Prof. Dr. Joachim Holtz
Editor-in-Chief
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Prof. Dr. Joachim Holtz |
IEEE Transactions on Industrial
Electronics
Volume 44, Number 6, December 1997
Special Section on Neural Networks for Robotics
Abstract - In this paper, adaptive neural network control of robot manipulators in the task space is considered. The controller is developed based on a neural network modeling technique which neither requires the evaluation of inverse dynamical model nor the time-consuming training process. It is shown that if Gaussian radial basis function networks are used, uniformly stable adaptation is assured and asymptotically tracking is achieved. The controller thus obtained does not require the inverse of Jacobian matrix. In addition, robust control can be easily incorporated to suppress the neural network modeling errors and the bounded disturbances. Numerical simulations are provided to show the effectiveness of the approach.
Abstract - An intelligent controller which consists of an intelligent planner and an adaptive fuzzy neural position/force controller is proposed for a robot manipulator. The proposed controller deals with the human expert knowledge and skills for planning and control. In this paper, it is applied to the task of deburring with an unknown object. The effectiveness of the proposed controller is evaluated by computer simulations.
Abstract - This paper presents an Enhanced Feedback Error Learning Control (EFELC) strategy for a n degree-of-freedom robotic manipulator. It covers the design and simulation study of the neural-network-based controller for the manipulator with a view of tracking a predetermined trajectory of motion in the joint space. An industrial robotic manipulator, Adept One Robot, was used to evaluate the effectiveness of the proposed scheme. The Adept One Robot was simulated as a three-axis manipulator with dynamics of the tool (fourth link) neglected and the mass of the load incorporated into the mass of the third link. For simplicity, only the first two joints of the manipulator were considered in the simulation study. The overall performance of the control system under different conditions, namely trajectory tracking, variations in trajectory and different initial weight values were studied and comparison made with the existing Feedback Error Learning Control (FELC) strategy. The enhanced version was shown to outperform the existing method.
Power Electronics
Abstract - A low power, low cost, highly efficient Maximum Power Point Tracker (MPPT) to be integrated into a photovoltaic panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed to use an integrated MPPT converter as part of the PV panel. This proposed integrated MPPT is proposed to use a simple controller in order to be cost-effective. Furthermore the converter has to be very efficient in order to transfer more energy to the load than a directly coupled system. This is achieved by using a simple soft-switched topology. A much higher conversion efficiency at lower cost will then result, making the MPPT an affordable solution for small PV energy systems.
Abstract - Contactless power delivery systems for mobile loads use transformers comprising a core with a secondary winding sliding along an extended primary winding. The sliding transformer is identified as the most limiting component in the system and is analyzed by representing it as a special, multi-turn power transmission line. Two performance parameters, namely: the transmission line efficiency and system penalty factor are introduced. It is shown that fundamental restrictions may limit the attainable performance of the system. The inductance of the primary winding is identified as a parameter which can be optimized to improve the system performance. Experimental results for a short and a long stroke transformer are presented.
Abstract - Series connection of power devices has evolved into a mature technique and is widely applied in HVDC systems. Static and dynamic voltage balance is ensured by shunting individual devices with (dissipative) snubbers. The snubber losses become pronounced for increased operating frequencies and adversely affect power density. Capacitive snubbers do not exhibit these disadvantages but they require a zero-voltage switching mode. Super-resonant power converters facilitate the principle of zero-voltage switching. A high-voltage DC-DC power converter with multiple series-connected devices is proposed. It allows the application of non-dissipating snubbers to assist the voltage sharing between the multiple series-connected devices and lowers turn-off losses. Simulation results obtained with a circuit simulator are validated in an experimental converter operating with two series-connected devices. The behaviour of the series connection is examined for MOSFET's and IGBT's by both experimental work with a 2 kW prototype and computer simulation. Applications can be found in traction and heavy industry where the soft-switching converter is directly powered from a high-voltage source.
Abstract - The effect of dc flux on the core loss is examined for the practical range of power and frequency. Relevant core loss equations are derived and applied to an optimization algorithm to determine the minimum core loss at a given ratio s(dc flux density to ac peak flux density). It has been found that the curves of hysteresis loss density versus ratio of s exhibit a peak at a critical ratio. Below or above this critical ratio, the loss density decreases drastically. On the other hand, the curves of eddy current loss density versus ratio of s exhibits a minimum point at a critical ratio. Below or above this critical ratio, the loss desnity increases gradually.
Drive Control
Abstract - Robust speed control of a switched reluctance vector drive is presented in this paper. An approximate sliding mode input power controller and another feedforward sliding mode speed controller are combined with space voltage vector modulation. The resultant drive has rapid and robust speed response. In addition, a switched reluctance drive incorporating the proposed controller requires only one current sensor and can be implemented in a low cost 8 bit micro-computer and a few discrete integrated circuits. Furthermore, the controller does not require any off-line characterization of the motor or load characteristics and could easily be applied to switched reluctance motors with any number of phase windings. A 4 kW 4 phase switched reluctance drive is constructed to test the performance of the controller. The results show that a step response from 200 r/min to 1980 r/min needs only 2 - 3 seconds even when driving a high inertia load and that the speed error can be controlled below 1 % even under unknown and dynamic loads. It is concluded that modified sliding mode controllers are effective in dealing with the highly nonlinear characteristics of the switched reluctance drive system.
Abstract - A new minimum-time minimum-loss speed control algorithm for induction motors is suggested to obtain high performance as well as high efficiency under field oriented control with practical constraints on voltage and current. This algorithm utilizes a two stage control. In the transient stage, a maximum-torque control algorithm is utilized to get the minimum-time response. In the steady-state, a minimum-loss control algorithm is applied to improve the efficiency. Simulation studies show the performance of the proposed minimum-time minimum-loss control algorithm under field oriented control.
Signal Processing
Abstract - The ubiquitous super market checkout scanner is a well engineered and effective device. Existing scanners rely on simple and low cost signal processing to interpret bar code signals which imposes restrictions on the system noise power that they can tolerate. In this paper, we describe the relationships between engineering parameters of the system that limit reader performance. If the combined noise is Gaussian, we show that the reader error probability depends on a single parameter which we call a timing signal-to-noise ratio.
Abstract - This paper describes the pilot implementation of a local network by using a hybrid MAC-sublayer protocol (GIT-CSMA/CD) developed for hard real-time industrial Local Area Networks. This protocol outperforms standard CSMA/CD and token passing protocols as well as other hybrid protocols, in terms of mean and maximum packet delays versus throughput. Also, GIT-CSMA/CD offers bounded packet delay and a great degree of adaptation to the varying requirements imposed by the user applications. A seven-node pilot network was set up and its experimental performance evaluated. The implementation of the network node is based on the existing advanced microcontroller technology (INTEL 80C152 Communication Controller) and FPGA logic XILINX XC3190. The measurements carried out in real-time on a 1 Mbps LAN yielding reproducible results. The comparison between the experimental and the simulation results showed excellent agreement.
Abstract - The motivation of this paper is to provide a real-time compact device for inputting handwritten characters to mobile personal digital assistants (PDAs). A novel method for the recognition of on-line handwritten Chinese characters is presented, giving emphasis to the representation of the patterns using fuzzy logic. The information contained in a character, including shapes of individual strokes and their relative spatial relations, is examined by inference of fuzzy rule base, and the fuzzified representation are organized in a matrix structure. It is well-known that Chinese characters comprise a set of basic units, representing fundamental meanings. Hence, a unit extraction module is designed to search the possible units within characters. The input character object is recognized by a combination of units with the largest fuzzy confidence degree. The training capability, which provides the unit model set, is performed using the qualitative fuzzy c-means clustering algorithm. An experimental system is implemented that achieves a real-time recognition rate about 95% with a test set of 550 characters and 2 cases for each character written by 6 users. The experimental system has real- time recognition speed of average 0.5 sec/character. The presented approach shows two significant advantages over other methods: (1) Less training time and (2) Less storage required to store character models, that are two crucial factors in designing Personal Digital Assistant (PDA) devices for mobile communication.
Abstract - A vision-based vehicle guidance system for road vehicles can have three main roles: road detection, obstacle detection and sign recognition. The first two have been studied for many years and with many good results, but traffic sign recognition is a less studied field. Traffic signs provide drivers with very valuable information about the road in order to make it safer and to make driving easier. We think that traffic signs must play the same role for autonomous vehicles. They are designed to be easily recognized by human drivers mainly because their color and shapes are very different from natural environments. The algorithm described in this paper takes advantage of these features. It has two main parts: the first one, for the detection, uses color thresholding to segment the image and shape analysis to detect the signs. The second one, for the classification, uses a neural network. Some results from natural scenes are shown. On the other hand, the algorithm is valid to detect other kinds of marks that would tell the mobile robot to perform some task at that place.
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