Abstract: Based on the principle of Rong-Cha, a novel control method is proposed, which can work effectively within a certain range without precise perception. The working principle of how to use the same control input to achieve different grasping tasks by the Rong-Cha based grasping method is analyzed. Based on this principle, the grasping method can cope with a large class of grasping tasks without knowing the specific parameters of the objects, only the boundary conditions of this large class of objects are needed to know. The applicability of the Rong-Cha based grasping method to underactuated grippers is analyzed, and limitations of underactuated grippers are unveiled. The experiments show that by the Rong-Cha based grasping method and with the unchanged control inputs, the soft gripper can grasp the soft tofu without damage within the width range of 5~45 mm, and can successfully grasp the rigid cuboid within the width range of 5~60 mm. The spring-jointed underactuated gripper can grasp soft tofu within the width range of 20~40 mm without damage, and can successfully grasp the hard cuboid within the width range of 5~60 mm. The results demonstrate the versatility of the Rong-Cha based grasping method and the limitations of the underactuated gripper in grasping soft objects. Finally, it is shown that the soft gripper uses the Rong-Cha based grasping method to successfully grasp objects of different shapes and materials with a simple control strategy in a desktop grasping application. This fully demonstrates that the Rong-Cha based grasping method doesn't rely on the accurate object perception and the corresponding object model, and can simplify the control strategy.