## 2 7 DOFs VI Robotic System  
### 7 DOFs VI Slave Robot  
In this study, a 7 DOFs VI slave robot system was developed to control the motions of the catheter, guidewire, microcatheter, and micro guide wire. Figure 1a shows the 7 DOFs VI slave robot proposed in this study, which is a modified version of that developed by [PERSON] et al. [20; 21; 22]. [PERSON] et al. developed a 4 and 5 DOFs robotic systems for vascular intervention. The 4 DOFs robotic system controls the guidewire and the catheter, and the 5 DOFs robotic system includes steerable catheter. The unique feature of the 7 DOFs VI slave robot is that it employs a two-way design to minimize the total length of the robotic system. The front part of 7 DOFs VI slave robot is used to drive the guidewire and the catheter, and the longitudinal part is used to control the motion of the micro guidewire and the microcatheter.  
The 7 DOFs VI slave robot employs a telescopic mechanism in the central axis to control the catheter, as shown in Figure 1b. The guidewire moves sideways through the y-connector; this is done to enable the installation of up to four intervention tools on the 7 DOFs VI slave robot at once before conduction of the procedure so that the operator does not need to intervene during the VI procedure. The 7 DOFs VI slave robot can implement catheter rotation/insertion, guidewire rotation/insertion, microcatheter insertion, and micro guide wire rotation/insertion motions, as shown in Figure 1b.  
To use the VI robotic system in a real operating room, it is necessary to consider the installation of the VI robotic system. During the VI procedure, the position of the bed and the C-arm are required to be freely adjustable. Therefore, the proposed VI slave robot was developed in the form of a bed mounting to maintain the robot's position with respect to the patient. In addition, a 5 DOFs robot arm is used to adjust the position of the VI slave robot such that it could approach the patient's treatment area in the right direction. The movement of the 5 DOFs robotic arm is shown in Figure 2a. For user convenience, a motor and a brake were installed at each joint of the 5 DOFs arm. In the case of normal operation, when power is supplied to the 5 DOF robot arm, the brake on the robot arm is released so that the robot arm can be properly positioned. Conversely, in the event of an emergency when the power supply is not stable, the brake on the 5 DOF robot arm is locked to ensure  
Figure 1: 7 DOFs VI slave robot modified from previous research: (**a**) 7 DOFs VI slave robot mechanism; (**b**) 7 DOFs VI motions of the slave robot.  
patient safety. The position of the VI robot was adjusted by operating the handle. The force/torque sensor (ROBOTUS, RFT40) installed on the handle of the 5 DOFs robot arm is employed to position the handle easily using an admittance control algorithm.  
The 7 DOFs VI slave robot thus mounted on the side of the bed with the 5 DOFs robot arm is shown in Figure 2b.  
When the user operates the handle, the measured force and torque \(\underline{f}\) are converted to a position command \(\underline{u}_{arm}\) of the 5 DOFs robot arm through admittance control according to the expression  
\[\underline{u}_{arm}=[A]\underline{f}, \tag{1}\]  
where \([A]\in R^{5\times 5}\) is the admittance gain matrix.