Contact Force Sensor Research Articles

Finger Force and Position Measurement without Obstructing Touch Interaction

In order to analyze tactile sense of touch in manipulating real-world objects, haptic information is required to be captured without obstructing touch interaction. This study designed a system that enables to simultaneously measure finger force and three-dimensional position without preventing tactile sense of touch. The system consists of a contact force sensor which estimates contact force through deformation of finger, and a magnetic sensor to obtain three-dimensional position of the finger.

Automated Multiprobe Microassembly Using Vision Feedback

This paper describes the algorithm development and experimental results of a vision-guided multiprobe microassembly system. The key focus is to develop the capabilities required for the construction of 3-D structures using only planar microfabricated parts. Instead of using grippers, multiple sharp-tipped probes are coordinated to manipulate parts by using vision feedback. This novel probe-based approach offers both stable part grasping and dexterous part manipulation. The light weight of the part and relatively slow motion means that only kinematics-based control is required. However, probe motions need to be carefully coordinated to ensure reliable and repeatable part grasping and manipulation. Machine vision with multiple cameras is used to guide the motion. No contact force sensor is used; instead, vision sensing of the probe bending is used for the grasp force control. By combining preplanned manipulation sequences and vision-based manipulation, repeatable spatial (in contrast with planar) manipulation and insertion of a submillimeter part have been demonstrated with an experimental testbed consisting of two actuated probes, a passive probe, an actuated die stage, and two cameras for vision feedback.

How to achieve durable pulmonary vein isolation: Use the force

How to achieve durable pulmonary vein isolation: Use the force

The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study

The clinical efficacy of catheter ablation of paroxysmal atrial fibrillation (AF) remains limited by difficulty in achieving durable pulmonary vein isolation (PVI). Suboptimal catheter tip-to-tissue contact force (CF) during lesion delivery is believed to reduce clinical efficacy. To determine the relationship between catheter CF during irrigated catheter ablation for AF and clinical recurrences during follow-up. Thirty-two patients with paroxysmal AF underwent PVI by using a radiofrequency ablation catheter with a CF sensor integrated at its tip, and they were followed for 12 months. The relationship between the CF and clinical outcomes was determined. Acute PVI was achieved in 100% of the veins. Thirty-five percent (351 of 1017) of the applications were placed with an average CF of <10 g (low CF). All patients treated with an average CF of <10 g (5 of 5 patients) experienced recurrences, whereas 80% of the patients treated with an average CF of >20 g (8 of 10 patients) were free from AF recurrence at 12 months. The analysis of the average force-time integral showed that 75% of the patients treated with <500 gs were recurrent whereas only 31% of the patients treated with >1000 gs had recurrences at 12 months. The CF during catheter ablation for AF correlates with clinical outcome. Arrhythmia control is best achieved when ablation lesions are placed with an average CF of >20 g, and clinical failure is universally noted with an average CF of <10 g.

Highly Sensitive Compact Force Sensor Based on Microfiber Bragg Grating

We present and demonstrate a miniature contact force sensor based on a 30-μm diameter microfiber Bragg grating. The microfiber Bragg grating packaged in a conforming elastomer material features an extremely high sensitivity of 1.37 mN and excellent linearity up to a contact force of 0.65 N. The performances were experimentally characterized and meet all the essential specifications as minimally invasive surgery devices for catheters' applications. The novel force sensor is easy to fabricate and thus potentially low cost.

혈압 측정을 위한 외팔보형 접촉힘 센서 어레이

Piezoresistive type contact force sensor array is fabricated by (111) Silicon bulk micromachining for continuous blood pressure monitoring. Length and width of the unit sensor structure is <TEX>$200{\mu}m$</TEX> and <TEX>$190{\mu}m$</TEX>, respectively. The gap between sensing elements is only <TEX>$10{\mu}m$</TEX>. To achieve wafer level packaging, the sensor structure is capped by PDMS soft cap using wafer molding and bonding process with <TEX>$10{\mu}m$</TEX> alignment precision. The resistance change over contact force was measured to verify the feasibility of the proposed sensor scheme. The maximum measurement range and resolution is 900 mm Hg and 0.57 mm Hg, respectively.

Superstructured fiber-optic contact force sensor with minimal cosensitivity to temperature and axial strain

In this work a new superstructured, in-fiber Bragg grating (FBG)-based, contact force sensor is presented that is based on birefringent D-shape optical fiber. The sensor superstructure comprises a polyimide sheath, a stress-concentrating feature, and an alignment feature that repeatably orients the sensor with respect to contact forces. A combination of plane elasticity and strain-optic models is used to predict sensor performance in terms of sensitivity to contact force and axial strain. Model predictions are validated through experimental calibration and indicate contact force, axial strain, and temperature sensitivities of 169.6 pm/(N/mm), 0.01 pm/με, and -1.12 pm/°C in terms of spectral separation. The sensor addresses challenges associated with contact force sensors that are based on FBGs in birefringent fiber, FBGs in conventional optical fiber, and tilted FBGs. Relative to other birefringent fiber sensors, the sensor has contact force sensitivity comparable to the highest sensitivity of commercially available birefringent fibers and, unlike other birefringent fiber sensors, is self-aligning with respect to contact forces. Unlike sensors based on Bragg gratings in conventional fiber and tilted Bragg gratings, the sensor has minimal cosensitivity to both axial strain and changes in temperature.

Contact force–controlled zero-fluoroscopy catheter ablation of right-sided and left atrial arrhythmia substrates

Conventional catheter ablation of cardiac arrhythmias is associated with radiation risks for patients and laboratory personnel. However, nonfluoroscopic catheter guidance may increase the risk for inadvertent cardiac injury. A novel radiofrequency ablation catheter capable of real-time tissue-tip contact force measurements may compensate for nonfluoroscopic safety issues. To investigate the feasibility of contact force-controlled zero-fluoroscopy catheter ablation. In 30 patients (including 12 pediatric patients), zero-fluoroscopy catheter ablation of right-sided (right atrium, n = 20; right ventricle, n = 2) and left atrial (n = 8) arrhythmias was attempted. Inclusion criteria were symptomatic suspected atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, focal right atrial and ventricular arrhythmias, and lone atrial fibrillation. A novel irrigated-tip catheter with an integrated contact force sensor was used for nonfluoroscopic 3-dimensional electroanatomical mapping and radiofrequency ablation. Transseptal access was gained under transesophageal guidance for ablation of left-sided arrhythmias. Procedural success without fluoroscopy was achieved in 29 of the 30 patients (97%). In 1 patient, endocardial nonfluoroscopic ablation failed because of an epicardial accessory pathway within a coronary sinus aneurysm. Mean total contact force and amplitude of force undulations were kept below 50 g during mapping and below 40 g during ablation to prevent contact force peaks (>100 g). Apart from a transient second-degree type I atrioventricular block, no complications occurred. The mean procedure time was 2.8 ± 0.9 hours. There were no arrhythmia recurrences during a mean follow-up of 6.2 ± 4.2 months. Contact force-controlled zero-fluoroscopy catheter ablation is generally feasible in right-sided and left atrial cardiac arrhythmias.

Design of a Lightweight, Cost Effective Thimble-Like Sensor for Haptic Applications Based on Contact Force Sensors

This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i) force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii) the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation.

Abstract 17234: The EFFICAS Studies: Reducing Low Force-Time Integral (FTI) Radiofrequency Applications Improves Procedural Efficacy During Pulmonary Vein Isolation

Objectives Results of the EFFICAS I study illustrate that in patients with paroxysmal atrial fibrillation (PAF) undergoing pulmonary vein isolation (PVI), ablation using low Force-Time Integral (FTI &lt;400 gs) predicts early gap formation. The EFFICAS II multicenter study prospectively evaluated whether limiting the number of low FTI ablations during PVI improves procedural efficacy. Methods Patients with PAF underwent PVI using an ablation catheter with an integrated Contact Force (CF) sensor (TactiCath®, Endosense, Switzerland). Operators were requested to start ablation when CF was ≥ 10 g and to avoid ablations with FTI &lt; 400 gs, thereby demonstrating good catheter stability. Procedure duration, RF ablation time, number of ablations for PVI and fluoroscopy time were compared between EFFICAS I and EFFICAS II. Results Five operators in 3 centers treated 30 patients in EFFICAS I and 34 patients in EFFICAS II. All PVs (100%) were isolated at the end of the procedure. In EFFICAS I, 42% of 2060 ablations were performed with an FTI &lt; 400 gs, compared to 18% of 1860 ablations applied in EFFICAS II. There was a statistically significant reduction in RF ablation time, number of ablations, and fluoroscopy time in EFFICAS II as compared to EFFICAS I (table). Conclusions Reducing the number of radiofrequency ablations with an FTI &lt; 400 gs increases the efficacy of ablation during PVI. Whether more effective ablation will increase safety and improve outcome following PVI needs to be determined.

A flexible tri-axis contact force sensor for tubular medical device applications

A capacitive, tube-shaped tri-axis contact force sensor is fabricated and characterized in this paper. The sensor is inserted into a tubular medical device just like a small section of tube in order to sense the applied contact force on the tip of this tubular device. It comprises two SU-8 plates, wherein the outer and inner rims of the plates with diameters of 2.3 and 1.1 mm, respectively, are assembled together. Three proof masses were hinged to the outer and inner rims of the first plate by membranes. The different signals received from the three electrodes provide collective information indicating the precision and accurate direction of contact forces exerted on the tip of the tubular medical device. In the test, applied force range from 10 mN to 1.0 N was detected, the performance of the sensor is stable from 25 to 65 °C, and the device was functional under a shock of 2.0 N for 10 s in a shock test. In addition, a two-wire readout approach was also developed to minimize the lead wires.

1A1-L02 床反力計測に基づく力学同定を用いた産業用ロボットのIDCS制御(動作計画と制御の新展開)

1A1-L02 床反力計測に基づく力学同定を用いた産業用ロボットのIDCS制御(動作計画と制御の新展開)

An in-fiber Bragg grating sensor for contact force and stress measurements in articular joints

We present an in-fiber Bragg grating-based sensor (240 µm diameter) for contact force/stress measurements in articular joints. The contact force sensor and another Bragg grating-based pressure sensor (400 µm diameter) are used to conduct the first simultaneous measurements of contact force/stress and fluid pressure in intact cadaveric human hips. The contact force/stress sensor addresses limitations associated with stress-sensitive films, the current standard tools for contact measurements in joints, including cartilage modulus-dependent sensitivity of films and the necessity to remove biomechanically relevant anatomy to implant the films. Because stress-sensitive films require removal of anatomy, it has been impossible to validate the mechanical rationale underlying preventive or corrective surgeries, which repair these anatomies, by conducting simultaneous stress and pressure measurements in intact hips. Methods are presented to insert the Bragg grating-based sensors into the joint, while relevant anatomy is left largely intact. Sensor performance is predicted using numerical models and the predicted sensitivity is verified through experimental calibrations. Contact force/stress and pressure measurements in cadaveric joints exhibited repeatability. With further validation, the Bragg grating-based sensors could be used to study the currently unknown relationships between contact forces and pressures in both healthy and degenerated joints.

Novel Contact Force Sensor Incorporated in Irrigated Radiofrequency Ablation Catheter Predicts Lesion Size and Incidence of Steam Pop and Thrombus

An open-irrigated radiofrequency (RF) ablation catheter was developed to measure contact force (CF). Three optical fibers measure microdeformation of the catheter tip. The purpose of this study was to (1) validate the accuracy of CF sensor (CFS) (bench test); and (2) determine the relationship between CF and tissue temperatures, lesion size, steam pop, and thrombus during RF ablation using a canine thigh muscle preparation. CFS measurements (total 1409) from 2 catheters in 3 angles (perpendicular, parallel, and 45 degrees ) were compared with a certified balance (range, 0 to 50 g). CFS measurements correlated highly (R(2) > or =0.988; mean error, < or =1.0 g). In 10 anesthetized dogs, a skin cradle over the thigh muscle was superfused with heparinized blood at 37 degrees C. A 7F catheter with 3.5-mm saline-irrigated electrode and CFS (Endosense) was held perpendicular to the muscle at CF of 2, 10, 20, 30, and 40 g. RF was delivered (n=100) for 60 seconds at 30 or 50 W (irrigation 17 or 30 mL/min). Tissue temperature (3 and 7 mm depths), lesion size, thrombus, and steam pop increased significantly with increasing CF at each RF power. Lesion size was greater with applications of lower power (30 W) and greater CF (30 to 40 g) than at high power (50 W) with lower CF (2 to 10 g). This novel ablation catheter, which accurately measures CF, confirmed CF is a major determinant of RF lesion size. Steam pop and thrombus incidence also increases with CF. CFS in an open-irrigated ablation catheter that may optimize the selection of RF power and application time to maximize lesion formation and reduce the risk of steam pop and thrombus.

Force control of a very lightweight single-link flexible arm based on coupling torque feedback

In this paper, a feedback control law is proposed for regulating the contact force exerted by a very lightweight single-link flexible manipulator when it comes into contact with a motionless object. This control law is based on a lumped-parameter model. The tracking of the desired contact force is obtained by using a feedback loop control of the coupling torque between the motor and the flexible arm. To achieve a good performance on the force control it is only necessary to measure the coupling torque at the root of the arm. Neither the contact force sensor nor the angular position sensor of the motor are used in the control method. A modified PID controller is proposed for this control law. In this work the force control problem is studied for both free and constrained motions of the flexible manipulator, and a collision detection algorithm is also described.

Abstract 3223: Feasibility and Safety of the Integrated 3D Image and Contact Force-Guided Ablation for Atrial Fibrillation with the Hansen Robotic Catheter Sheath System

Background: Current technologies to fully “register” surrogate maps onto 3D CT (CartoMerge, NavxMerge) or 3D ICE images (CartoSound) have emerged to guide ablation. The feasibility of navigation with the Hansen Robotic Catheter Sheath System (HRCS) has also been reported. Integrated 3D Image and contact force sensor with this robotic system may allow for feasibility and safety for guiding complex anatomic-based ablation. Methods: Circumferential pulmonary vein (PV) ablation with the robotic system guided by integrated 3D images (CartoMerge, NavxMerge or CartoSound) (n=3), were done and compared to manual manipulation guided by the integrated 3D images (CartoSound) (n=8). Each ablation was performed using contact force ranges of 10 –20 grams (20W, 17 ml/min flow, 30 seconds). Accuracy of PV ablation was assessed by comparing distance from the PV ostia (specific 4 sites) to the ablative points on the 3D image structures, and the corresponding distances of the actual ablative lesions at pathologic exam. Results: Using three integrated 3D image systems, circumferential PV ablation was successfully guided in 6 PVs (3 RSPVs and 3 LSPVs) with the robotic system. During all ablations with contact forces of 10 –20 grams, no impedance rises, pops or type 2 microbubbles were seen. Accuracy of the PV ablation was 0.22±0.84 mm (range 0 –2). The PV rings were 100% circumferential by electroanatomic mapping, yielding an 86±7% (range 80 –98%) uninterrupted circumferential ablative ring around each PV with 1.1 ± 0.4 gaps (3.0 ± 0.9 mm). These resulting parameters were equal to those in the integrated 3D image-based manual navigation (Accuracy: 0.5±0.9 (range 0 –2.5) mm, Gaps:1.3 ± 0.9 ( 2.6 ± 0.9 mm), circumferential lesions 88 ± 10% (range 70 –100). Conclusions: This feasibility study demonstrated successful integrated 3D image and contact force-guided robotic ablation. Contact sensor guided 3D volume construction and real time 3D images accurately replicated atrial and venous anatomy, resulting in successful circumferential ablation.

柔軟接触部を有する4軸接触力計測センサの開発

柔軟接触部を有する4軸接触力計測センサの開発

柔軟接触型4軸力センサの開発(触覚・力覚2)

柔軟接触型4軸力センサの開発(触覚・力覚2)

Contact force sensor for artificial hands with a digital interface for a controller

A force sensor, for use with an artificial hand, needs to be small, robust, lowpower, cheap and easily interfaced to a controller using digital techniques. Theprototype featured in this paper uses capacitance effects to measure the strain onan elastic polymer foam. Low power consumption results in a device that can besupplied from a miniature battery thereby requiring only signal wires to thecontroller. A non-linear model accurately describes the characteristic of thesensor, requiring the estimation of only three parameters. The devicehas been tested up to 20 N but is capable of measuring greater forces.

2P1-J05 柔軟構造を用いた微小接触力計測センサの開発

2P1-J05 柔軟構造を用いた微小接触力計測センサの開発