K.K. Tan

Distributed fault detection in industrial system based on sensor wireless network

In metal cutting processes, an effective monitoring system, based on a suitably developed scheme or set of algorithms can maintain machine tools in good condition and delay the occurrence of tool wear. In this paper, an approach is developed for fault detection based on a distributed system. Firstly, identifying of sensor instrumentation system is responsible for the signal processing and the system fault information. Secondly, the sensor wireless networks are used to transmit the data (lower layer) to or receive the commands from the computer center (top layer). Thirdly, the computer center at the top layer will monitor the overall system and generate the alarm signals or the commands when the faults occur.

Geometrical Error Modeling and Compensation Using Neural Networks

This paper describes an approach based on neural networks (NNs) for geometrical error modeling and compensation for precision motion systems. A laser interferometer is used to obtain the systematic error measurements of the geometrical errors, based on which an error model may be constructed and, consequently, a model-based compensation may be incorporated in the motion-control system. NNs are used to approximate the components of geometrical errors, thus dispensing with the conventional lookup table. Apart from serving as a more adequate model due to its inherent nonlinear characteristics, the use of NNs also results in less memory requirements to implement the error compensation for a specified precision compared to the use of lookup table. The adequacy and clear benefits of the proposed approach are illustrated via applications to various configurations of precision-positioning stages, including a single-axis, a gantry, and a complete XY stage

Application of vibration sensing in monitoring and control of machine health

In this paper, an application for monitoring and control of machine health using vibration sensing is developed. This vibration analyzer is able to continuously monitor and compare the actual vibration pattern against a vibration signature, based on a fuzzy fusion technique. More importantly, this intelligent knowledge-based real-time analyzer is able to detect excessive vibration conditions much sooner than a resulting fault could be detected by an operator. Subsequently, appropriate actions can be taken, say to provide a warning or automatic corrective action. This approach may be implemented independently of the control system and as such can be applied to existing equipment without modification of the normal mode of operation. Simulation and experimental results are provided to illustrate the advantages of the approach taken in this application.

Developments in Visual Servoing for Mobile Manipulation

A new trend in mobile robotics is to integrate visual information in feedback control for facilitating autonomous grasping and manipulation. The result is a visual servo system, which is quite beneficial in autonomous mobile manipulation. In view of mobility, it has wider application than the traditional visual servoing in manipulators with fixed base. In this paper, the state of art of vision-guided robotic applications is presented along with the associated hardware. Next, two classical approaches of visual servoing: image-based visual servoing (IBVS) and position-based visual servoing (PBVS) are reviewed; and their advantages and drawbacks in applying to a mobile manipulation system are discussed. A general concept of modeling a visual servo system is demonstrated. Some challenges in developing visual servo systems are discussed. Finally, a practical application of mobile manipulation system which is developed for applications of search and rescue and homecare robotics is introduced.

Optimization of Mechatronic Design Quotient using Genetic Algorithm in Vibration Controllers for Flexible Beams

Due to their extensive utilization in engineering designs, various vibration controllers have been investigated with design specifications in mind. The optimization of vibration controller designs is a complicated multi-criteria problem. In this paper, the mechatronic design quotient (MDQ) approach and genetic algorithm (GA) are coupled together to determine this optimal design solution. The MDQ is presented to formulate an evaluation function for the passive vibration controller design of flexible beam structures, and the GA is then used to maximize this function so as to achieve a design solution with the highest MDQ value. For comparison, both the MDQ performance of passive vibration controller design using linear dampers and active vibration controller design using a linear quadratic regulator are provided. The latter is used as the performance benchmark to evaluate the optimal design solution of the former. Experimental results show that the linear dampers design with the proposed method can achieve similar performance to an optimal active controller.

Online Parameter Estimation and Compensation of Preisach Hysteresis by SVD updating

Abstract Preisach model can be used to describe the hysteresis in smart actuators. In this paper, online parameter identification by singular value decomposition (SVD) updating is presented for Preisach hysteresis. Firstly, SVD in least squares sense is used to obtain the pseudo inverse. However, it is time-consuming to compute singular values for large matrix, and PE condition is not always satisfied. Secondly, the SVD of large matrix is transformed to low order thin matrix, then, based on the initial result of offline SVD, online SVD updating is given by rotating basis which needs to be revised when new data is large. Finally, inverse Preisach feedforward is used to compensate the hysteresis.

Iterative learning algorithm with a quadratic criterion for linear time-varying systems

Abstract A novel iterative learning controller for linear time-varying systems is developed. The learning law is derived on the basis of a quadratic criterion. This control scheme does not include package information. The advantage of the proposed learning law is that the convergence is guaranteed without the need for empirical choice of parameters. Furthermore, the tracking error on the final iteration will be a class K function of the bounds on the uncertainties. Finally, simulation results reveal that the proposed control has a good setpoint tracking performance.

Neural network control design for a rigid-link electrically driven robot

Abstract In this paper, a back-stepping scheme for rigid-link electrically driven (RLED) robot systems is proposed. A two-step controller is presented: the first step is a virtual controller, while the second step is an actual one. A neural network is used to approximate the unknown non-linear dynamics in the system. The stability can be guaranteed by using a rigid proof. A simulation is used to illustrate the effectiveness of the proposed algorithm.

Adaptive friction compensation with a time-delay friction model

Abstract This paper presents a new compensation technique for a time-delay friction model that captures the effect of frictional memory. The proposed control utilizes a proportional-derivative (PD) control structure and an adaptive estimate of the friction force. Specifically, a radial basis function (RBF) is used to compensate the effects of the non-linearly occurring parameters in the friction model. Simulation results verify the theory and show that the method can significantly improve the tracking performance of a control system in which it is used.

Fabrication of Electronics Devices with Multi-material Drop-on-Demand Dispensing System

One of the key engineering applications of drop-on-demand (DoD) micro-dispensing system is to fabricate functional devices. Diverse materials with wider range of properties are needed in this process. To satisfy this requirement, multiple print heads on micro level fabrication are preferred to perform multi-material dispensing task. This paper proposes a micro dispensing system with two print heads (micro valve print head and piezoelectric print head), since each type of print head has advantages and limitations over the others in specific fabrication. This proposed system has demonstrated its capability for printing resistor and capacitor. The functionalities of these components are tested such as IV characterization for resistor, and frequency characteristics for printed capacitor, followed by a detailed discussion and in-depth analysis. Our experimental results have approved that micro DoD dispensing is a feasible way to fabricate passive electronic devices.