Mathematical basis for three dimensional circular interpolation on CNC machines

The control units of numerically controlled manufacturing machines allow the programmer only a limited number of mathematical functions with which programmes can be written. Despite these limitations it is now possible to write programmes with which three dimensional (3D) circular interpolation can be performed directly on the .machines. The necessary mathematical techniques to perform 3D circular interpolation directly on the machines are deduced, although somewhat roundabout to overcome the programming limitations. The main programming limitations as well as cutter speed limitations are indicated.Die beheereenhede van numeriesbeheerde vervaardigingsmasjiene beskik:oor 'n beperkte aantal wiskundige funksies wat tot die beskikking van die programmeerder gestel word om programme mee te skryf. Selfs met .hierdie beperkings is dit nou moontlik om programme te skryf waarmee driedimensionele (3D) sirkelinterpolasie direk op die masjiene uitgevoer kan word. Die nodige wiskundige tegnieke waarmee 3D sirkelinterpolasie gedoen kan word, al is dit 'n effens omslagtige manier om die beperkings te oorkom, word afgelei. Die belangrikste programmeringsbeperkings asook snyspoedbeperkings word aangetoon.http://sajie.journals.ac.z

Praktiese driedimensionele sirkel-interpolasie vir numeriesbeheerde masjiene

Numerically controlled manufacturing machines provide for machining circles only in two dimensions. As a result of this limitation a wide variety of shapes can only be machined by making use of computer-aided design. In this article the theory is derived and a subroutine developed with which three dimensional circular interpolation with radius correction is made available for application in practice.Numeriesbeheerde vervaardigingsmasjiene maak voorsiening vir die sny van sirkels in slegs twee dimensies. Hierdie beperking veroorsaak dat 'n wye reeks vorme slegs m.b.v. rekenaargesteunde ontwerpprogrammatuur gesny kan word. In hierdie artikel word die teorie, afgelei en ' n subroetine ontwikkel waarmee driedimensionele sirkel-interpolasie met radiuskorreksie vir praktykgebruik beskikbaar gestel word.http://sajie.journals.ac.z

The development of a computer driver jigsaw

With a jigsaw, sharp inside corners can only be sawn out if the blade of the jigsaw is lifted out of the material and the corner is approached from two different sides. For the blade to be able to re-enter the material no material must be present at the entry point. The most important feature of an automated jigsaw is that it should be able to round off inside corners on a contour and automatically return to these corners to remove material left between the round off and the contour. With this development project an automated jigsaw machine was designed, built and tested. Emphasis fell on the development of software that enables one to draw contours that need to be sawn out, change these contours into cutter paths for the jigsaw and transform the cutter paths into digital format necessary to control the jigsaw machine via the parallel port of a personal computer.‘n Figuursaag kan slegs skerp binnehoeke saag as die lem uit die materiaal uitgelig word en die hoek van twee kante af gesaag word. Waar die lem weer in die materiaal ingaan, mag geen materiaal aanwesig wees nie. Die belangrikste eienskap van ‘n ge-outomatiseerde figuursaag is dat kontoere so gesaag moet word dat binnehoeke afgerond kan word en die materiaal tussen die afronding en die gewensde kontoer outomaties verwyder moet word. Met hierdie ontwikkelingsprojek, is ‘n ge-outomatiseerde figuursaag ontwerp, gebou en getoets. Die klem van die projek val op die ontwikkeling van sagteware waarmee kontoere wat uitgesaag moet word, geteken kan word, omgeskakel kan word in ‘n snyerpad vir die saaglem en gebruik kan word vir digitale beheer van die saagmasjien deur gebruik te maak van die parallelpoort van ‘n persoonlike rekenaar.http://sajie.journals.ac.z

The development of a laser based local positioning system

There is no cheap, accurate device available with which the position of a slow moving object , such as a lawnmower cutting lawn, can be determined. If such a positioning system were available it would be possible to develop numerous programmable moving machines that can be taught computer-wise to perform daily chores. In this paper a prototype local positioning system, which could possibly be applied to determine the absolute position in relation to a fixed point for slow moving objects, is discussed. Accuracy, shortcomings and possible improvements of a laser based prototype are discussed.Daar is geen goedkoop, akkurate wyse beskikbaar om die posisie van 'n stadigbewegende voorwerp soos 'n grassnyer oor 'n grasperk te bepaal nie. Indien so 'n posisioneringstelsel wei beskikbaar sou wees, sou dit moontlik wees om 'n groot verskeidenheid programmeerbare bewegende masjiene te ontwikkel wat rekenaargewys geleer kan word om alledaagse take te verrig. In hierdie artikel word 'n prototipe 10kale posisioneringstelsel bespreek wat moontlik aangewend kan word om die absolute posisie, ten opsigte van 'n vaste punt, van stadigbewegende voorwerpe te bepaal. Akkuraatheid, tekortkomings en moontlike verbeterings van 'n lasergebaseerde prototipestelsel word bespreek.http://sajie.journals.ac.z

The development and evaluation of a prototype cell phone controlled robotic system

New cell phone technology offers the possibility to implement long distance control of robotic systems, although cell phones were not developed for control purposes but rather for communication. In this publication it is described how a cell phone is combined with a microcontroller, an audio-to-digital converter, a relay board, a wireless video camera and audio feedback to control a prototype robot. The limitations of long distance audio control of the prototype robot are discussed.AFRIKAANS: Nuwe selfoontegnologie bied die moontlikheid van langafstandsbeheer van robotstelsels, hoewel selfone nie ontwerp is vir beheerdoeleides nie, maar vir kommunikasie. In hierdie publikasie word beskryf hoe ‘n selfoon gekombineer word met ‘n mikrobeheerder, ‘n oudio-na-digitale-omskakelaar, ‘n relê-bord, ‘n koordlose videokamera tesame met oudioterugvoer om die beheer van ‘n prototipe robot te behartig. Die beperkinge van langafstand-oudiobeheer van die prototipe robot word bespreek

Silindriese interpolasie

In the manufacturing process of cylindrical cams with numerically controlled milling machines, the programming as well as the machining of accurate profiles normally turn out to be problematic. In an effort to overcome some of these problems the machine tool builder, MAHO (Germany), had during 1990, supplemented its numerically controlled units with an option with which cylindrical interpolation is made possible. With this option programming is considerably simplified in some cases, but serious limitations necessitate in many instances that the option cannot be applied at all. The limitations of the option and how to overcome them, are illustrated and discussed in a typical programming example

Ontwikkeling van 'n parametriese model vir die sny van ruimtes soos die van margarienbakkies

When three dimensional machining is performed with a numerically controlled milling machine, then it is necessary to make use of cutter centre point programming because radius correction for these machines is possible in two dimensional context only. With the rapid development of numerically controlled units it is possible now to use parameter programming for the development of three dimensional spaces which was possible only with computer aided design software some two years ago. An exceptional visualization of the relationship between cutting surface and cutter position as well as a sound mathematical background is necessary to enable accurate programming of three dimensional spaces

Development and testing of a wireless controlled car using the internet as communication medium

Recent innovations in wireless networking technology have brought low cost, high bandwidth and low latency communication to the consumer. Apart from the standard use of connecting computers to the Internet, the new wireless networks also offer the possibility of sending a combination of two-way video, audio and control signals almost instantaneous between any two places in the world. This paper provides an overview of the techniques and software integration necessary to develop a mechatronic device that can be controlled remotely through remote controlled vehicle, was developed and successfully tested to demonstrate the integration of motion control with live video feedback through the Internet.AFRIKAANS: Die onlangse vooruitgang in draadlose netwerktegnologie het laekoste, hoëbandwydte en lae tydsvertragingkommunikasie binne bereik van die gebruiker geplaas. Behalwe die standaardgebruik om rekenaars aan die Internet te verbind, bied die nuwe draadlose netwerke ook die vermoë om tweerigting-video, oudio- en beheerseine feitlik oombliklik tussen enige twee plekke op aarde te stuur. Hierdie artikel veskaf 'n oorsig oor die tegnieke en rekenaarprogramintegrasie wat nodig is om 'n megatronikatoestel te ontwikkel wat deur afstandsbeheer oor die beskikbare draadlose netwerke beheer kan word. 'n Prototipe megatronikatoestel, in die vorm van 'n afstandbeheerde voertuig, is ontwikkel en suksesvol getoets om die integrasie van bewegingsbeheer en intydse videoterugvoer deur die Internet te demonstreer

Long-Term Outcomes of Patients With Recent-Onset Rheumatoid Arthritis After 10 Years of Tight Controlled Treatment: A Randomized Trial

BACKGROUND: Treat-to-target therapy is effective for patients with rheumatoid arthritis (RA), but long-term results of continued targeted treatment are lacking. OBJECTIVE: To evaluate long-term outcomes in patients with early RA after 10 years of targeted treatment in 4 treatment strategies. DESIGN: Randomized trial. (Nederlands Trial Register: NTR262 and NTR265). SETTING: The Netherlands. PATIENTS: 508 patients with early active RA. INTERVENTION: Sequential monotherapy (strategy 1), step-up combination therapy (strategy 2), or initial combination therapy with prednisone (strategy 3) or with infliximab (strategy 4), all followed by targeted treatment aiming at low disease activity. MEASUREMENTS: Functional ability (Health Assessment Questionnaire [HAQ] score) and radiographic progression (Sharp-van der Heijde score) were primary end points. Survival in the study population was compared with the general population using the standardized mortality ratio. RESULTS: 195 of 508 of patients (38%) dropped out of the study (28% in strategy 4 vs. 40% to 45% in strategies 1 to 3, respectively). At year 10, mean HAQ score (SD) was 0.57 (0.56); 53% and 14% of patients were in remission and drug-free remission, respectively, without differences among the strategies. Over 10 years, mean HAQ scores were 0.69, 0.72, 0.64, and 0.58 in strategies 1 to 4, respectively (differences not clinically relevant). Radiographic damage was limited for all strategies, with mean Sharp-van der Heijde estimates during follow-up of 11, 8, 8, and 6 in strategies 1 to 4, respectively (P = 0.15). Standardized mortality ratio was 1.16 (95% CI, 0.92 to 1.46) based on 72 observed and 62 expected deaths, with similar survival among the 4 strategies (P = 0.81). LIMITATION: Dropout rate varied by strategy. CONCLUSION: In patients with early RA, initial (temporary) combination therapy results in faster clinical improvement and targeted treatment determines long-term outcomes. Drug-free remission, with prevention of functional deterioration and clinically relevant radiographic damage, and normalized survival are realistic outcomes. PRIMARY FUNDING SOURCE: Dutch College of Health Insurance Companies, Schering-Plough, and Janssen