bluuebunny/crossref_metadata_2025 huggingface dataset:
Employee Voice and the Communication of Dissent in an Organisational Setting in Malaysia: A Case Study
Authors: Su Yee Lee , Shanti C Sandaran, , Abd Razak Siti Suraya
Published: November 2018

The purpose of this study is to look at employee voice and in particular, how dissent is expressed in an organisation in Malaysia. The study draws upon current theories on employee voice, dissent and whistle-blowing to report on the findings of a preliminary study that used the qualitative approach by analysing semi-structured interviews. Six members of staff took part in the study. Fundamental information contained in the interview questions included communication style, management style and the organisational culture that would encourage employee voice and freedom of speech within the organisation. The preliminary findings show that the staffs are restrictive in expressing dissent to the top management. This highlights the lack of a culture for employees to express dissatisfaction at work to higher authorities due to limited openness of the top management, which results in a low level of articulated dissent. Possible reasons include the unavailability of an employee voice mechanism within the organisation including the legal support and protection where proper channels for employees to express dissent are not in practice. This study highlights the importance of employee voice within an organisation and that proper mechanisms should be in place as a sign of respect and appreciation of employee voice at the workplace.
Lecturers’ Perceptions of the benefits of Using Humour in Classroom
Authors: Yusob Khairul Firhan , Nikman Khairunisa , Jelani Ahmad Nazri , Abu Hassan Nor Asni Syahriza
Published: November 2018

Of all topics concerning classroom instruction, the use of humour has received the least attention. While some lecturers believe that using humour creates a fun and lively classroom, others may experience different situations which hamper them from using it. Hence, this paper aims to look at the lecturers’ perception of the benefits of using humour as a teaching strategy and the relationship between socio-psychological and educational benefits which students gain from humour. This study was carried out in a Malaysian public university which regards English as a medium of instruction. 60 respondents participated in this study. The findings showed lecturers considered humour as socio-psychologically and educationally beneficial for students and there was a correlation between socio-psychological and educational benefits of using humour in the classroom.
Receptive Vocabulary Levels of Malaysian University Students
Authors: Lateh Nor Hazwani Munirah , Shamsudin Sarimah , Abdul Raof Abdul Halim
Published: November 2018

Acquiring adequate vocabulary knowledge is necessary for English language learners in order to be able to function effectively using the language. The study investigated the English language receptive vocabulary knowledge among Malaysian undergraduates in terms of word levels. The Vocabulary Levels Test (VLT) by Schmitt et al., (2001) was employed in order to assess the students’ receptive vocabulary knowledge at five different word levels. The result reveals majority of the students are weak in terms of their receptive vocabulary knowledge and most of them failed to reach the mastery level for all the five word levels; 40 (57%) of the students do not master the 2000 word level, 58 (83%) of the students do not master the 3000 word level, 65 (93%) of the students do not master the 5000 word level, 70 (100%) of the students do not master the 10000 word level and 65 (93%) of the students do not master the academic word level. The findings were useful insights on the English language receptive vocabulary knowledge among Malaysian university students in terms of word levels.
Static Watson-Crick regular grammar
Authors: Abdul Rahman Aqilahfarhana , Fong Wan Heng , Sarmin Nor Haniza , Turaev Sherzod , Mohamad Zulkufli Nurul Liyana
Published: November 2018

DNA computing, or more generally, molecular computing, is a recent development at the interface of computer science and molecular biology. In DNA computing, many computational models have been proposed in the framework of formal language theory and automata such as Watson-Crick grammars and sticker systems. A Watson-Crick grammar is a grammar model that generates double stranded strings, whereas a sticker system is a DNA computing model of the ligation and annealing operations over DNA strands using the Watson-Crick complementarity to form a complete double stranded DNA sequence. Most of the proposed DNA computing models make use of this concept, including the Watson-Crick grammars and sticker systems. Watson-Crick grammars and their variants can be explored using formal language theory which allows the development of new concepts of Watson-Crick grammars.  In this research, a new variant of Watson-Crick grammar called a static Watson-Crick regular grammar is introduced as an analytical counterpart of sticker systems. The computation of a sticker system starts from a given set of incomplete double stranded sequence to form a complete double stranded sequence. Here, a static Watson-Crick regular grammar differs from a dynamic Watson-Crick regular grammar in generating double stranded strings: the latter grammar produces each strand string “independently” and only check for the Watson-Crick complementarity of a generated complete double stranded string at the end, while the former grammar generates both strand strings “dependently”, i.e., checking for the Watson-Crick complementarity for each complete substring. In this paper, computational properties of static Watson-Crick regular grammars are investigated to correlate with the Chomsky hierarchy and hierarchy of the families of dynamic Watson-Crick regular languages. The relationship between families of languages generated by static Watson-Crick regular grammars with several variants of sticker systems, Watson-Crick regular grammars and Chomsky grammars are presented by showing the hierarchy.
Effect of heating rates on the microstructure and gas permeation properties of carbon membranes
Authors: Sazali Norazlianie , Wan Salleh Wan Norharyati , Ismail Ahmad Fauzi , Kadirgama Kumaran , Moslan Mohamad Shahrizan , Che Othman Faten Ermala , Ismail Nor Hafiza , Samykano Mahendran , Harun Zawati
Published: November 2018

High performance tubular carbon membrane (TCM’s) for CO2 separation were prepared by controlling the carbonization heating rates in range of 1-7 oC/min carbonized at 800 oC under Argon environment. A single permeation apparatus was used to determine the gas permeation properties of the membrane at room temperature. Fine turning of the carbonization condition was necessary to obtain the desired permeation properties. The preparation of PI/NCC-based TCM at low heating rate caused the gas permeance for the examined gas N2 and CO2 decreased whereas the selectivity of CO2/N2 increased. It was also identified that the gas permeation properties of the resultant TCM and its structure was highly affected by the heating rate. The best carbonization heating rate was found at 3oC/min for the fabrication of TCM derived via polymer blending of PI/NCC for CO2/N2 separation.
Preliminary study on lipid extraction from Nannochloropsis salina using supercritical carbon dioxide method
Authors: Zainan Nur Hidayah , Che Yunus Mohd Azizi , Harun Razif
Published: November 2018

The issues involved with conventional lipid extraction methods, such as the usage of toxic solvents and accumulation of chemical waste, has motivated researchers to find an alternative approach to the extraction technology. One of the alternatives is via the Supercritical Carbon Dioxide (SC-CO2) method. This extraction method is considered as green as it provides a clean, selective and efficient process. Although the SC-CO2  method has been successfully used to extract lipids from microalgae, there are still some issues related to sample preparation and process parameters that need to be resolved. Therefore, this study investigates the effect of adding a modifier (ethanol) and using different types of holders (cotton and steam bun cloth) has on the yield of lipid from Nannochloropsis salina. The usage of a holder is required during the process due to the fine particles of the microalgae which have the potential to clog the instrument used. The SC-CO2 extraction without the modifier was conducted for 4 hours at 60°C, 30 MPa and CO2 flow rate of 4 ml/min, while the extraction with the modifier was conducted using 3.8 ml/min CO2 and 0.2 ml/min ethanol. It was found that the highest lipid yield of 0.16 g lipid / g dried microalgae was achieved using cotton cloth as a holder with the addition of the modifier. Lower amount of lipids were obtained when using the Soxhlet method (0.08 g lipid / g dried microalgae) and SC-CO2 without modification (0.02 g lipid / g dried microalgae). These preliminary findings show that the SC-CO2 process requires modifications to enhance the lipids yield from microalgae.
GABAB receptors modulate Ca2+ but not G protein‐gated inwardly rectifying K+ channels in cerebrospinal‐fluid contacting neurones of mouse brainstem
Authors: Jurčić Nina , Er‐Raoui Ghizlane , Airault Coraline , Trouslard Jérôme , Wanaverbecq Nicolas , Seddik Riad
Published: November 2018

Key points

Medullo‐spinal CSF contacting neurones (CSF‐cNs) located around the central canal are conserved in all vertebrates and suggested to be a novel sensory system intrinsic to the CNS.

CSF‐cNs receive GABAergic inhibitory synaptic inputs involving ionotropic GABAA receptors, but the contribution of metabotropic GABAB receptors (GABAB‐Rs) has not yet been studied.

Here, we indicate that CSF‐cNs express functional GABAB‐Rs that inhibit postsynaptic calcium channels but fail to activate inhibitory potassium channel of the Kir3‐type.

We further show that GABAB‐Rs localise presynaptically on GABAergic and glutamatergic synaptic inputs contacting CSF‐cNs, where they inhibit the release of GABA and glutamate.

Our data are the first to address the function of GABAB‐Rs in CSF‐cNs and show that on the presynaptic side they exert a classical synaptic modulation whereas at the postsynaptic level they have an atypical action by modulating calcium signalling without inducing potassium‐dependent inhibition.

Medullo‐spinal neurones that contact the cerebrospinal fluid (CSF‐cNs) are a population of evolutionary conserved cells located around the central canal. CSF‐cN activity has been shown to be regulated by inhibitory synaptic inputs involving ionotropic GABAA receptors, but the contribution of the G‐protein coupled GABAB receptors has not yet been studied. Here, we used a combination of immunofluorescence, electrophysiology and calcium imaging to investigate the expression and function of GABAB‐Rs in CSF‐cNs of the mouse brainstem. We found that CSF‐cNs express GABAB‐Rs, but their selective activation failed to induce G protein‐coupled inwardly rectifying potassium (GIRK) currents. Instead, CSF‐cNs express primarily N‐type voltage‐gated calcium (CaV2.2) channels, and GABAB‐Rs recruit Gβγ subunits to inhibit CaV channel activity induced by membrane voltage steps or under physiological conditions by action potentials. Moreover, using electrical stimulation, we indicate that GABAergic inhibitory (IPSCs) and excitatory glutamatergic (EPSCs) synaptic currents can be evoked in CSF‐cNs showing that mammalian CSF‐cNs are also under excitatory control by glutamatergic synaptic inputs. We further demonstrate that baclofen reversibly reduced the amplitudes of both IPSCs and EPSCs evoked in CSF‐cNs through a presynaptic mechanism of regulation. In summary, these results are the first to demonstrate the existence of functional postsynaptic GABAB‐Rs in medullar CSF‐cNs, as well as presynaptic GABAB auto‐ and heteroreceptors regulating the release of GABA and glutamate. Remarkably, postsynaptic GABAB‐Rs associate with CaV but not GIRK channels, indicating that GABAB‐Rs function as a calcium signalling modulator without GIRK‐dependent inhibition in CSF‐cNs.
Theoretical and Finite Element Analysis of Residual Stress Field for Different Geometrical Features After Abrasive Waterjet Peening
Authors: Zhang Meng , He Zhanshu , Zhang Yuanxi , Wang Xingdong , Zhao Shusen , Fu Ting , Chen Lei
Published: November 2018

Abrasive waterjet (AWJ) peening can be used for metal surface strengthening by introducing near-surface plastic strain and compressive residual stress. The present studies seldom focus on residual stress by AWJ peening of targets with different geometrical features. In fact, those targets usually exist on some machine parts including gear roots, shaft shoulders, and stress concentration areas. According to Hertz theory of contact and Miao's theoretical model for predicting residual stress of flat surface, this paper developed a theoretical model for investigating residual stress of targets with different geometrical features including concave arc surface, concave sphere surface, convex arc surface, and sphere surface. AWJ peening of targets with different geometrical features and different radii of Gaussian curved surface was simulated by abaqus. Theoretical results were consistent with numerical simulation results and published experimental results (H. Y. Miao, S. Larose, et al., 2010, “An analytical approach to relate shot peening parameters to Almen intensity,” Surf. Coat. Technol., 205, pp. 2055–2066; Cao et al., 1995, “Correlation of Almen arc height with residual stresses in shot peening process”, Mater. Sci. Technol. 11, pp. 967–973.), which will be helpful for predicting residual stress of gear roots, shaft shoulders, and stress concentration areas after AWJ peening. The research results showed that under the same peening parameters, σmax, σtop, dmax, and dbottom in concave surface (including concave arc surface and concave sphere surface) were the maximum; σmax, σtop, dmax, and dbottom in convex surface (including convex arc surface and sphere surface) were the minimum; for concave surface, σtop, σmax, dbottom, and dmax decreased, respectively, with target radius; for convex surface, σtop, σmax, dbottom, and dmax increased, respectively, with target radius.
Dynamic Trajectory Planning for Failure Recovery in Cable-Suspended Camera Systems
Authors: Passarini Chiara , Zanotto Damiano , Boschetti Giovanni
Published: November 2018

The use of cable-driven parallel robots (CDPR) in real-world applications makes safety a major concern for these devices and a relevant research topic. Cable-suspended camera systems are among the earliest and most common applications of CDPRs. In this paper, we propose a novel after-failure approach for cable-suspended camera systems. This strategy, which is applied after a cable breaks, seeks to drive the end effector, i.e., the camera, toward a safe pose, following an oscillatory trajectory that guarantees positive and bounded tensions in the remaining cables. The safe landing location is optimized to minimize the trajectory time while avoiding collisions with the physical boundaries of the workspace. Results of numerical simulations indicate the feasibility of the proposed approach.
Prospective Life Cycle Assessment Based on System Dynamics Approach: A Case Study on the Large-Scale Centrifugal Compressor
Authors: Peng Shitong , Li Tao , Wang Yue , Liu Zhichao , Tan George Z. , Zhang Hongchao
Published: November 2018

The deficiency of temporal information in life cycle assessment (LCA) may misrepresent the environmental impacts of products throughout the life cycle or at a particular time in the future. For the environmental assessment of energy-consuming products, background data obtained from the LCA database fail to incorporate emissions or extractions reflecting the future situation. To overcome this knowledge gap, we developed a system dynamics (SD) model to predict the evolution of energy structure in China till 2030 and further determined the time-varying emissions of unit electric power combined with the ecoinvent 3.1 database. Additionally, dynamic characterization factors (CFs) of global warming potential (GWP) were integrated into the life cycle impact assessment (LCIA). This study took the PCL803 large-scale centrifugal compressor as an illustrative example in which the temporal-dependent electricity was included in the dynamic life cycle inventory and the dynamic CFs of GWP were included in the LCIA. Environmental impacts were quantified and compared using the traditional and prospective LCA. Results indicated that the environmental burdens under the electricity variation were approximately 13% less than those of conventional LCA, and the GWP under dynamic CFs would be further reduced by 14.5%. The results confirmed that, when socio-economic progress, technical improvement, and dynamic CFs are not considered, the environmental assessment will lead to an overestimation of environmental loads. Therefore, the relevant time-varying parameters should be considered for accurate assessment.
Aerothermal Optimization of Fully Cooled Turbine Blade Tips
Authors: Andreoli Valeria , Braun James , Paniagua Guillermo , De Maesschalck Cis , Bloxham Matthew , Cummings William , Langford Lawrence
Published: November 2018

Optimal turbine blade tip designs have the potential to enhance aerodynamic performance while reducing the thermal loads on one of the most vulnerable parts of the gas turbine. This paper describes a novel strategy to perform a multi-objective optimization of the tip geometry of a cooled turbine blade. The parameterization strategy generates arbitrary rim shapes around the coolant holes on the blade tip. The tip geometry performance is assessed using steady Reynolds-averaged Navier–Stokes simulations with the k–ω shear stress transport (SST) model for the turbulence closure. The fluid domain is discretized with hexahedral elements, and the entire optimization is performed using identical mesh characteristics in all simulations. This is done to ensure an adequate comparison among all investigated designs. Isothermal walls were imposed at engine-representative levels to compute the convective heat flux for each case. The optimization objectives were a reduction in heat load and an increase in turbine row efficiency. The multi-objective optimization is performed using a differential evolution strategy. Improvements were achieved in both the aerodynamic efficiency and heat load reduction, relative to a conventional squealer tip arrangement. Furthermore, this work demonstrates that the inclusion of over-tip coolant flows impacts the over-tip flow field, and that the rim–coolant interaction can be used to create a synergistic performance enhancement.
Extremely Large Oscillations of Cantilevers Subject to Motion Constraints
Authors: Farokhi Hamed , Ghayesh Mergen H.
Published: November 2018

The nonlinear extremely large-amplitude oscillation of a cantilever subject to motion constraints is examined for the first time. In order to be able to model the large-amplitude oscillations accurately, the equation governing the cantilever centerline rotation is derived. This allows for analyzing motions of very large amplitude even when tip angle is larger than π/2. The Euler–Bernoulli beam theory is employed along with the centerline inextensibility assumption, which results in nonlinear inertial terms in the equation of motion. The motion constraint is modeled as a spring with a large stiffness coefficient. The presence of a gap between the motion constraint and the cantilever causes major difficulties in modeling and numerical simulations, and results in a nonsmooth resonance response. The final form of the equation of motion is discretized via the Galerkin technique, while keeping the trigonometric functions intact to ensure accurate results even at large-amplitude oscillations. Numerical simulations are conducted via a continuation technique, examining the effect of various system parameters. It is shown that the presence of the motion constraints widens the resonance frequency band effectively which is particularly important for energy harvesting applications.
Control of Continuous Time Chaotic Systems With Unknown Dynamics and Limitation on State Measurement
Authors: Kaveh Hojjat , Salarieh Hassan
Published: November 2018

This paper has dedicated to study the control of chaos when the system dynamics is unknown and there are some limitations on measuring states. There are many chaotic systems with these features occurring in many biological, economical and mechanical systems. The usual chaos control methods do not have the ability to present a systematic control method for these kinds of systems. To fulfill these strict conditions, we have employed Takens embedding theorem which guarantees the preservation of topological characteristics of the chaotic attractor under an embedding named “Takens transformation.” Takens transformation just needs time series of one of the measurable states. This transformation reconstructs a new chaotic attractor which is topologically similar to the unknown original attractor. After reconstructing a new attractor its governing dynamics has been identified. The measurable state of the original system which is one of the states of the reconstructed system has been controlled by delayed feedback method. Then the controlled measurable state induced a stable response to all of the states of the original system.
Could Chalk Hopping Be Caused by Reverse Chatter?
Authors: Sanders John W.
Published: November 2018

Anyone who has ever used a chalkboard is probably familiar with the phenomenon of “chalk hopping,” where the chalk unexpectedly skips across the chalkboard, leaving a dotted line in its wake. Such behavior is ubiquitous to mechanical systems with moving parts in contact, where it is almost always undesirable. It is widely believed that hopping behavior is a physical manifestation of either the classical Painlevé paradox or a related phenomenon called dynamical jam. The present paper poses the question of whether chalk hopping might be caused by a different, and much more recently discovered, instability called “reverse chatter,” in which two bodies initially in sustained contact can lose contact through a sequence of impacts with increasing amplitude. Previous simulations of reverse chatter have considered only constant external loads, which do not adequately model the forces exerted on a piece of chalk. The current work presents simulation results for a model system in the presence of a control algorithm that mimics the human hand by attempting to keep the chalk in contact with the chalkboard. The simulations reveal that there exist physically realistic parameter values for which a loss of contact occurs that cannot be attributed to either the classical Painlevé paradox or dynamical jam, but which can only be attributed to reverse chatter. Furthermore, the subsequent motion of the system after losing contact is found to be strikingly similar to that of chalk hopping on a chalkboard, to a hitherto unparalleled degree. These results show that neither the classical Painlevé paradox nor dynamical jam is necessary for hopping behavior, and suggest that reverse chatter may be the most plausible explanation for chalk hopping.
Dynamics, Vibrations and Control Lab Equipment Design
Authors: Tekes Ayse , Van Der Horn Kevin , Marr Zach , Tian Chong
Published: November 2018

Take home lab equipment and hands-on learning tools are still in demand for control theory and vibrations courses. The existing equipment are extremely expensive and require wide lab space. The aim of this research is to build vibratory mechanical system that is compact, modular and small scale so that each student can work on their setup and take it home if necessary. For this purpose, in this study, a semi-compliant mechanism is designed to be utilized in systems control and vibrations courses which would enhance the understanding of students by using experimental demonstration of the theoretical systems. The superiorities of the design over commercially available equipment are their low cost and simplicity.

A parallel arm mechanism consisting of several flexible links that can be attached at different points on the slider is designed, finite element analysis (FEA) is performed in Solidworks, and the flexible beams are 3D printed using polyactic acid (PLA) and Polyethylene terephthalate glycol-modified (PETG) filaments. Different configurations of the mechanism are explored by changing the number of flexible beams attached to the slider. The mathematical model of the proposed mechanism can be represented by a single mass and multiple springs in parallel. Since mass is a known property, the equivalent stiffness can be experimentally found from the frequency analysis of free response. For this purpose, a PCB model tri-axial accelerometer is attached to the slider and the equations of motion are derived from the analysis of frequency characteristics of the complaint dual arm mechanism for each configuration. System properties including the equivalent friction are obtained from the acceleration vs time data using logarithmic decrement. The forced response is studied by attaching a load to the mass through a pulley system. The load deflection curve is obtained experimentally from LabVIEW. Since the system parameters are obtained from the free response, Matlab Simulink model outputs for the same initial displacement and force input are verified with the experimental data.
Decoupling Method for PI Controllers via Setpoint Modification Applied to HVAC Systems
Authors: Salsbury Timothy I. , House John M. , Alcala Carlos F.
Published: November 2018

The method described in this paper addresses the problem of interaction in a control system that consists of multiple legacy PI(D) controllers. In these systems, it is often not possible to intercept the signals between the controllers and plant and replacement with multivariable alternatives such as model predictive control (MPC) may not be viable from a cost perspective. To address these issues, we propose a decoupling method that involves first changing the tuning of the controllers and then dynamically adjusting the setpoints. The method enables decoupling of a multiloop control system via setpoint adjustment which can be carried out without having to re-engineer any of the legacy controllers. The paper focuses on the application area of energy systems in buildings where costs are constrained and PID multiloop configurations are prevalent. Simulation test results are presented from two systems to demonstrate the improvement in control achieved with the method.
Crane Guidance Gesture Tracking and Recognition With Nonlinear Estimation and Fuzzy Logic
Authors: Wang Xin , Gordon Chris , Yaz Edwin E.
Published: November 2018

This paper presents a novel human arm gesture tracking and recognition technique based on fuzzy logic and nonlinear Kalman filtering with applications in crane guidance. Kinect visual sensor and MYO armband sensor are jointly utilized to perform data fusion in providing more accurate and reliable information on Euler angles, angular velocity, linear acceleration and electromyography data in real-time. Dynamic equations for arm gesture movement are formulated with Newton-Euler equations based on Denavit-Hartenberg parameters. Nonlinear Kalman filtering techniques, including the extended Kalman filter and the unscented Kalman filter, are applied to perform reliable sensor fusion, and their tracking accuracies are compared. A Sugeno-type fuzzy inference system is proposed for arm gestures recognition. Hardware experiments have shown the efficacy of proposed method for crane guidance applications.
Modeling and Validation of Capacitive Type RF MEMS Switches for Low Actuation Voltage and High Isolation
Authors: Mohite Suhas S. , Madhewar Mukesh , Sawant Vishram B.
Published: November 2018

Design objectives in capacitive type radio frequency micro electro mechanical switches (RF-MEMS) are to reduce actuation voltages and to obtain low insertion losses with high isolation. In this study, we report design, modeling and simulation of three new structural configurations using ANSYS to obtain the optimum geometry; further high frequency simulations are performed using HFSS to obtain low insertion losses and high isolation. The designed switches require only 3.9 to 5 V as pull-in voltage for actuation. The mechanical resonant frequency and quality factor are in the range of 6.5 to 8.7 kHz and 1.1 to 1.2, respectively. Switching times for all the designs are 32 to 38 μs at their respective pull-in voltages. Two of the switch designs have insertion loss of less than 0.25 to 0.8 dB at 60 and 50 GHz, and isolation greater than 58 dB for all three designs.
Passive Pitch Mechanics of Elastic Flapping Wings
Authors: Jankauski Mark A.
Published: November 2018

Many flapping wing micro air vehicles (FWMAVs) utilize a flexible joint that allows the wing to passively rotate about the pitching axis. Generally, simple rigid body models are used to estimate the passive pitching dynamics. However, evidence suggests elastic wings increase aerodynamic force generation and expend less energy relative to rigid wings. As a result, elastic wings are becoming an integral part of FWMAV design. But, the effect of wing elasticity on passive pitching mechanics is unclear. To explore this, we develop a coupled model of an elastic wing attached to a flexible pitching joint. Aerodynamic moments are included through a simple blade element approach. The model is applied to an idealized insect forewing subject to prescribed roll rotation. The simulation results suggest (1) aerodynamic moments, not rigid body inertia or elastic forces, are primarily responsible for lift-generating passive pitch, (2) joint stiffness influences pitching mechanics more than wing elasticity does, and (3) flexible wings can increase net lift by as much as 20% if the pitching joint is mistuned. The framework developed in this paper can be used to design and optimize FWMAV systems in terms of both elastic wings and flexible passive pitch joints.
Adjustable Compliant Mechanism Load Deflection Test Bench Design
Authors: Tekes Ayse , McFall Kevin , Woods Franklin , Bryant Alexander
Published: November 2018

Two adjustable compliant mechanism load deflection test benches are presented in this study. Both test bench mechanisms enable testing the deflection of flexible links or mechanisms. The modularity of the designs provides to test various link forms such as fixed-fixed and pinned-pinned joints. The load deflection test benches consist of a linear actuator, an amplifier rod, a linear rail and a sliding car. The measurement setup is equipped with force and displacement sensors for the linear actuator, various clamps to attach the compliant member, and machine vision software to measure member deflection. A displacement-controlled loading using a linear actuator, rack-pinion attached to a motor, or step loading with a pulley can be applied as an input to the system.

There are several limitations involved in the design. First, the length of the test object should be kept between 5 cm to 30 cm. Second, a low cost linear actuator with a low extension velocity to obtain quasi static deflection curves of the compliant members is required. Finally, the design should also have the capability of providing various types of boundary conditions with interchangeable attachments. The force can be applied either parallel or perpendicular to the test object. Input load deflection is measured with the displacement sensor, and the resulting member displacement measured visually using machine vision software. This software synchronizes data from the displacement sensor and a calibrated camera image to automatically detect deflection using a pinhole camera model and known dimensions of the test apparatus.

The purpose of this study is to design and fabricate a load deflection test setup capable of testing flexible links and compliant mechanisms. Two different designs are proposed and explored in this study. The first design is the modification of a commercially available ECP Model 210 educational turnkey system favorably utilized in undergraduate level vibrations and control labs. By attaching the designed clamps on two carts, fixed-fixed and U shaped compliant link load deflection can be obtained. Four cases such as fixed-fixed buckling beam, U shaped beam buckling with one end sliding, already buckled beam loaded at its upper midpoint, and inverse U-shaped beam loaded at its apex to form deflected M beam (with design 2) are considered. In order to achieve buckled beam experiments in which the load is applied at the midpoint of the already buckled links, a new test bench consisting of a linear actuator, rigid links, rail and two sliding cars is designed.
Contact and Tracking Hybrid Control With Impulse-Momentum Sliding Surface and Terminal Sliding Mode
Authors: Richter Hanz , Mobayen Saleh , Simon Dan
Published: November 2018

The control system proposed in the paper is motivated by robotic testing of prosthetic legs, where a test robot is used to emulate the mechanics of walking. Previously, robust trajectory tracking of walking profiles was used on the test robot’s hip axes, both for swing and stance phases. For the stance phase, a tracking controller does not reproduce the dynamics of weight transfer and release during the swing-stance transitions of human walking. To address this problem, a novel contact mode controller is proposed which allows the test robot to emulate weight transfer and momentum exchange in the stance phase. The swing phase controller is still designed for tracking, but introduces a fast terminal sliding mode controller for rapid convergence to reference swing trajectories with small chattering. This paper introduces the concept of an impulse-momentum sliding surface and develops the control system for a one-degree-of-freedom electromechanical system moving in a vertical axis. A simulation study and a successful real-time implementation are described that illustrate the practical validity of the concept, which can be used in conjunction with more realistic walking models.
Speed Control of Shunt-Wound DC Motors Using Switching Technique
Authors: Nudehi Shahin S. , Newendyke Ryan , Antonides Dylan , Zange Timothy
Published: November 2018

In this paper, a switching feedback control system for speed control of a shunt-wound DC motor is described. In the control system a fast-acting switch periodically opens and closes between the motor terminal and the motor driver in order to estimate the motor’s speed. Theoretical results predicted the stability of the control system and it was shown that the tracking error in the motor’s speed is linearly dependent on the switching rate. To prove the applicability of this approach, an experimental setup was built and the switching control system was implemented using the real-time hardware within MATLAB/SIMULINK™ software.
Setpoint Tracking Control With Discrete Actuators Using Controller Switching
Authors: Chida Y. , Hara R.
Published: November 2018

In the present paper, we discuss a setpoint tracking control problem for a plant with discrete actuators. When a conventional linear servo controller is applied to the plant, undesirable periodic vibrations similar to the limit cycle occasionally occur in the output response caused by synergy with the integration of the steady-state tracking errors and the quantized errors of the control inputs. To prevent an undesirable response, a novel control method is proposed, in which the controller switches the control structure based on the value of the Lyapunov function. The effectiveness of the proposed method was verified through numerical simulations.
Model Predictive Control Based Energy Management of Power-Split Hybrid Electric Vehicles in Presence of Uncertainty
Authors: HomChaudhuri Baisravan , Hall Carrie M.
Published: November 2018

A model predictive control (MPC) based robust energy management strategy for power-split hybrid electric vehicles (HEVs) is proposed in this paper which can guarantee charge sustaining constraint satisfaction in presence of uncertainty in future torque demand and vehicle velocity. The proposed method utilizes robust backward reachability analysis to pre-compute a robust set from where control solutions exist that ensure charge sustaining constraint satisfaction despite the uncertainty. This set is then used as the terminal set constraint of the MPC problem followed by tightening of state constraints for robust constraint satisfaction. An equivalent convex optimal control is then formulated which is solved in a receding horizon fashion. Simulation results show the efficacy of the proposed control strategy in robust constraint satisfaction.
A Bowden Cable-Based Series Elastic Actuation Module for Assessing the Human Wrist
Authors: Erwin Andrew , Moser Nick , McDonald Craig G. , O’Malley Marcia K.
Published: November 2018

Currently, wrist passive stiffness and active range of motion, two clinically relevant properties, are assessed using devices designed for rehabilitation. As a result, these devices do not have sufficient torque output and range of motion for complete wrist biomechanical assessment. To address these limitations, we are developing an actuation module specifically for assessing wrist biomechanical properties. Our device employs a serial kinematic exoskeletal architecture to directly interact with and measure wrist flexion/extension and radial/ulnar deviation. A Bowden cable-based actuation scheme, locating the motors off-board, was adopted for increased device range of motion and torque output compared with previous wrist exoskeletons. Additionally, the device was designed to incorporate a rotational elastic element at each joint, creating series elastic actuators, for accurate torque control and direct torque measurement. In this work, we present the design and demonstration of a 1-DOF module of the device, which can interact with a user’s wrist in flexion/extension, providing an important first step towards the control, evaluation, and application of the 2-DOF device.
Sensitivity Analysis of Drivetrain Oscillations in Electric Vehicles
Authors: Foerth Matthias , Ota Junya , Lienkamp Markus
Published: November 2018

The increase of electric mobility is leading to new drivetrain designs in vehicle development. A common problem in electric drivetrains are torsional oscillations caused by elastic components. These components are wheel shafts, tires and bushings. A common problem, its sensitivity to parameter variation has not yet been fully investigated. The objective of this study is to quantify the sensitivity of oscillation frequency, damping and coupling between components with respect to key drivetrain parameters. A parameter space is investigated using Monte-Carlo sampling. A linear state space model is parameterized for each sample. Modal analysis permits the analysis of oscillation frequency, damping and coupling between components using the state variables. Subsequently, a Gaussian mixture model clusters the resulting data to form mode groups. Finally, linear regressions quantify the sensitivities. The results show oscillation damping can be increased by stiff wheel shafts. Decoupling of components in oscillation modes is mainly achieved by separating the oscillation frequencies of the different modes.
Learning to Predict Coronary Perfusion Pressure During Cardiopulmonary Resuscitation
Authors: Gandhi Manan , Pan Yunpeng , Theodorou Evangelos , Sebastian Pierre , Olson Matt , Yannopoulos Demetri
Published: November 2018

The goal of this work is to advance the capability of automated, mechanical cardiopulmonary resuscitation (CPR) by predicting Coronary Perfusion Pressure (CPP) within 5 mmHg at a given moment in time. We aim to utilize methods from machine learning in order to model the CPP of a porcine patient subjected to automated chest compressions. During preprocessing of the data, we show how data sampling rate, delays and moving average filtering can improve predictions. We demonstrate state of the art modeling performance utilizing a variety of algorithms, and analyze the performance of each algorithm for single-step and long-term predictions. The results indicate that a delayed linear system achieves this target CPP within 0.25 mmHg. For longer time horizons, a more complex model is required. We demonstrate that the Long-short-term-memory (LSTM) network has the best single run performance, while the Sparse Spectrum Gaussian Process (SSGP) has the best average performance.
The Effect of Nonlinear Springs in Jumping Mechanisms
Authors: Sadeghi Sahand , Betsill Blake D. , Tallapragada Phanindra , Li Suyi
Published: November 2018

This research investigates the potential effects of utilizing nonlinear springs on the performance of robotic jumping mechanisms. As a theoretical example, we study dynamic characteristics of a jumping mechanism consisting of two masses connected by a generic nonlinear spring, which is characterized by a piecewise linear function. The goal of this study is to understand how the nonlinearity in spring stiffness can impact the jumping performance. To this end, non-dimensional equations of motion of the jumping mechanism are derived and then used extensively for both analytical and numerical investigations. The nonlinear force-displacement curve of the spring is divided into two sections: compression and tension. We examine the influences of these two sections of spring stiffness on the overall performance of the jumping mechanism. It is found that compression section of the nonlinear spring can significantly increase energy storage and thus enhance the jumping capabilities dramatically. We also found that the tension section of the nonlinear force-displacement curve does not affect the jumping performance of the center of gravity, however, it has a significant impact on the internal oscillations of the mechanism. Results of this study can unfold the underlying principles of harnessing nonlinear springs in jumping mechanisms and may lead to the emergence of more efficient hopping and jumping systems and robots in the future.
Towards Computational Modeling of Temperature Field Evolution in Directed Energy Deposition Processes
Authors: Li Jianyi , Wang Qian , Michaleris Panagiotis (Pan)
Published: November 2018

In modeling and simulating thermo-mechanical behavior in a directed energy deposition process, it often needs to compute the temperature field evolved in the deposition process since thermal history in the deposition process would affect part geometry as well as microstructure, material properties, residual stress, and distortion of the final part. This paper presents an analytical computation of temperature field evolved in a directed energy deposition process, using a single-bead wall as an illustrating example. Essentially, the temperature field is computed by superposition of the temperature fields generated by the laser source as well as induced from each of the past beads, where the transient solution to a moving heat source in a semi-infinite body is applied to describe each individual temperature field. For better characterization of cooling effect (temperature contribution from a past bead), a pair of positive and negative virtual heat sources is assigned for each past bead. In addition, mirrored heat sources through a reflexion technique are introduced to define the adiabatic boundaries of the part being built and to account for the substrate thickness. In the end, three depositions of Ti-6AL-4V walls with different geometries and inter-layer dwell times on an Optomec® laser engineered net shaping (LENS) system are used to validate the proposed analytical computation, where predicted temperatures at several locations of the depositions show reasonable agreement with the in situ temperature measurements, with the average prediction error less than 15%. The proposed analytical computation for temperature field in directed energy deposition could be potentially used in model-based feedback control for thermal history in the deposition, which could affect microstructure evolution and other properties of the final part.
Energy-Efficient Control Approach for Automated HEV and BEV With Short-Horizon Preview Information
Authors: Seok Jinwoo , Wang Yan , Filev Dimitar , Kolmanovsky Ilya , Girard Anouck
Published: November 2018

The interest in autonomous electrified vehicles has rapidly increased in recent years. In this paper, a speed trajectory generation method based on speed and road grade preview over a short horizon is presented, to improve energy efficiency of the autonomous power split HEV and BEV. The speed trajectory is generated by minimizing the required cumulative over the the horizon wheel power, including regenerative power. We confirm by simulations that the generated speed profiles improve MPG (or MPGe) even though only a short horizon preview information is used with small deviation permitted from the nominal speed profile.
A Control-Oriented Reaction-Based SI Engine Combustion Model
Authors: Li Ruixue C. , Zhu Guoming G.
Published: November 2018

This paper proposes a control-oriented chemical reaction-based two-zone combustion model designed to accurately describe the combustion process and thermal performance for spark-ignition engines. The combustion chamber is assumed to be divided into two zones: reaction and unburned zones, where the chemical reaction takes place in the reaction zone and the unburned zone contains all the unburned mixture. In contrast to the empirical pre-determined Wiebe-function-based combustion model, an ideal two-step chemical reaction mechanism is used to reliably model the detailed combustion process such as mass-fraction-burned (MFB) and rate of heat release. The interaction between two zones includes mass and heat transfer at the zone interface to have a smooth combustion process. This control-oriented model is extensively calibrated based on the experimental data to demonstrate its capability of predicting the combustion process and thermodynamic states of the in-cylinder mixture.
Rapid Information Transfer in Swarms Under Update-Rate-Bounds Using Delayed Self Reinforcement
Authors: Devasia Santosh
Published: November 2018

The effectiveness of a network’s response to external stimuli depends on rapid distortion-free information transfer across the network. However, the rate of information transfer, when each agent aligns with information from its network neighbors, is limited by the update rate at which each individual can sense and process information. Moreover, such neighbor-based, diffusion-type information transfer does not predict the superfluid-like information transfer during swarming maneuvers observed in nature. The main contribution of this article is to propose a novel model that uses self reinforcement, where each individual augments its neighbor-averaged information update using its previous update, to (i) increase the information-transfer rate without requiring an increased, individual update-rate; and (ii) enable superfluid-like information transfer. Simulations results of example systems show substantial improvement, more than an order of magnitude increase, in the information transfer rate, without the need to increase the update rate. Moreover, results show that the DSR approach’s ability to enable superfluid-like, distortion-free information transfer results in maneuvers with smaller turn radius and improved cohesiveness.