**3.3. Experiment on principle verification**

14 Will-be-set-by-IN-TECH

**Figure 19.** Schematic diagrams of the proposed movement principle of the cylindrical soft robot. Initial state (1), Magnetic particles inside the water balloon are affected by the external magnetic field (2), push the inner side of a balloon, rotate the water balloon to the direction of a magnetic field (3)(4), Magnetic

field disappears and rotational movement stops (5).

The sliding movement is measured using an experimental model (Fig.21). The model is pulled with a wire, and it passed between two sheets that simulated internal organs (SEIWA DENTAL Ltd., Japan; Polyvinyl alcohol, 20 × 10 × 1cm). The sheet imitates the softness of an abdominal wall but not the colonic peristalsis and the organs' shape. The gap between the two sheets is gradually increased. The force required to slide the model without rotation is measured as frictional force *a*, *b*, and the force required to rotate and deform the model without slippage is measured as the force necessary for movement *c* in Eq.(2). The measuring system is shown in Fig.22, it consists of a load cell (KYOWA ELECTRONIC INSTRUMENTS CO., LTD.; LUX-A-1KN), a stage (SIGUMA KOKI CO.,LTD; SGSP 20-30), and a PC. The measured values are shown in Table 1. The values of the magnetic force necessary for movement were determined at intervals from 28 to 33 mm.

Verification experiment of the proposed movement principle were conducted by use of the experimental prototype(Fig.21), simulated internal organs' sheets and magnetic field generator(Fig.5).

16 Will-be-set-by-IN-TECH 440 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

**Figure 22.** Measuring setup of movement condition. The model is pulled with a wire, and it passed between two sheets that simulated internal organs. The gap between the two sheets is gradually increased.


**Table 1.** Measured value of movement condition

Fig.23 shows a graph of the measured magnetic force exerted by magnetic particles inside the water ballon. The magnetic force of 0 - 1.5 N can be applied to the model by the magnetic field generator.

Eq.(3) shows theoretical formulas of the magnetic force *F*, measured values are consistent with theoretical ones.

$$F = m\frac{dH}{dx}\tag{3}$$

$$
\hbar \mathfrak{m} = \chi\_{eff} \text{HV} \tag{4}
$$

*m*: magnetic moment, *H*:magnetic field, *x*: distance from coil, *V*:volume of material, *χeff* : magnetic susceptibility

In the experiment, the model was positioned at this point and placed between the two sheets that simulate internal organs. The gap between the two sheets was 30 mm. The magnetic force of 0.52 N was momentarily applied to the model by the magnetic field generator.

**Figure 23.** Graph of the measured magnetic force exerted by magnetic particles inside the water balloon.
