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At least 1,549 records · Page 86Linked to original sources
PubMed1988

Method of formation of artificial organ components using a plastic dispenser system manipulated by a robot.

In order to produce an artificial organ component having a complicated structure, a plastic-forming method was proposed in which small amounts of material were accumulated successively by using a dispenser system manipulated by a robot; a preliminary experiment with silicone rubber was conducted. Components of different shapes were produced, including straight tubes, tapered tubes, bifurcating tubes, tubes having leaflets on the inside, cones, spiral tubes, and tubes with a sack. This method provides the possibility of producing complicated artificial organ components, which are difficult to produce by conventional plastic-processing methods.

Artificial Organs↗
PubMedDate not supplied

Improvement of accuracy in a high-capacity, six degree-of-freedom load cell: application to robotic testing of musculoskeletal joints.

This study investigated a previously unaccounted for source of error in a high-capacity, six degree-of-freedom load cell used in multi-degree-of-freedom robotic testing of musculoskeletal joints, an application requiring a load cell with high accuracy in addition to high load capacity. A method of calibration is presented for reducing the error caused by changes in universal force-moment sensor (UFS) orientation within a gravitational field. Uncorrected, this error can exceed a magnitude of 1% of the full-scale load capacity-the manufacturer-stated accuracy of the UFS. Implementation of the calibration protocol reduced this error by approximately 75% for a variety of loading conditions. This improvement in load cell accuracy (while maintaining full load capacity) should improve both the measurement and control of specimen kinetics by robotic/UFS and other biomechanical testing systems.

Bias↗
PubMed2004

A novel robotic system for joint biomechanical tests: application to the human knee joint.

The objectives of the work reported in this article were to develop a novel 6-degree-of-freedom (DOC) robotic system for knee joint biomechanics, to complete a hybrid force-position control scheme, to evaluate the system performance, and to demonstrate a combined loading test. The manipulator of the system utilizes two mechanisms; the upper mechanism has two translational axes and three rotational axes while the lower mechanism has only a single translational axis. All axes were driven with AC servo-motors. This unique configuration results in a simple kinematic description of manipulator motion. Jacobian transformation was used to calculate both the displacement and force/moment, which allowed for a hybrid control of the displacement of, and force/moment applied to, the human knee joint. The control and data acquisition were performed on a personal computer in the C-language programming environment with a multi-tasking operating system. Preliminary tests revealed that the clamp-to-clamp compliance of the system was smaller in the vertical (Z) and longitudinal (Y) directions (0.001 mm/N) than in lateral (X) direction (0.003 mm/N). The displacement error under the application of 500 N of load was smallest in the vertical direction (0.001 +/- 0.003 mm (mean +/- SD), and largest in the lateral direction (0.084 +/- 0.027 mm). Using this test system, it was possible to simulate multiple loading conditions in a human knee joint in which a cyclic anterior force was applied together with a coupled, joint compressive force, while allowing natural knee motion. The developed system seems to be a useful tool for studies of knee joint biomechanics.

Biomechanical Phenomena↗
PubMed2004

Design of an MRI-compatible robotic stereotactic device for minimally invasive interventions in the breast.

The objective of this work was to develop a robotic device to perform biopsy and therapeutic interventions in the breast with real-time magnetic resonance imaging (MRI) guidance. The device was designed to allow for (i) stabilization of the breast by compression, (ii) definition of the interventional probe trajectory by setting the height and pitch of a probe insertion apparatus, and (iii) positioning of an interventional probe by setting the depth of insertion. The apparatus is fitted with five computer-controlled degrees of freedom for delivering an interventional procedure. The entire device is constructed of MR compatible materials, i.e. nonmagnetic and non-conductive, to eliminate artifacts and distortion of the MR images. The apparatus is remotely controlled by means of ultrasonic motors and a graphical user interface, providing real-time MR-guided planning and monitoring of the operation. Joint motion measurements found probe placement in less than 50 s and sub-millimeter repeatability of the probe tip for same-direction point-to-point movements. However, backlash in the rotation joint may incur probe tip positional errors of up to 5 mm at a distance of 40 mm from the rotation axis, which may occur for women with large breasts. The imprecision caused by this backlash becomes negligible as the probe tip nears the rotation axis. Real-time MR-guidance will allow the physician to correct this error Compatibility of the device within the MR environment was successfully tested on a 4 Tesla MR human scanner

Algorithms↗
PubMed2005

Dynamic motion planning for the design of robotic gait rehabilitation.

In this paper we examine a method to control the stepping motion of a paralyzed person suspended over a treadmill using a robot attached to the pelvis. A leg swing motion is created by moving the pelvis without contact with the legs. The problem is formulated as an optimal control problem for an underactuated articulated chain. The optimal control problem is converted into a discrete parameter optimization and an efficient gradient-based algorithm is used to solve it. Motion capture data from an unimpaired human subject is compared to the simulation results from the dynamic motion optimization. Our results suggest that it is feasible to drive repetitive stepping on a treadmill by a paralyzed person by assisting in torso movement alone. The optimized, pelvic motion strategies are comparable to "hip-hiking" gait strategies used by people with lower limb prostheses or hemiparesis. The resulting motions can be found at the web site http://ww.eng.uci.edu/-chwang/project/stepper/stepper.html.

Computer Simulation↗
PubMed2005

An intelligent control method based on fuzzy logic for a robotic testing system for the human spine.

In previous biomechanical studies of the human spine, we implemented a hybrid controller to investigate load-displacement characteristics. We found that measurement errors in both position and force caused the controller to be less accurate than predicted. As an alternative to hybrid control, a fuzzy logic controller (FLC) has been developed and implemented in a robotic testing system for the human spine. An FLC is a real-time expert system that can emulate part of a human operator's knowledge by using a set of action rules. The FLC provides simple but robust solutions that cover a wide range of system parameters and can cope with significant disturbances. It can be viewed as a heuristic and modular way of defining a nonlinear, table-based control system. In this study, an FLC is developed which uses the force difference and the change in force difference as the input parameters, and the displacement as the output parameter. A rule-table based on these parameters is designed for the controller Experiments on a physical model composed of springs demonstrate the improved performance of the proposed method.

Algorithms↗
PubMed1999

An in vitro study of implant--tooth-supported connections using a robot test system.

Many unsolved problems in dental implant research concern the interfacial stress distributions between the implant components, as well as between the implant surface and contacting bone. To obtain a mechanical understanding of how vertical and horizontal occlusal forces are distributed in this context, it is crucial to develop in vitro testing systems to measure the force transmission between dental implants and attached prostheses. A new approach to such testing, involving a robotic system, is described in this investigation. The system has been designed to produce simulated mandibular movements and occlusal contact forces so that various implant designs and procedures can be thoroughly tested and evaluated before animal testing or human clinical trials. Two commonly used fixed prosthesis designs used to connect an implant and a tooth, a rigid connection and a nonrigid connection, were fabricated and used for experimental verification. The displacement and force distributions generated during simulated chewing activities were measured in vitro. Force levels, potentially harmful to human bone surrounding the connected dental implant and tooth, were analyzed. These results are useful in the design of prostheses and connecting components that will reduce failures and limit stress transfer to the implant/bone interface.

Computer Simulation↗
PubMed1995

Automated retinal robotic laser system.

Researchers at the University of Texas and the USAF Academy have worked toward the development of a retinal robotic laser system. The overall goal of this ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Recent efforts have concentrated on combining the two subsystems into a single prototype capable of simultaneously controlling both lesion depth and placement. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies.

Animals↗
PubMed2002

Robotic observations of dust storm enhancement of carbon biomass in the North Pacific.

Two autonomous robotic profiling floats deployed in the subarctic North Pacific on 10 April 2001 provided direct records of carbon biomass variability from surface to 1000 meters below surface at daily and diurnal time scales. Eight months of real-time data documented the marine biological response to natural events, including hydrographic changes, multiple storms, and the April 2001 dust event. High-frequency observations of upper ocean particulate organic carbon variability show a near doubling of biomass in the mixed layer over a 2-week period after the passage of a cloud of Gobi desert dust. The temporal evolution of particulate organic carbon enhancement and an increase in chlorophyll use efficiency after the dust storm suggest a biotic response to a natural iron fertilization by the dust.

Atmosphere↗
PubMed2006

Operation of a DNA robot arm inserted into a 2D DNA crystalline substrate.

The success of nanorobotics requires the precise placement and subsequent operation of specific nanomechanical devices at particular locations. The structural programmability of DNA makes it a particularly attractive system for nanorobotics. We have developed a cassette that enables the placement of a robust, sequence-dependent DNA robot arm within a two-dimensional (2D) crystalline DNA array. The cassette contains the device, an attachment site, and a reporter of state. We used atomic force microscopy to demonstrate that the rotary device is fully functional after insertion. Thus, a nanomechanical device can operate within a fixed frame of reference.

Crystallization↗
PubMed2000

Autonomous learning based on cost assumptions: theoretical studies and experiments in robot control.

Autonomous learning techniques are based on experience acquisition. In most realistic applications, experience is time-consuming: it implies sensor reading, actuator control and algorithmic update, constrained by the learning system dynamics. The information crudeness upon which classical learning algorithms operate make such problems too difficult and unrealistic. Nonetheless, additional information for facilitating the learning process ideally should be embedded in such a way that the structural, well-studied characteristics of these fundamental algorithms are maintained. We investigate in this article a more general formulation of the Q-learning method that allows for a spreading of information derived from single updates towards a neighbourhood of the instantly visited state and converges to optimality. We show how this new formulation can be used as a mechanism to safely embed prior knowledge about the structure of the state space, and demonstrate it in a modified implementation of a reinforcement learning algorithm in a real robot navigation task.

Algorithms↗
PubMed1999

Unsupervised learning and recall of temporal sequences: an application to robotics.

This paper describes an unsupervised neural network model for learning and recall of temporal patterns. The model comprises two groups of synaptic weights, named competitive feedforward and Hebbian feedback, which are responsible for encoding the static and temporal features of the sequence respectively. Three additional mechanisms allow the network to deal with complex sequences: context units, a neuron commitment equation, and redundancy in the representation of sequence states. The proposed network encodes a set of robot trajectories which may contain states in common, and retrieves them accurately in the correct order. Further tests evaluate the fault-tolerance and noise sensitivity of the proposed model.

Algorithms↗
PubMed1999

Autonomous learning based on cost assumptions: theoretical studies and experiments in robot control.

Autonomous learning techniques are based on experience acquisition. In most realistic applications, experience is time-consuming: it implies sensor reading, actuator control and algorithmic update, constrained by the learning system dynamics. The information crudeness upon which classical learning algorithms operate make such problems too difficult and unrealistic. Nonetheless, additional information for facilitating the learning process ideally should be embedded in such a way that the structural, well-studied characteristics of these fundamental algorithms are maintained. We investigate in this article a more general formulation of the Q-learning method that allows for a spreading of information derived from single updates towards a neighbourhood of the instantly visited state and converges to optimality. We show how this new formulation can be used as a mechanism to safely embed prior knowledge about the structure of the state space, and demonstrate it in a modified implementation of a reinforcement learning algorithm in a real robot navigation task.

Models, Theoretical↗
PubMed1999

Using a mobile robot to study locust collision avoidance responses.

The visual systems of insects perform complex processing using remarkably compact neural circuits, yet these circuits are often studied using simplified stimuli which fail to reveal their behaviour in more complex visual environments. We address this issue by testing models of these circuits in real-world visual environments using a mobile robot. In this paper we focus on the lobula giant movement detector (LGMD) system of the locust which responds selectively to objects which approach the animal on a collision course and is thought to trigger escape behaviours. We show that a neural network model of the LGMD system shares the preference for approaching objects and detects obstacles over a range of speeds. Our results highlight aspects of the basic response properties of the biological system which have important implications for the behavioural role of the LGMD.

Animals↗
PubMed2001

Robotics and radiosurgery--the cyberknife.

The Cyberknife is a dedicated image-guided robotic radiosurgical device. While clinical results with intracranial lesions are comparable to frame-based radiosurgical techniques, recent experience demonstrates the potential to broadly expand the scope of radiosurgery to many extracranial sites.

Aged↗
PubMed2004

Robotics in colorectal surgery.

Minimally invasive surgery has been shown to offer many advantages to general surgical patients but has not been widely adopted for colorectal disease. Initial fears surrounding the oncological safety of laparoscopic colectomies have largely subsided but the technical challenges still remain. Surgical robots or telemanipulators present the laparoscopic surgeon with unrivaled dexterity and vision, which may allow colonic resections to be completed with greater ease. Although initial studies suggest promising results using currently available systems, it will take further time for patient benefits to be proven, therefore justifying the greater expense of operating with this new technology.

Colonic Diseases↗
PubMed2005

Robotic-assisted anatomic radical prostatectomy: technical difficulties due to a large median lobe.

The case of a robot-assisted laparoscopic radical prostatectomy in a patient with a 143-gram prostate with a large median lobe is reported. The aim of the study was to delineate the difficulties and concern when confronted with such a situation. The technical difficulties, possible preventive methods, correction and management are discussed briefly with the hope of aiding urologists when performing radical prostatectomy in patients with large median lobe prostates.

Adenocarcinoma↗
PubMed2005

Volumetric resection using the SurgiScope: a quantitative accuracy analysis of robot-assisted resection.

OBJECTIVE: This study evaluates the hypothesis that current image guidance technology can effectively guide the resection of a predefined intracranial volume from the surgical field in the absence of a visually distinct lesion. METHODS: An in vitro model was constructed to simulate the resection of a visually nondistinct lesion. Preoperative CT was acquired, and the lesion was resected from the model with a cavitating ultrasonic aspirator using image guidance information provided by the SurgiScope system. RESULTS: On average, 77% of the 8.2-cm(3) surgical target volume was removed. Over a series of 5 trials, the underresection volume was 1.9 cm(3) on average or 23% of the surgical target volume. The overresection volume was 1.0 cm(3) on average, representing 13% of the surgical target volume. CONCLUSION: This in vitro model developed to evaluate the accuracy and limitations of our current image guidance technology provided quantitative data to demonstrate the potential for robotic navigation systems to guide the volumetric resection in the absence of visual differentiation between the lesion and the surrounding brain.

Models, Anatomic↗