A simple improvement of an off-grid solar photovoltaic panel using an integrated reflector

This work presents a simple demonstration of a solar photovoltaic (PV) panel integrated with mirror reflectors to increase electric energy generation. The reflector was integrated with a PV panel and its angle was adjusted to an incline to optimize sunlight collection. Current and voltage generated by PV panel was recorded by an Arduino data logger. The integrated-reflector PV panel at an appropriate incline angle of 70 degrees presented a 9.38% increased electric energy beyond that of a conventional PV panel. This result was because the reflector provided greater sunlight to the PV panel. Therefore, this method can be used to increase solar PV panel performance without the installation of additional panels.

Balancing inverted pendulum cart on inclines using accelerometers

The balance of inverted pendulum on inclined surfaces is the precursor to their control in unstructured environments. Researchers have devised control algorithms with feedback from contact (encoders - placed at the pendulum joint) and non-contact (gyroscopes, tilt) sensors. We present feedback control of Inverted Pendulum Cart (IPC) on variable inclines using non-contact sensors and a modified error function. The system is in the state of equilibrium when it is not accelerating and not falling over (rotational equilibrium). This is achieved when the pendulum is aligned along the gravity vector. The control feedback is obtained from non-contact sensors comprising of a pair of accelerometers placed on the inverted pendulum and one on the cart. The proposed modified error function is composed of the dynamic (non-gravity) acceleration of the pendulum and the velocity of the cart. We prove that the system is in equilibrium when the modified error is zero. We present algorithm to calculate the dynamic acceleration and angle of the pendulum, and incline angle using accelerometer readings. Here, the cart velocity and acceleration are assumed to be proportional to the motor angular velocity and acceleration. Thereafter, we perform simulation using noisy sensors to illustrate the balance of IPC on surfaces with unknown inclination angles using PID feedback controller with saturated motor torque, including valley profile that resembles a downhill, flat and uphill combination. The successful control of the system using the proposed modified error function and accelerometer feedback argues for future design of controllers for unstructured and unknown environments using all-accelerometer feedback.

Computational Flow Analysis on a Real Scale Run-of-River Archimedes Screw Turbine with a High Incline Angle

The Archimedes screw turbine (AST) is the most sustainable mini-hydropower extraction method that offers number of economic, social, and environmental advantages. Nowadays, many researchers are interested in AST development as it is considered a new technology. Currently, a lot of researchers are conducting experimental testing of the screws, comparing their reliability with computational fluid dynamic (CFD) analyses. Almost all of them are lab-scale testing models that claiming an average 80% efficiency for low pitch angles. In the case of a real site with a small inclination angle, the length of the screw is large enough to cause severe problems, specially related to bending of the screw. Therefore, this research was conducted to analyze the CFD flow field in a real site-scale AST with the maximum possible inclination of 45 degrees. In addition, the design was done without the upper and lower reservoir as it was conceived as a run-of-river flow system. The simulated real scale AST result showed a maximum efficiency of around 82% for a 5.2 m hydraulic head and 0.232 m3/s discharge. Many researchers claim above 80% efficiency for low inclination angle ASTs with reservoirs. This CFD study indicates that even higher inclination angle ASTs can achieve 80% efficiency in run-of-river; real-scale applications.

Subjective Preferences and Discomfort Ratings of Backrest and Seat Pan Adjustments at Various Speeds

Power seats (i.e., electrically adjustable seats that can be designed to move in several ways) have become increasingly common in airplanes, vehicles, and offices. Many studies have investigated the effects of seat attitude parameters, for example, the inclined angles of a backrest, on discomfort during the adjustment process. However, few studies have considered discomfort under different speeds during the adjustment process. In this study, we investigated discomfort with three speeds (i.e., “fast”, “median”, and “slow” corresponding to three durations of 15, 20, and 25 s, respectively) and two adjustments of a power seat, i.e., incline angle adjustment of the backrest and fore-and-aft position adjustment of the seat pan. We also investigated the effects of different physiological parameters on subjects’ discomfort. Twenty-four subjects (12 males and 12 females) completed a questionnaire to indicate their adjustment condition preferences, to rate their overall discomfort during the adjustment processes on a category-ratio scale, and to rate their local body discomfort. The majority of subjects preferred the fast speed adjustment condition and the trend was that a lower backrest adjustment speed increased discomfort during the process. The dominant local discomfort was in the upper and lower back regions during the backrest adjustment, whereas there was no obvious dominant local discomfort during the seat pan adjustment. The physiological parameters also had significant correlations with discomfort in some adjustment movements, for example, the discomfort was negatively correlated with height during the backrest adjustment.

Dynamic Simulation-Guided Design of Tumbling Magnetic Microrobots

Design of robots at the small scale is a trial-and-error based process, which is costly and time-consuming. There are few dynamic simulation tools available to accurately predict the motion or performance of untethered microrobots as they move over a substrate. At smaller length scales, the influence of adhesion and friction, which scales with surface area, becomes more pronounced. Thus, rigid body dynamic simulators, which implicitly assume that contact between two bodies can be modeled as point contact are not suitable. In this paper, we present techniques for simulating the motion of microrobots where there can be intermittent and non-point contact between the robot and the substrate. We use these techniques to study the motion of tumbling microrobots of different shapes and select shapes that are optimal for improving locomotion performance. Simulation results are verified using experimental data on linear velocity, maximum climbable incline angle, and microrobot trajectory. Microrobots with improved geometry were fabricated, but limitations in the fabrication process resulted in unexpected manufacturing errors and material/size scale adjustments. The developed simulation model is able to incorporate these limitations and emulate their effect on the microrobot's motion, reproducing the experimental behavior of the tumbling microrobots, further showcasing the effectiveness of having such a dynamic model.

Effect of Pitch Parameters on Aerodynamic Forces of a Straight-Bladed Vertical Axis Wind Turbine with Inclined Pitch Axes

Pitch regulation plays a significant role in improving power performance and achieving output control in wind turbines. The present study focuses on a novel, pitch-regulated vertical axis wind turbine (VAWT) with inclined pitch axes. The effect of two pitch parameters (the fold angle and the incline angle) on the instantaneous aerodynamic forces and overall performance of a straight-bladed VAWT under a tip-speed ratio of 4 is investigated using an actuator line model, achieved in ANSYS Fluent software and validated by previous experimental results. The results demonstrate that the fold angle has an apparent influence on the angles of attack and forces of the blades, as well as the power output of the wind turbine. It is helpful to further study the dynamic pitch regulation and adaptable passive pitch regulation of VAWTs. Incline angles away from 90° lead to the asymmetric distribution of aerodynamic forces along the blade span, which results in an expected reduction of loads on the main shaft and the tower of VAWTs.

THE EFFECTS OF SWIRL AND TUMBLE RATIOS ON THE ENGINE PERFORMANCE OF MOTORBIKES

Nowadays, motorbikes are still the main and most popular transport in Asian countries, especially, in Vietnam. However, the manifold intake systems in motorbikes are usually designed in a simple structure, which can reduce engine performance and increases fuel consumption in motorbikes. This paper presents the study of the improvement of the intake system in a 125cc motorbike engine to enhance air-fuel mixing quality that can increase the engine performance. The study employs the ANSYS software to obtain an optimal intake systemthrough the tumble and swirl ratios in different simulation cases. Another model wasalso built by Matlab/Simulink to examine the effects of swirl and tumble ratios on engine performance and fuel consumption at various engine speeds. The simulation results show that the modified intake system withan incline angle of 30o has optimal tumble and swirl ratios. Accordingly in conclusion, power output and torque of the engine with the modified intake system are higher, while the fuel consumption is lower than previouslyfound.

Flow Characteristics of a Straight-Bladed Vertical Axis Wind Turbine with Inclined Pitch Axes

Currently, vertical axis wind turbines (VAWT) are considered as an alternative technology to horizontal axis wind turbines in specific wind conditions, such as offshore farms. However, complex unsteady wake structures of VAWTs exert a significant influence on performance of wind turbines and wind farms. In the present study, instantaneous flow fields around and downstream of an innovative VAWT with inclined pitch axes are simulated by an actuator line model. Unsteady flow characteristics around the wind turbine with variations of azimuthal angles are discussed. Several fluid parameters are then evaluated on horizontal and vertical planes under conditions of various fold angles and incline angles. Results show that the total estimated wind energy in the shadow of the wind turbine with an incline angle of 30° and 150° is 4.6% higher than that with an incline angle of 90°. In this way, appropriate arrangements of wind turbines with various incline angles have the potential to obtain more power output in a wind farm.

Numerical and experimental investigation of notch-induced high-speed precise shearing of 42CrMo bar

A notch-induced high-speed precise shearing method was developed for high-strength metal bars, which prefabricated V-shape circumferential notches in batch on the bar surface to make stress concentration, and applied a high-speed load to complete separation on a new type of electric-pneumatic counter hammer. The FE simulation and experimental tests were conducted; the influences of loading speed, notch depth, and axial clearance were analyzed on the fracture behavior and blank quality; the microfracture mechanism was further investigated. The results showed that the circumferential notch inhibited the plastic distortion and obtained high precision chamfered billets, with a roundness error of 1.34%, flatness error of 0.34 mm, and incline angle of 0.87°. Besides, the surface notch effectively reduced Max. impact force and fracture energy. The fractography revealed that: for the notched bar, the cracks initiated from the thin extrusion layers at the bilateral-notch tips, and from micro extrusion and intrusion at the top-notch tip. The predominant microfracture mechanism involves microvoid coalescence and forming of quasi-parabolic dimples along with the shear stress.

Finite element analysis of the behavior of bonded composite patches repair in aircraft structures

This paper aims to analyze the multi-effects of the glass fiber reinforced polymer (GFRP) composite patch to repair the inclined cracked 2420-T3 aluminum plate. Three-dimensional finite element method (FEM) was used to study the effect of GFRP composite patch with different stacking composite laminate sequence, [0°]4, [90o]4, [45o]4, [0o/45o]2s and [0°/90°]4s on the crack driving force, J-integral, of inclined cracked 2420-T3 aluminum plate. Furthermore, the effects of patch geometry, number of layers, single or double side patch and crack incline angle are described. The present results show that the patch has a high effect in case of a crack in pure mode I. Furthermore, the effectiveness of the composite patch is increasing with the crack length increases. Moreover, the efficiency of the composite patch has a high effect by changing the fiber orientation, the number of layers, and the single or double side patch.