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.     

A practical procedure for conceptual design and testing of machine tool structure

This paper discusses the initial development of a machine tool and its structure (concept, calculation, design) and the verification of the prototype. The topics studied include two issues: static rigidity and dynamic stability. For static rigidity several experiments and modelling studies using the finite element method have been carried out in order to identify the model parameters. In this way differences between models of bolted joints, slideways and the cross-section of the structural elements have been determined. The model is formed by design documentation and later verified through experiments on the prototype of the machine. The approach is different in the case of dynamic stability. The model is not made on the basis of design documentation or static calculations, but by experiments performed on the prototype. This relates to an oriented transfer function; parameters are determined by fitting experimental transfer function curves. With this model, the stability is analyzed under different machining conditions. Specific features of this methodology are as follows:

• • The finite element method is used for qualitative comparison of different machine tool structure concepts during the conceptual and design stages. Only after completion of the prototype may the parameters of the prototype model be adjusted for the purpose of obtaining quantitative indicators.

• • Dynamics are analyzed by parameter identification of the oriented transfer function model. The dominant degree of freedom is naturally selected by experiment and not from hypotheses about the behavior of structures obtained from mathematical manipulations such as expansion of the model according to the finite element method. If necessary another machine tool structure may be modelled; in this way hypotheses are drawn about the stability of the reconstructed prototype.

Such a procedure has been applied and verified on the machine tool structure of a horizontal machining center. Results for static rigidity and dynamic stability have been obtained from the model and experiments performed on the prototype. The following techniques have been used:

• • finite element method for qualitative identification of static behavior,

• • self-excitation of the machine,

• • digital signal processing on the FFT basis,

• • smoothing of curves and digital filtration,

• • function fitting of the transfer function (modal analysis),

• • coefficient calculus and oriented transfer function,

• • stability assessment of the fitted model under different machining conditions, and

• • modelling of the regenerative machining effect by cutting.

Necessary tests have been done by instruments required for the use of the above techniques.

Such a combined static-dynamic criteria procedure for structuring a machine tool enables efficient follow-up of all results and facilitates necessary future expansion, the utilization of universal equipment, the combination of modelling and experiments, and the synthesis of simple models of the examined machine with behavior identical to the machine. The well-known machining system dynamic stability theories are applied to such models.     

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

Progress in the prevention of falls caused by slipping

Initial research by the INRS showed the importance of biomechanical factors in the causes of accidents by slipping. Dynamic friction was shown to be far more significant than static fraction. The measuring procedure which has been developed does not provide a model of walking or slipping but a physical measurement giving the same ranking as subject evaluation methods.

Systematic measurements show the effect on slip resistance of the material used and the configuration of the sole. Following publication of these results, manufacturers have improved the slip resistance of shoes. An internationally acceptable method (ISO) should, however, be developed so that slip resistance, which is such an important factor in accident prevention, can be given as much attention as other features of the sole.

Scientific research on the psychophysiology of equilibrium on slippery surfaces is needed, as is applied research on friction with lubricated elastomers and on-site research into floor-surface friction.     

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 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.     

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.     

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.     

An on-chip micro-friction tester for tribology research of silicon based MEMS devices

An on-chip micro-tribotester has been developed to investigate the friction and wear properties on side contacting surfaces of single crystal silicon that is most widely used in usual microelectromechanical systems actuators. The device is fabricated with standard bulk silicon process and bonding technology based on parameters that have been theoretically calculated to get the stiffness and friction forces. In this device, two comb shuttles are used. One comb shuttle is used to contact the friction surfaces under a certain normal load. The other comb shuttle moves back and forth to provide relative motion between the two friction surfaces. The tested two surfaces are the top surface of an anchor with rounded end and the lateral surface of a beam that has been connected to the two comb shuttles. Tribology experiments on the etched silicon surfaces that are side contacted have been carried out. Friction coefficients testing results suggest that dynamic friction coefficient is about 0.31–0.33 and the obtained static friction coefficient increases with the decrease of normal force. Wear experiment indicates that oxidation happens between the rubbing surfaces during the course of the testing. Wear debris is collected as agglomerates because of the function of adhesion force and water vapor and the agglomerates that are collected on top and lateral surfaces are of different shapes.     

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).     

Fuzzy multiple attributes and multiple hierarchical decision making

A procedure is proposed to solve the multiple attributes and multiple hierarchical system under fuzzy environment. The approach is based on:

1. (1) fuzzy representation;

2. (2) hierarchical performance evaluation structure,

3. (3) gradient eigenvector method for rating the fuzzy criteria weighting, and

4. (4) using the max-min paired elimination method for aggregation.

To illustrate the approach, an example on the evaluation of teaching performance in higher education is solved.     

Development and validation of a novel portable slip simulator

The objective was to develop, construct and validate a portable device suitable for measurements of pedestrian slip resistance in situ. The developed device proved to be precise enough and easy to use. The dynamic coefficient of friction (DCOF) values measured by it showed strong correlation (r> or = 0.990, p < 0.001) with the values measured by the force platform used as a reference. In addition, the measured DCOF values were in good consistency with those obtained when using the older laboratory device of the Institute, the slip simulator. Based on the use of the new, developed device it can be concluded that accurate friction measurements with actual footwear can be performed even with a moderate-sized but portable device. The developed slipmeter will be used to measure slipperiness of various walking surface conditions, e.g. at different work places and in walkways, in the near future.     

Flat Dry Elastomer Adhesives as Attachment Materials for Climbing Robots

In this paper, flat elastomers are proposed as an attachment material for climbing robots on less than a few micrometer-scale rough surfaces due to their energy-efficient, quiet, and residue-free characteristics. The proper elastomer is chosen by the use of the current adhesion, friction, and peeling elastomer-contact-mechanics models. Then, adhesion and friction properties of the chosen dry flat-elastomer thick films (Vytaflex-10) are characterized on acrylic and smooth and rough glass surfaces for variations in preloads, speeds, contact times, and elastomer thicknesses. A climbing robot with four-bar-based legged-body kinematics is designed and fabricated as simple and lightweight as possible to demonstrate the feasibility of the elastomers as attachment materials on relatively smooth surfaces. The robot utilizes a passive alignment system to make the footpads parallel to the surface on light contact, a peeling mechanism to minimize the detachment vibration, and a passive tail to minimize the pitch-back moment. Experimental results showed that the robot can climb stably on vertical, smooth surfaces in any direction and can walk inverted for a limited amount of time.      

A MEMS Device for Studying the Friction Behavior of Micromachined Sidewall Surfaces

A microelectromechanical system device fabricated by deep reactive ion etching for friction characterization was developed with single-crystal silicon in this paper. Two orthogonally placed electrostatic comb-drive actuators were adopted to apply the normal load and generate the tangential motion. A sensing plate for sliding contact and a driving plate with two bumps designed for the Hertzian contact are included in the testing device. With an image processing technique developed, experimental displacement data were extracted from the captured video frames. A quasi-static stick–slip model was developed to predict the transitions between static and kinetic friction at the contacting sidewall surfaces. Both static and kinetic friction coefficients can be determined by using this model, and these measured results are shown to be insensitive to errors in the calculation of the electrostatic forces. The measured displacements of the driving and sensing plates are in good agreement with the trend predicted by the model. Based on the Hertz theory, the contact silicon interface has been found to be in an elastic regime at the scale of the designed bumps. With the aid of the quasi-static stick–slip model, a saturation phenomenon of the kinetic friction at the sidewall surfaces was observed while the normal load was increased. $hfill$[2007-0302]      

Observation of the floor surface topography changes in pedestrian slip resistance measurements

This study is concerned with the changes of the floor surface topography in the early stage of repetitive wear rubbings and the relationships between slip resistance properties and operationally defined geometric characteristics of the floor surfaces. It was assumed that: (1) alterations in surface topography will be associated with changes in the DFC; and (2) wear process will be accompanied by changes in surface topography. For the analysis of initial characterization on the surface topography, specially prepared, dry and clean metal and perspex specimens were chosen. The surface profiles of the fresh and rubbed flooring specimens were recorded using a laser scanning confocal microscope. From the profile ordinate data read at 1 μm intervals, a number of surface roughness parameters – centre line average, root-mean-square roughness, maximum height, maximum mean peak height, maximum mean depth, and absolute average asperity slope were calculated using a computer program. The skew and the kurtosis of the statistical distribution of each surface profile were also computed. The results indicate that the asperity height and the maximum mean depth were significantly reduced after the friction tests. The average slope of asperities was the parameter that most highly correlated with the dynamic friction coefficient. The analyses also showed that the surface parameters underwent large variations initially, but subsequently these changes were less marked, which was explained by the transition from unsteady-state friction to steady-state friction. These results found that slip resistance properties between the shoes and the floor counterfaces were greatly influenced by the manner in which the geometry of the floor surface was modified. It was suggested that measurement of changes in the surface geometry provides additional information on the analysis of slip resistance and could usefully be reported with friction measurements.

Relevance to industry

Slipping and falling accidents are a major ergonomic and safety concern in the workplace and the general community. Prevention of slip hazard has focused on designing “slip resistant” footwear and floor surfaces. This study is primarily concerned with the understanding of friction and wear mechanisms from a tribological point of view. A tribological approach may provide additional useful information about slip resistance performance.     

The role of friction in the measurement of slipperiness,Part 1: Friction mechanisms and definition of test conditions

Friction has been widely used as a measure of slipperiness. However, controversies around friction measurements remain. The purposes of this paper are to summarize understanding about friction measurement related to slipperiness assessment of shoe and floor interface and to define test conditions based on biomechanical observations. In addition, friction mechanisms at shoe and floor interface on dry, liquid and solid contaminated, and on icy surfaces are discussed. It is concluded that static friction measurement, by the traditional use of a drag-type device, is only suitable for dry and clean surfaces, and dynamic and transition friction methods are needed to properly estimate the potential risk on contaminated surfaces. Furthermore, at least some of the conditions at the shoe/floor interface during actual slip accidents should be replicated as test conditions for friction measurements, such as sliding speed, contact pressure and normal force build-up rate.     

An optimal gas-fired heating system

Utilizing a prescribed system configuration, this paper discusses the mathematical models of the system components used and formulates a method for controlling a domestic heating system in accordance to a prescribed criterion. The optimal problem treated is one of reducing the room temperature deviation from a prescribed reference value to zero, while at the same time minimizing the value of some predetermined performance or cost functional J. The development proceeds in essentially five steps.

1. (a) The development of the mathematical models for each of the elements of the heating system;

2. (b) Combining the mathematical models into a form which is suitable for the application of optimization techniques;

3. (c) Defining an optimization criterion which incorporates the main objective for minimizing room temperature variations with respect to a prescribed reference temperature;

4. (d) Choosing the optimization technique best suited for the problem;

5. (e) Constructing an optimal control system employing the optimization technique developed.

A numerical example compares the performance of the optimal system with a system of the conventional type which can be found in many American homes.     

The role of friction in the measurement of slipperiness, Part 1: friction mechanisms and definition of test conditions.

Friction has been widely used as a measure of slipperiness. However, controversies around friction measurements remain. The purposes of this paper are to summarize understanding about friction measurement related to slipperiness assessment of shoe and floor interface and to define test conditions based on biomechanical observations. In addition, friction mechanisms at shoe and floor interface on dry, liquid and solid contaminated, and on icy surfaces are discussed. It is concluded that static friction measurement, by the traditional use of a drag-type device, is only suitable for dry and clean surfaces, and dynamic and transition friction methods are needed to properly estimate the potential risk on contaminated surfaces. Furthermore, at least some of the conditions at the shoe/floor interface during actual slip accidents should be replicated as test conditions for friction measurements, such as sliding speed, contact pressure and normal force build-up rate.     

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?

 

Interaction of dielectric substrates in the course of tribometric assessment of the surface cleanliness

We look into theoretical and experimental aspects of tribometric interaction between two dielectric substrates with identical surfaces in the course of rapid analysis of their cleanliness. It is shown that if the coefficient of sliding friction equals that of static friction the surface is can be defined as being of production grade. The tribometric interaction of the substrates is experimentally shown not to result in a mechanical damage of the surface under study. It is suggested that the device should be complemented by a diffraction grating that generates light pulses. Based on the grating parameters, such as light pulse duration, average sum of three pulses, and degree of their deviation from reference values, the level of substrate surface cleanliness is assessed. The use of the diffraction grating of period T = 63 μm and slit width b = 20 μm is shown to pro vide a 16-fold increase in the resolution of the tribometric device. The text was submitted by the authors in English.