scholarly journals A Vision-Based Approach for Estimating Contact Forces: Applications to Robot-Assisted Surgery

2005 ◽  
Vol 2 (1) ◽  
pp. 53-60 ◽  
Author(s):  
C. W. Kennedy ◽  
J. P. Desai
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Real Time ◽  
Force Feedback ◽  
Element Model ◽  
Robot Arm ◽  
Robot Assisted ◽  
Interaction Forces ◽  
Fem Model ◽  
Nodal Displacements

The primary goal of this paper is to provide force feedback to the user using vision-based techniques. The approach presented in this paper can be used to provide force feedback to the surgeon for robot-assisted procedures. As proof of concept, we have developed a linear elastic finite element model (FEM) of a rubber membrane whereby the nodal displacements of the membrane points are measured using vision. These nodal displacements are the input into our finite element model. In the first experiment, we track the deformation of the membrane in real-time through stereovision and compare it with the actual deformation computed through forward kinematics of the robot arm. On the basis of accurate deformation estimation through vision, we test the physical model of a membrane developed through finite element techniques. The FEM model accurately reflects the interaction forces on the user console when the interaction forces of the robot arm with the membrane are compared with those experienced by the surgeon on the console through the force feedback device. In the second experiment, the PHANToM haptic interface device is used to control the Mitsubishi PA-10 robot arm and interact with the membrane in real-time. Image data obtained through vision of the deformation of the membrane is used as the displacement input for the FEM model to compute the local interaction forces which are then displayed on the user console for providing force feedback and hence closing the loop.

scholarly journals Piezoelectric Beam Finite Element Model and Its Reduction and Control

2021 ◽  
Vol 71 (1) ◽  
pp. 87-106
Author(s):  
Kutiš Vladimír ◽  
Paulech Juraj ◽  
Gálik Gálik ◽  
Murín Justín
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
State Space ◽  
State Space Model ◽  
Element Model ◽  
Functionally Graded ◽  
Fem Model ◽  
Space Model ◽  
Piezoelectric Beam ◽  
Reduced State

Abstract The paper deals with the development of the finite element method (FEM) model of piezoelectric beam elements, where the piezoelectric layers are located on the outer surfaces of the beam core, which is made of functionally graded material. The created FEM model of piezoelectric beam structure is reduced using the modal truncation method, which is one of model order reduction (MOR) method. The results obtain from reduced state-space model are compared with results obtain from finite element model. MOR state-space model is also used in the design of the linear quadratic regulator (LQR). Created reduced state-space model with feedback with the LQR controller is analysed and compared with the results from FEM model.

Methods for Reducing a Thermal Finite Element Model Including the Advection Network Contribution

2006 ◽  
Author(s):  
Daniele Botto ◽  
Stefano Zucca ◽  
Muzio M. Gola
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Real Time ◽  
Residual Life ◽  
Mathematical Formulation ◽  
Time Integration ◽  
Element Model ◽  
Computational Time ◽  
Fatigue Damage Accumulation ◽  
Secondary Air

The life monitoring concept needs on-line calculation to evaluate stresses and temperatures on aircraft engine components, in order to asses fatigue damage accumulation and residual life. Due to the amount of computational time required it is not possible for a full finite element model to operate in real time using the on-board CPU. Stresses and temperatures are then evaluated by using simplified algorithms. In the present work Guyan reduction and component mode synthesis have been applied to a thermal finite element model, including the cooling stream flow — the so called advection network — in order to reduce the size of the solving equation system. The appropriate mathematical formulation for the advection network reduction has been developed. Two reduction methods have been performed, discussed and subsequently applied to a thermal finite element model of a real low pressure turbine disk. The reduced system includes both the disk and the correlated fluid network model, simulating turbine secondary air system. The finite element model is axi-symmetric, with constant convective coefficients. Results of time integration for the reduced and the complete models have been compared. Results show that the proposed techniques gives models with a reduced number of degrees of freedom and at the same time good accuracy in temperature calculation. The reduced models are then suitable for real time computation.

The Influence of Residual Stress on the Machining Deformation

2012 ◽  
Vol 426 ◽  
pp. 172-176
Author(s):  
Hun Guo
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Finite Element Model ◽  
Simulation Model ◽  
Elasticity Theory ◽  
Initial Stress ◽  
Fem Simulation ◽  
Element Model ◽  
Fem Model ◽  
Simulation Results

The key problems in 2D FEM simulation such as the establishment of finite element model, the initial stress loading, the distortion appraisal are solved and 2D FEM simulation model is built to analyze the milling distortion caused by the residual stress. The FEM model is verified by the elasticity theory. Some machining cases are simulated by using of the FEM model. The machining distortion caused by residual stress are analyzed and summarized using the simulation results.

Analysis on the Upholding Bracket for Bridge Fabricating System & the Building of its FEM Model

2012 ◽  
Vol 472-475 ◽  
pp. 641-644
Author(s):  
Quan Cai Li ◽  
Cui Rong Wu
Keyword(s):  
Finite Element ◽  
Structural Analysis ◽  
Finite Element Model ◽  
Static Analysis ◽  
Large Scale ◽  
Element Model ◽  
Fem Model ◽  
At Home

Bridge Fabricating System is one of the most widely used large-scale machinery equipment in construction fields like highway, railway both at home and abroad. Through structural analysis on the bridge fabricating system, and build a finite element model with ANSYS, we can form a found- ation for Static Analysis for it.

scholarly journals Dynamic Path Planning for Bevel-Tip Flexible Needle Insertion into Soft Tissue Based on a Real-Time Finite Element Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Murong Li ◽  
Dedong Gao ◽  
Yong Lei ◽  
Tian Xu
Keyword(s):  
Finite Element ◽  
Soft Tissue ◽  
Path Planning ◽  
Finite Element Model ◽  
Real Time ◽  
Ccd Camera ◽  
Element Model ◽  
Online Planning ◽  
Dynamic Path Planning ◽  
Dynamic Path

This paper presents a novel dynamic path planning methodology for needle steering into the soft tissue. A real-time finite element model is used to simulate the procedure of a flexible needle into the homogeneous soft tissue, which provides the dynamic deformation information for the path planning. The relationship between needle base and tip is formulated as the transformations of homogeneous matrix with quasi-static assumptions. Based on the reachability of the flexible needle, the real-time motions of obstacles and target are considered through the dynamic needle-tissue interactions. A testbed including a XY linear stage, one rotator, and a CCD camera is constructed, and the experiments are designed to validate the proposed method. The 23G PTC needle was inserted into the PVA phantom with markers, and the CCD camera was utilized to record the needle trajectories and motions of target and obstacles. The targeting errors between the experimental and planned paths are less than 1.20 mm, and the distance from the obstacle to needle is not smaller than 1.16 mm. The results demonstrate that the proposed algorithm is effective for online planning the paths in the needle-tissue interactive environment.

A Real-Time Neural Network Estimator for Workpiece Thermal Expansion Errors

2000 ◽  
Author(s):  
A. D. Yoder ◽  
R. N. Smith
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Thermal Expansion ◽  
Finite Element Model ◽  
Real Time ◽  
Element Model ◽  
Precision Machining ◽  
Machining Processes ◽  
The Neural Network ◽  
The Finite Element Model

Abstract The importance of predicting and reducing thermal expansion errors in workpieces is becoming greater as better precision machining processes are developed. An artificial neural network model to estimate the workpiece thermal expansion errors in real-time during precision machining operations is developed and compared with experimental results. A finite element model of workpiece thermal expansion has been created to predict expansions in a thin cylinder undergoing a turning process. The neural network has been trained using finite element model solutions over a range of conditions to allow for changing machining parameters. To realize “on-line” capability, the measurable values of heat flux into the workpiece, surface heat transfer coefficient, and tool location are used as inputs and the expansion as the output for the neural network. The estimations of the network are compared with experimental results from a turning process on a large diameter aluminum cylinder. There is reasonable agreement between measured and estimated expansions with an average error of 18%. The neural network has not been trained at the cutting conditions used during the experiment. The speed of the neural network estimation is much greater than the solution to the finite element model. The finite element model required over 15 minutes to solve on a Pentium 133Mhz computer. The neural network calculated the expansions easily at 1 Hz during the experiment on the same computer. With real-time estimation using measurable data, compensation can be made in the tool path to correct for these errors. The application of this method to precision machining processes has the capability of greatly reducing the error caused by workpiece thermal expansions.

Study on Ship Hull Deformation by Integrated Model of Hull with Shaft

2014 ◽  
Vol 904 ◽  
pp. 450-453
Author(s):  
Xiang Kui Ruan ◽  
Ping Yang ◽  
Xin Ping Yan ◽  
Zhe Huang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Working Condition ◽  
Element Model ◽  
Integrated Model ◽  
Container Ship ◽  
Accurate Calculation ◽  
Fem Model ◽  
Large Container ◽  
Basic Content

Hull deformation directly influences the working condition of propulsion shaft, so that the reasonable and accurate calculation of deformation is the basic content of research on ship propulsion system. This paper, basing on a large container ship, built up an integrated finite element model of the hull with the propulsion shaft. By employing inertial relief method, the hull deformation at place of shaft supports is calculated under different loading conditions. The results are compared with those from a hull FEM model without shaft. Some valuable conclusions are made from the results analysis.

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