Linear Vibration of the Rotary Plate Under Combined Excitations in Subsonic Airflow

Due to strong nonlinear, unsteady characteristics and the fluid–structure interaction effect, vibration analysis of blades under the excitation of the airflow is still one of the technical difficulties. In this paper, the accurate subsonic aerodynamic force is obtained through numerical simulation, and the aerodynamic coupling model of the rotary blade is established. The distribution of the aerodynamic force of the compressor blade under the unsteady airflow is focused on. The blade is modeled as presetting a presetting pre-twisted rotary cantilever plate. Dynamic frequencies of the plate, calculated by Chebyshev–Ritz method, are compared with frequencies calculated using the finite element method (FEM). Effects of different parameters on natural frequencies of the rotary plate are discussed. Based on von-Karman nonlinear geometric relation and the first-order shear deformation theory, nonlinear dynamic equations of the pre-twisted rotary plate under the combination of the centrifugal force and the aerodynamic are derived by utilizing Hamilton’s principle. Second-order ordinary differential equations are derived by applying the Galerkin method. Analytical solution of the dynamic deformation of the plate is presented and is compared with that produced by FEM. Results indicate the accuracy of the explicit presentation of the aerodynamic of the low-pressure compressor blade. Effects of the rotary speed, the thickness, the pre-twisted angle and the presetting angle on vibration characteristics of the warping blade are studied. Mode shape shift and frequency loci veering are discussed.

Comparative Evaluation on Performance Characteristics of an Impact Sprinkler with Nozzle-Dispersion Devicesand Rotary Plate Sprinkler

A set of nozzle and water dispersion devices were designed to obtain a desirable jet breakup and save water from an impact sprinkler (IS) at low pressure conditions. Comparative performance indicators were obtained for the commercial LP and IS sprinkler heads. Results show that under the same working conditions, the IS produced a large spray range and the water distribution in the middle of the spray range (R) was better than the LP. The best simulated uniformity from the IS was obtained for the combined spacing factor of 1.4*R and the combined uniformity was 4% larger than the LP. Considering the middle position of the spray range, the number and diameter of the droplets from the IS were larger than the droplets from the LP. However, in the end position of the spray range, the droplet diameters from the IS were quite smaller than the LP. Velocities from IS ranged between 0.2 and 6.4 m/s, while that from LP sprinkler were slightly higher ranging from 0.15 to 7.7 m/s at 150 kPa. Overall, introduction of the fixed dispersion device with a pointed tip profile combined with the 6 mm nozzle offered some advantages for the IS over the LP sprinkler at low-pressure conditions. Keywords: Dispersion device, Droplet distribution, Impact sprinkler, Low pressure sprinkler, Nozzle, Spray range, Uniformity.

The Performance of Mass Properties Measurement for Satellite’s Structural Model

This paper focuses on the capabilities of equipment known as Mass Properties Measurement (MPM) to calculate the center of gravity (CG) of a jig or an adaptor, which is used for mounting a structural model of Malaysian satellite, RazakSAT on POI-1000M Spin Balance Machine. The adaptor needs to be designed accurately to precisely accommodate the bolt sizes in both sides of the Device Under Test (DUT) side and the rotary plate side. In other words, the adaptor must be able to act as a good interface plate. A Malaysian research institute, SIRIM Berhad was chosen to undertake the design and manufacturing of the adaptor according to the specifications made by ANGKASA. The list of requirements of MPM should be considered during measurement to have optimum results, so that the satellite fixture onto the rotary table can be preceded for further calculations. Space Electronics (SE), the manufacturer for this MPM machine, has provided the control system for operators to calculate the required measurement such as CG, moment of inertia (MOI) and Product of Inertia (POI). Results confirmed that the simulation and experimental values are successfully obtained.

Kinematics and Interfacing of ModRED: A Self-Healing Capable, 4DOF Modular Self-Reconfigurable Robot

Modular self-reconfigurable robots (MSRs) are systems which rely on modularity for maneuvering over unstructured terrains, while having the ability to complete multiple assigned functions in a distributed way. An MSR should be equipped with robust and efficient docking interfaces to ensure enhanced autonomy and self-reconfiguration ability. Genderless docking is a necessary criterion to maintain homogeneity of the robot modules. This also enables self-healing of a modular robot system in the case of a failed module. The mechanism needs to be compact and lightweight and at the same time have sufficient strength to transfer loads from other connected modules. This research focuses on the design of a modular robot with four degrees of freedom (4DOF) per module and with the goal of achieving higher workspace flexibility and self-healing capability. To explain the working principle of the robot, forward kinematic transformations were derived and workspace and singularity analysis were performed. In addition, to address the issues of interfacing, a rotary plate genderless single-sided docking mechanism—RoGenSiD—was developed. The design methodology included considerations for minimal space and weight as well as for fault tolerance. As a result, this docking mechanism is applicable for multifaceted docking in lattice-type, chain-type, or hybrid-type MSR systems. Several locomotion gaits were proposed and bench-top testing validated the system performance in terms of self-healing capability and generation of locomotion gaits.

Structure Scheme Design of a Large Ultra-Precision Hydrostatic Rotary Table with a High Diameter-Length Ratio

This essay briefly introduces a structure scheme design of a high diameter-length ratio rotary plate. This structure scheme is unique from any well-known schemes. In this scheme, there is only one flat act as the working flat for both main thrust bearing and aux thrust bearing. It minimizes the faces which need lapping. At the same time, this scheme minimizes the number of assembling parts. So, it will be easier for this scheme to achieve high accuracy. This essay includes the process of design: calculation for bearings and schemes compare.

RoGenSiD: A Rotary Plate Genderless Single-Sided Docking Mechanism for Modular Self-Reconfigurable Robots

Docking mechanisms are an integral part of modular self-reconfigurable robot (MSR) systems, allowing multiple robot modules to attach to each other. An MSR should be equipped with robust and efficient docking interfaces to ensure enhanced autonomy and self-reconfiguration ability. Genderless docking is a necessary criterion to maintain homogeneity of the robot modules. This also enables self-healing of a modular robot system in the case of a failed module. The mechanism needs to be compact and lightweight and at the same time have sufficient strength to transfer loads from other connected modules. RoGenSiD is a rotary-plate genderless single sided docking mechanism that was designed to perform robustly and efficiently considering its application in unstructured terrains. The design methodology followed design for manufacture (DFM) and design for assembly (DFA) guidelines as well as considerations for minimal space and weight. As a result, this docking mechanism is applicable for multi-faceted docking in lattice-type, chain-type, or hybrid MSR systems. Bench-top testing validated the system performance.

Design of a manual device to measure ankle joint stiffness and range of motion

Background and Aim: Ankle joint stiffness and its range of motion (ROM) are commonly assessed to determine the appropriate mechanical characteristics required in an effective ankle-foot orthosis (AFO) prescription. The aim of this technical note is to present the design of a manual device that enables their convenient measurement in the clinical setting and to demonstrate its reliability.Technique: The manual device was designed with a torquemeter, a potentiometer, a steering wheel, a rotary plate, and a foot plate. The measurement of resistive torque at 0° (neutral), 5° (dorsiflexion) and 10° (dorsiflexion) ankle angular positions demonstrated the high reliability of the device with Intraclass Correlation Coefficient (ICC) (1,k) values over 0.97.Discussion: Quantitative measurement of ankle joint stiffness and ROM by this manual device would provide objective information that could potentially assist AFO prescriptions. A future study should investigate how to incorporate the measurement obtained from the device into the prescription of an AFO.

Design of an Automated Device to Measure Sagittal Plane Stiffness of an Articulated Ankle-Foot Orthosis

The purpose of this study was to design a new automated stiffness measurement device which could perform a simultaneous measurement of both dorsi- and plantarflexion angles and the corresponding resistive torque around the rotational centre of an articulated ankle-foot orthosis (AAFO). This was achieved by controlling angular velocities and range of motion in the sagittal plane. The device consisted of a hydraulic servo fatigue testing machine, a torque meter, a potentiometer, a rotary plate and an upright supporter to enable an AAFO to be attached to the device via a surrogate shank. The accuracy of the device in reproducing the range of motion and angular velocity was within 4% and 1% respectively in the range of motion of 30&dG (15&dG plantarflexion to 15&dG dorsiflexion) at the angular velocity of 10&dG /s, while that in the measurement of AAFO torque was within 8% at the 0&dG position. The device should prove useful to assist an orthotist or a manufacturer to quantify the stiffness of an AAFO and inform its clinical use.