# Soft Robotic Gripper with Chambered Fingers for Performing In-Hand Manipulation
## 4 Experiment
### Experiment on a Single Actuator  
We conducted experiments by inflating the middle chamber and side chamber just as we did in the simulation. We also applied pressure simultaneously to both chambers, as shown in Figure 7.  
Figure 7: Top and side view of inflations, which include: (**a**) Middle chamber’s inflation, (**b**) side chamber’s inflation, and (**c**) dual-chamber inflation.  
In the experiments, we mostly focused on the bending angle, which is the angle between the center of a fingertip and its initial position during inflation (see Figure 8b). As in the first experiment, we applied pressure ranging from 25 kPa to 95 kPa. The deformation of the proposed finger started at 28 kPa and bending angle was resulted in 80\({}^{\circ}\) at 85 kPa. We compared the experimental results from the middle chamber's inflation with the results from FEM and noted the difference, which we had assumed would occur, as can be seen in Figure 8c. The difference can be caused by small air losses by components on the pneumatic control board. It can also depend on how we applied pressure to the actuator. In the simulation, all configurations were accurately set, and the software analyzed the motion of finger based on the defined calculation; therefore, the deformation result was stable.  
Our next experiment was conducted on the side chamber's inflation. We applied pressures from 25 kPa to 100 kPa and the finger bent fully at 97 kPa. Compared to the previous experiment results, the finger bent between two axes. This experiment result was precisely demonstrated in the 3D curve. As shown in Figure 9a, the O represents the initial position of the fingertip. We combined all of the results from the middle chamber's inflation and side chamber's inflation. From this, we could predict the motion resulting from inflation in both chambers, which means every chamber's inflation will suppress each other's bending motion. To investigate this phenomenon, we conducted the following experiment. We present the last experiment, which was performed by applying the same pressure to both chambers at the same time. Figure 9b illustrates the 3D curve after adding the result of the dual chamber's inflation to previous results. We can easily predict the fingertip position using this combination of experimental results. From Figure 7c, we can see that when we applied the same pressure to the middle chamber and side chamber, the finger bent away from the inflated the side chamber. In other words, as shown in Figure 9b with respect to applying pressure to a side chamber, the finger bends along the positive side of the \(Y\)-axis, but when pressure is applied to dual chambers, including the side chamber that was used before, and the middle chamber, the finger bends along the negative side of the \(Y\)-axis.  
Figure 8: \(Cont\).  
We also observed that when we decrease pressure in the air chamber by a certain amount, the finger will bend along the \(X\)-axis. Following this principle, regarding the ratio of inlet pressure of the middle chamber and side chamber, it resulted in a wide range of workspace as we see in Figure 9. Furthermore, this motion can be used to accomplish the in-hand manipulation. Depending on the object's size, we can use just one side chamber's inflation to rotate the object.  
From the 3D curve, we can conclude the following statements:  
* Inflating the side chamber can be sufficient to produce a small-angle twisting motion.
* The gripper was found to be capable of grasping bigger objects than expected, as seen in Figure 6, because of the size of the grasp.
* Inflating dual chambers allows smaller objects to be rotated with any angle.
* To grasp and twist sequentially, the dual chamber's inflation is performed after the middle chamber's inflation.  
Figure 8: Experiment on single finger: (**a**) Experimental setup; (**b**) bending angle when the middle chamber is inflated; (**c**) plot showing the relationship between bending angle and pressure with middle chamber’s inflation.