Robot simulator in TIPS/Geometric Simulator

With the growth of factory automation, the need for off-line robot programming is increasing rapidly. Off-line programming requires a robot simulator. This is the reason for the development of a TIPS/GS (Geometric Simulator), accompanied by a robot simulator. TIPS/GS has been developed as a project in the TIPS Research Association. The goal of this project is to extend the functions and applications of the solid modeler TIPS-1. Four simulators (i.e. the assembly simulator, engineering, NC simulator and robot simulator) have been developed for these extended applications.

The robot simulator described in this paper has the following special features:

• • When a robot motion is prescribed by the VAL-G language, the result can be seen on a CRT display in several patterns.

• • High-speed dynamic display which can almost keep up with real-time movements.

• • A shaded as well as wire-frame picture is used for the high-speed display entioned above.

• • Supported by the solid modeler, any robot and environment can be used with this system.

• • The preparation of a precise interference checker based on an analytical methods.

This paper is a report on the development of the robot simulator.     

Application of AI in software and information engineering

Methodologies already exist for information systems analysis and design (e.g. SSADM, JSP, Merise, etc.) and supporting tools, namely, CASE (Computer Aided Software Engineering) and RDBMS (Relational Database Management System) and/or 4GL tools. All of these tools contain a data dictionary at the core of certain facilities.

In the underlying research and in this paper, the following questions need to be addressed:

• —How can the capability of a recently available data dictionary be enhanced with some knowledge-based modules?

• —What would be the architecture of such a system, based on the data dictionary of some CASE tools?

• —How can the informal and formal modelling approach information system design be combined?

• —What sort of knowledge-representation techniques would be suitable for the different tasks during the analysis and the design of the system?

The system outlined here would work as an intelligent assistant and workbench supporting the developer, but not as an automatic programming environment.     

Advanced process monitoring—a major step towards adaptive control

Adaptive Control (AC) of machine tools requires many kinds of measured input data. The more information about the complex metal cutting process that can be obtained, the better the process can be controlled.

The paper describes an Adaptive Control Optimization (ACO) system for turning operations. The system continuously chooses Optimal Cutting Data (OCD), taking into account both economical criteria and technical limitations.

The system operates at three different levels:

• • Advanced Process Monitoring

• • Adaptive Control Constraint (ACC)

• • Adaptive Control Optimization (ACO).

Two commercial monitoring systems perform process monitoring. In addition, five independent measurement systems have been developed.

A dedicated vision system has been installed in the lathe to measure the tool flank wear between cuts. The flank wear data are utilized to predict the tool life. Based upon these predictions economical optimum cutting data can be calculated at the ACO level.

To obtain in-process real-time control of the metal cutting process the cutting forces are measured during machining. The forces are measured with conventional piezoelectric force transducers which are located between the turret housing and the cross-slide. The measured force signals are processed by a dedicated microcontroller at the ACC level and cutting data adjustments are fed back to the machine control.

A vibration measurement system, which either can be connected to an accelerometer or use the dynamic force signal from the piezoelectric force transducer, is part of a vibration control module at the ACC level. An ultra-fast signal processor performs the signal analysis.

The remaining two measurement systems—a high frequency tool signal analysis system and a power spectra analysis system—are mentioned in the paper but not further discussed.

Finally, the paper deals with how the strategies at the three different levels will be combined, in order to form an AC system. The monitoring tasks will always reside in the background and be activated if any failure occurs. The ACO subsystem will act as a path-finder and suggest cutting data. The active control tasks will, however, be carried out at the ACC level.     

Development of an integrated information model for computer integrated manufacturing

The development of an FDBS is integrate existing CIM components by using a bottom-up development process. The components used in this paper do not support any kind database management. The integration of those components into a federation may be done by using two general approaches [3]:

• • Migration of the files to a DBMS

• • Extend the file system to support DBMS-like features

Both migration and extension of the file system are costly solutions and actually depend on existing capabilities of the components. Problems may occur when the federated schema becomes too large. The schema might be split up into smaller federated schemes (loosely coupled FBDS).     

Advanced CMOS speech synthesizers

Employing an updated C²MOS (clocked CMOS) technique, two types of speech synthesizer LSI circuits, based on the Parcor (partial correlation) and the ADM (adoptive delta modulation) methods, and recording watch system, are introduced and described.

These LSI circuits and system have several functions

• • The new Parcor LSI circuit has the circuits needed by the Parcor synthesis algorithm. It has a 64 kbit speech data ROM, output low pass filter and preamplifier. Using only this LSI circuit, 30 s to 60 s of speech can be synthesized.

• • The new ADM LSI circuit has encoding and decoding circuits, a 64 kbit speech data ROM and RAM control circuit. The record and synthesis system can be easily constructed with this LSI circuit and RAM.

• • The recording watch system consists of the watch LSI circuit with the ADM system and the analogue LSI circuit.

In the Parcor system, various high quality and low data-rate speech outputs are obtainable. The ADM system is applied for recording and synthesizing. By applying these systems to meet market needs, it is possible to achieve good cost performance in a simple system.     

Health effects of vibration in agriculture - Pilot for an epidemiological study

A pilot study has been conducted to prepare for an epidemiological study into the effects of vibration on tractor drivers. The reason for the study is that, despite a large volume of existing data on health and vibration (over 43,000 exposed workers having been studied) there is still no good basis for estimating dose-response relationships between vibration and health. There have been three main difficulties:

• - Many studies have not measured vibration, or have not measured it thoroughly enough.

• - Confounding variables such as posture have not been entirely controlled for, because well-matched control groups do not exist.

• - Health data have tended to be binary incidence data rather than continuous scale data, reducing the sensitivity of the studies.

The pilot study has produced procedures to overcome these difficulties.     

Assessment of the slip-resistance of floors in the laboratory and in the field: Two complementary methods for two applications

There are numerous methods available to measure the slip-resistance of different floor-coverings. The INRS has developed two distinct methods for the evaluation of the slip resistance of a given surface within the framework of its studies on the prevention of slips:

• - One method that can be used to compare new surfaces. It uses a static device developed at the INRS and it is based on the evaluation of a coefficient of dynamic friction between a sample of a new oiled surface and an elastomer. This method is well-adapted to the needs of standardisation work;

• - Another method that can be used to evaluate slippage in the field where the surfaces are often worn and polluted with a specific product. It uses a portable device developed in Sweden and it is based on the continuous evaluation of a coefficient of dynamic friction over a variable distance between the surface to be tested and an elastomer.

These two methods which present well-correlated results are described in this publication, and their distinctly different uses will be underlined.     

Parallelising large irregular programs: an experience with Naira

Naira is a compiler for Haskell, written in Glasgow parallel Haskell. It exhibits modest, but irregular, parallelism that is determined by properties of the program being compiled, e.g. the complexity of the types and of the pattern matching. We report four experiments into Naira's parallel behaviour using a set of realistic inputs: namely the 18 Haskell modules of Naira itself. The issues investigated are:

• Does increasing input size improve sequential efficiency and speedup?

• To what extent do high communications latencies reduce average parallelism and speedup?

• Does migrating running threads between processors improve average parallelism and speedup at all latencies?

 

Applications of power series in computational geometry

A number of algorithms are presented for obtaining power series expansions of curves and surfaces at a point. Some results on the radius of convergence are given. Two applications of series are given:

1. • for curve tracing algorithms, where a truncated series is used to approximate the curve of intersection of two surfaces

2. • to define nth degree geometric continuity, for arbitrary

Some issues of structure and control for linear time-invariant systems

The objective of this paper is to emphasise the role played by particular structures in the solution of some control problems. The so-called “structural approach” relies on various indicators of dynamical systems such as, for instance, finite and infinite zeros, kernel indices, …. The fundamental invariance properties of these structures under the action of some transformations groups (e.g. feedback) are at the origin of their key role. Structural solutions to “classical” control problems, such as disturbance rejection, model matching and non-interaction are now rather well known: zeros at infinity play a role in the existence of “proper” solutions, while finite (invariant) zeros allow for the characterisation of “fixed poles”, whose location in the complex plane gives answer to pole placement limitations (including stability). Among the recent contributions to this structural approach, a particular attention is here devoted to:

- “Partial” versions of some of these control problems: The control objective only concerns a finite number of (and not necessarily all) the first Markov parameters of the transfer function matrix of the controlled system (e.g. to be zero for disturbance rejection or model matching, to be diagonal for non-interaction). Some interesting new issues in the dual context of failure detection are also sketched.

- Generalised solutions: Based on proportional and derivative feedback laws, with new issues in the context of systems with variable internal structures, and also for systems with delays.

Geometric concepts, such as invariant and almost invariant subspaces, and algebraic counterparts, such as factorisations on some special rings, are intermediary tools which support the characterisations of those particular structures and which allow for a structural treatment of the considered control and/or observation problems.

The results are here presented without proof: references are given to previous published results (in most cases in books and journals which are easily available), and some simple examples are used to illustrate non-standard notions (among which systems with variable internal structure, and time domain left invertibility).

Most of the results here presented rely on long and intensive collaborations between the author and various colleagues.     

A high speed gaze control system based on the Vestibulo-Ocular Reflex

Stabilizing the visual system is a crucial issue for any sighted mobile creature, whether it will be natural or artificial. The more immune the gaze of an animal or a robot is to various kinds of disturbances (e.g., those created by body or head movements when walking or flying), the less troublesome it will be for the visual system to carry out its many information processing tasks. The gaze control system that we describe in this paper takes a lesson from the Vestibulo-Ocular Reflex (VOR), which is known to contribute to stabilizing the human gaze and keeping the retinal image steady. The gaze control system owes its originality and its high performances to the combination of two sensory modalities, as follows:

• a visual sensor called Optical Sensor for the Control of Autonomous Robots (OSCAR) which delivers a retinal angular position signal. A new, miniature (10 g), piezo-based version of this visual sensor is presented here;

• an inertial sensor which delivers an angular head velocity signal.

We built a miniature (30 g), one degree of freedom oculomotor mechanism equipped with a micro-rate gyro and the new version of the OSCAR visual sensor. The gaze controller involves a feedback control system based on the retinal position error measurement and a feedforward control system based on the angular head velocity measurement. The feedforward control system triggers a high-speed “Vestibulo-ocular reflex” that efficiently and rapidly compensates for any rotational disturbances of the head. We show that a fast rotational step perturbation (3° in 40 ms) applied to the head is almost completely (90%) rejected within a very short time (70 ms). Sinusoidal head perturbations are also rapidly compensated for, thus keeping the gaze stabilized on its target (an edge) within a 10 times smaller angular range than the perturbing head rotations, which were applied here at frequencies of up to 6 Hz in an amplitude range of up to 6°. This high standard of performance in terms of head rotational disturbance rejection is comparable to that afforded by the human vestibulo-oculomotor system.     

A survey of simple transfer-function derivations from high-order state-variable models

The problem of the derivation of simple transfer function models from high order state variable models is reviewed. Methods of reduction are classified according to whether they involve

1. (a) the computation of the time or frequency responses

2. (b) the derivation, as an intermediate step, of a transfer function which is the ratio of two polynomials, the denominator being of the same order as the state variable model, or

3. (c) a set of characterising functions.

Particular reduction methods considered are those based on fitting the step or frequency responses, on determining the intermediate, high order transfer function and reducing it by continued fraction expansion and on fitting the moments of the impulse response. An example illustrating these methods is given. The form of the simple model, the criteria of goodness of fit and the practical difficulties involved in the use of these methods are discussed.     

Finite element programs based on general programming systems

This article describes the advantages and inconveniences with a finite element programming system, i.e. blocks of routines already thoroughly tested, which has to be built together by a programmer to a finite element program. This program may be a tailor-made program to fit a special problem or a general purpose finite element program.

The programming system used as an example in this article consists of

1. *NORSAM—finite element programming system

2. *DASA — pre- and postprocessors

3. *ELLIB—element library

Together they form a complete set of subroutines from datageneration through the necessary routines for matrix manipulation to presentation of results, including the multilevel superelement technique.

Reference to finite element programs applying the programming system concept, is given at the end of the article. Among others, programs for buckling, elasto-plastic analysis of 3-dimensional membranes and solids, nonlinear pipeline problems, acoustic field problems and transient heat conduction in solids are developed. The multilevel superelement technique has been applied in several of these application programs.

The concept of the programming system gives undoubtedly a large saving of time and resources and has proved to be more reliable than conventional methods when developing finite element programs.     

A comparison of standards for software engineering based on DO-178B for certification of avionics systems

Certification of avionics software is an increasingly important subject, since more and more avionics systems in future aircraft will be software equipped. The DO-17813 standard provides guidelines for software certification. Re-use of software is emerging, partly enabled by the integrated modular avionics concept, and imposed by a reduction of life-cycle costs. Re-use, however, requires re-certification or certification of software that was not developed according to DO-17813.

The DO-178B standard is specially developed to provide a certification basis for avionics software, without going into details of the software development process. Other standards focus on software engineering aspects. We have used the DO-178B standard as a common basis for comparison with DOD-STD2167A (military), ESA PSS-05-0 (space), and IEC65A(Secretariat)122 (industry). Comparison topics include:

• • life cycles;

• • prescribed documentation;

• • configuration management;

• • verification and validation;

• • quality assurance.

All standards prescribe the software development process, emphasizing specific aspects in a certain area of interest. The results of our investigation will assist in understanding the rationale behind several standards, and can be used for:

• • certification according to DO-17813 of software that was developed using another standard;

• • certification of software using DO-17813, in concert with another standard.

     

On the complexity of ω-type Turing acceptors

Turing machines are considered as recognizers of sets of infinite (ω-type) sequences, so called ω-languages. The basic results on such ω-type Turing acceptors were presented in a preceding paper. This paper focuses on the theory of deterministic ω-type Turing acceptors (ω-DTA's) which turns out to be crucially different from the ‘classical’ theory of Turing machines. It is shown that there exists no ω-DTA which is universal for all ω-DTA's. Two infinite complexity hierarchies for ω-DTA's are established, the ‘states hierarchy’, corresponding to the number of states in the machine, and the ‘designated sets hierarchy’, corresponding to the number of designated sets of states used in the recognition. Concrete examples of ω-languages characterizing each of the complexity classes are exhibited. Two additional examples of interesting ω-languages are presented:

1. (i) An ω-language which is ‘inherently non-deterministic’, i.e. can be recognized by a non-deterministic Turing acceptor but by no deterministic acceptor.

2. (ii) An ω-language which cannot be recognized even by a non-deterministic Turing acceptor.

The above examples are constructed without using diagonalization. Oscillating ω-DTA's, i.e. ω-DTA's which are allowed to oscillate on ω-inputs, are also considered and are shown to be strictly more powerful than non-oscillating ω-DTA's, yet strictly less powerful than non-deterministic ω-Turing acceptors.     

Driver performance modelling and its practical application to railway safety

This paper reports on the development and main features of a model of driver information processing. The work was conducted on behalf of Network Rail to meet a requirement to understand and manage the driver's interaction with the infrastructure through lineside reminder appliances. The model utilises cognitive theory and modelling techniques to describe driver performance in relation to infrastructure features and operational conditions. The model is capable of predicting the performance time, workload and error consequences of different operational conditions. The utility of the model is demonstrated through reports of its application to the following studies:

Research on the effect of line speed on driver interaction with signals and signs.

Calculation of minimum reading times for signals.

Development of a human factors signals passed at danger (SPAD) hazard checklist, and a method to resolve conflicts between signal sighting solutions.

Research on the demands imposed on drivers by European train control system (ETCS) driving in a UK context.

The paper also reports on a validation of the model's utility as a tool for assessing cab and infrastructure drivability.     

Scheduling flow shops in the environment of multi-functional machine tools

The concept of virtual machine tool (VMT) is introduced in this paper to specify machining resources of multi-functional machine tools. A two-level model for makespan minimization in a flow shop is developed in multi-functional machine tool environments. The model is first optimized with an Hopfield neural network to find the optimal processing sequence for components to visit all the necessary VMTs. Secondly, according to a set of shop floor control rules, the VMTs for components machining are matched with real machine tools. This procedure is driven by the events taking place in components machining, such as the arriving or the finishing of a component. Numerical experiments are conducted in a number of flow shop scheduling problems up to 8×8 and the mean relative optimizing rate is employed to assess the results of numerical experiments.     

An element for static, vibration and buckling analysis of thick laminated plates

A conforming finite element formulation of the equations governing composite multilayered plates using Reddy's higher-order theory is presented. The element has eight degrees of freedom, u₀, v₀, w, ∂w/∂x, ∂w/∂y, ∂²w/∂x∂y, γ_x, γ_y, per node. The transverse displacement of the present element is described by a modified bicubic displacement function while the in-plane displacements and shear-rotations are interpolated quadraticly. The element is evaluated for its accuracy in the analysis of static, vibration, and buckling of anisotropic rectangular plates with different lamination schemes and boundary conditions. The conforming finite element described here for the higher-order theory gives fairly accurate results for displacements, stresses, buckling loads, and natural frequencies.