## 2 Design of the Robotic Catheter System
### Design of the Slave Robotic Device  
As shown in Figure 3a,b, the slave-side robotic device comprises a 2-DOF mechanism geared by stepper motors and a linear actuator. The slave platform implements the actual navigation of the endovascular tool based on input commands received from the master unit.  
For this custom setup, the slave platform utilizes a motorized linear actuator (EAS4 RXE015, Oriental motor, Tokyo, Japan) with a width and height of 58.4 mm \(\times\) 60 mm, a stroke length of 150 mm (accuracy: \(\pm\)0.02 mm), and a resolution of 5000 CPR, as shown in Figure 3a. The actuator employs a ball screw mechanism for its axial drive and is powered by a DC-input stepper motor (AZM24 AK, Oriental motor, Tokyo, Japan), resolution: 1000 CPR, a motor driver (SR series, MOONS', Shanghai, China), and a linear actuator driver (AZD-KD, Oriental motor, Tokyo, Japan), as shown in Figure 3b. In addition, two limit sensors placed 15 mm from both ends of the linear actuator prevent the sliding plate from going beyond the terminal ends of the axial stage. Thus, one-to-one position mapping exists between the master-slave devices, with an active stroke length of 120 mm. The sliding plate houses the proximal force sensor, slip ring, and clamping mechanism. A rotary stepper motor attached to the sliding plate drives the belt and pulley system for rotational movement of the endovascular tool as controlled by the master.  
In addition, as shown in Figure 3b, a miniature linear stepper motor (8k2105, SAMSR motor, Shenzhen Melike Technology Co., Ltd., Shenzhen, China) positioned above the clamping device turns a roller pair, controlling the opening and closing of the clamp via a lateral shift of the clamping controller at the master side. When opened, an operator manually steers the guidewire or catheter through the clamp, the guide sheath, and the grasping device to position the flexible tool at the entrance of a peripheral access port,  
Figure 3: The design and assembling of the slave robot platform. (**a**) The exterior components of the slave platform, and (**b**) the clamping mechanism and interior components of the slave robotic device.  
from where the master-slave device operates the endovascular tool for intravascular the catheterization procedure. The clamp achieves a fixed grasp of the endovascular tool during axial and rotary motion when held in a locked position via four smaller roller shafts, as shown in Figure 3b. The clamping force between the device and the tool, as measured by the proximal sensor (KD24s, ME-Messsysteme GmbH, Hennigsdorf, Germany) with a resolution of 0.002 N and a range of 2 N, is fed back to the operator during procedures. Input-to-output motion and imaging feedback during procedures could aid the development of state-based navigation in RCSs using learning-based models [10; 37].  
Furthermore, as shown in Figure 3, the distally positioned stepper motor facilitates adjustment of the guide sheath angle to optimize the tool's navigation during catheterization procedures. A DC 24V 10,000-mAh rechargeable lithium-ion battery powers the slave device for a mean of 270 min, while a Raspberry PI 4 (Raspberry Pi Foundation, South Cambridgeshire, UK) single-board computer with 8 GB RAM is used for data processing and transfer between master and slave devices.