Flexible Gantry Research Articles

Payload motion control for a varying length flexible gantry crane

Cranes play a very important role in transporting heavy loads in various industries. However, because of its natural swinging characteristics, the control of crane needs to be considered carefully. This paper presents a control approach to a flexible cable crane system in consideration of both rope length varying and system constraints. At first, from Hamilton's extended principle the equations of motion that characterized coupled transverse-transverse motions with varying rope length of the gantry are obtained. The equations of motion consist of a system of partial differential equations. Then, a barrier Lyapunov function is used to derive the control located at the trolley end that can precisely position the gantry payload and minimize vibrations. The designed control is verified through extensive experimental studies.

Input Preshaping Control of Flexible Gantry with Active Mass Damper

Input Preshaping Control of Flexible Gantry with Active Mass Damper

XperCT Sharpening Reconstruction for Cone-Beam Computed Tomography Guided Lung and Bone Interventions

AbstractC-arm cone-beam computed tomography (CBCT) is a valuable tool for three-dimensional navigation and mapping in the interventional radiology suite owing to its flexible gantry positioning, real-time three-dimensional volume acquisition, and reduced contrast and radiation use. Reports of CBCT-guided bone and lung interventions are relatively infrequent, however, possibly due in part to the lack of dedicated bone and lung reconstruction algorithms and concerns regarding insufficient lesion conspicuity. Two cases of an ad hoc intraprocedural CBCT sharpening reconstruction are presented in this article.

Vibration Suppression Control of a Flexible Gantry Crane System with Varying Rope Length

The paper presents a control approach to a flexible gantry crane system. From Hamilton’s extended principle the equations of motion that characterized coupled transverse-transverse motions with varying rope length of the gantry is obtained. The equations of motion consist of a system of ordinary and partial differential equations. Lyapunov’s direct method is used to derive the control located at the trolley end that can precisely position the gantry payload and minimize vibrations. The designed control is verified through extensive numerical simulations.

Visual Servoing of a Flexible Gantry Crane With a Sway Range Constraint

In this letter, the problem of moving a gantry crane with a flexible cable and a sway range constraint to the desired position is solved. The dynamic model of the flexible gantry crane system is built based on the absolute nodal coordinate formulation (ANCF), which is useful for analyzing flexible bodies. A novel controller is proposed to control the gantry crane to the desired position and guarantee the sway range constraint. Moreover, with the help of an eye-in-hand camera, an adaptive law is developed to detect the position of the object with respect to the base frame. The convergence of the cable's position to the desired position, the satisfaction of the sway range constraint, and the convergence of the estimated object's position to the real value are rigorously verified based on the Lyapunov theory. Simulation demonstrates the effectiveness of the proposed controller.

Weight-Bearing CT Imaging of the Lower Extremity

The purpose of this article is to describe weight-bearing CT of the lower extremity joints using a novel portable imager utilizing cone-beam CT technology. Cone-beam CT technology with new design and flexible gantry movements allows both supine and weight-bearing imaging of the lower extremities, with a reasonable radiation dose and excellent image quality. Weight-bearing CT of joints can provide important new clinical information in musculoskeletal radiology.

Laser‐driven beam lines for delivering intensity modulated radiation therapy with particle beams

Laser-accelerated particles are a promising option for radiation therapy of cancer by potentially combining a compact, cost-efficient treatment unit with the physical advantages of charged particle beams. To design such a treatment unit we consider different dose delivery schemes and analyze the necessary devices in the required particle beam line for each case. Furthermore, we point out that laser-driven treatment units may be ideal tools for motion adaptation during radiotherapy. Reasons for this are the potential of a flexible gantry and the time structure of the beam with high particle numbers in ultrashort bunches. One challenge that needs to be addressed is the secondary radiation produced in several beam line elements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Vibration Analysis of Flexible Gantry Crane System Subjected Swinging Motion of Payload

Vibration Analysis of Flexible Gantry Crane System Subjected Swinging Motion of Payload

A microPET/CT system for in vivo small animal imaging

A microCT scanner was designed, fabricated and integrated with a previously reported microPET II scanner (Tai et al 2003 Phys. Med. Biol. 48 1519, Yang et al 2004 Phys. Med. Biol. 49 2527), forming a dual modality system for in vivo anatomic and molecular imaging of the mouse. The system was designed to achieve high-spatial-resolution and high-sensitivity PET images with adequate CT image quality for anatomic localization and attenuation correction with low x-ray dose. The system also has relatively high throughput for screening, and a flexible gantry and user interface. X-rays were produced by a 50 kVp, 1.5 mA fixed tungsten anode tube, with a focal spot size of 70 µm. The detector was a 5 × 5 cm2 photodiode detector incorporating 48 µm pixels on a CMOS array and a fast gadolinium oxysulfide (GOS) intensifying screen. The microCT system has a flexible C-arm gantry design with adjustable detector positioning, which acquires CT projection images around the common microPET/CT bed. The design and the initial characterization of the microCT system is described, and images of the first mouse scans with microPET/CT scanning protocols are shown.

Geometric errors and uncertainty caused by gantry tilt in 3D reconstructions of CT data

This paper presents new feedback actuators to achieve an accurate position control of a flexible gantry robot arm. The translational motion in the plane is generated by two d.c. motors and controlled by electro-rheological (ER) clutch actuators. The generated motion can be continuously controlled by controlling the intensity of electric fields imposed to the ER fluid domains of bi-directional rotating ER clutches. On the other hand, during control action of the translational motion, a flexible arm attached to the moving part produces undesirable oscillations due to its inherent flexibility. The oscillations are actively suppressed by employing feedback voltage to the piezoceramic actuator bonded on the surface of the flexible arm. Consequently, an accurate position control at the end-point of the flexible arm can be achieved. In order to accomplish this control target, the governing equations of the proposed system are derived and rewritten as transfer functions to design a robust H∞ controller. The control electric fields to be applied to the ER clutch and the control voltage for the piezoceramic actuator are determined via the loop shaping design procedures (LSDP) in the H∞ control technique. Control results of position regulating and tracking are provided to evaluate the effectiveness of the proposed methodology.

Position control of a flexible gantry robot arm using smart material actuators

This article presents new feedback actuators that achieve accurate position control of a flexible gantry robot arm. Translational motion in the plane is generated by two dc motors and controlled by applying electric fields to electro-rheological (ER) clutch actuators. On the other hand, during control action of translational motion, a flexible arm attached to the moving part produces undesirable oscillations due to its inherent flexibility. Oscillations are actively suppressed by employing feedback voltage to the piezoceramic actuator attached to the surface of the flexible arm. Consequently, an accurate position control at the end-point of the flexible arm can be achieved. To accomplish this control goal, governing equations of the proposed system are derived and written as transfer functions. Transfer functions are used in design of a set of robust H∞ controllers. Electric fields to be applied to ER clutch and control voltage for the piezoceramic actuator are determined via H∞ methodology which is incorporated with classical loop shaping design technique. To evaluate effectiveness of the proposed control system, experiments for both regulating and tracking controls are undertaken. ©1999 John Wiley & Sons, Inc.

H ∞ control of a flexible gantry robot arm using smart actuators

This paper presents new feedback actuators to achieve an accurate position control of a flexible gantry robot arm. The translational motion in the plane is generated by two d.c. motors and controlled by electro-rheological (ER) clutch actuators. The generated motion can be continuously controlled by controlling the intensity of electric fields imposed to the ER fluid domains of bi-directional rotating ER clutches. On the other hand, during control action of the translational motion, a flexible arm attached to the moving part produces undesirable oscillations due to its inherent flexibility. The oscillations are actively suppressed by employing feedback voltage to the piezoceramic actuator bonded on the surface of the flexible arm. Consequently, an accurate position control at the end-point of the flexible arm can be achieved. In order to accomplish this control target, the governing equations of the proposed system are derived and rewritten as transfer functions to design a robust H ∞ controller. The control electric fields to be applied to the ER clutch and the control voltage for the piezoceramic actuator are determined via the loop shaping design procedures (LSDP) in the H ∞ control technique. Control results of position regulating and tracking are provided to evaluate the effectiveness of the proposed methodology.

New spherical PET design with fresnel aperture orientation

AbstractA new spherical PET using Fresnel aperture is being designed, and construction is in progress. In the new design, the original spherical geometry is modified to accommodate a more flexible gantry construction and data processing while preserving the focused geometry of the original design. The performance of this new Fresnel aperture‐SPET (F‐SPET) is expected to follow closely with that of the original S‐PET design. An analysis of an F‐SPET designed with nine modular layers, with each modular layer being four rings, was performed in terms of the counting statistics and solid angle and compared with the original S‐PET as well as the conventional cylindrical PET. According to the simulation results, the sensitivity gain of the Fresnel aperture‐SPET remains a factor of 2 over the equivalent cylindrical system and has nearly the same performance as the original S‐PET, while offering a simpler means in construction and data handling for the image reconstruction.