Continuum robots are widely used in the medical scenarios due to their dexterity and flexibility. However, precise end-to-end control of continuum robots remains challenging, limited by the kinematic or kinetostatic accuracy and no enough space for additional sensors configurations. This paper proposes a precise position control method for fiber-driven continuum robots using the reconstructed shape based on distributed force sensing from the same fibers, where the optical fibers serve as both robot actuation and force sensing simultaneously without requiring additional sensors. First, we use single-core optical fibers (SCFs) as the actuation cables of the continuum robot, and each fiber has multiple fiber Bragg grating (FBG) sensors inscribed on it to sense distributed force along the entire cables. Then, the forward kinetostatics model of the fiber-driven continuum robot is established using the known distributed forces as the inputs. Notably, the nonlinear friction between the cables and actuation channels does not require an additional estimation model. Benefiting from this, the shape can be accurately reconstructed after the stiffness calibration of the continuum robot. Finally, a position controller based on real-time feedback from shape is developed to achieve the tip position control of the continuum robot. Experimental results demonstrate that the proposed forward kinetostatics model can achieve the shape reconstruction with the errors of 0.45 mm and 0.57 mm in planar bending and spatial bending states, respectively. By comparison to the traditional constant curvature kinematics-based control method, the proposed methods can achieve the mean absolute error of 0.37 and 0.6 mm in two distinct path tracking tests. The proposed method using distributed forces sensing enables a real-time accurate position feedback control combined with kinetostatic model, instead of modelling the nonlinear friction or adding additional external sensors.

Deformation of flexible robots can be practically assessed using extension/compression, shear, curvature, and torsion. Sensing based on one or more of the above characteristics enables closed-loop control for delicate tasks that require precision and dexterity. Due to the increasing popularity of flexible robotics in recent years, significant research effort has been directed to this burgeoning field. Although numerous studies have addressed soft sensing technologies, their successful integration into flexible robotic systems remains limited. This article provides a comprehensive review of sensing methods, from multidimensional deformation to the underlying principles of deriving hard-to-measure deformation from surrogate parameters. It focuses on sensing modalities such as strain measurement via piezoelectric, capacitive, resistive, and optical techniques. The applications of deformation sensing in industrial and service robotics are described. Future challenges and potential research issues including resolution, conformability, multifunctionality, crosstalk, and miniaturization are discussed. The need for a synergistic approach across disciplines is highlighted, emphasizing the integration of new materials, microstructures, advanced manufacturing technologies, and state-of-the-art signal processing techniques.

Traditional interaction perception of parallel robots relies on a six-dimensional force sensor for contact sensing at their distal end. However, the sensor body occupies the space of moving platform and also increases the load on the robot actuations. To enable both minimization and embodied intelligence, this paper proposes an external interaction estimation method with embodied mechanical intelligence by embedding two single-axis force sensors in each leg of 6-PSS parallel robot. The method uses a backward propagation neural network optimized by sparrow search algorithm, and it can simultaneously estimate the external force and its position using information from multiple single-axis force sensors and the encoder of driving motor. The experimental platform is established to collect the data and train the network. The result shows that the force estimation mean error is 2.4% and the position estimation error is 2.9%. A demonstration with a virtual display interface showing the reconstructed parallel robot pose, and the interaction force and its pose using the proposed estimation method, indicates the effectiveness of the proposed interaction method with embodied mechanical intelligence for 6-PSS parallel robot

Cable-driven continuum robots are widely used for endoluminal intervention because of their dexterity and shape conforming steerability. However, body contact between the continuum robot and its surrounding anatomy is unavoidable, which imposes a potential safety risk, including vessel wall damage or even perforation. This paper presents an approach for body contact estimation of continuum robots with tension-profile sensing of actuation fibers. First, tension-sensing optical fibers with multiple inscribed fiber Bragg grating (FBG) sensors are used for both actuation and in-situ sensing of the continuum robot. Second, a beam theory-based mechanical model considering segmental differences, multiple fiber interactions and external force interactions is established, followed by robust estimation of contact positions and forces. Finally, detailed simulations are conducted to validate the accuracy and effectiveness of the proposed method. Experiments on a notched continuum robot are carried out, and the results show that the proposed approach can effectively recover in-situ segmental actuation forces without the need of explicit modeling of the friction between the fibers and guiding channels. The method enables the estimation of the number of contact points, as well as contact positions and contact forces along the body of the continuum robot.

Tip force sensing for cable-driven continuum robots are vital to provide the force information for safe and reliable human-robot interaction. However, traditional triaxial force sensors usually have a complicated structure occupying its inner lumen, without enough space for additional instrumental tools. To solve this, this paper proposes a fixed and sliding fiber Bragg grating (FBG) sensors-based triaxial force sensing method for cable-driven continuum robots. The fixed FBG sensors are attached to the circumferential surface of continuum robot at the tip and base, and the sliding optical fibers with FBG sensors are located in the actuation channels as the sensing integrated pulling cables. This configuration guarantees a compact structure and large inner lumen. Two five-degreed-of-freedom (5-DOF) electromagnetic (EM) and a 6-DOF EM sensors are assembled to the tip and the base of the robot respectively, which can obtain the pose of the tip with respect to the base. The tip force in three directions can be decoupled using the information of the Bragg wavelength changes and EM sensors. Results show that the mean errors of force sensing along x-direction, y-direction, and z-direction are 4.1%, 4.7%, and 9.8%, respectively. The proposed sensing method does not rely on the elasticity of continuum robot, enabling its wide applicability for other cable-driven pseudo-continuum robots.

Percutaneous coronary intervention (PCI) involves the delivery of a flexible submillimeter guidewire and existing x- ray based approaches impose significant ironing radiation. The use of magnetic resonance imaging (MRI) for intraoperative guidance has the advantages of not only being safe but also having high positioning accuracy and excellent tissue contrast. This paper develops a pneumatically driven MR-conditional delivery mechanism for the ease of manipulation of the guidewire in vivo. It incorporates newly developed rotary pneumatic step motors and a pneumatic slip ring for actuation and decoupling of translational and rotational motions. An effective clamping mechanism for the locking and releasing of the guidewire is also incorporated. The proposed pneumatic slip ring mechanism decouples six gas lines, where four are used to supply a pneumatic step motor for translational motion and two for the clamping mechanism. High friction sil sleeve is used to hold the guidewire firmly. The rotary pneumatic motor has excellent sealing and stability, providing an output torque of 15.75 Nm/MPa. Experiments show that the average error of translational motion is 0.37 mm. Real-time MRI-guided endovascular intervention is performed in a vascular phantom with pulsatile flows to validate its potential clinical use. The imaging artifact test under MRI shows no noticeable distortion and the loss of Signal-to-Noise Ratio (SNR) is less than 2%.

MRI-guided robotic systems are emerging platforms for minimally invasive intervention because of high positioning accuracy and excellent tissue contrast. MR safe encoders are critical components for closed-loop robotic control. This paper develops an MR safe absolute rotary encoder based on eccentric sheave and FBG sensors. The eccentric sheave transforms the rotational motion of the shaft to the bending deflection of the beam on which FBG sensors are integrated. A model is built by establishing the relationship of the kinematics of the sheave, the mechanical properties of the beam with unknown length, and the strain model of two Fiber Bragg Grating (FBG) sensors. A Pseudo-Rigid Body (PRB) 3R model is used to solve a set of constrained equations for accurate rotary encoding. A prototype is built to calibrate the parameters and validate the accuracy of the encoder and its MR compatibility. Results show that the maximum angular error is 1.6°, and the RMS error is 0.46°. MRI shows that no noticeable artifacts are observed, and the Signal to Noise Ratio (SNR) is not affected. The results demonstrate the potential of the proposed method for it to be integrated with MR safe robots with easy fabrication, compact structures, and continuous measurement.

Electrospinning has exhibited excellent benefits to treat the trauma for tissue engineering due to its produced micro/nano fibrous structure. It can effectively adhere to the tissue surface for long-term continuous therapy. This paper develops a robotic electrospinning platform for endoluminal therapy. The platform consists of a continuum manipulator, the electrospinning device, and the actuation unit. The continuum manipulator has two bending sections to facilitate the steering of the tip needle for a controllable spinning direction. Non-circular joint profile is carefully designed to enable a constant length of the centreline of a continuum manipulator for stable fluid transmission inside it. Experiments are performed on a bronchus phantom, and the steering ability and bending limitation in each direction are also investigated. The endoluminal electrospinning is also fulfilled by a trajectory following and points targeting experiments. The effective adhesive area of the produced fibre is also illustrated. The proposed robotic electrospinning shows its feasibility to precisely spread more therapeutic drug to construct fibrous structure for potential endoluminal treatments.

Accurate force sensing is important for endoluminal intervention in terms of both safety and lesion targeting. This paper develops an FBG-based force sensor for robotic bronchoscopy by configuring three FBG sensors at the lateral side of a conical substrate. It allows a large and eccentric inner lumen for the interventional instrument, enabling a flexible imaging probe inside to perform optical biopsy. The force sensor is embodied with a laser-profiled continuum robot and thermo drift is fully compensated by three temperature sensors integrated on the circumference surface of the sensor substrate. Different decoupling approaches are investigated, and nonlinear decoupling is adopted based on the cross-validation SVM and a Gaussian kernel function, achieving an accuracy of 10.58 mN, 14.57 mN and 26.32 mN along X, Y and Z axis, respectively. The tissue test is also investigated to further demonstrate the feasibility of the developed triaxial force sensor.

Lesions of the lateral skull base in the petrous apex present unique surgical challenges because of the proximity of critical structures, including the inner ear, carotid artery, jugular bulb, facial nerve, lower cranial nerves, dura and brain. Currently, there are few appropriate surgical devices that can reach and remove these lesions, each with their own disadvantages. Here we investigate the feasibility of a dexterous continuum manipulator (DCM) capable of C-& S-shaped bends enabling dissection with remote center of motion (RCM) deep to the intact inner ear. A dedicated borescope channel provides the necessary visualization, while a flexible ring curette pre-shaped with a nitinol strip is designed to work through the instrument lumen for curettage of a cystic lesion. The kinematics of the DCM with the ring curette subject to an RCM constraint are investigated to explore the boundaries of a typical cyst cavity. Experiments in the planar phantom are carried out to validate feasibility, and results show that the proposed solution is practicable, accomplishing 80% and 83% removal of cysts for two kinds of boundaries.

S shape dexterous continuum manipulators (DCMs) are preferred in minimally invasive surgeries for better steerability towards a target and obstacles avoidance capability. Current ways of realizing S shapes need to combine multi-bending segments which need to control the different segment separately. We propose a cross-helical tendons actuated DCM that can realize S shapes just using one segment. With two pairs of cross-helical tendons, it can realize omin-directional S shapes, where two types of planar S shapes are investigated in this paper. A prototype with 8mm diameter and 80mm length is built and the kinematics characteristics are investigated. The results show it can well realize the desired S shapes. The tip directional capability and obstacles avoidance capability are compared with C shape DCM.