Mass Properties Measurement

Adequate design of tree harvesting equipment requires reliable estimates of centers of gravity and moments of inertia for full trees and tree-length stems. Several prediction models were developed for both centers of gravity and moments of inertia based on the theory of geometric solids. These models were fitted to center of gravity and moment of inertia estimates that were derived from stem dimension and weight measurements on loblolly pine (Pinus taeda L.) trees. The models were compared, and the best prediction equations for center of gravity and moment of inertia of tree-length stems were identified. Application of standard multiple regression methods resulted in a moment of inertia prediction model with a slope parameter estimate that had a sign opposite to that indicated by a theoretical model. Ridge regression and nonlinear regression were used to fit moment of inertia prediction models having coefficient signs consistent with those predicted by the theoretical model. The parameter estimates obtained by nonlinear regression were selected since they conformed more closely to properties of the theoretical moment of inertia model. FOR. SCI 39(2):260-274.

Baby weight and length measurement system has been designed based on ultrasonic and load cell sensors with data storage using MySQL database and website interface. This research aims to produce a baby weight and length measurement system with microcontroller NodeMCU ESP32. The system is designed with an ultrasonic sensor HC-SR04 and four half-bridge load cells of 50 kg. The ultrasonic sensor works on the piezoelectric and inverse piezoelectric principles, while load cell sensors work on strain gauge principles. An ultrasonic sensor measures body length, while a load cell sensor measures body weight. According to the Ministry of Health of the Republic of Indonesia’s regulations, this system also has an LCD 20×4 to display measurement and nutritional status assessment results. The experiment used four doll objects with different lengths and weights. This research shows that the ultrasonic sensor HC-SR04 used in this research has an average error of 0.494% in length measurement. The load cell sensor and HX711 ADC used in this research has an average error of 0.949% in weight measurement. The designed system automatically assesses the nutritional status and stores the measurement result and nutritional status in the database to be displayed on the website.

Determination Of Rigid Body Characteristics From Time Domain Modal Test Data

Comparing the influence of Roll-Over Protective Structure type on tractor lateral stability

To increase the accuracy of the large size mass property measurement system, a method of error compensation based on kinematics model is presented. The kinematics equation of the machine is established with D-H transform matrix and the relation between the measurement error and geometric parameters error is established. For some parameters which can be measured accurately, the error of them can be ignored, which simplify the calibration equation and calculating. To speed up the calibration process, optimal measure poses, which realize high positioning accuracy with small point number, are selected using particle swarm optimization algorithm(PSO). The relationship between pose of the calibration and fitness function is established. Experimental studies are performed to demonstrate the importance of PSO to the efficiency of calibration. Through the pose error compensation the max errors of the centroid, the moment of inertia and the product of inertia are reduced to approximately 10%, 50% and 20% respectively.

Physical properties and roll decay of David Taylor Model Basin (DTMB) Model 5720, a 23rd scale free running model of the research vessel (R/V) Melville, are documented with uncertainty estimates. Properties include mass, vertical center of gravity (VCG), longitudinal center of gravity (LCG), and transverse center of gravity (TCG), and moments of inertia (MOI) for roll and pitch, transverse metacentric height (GMT), and natural roll period, Tn. Previous analysis has been expanded with additional details and uncertainty estimates. Results are based on measurements with the latest technology. The significant results for model properties are as follows: length 3.3652 ±0.0010 m (±0.030 %), mass 233.21 ±0.46 kg (±0.20 %), LCG 1.6061 ±0.0011 m (±0.067 %) aft of bow, VCG 0.2640 ±0.0017 m (±0.63 %) above keel, GMT 47.76 ±0.61 mm (±1.3 %), roll radius of gyration 0.2329 ±0.0042 m (±1.8 %), and pitch radius of gyration 0.8434 ±0.0024 m (±0.28 %). The roll period in calm water was independent of the Froude number (Fr) and initial roll angle (a). At Fr = 0, 0.15, 0.22, the average roll period was 2.2298 ±0.0040 s (±0.18 %) for 76 runs, all Fr, and all initial roll angles. The initial roll angle variation was 3° to 25°. The natural roll period was 2.139 ±0.041 s (±1.9 %). The decay coefficient data were accurately approximated by a plane in three dimensions with Fr and initial roll amplitudes (a) as the independent variables. Examples are provided that show the average values for a single roll decay event from the logdecrement method are the same as the values by the curve fitting method within the uncertainty estimates.

The project deals with the structural design and analysis of mounting structure for assembling of electronic packages in a flight vehicle section. The flight vehicle consists of various sections assembled to form an integrated vehicle. Different types of electronic packages to meet the requirements are assembled in different flight vehicle sections based on the flight vehicle configuration. One such type of flight vehicle section needs to be assembled with different electronic packages. The packages have to be rigidly mounted on a mounting structure in the flight vehicle section. The launch of a flight vehicle can be one of the most rigorous loads environments for which to design hardware. The high random vibration loads imparted on vehicle by the electronic packages during launch create an adverse design requirement that all hardware have a natural frequency greater than that of the vehicle, in order to avoid damage and failure due to dynamic coupling. Maximizing natural frequency is generally accomplished by creating as stiff and lightweight a design as possible. However, designing for the resultant high loads also requires a high strength intermediate structure for mounting the various components and subassemblies to the vehicle structure. These two opposing design requirements drive an optimization between a lightweight and high strength structure. The project comprises of design and analysis of the mounting structure. The mounting structure has to be designed to withstand the loads generated by the electronic packages. It also includes the design of mounting plate and brackets to withstand the given loads using CAD and CAE tools. Unigraphics software is used for modeling the flight vehicle section, packages and the mounting plate with brackets. The mounting plate and brackets are imported to ANSYS software for structural analysis. The mounting plate with brackets is applied with specified loads in different flight conditions like Pitch, Yaw and Roll moments. A finite element model was created to manually iterate several aspects of the design, such as geometric characteristics like thicknesses and fillet radii, to analyze the effects on weight and stress and converge on a successful design .The project elucides in detail the methodology adopted for the analysis of mounting structures for flight vehicles. configuration. These have to be mounted to withstand aerospace loads both static and dynamic. The main parts of the anatomy of an airframe are fuselage, the wing and the empennage. Each of the is in turn composed of various structural members. The area of interest in the current project is on the fuselage or the body of the aircraft in which in which electronic subsystems are mounted. In general, flight vehicle can be a air craft or rocket or missile. Mass properties are vital for the flight vehicle to travel in desired trajectory. The mass properties of the flight vehicle are Weight, Center of gravity and Moment of Inertia. Weight is the force generated by the gravitational attraction of the earth on the model rocket. The mass (and weight) is actually distributed throughout the rocket and for some problems it is important to know the distribution. But for rocket trajectory and stability, we only need to be concerned with the total weight and the location of the center of gravity. The center of gravity is the average location of the mass of the rocket. The flight vehicle or Aerospace vehicle has three modes of motion viz. Pitch, Yaw and Roll. These terms frequently used in the flight vehicle are explained below. The below figure shows the three modes of motion. Figure 2 Three modes of motion in a flight vehicle

For balanced cars, to achieve high-speed and stable operation, two efforts should be made. The first is to make the center of gravity of the car model as low as possible, which is conducive to upright stability. The second is to make the quality as concentrated as possible. Make the vehicle's steering more flexible and reduce the vehicle's moment of inertia. At the same time, the approach angle and departure angle of the car are very important considerations, because the running speed of the car model requires the car model to maintain a certain forward inclination to obtain acceleration. When the car model goes uphill, it also needs to consider the impact of the slope. Hanging the chassis requires a certain distance from the ground while lowering the center of gravity. The battery is the heaviest piece in the entire car. The location of the battery almost determines the height of the center of gravity, the size of the moment of inertia, and the departure angle of the approach angle. In order to reduce the noise of the car to the accelerometer and gyroscope, the sensor should be installed as low as possible.

A reliable and sensitive in situ method for measuring polyp size is fundamental for growth studies of colonic polyps. A measuring probe inserted through a colonoscope can give a visual assessment of polyp diameter, and from a picture of the polyp the area of the polyp on the picture can be calculated by computerized analysis. To test the reliability and sensitivity of these two in situ measurements, 43 colonic polyps (mean diameter, 8.5 mm; range, 4-20 mm) removed by snare diathermy resection were examined. The maximal diameter was measured, and two Polaroid pictures taken of each polyp. After polypectomy each polyp was subjected to extracorporeal reassessment of diameter and measurement of weight and volume. By computerized analysis of the pictures the following variables were estimated: 1) area of the polyp on the picture; 2) largest diameter; 3) maximum width 90 degrees on the largest diameter; 4) maximum distance from centre of gravity; and 5) minimum distance from centre of gravity. Results showed good correlation between diameter measured in situ and after removal (r = 0.93), diameter raised to the 3rd power and weight (r = 0.93), and also to volume (r = 0.77). Area analysis compared with weight was less good (r = 0.72). A very high correlation was demonstrated between weight and volume (r = 0.99). We conclude that the measurement of diameter in situ with a measuring probe is sensitive and somewhat more reliable than computerized analysis of size. The present 3-year follow-up and intervention study will show which of the two methods is preferable for evaluation of polyp growth.

Early childhood talent identification sport programs are needed to decide the potential of children in certain sports. It is expecting that children will be able to maximize sports achievements according to their talents. To find out a human's talent in sports, several parameters can be used for a measurement. One of them is the anthropocentric test, which is a series of processes for measuring the dimensions of the human body with in the form of body height and weight. Based on the results of measurement analysis, children will be able to identify their sport talents. Therefore, a website-based height and weight measurement system was developed that is able to provide information on measurement results and talents identification. The development of this tool uses the ESP 32 Dev Kit Module as a micro controller, an ultrasonic sensor for height sensors and a load cell for a weight sensor. The data are sent to the database contained on the website for further processing and analysis based on the measurement results of talent in the sports field. The measurement website page can display measurement results and identify type of talent that belongs to the child. Based on the results of measurement and data analysis, the accuracy of the tools for measuring body height were 98.7% and body weight were 99.5%, while the precision of the tools were 98.6% for body height and body weight were 97.4%.

In a mass measurement system using relay feedback of displacement, an object to be measured was guided mechanically by leaf springs to restrict its motion to a single translation. Such a mechanical guide produces restoring force that affects the estimation of mass based on the measured periods of oscillation. However, such effects on mass measurement have not been studied sufficiently. In this research, an experimental device is designed and manufactured to verify the analytical results experimentally. The nonlinearity of the spring is compensated by feeding back the deflection of the spring. Mass measurements are conducted with this device. The measured results support the analytical results.

A description is given of the development of a dynamic biped model for use in determining the amount of performance resources required to perform a predetermined gait task. The gait task is specified by identifying the desired cadence and stride length, and the performance resources predicted by the model are the joint torques, displacements, and velocities associated with the hip, knee, and ankle. Measurements of the subject's height, weight, and limb segment lengths are used to individualize the model parameters to the subject. Values for segment density, mass moment of inertia, and center of gravity are obtained from the literature. Because the model is developed using a functional unit approach, it should be useful for comparing the amount of performance resources required for the task (from the model) with isokinetic strength data describing the amount of performance resources available to the subject. The initial development of the model and the preliminary validation procedure using data from the literature are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Objectives: Although side-impact sled studies have investigated chest, abdomen, and pelvic injury mechanics, determination of head accelerations and the associated neck forces and moments is very limited. The purpose of the present study was therefore to determine the temporal forces and moments at the upper neck region and head angular accelerations and angular velocities using postmortem human subjects (PMHS). Methods: Anthropometric data and X-rays were obtained, and the specimens were positioned upright on a custom-designed seat, rigidly fixed to the platform of the sled. PMHS were seated facing forward with the Frankfort plane horizontal, and legs were stretched parallel to the mid-sagittal plane. The normal curvature and alignment of the dorsal spine were maintained without initial torso rotation. A pyramid-shaped nine-accelerometer package was secured to the parietal-temporal region of the head. The test matrix consisted of groups A and B, representing the fully restrained torso condition, and groups C and D, representing the three-point belt–restrained torso condition. The change in velocity was 12.4 m/s for groups A and C, 17.9 m/s for group B, and 8.7 m/s for group D tests. Two specimens were tested in each group. Injuries were scored based on the Abbreviated Injury Scale. The head mass, center of gravity, and moment of inertia were determined for each specimen. Head accelerations and upper neck forces and moments were determined before head contact. Results: Neck forces and moments and head angular accelerations and angular velocities are presented on a specimen-by-specimen basis. In addition, a summary of peak magnitudes of biomechanical data is provided because of their potential in serving as injury reference values characterizing head-neck biomechanics in side impacts. Though no skull fractures occurred, AIS 0 to 3 neck traumas were dependent on the impact velocity and restraint condition. Conclusions: Because specimen-specific head center of gravity and mass moment of inertia were determined, and a suitable instrumentation system was used for data collection and analysis, head angular accelerations and neck forces and moments determined in the present study can be used with confidence to advance impact biomechanics research. Although the sample size is limited in each group, results from these tests serve as a fundamental data set to validate finite element models and evaluate the performance and biofidelity of federalized and prototype side-impact dummies with a focus on head-neck biomechanics.

The conceptual design and flight controller of a novel kind of quadcopter are presented. This design is capable of morphing the shape of the UAV during flight to achieve position and attitude control. We consider a dynamic center of gravity (CoG) which causes continuous variation in a moment of inertia (MoI) parameters of the UAV. These dynamic structural parameters play a vital role in the stability and control of the system. The length of quadcopter arms is a variable parameter, and it is actuated using attitude feedback-based control law. The MoI parameters are computed in real-time and incorporated in the equations of motion of the system. The UAV utilizes the angular motion of propellers and variable quadcopter arm lengths for position and navigation control. The movement space of the CoG is a design parameter and it is bounded by actuator limitations and stability requirements of the system. A detailed information on equations of motion, flight controller design and possible applications of this system are provided. Further, the proposed shape-changing UAV system is evaluated by comparative numerical simulations for way point navigation mission and complex trajectory tracking.

Nine low-lying ${\mathrm{O}}_{\mathit{n}}^{+}$ states of $^{20}\mathrm{Ne}$ and their possible rotational bands have been studied by employing the isomorphic shell model which is a hybrid between conventional shell model and the liquid drop model in conjunction with the nucleon finite size and which in addition uses no adjustable parameters. The configurations of six out of these nine ${\mathrm{O}}_{\mathit{n}}^{+}$ states have an \ensuremath{\alpha}-planar structure when, for each set of four closeby nucleon average positions (two protons and two neutrons), possessing the same principal quantum number n and forming an instant \ensuremath{\alpha}-like particle, the center of gravity is considered. The novelty of the present study is focused on the fact that the axis of rotation and the number of rotating nucleons inside the same rotational band may change in such a way that the relevant moment of inertia increases monotonically in steps forming for each step a new branch of the band. Up to five such branches have been found and each time the moment of inertia of the last of them approaches the rigid body limit, creating superdeformed bands. The coexistence of a superdeformed band and of lower deformation bands include several states with the same ${\mathit{I}}^{\mathrm{\ensuremath{\pi}}}$ value. Two rotational bands are introduced for the first time and the model predictions of states in all cases are very close to the experimental data. Another important feature of the present study is that two different configurations possess identical binding energy (the maximum among all possible configurations) and are assigned, by 50% each, to the g.s. of $^{20}\mathrm{Ne}$. This has been verified by successfully employing many observables and results of other models. \textcopyright{} 1996 The American Physical Society.