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Trajectory control of two-degree-of-freedom sweet potato transplanting robot arm

To address the poor performance of the existing sweet potato transplanting robots, in this paper, a two-degree-of-freedom sweet potato transplanting robot arm is proposed to improve the transplanting success rate and production yield. Different transplanting strategies, including vertical transplanting, boat-shaped transplanting, and inclined planting, can be achieved for different terrain types. The designed transplanting mechanical arm can achieve both vertical and rotational movement of the seedling claw through the vertical sliding motor and the rotating motor respectively. With the two degrees of freedom, the designed transplanting robot arm can complete various transplanting trajectories on the transplanting plane. Moreover, a transplanting trajectory controller is then designed for the proposed transplanting robot based on a linear model prediction algorithm. To improve the control performance, two control system optimization schemes are proposed: the influence of prediction time length on the accuracy of transplanting trajectory is discussed and the optimal prediction time length value is obtained, and a reference trajectory segmenting control was proposed to improve the real time of sweet potato transplanting. The proposed sweet potato transplanting robot is validated experimentally through field testing. The minimum qualified rate of potato seedling erection angle was 94.7%, and the minimum qualified rate of planting depth was 94.8%. The test proved that the proposed transplanting scheme can realize various transplanting methods of sweet potato with better performance, which satisfies the practical production requirements for mechanical planting of sweet potatoes.