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Tendon routing and anchoring for cableriven single-t surgical manipulators 185

Figure 7.13
Joystick control in the x, y coordinates.

temperature still forced the device to have downtime to cool down the circuit. Second, the
stepper motors occupied a larger space and weight too heavy to achieve a lightweight,
portable device. Stepper motors were replaced with high-torque 360-degree servo motor in
the second prototype to meet the functional requirement, as shown in Fig. 7.14. Servo
motor allowed a precious control of speed using the pulse width modulation (PWM)
control. Additionally, servo motors eliminated the need for the H-bridge circuit, eliminating
the high circuit temperature issue. Furthermore, servo motors feature a high-torque, small
size configuration, making it suitable for a lightweight, portable device.

7.5.3 Prototype testing

As shown in Fig. 7.15, our prototype was successful in meeting our design requirements
and functional goals. It was miniaturized to an overall shaft diameter of 12 mm, while the
individual channels are around 3 mm in diameter. It is to be noted that we are using a low-
cost endoscope for this run as a proof of concept. There are higher resolution endoscopes
available that have a smaller size than the one currently being used. As such, further
miniaturization is possible up to 9 10 mm from our current 12 mm (corresponding to a
25% 30% reduction in size). A 20-cent coin visible in the image shows the scale of