Patrick S. K. Chua

Least-squares calibration method for fringe projection profilometry considering camera lens distortion

By using the least-squares fitting approach, the calibration procedure for fringe projection profilometry becomes more flexible and easier, since neither the measurement of system geometric parameters nor precise control of plane moving is required. With consideration of camera lens distortion, we propose a modified least-squares calibration method for fringe projection profilometry. In this method, camera lens distortion is involved in the mathematical description of the system for least-squares fitting to reduce its influence. Both simulation and experimental results are shown to verify the validity and ease of use of this modified calibration method.

Novel design and development of an active feeder

Purpose – This paper aims to focus on the novel design and development of an automatic feeding system which is capable of feeding cylindrical parts which are fragile and powdery in nature and possess asymmetrical features such as a groove near to one end.Design/methodology/approach – It is an active feeder, performing its task without having to reject any feeding part by performing active orientation of feeding parts that are in the undesired orientation. This design incorporating active orientating capability is aimed at 100 percent feeding efficiency. The system is controlled and driven by a programmable logic controller and electropneumatics.Findings – System evaluation results showed that the average jam rate is below 5 percent and the percentage of correctly orientated parts is above 95 percent. With enhancement and fine tuning, the system could become a very useful feeder for industry in the future.Research limitations/implications – The scope of this paper focuses on presentation of the design conc...

Fault Detection of Water Hydraulic Motor by Demodulated Vibration Signal Analysis with the Hilbert Transform and Genetic Algorithm

The vibration signals analysis from the water hydraulic motor is the most modern technique for fault detection of water hydraulic motor. The machine’s residual life is estimated by the detection of the fault presence and type at an earlier stage for the adequate plan of maintenance. The most important components in the impulsive vibration signal spectra are the rotational frequency and its harmonics as well as sidebands due to modulation phenomena. This paper studied the fault detection of fluid machines by the demodulated frequency components of the periodic impulse vibration signal. We apply the Hilbert transform to demodulate the characteristic envelope of the periodic impulsive signal to show the fundamental frequencies. The adaptive spectrogram is optimized to get the optimal parameters to show the characteristic frequencies of the Hilbert transform-based envelope of the vibration signals. The results show that it is applicable and effective to fault detection of water hydraulic motor by analyzing the demodulated frequency components of the periodic impulsive signal.

Feature Extraction, Optimization and Classification by Second Generation Wavelet and Support Vector Machine for Fault Diagnosis of Water Hydraulic Power System

Abstract The work described in this paper investigates the fault diagnosis of water hydraulic motor by the optimization and automatic classification of the feature values. The second generation wavelet for the vibration signals analysis of the water hydraulic motor was proposed to extract the feature values. The new optimization method by bi-classification support vector machine (SVM) was proposed to select the optimal feature values based on a rank criterion and the algorithm was developed here. In order to classify the conditions of the pistons used in the hydraulic motor, a two-level structure based on the multi-classification was developed in this work. The multi-classification method of SVM for the fault diagnosis of a piston crack was investigated. The winner-takes-all scheme was studied. The results of the classification were found to be successful.

Fault diagnosis of water hydraulic actuators under some simulated faults

Abstract Water hydraulics captured the imagination of engineers some 2500 years ago and recently it has revived to become a powerful alternative in areas where the environment and health are of great concern. Previously, this field of knowledge suffered some setbacks as technology was still at its developing stage, but with better tolerances and the availability of better materials, this technology is now a reality. This paper focuses on the fault diagnosis of the condition of hydraulic actuators working on the principle of tap water hydraulic power systems. Two common actuators were explored, namely a water hydraulic cylinder and a water hydraulic axial piston motor. Possible real-life faults were simulated on the actuator’s internal component. The cylinder was operated with worn piston or rod seals whereas the motor has worn capstan and piston shoes in place. These actuators were operated to capture their unique vibration signals in their faulty states to be compared with their ‘healthy’ condition state. Both actuators were loaded in steps for trend observation in the vibration signatures. Results show that, in general, there is a change in vibration signals, flow rate and average operation duration when more load is added to the actuators. If a fault has occurred internally, it will also correspond to another change in the above parameters in the spectra plotted. With this knowledge, LabVIEW software can be written to set warning levels that will trigger an alarm when a fault is impending.

Simulation software for parts feeding in a vibratory bowl feeder

This paper describes the development of three-dimensional (3D) computer simulation software to simulate parts feeding and orienting in a vibratory bowl feeder. A mathematical model of part motion and the interaction of the part with the orienting mechanism were developed. Based on the mathematical model, a 3D-simulation software has been developed using Java. The key technology involves 3D object modelling and collision detection, which were developed with Java 3D API. The simulation software can perform dynamic simulation of part motion and the interaction of simple parts with the designed orienting mechanism, therefore enabling the reliability and capability of the design to be assessed prior to fabrication. The computer simulation was verified by carrying out physical experiments in the laboratory. Good agreement between the results of the computer simulation and experiments was obtained.

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.

Symbolic pattern manipulation of Karnaugh-Veitch maps for pneumatic circuits

Pneumatics continue to play a vital role in low-cost automation. The designing of pneumatic control circuits has to date been a slow manual process. This paper describes the computational symbolic manipulation of the Karnaugh-Veitch (KV) map which is the heart of the prototype expert system called PNEUMAES. The symbolic manipulation of a KV map is governed by two sets of generic rules for signal flow plotting and for logic equation minimisation applicable for complex pneumatic circuits. As the complexity of the circuit increases, the symbolic manipulation of a KV map leads to the combinatorial explosion problem. Because of this problem, PNEUMAES can only automatically generate pure pneumatic circuit design equations which will yield minimised circuit configuration for up to four cylinders with auxiliary control valves. A case study is included and issues and problems relating to the implementation of the KV map are discussed. Symbolic and sub-symbolic learning approaches are suggested as a means by which the search space of the symbolic patterns of the KV map can be pruned.

Testing and evaluation of water hydraulic components by acoustic emission and wavelet analysis

In condition monitoring and fault diagnosis of machinery, vibration analysis is the major method and wavelet analysis is widely implemented. The acoustic emission (AE) method is another important and effective signal in fault diagnosis of mechanical systems. In this paper, the AE signal is applied to diagnose the piston condition of the water hydraulic motor in a water hydraulic system. The AE signal is obtained under different flow rates and torques. The wavelet-based signal processing technique is used to analyze the fluid-borne vibration and structure-borne vibration (acoustic signal). The spectrum based on wavelet analysis is effective in analyzing the acoustic signals under specific frequency ranges, compared with the conventional power spectrum density (PSD). The results show root mean square (RMS) of the wavelet-based acoustic signal analysis is very effective for the fault diagnosis of piston cracks under the different flow rates and torques.

Object‐oriented heat transfer software application

A heat transfer solver has been developed using an object‐oriented approach, which allows the heat transfer problem to be set up and solved easily with ease and user‐friendliness. The solver is developed as a Window application using Java programming. It can solve several types of heat transfer problems such as one‐dimensional steady‐state heat conduction through a plane wall, cylinder, or sphere, with temperature, heat flux, and convective boundary conditions (BCs), one‐dimensional transient heat conduction through a plane wall, lumped system analysis, extended heat transfer surface, forced convection over a flat plate, and radiation.