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.
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 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.
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.