**4. Soft Gripper Control Method for Slip Detection and Constant-Pressure Feedback**

During the actual grasping, the gripping force is *fc*, which is the same magnitude as the force *Fc* but in the opposite direction, and the pulling force is the resultant force in the x-axis direction *F.* From Equations (11) and (16), the relationship between the gripping force *fc* of the gripper, the pulling force *F*, and the servo torque *Md* can be obtained, as shown in Figure 10a. Therefore, when the fruit detachment force *Fd* is determined, the driving torque required for fruit detachment can be calculated according to the diameter of the fruit, thereby setting the servo output torque *Md*. Simultaneously, it is possible to conclude that the gripping force *fc* on the fruit surface at this time. To ensure constant pressure acting on the surface of the fruit, *fc* should not be greater than the maximum pressure *Fm* that the pericarp of the fruit can withstand.

**Figure 10.** Model of the soft gripper control method: (**a**) the relationship among *fc*, *F*, and *Md*; (**b**) Relative position detection between fthe ruit and the gripper.

In addition to the fruit damage caused by the excessive gripping force of the fingers, which also includes bruises and scratches caused by the relative sliding between the fruit and the fingers, as shown in Figure 11. Therefore, to avoid the slippage between the fruit and the finger during harvesting, this paper detects the relative position between the fruit and the gripper by integrating a distance sensor to assess the fruit slippage and minimizing the damage caused by fruit slippage during harvesting, as shown in Figure 10b.

**Figure 11.** Damage to the fruit: (**a**) scratches; (**b**) bruises.

Combined with the constant-pressure feedback state, the specific implementation steps of the soft gripper control method for slippage detection are as follows:
