Mokh. Sholihul Hadi

Iwai LaboratoryDept. of Electronics and Applied Physics

Interdisciplinary Graduate School of Science and EngineeringTokyo Institute of Technology

Brief IntroductionThe design of a swallowable (11mm diameter by 25mm long), 12-legged endoscopic capsule for locomotion in the lower gastro intestinal tract (large bowel), which is expected to be useful for bothdistending deflated colon tissue and also for navigating the sharp corners of the splenic flexure found in the colon.

Side angle view of the 12-legged capsule.

Front view of the capsule showing a 32 mm diameter circle

DESIGN OVERVIEW

Side view of the capsule showing motor, gears, lead screw, leg holder,

leg and pins. The arrows show the direction of translation of the

nut and the rotational movement imparts to the leg-holder.

Side view of the slot-follower mechanism

showing all its design parameters

The values AD, OD, OC and ξi are related by the law of cosines:

KINEMATIC ANALYSIS

a) In the closed position (dark line) the leg is completely inside the body (indicated by the body border line). b) In this case in the “closed” position the leg remains outside the body.

A Free body diagram of the mechanism

showing forces and torques.

The summation of these 6 reaction forces on the nut:

reaction force at the nut:

The torque which must be applied to the lead screw to overcome W:

Considering the schematic shown inThis Figure , we can Write:

where,

Line schematic of slot-follower mechanism used for calculating the position where the leg tip reaches maximum distance from the capsule wall.

Differentiating the above equation

the maximum value of the distance between the leg tip and the horizontal axis:

the corresponding position of the nut along the longitudinal axis:

MAXIMUM LEG LEVER ARMS

The Matlab plot showing the permissible AD and ODicombinations, providing a design tool for both leg opening angles and leg

placement positions on the outside of the capsule body

Software Simulation