Abstract
Soft robot has been one significant study in recent decades and soft gripper is one of the popular research directions of soft robot. In a static gripping system, excessive gripping force and large deformation are the main reasons for damage of the object during the gripping process. For achieving low-damage gripping to the object in static gripping system, we proposed a soft-rigid gripper actuated by a linear-extension soft pneumatic actuator in this study. The characteristic of the gripper under a no loading state was measured. When the pressure was >70 kPa, there was an approximately linear relation between the pressure and extension length of the soft actuator. To achieve gripping force and fingertip displacement control of the gripper without sensors integrated on the finger, we presented a non-contact sensing method for gripping state estimation. To analyze the gripping force and fingertip displacement, the relationship between the pressure and extension length of the soft actuator in loading state was compared with the relationship under a no-loading state. The experimental results showed that the relative error between the analytical gripping force and the measured gripping force of the gripper was ≤2.1%. The relative error between analytical fingertip displacement and theoretical fingertip displacement of the gripper was ≤7.4%. Furthermore, the low damage gripping to fragile and soft objects in static and dynamic gripping tests showed good performance of the gripper. Overall, the results indicated the potential application of the gripper in pick-and-place operations.
Highlights
In a static gripping system, fragile and soft objects such as eggs, cakes, strawberries, etc., are often damaged due to excessive gripping force or large deformation
When gripping soft objects such as cakes, strawberries, etc., both the gripping force and the fingertip displacement of the fingertip deep-going into the object surface must be precisely controlled
We proposed a soft-rigid gripper actuated by a linear-extension soft pneumatic actuator used in a static gripping system
Summary
In a static gripping system, fragile and soft objects such as eggs, cakes, strawberries, etc., are often damaged due to excessive gripping force or large deformation. Compared with the black line, the relationship between the pressure and extension length with the gripper gripped the rigid cylindrical objects with diameters of 40, 35, 30, 25, and 20 mm displaced at points R1, R2, R3, R4, and R5, respectively. Compared with the black line, the relationship between the pressure and extension length when the gripper gripped the soft cylindrical objects with diameters of 40, 35, 30, 25, and 20 mm displaced at points S1, S2, S3, S4, and S5, respectively.
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