Deformation Compensation Research Articles

Accelerating B-spline interpolation on GPUs: Application to medical image registration

Background and ObjectiveB-spline interpolation (BSI) is a popular technique in the context of medical imaging due to its adaptability and robustness in 3D object modeling. A field that utilizes BSI is Image Guided Surgery (IGS). IGS provides navigation using medical images, which can be segmented and reconstructed into 3D models, often through BSI. Image registration tasks also use BSI to transform medical imaging data collected before the surgery and intra-operative data collected during the surgery into a common coordinate space. However, such IGS tasks are computationally demanding, especially when applied to 3D medical images, due to the complexity and amount of data involved. Therefore, optimization of IGS algorithms is greatly desirable, for example, to perform image registration tasks intra-operatively and to enable real-time applications. A traditional CPU does not have sufficient computing power to achieve these goals and, thus, it is preferable to rely on GPUs. In this paper, we introduce a novel GPU implementation of BSI to accelerate the calculation of the deformation field in non-rigid image registration algorithms. MethodsOur BSI implementation on GPUs minimizes the data that needs to be moved between memory and processing cores during loading of the input grid, and leverages the large on-chip GPU register file for reuse of input values. Moreover, we re-formulate our method as trilinear interpolations to reduce computational complexity and increase accuracy. To provide pre-clinical validation of our method and demonstrate its benefits in medical applications, we integrate our improved BSI into a registration workflow for compensation of liver deformation (caused by pneumoperitoneum, i.e., inflation of the abdomen) and evaluate its performance. ResultsOur approach improves the performance of BSI by an average of 6.5× and interpolation accuracy by 2× compared to three state-of-the-art GPU implementations. Through pre-clinical validation, we demonstrate that our optimized interpolation accelerates a non-rigid image registration algorithm, which is based on the Free Form Deformation (FFD) method, by up to 34%. ConclusionOur study shows that we can achieve significant performance and accuracy gains with our novel parallelization scheme that makes effective use of the GPU resources. We show that our method improves the performance of real medical imaging registration applications used in practice today.

A Linear Regression Thermal Displacement Lathe Spindle Model

Thermal error is one of the main reasons for the loss of accuracy in lathe machining. In this study, a thermal deformation compensation model is presented that can reduce the influence of spindle thermal error on machining accuracy. The method used involves the collection of temperature data from the front and rear spindle bearings by means of embedded sensors in the bearing housings. Room temperature data were also collected as well as the thermal elongation of the main shaft. The data were used in a linear regression model to establish a robust model with strong predictive capability. Three methods were used: (1) Comsol was used for finite element analysis and the results were compared with actual measured temperatures. (2) This method involved the adjustment of the parameters of the linear regression model using the indicators of the coefficient of determination, root mean square error, mean square error, and mean absolute error, to find the best parameters for a spindle thermal displacement model. (3) The third method used system recognition to determine similarity to actual data by dividing the model into rise time and stable time. The rise time was controlled to explore the accuracy of prediction of the model at different intervals. The experimental results show that the actual measured temperatures were very close to those obtained in the Comsol analysis. The traditional model calculates prediction error values within single intervals, and so the model was divided to give rise time and stable time. The experimental results showed two error intervals, 19µm in the rise time and 15µm in the stable time, and these findings allowed the machining accuracy to be enhanced.

Thermal Deformation Compensation of Laser Tracker Relocating in Aircraft Assembly

During aircraft assembly, measurements from either a single or multiple laser tracker with different positions are transformed to an assembly coordinate system by measuring the enhanced reference system (ERS) points via a rigid-body registration method. The location deviations of the ERS points resulting from thermal deformations have become the major error source in registration. To improve the accuracy of measurement, a thermal deformation compensation method, based on precise thermal deformation theory, is proposed in this study. Thermal deformation coefficients of ERS points in X-, Y-, and Z-axes are calculated separately, and an iterative algorithm is developed to correct the actual locations of the ERS points and estimate the optimal coordinate transformation parameters. A case study indicated that, with our proposed novel thermal deformation compensation method, the average registration error is decreased by 9.2–38.7%, and the maximum registration error is deceased by 12.3–38.6%.

Static Deformation-Compensation Method Based on Inclination-Sensor Feedback for Large-Scale Manipulators with Hydraulic Actuation

Modern large-scale manipulators with hydraulic actuation like mobile concrete pump manipulators are increasingly used in industrial, construction, and other fields. Due to the large span of these manipulators, the static deformation accumulation to the endpoint has seriously affected the precise control of the endpoint. In this paper, we propose a static deformation-compensation method based on inclination sensor feedback for large-scale manipulators to reduce the deviation of the endpoint. Compared with the finite element method, this method does not need to consider many boundary conditions that are uncertain for flexible manipulators in most situations. It has appropriate accuracy and is universal for large-scale manipulators of different sizes and working under different loads. Based on a 24m-3R mobile concrete pump manipulator, the parametric simulation is carried out. The reliability of the static deformation-compensation method is verified, and the error is analyzed. The validity of the static deformation-compensation method is verified by comparing the theoretical endpoint position with the actual endpoint position after static deformation compensation. The compensation error under different loads is obtained, and the universality of the compensation method for different loads is verified.

Improving the measurement of thread parameters by use of corundum elements

Considered an advanced method of the three wires to measure the average diameter dav and pitch P of the thread using three elements corundum (synthetic sapphire, sapphire, ruby): two fibers and tip with the ability to visualize and measure the size of the contact zone with the product to calculate the contact elastic deformation. It is proposed to use two fibers incoherent and one coherent interferometers to measure the position of corundum fibers and the tip. A method for calculating the diameter dav and pitch P of the thread based on the results of interferometer measurements by using the compensation of contact elastic deformations is presented.

Условие абсолютной устойчивости системы управления электроупругим актюатором для наномехатроники

An electroelastic actuator for nanomechatronics is used in nanotechnology, adaptive optics, microsurgery, microelectronics, and biomedicine to actuate or control mechanisms, systems based on the electroelastic effect, and to convert electrical signals into mechanical displacements and forces. In nanomechatronic systems, a piezoactuator is used in scanning microscopy, laser systems, in astronomy for precision alignment, for compensation of temperature, gravitational deformations and atmospheric turbulence, focusing, and stabilizing the image. In this study, a condition for absolute stability of an electroelastic actuator control system for nanomechatronics under deterministic and random inputs is obtained. A number of equilibrium positions in an electroelastic actuator mechatronic control system are found, the totality of which is represented by a straight line segment. The electroelastic actuator’s deformation control system dead band relative width is determined for the actuator’s symmetric and asymmetric hysteresis characteristics. Under deterministic inputs and with fulfilling the condition for the derivative of the nonlinear hysteresis actuator deformation characteristic, the set of equilibrium positions of the electroelastic actuator control system for nanomechatronics is absolutely stable. Under random inputs, the system absolute stability with respect to the mathematical expectations of the electroelastic actuator mechatronic control system equilibrium positions has been determined subject to fulfilling the condition on the derivative of the actuator hysteresis characteristic.

Distortion prediction and compensation in direct laser deposition of large axisymmetric Ti-6Al-4V part

A Ti-6Al-4V alloy aircraft engine part consisting of a cylinder (inner radius 977 mm, height 250 mm and 7.5 mm wall thickness) and two flanges (10.5 and 13.5 mm thick) was manufactured by direct laser deposition technology. A two-dimensional thermomechanical model was developed to simulate distortion of large axisymmetric parts during direct laser deposition. As it was established the shape and dimensions of the finished part, simulated using the original CAD model, have unacceptable deviations from the required parameters. A significant correction of the model is necessary to ensure the required accuracy. It was found that for complete compensation of deformations, an initial geometry should be pre-distorted according to the inverted distortions predicted by the FE simulation. To prevent fracture of the build-up, an 8 mm thick flexible substrate was used. The DLD process stability was ensured by taking into account spatial position of the deposited part in the motion path of the processing head. The simulated shape and size of the finished part satisfactory agrees with the experimentally obtained.

Deformation control method for inorganic biological coating materials under tensile loading

In order to overcome the problem of long control period in traditional material deformation control methods, a new method for controlling the deformation of inorganic biological coating materials under tensile loading is proposed. This method classifies inorganic biological coating materials and studies the properties of different materials. By improving the preparation process of inorganic biological coating material, its strength was enhanced and deformation was restrained. Based on the above materials, the inorganic biological coating material is reprocessed by heat treatment and cold hardening, and the deformation compensation technology is adopted to further control the deformation of inorganic biological coating material. Experimental results show that the method in this paper can reduce the material deformation by 3.34%, and the control effect is good. The control period is always less than ten hours and the control period is short, which provides an important reference for the optimisation of inorganic biological coating materials.

Surface adjustment strategy for a large radio telescope with adjustable dual reflectors

With the development of large-aperture and high-frequency radio telescopes, a surface adjustment procedure for the compensation of surface deformations has become of great importance. In this study, an innovative surface adjustment strategy is proposed to achieve an automated adjustment for the large radio telescope with adjustable dual reflectors. In the proposed strategy, a high-precision and long-distance measurement instrument is adopted and installed on the back of the sub-reflector to measure the distances and elevation angles of the target points on the main reflector. Here, two surface adjustment purposes are discussed. The first purpose is to ensure that the main reflector and sub-reflector are always positioned at their ideal locations during operation. The second purpose is to adjust the main reflector to the location of the best fitting reflector, and the sub-reflector to the focus of the best fitting reflector. Next, the calculation procedures for the adjustments of the main reflector and the sub-reflector are discussed in detail, and corresponding simulations are carried out to verify the proposed method. The results show that the proposed strategy is effective. This study can provide helpful guidance for the design of automated surface adjustments for large telescopes.

The model and stress analysis of self-doping SiGe/Si multi-quantum wells applied in uncooled infrared focal plane array

Silicon-germanium multi-quantum wells (MQWs) film is a promising sensitive material with high temperature coefficient of resistance (TCR). This paper focuses on solving the stress problem of uncooled infrared focal plane array caused by intrinsic stress of MQWs films. First of all, the paper presents the accurate TCR model of MQWs, which is more consistent with the actual situation especially when the Fermi level enters the valence band. The energy bands distributions and each sub-band wavefunction of MQWs were calculated. The critical thickness analysis about epitaxial growth film was carried out for solving intrinsic stress of MQWs film, which leads to the deformation of pixel structure in the fabrication processes. The paper calculated the maximum film stress in completely strain state and derived the buckling of the bolometer. Tri-layer structure was applied in support beam design for the deformation compensation. The self-doping MQWs film was epitaxial growth on silicon substrate with buffer layer to overcome the lattice slips in experiments. The bolometer was fabricated and released without visible deformation utilizing the compensation methods. The ohmic-contact problems and signals were also mentioned in the paper. The thermal conductivity and capacity were calculated by means of thermal response experiments without infrared radiation.

Real-time thermal deformation compensation method for active phased array antenna panels

The electromagnetic (EM) performance of active phased array antennas (APAAs) is significantly influenced by thermal deformation of the antenna panels caused by thermal power consumption and ambient temperature change. This paper proposes a method to reduce the influence of thermal deformation on the EM performance of small APAAs via real-time compensation. In the proposed method, a thermal deformation prediction model is first constructed based on analysis of experimental data. The model is then used to accurately predict thermal deformation based on the measured values of several key temperature sensors in real time, and the EM performance is compensated by adjusting the array phase difference controlled by a phased shifter according to the predicted results. The results of experiments conducted indicate that the thermal deformation model has high prediction accuracy, and the decrease in EM performance caused by antenna panel thermal deformation is effectively reduced by the proposed method. Thus, the proposed method has positive implications for improving the overall performance of APAAs.

Dual-beam laser welding and seam accurately tracking control for 3D T-joint

The processing methods and quality of T-joint directly affect the performance of stiffened panels. In this paper, firstly, a ten-six axis dual-beam laser welding system is constituted to research the T-joint welding process. Then, the ten-six axis controller in laser welding system is designed to achieve the accurate controlling for position and attitude of welding head during 3D welding of T-joint. In addition, the real-time measurement on both sides of T-joint is adopted to enable deformation compensation and precise tracking for welding seam. Finally, the T-joint welding tests are carried out and the results show that the welding seam errors are within allowable range. Consequently, the dual-beam laser welding and seam tracking control technology presented in this study can meet the processing requirements for T-joint.

Synthesis of Measurement Method of Stressed — Deformed Condition of Complex Structures

Nowadays the most common instruments of measuring the stress-strain state of complex structures are strain gauges. As a rule, strain gages are connected to the measuring system according to the bridge scheme, it provides elimination of systematic errors of measurement and compensation of temperature deformations. The principles of constructing, designing and mathematical modeling of deformation and stresses of complex technical constructions with the help of strain gauges taking into account destabilizing factors are developed, which allows to significantly reduce the level of errors in relation to existing methods of measurement and known analogues.
 The analysis of the main destabilizing factors that limit the accuracy of measurement using strain gauge is carried out, are (Fig. 1—4):
 
 the random processes (noises, obstacles, etc.);
 the time changes of parameters of measuring transducers due to aging and physical degradation;
 the influence of external climatic and mechanical factors (temperature, humidity, etc.).
 
 The temperature error values are set for the most common alloys used for the manufacture of strain gauges, namely: constantan and karma.
 This work is aimed at finding ways to improve the accuracy of remote measurements and impedance of measuring devices of the stress — strain state, in particular strain gauges and strain gauges, by introducing improved theoretical calculations taking into account destabilizing factors, which makes it possible to reduce the level of errors with respect to known analogs in dozens of times.

An accelerated convergence approach for real-time deformation compensation in large thin-walled parts machining

Abstract Excessive static deformations often occur during the end-milling of large thin-walled parts, which play an important role in the aerospace industry. The real-time adjustment of axial cutting depth (ACD) is often adopted to compensate deformation errors. Owing to the coupling effect between the ACD and the force induced deformation, the iterative adjustment of ACD is needed. However, it may not converge with the limited adjustment times especially in high-speed machining with large ACD. We hereby propose an approach to speed up the convergence of the ACD iterative adjustment. Firstly, the real-time full compensation process, which is commonly used in the existing real-time compensation methods, is mathematically analyzed and proved to be only first-order convergent. Then, an approach based on the secant method, which provides a higher order of convergence, is developed and introduced into the real-time compensation process for large thin-walled plate machining. Finally, the superiority and effectiveness of the proposed approach are demonstrated through an ACD iterative adjustment simulation and an experiment of cutting square pockets.

Prediction and compensation of force-induced deformation for a dual-machine-based riveting system using FEM and neural network

Force-induced deformation of machine tools has a great influence on the workpiece dimension and surface quality. For the dual-machine-based riveting system, the great squeezing force during riveting process not only causes structural deformation of the machine tools but also leads to inaccurate positioning of the riveting bar and dimension deviation of riveted joints. Moreover, the force-induced deformation usually changes with the varying poses of the machine tools, which makes it more difficult to predict precisely. In this paper, an efficient prediction and compensation method of force-induced deformation is developed based on finite element modeling (FEM) and artificial neural network. Firstly, a series of finite element models at selected poses are established to obtain the deformation data. Then, a force-induced deformation prediction model is established through radial basis function neural network with adaptive genetic algorithm optimization (AGA-RBF). Furthermore, a basic strategy is proposed to compensate for the predicted error through the motion commands modification. Finally, a contrast experiment is carried out to verify the feasibility and efficiency of the proposed method.

Cross-rail deformation modeling, measurement and compensation for a gantry slideway grinding machine considering thermal effects

For a large gantry slideway grinding machine, the cross-rail is the main connecting and support component, whose deflection is greatly determined by both gravity and thermal effects. To precisely analyze and compensate the cross-rail deflections, this article presents an analytical prediction model of the cross-rail deflection considering both gravity and thermal effects. The total deflection of the cross-rail in the heated state is modeled as the superposition of three parts, i.e. the gravity-induced error, the thermally-induced error and the manufacturing-induced error. The self-weight of the cross-rail and spindles causes the bending in the Z-direction and torsional deflection in the X-direction. The thermal stress caused by the temperature difference between the top and bottom surfaces leads to large thermal bending in the Z-direction. The modeling accuracy is verified by the straightness error measurement, and the corresponding errors are compensated via a compensator. After compensation, the straightness error of the cross-rail meets the requirements of ISO 4703-2001.

Modeling, online identification, and compensation control of single tendon sheath system with time-varying configuration

• The transmission models of single TSS with arbitrary route configurations are developed. • A tendon-sheath-based bending sensor is proposed for online parameter identification. • Two compensation strategies are developed to enhance the control accuracy of TSS without distal feedback. • The effectiveness is validated by trajectory tracking and frequency response experiments. Tendon sheath system (TSS) has been widely used in many applications with strict spatial limitations due to its flexibility, dexterity, and remote transmission ability. However, the inherent configuration-dependent nonlinearities between tendon and sheath seriously degrade the transmission performance and result in inaccurate force and position control. In this paper, the force and position transmission models of single TSS with arbitrary route configurations and terminal loads are developed based on the analysis of system friction and deformation. A tendon-sheath-based bending sensor is proposed for the online identification of accumulated bending angle. To enhance the accuracies of force control and position control with time-varying configuration, two control strategies are developed for the friction and deformation compensation without sensory feedback from distal end. An experimental setup of tendon sheath actuation is established to gain insights into the force and position transmission processes and evaluate the effectiveness of the developed transmission models and compensation controllers. The results of model validation experiments with sinusoidal force input show that the modeling errors of force and position transmission are less than 5% and 2.5%, respectively. Moreover, the trajectory tracking experiments and frequency response experiments are carried out, and the results demonstrate the feasibility of the proposed identification strategy and compensation controllers in improving control accuracy and ensuring control bandwidth of single TSS with time-varying bending angle.

Structural Schemes and Structural-Parametric Models of Electroelastic Actuators for Nanomechatronics Systems

The parametric structural schemes, structural-the parametric models and the transfer functions of the electroelastic actuators for the nanomechatronics systems are obtained. The transfer functions of the piezoactuator are determined under the generalized piezoelectric effect. The changes in the elastic compliance and the stiffness of the piezoactuator are found, taking into account the type of control. The decision wave equation and the structural-parametric models of the electroelastic actuators are obtained. Effects of the geometric and physical parameters of the electroelastic actuators and the external load on its static and dynamic characteristics are determined. The parameteric structural schemes for the electroelastic actuators for the nanomechatronics systems are obtained. The transfer functions are determined. For calculation of the automatic control systems for the nanometric movements with the electroelastic actuators are obtained the parametric structural schemes and the transfer functions of actuators. Static and dynamic characteristics of the electroelastic actuators are determined. The application of electroelastic actuators solves problems of the precise matching in microelectronics and nanotechnology, compensation of temperature and gravitational deformations, atmospheric turbulence by wave front correction. By solving the wave equation with allowance for the corresponding equations of the piezoelectric effect, the boundary conditions on loaded working surfaces of the electroelastic actuator, the strains along the coordinate axes, it is possible to construct the structural parametric model of the actuator. The transfer functions and the parametric structural schemes of the electroelastic actuator are obtained from the equations describing the corresponding structural parametric models and taking into account the opposed electromotive force of the electroelastic actuator for the nanomechatronics systems.

Model-based spinal deformation compensation in robot-assisted decompressive laminectomy

Decompressive laminectomy is a common operation for the treatment of lumbar spinal stenosis. A high-speed burr and piezosurgery are often used to remove the lamina to relieve compressed nerves. However, surgeons need to control the cutting margin of the lamina based on experience, and the remaining laminar thickness is difficult to quantify before image measurements. In other surgeries, robot-assisted grinding guided by navigation can make operations accurate, but the deformation of bone tissue caused by instrument interaction cannot be ignored, especially for spinal surgery. Because of the elasticity of the intervertebral disk, the spine deforms under external force, which leads to deviation from the preoperative trajectory for the robot. This paper proposes a model-based compensation method for spinal deformation during decompression operation. A torsion model and bending model are built based on traditional elastic mechanics, and then a coupling model is simplified and modified for improved robot control. The source and influence of residual error caused by the noise is analysed, and data-based estimation of the model parameters is conducted to accommodate different patients. Robot deformation is also considered in the control system, and the model inputs—the feedback force data—are processed using the adaptive Kalman filter in real time. The lumbar data are segmented for finite element analysis, which provides the input and output data with which the parameters of the model are estimated, and the simulation shows that the signal-to-noise ratio of the force sensor has a great effect on system performance.

Straintronics beyond homogeneous deformation

We present a continuum theory of graphene treating on an equal footing both homogeneous Cauchy-Born (CB) deformation, as well as the microscopic degrees of freedom associated with the two sublattices. While our theory recovers all extant results from homogeneous continuum theory, the Dirac-Weyl equation is found to be augmented by new pseudo-gauge and chiral fields fundamentally different from those that result from homogeneous deformation. We elucidate three striking electronic consequences: (i) non-CB deformations allow for the transport of valley polarized charge over arbitrarily long distances e.g. along a designed ridge; (ii) the triaxial deformations required to generate an approximately uniform magnetic field are unnecessary with non-CB deformation; and finally (iii) the vanishing of the effects of a one dimensional corrugation seen in \emph{ab-initio} calculation upon lattice relaxation are explained as a compensation of CB and non-CB deformation.