Morikazu Takegaki

A New Feedback Method for Dynamic Control of Manipulators

Department of Mechanical Engineering, Faculty of Engineering SCience, Osaka University, Toyonaka, Osaka, 560 Japan A new approach to the dynamic control of manipulators is developed from the viewpoint of mechanics. It is /irst shown that a linear feedback of generalized coordinates and their derivatives are effective for motion control in the large. Next, we propose a method for task-oriented coordinate control which can be easily implemented by a micro-computer and is suited to sensor feedback control. The proposed method is applicable even when holonomic constraints are added to the system. Effectiveness of the proposed method is verified by computer simulation.

Middleware for distributed industrial real-time systems on ATM networks

We address the problem of middleware design for constructing ATM LAN based distributed industrial plant monitoring and control systems. In particular, we present a real-time client-server programming model based on a uniform ATM network. This model is being realized in our middleware called MidART. The middleware provides a set of industrial application specific but network transparent programming abstractions and application programming interface (API) that support individual application QoS requirements. In order to achieve on-demand transmission of plant data, we have developed a concept called selective real-time channels to be supported by MidART. We present the design and protocols of selective real-time channels and describe how QoS requirements of applications are guaranteed.

Acquisition and service of temporal data for real-time plant monitoring

Data sampled from plants are registered as temporal data, combined with time stamps. We developed a real-time data server which periodically acquires temporal data and transmits them to clients for graphic presentation. The real-time data server consists of multi threads scheduled based on the rate monotonic theory. This paper explains the design of a real-time data server. The prediction for schedulability of it based on the rate monotonic theory has been verified with an experiment on an actual system.<<ETX>>

Active transactions integrated with real-time transactions according to data freshness

Plants need both data acquisition without any loss and detection of state changes in restricted times. The paper proposes the active ring model for active real-time database systems which acquire data from industrial plants, provide the data for applications, and detect state changes to notify them to applications. The model incorporates the ECA mechanism into circular storage areas. In the ECA mechanism, conditions whose evaluation time is bounded are separated from others. The model is cognizant of data freshness. Since deadlines of transactions are set according to data freshness, the detection is integrated with the real-time acquisition. The paper includes an experimental result revealing that the active ring model is effective to provide service according to data freshness.

A new control strategy for nuclear power reactors

A new automatic direct digital control strategy for nuclear power reactors is presented. It is based on a simple control logic of comparison between the available time (the time for the error signal to disappear) and the required time (the time for the time derivative to match that of the target trend). The method aims to control the system to an acceptable state within a minimum time under a number of restraints. The control capability of the method is shown for two typical transients. This method is generally applicable to process control in which time-optimal control based on the maximum principle is sought.

New architecture of industrial systems with real-time ATM middleware

We propose a programming model, a real-time client-server model, for distributed real-time systems for monitoring and controlling plant. With the model we can make a system scalable in a flat architecture with an ATM network. The system can be scalable because it has no bottlenecks in plant data transmission as traditional systems has with their cyclic transmissions. On-demand transmission of plant data realizes this scalability. The architecture can be flat with the ATM network integrating various kinds of traffics transmitted separately in traditional systems. We also propose using our middleware which provides application program interfaces (APIs) based on the model and guarantees application-to-application QoS. In addition, to achieve on-demand transmission of plant data, we propose a concept of selective real-time channels. We show an example of an application with our middleware, a plant monitoring system with an operator station and a programmable logic controller.

Knowledge-based modeling of physical processes

Abstract We propose a knowledge-based modeling method to represent process dynamics for deriving control procedures and diagnosis rules. Our modeling method treats process characteristics as interactions of autonomous objects, corresponding to sub-components or units that form some local characteristic, and evaluates process dynamics as a sequence of equilibrium states of objects. To represent the characteristics of each autonomous object, we use structured frame-type data to represent state variables for each object, and rule descriptions to represent the numerical relations of autonomous objects with a combination of logical and numerical operations. We also show a method for constructing a control algorithm from evaluated data which uses fuzzy inference rules to interpolate the sequence of points around a fixed point. With fuzzy inference, complex characteristics with multiple inputs and multiple outputs can be easily presented in the form of simple IF-THEN rules

Real-Time Reactions in Supervisory Control According toData Freshness

Supervisory control systems in plants mustacquire data without any loss and react for state changes. Someof state change should be reacted in a real-time manner, whileothers may be notified in a best-effort manner. To implementa middleware which works as a server in supervisory control systemsin an acceptable cost, we value the data freshness which meanshow much time has passed from the occurrence of the data. Inthis paper, we present the Active Ring model whichincorporates the ECA mechanism into circular areas. With rulesusing only the latest data, the ECA mechanism realizes time-criticalreactions as firm real-time tasks. In addition to that, the rulestrigger best-effort notification which is realized as a softreal-time task. The middleware works in numerous plants for steelmill, water purifying, and tunnel ventilation. This paper includesan experimental result revealing that the ActiveRing model is effective to provide service according to the datafreshness.

Multimedia Capabilities in Distributed Real-Time Applications

Distributed real-time industrial control applications can benefit significantly from the incorporation of multimedia information into the control environment. Potential benefits of such systems include enabling more intuitive visualization of the state of the control process, resulting in improved quality and/or safety of the process, better decision making at both the management and supervisory operator levels, as well as distance collaborative planning, design and effective trouble shooting. Thus, the processing and analysis of different types of multimedia information provides a wider range of capabilities to different entities (e.g., operation, maintenance, training, and administration) within a company than is possible now. Recent advances in computer technology, high speed networks, high capacity storage and innovative sensors make it possible to realize such enhanced control systems. The goals of this chapter are to examine real-time control applications that can exploit multimedia capabilities so as to determine their requirements, to identify key research issues at the system and database levels, and to propose a generic architecture for these applications.

An advanced design support system for intelligent robots

To design intelligent robotic systems which are expected to execute various tasks dexterously in a complex and hazardous environment, it is necessary to provide flexible programming environments for designing intelligent functions of robots and the capability of realistic environmental simulation for evaluating the behaviour of robots in work space. This paper describes an advanced design support system for such an intelligent robots. The present design support system integrates knowledge engineering approach (object-oriented programming and production system) with 3-D graphics and an image processing technique (oct-tree method). It is emphasized that object-oriented approach plays a key role in the design of robotic systems. It is also discussed that the interactive graphic simulation and environmental information processing based on the oct-tree method are very effective for evaluation and verification of robot systems. The present design support system is applied to functional design of a robot system that works in a nuclear plant.