Chanat Ratanasumawong

Utilization of synchronous averaging for inspection of tooth surface undulations on gears (localization of nonmesh harmonic components to individual gear)

Cyclic undulation of the gear tooth surface is one of the important sources of gear noise and vibration. It has been known that vibration caused by this source can appear at the nonmesh harmonic frequency components (ghost components). As there are no relationships between the frequency of this vibration and any gear specifications, the gear noise source is hard to detect. This paper proposes the utilization of the synchronous averaging technique for diagnosis of the source of nonmesh harmonic vibration components on a gear pair, and shows the possibility of using this technique for inspection of tooth surface undulation. The method for practically applying this technique is discussed in detail. Results demonstrated in the form of spectrum showed good agreement with the undulation assessed from precise tooth surface measurement over the whole surface of every tooth. The effect of the direction of the arrangement of cyclic undulation on tooth surface and gear vibration is also discussed in this paper. Finally the limitation to the synchronous averaging technique was discussed with respect to gear ratio.

Design, Fabrication and Evaluation of a Novel Electro Thermal Micro-Gripper for Handling of Head Gimbal Assembly

A development of a novel electro thermal micro-gripper for handling of Head Gimbal Assembly (HGA) is an ultimate goal of this study. The scope of this study covers a design, fabrication and performance evaluation of the electro thermal micro-gripper. ANSYS software was used to examine the magnitude of tip displacement, exerting force and induced stress to investigate the mechanism’s viability for handling of HGA. Electroplating of nickel was employed to construct the micro-gripper’s mechanisms with three different sizes, and their displacement and exerting force were then examined. From the experiments, each mechanism deflected between 100 to 220 μm while the exerting force was over 200 mN at 25 oC above room temperature. Therefore, the results suggested that the new electro thermal micro-grippers are viable for the HGA handling application.

Estimating Gear Tooth Surface Geometry by Means of the Vibration Measurement: Distinction of the Vibration Characteristics of Gears With Tooth Surface Form Error

Tooth surface measurement is an important way to verify the quality of produced gears. To reduce inspection time and cost, only a few tooth profiles and traces on some teeth are inspected. Measured data are not likely representatives of all gear teeth because errors may occur in assembly procedure and affect tooth contact condition. Frequently, tooth surface measuring data cannot show contact condition and used to predict gear vibration accurately. Field inspection method whose measured results relate directly to the messing condition is required. This paper derives the relationship between meshing vibration components and the common gear tooth surface geometries of helical gears. The tooth surface geometries considered here are lead crowning, profile convex, pressure angle error, and bias-in modification. The polar plot representation, which plots meshing components in a complex plane, is proposed here to distinguish vibration characteristics of gears with various tooth surface forms. It is found that the vector of the second order of meshing component is valuable for classifying the type of tooth surface geometry.

An Alternative Method for Evaluating Gear Tooth Surface Geometry Based on Synchronous Average of Vibration of a Gear Pair

Low noise and vibration in the gearing operation is always required. Inspection by measuring gear tooth surface is a common way to investigate the source of noise and vibration. However many problems probably occur during assembling procedure, or are attributed to the bearing condition of the tooth pairs that certainly cannot be detected when inspecting each gear separately. In this paper, the newly developed method to evaluate gear tooth surface geometry based on vibration measurement is proposed. This method can be done in field. Moreover measured vibration also relates directly with the tooth bearing condition. In this method, vibration of the gear pair is measured and processed by the synchronous averaging technique to extract only the signal of interest. Then the system transfer function obtained experimentally is applied to the averaged-meshing vibration to estimate vibration excitation. Consequently tooth surface geometry directly relating with the vibration excitation can be inversely evaluated. The effectiveness of this method was verified by many experiments done by measuring the vibration of helical gears with various kinds of tooth surface forms at various operating conditions. The evaluated vibration excitations were plotted in the polar coordinate. The changes of amplitude and phase angle of the second order components were found to be suitable and could be used as an indicator to evaluate gear tooth surface form.Copyright

Utilization of Synchronous Averaging of Vibration for Diagnosis of Gear System to Estimate Tooth Error

Generally, gear vibration behavior has base frequencies equal to meshing frequency and its harmonics. But it has become known that slight undulation even on ground gear surface sometimes generate peculiar vibration behavior that is non-integer order of meshing frequency, and it is called ‘ghost noise’. In the normal cases, the gear pair that is the source of vibration can be located by considering mesh frequencies of each gear pair and their harmonics. But if ghost noise components exist, it becomes difficult to detect which gear pair is the source. Therefore diagnosis method to detect ghost noise source with measuring vibration is required. In this study, we proposed the utilization of synchronous averaging to distinguish the source of ghost noise components. With this method, we could separate the effect of driving and driven gear from each other. The estimation results with synchronous averaging were verified with precise tooth surface measurements.Copyright

Parallel-Axis Gear Design Methodology for Minimization of Power Loss and Its Effect on Vibration Characteristics

Gear tooth strength is mainly considered in gear design to ensure the ability to transmit power. With the design process, various sets of gear parameters are probably selected to meet the tooth strength. However the efficiencies of various designed gears are different. Improper gear parameter selection probably makes the gear power loss increase significantly. In this paper, the design methodology to minimize gear power loss is presented. A spur gear selected from a catalogue is used as the reference gear. Then several gears with various parameters but having the ability to transmit the same load are designed. The power losses of the designed and the reference gears are estimated by the sliding loss model, hence the minimum power loss gear is able to choose from the various designed gear sets. Both analytical and experimental results show that to minimize gear power loss along with keeping loading capacity, pressure angle should be increased and module should be reduced. The effect of this design methodology on vibration characteristics is also investigated by measuring the vibration attributed to the sample gear sets. It is found that the helical gear having large pressure angle, wide face width and having helix angle about 10 to 20 is favorable, since it has more capability to transmit load, lower power loss and also lower vibration than the reference spur gear.

Utilization of Tooth Contact Pattern in a Gear Meshing Model for Estimation of Sliding Loss in a Parallel-Axis Gear Pair

The utilization of tooth contact pattern in a gear meshing model for estimation of sliding loss in a spur and helical gear pair is presented in this paper. The photo of tooth contact pattern taken after the gear operation is used as the database to generate the simplified tooth contact pattern. Then the simplified contact pattern is used along with the gear meshing model to estimate the sliding loss of a gear pair. Experiments are done to verify the results. The estimated results from the presented method agree well with the experimental results. The presented method is able to estimate the effect of the helix angle on the sliding loss correctly whereas the estimation without using the data of tooth contact pattern cannot.