## 3 Materials and Methods
### Driving Environment  
The driving environment of the semi-automatic implanter is shown in Figure 11. To drive the needle (or gripper) and the rod, two Maxon DCX10L motors are used in Figure 11a, and a motor encoder is connected to each motor for driving them. The volume of the semi-automatic implanter is \(257.9\times 59.8\times 36\) mm and can be gripped with one hand. For the driving experiment, a number of implanting needles were inserted in the NSM. At the transplant, the needle and rod advance into the scalp, and then the HF is transplanted by the retraction of the needle while the rod is fixed; this moment of transplantation is shown in Figure 11b. The HF transplantation ability of the semi-automatic implanter was tested using artificial scalps with a hardness of 10 and 20, as shown in Figure 11c.  
Figure 11: Driving environment for semi-automatic implanter. (**a**) Driving environment, (**b**) state of needle and rod at transplant, and (**c**) transplantation ability test.  
Figure 10: Guide structure for needle transfer.  
The movement of the needle and the rod of the semi-automatic implanter is based on the operating principle of the existing manual implanter, which leaves the HF inside the needle in the scalp. The developed motor control program using the EPOS2 digital positioning controller [27] is designed to set the motor gear ratio (4:1), direction, number of rotations, rotation speed, and acceleration and deceleration of respective motors for each transplant stroke, as shown in Figure 12.  
The motor control program currently supports three motors, but it only uses two for the semi-automatic implanters. It has a selectable gear ratio and can set the rotation speed, acceleration and/or deceleration speed, and delay time. Since the motor encoder signal is 1024/cycle, the speed setting supports a resolution of 1/1024. The motor control program also has a homing mode function when both motors stop working. Its command comprise rotation direction, number of rotations, speed of rotation, acceleration, deceleration, delay time, and gear ratio. In addition, it can store an entirely new command or call up an existing command. Each motor is configured with a USB port interface with a baud rate and timeout of 10\({}^{6}\) and 500 ms, respectively.  
The characteristics of the motor control program are as follows:  
* Initially, the driving motor is homed by the motor control EPOS2 program.
* The transplant speed is adjusted by the setting of the number of rotations, rotation speed, and acceleration and/or deceleration of the needle motor and the rod motor.
* The range of the rotation speed of the driving motor (DCX10L) is 0-32,256 rpm; the rotation speed for each transplant stroke can be changed according to the surgeon's preference.
* Both motors operate at 1350 rpm by default. However, in the case of the rod motor, the rotation speed is 1350 rpm or more in two strokes: the insertion of the rod into the needle when moving forward (the fourth stroke) and the rapid release of the rod out of the needle when moving backward (the sixth stroke).
* The motor-related setting values are entered in the order of movement of the needle and rod described in Section 3.4, but they can be adjusted within the confidence error.  
Table 1 shows the setting value of each motor per transplant stroke. This setting value was based on the operation sequence of the needle and the rod of the semi-automatic implanter shown in Figure 9.  
Figure 12: Proposed motor control program using the EPOS2 digital positioning controller.