Design and control of a tennis ball collector robot

In this study, an autonomous robot that collects scattered tennis balls in a tennis court is designed and developed. The robot perceives the balls by using a camera placed on it and starts to collect the balls starting from the nearest ones. Mechanical design is achieved with considerations given to increase ease of ball capturing and to prevent captured balls falling out. Image processing is implemented using OpenCV libraries on Raspberry Pi 3. Using edge detection algorithm and appropriate color filter, tennis balls are detected and sorted by their distance to the robot. After the generation of desired robot angle, it is converted to appropriate motor velocity values and transmitted to the motor controller unit. In order to achieve the operation, four DC motors are used. Two of them are used for platform movement, one of them is used to control camera angle for ball scanning operation, and the last one is utilized for ball capturing mechanism. On motor controller board with ARM MCU, position and velocity control of two DC motors with rotary encoders are achieved by discrete PI controllers. System design is validated through real world experimental tests.