Rectangular Path Research Articles

Design and simulation for a one-degree-of-freedom-based rectangular path generating mechanism using an ellipse

Conventional rectangular path generating mechanisms can not avoid structural complexity due to the large number of components and high degree of freedom. Therefore, the authors present a simplified rectangular path generating mechanism using an ellipse. The mechanism not only consists of much fewer components than conventional mechanisms, but also has one degree of freedom. In the design procedure, a reverse kinematic design is implemented, and a theoretical analysis of the displacement, velocity and acceleration is conducted to validate the superiority of this mechanism. In particular, this paper highlights the low acceleration values at the contact points between the ellipse and the frame. This is noteworthy since acceleration is directly correlated with impulsive forces that induce early malfunctions, low stability and wear in devices using such mechanisms. In addition, this paper discusses achieving optimal eccentricity to have the lowest acceleration at the corners. Lastly, a dynamics analysis for two cases–a mechanism with a perfect circle and a mechanism with an ellipse–is carried out using dynamic analysis software to investigate real reaction force at the corners. Conclusively, the novelty of the mechanism using an ellipse is validated through the kinematics and dynamics analyses.

Relationship between Executive Function and Dual Task Physical Performance among Older Adults-A Cross Sectional Study

Background: Older adults with both physical and cognitive impairment are at higher risk for dementia, fall and disability. So, identifying whether physical performance decline is associated with executive dysfunction is important for developing physical therapy early intervention strategies for older adults. Purpose: (1) To examine the relationship between executive functions and dual-task physical performances among older adults, (2) To confirm executive function as a useful predictor for functional limitation or disability process in older adults. Methodology: To measure physical performance, first, reference gait speed on 10 m path was measured. Secondly, dual task gait speed was calculated from 20 m rectangular path with obstruction and picking up an object from it while walking at their comfortable pace. Participants had to cross the obstacles simultaneously picking the ball from bucket. The time to finish the task was measured and from that gait speed during dual task was calculated. The TMT-B test was used to evaluate the components of executive function. To complete this test, participant was asked to use a pencil to connect 25 encircled numbers and letters in numerical and alphabetical order, alternating between numbers and letters. Time to finish this test was recorded. Results: After analyzing data, for dual task gait speed and TMT-B, we got the value of Spearman’s correlation coefficient(r) is 0.698 and level of significance (p<0.05). For reference gait speed and TMT-B, we got the value of Spearman’s correlation coefficient(r) is 0.600 and level of significance (p<0.05) Conclusion: This points out that there is statistically significant correlation between executive function and dualtask physical performance among older adults.

Personal Dead Reckoning Using IMU Mounted on Upper Torso and Inverted Pendulum Model

There has been an increasing demand for infrastructureless localization. Current approaches involving inertial measurement unit (IMU) generally utilize step detection and step counting to estimate the displacement. However, the accuracy is affected, because the step sizes are neglected. Some groups have proposed algorithms that involve placing the IMU on the foot to estimate the step size, but users have commented that it affects their walking. Hence, this paper presents a new method to estimate both the forward displacement and orientation with the IMU placed at the upper torso. Placing IMU at the upper torso to estimate horizontal displacement has been challenging, as the accuracy of the inertial sensors is greatly handicapped by the notorious integration drift when performing integration in the travel direction with the lack of opportunity for zero velocity update. Thus, a novel method is proposed in this paper by exploiting the vertical component of the accelerometer reading. An inverted pendulum model is proposed with a step detector and a step length estimation method. The system is implemented, and two sets of experiments are conducted to demonstrate the capability. The experiment sets include straight lines and rectangular shape path, and in each set, four step sizes of small, normal, large, and mixture are conducted for each test and each test is performed four times. The experimental results show an average displacement error of 1% for straight line paths and 2% for the rectangular paths.

Sensorimotor-Conceptual Integration in Free Walking Enhances Divergent Thinking for Young and Older Adults.

Prior research has shown that free walking can enhance creative thinking. Nevertheless, it remains unclear whether bidirectional body-mind links are essential for the positive effect of free walking on creative thinking. Moreover, it is unknown whether the positive effect can be generalized to older adults. In Experiment 1, we replicated previous findings with two additional groups of young participants. Participants in the rectangular-walking condition walked along a rectangular path while generating unusual uses for chopsticks. Participants in the free-walking group walked freely as they wished, and participants in the free-generation condition generated unconstrained free paths while the participants in the random-experienced condition walked those paths. Only the free-walking group showed better performance in fluency, flexibility, and originality. In Experiment 2, two groups of older adults were randomly assigned to the free-walking and rectangular-walking conditions. The free-walking group showed better performance than the rectangular-walking group. Moreover, older adults in the free-walking group outperformed young adults in the rectangular-walking group in originality and performed comparably in fluency and flexibility. Bidirectional links between proprioceptive-motor kinematics and metaphorical abstract concepts can enhance divergent thinking for both young and older adults.

Optimal synthesis and kinematic analysis of adjustable four-bar linkages to generate filleted rectangular paths

ABSTRACTContinuous and precise path generation of filleted-rectangle using adjustable four-bar mechanism is presented. Coupler path passing through precision points is verified using reconstructed adjustable parameter curve (RAPC) method proposed in this article. This method extracts adjustable parameter values of intermediate path points, along the filleted rectangular path generation profile, corresponding to uniformly incremented crank input values without using interpolation of data points. Influence of number of precision points and spacing between them in achieving perfect coupler path of filleted-rectangle are analyzed. Verification of filleted-rectangle path generation and kinematic analysis of adjustable four-bar crank-rocker mechanism are carried out through motion simulation. Hybrid method combining Genetic Algorithm and Pattern Search is used in the synthesis of adjustable four-bar mechanisms to generate coupler path for three different filleted-rectangles. Results and conclusions prove the validity of the method suggested in this work.

Deformation behavior of woven glass/epoxy composite substrate under thermo-mechanical loading

Abstract The deformation behaviors of woven glass/epoxy composite substrate under four thermo-mechanical loading paths, i.e. rectangular and triangular paths in clockwise and anticlockwise directions within a temperature range of 25–250 °C were investigated. Temperature scanning tests were conducted to identify the viscoelastic property of the material. The glass transition temperature of the composite substrate was 138 °C, above which significant reduction of storage modulus was observed. The deformation behavior of the composite substrate was temperature and history dependent, and change of deformation rate resulted from state transition was noticeable. The residual deformation of specimen following the anticlockwise rectangular loading path was the largest in contrast with the lowest in clockwise rectangular path. The residual deformations in two triangular paths were close after each cycle.

Thermo-mechanical Coupling Properties of Proton Exchange Membrane in Liquid Water

In this study, the effects of the combination and interaction of thermal and mechanical loading on mechanical behaviors of proton exchange membranes (PEMs) under immersed condition were investigated. Experiments under two kinds of loading path were performed: the quasi-simultaneous loading path where mechanical loads and temperature occurred simultaneously and the rectangular loading path where thermal and mechanical loads were inserted in turn. The quasi-simultaneous loading path is composed of in-phase, 90° and 180° out-of-phase loading paths. Comparison between in-phase and 180° out-of-phase loading paths showed that strain accumulation under in-phase loading path mainly resulted from creep strain while that under 180° out-of-phase loading path were mostly induced by cyclic stress. Accumulation of strain was comprised of tensile strain and creep strain, and these two strain components showed different evolution trends with thermo-mechanical cycles. In addition, the modulus of the membrane was history-dependent as indicated from results of rectangular loading path. Through comparing creep strain with strain energy density which is an indicator of damage in the membrane, we came to the conclusion that creep strain contributed to the damage of the membrane in the first three cycles.

Uniaxial and Biaxial Ratcheting of ST52 Steel under Variable Amplitude Loading – Experiments and Modeling

The paper shows results of experiments focused on the influence of loading frequency on ratcheting as well as interesting results obtained from uniaxial tests and biaxial tests with rectangular and circular loading paths under variable amplitude loading realized on the ST 52 steel at the VŠB-Technical University of Ostrava. The model based on the AbdelKarim-Ohno kinematic hardening rule and Calloch isotropic hardening rule was used for stress-strain behavior description in finite element analysis using commercial software Ansys. The material model was implemented into the FE code using a fortran subroutine. Results of simulations containing ratcheting and cyclic hardening effects correspond with experiments very well.

Kinematic Analysis of Rectangular Path Generating Adjustable Four-Bar Linkage

This paper focuses on the kinematic analysis of rectangular path generating adjustable four-bar crank rocker linkage. One of the ground pivots of rocker side of the adjustable mechanism is subjected to continuous adjustment while the crank arm is given uniform angular velocity. Variations of coupler and rocker position, velocity and acceleration are computed for continuously changing phases of the adjustable four bar linkage. These kinematic parameters are compared with non-adjustable four-bar mechanism. Effect of the continuous adjustment on transmission angle and torque ratio are presented. The above procedures are implemented successfully in MATLAB environment and graphical results are presented.

Analytical modelling using Green’s functions of heat transfer in a flat solar air collector

We have developed a purely analytical model to simulate the thermal behaviour of a flat solar air collector operating in forced convection.The mathematical model developed is based on a direct solution using Green’s functions of the linear equation for heat propagation in the air flowing through the rectangular flow path, interacting with the solid walls of the solar collector. Given the speed of the air flow and the mean solar heat flux, this approach can be used analytically to determine the two-dimensional temperature profile throughout the fluid.This analytical model is confirmed experimentally, and can determine the local and mean temperature field in the fluid and, in particular, the surface convective heat flow. It is also used to identify changes in the convective heat exchange coefficient as a function of position and air temperature at the solar collector outlet.

Thermal Density Factor Analysis of Proton Exchange Membrane by Using Cfd

The objective of the project is to analyze Proton Exchange Membrane (PEM) Fuel Cell model numerically to understand the performance of the Fuel Cell model in various design and operating parameters which is difficult to analyze through the experiment. The numerical analysis was performed on single channel fuel cell which has INTERDIGIT rectangular flow path and also analysis was performed by varying the cross section like semicircular and triangular flow channel. After completing the study of analysis of the single channels, the numerical analysis work was performed on original PEMFC model which is used in fuel cell laboratory. Various analyses were carried out for the model by varying the parameters like varying the pressure, temperature. After varying the flow parameters similar procedure was followed for the analysis of various INTERDIGIT models with semicircular and triangular cross section and the performance of the models. The results show that the performance of the PEM Fuel Cell model is improved by decreasing the temperature and by increasing the operating pressure and by using semicircular and triangular flow channels compared with rectangular channel.

Polarization phase shifting cyclic interferometer for surface profilometry of non-birefringent phase samples

A rectangular path cyclic interferometer has the unique property that the counter-propagating wavefronts travelling in the interferometer arms are folded with respect to each other in the plane of the interferometer although the two wavefronts finally emerge from the interferometer unfolded. A phase disturbance introduced in one lateral half of the interferometer arm is therefore manifested in complementary lateral halves of the observed interference pattern. This phenomenon is utilized to evaluate the surface profile of a reflecting sample placed on one of the interferometer mirrors. The sample phase is retrieved using polarization phase shifting. Experimental results showing three-dimensional surface morphology of a small scale integrated circuitry directly etched on silicon are presented.

A Proportional-Integral-Derivative Control Scheme of Mobile Robotic platforms using MATLAB

This paper proposes an approach for the navigation of mobile robots namely Khepera 3 and iRobot Create in a designated environment. In this study, the navigation system of Khepera 3 includes the motion of the mobile robot at a particular angle to reach a particular goal and avoidance of the obstacle that may occur in its path. Obstacle avoidance is realized using Blending and Hard switching techniques respectively and the navigation system of iRobot Create includes its movement in a rectangular path. In controlling the navigation of the robots, Proportional-Integral-Derivative (PID) controller is used. The most suitable set of values of PID parameters implemented for safe and effective navigation of the robots have been presented. Computer simulation is done using MATLAB software. Keywords: Navigation, Mobile robots, Obstacle avoidance, Blending, Hard switching, PID.

New integral forms of generalized Mathieu series and related applications

The main object of this article is to present a systematic study of integral representations for generalized Mathieu series and its alternating variant, and to derive a new integral expression for these special functions by contour integration using rectangular integration path. Also, by virtue of newly established integral form of generalized Mathieu series, we obtain a new integral expression for the Bessel function of the first kind of half integer order, solving a related Fredholm integral equation of the first kind with nondegenerate kernel.

Contour Errors during Milling Process

To achieve high quality and productivity during continuous contouring, it is important to know how the two axes work together to move the machine in a circular or rectangular path. For this reason, we have analyzed circular and linear motion trajectories and the frequency response of the system during milling process. In the same time, is required to analyses simultaneously both mechanical and control subsystems. Based on these problems, the main objectives of this work have been defined to find a way to improve dimensional accuracy.

Self-referenced rectangular path cyclic interferometer with polarization phase shifting

A polarization phase shifting interferometer using a cyclic path configuration for measurement of phase nonuniformities in transparent samples is presented. A cube beam splitter masked by two linear polarizers is used to split the source wavefront into two counter propagating linearly polarized beams that pass through the sample. At the output of the interferometer, the two orthogonally polarized beams are rendered circularly polarized in the opposite sense through the use of a quarter wave plate. Finally, phase shifting is achieved by rotating a linear polarizer before the recording plane. In a rectangular path interferometer, although the two counter propagating wavefronts are laterally folded with respect to each other in the interferometer arms, the beams finally emerge mutually unfolded at the output of the interferometer. This phenomenon is utilized to create a reference if the sample is introduced in one lateral half of the beam in any one of the interferometer arms. The polarization phase shifting technique is used to generate four phase-shifted interferograms, which are utilized to evaluate the phase profile of the phase sample. Experimental results presented validate the proposed technique.

The study of path error for an omnidirectional home care mobile robot

The first objective of this research was to develop an omnidirectional home care mobile robot. A PC-based controller controls the mobile robot platform. This service mobile robot is equipped with an “indoor positioning system” and an obstacle avoidance system. The indoor positioning system is used for rapid and precise positioning and guidance of the mobile robot. The obstacle avoidance system can detect static and dynamic obstacles. In order to understand the stability of a three-wheeled omnidirectional mobile robot, we carried out some experiments to measure the rectangular and circular path errors of the proposed mobile robot in this research. From the experimental results, we found that the path error was smaller with the guidance of the localization system. The mobile robot can also return to its starting point. The localization system can successfully maintain the robot’s heading angle along a circular path.

J031021 数値計算によるマイクロチャンネルの伝熱特性評価([J03102]電子情報機器,電子テバイスの強度・信頼性評価と熱制御(2))

In this study, we fabricated microchannel for cooling of the electronic components. Microchannel was made of polydimethylsiloxane (PDMS) elastomer using soft lithography techniques. An epoxy-based photoresist (SU-8) was used as a master mold to induce soft lithography. The fabricated microchannel had a rectangular flow path with length of 24mm, width of 500pm and depth of 50vtm. We measured heat flux for water flows in the fabricated microchannel with heated plate. Water flows were laminar fully developed flow. The maximum heat flux was 44W/cm^2 for a 38K temperature difference, and flow rate of 2.0 cm^3/min. We simulate the experiment, and numerical calculation results were compared with experimental results. We clear measurements problems from the difference of experimental and numerical results.

Out-of-phase thermo-mechanical coupling behavior of proton exchange membranes

The thermal effects and mechanical effects on the durability of proton exchange membranes (PEMs) have been studied extensively in the literatures. However researches on the thermo-mechanical coupling behavior of PEMs are very limited. In this study, the interaction of mechanical and thermal effects in Nafion® NRE-212 was investigated using experimental methods. The thermo-mechanical coupling experiments were conducted following the in-phase proportional loading path, where the maximum/minimum mechanical loads and temperatures occur simultaneously and out-of-phase non-proportional rectangular loading paths where a phase difference of 90° existed between thermal and mechanical loads. During the creep processes under a variable temperature in out-phase profiles, the creep strain was found to be history-dependent in the membrane. The effect of initial temperature on the creep was significant in the first cycle. Moreover, temperature cycles were applied as thermal loading conditions and the history-dependence was also observed for thermal stresses. The maximum thermal stress did not occur at the lowest temperature.

Measurement error associated with the SAGIT/Squash computer tracking software

The velocities and distances covered by players during competition serve as a basis for planning fitness regimes according to the specific demand of the sport. The techniques used to calculate these movement parameters have ranged from human judgements to technological solutions such as GPS and computer vision. This paper evaluates the accuracy of a computerized motion tracking system (SAGIT/Squash) that uses computer vision methods on video captured via a fixed single camera located centrally above the court. Digital images were processed automatically with operator supervision so that any tracking errors could be rectified and manual tagging of all shots added. Four separate experiments were used to assess the error associated with tracking adult players' velocities and positions with respect to the court floor. Experiment 1 involved players standing still in different areas of the court. The tracking software was found to be more accurate when a player was stood in the centre of the court (1.33 m · min−1 error) than in the corners (2.61 m · min−1 error), predominately due to systematic errors (e.g. calibration). Experiment 2 was conducted in the same manner as Experiment 1 except that the players vigorously swung a racket around their body continuously. This resulted in 15 times the error found in Experiment 1 for the distance covered during 1 min. However, this is an unrealistic estimate of the true error when assessing matches, as during matches the racket is only swung approximately 35% of the time. Experiment 3 involved a player running at different speeds around a rectangular path on the court. The resultant trajectory, as captured by the software, was compared using different Gaussian smoothing equations of kernel widths 0.25 s, 0.5 s, and 1 s. The best solution (0.5 s) resulted in the most accurate trajectory, although the difference in distance calculated between the different equations was negligible. Experiment 4 used the 0.5-s smoothing equation to assess the tracking accuracy for a player running at a relatively steady speed in a more realistic circular trajectory. The trajectory of the pixel image was shown to have a smaller radius than the reference trajectory at increased speeds, due to the tendency of the player to lean over when negotiating a circular path. The error associated with the distance covered over 1 min was shown to range between 1.33 and 21 m depending on the nature and position of the player's movements. Values, typically somewhere in this range, are likely to be evident during typical use of this software.