the single chip microcomputer can complete various tasks according to the sent protocol. When picking up the ball, the "digital wall" program can calculate whether an action may be that the robot walked out of the ribbon, and once it is found, it will make the robot walk back to the ribbon. When there is no ping-pong ball in the field of view of the camera, the program calls the non-ball processing module, and the robot searches in the following ways: turn left 60 degrees to search-lift the camera to search again-turn right 60 degrees to search again-return to the original position and move forward 50 cm. If you are close to the ribbon, choose the best turning direction according to the angle with the ribbon to turn forward. If table tennis is found in each of the above steps, the ball picking procedure will be executed immediately. When the lap number recorded by the PC reaches four times, the robot executes the ball release program. First, the robot will advance to the vicinity of the ribbon, and then through the processing of the program, the robot will advance along the ribbon until it sees the mark of the carton, and then the robot will turn 180 degrees in place, and then reverse the car until it sees another mark prompting to put the ball, and then the robot will open the back door of the ball storage bin, and the table tennis will fall into the carton by its own gravity. After finishing the work, the two working modes will choose to enter the standby state or enter the ball-free module to continue the search.
Intelligent ball-picking robot can be regarded as a comprehensive display of the work achievements of our robot team members in the past two years. Every member has made great efforts to this end. Through this experience, we fully realized the hardships of scientific research, the satisfaction of applying what we have learned, and the fun driven by interest. It can be said that regardless of the result of the competition, we all enjoyed the happiness of scientific research.