Contact force modeling and variable damping impedance control of apple harvesting robot

In order to realize the compliant grasping of apple harvesting robot and reduce the mechanical damage in the process of grasping, a variable damping impedance control strategy for gripper grasping force tracking is proposed based on the establishment of contact force model in this paper. Firstly, the Burgers model is used to characterize the biological characteristics of apple. Then, according to Hertz contact theory, the contact force model of apple during grasping was established to represent the dynamic relationship between grasping force and deformation. Finally, based on the position impedance control theory and the analysis of the influence of impedance parameters on the control performance, a variable damping impedance controller is designed. The dynamic tracking of the grasping force is realized by adjusting the damping coefficient online to modify the desired position. The simulation and experimental results show that compared with the traditional impedance control, the variable damping impedance control has a smoother tracking effect on the grasping force and its dynamic performance is significantly improved. This method can provide reference for the research of compliant grasping control of apple harvesting robot end-effector.