bluuebunny/crossref_metadata_2025 huggingface dataset:
Anterior Selective Lumbar Fusion Saving More Distal Fusion Segments Compared with Posterior Approach in the Treatment of Adolescent Idiopathic Scoliosis with Lenke Type 5: A Cohort Study with More Than 8‐Year Follow‐up
Authors: Wang Zhi‐wei , Shen Yuan‐qing , Wu Yan , Li Jun , Liu Zhen , Xu Jian‐kun , Chen Qi‐xin , Chen Wei‐shan , Chen Lin‐wei , Zhang Ning , Li Fang‐cai
Published: November 2021

Objective

To investigate whether anterior selective fusion (ASF) could save more distal fusion segments compared with posterior approach in the treatment of Lenke type 5 adolescent idiopathic scoliosis with long term follow‐up.

Methods

A retrospective cohort study. From 2008 to 2011, 22 AIS girls with Lenke type 5 who underwent ASF or posterior selective fusion (PSF) with more than 8‐year follow‐up, were extracted from the database. 13 girls in the ASF group had an average age of 14.3 ± 1.3 years and Risser sign of 3.3 ± 1.1; 9 PSF girls had an average age of 16.2 ± 3.6 years and Risser sign of 3.8 ± 1.5. The radiographic outcome was compared between groups preoperatively, 6‐month postoperatively, 8‐year postoperatively and at last follow‐up (>8 years).

Results

The average follow‐up duration was 8.7 ± 0.4 (ASF) and 8.8 ± 0.5 (PSF) years, respectively. There was no significant difference at baseline in age, Risser sign and preoperative curve pattern in the coronal and sagittal plane between the groups (P > 0.05). The ASF group had significantly shorter fusion segments (5.1 ± 0.6 vs. 7.0 ± 1.3) and decreased upper instrumented vertebra (UIV) (T11 ± 0.8 vs. T10 ± 0.8) than the PSF (P < 0.05); while no significant difference was found in the lower instrumented vertebra (LIV) and distal reserved segments (P > 0.05), which suggested that ASF could shorten the fusion segments by lowering UIV. The distal compensatory curve in the ASF group (9.0° ± 3.9°) was significantly larger than in the PSF group (3.3° ± 2.4°, P = 0.003), despite of no significant difference in the incidence of coronal imbalance (P > 0.05), indicating that both two approaches could obtain satisfactory correction in the coronal plane. In the sagittal plane, PSF patients had significantly larger lumbar lordosis (LL, 59.1° ± 10.5°), thoracic kyphosis (TK, 37.2° ± 13.3°) and proximal junctional angle (PJA, 13.3° ± 6.1°) at the last follow‐up than the ASF (LL: 43.4° ± 9.4°; TK: 20.7° ± 8.4°; PJA: 4.7° ± 3.4°; P < 0.05), but without significant difference in proximal junctional kyphosis (PJK) and sagittal vertical axis (SVA) (P > 0.05). After controlling for age, Risser sign, and radiographic parameters related to the primary curve pattern, shorter fusion segments and more distal reserved segments still remained significant in the ASF group with greater Risser sign (P < 0.05). No major intra‐ or post‐operative complications occurred.

Conclusions

Both ASF and PSF could obtain satisfactory coronal and sagittal correction for Lenke 5 AIS; compared with PSF, ASF could shorten the fusion segments by lowering UIV, and save more distal fusion segments only in patients with greater skeletal maturity.
Quantifying the ecosystem service of non‐native weed seed predation in traditional terraced paddy fields
Authors: Ichihara Minoru , Maruyama Keisuke , Yamashita Masayuki , Sawada Hitoshi , Inagaki Hidehiro , Asai Motoaki
Published: November 2021

Weed seed predation is an important ecosystem service in paddy areas. To conserve and sustainably utilize this service, it is necessary to quantify the seed predation and reveal the relative contributions of seed predators. In this study, we quantified the extent of postdispersal seed predation of Lolium multiflorum Lam., a non‐native invasive grass weed, on levees of terraced paddy fields located in a traditional cultural landscape (satoyama landscape) of Japan. We investigated the temporal variability in seed predation of L. multiflorum during summer after the seed shed, and estimated the total seed loss due to predation on the levees of terraced paddy fields for 2 years. Furthermore, the relative contribution of invertebrates and vertebrates to the seed predation was estimated based on exclosures. The total seed loss due to predation during 4 months (from late June to late October) was consistently high (>99%) in both years (the maximum proportion of seed predation per 2 weeks = 80.0–86.7%). The seed predators were likely to be mainly invertebrates such as crickets and ground beetles. This study revealed that the seed predation intensity was consistently high and can be an important depletion factor for the seedbanks of weeds such as L. multiflorum on the levees of terraced paddy fields. The high intensity of seed predation by invertebrates might suppress the invasion and population expansion of L. multiflorum on the levees of terraced paddy fields.
Investigation of Damage in Unidirectional Ceramic Matrix Composites Using a Cohesive-Shear-Lag Model
Authors: Yang B. , Mall S.
Published: November 2021

The present study develops a cohesive-shear-lag model to analyze the cycling stress-strain behavior of unidirectional fiber-reinforced ceramic matrix composites. The model, as a modification to a classical shear-lag model, takes into account matrix cracking, partial interfacial debonding, and partial breakage of fibers. The statistical nature of partial breakage of fibers is modeled by using a cohesive force law. The validity of the model is demonstrated by investigating stress-strain hysteresis loops of a unidirectional fiber-reinforced ceramic-glass matrix composite, SiC/1723. This example demonstrates the capability of the proposed model to characterize damage and deformation mechanisms of ceramic matrix composites under tension-tension cycling loading. The dominant progressive damage mechanism with cycling in this case is shown to be accumulation of fibers breakage, accompanied by increase in interfacial debonding and smoothening of frictional debonded interface.
High-Strain-Rate Failure of a Porous Heterogeneous Composite: Balsa Wood
Authors: Vural M. , Ravichandran G.
Published: November 2021

The compression behavior of a naturally occurring porous and heterogeneous biocomposite, balsa wood, along the grain direction is investigated at strain rates 10−3 to 104 s−1. Specimens with different densities, ranging from 55 to 380 kg/m3, were loaded by a modified Kolsky (split Hopkinson) pressure bar apparatus at varying high strain rates and by a screw-driven testing machine at quasi-static strain rates. The mechanical response of balsa wood is documented and the variation of compressive strength, crushing stress and densification strain as a function of density and strain rate is presented. Results show that characteristics of mechanical response for balsa wood are significantly affected by the strain rate and density.
Dynamic Crush Test of Subcomponent Composite Front Frame Rails
Authors: Brimhall Thomas , Mariam Hasetetsion G.
Published: November 2021

Testing of components is a usual method to evaluate structures, joining methods, and materials prior to full scale testing. Ambient temperature dynamic crush testing was performed on steel and composite sub-component front frame rails to compare the energy absorption and evaluate crush behavior. The sub-component composite frame rails were fabricated from two parts, an upper and lower, and bonded using three adhesives: Ashland polyurethane, Lord epoxy, and 3M epoxy. Prior to the dynamic test of the rails, single lap shear coupon tests were performed at ambient temperature and elevated temperature, 135°C, to evaluate relative bond strength of these adhesives. Testing was performed at elevated temperature because adhesives used for structural bonding in automotive, specifically under-hood, applications can be subjected to elevated temperatures. All three adhesives tested showed reduced bond strength at elevated temperatures. At room temperature, the Ashland urethane and Lord epoxy adhesives were observed to have comparable higher bond strength with the composite-to-composite lap shear coupons compared to the 3M epoxy. However, the crush failure mode for the composite tubes was confined to the substrate and the mean crush load was independent of the adhesive used for fabrication.

Progressive crushing of the rail specimens was observed for all specimens tested. The amount of energy absorbed and crush mode for each rail design depended on its structural and material characteristics. The steel specimen absorbed energy by localized buckling in an accordion crush mode. The composite specimens absorbed energy by fracturing the composite matrix, delamination, fracture of the reinforcement fibers, and friction between the fracture and crushing surfaces. The crushing process of the steel rail was initiated by fabricated corrugations in the rail comers at the front, or impact, end of the rail. The composite rail crush event was initiated with an aluminum plug trigger designed to cause the composite rail to split at the comers with fracture of the composite matrix and delamination of the composite plies. Glass fibers were observed to fracture primarily at the tube corners. Fiber fracture elsewhere was infrequent. Close examination of the bonded joint fracture surface showed extensive fiber tear-out indicating that the failure was in the composite, not the adhesive. Mean crush load for the steel rail was 60% higher than the average mean load for the composite rails. The peak load for the steel rail was 71% higher than the average peak load for the composite rails. Specific energy absorption (SEA) of the steel rail was calculated to be 6.34 kJ/kgm compared with an average of 10.5 kJ/kgm for the composite rails.
Optimal Design of an Inflatable Knee Bolster Using Genetic Algorithms
Authors: Fu Yan , Yang R. J. , Yeh Isheng
Published: November 2021

An inflatable knee bolster (IKB) is an inflatable airbag cushion deployed in the knee area in conjunction with the frontal airbags to reduce the potential lower-leg injuries. It is conceivable that an IKB can reduce the femur loads. However, its effects on the occupant head and chest injuries and its interaction with the other components of the occupant restraint system are unknown. The goal of this study is to evaluate the potential application of an inflatable knee bolster to improve the occupant safety performance, such as the U.S. new car assessment program (NCAP) star rating. An efficient genetic algorithm method is developed for solving this type of large-scaled, combinatorial, and discrete optimization problems. Genetic algorithm works simultaneously on a population of solution strings according to the survivor of the fitness and provides a population of solutions, which gives more flexibility for engineering implementation and produces a potential global optimal design. The results demonstrate that the genetic algorithm is a useful and applicable tool to optimize design configurations for large-scaled occupant simulation problems.
University - National Laboratory Collaboration on MEMS Design Education
Authors: Kilani Mohammad I. , Galambos Paul C. , Haik Yousef S. , Chen Ching-Jen
Published: November 2021

The paper describes the FAMU-FSU College of Engineering approach in educating graduate students in MEMS technology. The approach is based on a collaboration project between the Florida Agricultural and Mechanical University - Florida State University College of Engineering (FAMU-FSU COE) and Sandia National Laboratories (SNL). The project aims at developing a line of electrostatically and magnetically actuated surface micromachined pumps. The paper describes our experience in this collaboration program and illustrates the educational aspects of SNL MEMS design tools. The paper also describes the micropump designs developed in the first phase of the project. The pumps are being fabricated at this time. Results related to performance will be presented at a later time. However, an overview of the work to be done in the next phase is also presented.
Theoretical Analysis of the Strength of Internal Gear Drive With Zero-Tooth-Difference
Authors: Wang Shijie , Hong Guang
Published: November 2021

In this paper we apply internal gear drive pair, with zero-tooth-difference, in the coupling mechanism to connect the output shaft of reducer and the rotor of pump in the submerged-motor-driven PC pumping system for oil production. Because there are dual modifications along radial and tangential direction for the cut of gear teeth, the gear-tooth thickness will be reduced and thus the strength of the teeth will be weakened evidently. At present, there is no theoretical criteria for the strength verification suitable for such mechanism design. The new calculating formulae for contacting stress of tooth surface and bending stress of tooth-root were established in this paper just for this reason, which not only provide the strength verifying criteria for gear-tooth but can also be regarded as the theoretical basis for the design of internal gear drive mechanism with zero-tooth-difference.
Failure Mode Analysis of Rolling Element Bearings
Authors: Sehgal Rakesh , Gandhi O. P. , Angra S.
Published: November 2021

A procedure based on digraph modeling and matrix approach is suggested for failure mode analysis of rolling element bearings. A Bearing Failure Mode Digraph (BFMDj for a failure mode of the rolling element bearing is defined, which considers contributing cause events and their interrelations. The digraph is analyzed using connection and reachability matrices. A Bearing Failure Mode Connection Matrix (BFMCM) is obtained for the Bearing Failure Mode Digraph and a Bearing Failure Mode Reachability Matrix (BFMRM) is derived from it, which helps in identifying the stage relationship among various cause events, and evaluates the importance of the cause events for the failure mode. It therefore provides directions for appropriate action for minimization of the failure mode thus leading to improvement in reliability of the rolling element bearing. The methodology is developed considering the failure mode - bearing seizure and is illustrated by considering the failure mode - excessive noise.
Intuitive Intelligent Sensor Fusion With Highly Autonomous Sensors
Authors: Yuan Jane Xiaojing , Figueroa Fernando
Published: November 2021

The objective of sensor fusion is to synergistically combine different sources of sensory information into one representational format to provide more complete and precise interpretation of the system. A generic sensor fusion framework based on a highly autonomous sensor (HAS) model is presented. The framework provides freedom to choose different data fusion methods and combine them together to achieve better performance. In the context of HAS’s, this paper describes a hierarchical decentralized sensor-fusion approach based on a qualitative theory to interpret measurements, and on qualitative procedures to reason and make decisions based on the measurement interpretations. In this manner, heuristic fusion methods are applied at a high-qualitative level as well as at a numerical level when necessary. This approach implements intuitive (effective) methods to monitor, diagnose, and compensate processes/systems and their sensors.
Development of a System for Monitoring Tool Wear Using Artificial Intelligence Techniques
Authors: Silva Rui. G. , Wilcox Steven J. , Reuben Robert L.
Published: November 2021

The main objective of the work reported here was to develop an intelligent condition monitoring system able to detect when a cutting tool was worn out. To accomplish this objective the use of a hybrid intelligent system, based on an expert system and two neural networks was investigated. The neural networks were employed to process data from sensors and the classifications made by the neural networks were combined with information from the knowledge base to obtain an estimate of the wear state of the tool by the expert system.

The novelty of this work is mainly associated with the configuration of the developed system. The combination of sensor-based information and inference rules, results in an on-line system that can learn from experience and update the knowledge base pertaining to information associated with different cutting conditions. The neural networks resolved the problem of interpreting the complex sensor inputs while the expert system, by keeping track of previous success, estimated which of the two neural networks was more reliable. Mis-classifications were filtered out through the use of a rough but approximate estimator, Taylor’s tool life model. The system’s modular structure would make it easy to update as required for different machines and/or processes. The use of Taylor’s tool life model, although weak as a tool life estimator, proved to be crucial in achieving higher performance levels. The application of the Self Organizing Map to tool wear monitoring proved to be slightly more reliable then the Adaptive Resonance Theory neural network although overall the system made reliable, accurate estimates of the tool wear.
Optimal Path Planning and Torque Minimization via Genetic Algorithm Applied to Cooperating Robotic Manipulators
Authors: Garg Devendra P. , Kumar Manish
Published: November 2021

This paper presents the formulation and application of a genetic algorithm based strategy for the determination of an optimal trajectory for a multiple robotic configuration. First, the motivation for multiple robot control and the current state-of-art in the field of cooperating robots are briefly given. This is followed by a discussion of energy minimization techniques in the context of robotics, and finally, the principles of using genetic algorithms as an optimization tool are included. The initial and final position of the end effector are specified. Two cases, one of a single manipulator, and the other of two cooperating manipulators carrying a common payload illustrate the approach proposed. The genetic algorithm identifies the optimal trajectory based on minimum joint torque requirements. The minimization of a suitably defined performance index involving joint torques implies that the trajectory thus obtained requires the least amount of torque.
A First Principle Engine Model for Up-Front Design: Bearing Models and Example Results
Authors: Ma Zheng-Dong , Perkins N. C.
Published: November 2021

The design of new engine concepts requires an engineering tool that can quickly estimate noise, vibration and durability metrics at the very onset of the engine design cycle. In (Ma et al., 2000), we presented an engine modeling template (EMT) to support up-front engine design. The engine models generated from the EMT use the minimum set of generalized coordinates to represent engine dynamics. This is achieved by employing a pre-selected set of relative coordinates. The resulting engine model is cast as a (minimum) set of ordinary differential equations in lieu of the differential-algebraic equations that result from using commercial multibody dynamics codes. The resulting models then enjoy greater computational efficiency.

In (Ma et al., 2000), we formulate the equations of motion for the engine and its major components. The objective of this paper is to review the numerical results obtained from sample engine designs and to discuss several tradeoffs between model accuracy and efficiency. Attention focuses on the trade-offs resulting from several bearing models, including linear and nonlinear spring-damper bearing models, and hydrodynamic bearing models based on the Reynolds equation. Results computed using these bearing models are critically compared.
Further Results on Adaptive Compression Braking Control for Heavy-Duty Vehicles
Authors: Druzhinina Maria , Stefanopoulou Anna , Moklegaard Lasse
Published: November 2021

In this paper we present further results on adaptive compression braking control for a Class-8 heavy duty vehicle with the objective to achieve good and consistent vehicle speed tracking performance during large variation in vehicle mass (payload) and road grade. In our previous work the adaptive controller performance was tested in simulations on a reduced order nonlinear vehicle/engine model. In this paper, we include several modifications to deal with actuator saturation and unmodeled dynamics. The final version of the controller is successfully evaluated on a high order crankangle model. Good tracking performance during braking as well as estimation properties of the algorithm for vehicle mass and road grade are confirmed. Moreover, the stability and response properties of the overall scheme are rigorously analyzed.
Quiet Seating Control Design of an Electromagnetic Engine Valve Actuator
Authors: Tai Chun , Tsao Tsu-Chin
Published: November 2021

The control of engine valve seating velocity has been identified to be crucial for the application of an electromagnetic valve (EMV) actuator for camless variable valve timing engine operations. Analysis shows that the EMV actuator becomes unstable when the engine valve is hold steady close to the seating position. As such, valve motion under open loop control is sensitive to disturbances and suffers poor repeatability. Therefore, closed-loop control is required to achieve desirable quiet-seating performance consistently.

A linear plant model was constructed based on a gray-box approach that combines mathematical modeling and system identification. A controller was developed with H∞ loop-shaping method to stabilize the EMV actuator. The performance of this control design is demonstrated by experimental results. “Seating velocity” and “seating tail-length” are defined and used to evaluate the control system performance.
Analytical Traction and Propulsion Analysis
Authors: Lieh Junghsen
Published: November 2021

Conventional approach for vehicle traction and propulsion analysis used spreadsheets. This is inconvenient if one intends to vary a parameter, and it is even more difficult when multiple parameters are evaluated at the design phase. In this paper, it is intended to formulate two nonlinear differential equations representing road load and power consumption. By expanding inertia force, air drag, rolling resistance, gravitational force and tire tractive force, the equations can be simplified as the function of velocity v, i.e., s 1 v ˙ = s 2 - s 3 v 2 and m v ˙ = - r 1 v 3 - r 2 v + r 3 v , respectively. With these two equations, it allows engineers to use either numerical or analytical method to study key parameters at the design phase.

To demonstrate the effectiveness of these equations, Wright State’s electric car model is used. The results for front-wheel drive (FWD), rear-wheel drive (RWD) and four-wheel drive (4WD) cases are presented.
First Order Analysis for Automotive Designs
Authors: Kojima Yoshio , Nishigaki Hidekazu , Sugiura Hideki , Nishiwaki Shinji , Kikuchi Noboru
Published: November 2021

In current automotive development, innovations to reduce development time and to use a virtual prototype have been numerous and progressive. Computer Aided Engineering (CAE) has played an important role in these innovations. CAE numerically estimates the performance of automobiles and proposes alternative ideas that lead to higher performance without building physical prototypes. However, current CAE can not usually be used at the initial design phase due to their difficult, and complex functions and characteristics. In this paper, we propose a new type of CAE, First Order Analysis (FOA). The basic ideas include: (1) graphic interfaces using Microsoft /Excel to achieve a product-oriented analysis, (2) use of mechanics of materials to provide useful information regarding structural mechanisms, and (3) a topology optimization method using function oriented elements. Also, some prototype software is presented to confirm the applicability of method presented here to the automotive designs.
Slip-Based Tire-Road Friction Estimation During Braking
Authors: Müller Steffen , Uchanski Michael , Hedrick Karl
Published: November 2021

We develop a slip-based method that estimates tire-road friction during braking using data from standard ABS wheel speed sensors and a brake pressure sensor. During a braking maneuver, normalized traction force, μ, vs. slip data is collected and the slope of this μ vs. slip line is used to estimate the road friction. Results from field tests of the algorithm are presented.
A Dynamic Tire Friction Model for Combined Longitudinal and Lateral Motion
Authors: Deur Joško , Asgari Jahan , Hrovat Davor
Published: November 2021

A dynamic tire friction model based on the comprehensive LuGre friction model has been proposed recently for the case of pure longitudinal motion. An extension of the model for combined longitudinal and lateral motion, including calculation of the self aligning torque, is presented in this paper. The extended model is derived for both uniform and non-uniform normal pressure distributions. The model steady-state behavior is validated with respect to Pacejka static tire model, which served as an “ideal” benchmark. Possible further improvements of the proposed model are also addressed.
A Dynamic-Programming-Styled Algorithm for a Class of Multi-Agent Optimal Task Assignment
Authors: Yang Guang , Kapila Vikram , Vaidyanathan Ravi
Published: November 2021

In this paper, we use a dynamic programming formulation to address a class of multi-agent task assignment problems that arise in the study of fuel optimal control of multiple agents. The fuel optimal multi-agent control is highly relevant to multiple spacecraft formation reconfiguration, an area of intense current research activity. Based on the recurrence relation derived from the celebrated principle of optimality, we develop an algorithm with a distributed computational architecture for the global optimal task assignment. In addition, we propose a communication protocol to facilitate decentralized decision making among agents. Illustrative studies are included to demonstrate the efficacy of the proposed multi-agent optimal task assignment algorithm.
Time Delay Modeling and Sample Time Selection for Networked Control Systems
Authors: Lian Feng-Li , Moyne James , Tilbury Dawn
Published: November 2021

This paper discusses the impact of network architecture on control performance in a class of distributed control systems called Networked Control Systems (NCS), and provides design considerations related to control quality of performance (QoP) as well as network quality of service (QoS). The integrated network-control system changes the characteristics of time delays between application devices. This study first identifies several key components of the time delay through an analysis of network protocols and control dynamics. The analysis of network and control parameters is used to determine an acceptable working range of sampling periods in an NCS. A network-control simulator and an experimental networked machine tool have been developed to help validate and demonstrate the performance analysis results, and identify the special performance characteristics in an NCS. These performance characteristics are useful guidelines for choosing the network and control parameters when designing an NCS.
Actuator Placement and Control Efficiency of Paraboloidal Shell Structures
Authors: Tzou H. S. , Ding J. H.
Published: November 2021

Paraboloidal shells of revolution are commonly used in communication systems, precision opto-mechanical systems and aerospace structures. This study is to investigate the precision distributed control effectiveness of paraboloidal shells laminated with segmented actuator patches. Mathematical models of the paraboloidal shells laminated with distributed actuator layers subjected to mechanical, temperature, and control forces are presented first, followed by formulations of distributed control forces with their contributing meridional/circumferential membrane and bending control components using an assumed mode shape function. Studies of actuator placements, control forces, contributing components, and normalized control authorities of paraboloidal shells are carried out. These forces and membrane/bending components basically exhibit distinct modal characteristics influenced by shell geometries and other design parameters. Analyses suggest that the membrane contributed components dominate the overall control effect. Locations with larger normalized forces indicate the areas with high control efficiencies, i.e., larger induced control force per unit actuator area. With limited actuators, placing actuators at those locations would lead to the maximal control effects.
Alternative Analytical Mean-Square Calculations for Dynamic Systems Subject to Random Inputs
Authors: Redfield Robin C.
Published: November 2021

Output variables of linear dynamic systems subject to random inputs are often quantified by mean square calculations. Computationally, these involve integration of the frequency response magnitude squared over all frequency. Numerically, this is an easy task and analytically, methods exist to find mean square values as functions of transfer function (frequency response) coefficients. This paper develops further analytical techniques to calculate mean-square values as functions of system pole-zero locations and as functions of eigenproperties and system matrices. These other analytical representations may provide paths to further insight into dynamic system response and optimal design/tuning of dynamic systems.
Optimal Actuator/Sensor Placement for Control of Combustion Instabilities
Authors: Al-Masoud Nidal , Singh Tarunraj
Published: November 2021

In this paper, a methodology is proposed for determination of optimal actuator and sensor locations for the control of combustion instabilities. The proposed approach relies on certain quantitative measures of degree of controllability and observability based on the controllability and observability grammians. These criteria are arrived at by considering the energies of system’s inputs and outputs. The optimality criteria for sensor and actuator locations provide a balance between the importance of the lower order and the higher order modes. It is assumed that the control input is provided by a finite number of point actuators, and the instantaneous conditions in the chamber are monitored, in general, by multiple sensors.
Dynamic Redesign of a Flow Control Servo-Valve Using a Pressure Control Pilot
Authors: Li Perry Y.
Published: November 2021

In this paper, the dynamic performance of an unconventional two-spool flow control servo valve using a pressure control pilot is analyzed. Such valves are less expensive than typical servo-valves but also tend to be limited in their dynamic performance. Based on a previously developed eight state nonlinear model, we develop a simplified linear model which is able to capture the essential dynamics of the valve. Using root locus analysis method, the limitation in dynamic performance is shown to be due to a “zero” introduced by the structure of the interconnection of the subsystems. Design parameters that move the “zero” further to the left half plane, and do not adversely affect other steady state criteria are identified. The effectiveness of these parameters to improve the dynamic performance is demonstrated.
Modeling and Multivariable Control of an Earthmoving Vehicle Powertrain
Authors: Zhang Rong , Prasetiawan Eko A. , Alleyne Andrew G.
Published: November 2021

Coordination of the power distribution in a Multi-Input Multi-Output (MIMO) electrohydraulic transmission is investigated for the case of an earthmoving vehicle powertrain. A generalized model of a representative system is presented along with the development of both H2 and H∞ MIMO controller designs. The controllers are developed based on a linearized model of the system about some nominal operating point Multiple inputs are coordinated to control multiple load outputs simultaneously. Since typical MIMO electrohydraulic transmission systems have significant nonlinear dynamics that vary with system operating conditions, a robust controller design is paramount The increased robustness of the H∞ controller over the H2 scheme is demonstrated qualitatively in the time domain through both disturbance rejection and trajectory tracking comparisons. A frequency domain criterion quantitatively provides quantifiable comparisons between the two methods. Hardware-in-the-Loop experiments validate the modeling and control performance on an Earthmoving Vehicle Powertrain Simulator (EVPS).
Washing Machine Health Diagnostics Through Information Synthesis
Authors: Brown J. , Franchek M. A.
Published: November 2021

Presented in this paper is a model-based method for assessing suspension and motor health of washing machines. The diagnosis of the suspension and motor health is achieved by processing the measured dynamics of the washtub. In particular, an online adapted lumped parameter model of the washtub is used to estimate key suspension and motor parameters. These parameters are identified from the measured displacement of the washtub due to a motor pulse input prior to the beginning of the wash cycle. Comparing the estimated values to design values assesses both suspension and motor health. Included are simulation results to validate the parameter estimation process.
Fault Detection for Nonlinear Systems
Authors: Fretheim Tor , Shoureshi Rahmat , Vincent Tyrone
Published: November 2021

A new fault detection and isolation scheme has been developed to enable automatic detection of faulty conditions in linear or non-linear systems. The focus of this paper is on the development of a general, and feasible method for nonlinear system fault detection which can be easily implemented on input/output models. The method proposed here is different in that the neural network is used to model the process dynamics, while a dead-beat observer is implemented by solving a set of coupled nonlinear equations. This enables the introduction of constraints into the problem that can improve the power of the fault detection techniques.
Implementation of Observer-Corrector Feedback for Motion Control of Direct-Drive Robotic Manipulator
Authors: Hosek Martin , Moura Jairo T. , Elmali Hakan
Published: November 2021

Observer-corrector feedback is a control strategy which reduces destabilizing effects of unmodeled higher-order dynamics (e.g., structural resonances of a robotic manipulator) found in many systems subject to control. The fundamental idea is to synthesize a substitute feedback signal in order to extract dominant dynamic components (e.g., rigid body motion of a robotic manipulator) from the output of the controlled system. A band-limited state observer complemented by a low-pass filter corrector are employed for this purpose. The synthetic signal is used as a controller input, effectively eliminating destabilizing effects of unmodeled dynamics of the controlled system. In the presented work, the observer-corrector feedback mechanism is implemented for motion control of a three-axis direct-drive robotic manipulator for automated pick-place operations in semiconductor manufacturing applications. A detailed technical description of the robotic manipulator is provided, a control system with the observer-corrector arrangement is designed, and selected results of laboratory tests are presented. The tests demonstrate that the observer-corrector feedback mechanism leads to improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to usual control methods.
Flexible Link End-Point Control Based on Exact Dynamic Inversion: Experimental Results
Authors: Piazzi Aurelio , Visioli Antonio
Published: November 2021

In this paper we present a new method for the point-to-point motion control of the end-point of a single flexible link manipulator. The technique is based on an exact system inversion procedure, that allows to define a suitable motion law for the hub in order to reduce the residual vibration at the end of the tip motion. Thus, the end-point control is actually performed in open-loop, therefore avoiding the use of a sensor to measure the actual tip position. Experimental results demonstrate the effectiveness of the approach and that the overall control system is inherently robust to modelling errors.
Adaptive Control Strategies for Coordination and Control of Mutliple Robots
Authors: Nagchaudhuri Abhijit , Garg Devendra P.
Published: November 2021

The uncertainty associated with the robot dynamics for performing contact tasks have often necessitated the use of adaptive algorithms. This paper investigates the use of adaptive control and impedance control for a difficult contact task involving multiple robots handling a common heavy object. Simulations are performed using various trajectories in the Cartesian space, and uncertainties associated with payload as well as dynamic characteristics of the robots are considered. Three different trajectories are generated for motion of the object centroid between the same two locations in the Cartesian space. The simulations establish that the adaptive strategies proposed are not only robust to uncertainties in dynamic parameters and load characteristics but also with regard to speed of motion and trajectory alterations that may be necessary for considerations involving path planning and obstacle avoidance.
A Fault Accommodating Control of an Autonomous Underwater Vehicle Under Thruster Redundancy and Saturation
Authors: Podder Tarun Kanti , Sarkar Nilanjan
Published: November 2021

An approach to the allocation of thruster forces of an autonomous underwater vehicle (AUV) is investigated in this paper. Generally, the number of thrusters in an AUV is more than what is minimally required to produce the desired motion. This paper presents a framework that exploits the excess number of thrusters to accommodate thruster faults during operation. First, a redundancy resolution scheme is presented that takes into account the presence of excess number of thrusters along with any thruster faults, and determines the reference thruster forces to produce the desired motion. This framework is then extended to incorporate a dynamic state feedback technique to generate reference thruster forces that are within the saturation limit of each thruster. These reference thruster forces are utilized in the thruster controller to generate the required motion. This approach resolves the thruster redundancy in the Cartesian space and allows the AUV to track the task-space trajectories with asymptotic reduction of the task-space errors. Results from computer simulations are provided to demonstrate the viability of the proposed scheme.
Observer-Corrector Control Strategy for Robotic Manipulators With Unmodeled Dynamics
Authors: Hosek Martin
Published: November 2021

A control strategy is presented which reduces destabilizing effects of unmodeled higher-order dynamics found in many systems subject to control. These effects are major limiting factors of conventional controllers, especially for high-performance machinery, such as precision machine tools and robotic manipulators. In the proposed strategy, a substitute feedback signal is synthesized in order to extract dominant dynamic components (e.g., rigid body motion of a flexible robotic manipulator) from the output of the controlled system. A unique arrangement of a band-limited state observer and a low-pass filter corrector is employed for this purpose. The synthetic signal is used as a controller input, effectively eliminating destabilizing effects of unmodeled dynamics of the controlled system. A simulation example demonstrates that the strategy results in improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to conventional methods adopted currently in engineering practice.
PDE Control of a Flexible Two-Link Manipulator
Authors: Zhang X. , Xu W. , Nair S. S. , Chellaboina V.
Published: November 2021

A stable strain feedback control design is proposed for a flexible two-link manipulator using a model with partial differential equations directly. Stability is established using a Lyapunov-based design.
A Fuzzy Controller for Tentacle Cooperative Robots
Authors: Ivanescu Mircea , Bizdoaca Nicu , Cojocaru Dorian , Popescu Nirvana , Popescu Decebal
Published: November 2021

A fuzzy system and the control algorithms are proposed to solve the control multi-chain robotic system formed by tentacle manipulators grasping a commune object with hard contact points. The control system contains two parts: the first component is a conventional controller, which implements a control strategy based on the Lyapunov stability, and the second is an adaptive fuzzy controller which adjusts the control parameters by the output of the first level controller. The stability and robustness is investigated and the fuzzy rules are established The fuzzy controller was developed using Matlab and Simulink software. Simulation results are presented and discussed.
An Active Radial Countercurrent Heat Sink Driven by a Synthetic Jet Actuator
Authors: Vukasinovic Jelena , Glezer Ari
Published: November 2021

The performance of a low-profile radial countercurrent heat sink driven by an integrated synthetic jet actuator is investigated experimentally. A packaged thermal test die is cooled using an array of synthetic jets normally impinging on the extended surface. A power dissipation of 50 W is accomplished at the nominal case temperature of Tc = 70 °C.

The heat sink design is driven by the flow and heat transfer analysis of normal jet impingement in a confined flow geometry consisting of two parallel circular plates having a diameter that is typically an order of magnitude larger than the spacing between the plates. The velocity and temperature distributions are measured using particle image velocimetry and arrays of thermocouple sensors. A jet actuator is integrated into one of the plates and cools a test heater attached to the opposite surface. The jet draws its makeup air from ambient, impinges on the heater, and ultimately rejects the heat to ambient. This introduces a radial countercurrent flow in the gap between the plates that includes a layer of hot air dispensed along the top plate and a layer of cooler ambient air entrained along the jet exit plane. When the jet is activated the heater temperature drops substantially. Although the global heat transfer coefficient decreases with decreasing gap height, flow pathlines show that the jet can still entrain cool air from ambient and effect substantial cooling even when the spacing between the plates is of the order of the jet orifice diameter.
Thermal Analysis of EPAS Power Module
Authors: Farhi Ram
Published: November 2021

The continuous improvement of robust design for reliability is possible by the implementation of Finite Element Methods (FEM). Thermal response of a chip-and-wire power module was studied to verify and optimize the design. The power module drives a three-phase Brushless DC motor in an Electric Power Assisted Steering (EPAS) system. It has a power output of ∼1.5kW with a peak current of 125A and with thermal efficiency of 86%. The three-phase inverter is built with 12 dies (2 parallel FETs per switch), and it is constructed on an Insulated Metal Substrate (IMS) and copper lead frame.

The FEA model was verified experimentally using a Forward Looking Infra Red (FLIR) system and a threshold voltage measurement for the junction temperatures. Experimental and FEA results show the peak junction temperature is less than 130°C and the thermal resistance is 1.2C/W. In addition to design changes and refinement of process prior to fabrication, the FEA approach enabled the study of competing design approaches without sacrificing valuable time.
Characterization of Strain Rate-Dependent Behavior of 63Sn-37Pb Solder Using Split Hopkinson Torsional Bars (SHTB)
Authors: Lee Shi-Wei Ricky , Dai Lan Hong
Published: November 2021

The present study is aimed at the experimental characterization of strain-rate dependent behaviour of solder materials under impulsive shear loading. In order to achieve this objective, a unique testing technique, namely, split Hopkinson torsion bar (SHTB) is employed. The solder material under investigation is 63Sn-37Pb. The experimental results indicate that the shear behavior of the solder joint is very sensitive to the strain rate and the dynamic shear strength of the solder joint is much higher than the static one.
Reliability Analysis on the Chaos Induced by the Effect of the Transient Temperature Variation of a Printed Wiring Board
Authors: He Xiaoling , Fulton Robert
Published: November 2021

The transient response of a printed wiring board (PWB) under mechanical and thermal loading is analyzed. The thermal load is caused by the time-dependent temperature variation of the PWB. Analytical solution is obtained for the equation of motion in nonlinear dynamics analysis. Numerical results showed that the response is in chaotic behavior under harmonic excitation due to the transient thermal effect. PWB response is characterized with respect to the thermal and mechanical load effect in both phase diagram and temporal oscillation.
Evaluation of Secondary Flow Between Rotating Concentric Spheres Using a Perturbation Method
Authors: Corral R. L. , Pérez A. , Márquez A.
Published: November 2021

A new approach to evaluate the Newtonian flow between concentric rotating spheres is introduced in this paper. A general analytic solution to the problem is deduced using a perturbation method that takes into account the primary and secondary flows produced between the spheres. In order to exemplify the results of the previous analysis, six particular cases were studied. The results show that under certain circumstances the secondary flow is no negligible, as is usually considered, but it is comparable to the value of the primary one.
Rayleigh-Taylor Instability of a Shock Accelerated Gas Water Interface
Authors: Wang Xiao-Liang , Itoh Motoyuki
Published: November 2021

Rayleigh-Taylor instability at a gas-water interface has been investigated experimentally. Such instability was produced by accelerating a water column down a vertical circular tube employing shock wave impact. Accelerations from 50 to 100 times gravitational acceleration with fluid depths from 125 to 250 mm were studied. The resulting instability from small amplitude random perturbations was recorded and later analyzed using high-speed video images. Cavity formation was observed in the middle of the gas-water interface soon after the shock wave impact; bubbles and spikes then developed across the rest of the interfacial plane. Measurements of the growth coefficient of the bubbles and spikes show that they are nearly constant over different runs.
GenIDLEST: A Scalable Parallel Computational Tool for Simulating Complex Turbulent Flows
Authors: Tafti D. K.
Published: November 2021

The paper describes the framework, features, capabilities, and example applications of GenIDLEST, a computational tool for the time-dependent simulation of turbulent flows in complex geometries. Preliminary work in coupling GenIDLEST with GRID enabled software for distributed computing, data archiving, and visualization is also described.
Analysis of Centrifugal Pump Performing Under Two-Phase Flow Using Bleeding System
Authors: Zaher M. A.
Published: November 2021

A one dimensional two fluid model is used to study the performance of a centrifugal pump. Pumping of two-phase products in oil/geothermal industry offered a special multiphase pump. Test with different suction void fraction was used to predict the two-phase pump head data for two scales of pumps. With the new arrangement of bleeding and correct impeller design, a radical solution is offered to handle a multiphase flow. The physical mechanism responsible for transporting multiphase flow on efficiency, specific energy requirement and flow rate were also investigated.