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Design and Modeling of a Single-Port Three-Arm Robotic Tool for Minimally Invasive Neurosurgery
Nazia H. Dana, Harith S. Gallage, Ismail A. Auta, Dhanvi Yuvaraj, Ronghuai Qi
TL;DR
Single-incision neurosurgery calls for compact, dexterous tools, while existing tool designs face constraints on miniaturization and maneuverability. This paper designs a 12-DoF, three-arm steerable tool, derives its kinematic model, and validates it experimentally. The model fits individual joint motion closely, while combined motion shows a notable Y-axis deviation.
Problem
Rigid surgical tools limit distal dexterity, triangulation, and access to the full workspace, and single-incision access constrains tool miniaturization and maneuverability.
Source: §I · pp. 1–2Method
The authors design a 12-DoF single-port tool with three steerable minor cannulas and derive and experimentally validate its kinematic model.
Source: §I · p. 2Results
RMSE < 1.5 mm and MAE < 1 mm for separate joint motions; combined actuation errors along X and Z are both < 1.5 mm, while the Y-axis shows notable deviation.
Source: §V · p. 6Takeaways & Limitations
The design places three minor cannulas within a 7.14 mm OD major cannula and achieves full ±360° rotation of the steerable minor cannula.
Source: §V · p. 6Combined actuation exhibits a notable deviation from the model along the Y-axis.
Source: §V · p. 6
Abstract
from arXiv · showhide
Surgical robots require highly dexterous and compact robotic systems capable of operating effectively within confined anatomical spaces. However, due to limited access provided by a single incision, the miniaturization and maneuverability of these robots still need to be improved. In this paper, we propose the design and modeling of a single-port three-arm robotic tool containing one major cannula (7.14 mm outer diameter (OD)) and three steerable minor cannulas (1.93 mm OD). By integrating the proposed 12 degrees-of-freedom (DoFs) steerable robotic tool with a 7-DoF robotic arm, this robotic system can potentially achieve multi-arm manipulation capability. We present the design of the steerable robotic tool consisting of tendon-driven joints controlled by a compact actuation system, derive the kinematic model, and validate both the static and kinematic models through experiments. The performance is evaluated with the root mean square error (RMSE) and mean absolute error (MAE) computed between the experimental data and the kinematic model.
I. INTRODUCTION
Single-port neurosurgical systems need compact, dexterous tools for coordinated manipulation in constrained spaces. This study introduces a three-arm steerable tool and contributes its design, actuation architecture, and experimentally validated kinematic model.
I. INTRODUCTION
- The system is designed for multi-instrument manipulation within a constrained workspace while retaining a compact single-port architecture.Single-port platforms are used across surgical procedures, and multi-channel systems deploy multiple instruments through one incision.Source: §I · p. 1
- Rigid tools limit distal dexterity, triangulation, and workspace access, while many platforms still deploy a single channel and limit coordinated multi-instrument manipulation.Neurosurgical applications impose especially strict diameter and workspace constraints in confined intracranial environments.Source: §I · p. 1
- The proposed tool places three 1.93 mm OD steerable minor cannulas in a 7.14 mm OD major cannula, with claimed larger workspace and reduced inter-joint coupling than current approaches.The paper builds on prior single-port dual-arm work.Source: §I · p. 2
- The 12-DoF tool combines prismatic, rotational, proximal-bending, and distal-bending joints.The paper also identifies minimizing inter-joint coupling and improving independent joint control as goals relative to earlier designs.Source: §I · pp. 1–2
- The study contributes a modular, compact actuation architecture for three minor-cannula joints and derives and experimentally validates the system's kinematic model.The paper identifies these as contributions of the work.Source: §I · p. 2
II. SYSTEM DESIGN
The system places three steerable minor cannulas inside one major cannula, using tendon-driven proximal and distal bending joints. Its design also provides linear insertion and addresses tendon slack in rotational actuation.
II. SYSTEM DESIGN
- Each of the three minor cannulas sits inside the major cannula and has independently actuated proximal and distal bending joints.The cannulas are arranged as shown in Fig. 2(a), with the two bending joints shown in Fig. 3.Source: §II · p. 2, Figure 3 · p. 2
- Laser-machined notches create preferential bending: the proximal unidirectional asymmetric notch pattern bends one way, while the distal bidirectional pattern bends both ways in the same plane.Two cannulas have eight notches per bending section; the third has 10 proximal and 12 distal notches.Source: §II · p. 2
- The prismatic joint provides 40 mm of linear travel, allowing each minor cannula to advance beyond or retract into the major cannula.Source: §II · p. 2
- To address tendon slack during rotational actuation, the design guides the tendon through a grooved sleeve and uses a redesigned spool with separate tendon slots.The authors report that these changes reduce slack and improve rotational-motion precision and accuracy.Source: §II · pp. 2–3
- The compact actuation system integrates 12 joint actuators, and each minor-cannula module includes an unused slot for a possible tendon-driven end-effector actuator.A 7-DoF robotic arm and wireless joystick interface are described as potential additions for teleoperated procedures.Source: §II · p. 3
III. KINEMATIC MODELING
Each minor cannula’s forward kinematics models its insertion, axial rotation, and two bending sections using a POE chain. The modeled three-cannula workspaces partially overlap, forming a common region for coordinated manipulation.
III. KINEMATIC MODELING
- The POE model explicitly includes prismatic insertion, which contributes to the minor cannula’s overall forward kinematics.The modeled joint variables include insertion Lt, rotation θr, and proximal and distal angles θp and θd.Source: Figure 5 · p. 3, §III · p. 3
- The base of each minor cannula is radially offset by w0, and its angular position around the major cannula is ϕj.The model uses this arm-specific rotation and translation to locate each minor cannula relative to the major cannula.Source: §III · p. 3
- Each minor cannula’s forward kinematics includes one insertion joint, one axial rotational joint, and two bending sections modeled as revolute–prismatic–revolute mechanisms.The complete chain has eight joints and uses eight twists in the POE formulation.Source: §III · p. 3
- The remaining joint twists are formed from the appropriate axis direction and a point on that axis, using v = −ω × q for rotational joints.The twist sequence assigns the first twist to insertion, the second to axial rotation, and three twists each to the proximal and distal RPR sections.Source: §III · p. 4
- The modeled workspace spans approximately 34.77 mm, 35.47 mm, and 53.99 mm along X, Y, and Z, with partially overlapping cannula workspaces.The inputs were 40 mm insertion, 30° proximal bending, 75° distal bending, and 360° axial rotation; the third cannula has a slightly larger lateral workspace.Source: §III · p. 4
IV. RESULTS & DISCUSSION
The authors conducted independent joint tests and combined-actuation tests to validate the static and kinematic models. A six-degree-of-freedom electromagnetic tracking system measured cannula-tip motion.
IV. RESULTS & DISCUSSION
- Two experiments tested individual joint static and kinematic models and simultaneous actuation of all joints to validate a single arm’s kinematic model.The test cannula had eight proximal and eight distal notches.Source: §IV · p. 4
- A six-DoF electromagnetic tracking system used one fixed-reference sensor and one sensor to track cannula-tip motion.The setup is shown in Fig. 6.Source: §IV · p. 4
- The joint kinematic models were evaluated using RMSE and MAE, with figures presenting experimental and model comparisons for joint behavior and tip displacement.Fig. 8 shows joint-angle deflections; Figs. 9 and 10 show tip displacement and trajectories, respectively.Source: §IV · p. 5, Figure 8 · p. 5
A. Verification of Joint Static Model
The joint static-model experiments cover proximal and distal bending, full-range rotation, and prismatic translation. The authors report that the models capture angular and translational behavior within acceptable ranges for the intended application.
A. Verification of Joint Static Model
- Proximal and distal bending tests targeted 30° and 60°, respectively, and measurements closely matched model output.The evaluated proximal actuation range extends to 30° from 15° in prior work; the system also supports simultaneous proximal and distal bending.Source: A. Verification of Joint Static Model · p. 5
- The rotational joint completed a 360° sweep and return, extending the prior design’s 180° range; its static model captured the overall experimental trend.The model comparison included a 0.9 mm tendon-slack compensation term.Source: A. Verification of Joint Static Model · p. 5
- The prismatic joint completed a 40 mm upward translation and return, and experimental measurements closely matched the lead-screw-based static model with low errors.The model relates commanded linear displacement to required motor angle using a 0.5 mm lead-screw pitch.Source: A. Verification of Joint Static Model · p. 5
- The static results validate joint models that capture angular and translational behavior, with deviations within acceptable ranges for the intended application.The rotational joint achieves full 360° bidirectional actuation, while the prismatic joint maintains small linear error.Source: A. Verification of Joint Static Model · p. 5
B. Verification of Kinematic Model
The kinematic model was tested with individual and combined joint actuation. It tracked the cannula tip overall, with the largest combined-trajectory deviation along Y.
B. Verification of Kinematic Model
- Independent joint tests evaluated rotational, proximal, and distal joints at 5°, 15°, and 25°, and the prismatic joint at insertion levels of 5 mm, 15 mm, and 25 mm.Across the experiments, RMSE was below 1.5 mm and MAE below 1 mm.Source: B. Verification of Kinematic Model · p. 6
- RMSE was 1.15 mm, 3.15 mm, and 1.29 mm, and MAE was 0.84 mm, 2.19 mm, and 1.05 mm along X, Y, and Z, respectively, during combined actuation.The sequence applied 10 mm translation, 8° proximal bending, 50° distal bending, and 90° axial rotation.Source: B. Verification of Kinematic Model · p. 6, Figure 11 · p. 6
- Overall Cartesian errors remained within a few millimeters, with the largest deviation along Y; the model captured angular and translational behaviors.The authors attribute discrepancies likely to compliance, tendon friction, backlash, and other effects absent from the ideal kinematic formulation.Source: B. Verification of Kinematic Model · p. 6
V. CONCLUSIONS & FUTURE WORK
The conclusion presents a three-arm tool with three 1.93 mm OD minor cannulas integrated within a 7.14 mm OD major cannula. Its full-joint kinematic model was experimentally validated, with a notable Y-axis deviation under combined actuation.
V. CONCLUSIONS & FUTURE WORK
- Three 1.93 mm OD minor cannulas fit within a 7.14 mm OD major cannula, and the steerable minor cannula achieves full ±360° rotation.The paper describes the system as smaller than existing state-of-the-art single-port MIS robots.Source: §V · p. 6
- The complete kinematic framework covers all joints, including prismatic motion, and the three minor cannulas are placed together within the system configuration.The study reports RMSE < 1.5 mm and MAE < 1 mm for individual joints; under combined actuation, X and Z errors are both < 1.5 mm, while Y shows a notable deviation.Source: §V · p. 6
- Future work includes adding a hysteresis model, implementing inverse kinematics, integrating functional end effectors, and mounting the mechanism on a 7-DoF manipulator.The authors identify these as planned developments for multi-arm MIS applications.Source: §V · p. 6