This paper presents a method for comprehensive 6D estimation of tip wrench for generally deflected static elastic rods. Current methods for load estimation are restricted to estimating lateral (point or distributed) forces for (quasi-)planar deformation; estimation of tangential force and moment, i.e., the full 6D wrench, remains largely unreliable due to the ill-posed nature of the problem. To address this challenge, this paper begins by proposing a high-fidelity static rod model that leverages Koopman Operator theory. Building on this model and utilizing shape feedback, a computationally efficient three-step wrench estimator is proposed: (i) a Koopman-UKF local moment observer, (ii) a static equilibrium solver, and (iii) a rod model propagator. Then, a 2D wrench screw system, identified as the insensible wrench in the initial estimation, elucidates error sources and informs strategies to enhance accuracy by incorporating additional feedback, such as the rod tip material frame and base axial force. Ultimately, the framework delivers accurate 6D tip wrench estimation with quantified uncertainty. Simulation and experimental evaluations validate its effectiveness, demonstrating mean errors of$53.14\,$mN (1.94%) and$2.65\,$mNm (7.18%) for a$159\,$mm-long Nitinol tube undergoing complex out-of-plane deformations, outperforming three replicated state-of-the-art methods. Additionally, its applicability to more complex continuum robots is demonstrated through load estimation on a Parallel Continuum Robot.

Tumors affecting abdominal organs rank among the deadliest malignancies. In this context, Magnetic Resonance Imaging (MRI) serves as an effective diagnostic tool with a strong potential to support image-guided minimally invasive interventions for treating these tumours, offering an ionizing-radiation-free medical modality. MRI provides exceptional soft tissue contrast and multi-angle imaging, enabling accurate intraoperative localisation of target tumours within these vital organs. Nevertheless, MRI-guided minimally invasive interventions still encounter significant challenges due to the strong magnetic field environment and the narrow and deep bore of MRI machines. This paper proposes a novel MR safe 5-degrees-of-freedom (DoFs) parallel table-mounted double-arch needle insertion robot with a scissor-folding mechanism (SFM) for abdominal interventions. The proposed robot is designed to fit a standard 70-cm MRI bore. Initial evaluation experiments indicate mean errors of 3.14 mm for the proposed robotic arch and 2.23 mm for the full needle insertion robot, respectively. Additionally, preliminary testing of the system in an MRI environment resulted in unaltered MRI imaging output, with negligible artefacts associated with the presence of the robot within the bore.

Minimally invasive surgery requires real-time tool tracking to guide the surgeon where depth perception and visual occlusion present navigational challenges. Although vision-based and external sensor-based tracking methods exist, fibre-optic sensing can overcome their limitations as they can be integrated directly into the device, are biocompatible, small, robust and geometrically versatile. In this paper, we integrate a fibre Bragg grating-based shape sensor into a soft robotic device. The soft robot is the pneumatically attachable flexible (PAF) rail designed to act as a soft interface between manipulation tools and intra-operative imaging devices. We demonstrate that the shape sensing fibre can detect the location of the tools paired with the PAF rail, by exploiting the change in curvature sensed by the fibre when a strain is applied to it. We then validate this with a series of grasping tasks and continuous US swipes, using the system to detect in real-time the location of the tools interacting with the PAF rail. The overall location-sensing accuracy of the system is 64.6%, with a margin of error between predicted location and actual location of 3.75 mm.

Endoscopic surgery is an increasingly popular alternative to laparoscopic techniques for many conditions, as the operation site can be reached without skin wounds. In many tasks, sufficient force generation is desired. As endoscopes must be highly flexible and slim, however, the force generation and sensing capabilities associated with these tools is limited due their compliance, significantly hindering the adoption rate of endoscopic surgeries. This paper proposes a technique, termed `environmental scaffolding', to stabilize an actuated, flexible segment in the intestine such that larger forces can be applied. Through the measurement of actuation forces, a method for intrinsically sensing multiple contact forces when in this configuration is presented. Experimental results show that with the environmental scaffolding technique, the tip force generated can be increased by over 50% on average compared to using the device in a purely cantilevered configuration, and the tip force estimation is accurate to within 2.97%.

Measuring forces and torques applied to tools of unconventional shapes can be challenging due to difficulties in connecting commercially available force/torque sensors. We propose an innovative, customizable six-axis force/torque sensor which can be clamped around a tool or end-effector to minimize the proximity between tool tip and sensor structure. The sensor is fabricated using 3d printing technology and consists of two pieces which together form an 8-legged Stewart platform. Each leg is designed as a cantilever beam to allow for a measurable displacement under an external load. The displacements of the legs are measured with 8 light intensity-based optoelectronic sensors, which exhibit high sensitivities and low noise levels without the need for external amplification circuitry. A customized printed circuit board and peripheral hardware are proposed to allow for efficient analog-to-digital conversion of the force/torque measurement. A calibration process is proposed which makes use ofa commercial ATI Mini40 sensor and custom hardware to allow for fast calibration routines. Finally, the calibrated sensor design is compared to the ATI Mini40 sensor by measuring sequences of forces and torques, and the maximum errors of force/torque components (Fx, Fy, Fz, Mx, My, Mz) are 16.3%, 20.0%, 27.5%, 20.5%, 21.6%, 14.9% respectively.

Knowledge of externally applied forces is crucial for compliant robotic manipulators in minimally-invasive and endoluminal robotic surgery for both patient safety and controllability of the device. We developed a novel continuum manipulator which comprises hydraulic actuation. In this work we investigate the use of the hydrostatic pressure feedback inside the inflatable actuation chambers to determine the normal and shear forces which are applied to the tip of the robot. For that purpose a nonlinear finite element model is derived and experimentally validated, showing a good approximation between experiment and simulation. The model is then used to derive descriptions for the normal and shear forces applied to the robot tip. The normal force estimation shows good results over the range of experimentally validated tip angles, while the shear force estimation shows good results for small tip deflection angles with an increasing error, with the tip orientation. The algorithm indicates good applicability to force control tasks as the forces are fast to compute.

Medical ultrasound imaging robotics systems often comprise of complex control architectures and hardware integration to enable safe human robot interaction. In this paper, we investigate the applicability of a soft robotic end-effector for ultrasound intervention. A novel, parallel design is derived based on the medical requirements, which addresses common shortcomings in both robotic ultrasound systems and soft robotic devices. Individual actuators are developed and characterized and the performance of the overall platform is evaluated in regards to its stiffness and steerability. It is shown that the platform comprises relatively high longitudinal and transversal stiffness, while still being compliant enough to ensure the safety of the patient. The shear stiffness of the platform is 4.2 times greater than the shear stiffness of an individual actuator. The platform is capable of applying loadings of 10N along its longitudinal axis, which makes it suitable for the given application. Furthermore, the workspace of the platform is suitable to robot-guided ultrasound with a maximum platform rotation range of ±14.8°, while only moving ±7mm in space.

Contact force play is a significant role in success of the cardiac ablation. However, it is still challenging to estimate contact force when a catheter is under large bending and multiple contacts. This paper develops a new multi-section static model of the tendon-driven catheters for both real-time intrinsic force sensing and interaction control. The model allows estimating the catheter shape by the external force at arbitrary location. Also, an algorithm is developed for the contact force estimation using the shape estimation with the catheter end-position tracking and tension feedback. In this study, we validated the contact force and shape estimation using a robotic platform, which steers a catheter consisting of 4 tendons with tension feedback. The shape estimation results show that the model can accurately predict the catheter shape; the position difference between measured and estimated was 2.5mm. The results of the contact force estimation show that 3-dimensional contact forces can be estimated accurately using the proposed method. The magnitude of contact force error was 0.0117N with 350Hz update rate.

This work investigates the applicability of stiffness-based modelling in soft robotics manipulation. The methodology is introduced and applied to model a soft robotics manipulator as single 3d Timoshenko beam element. The model is then utilized to solve the forward kinematics problem for the manipulator. The algorithm is validated comparing the simulated deflection with the deflection of the physical manipulator for two defined pressure sequences. It is shown that the model behaves in a highly similar fashion in comparison to the manipulator. For both trajectories the maximum position error is close to 6 mm while the error in orientation not more than 18°. The methodology as described in this work reveals great applicability to the field of soft robots being limited only by the stiffness matrix assembly for the given system. Implementations of inverse kinematics and the effects of external force applications are effectively integrable in the described theory.