IFD: Intensive Fieldbus Diagnostic

A few words up front: The CAN bus is the star­ting point for nume­rous suc­ces­sor sys­tems which have emer­ged from this ground-brea­king tech­no­lo­gy over the years. CAN-based bus sys­tems such as CANopen and J1939 ETC are dialects of a com­mon lan­guage. They have beco­me brand names in their respec­ti­ve sphe­res, but their true ori­gins are fre­quent­ly for­got­ten. Even so, CAN is the com­mon phy­si­cal foun­da­ti­on for all the­se bus systems.

Examp­les of CAN-based applications:

  • You will no doubt know about the OBD inter­face in your car. That is whe­re ser­vice work­shops and government inspec­tion agen­ci­es can hook up to read out errors and other data. OBD is a CAN gate­way to the con­trol devices on the vehicle.
  • In a vehi­cle used by muni­ci­pal sani­ta­ti­on depart­ments, SAE J1939 con­trols the engi­ne, while a CANopen bus is used to mana­ge the various onboard func­tio­n­a­li­ties. Both are CAN-based protocols.
  • Ener­gy­Bus con­trols the motor assi­s­tance on your electric bicy­cle, lea­ving you free to enjoy the fresh air. Ener­gy­Bus is based on CANopen.
  • All modern trac­tors and their attach­ments incor­po­ra­te an ISOBUS, a fur­ther deve­lo­p­ment of SAE J1939, which is based on the CAN stan­dard 2.0B. The same app­lies to many other machi­nes such as exca­va­tors, cra­nes, etc.
  • Dro­nes are kept in the air by UAVCAN, a rela­tively new stan­dard for unman­ned fly­ing objects.
  • Even your den­tist reli­es on CAN-based con­trol, name­ly for the electri­cal­ly adjus­ta­ble pati­ent chair and the incor­po­ra­ted functions.

Accord­in­gly, when we speak about CAN, that also inclu­des app­li­ca­ti­ons in the various dialects and under the various mar­ke­ting names. You can thus replace the term CAN with whiche­ver name is appro­pria­te for your par­ti­cu­lar case.

Regardless of the situation in which you use IFD, thanks to the gain of information, you will always …

  • Make data-based decisions;
  • Design and pro­du­ce machi­nes which ope­ra­te with hig­her stability;
  • Acce­le­ra­te the error loca­liz­a­ti­on and repair;
  • Mini­mi­ze the downtimes;
  • Save cos­ts.

The com­mu­ni­ca­ti­on back­bone is too important to your machi­ne for you to risk neglec­ting it possibly.

Noise margin

Digi­tal bus­ses are gene­ral­ly view­ed as sta­ble sys­tems with high avai­la­bi­li­ty. That also app­lies to a CAN bus. With only mini­mal elec­tro­nics out­lay, it pro­mi­ses a high level of inherent relia­bi­li­ty thanks to intel­li­gent error detec­tion mecha­nisms. For small and very simp­le topo­lo­gies, this achie­ves ade­qua­te sta­bi­li­ty and only extra­or­di­na­ry cir­cum­s­tan­ces – such as mecha­ni­cal dama­ge to a cable – lead to a loss of com­mu­ni­ca­ti­on. Such pro­blems, fur­ther­mo­re, are usual­ly rela­tively easy to localize.

The noi­se mar­gin of a digi­tal bus is an important para­me­ter, but its value remains lar­ge­ly unknown for most sys­tems. The impor­t­ance of the noi­se mar­gin for reli­able machi­ne ope­ra­ti­on incre­a­ses in line with the com­ple­xi­ty, while at the same time, the influ­en­cing fac­tors also incre­a­se. This can easi­ly lead to a situa­ti­on in which the added com­ple­xi­ty redu­ces the noi­se mar­gin to a point whe­re reli­able ope­ra­ti­on is no lon­ger gua­ran­te­ed. If this hap­pens, appa­rent tri­via­li­ties may suf­fice to bring the com­mu­ni­ca­ti­on down.

Incre­a­singly com­plex and auto­no­mous machi­nes demand more and more con­trol modu­les, sen­sors and actua­tors, all of which must com­mu­ni­ca­te via the CAN bus. The grea­ter com­ple­xi­ty alo­ne defi­nes moni­to­ring of the actu­al phy­si­cal bus cha­rac­te­ris­tics as a key fac­tor, first during the deve­lo­p­ment of the sys­tem and then con­ti­nuous­ly after deployment.

Aging

Aging is an often neglec­ted fac­tor in con­nec­tion with bus sys­tems. The lower the initi­al noi­se mar­gin, the more likely that age­ing alo­ne will even­tual­ly result in down­ti­mes. Long-term expe­ri­ence tells us that cable car­ri­ers and slip con­ta­cts will only have a limi­ted ser­vice life. But aging is also an issue for cables, plug con­nec­tors and the elec­tro­nic com­pon­ents in sen­sors and actua­tors. Depen­ding on the stres­ses ari­sing from electric pul­ses or envi­ron­men­tal influ­en­ces, digi­tal signals will auto­ma­ti­cal­ly dete­rio­ra­te until com­mu­ni­ca­ti­on final­ly breaks down altog­e­ther. Moni­to­ring at regu­lar inter­vals wit­hin the frame­work of ongo­ing main­ten­an­ce is able to iden­ti­fy such aging.

In some cases, con­stant moni­to­ring of the phy­si­cal signals may be mea­ning­ful. This per­mits auto­ma­ted messages to be sent to a con­trol cen­ter if the signal qua­li­ty drops below a defi­ned level or if the trans­mis­si­on of indi­vi­du­al mes­sa­ge frames must be repeated. Sub­se­quent main­ten­an­ce can then inclu­de tar­ge­ted trou­ble­shoo­ting and repairs to mini­mi­ze the risk of unsche­du­led com­mu­ni­ca­ti­on downtimes.

The CAN bus as element of a maintenance strategy

Many machi­ne para­me­ters are moni­to­red con­ti­nuous­ly, and nume­rous sen­sors are con­stant­ly collec­ting, orga­ni­zing and eva­lua­ting data. On the other hand, the CAN bus – as the back­bone of com­mu­ni­ca­ti­on – is rare­ly inclu­ded in the main­ten­an­ce stra­te­gy. This could mean that no one is pro­per­ly pre­pa­red for bus down­ti­me. The­re may be a lack of trai­ned tech­ni­ci­ans, mea­su­ring devices and com­pa­ra­ble mea­su­re­ment values, and effi­ci­ent­ly acces­si­ble sys­tem docu­men­ta­ti­on. In this case, com­pon­ents are fre­quent­ly repla­ced at ran­dom, hoping that such radi­cal mea­su­res will eli­mi­na­te the problem.

Even so, it is not sufficient simply to purchase a measuring device.

Let’s assu­me that you have a mea­su­ring device and come to a sys­tem that is down. Without the pos­si­bi­li­ty to com­pa­re mea­su­re­ments with refe­rence values, it is dif­fi­cult to inter­pret your rea­dings cor­rect­ly. It is thus very important to pos­sess indi­vi­du­al sys­tem mea­su­re­ments from the begin­ning of the machi­ne lifecy­cle as a basis for com­pa­ri­son with your cur­rent mea­su­red values.

The CAN bus must become part of your overall maintenance strategy.

This redu­ces the neces­si­ty to make presump­ti­ons about the sta­tus of the CAN bus. Ope­ra­tio­nal relia­bi­li­ty incre­a­ses signi­fi­cant­ly, and you can also res­to­re pro­per ope­ra­ti­on more quick­ly in case of errors.

1. During design and development

When deve­lo­ping CAN-based machi­nes, it is expe­dient to deter­mi­ne the phy­si­cal bus cha­rac­te­ris­tics at regu­lar inter­vals. In this way, it beco­mes pos­si­ble to incre­a­se the noi­se mar­gin and ope­ra­tio­nal relia­bi­li­ty, for examp­le, through modi­fi­ca­ti­on of the topo­lo­gy or a per­ti­nent choice of baud rate. Com­pa­ra­ti­ve mea­su­re­ments reve­al whe­ther plan­ned savings lead to a signi­fi­cant or only mar­gi­nal reduc­tion of the signal qua­li­ty. During the later pha­ses of design and deve­lo­p­ment, the influ­ence of the over­all sys­tem on bus per­for­mance and the sus­cep­ti­bi­li­ty to exter­nal influ­en­ces can also be investigated.

2. In manufacturing and quality testing

The last step at the end of machi­ne manu­fac­tu­ring is qua­li­ty tes­ting. If this tes­ting inclu­des mea­su­ring the bus qua­li­ty, it is pos­si­ble to detect any fluc­tua­tions and docu­ment the initi­al mea­su­re­ment values.

3. For service on site

Ser­vice tech­ni­ci­ans can refer to the expe­ri­ence and mea­su­re­ments collec­ted during deve­lo­p­ment and qua­li­ty tes­ting. This offers a basis for com­pa­ri­son, and it is pos­si­ble to deter­mi­ne whe­ther or not a cur­rent down­ti­me is attri­bu­ta­ble to the bus.

Evaluation

Across-the-board assess­ments of mea­su­re­ment values are rare­ly mea­ning­ful. It is not pos­si­ble to say whe­ther a mea­su­red qua­li­ty value of 75% is auto­ma­ti­cal­ly good or bad in a par­ti­cu­lar case. Too many fac­tors influ­ence the actu­al mea­su­red values. Accord­in­gly, mea­ning­ful limit values must be deter­mi­ned on the basis of data collec­ted in advan­ce. In the case of ser­vice, device per­for­mance can be eva­lua­ted in terms of the pre­vious­ly recor­ded limits and indi­ca­ted in accordance with the traf­fic-light principle.

The measuring device

The most sui­ta­ble tool must be cho­sen accord­ing to the cri­te­ria of your par­ti­cu­lar use. GEMAC offers four dif­fe­rent mea­su­ring devices, tog­e­ther with soft­ware sui­ta­ble for the most diver­se fiel­ds of application.

The­re is no doub­ting the fact that CAN­touch is the sys­tem with the broa­dest diver­si­ty of mea­su­re­ments, the most intui­ti­ve ope­ra­ting con­cept and the simp­lest eva­lua­ti­on func­tions. As a bat­te­ry-powe­red unit, it can be deploy­ed quick­ly and sim­ply. The func­tio­n­a­li­ty of the device was deve­lo­ped on the basis of high-level feed­back from cus­to­mers. With CAN­touch, fun­da­men­tal eva­lua­ti­on of the bus, with a “good/bad” state­ment on the over­all sta­tus, takes only approx. 10 seconds and can be star­ted with a sin­gle touch gesture.

The pos­si­bi­li­ty to inte­gra­te a CAN bus libra­ry for your ent­i­re machine­ry base, with indi­vi­du­al eva­lua­tions and pre­de­fi­ned bus user lists, pla­ces a power­ful tool in the hands of your technicians.

How good is the signal quality on your machine?

Find out for yourself, and take the oppor­tu­ni­ty to put our CAN­touch device to the test. We would be glad to pro­vi­de a CAN­touch device on loan – free of char­ge – for 5 days to enab­le you to mea­su­re and test your indi­vi­du­al machine.

Optio­nal­ly, you can have an eva­lua­ti­on done by our support.