The slave robot provides three fundamental degrees of freedom: guidewire axial feed, catheter axial feed, and continuous catheter rotation. Servo motors and timing belt transmission are adopted to achieve compact layout suitable for limited space in catheter laboratories [6]. Key mechanical specifications: Maximum travel: 180 mm; Adjustable feed speed: 0 - 15 mm/s (0 - 3 mm/s fine mode for stent deployment); Rotation range: 0˚ - 360˚ continuous rotation; Repetitive positioning accuracy ≤ 0.1 mm.

A disposable sterile cassette mechanism is designed for rapid assembly before surgery to avoid cross-contamination. Elastic roller clamping ensures stable fixation without scratching the outer surface of clinical catheters.

The master manipulator adopts impedance-type haptic handles. Vascular contact force detected on the slave side is mapped to the operator’s hand in real time. Resistance feedback is generated when the catheter touches vascular walls or stenotic lesions, restoring natural operation sensation similar to manual PCI [7].

A miniature high-precision load cell is installed along the catheter access path. Measuring range: 0 - 5 N, resolution: 0.01 N. According to clinical PCI experience, safe contact force between catheter and coronary vessel is recommended below 0.8 N; forces exceeding 1.2 N significantly increase risks of intimal injury. Two threshold strategies are implemented: warning threshold = 0.8 N, limiting threshold = 1.2 N. Once the limiting threshold is reached, the robot automatically reduces feed speed; sustained overload triggers temporary stop of propulsion [8].

The underlying motion controller is based on STM32 microcontrollers, and the upper computer runs on an industrial PC [9]. Human–machine interface is developed based on Qt, supporting motion parameter configuration, real-time force curve display, DICOM angiogram loading, lesion marking and surgical data recording. The software framework consists of servo driving layer, communication layer, control algorithm layer and visualization interaction layer.

Define the master workspace coordinate Xₘ and slave actuator coordinate Xₛ. A linear scaling mapping is established as the relational expression: Xₛ = k ∙ Xₘ where k represents the scaling factor adjustable by operators [10]. A smaller scaling factor is adopted during stent positioning to realize precise micro-manipulation.

The whole stent delivery workflow is divided into three stages with automatic parameter switching:

1) Vascular access stage: high allowable speed for rapid catheter advancement;

2) Lesion approaching stage: velocity reduction and force warning activation;

3) Stent positioning and deployment stage: minimum speed mode, increased haptic gain and restricted large-amplitude rotation to guarantee accurate alignment.

The test platform includes: silicone phantom mimicking coronary artery branches with 70% and 90% simulated stenosis; circulating pump simulating hemodynamic pressure; commercial guidewires, balloon catheters and drug-eluting stents; laser displacement sensor, multi-channel force acquisition system and the proposed robotic prototype [11].

Three groups of experiments are designed: positioning accuracy test, force tracking & safety protection test, and complete simulated PCI workflow test [12]. Each test is repeated 2 times for statistical averaging.

4.3.1. Positioning Accuracy

Target displacements of 5 mm, 10 mm and 20 mm are set. The measured average axial positioning error is 0.32 mm with maximum error 0.57˚. The average rotational error is 0.31˚, maximum 0.45˚ [13]. The accuracy satisfies clinical requirements (positioning error < 1 mm for stent implantation).

4.3.2. Force Safety Test

Continuous automatic propulsion is set to simulate catheter collision with stenotic lesions. The system triggers warning at 0.8 N. When contact force reaches 1.2 N, propulsion speed decreases rapidly and eventually stops. The overload protection function effectively limits excessive thrust [14].

4.3.3. Simulated Stent Implantation

Complete procedures including guidewire crossing, predilation, stent delivery and deployment are implemented on the phantom [15]. Operators can distinguish normal vascular segments and stenotic regions via haptic cues. Compared with manual manipulation, the robotic system suppresses hand tremor and improves repeatability of stent deployment position [2].

All experiments are conducted on static silicone phantoms. The mechanical properties differ from in-vivo pulsating coronary arteries. Further animal tests under physiological blood flow and cardiac motion are required to validate system robustness [16].

1) Remote operation enables physicians to work outside fluoroscopy rooms, eliminating occupational radiation hazards;

2) Closed-loop proximal force sensing and haptic feedback solve the missing tactile information problem of mainstream commercial robots;

3) Segmented intelligent control strategy is specially optimized for stent deployment procedures;

4) Modular mechanical design facilitates disinfection and compatibility with existing catheter room facilities.

This system belongs to an extracorporeal catheter-driving robot without onboard distal actuation [17]. Active bending inside vessels cannot be realized. For extremely tortuous and heavily calcified lesions, operation still relies on surgeon experience. At present, only 2D angiography is used. Future work will integrate IVUS and OCT multimodal imaging registration [18]. The platform remains human-in-the-loop teleoperation; fully autonomous stent implantation requires further exploration [19].

1) Multimodal registration of angiography, IVUS and OCT to realize automatic lesion measurement and stent size matching;

2) Introduce deep learning for preoperative path planning to achieve semi-autonomous navigation;

3) Develop integrated soft continuum robotic catheters with distal steering capability;

4) Combine intelligent sensing stents to realize “robotic precise implantation + long-term postoperative vascular monitoring”.