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CANtrace 3.17 Released

We have reached the Next Level – Cantrace 3.17 Released.

This release adds playback of log files to the CAN bus, which can be used for simulation, testing and bus traffic generation. Any log file in ASC format can be used to generate data on the CAN bus. For those working with J1939 this release adds masking of priority bits in J1939 databases. This allows using the default priority in the database, while still matching messages on the bus that uses a different priority. This feature works well with the included J1939 database, which in this release has been enhanced with the DM1 and Address Claimed messages, which are common in J1939 networks. Read more

Analysis of residual errors and their consequences in CANopen systems

Residual error analyses for CAN networks have been performed for years. It is well documented, that commonly used equations do not fully apply for analytic computing of the residual error probability of CAN networks. Also too high bit error probability values have commonly been used in the analyses. Furthermore, CANopen networks have been analyzed as CAN networks, without taking into account the additional safeguards provided by various CANopen services. Results have been very pessimistic, which has lead to significant unnecessary cost and complexity in various applications.

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Physical layer really matters in CAN

One should remember with the CAN physical layer that there exists only impedance, not plain conductors. Let us start with a brief review of the main important transmission line characteristics.

Despite of the comprehensive knowledge of the CAN physical layer, there is poor tradition in design of physical layer structures for industrial and machinery CAN net-“works. Cables with “wrong” impedance (not matching with termination) are commonly used and many engineers intentionally select them, because of constrained understanding of the transmission line behavior. Most engineers forget, that the transmission line cannot be considered as conductor with DC characteristics only. “Wrong” impedance leads not only to unmanaged reflections but also to different wave propagation speed in the cable. Unmanaged reflections increase the bit-error probability of the network and the propagation speed difference makes bit timing analysis results invalid. Read more

CANopen safeguards

Data transfer over CANopen networks is extremely reliable, but CANopen also offers further safeguards in order to decrease the effect of residual errors further.

In many applications, complex safety add-ons have been designed on top of existing control systems, which has lead to significantly increased complexity and costs. The most significant increase of the performance level can be achieved by replacing all analog signal paths with digital communication: as long as an error can be detected and a control system can perform a reliable reaction, the error cannot cause any harm. When typical failures of systems are analyzed, it is obvious that analog signal paths are the weakest point of any control system. Read more

Systematic re-use of information

Eliel Saarinen, a Finnish architect, said: “Always design a thing by considering it in its next larger context – a chair in a room, a room in a house, a house in an environment, an environment in a city plan.” That also applies to system design. Read more

Model-based design of CANopen systems

Multiple disciplines for mechatronic system design co-exist, which hinder the utilization of software-oriented modeling principles e.g. UML. Existing modern tools may be integrated into a working tool chain.
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CANopen in the frontline of openness

Open knowledge is any content, information or data that people are free to use, re-use and redistribute – without any legal, social or technological restriction.

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Experimental CANopen EEC management

Current CANopen design files do not support EECs (emergency error codes) with their human readable descriptions. This feature has become more problematic because of abstraction to parameters and signals. The system structure has become automated and proven way of working. Manual EEC management is decreasing the development efficiency because it is time-consuming and prone to inconsistent codes. These design projects are iterative and effort is wasted on each cycle of each project by managing EECs manually. Descriptions shall be uniformly defined for both producers and consumers. Read more

SI-Unit and scaling management in CANopen

Various kind of inconsistencies have been typical problems in design of distributed control systems. The first solved issue was an automated generation of signal and parameter abstraction from CANopen project avoiding the inconsistent names between application software and communication. The use of meta information of signals and local parameters, such as name, minimum, maximum and default values has already been implemented to avoid the most common inconsistencies. Read more

Commonality between hydraulic valves driven by generalpurpose CANopen I/O and hydraulic CANopen drives

Hydraulic valves have been driven by separate valve control electronics for decades. The tradition is becoming obsolete due to ever increasing performance, controllability, maintainability and re-usability requirements of the target systems. However, there are still a lot of functionally constrained fully hydraulic systems which need to be upgraded first to electrically controlled. There are also huge number of simple proprietary control systems needing upgrade from proprietary to standard technologies and components. Especially for such kind of systems, it is important to achieve easy and straightforward upgrade path from use of proprietary valve amplifiers into coil-mounted drivers with current-controlled valve. Further step is replacing separate valves and drivers with intelligent hydraulic drives. It is also important to utilize commonality between lower- and higher performance drive solutions. This presentation shows hands-on case examples how the presented system integration challenges can be solved with standard CANopen devices according to device profiles for general-purpose I/O-devices (CiA-401) and hydraulic drives (CiA-408). The main conclusion is that commitment to CANopen actually enables not only the required approaches, but also manufacturer and device independence with large number of interchangeable devices. Another significant result is that the lowest level applications can be implemented just by integrating standardized devices, without application software project. Read more

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