Forbidden Region Virtual Fixture Research Articles

A feasibility study of eye gaze with biofeedback in a human-robot interface

ABSTRACT Play is a vital activity in which children learn skills and explore the environment through object manipulation. Assistive robots have been used to provide access to play, and Forbidden Region Virtual Fixture (FRVF) guidance at the user interface could help the users make the robot traverse the play environment more efficiently because it behaves like virtual walls to follow. Eye gaze was used to indicate the user’s intended target and generate the location of the virtual walls in a card sorting task. We eliminated the typical computer screen required for visual feedback to confirm gaze location, and examined the use of alternative feedback. In this feasibility study, first a group of adults without physical impairment tested the system with auditory and vibrotactile feedback modalities for the gaze fixation and with the virtual walls on and off for robot movement. Then case studies with children and individuals with physical impairments were performed. Even though gaze fixation feedback and the virtual wall did not improve the performance of adult participants without impairment, the feedback increased the speed and accuracy of the gaze fixation and the virtual walls improved the movement efficiency for the participants with impairment and a 6-year-old child without impairment.

An operating smooth man–machine collaboration method for cataract capsulorhexis using virtual fixture

Abstract Techniques in ophthalmic surgery require higher precision while cataract capsulorhexis calls for enough operating space. There is no specific methods focusing on improving the safety and flexibility of Capsulorhexis operation in recent study. Traditionally, Guidance Virtual Fixture based on parameter curve failed to be flexible, while Forbidden-Region Virtual Fixture using PD control failed to be steady enough. This paper proposes a teleoperation control scheme using integrated virtual fixture to assist in performing cataract capsulorhexis, improving operation performance in precision and flexibility. Specifically, based on the ring pipe model presented simulating the working path and permitted operating space, the control scheme is combined attractive error-reducing constraints with variety stiffness. It works by providing composite feedback force to the master-side via haptic device and letting the user aware if he on the right path and assist him in correcting operation mistakes. Experimental evaluation of the functionality of the control scheme was tested under four different configurations to verify the effectiveness of each algorithm and the combination. Significantly, the average error of operation reduces from 0.56 mm to 0.33 mm by 41% under the control scheme and reduces from 0.56 mm to 0.11 mm by 80% under the control scheme combined with motion scaling, demonstrating improvement in control by providing accurate assistance to the operator.

Haptic Guidance Based on All-Optical Ultrasound Distance Sensing for Safer Minimally Invasive Fetal Surgery.

By intervening during the early stage of gestation, fetal surgeons aim to correct or minimize the effects of congenital disorders. As compared to postnatal treatment of these disorders, such early interventions can often actually save the life of the fetus and also improve the quality of life of the newborn. However, fetal surgery is considered one of the most challenging disciplines within Minimally Invasive Surgery (MIS), owing to factors such as the fragility of the anatomic features, poor visibility, limited manoeuvrability, and extreme requirements in terms of instrument handling with precise positioning. This work is centered on a fetal laser surgery procedure treating placental disorders. It proposes the use of haptic guidance to enhance the overall safety of this procedure and to simplify instrument handling. A method is described that provides effective guidance by installing a forbidden region virtual fixture over the placenta, thereby safeguarding adequate clearance between the instrument tip and the placenta. With a novel application of all-optical ultrasound distance sensing in which transmission and reception are performed with fibre optics, this method can be used with a sole reliance on intraoperatively acquired data. The added value of the guidance approach, in terms of safety and performance, is demonstrated in a series of experiments with a robotic platform.

Haptic-Based Manipulation Scheme of Magnetic Nanoparticles in a Multi-Branch Blood Vessel for Targeted Drug Delivery.

Magnetic drug targeting is a promising technique that can deliver drugs to the diseased region, while keeping the drug away from healthy parts of body. Introducing a human in the control loop of a targeted drug delivery system and using inherent bilateralism of a haptic device at the same time can considerably improve the performance of targeted drug delivery systems. In this paper, we suggest a novel intelligent haptic guidance scheme for steering a number of magnetic nanoparticles (MNPs) using forbidden region virtual fixtures and a haptic rendering scheme with multi particles. Forbidden region virtual fixtures are a general class of guidance modes implemented in software, which help a human-machine collaborative system accomplish a specific task by constraining a movement into limited regions. To examine the effectiveness of our proposed scheme, we implemented a magnetic guided drug delivery system in a virtual environment using a physics-based model of targeted drug delivery including a multi-branch blood vessel and realistic blood dynamics. We performed user studies with different guidance modes: unguided, semi virtual fixture and full virtual fixture modes. We found out that the efficiency of targeting was significantly improved using the forbidden region virtual fixture and the proposed haptic rendering of MNPs. We can expect that using intelligent haptic feedback in real targeted drug delivery systems can improve the targeting efficiency of MNPs in multi-branch vessels.

Haptic Virtual Fixture for Robotic Cardiac Catheter Navigation

In manual or robot-assisted catheter intervention, excessive manipulation force may cause tissue perforation. Using images acquired by an imaging device routinely used for catheter interventions such as X-ray fluoroscopy, the structure and size of blood vessels and the relative position of the catheter tip inside the vessel can be obtained. To prevent collision of the catheter tip and the vessel wall, vision-assisted control methods using forbidden-region virtual fixture (FRVF) technique can be utilized and an experimental implementation has been performed in this study. A master-slave configured robotic platform for cardiac catheter was used for this study. The robotic master handle can provide haptic rendering to the user. A vessel phantom model mimicking human vasculature for the inner radii was fabricated for simulated intervention experiments. A digital optical camera was used for image acquisition. After the vessel phantom and the catheter tip were segmented, distance between the vessel centerline and the catheter tip was calculated and the forbidden region that the catheter tip should keep away from was set for the safe catheter manipulation. Virtual force generation algorithm was implemented for feeding the signal indicating the catheter tip penetrating into the forbidden region back to the user in the robotic master handle. To validate the suggested method, in vitro experiments were conducted. Through a chain of image filtering procedures including edge detection, the catheter tip and the vessel wall were able to be well segmented. The virtual force generator worked appropriately. The developed FRVF technique could provide helpful auxiliary information to clinicians for safer manipulation of catheters in cardiac catheterization procedures.

Increasing Accuracy in Image-Guided Robotic Surgery Through Tip Tracking and Model-Based Flexion Correction

Robot assistance can enhance minimally invasive image-guided surgery, but flexion of the thin surgical instrument shaft impairs accurate control by creating errors in the kinematic model. Two controller enhancements that can mitigate these errors are improved kinematic models that account for flexing and direct measurement of the instrument tip's position. This paper presents an experiment quantifying the benefits of these enhancements in an effort to inform development of an image-guided robot control system accurate in the presence of quasi-static instrument flexion. The study measured a controller's ability to guide a flexing instrument along user-commanded motions while preventing incursions into a forbidden region virtual fixture. Compared with the controller using neither enhancement, improved kinematics and reduced maximum incursion depth into the forbidden region by 28%, tip tracking by 67%, and both enhancements together by 83%.

Stable Forbidden-Region Virtual Fixtures for Bilateral Telemanipulation

There has been recent interest in novel human-machine collaborative control laws, called “virtual fixtures,” which provide operator assistance for telemanipulation tasks. A forbidden-region virtual fixture is a constraint, implemented in software, that seeks to prevent the slave manipulator of a master/slave telemanipulation system from entering into a forbidden region of the workspace. In this paper, we consider the problem of unstable vibrations of the slave and/or master against forbidden-region virtual fixtures for a general class of telemanipulator control architectures, including those with haptic feedback. To the best of the authors’ knowledge, there has been no rigorous study of the stability of forbidden-region virtual fixtures in previous work. The system is evaluated around the master and slave equilibrium position resulting from a constant desired human input force, using a discrete state-space model. We present a method to analytically determine if instability is possible in the system. We thoroughly evaluate this method, experimentally, applying malicious user strategies that attempt to drive the system unstable. Our approach agrees with experimental results and can be used to design and analyze the stability and transient properties of a telemanipulator interacting with virtual fixtures. We show that the user can affect both slave- and master-side virtual fixture stability by modifying his or her impedance characteristics. However, the upper bound on stable slave-side virtual fixture stiffness does not depend on the particular user.