Low-overshoot control method for tennis trainer based on active disturbance rejection control

Traditional tennis trainers employing passive return mechanisms (springs or rubber bands) suffer from fixed return angles, non-adjustable damping, inability to measure hitting speed, and monotonous training modes. To overcome these limitations, this paper presents an active return device based on a joint motor and proposes a low-overshoot control method using Nonlinear Active Disturbance Rejection Control (NLADRC). The device integrates a joint motor with an encoder, an embedded controller, and a striking target mounted on a rotating arm, enabling real-time speed calculation, adjustable damping, and precise active return. To the best of our knowledge, this is the first application of ADRC to an active return device for striking-sports training, and it constitutes the primary innovation of this work. In MATLAB simulations, NLADRC reduces the 0°→180° step-response overshoot by 82% and the post-disturbance settling time by 62.5% compared with a tuned PID controller. Hardware experiments on a prototype closely match the simulations, with a step-response overshoot of about 2.8% and a disturbance recovery time of about 0.4 s under NLADRC. A four-unit cooperative training system demonstrates sequential and random multi-target modes with audio-visual feedback, and a preliminary usability survey with 30 amateur players yields mean ratings above 4.2 out of 5 on five dimensions. These results validate the proposed device and controller and demonstrate the superiority of NLADRC over PID for this application together with acceptable preliminary usability; direct effects on tennis skill acquisition or training outcomes are beyond the scope of this study and remain to be examined in future longitudinal work.