A computer analysis of orientation devices for vibratory bowl feeders

Currently, vibratory bowl feeders are widely used in industry to feed small parts in assembly processes. The actual orientation of parts is achieved by various devices used in these feeders. However, each type of device performs only a limited function. The objective of this project was to develop a systematic approach which both analyses the geometrical and topological properties of parts designed in a CAD system and selects appropriate orientation devices to feed the designed parts.     

A novel approach to vibratory finishing: Double vibro-polishing

In most conventional vibratory finishing processes, the vibration flow is in the following order: vibratory motor, machine walls, and ultimately the media which impart finishing action to the components. The components are either freely floating or secured to a fixture in the bulk of media flow throughout the process. Commonly used fixtures are of the mechanical type where components are held on the fixture which is either rigidly bolted to the vibratory finishing machine or freely floating in the media. In this paper, a novel polishing method is introduced: double vibro-polishing. The polishing process deploys a vibratory fixture incorporated in a conventional vibratory finishing setup so that dual vibrations are induced on the components. Ti-6Al-4V workpieces are attached to a vibratory fixture which is immersed in a vibratory finishing trough containing plastic media. Two modes are compared to evaluate asperity changes: vibratory fixture in the “silent” mode which is representative of a mechanical fixture, and the “active” mode giving rise to dual vibro-polishing. Average surface roughness (R_a) is measured using a surface profiler every 15?min until 180?min of process time and the results are plotted. The vibratory fixture demonstrates improvement in the process times in terms of reaching the saturation R_a in a shorter period of time. Force sensors are incorporated onto the fixture to examine the reasons behind the faster finishing.     

Incorporating pattern recognition capability in a flexible vibratory bowl feeder using a neural network

Programmable parts feeders that can orientate most of the parts of one or more part families, with short changeover times from one part to the next, are highly sought after in batch production. This study investigates a suitable neural-network-based pattern recognition algorithm for the recognition of parts in a programmable vibratory bowl feeder. Three fibre-optic sensors were mounted on a vibratory bowl feeder to scan the surface of each feeding part. The scanned signatures were used as the input for the different neural network models. The performances of ARTMAP, ART2 and backpropagation neural network models were compared. The results showed that, among the three models, ARTMAP is deemed to be superior, based on the criteria of learning speed, high generalization and flexibility. The better performance obtained with the ARTMAP neural network is mainly the result of its online training and supervised learning capabilities.     

A computer-aided framework for the selection and sequencing of orientating devices for the vibratory bowl feeder

Correct part orientation has been the key to many successful automation applications, and often vibratory bowls were used. Traditionally, the design and tooling of the vibratory bowls are limited to a group of skilled experts. In this paper a feature-based framework for the automatic selection and sequencing of orientating devices is presented. A direct link between part representation and the selection and sequencing of modular orientating devices is provided by a spatial technique, in place of traditional CAD representation. Also described is the classification of a part's orientating features and classification of orientating devices. These two classifications are integrated into a knowledge-based system that will automatically generate sequences of modular orientating devices.     

The bowl phenomenon revisited

A novel method of analysing serial production lines has been developed. This method lets one compute the throughput rate of lines composed of dissimilar stations, as well as for a large class of distributions of station service times. Several distribution-free models of 3-station lines are presented. These models are used to compute the throughput rate of unbalanced lines in which the sum of the mean service times is constant. Results are shown as contour plots of constant throughput rate. The bowl phenomenon is reviewed in the light of this capacity to model with a greater degree of freedom.     

Some observations on the bowl phenomenon

Previous studies suggest that performance of a series system may be enhanced if those station(s) having smallest mean operation time requirement(s) and/or smallest variability are placed in the middle of the line. There has been considerable confusion relative to whether this ‘bowl phenomenon’ has to do with the placement of means, variances, or some combination of the two. The results of the current study show that the phenomenon observed is not related to an imbalance in means. Rather, it is associated with an imbalance in absolute variability. Furthermore, it is suggested that the bowl effect vanishes altogether in cases where a minimal level of in-process buffer stock is provided.     

Dynamic characteristics of vibratory gyroscopes

Although there have been test results on microgyroscope dynamic characteristics, quantitative results relating the dynamic properties to microgyro design and operating parameters are not yet available. In this paper, we study the dynamic characteristics of a vibrating wheel microgyroscope. In vibratory microgyroscopes, the mechanical structure is driven into oscillatory motion. Consequently, the angular velocity input to the sensor is multiplied by the periodic driven motion. In order to recover the angular velocity input from the sensor responses, a demodulation must by carried out. Therefore, the differential equation governing the gyro input and output is not time invariant. The frequency response for the time-variant linear system is obtained through the demodulated and low-pass filtered steady-state output to sinusoidal excitations. With further assumptions of large Q value and close frequency match between the driven mode and sense mode, we obtain a time invariant model for the microgyroscope which is much simpler to use in the design of the microgyroscopes.     

A review of vibratory gyroscopes

This paper describes the mechanical design of some vibratory rate gyroscopes. The principal commercial designs are identified and their operating principles are described. Only two designs based upon micromechanical methods of manufacture have been produced and these are still at an early stage of development. These designs are described and discussed     

The diffraction pattern of large aperture bowl transducers

A new examination has been made of the diffraction pattern in the vicinity of the focus, for large aperture concave bowl ultrasonic transducers. The study gives results which show a departure from those derived from optical theory, hitherto accepted. This departure increases progressively with increase in bowl aperture and leads to the expectation that large aperture ultrasonic microscopes will provide a resolution somewhat greater than indicated by classical theory.The study has also shown that the major part of the wave energy radiated by the transducer is confined near the focus within a cylindrical region, in which it is propagated as a plane wave. By a suitable choice of bowl dimensions and ultrasonic frequency the radius of this region may be made a fraction of a milimetre, while its length is several milimetres.From the realisation of the plane wave nature of propagation near the focus a technique has been developed for the determination of the ultrasonic velocity in samples of solids of very small volume of the order of 50 mm³.     

制动皮碗装配方向检测系统

汽车制动皮碗装配方向错误会使主缸密封性能不良,进而影响汽车制动性能。制动缸为半密封工件,成像较难,故使用锥面镜对安装好的皮碗全景成像。视觉成像中,皮碗方向不同,光的反射角度不同,具有不同特征,故配合NI Assistant图像处理技术编译图像处理算法,通过圆心检测、全景图像双线性插值法展开,矩形图像融合拼接、灰度值投影等算法处理图像,设定灰度和比例系数K判别皮碗方x向。测试结果准确率高,测试的200张图像中,仅误判一张,基本满足工业检测需求。     

Piezo actuated vibratory feeding with vibration control

This research investigated the effect of decoupling the motion of a conventional vibratory feeder in order to develop a one-axis vibratory sliding mode for feeding tiny delicate parts that could ultimately be adapted to two axes. This research investigated a new type of vibratory drive by employing a piezoelectric actuator. In a decoupled design, the action of the horizontal and vertical vibration would be separately controlled to achieve a desired part trajectory and consequently the feed rate of the part. A computer control scheme was used to develop voltage input waveforms to control these actuators to produce movements that cause the parts to move forward relative to the track and overcome backsliding and other inefficient feeding motions. There are two advantages to this type of design. First, it can handle the parts in a more controlled manner by keeping them in constant contact with the track while maintaining a high conveying speed. This results in good protection for fragile parts. Secondly, this concept results in feedback control schemes that could allow the computer to adjust the drive waveforms to optimize feeder performance. Due to the non-sinusoidal nature of driving waveforms, the higher harmonic components can excite undesired deformation of the responding trajectory. A self-tuning control based on dynamic system identification was employed to counteract the higher harmonic effect. A one-dimensional hardware model is built and experiments were conducted to verify the precision and feasibility of the controlled actuation.     

Study of corrective abrasive finishing for plane surfaces using magnetic abrasive finishing processes

On the basis of ordinary plane magnetic abrasive finishing, a finishing method is proposed that can improve the flatness of a plane work-piece. In this method, ...     

振动沉桩过程的动力学仿真分析

振动沉桩过程是一个非常复杂的过程,其复杂性源于土的动力性能和桩－土接触面的动力接触行为。应用Ｄ－Ｐ准则,借助ＡＮＳＹＳ软件,建立桩－土系统有限元模型,选取合适的桩－土系统参数,并得出在该参数下的桩位移曲线。改变激振力振幅、频率及土的内摩擦角、粘结力和压缩模量等参数值,得出相应参数下的桩位移曲线。通过对比原参数下的桩位移曲线与改变参数后的桩位移曲线,得出激振力幅值、频率以及土的刚度和阻尼对沉桩速度和沉桩量的影响。