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Single-port multichannel multi-degree-of-freedom robot 397

17.2.7 Surgery procedure

The robotic system can be used in typically NOTES, such as the ESD. As one of the
robot-assisted surgeries, the necessary surgery procedure should be followed.
Before the operation, sufficient preparation for the patient is needed. The robotic system
should be sterilized or covered by sterilized wraps. After that, the endoscopic platform is
inserted into the natural orifice of the patient by surgeons. The manipulator is set as the
initial state so that it can pass through the channels of the endoscopic platform. After the
manipulators are inside the designated location, the surgeon operates the manipulators under
the guidance of the camera. If the surgical tools can be changed during the operation, the
manipulator is reset to the initial state and replace with others. The endoscopic platform
with the manipulators is retrieved after the operation. The postoperative work is conducted
at last.

17.3 Experiment and results

The experiment is conducted to verify the variation of the stiffness of the manipulator
under different conditions. The setup is shown in Fig. 17.5. The arm of the manipulator was
fixed on a platform. The terminal of the arm kept in touch with the force sensor, which was
attached to the motion stage. Two weights were attached to the wires to provide tension for
the bending of the arm, respectively. Three tests were conducted. The weight of 2 N was
attached to wire 1, and the weights of 3, 5, and 7 N were attached to wire 4, respectively.
In each test, the micro head rotated to move the terminal of the arm from 0.5 to 2.5 mm at
a step of 0.5 mm. The force sensor recorded the contact force.

The results indicate the relationship between the displacement and the contact force in
Fig. 17.6. When applying different displacements to the arm, the slopes of the arm that
represent the stiffness of the arm are approximately coincident, which means that the
stiffness is stable under various loads. When wire 4 is undergoing with the tension of 3, 5,
and 7 N, the slopes gradually increase, showing that the stiffness of the arms increases by
tuning the tension of the wires.

17.4 Conclusion and discussion

Robot-assisted MIS provides an effective solution compared with the conventional surgical
procedure in NOTES [18 24]. However, there still exist technical challenges and clinical
issues to be solved [16]. Most of the current robots are composed of structures with
constant stiffness, which are not ideal for NOTES because, during the operation, enough
stiffness of the manipulator is desirable for sufficient accuracy. At the same time, flexibility
is also essential for safety consideration.