CAN Newsletter June 2008
| Business | CANopen SIG sub-sea - CiA MG Spain - Test ECUs |
|---|---|
| Application | Looking into the space–the Grantecan CANopen in high-energy physics CANopen networks in container handling Dedicated for vehicle safety applications |
| Device | Display communicates with encoder Multi-interface - Automotive - Test conference CNC platform OEM boards with CAN Encoder - HMI computer Frequency inverter I/O modules Servo controller supports interpolated mode Pressure meters - Control system Joysticks - Hand-held device - Valve system Fluid power - Hydraulic control - Pressure sensors Motor controllers - PCI-Express - PC/104 board Single-board computer - Bus converter Semiconductor |
| Tools | Automatic testing of CANopen devices Cable tester - Prototyping - Data-logger - Generator Infotainment HIL simulator - Gateway & testing tool Motor control kit - Configuration tool Linux - Simulator - Diagnostics - Device managing Wireless analysis in a multi-protocol CAN environment |
| Software | PLCopen - CANopen XDD - Configuration suite |
| Specification | Node-ID assignment with LSS Fastscan |
| Automotive | Euro-5 - Cadillac BLS wagon |
| Reader service | CAN Newsletter subscription form |
Editorial: Save your investments
CANopen profiles are used also on non CAN-based communication systems; this includes EtherCat, Ethernet-Powerlink, and Varan networks. Recently, CAN in Automation (CiA) and Safety Network International e.V. (SNI) agreed that manufacturers of SafetyNet p devices may implement CANopen profiles. From the users point of view this is a huge advantage: It saves software investments when migrating to higher-performance network technologies.
In the last years, several manufacturers have already used CANopen profiles on non CAN-based networks. There are already some devices on the market, which implements standardized CANopen profiles on EtherCat, Ethernet-Powerlink, or Varan. The use of the CANopen dictionary structure and the CANopen profiles is generally permitted to any party, if they fulfill the following conditions:
The structure of the CANopen dictionary is not changed and used as specified in CiA 301.
- The index range 6000h to 9FFFh is reserved for standardized CANopen profiles by CiA.
- The index range 1000h to 1FFFh is free for non CAN-based communication technology consortia with three exceptions: The objects 1000h, 1001h, and 1018h are specified by CiA. The unique vendor-ID contained in 1018h is assigned by CiA only.
- The index range A000h to AFFFh shall be used for network variables.
- The index range B000h to BFFFh shall be for system variable as specified in CiA 302-7 (respectively in CiA 400).
- The index range C000h to FFFFh is reserved for CiA use.
These conditions are the same for all interested parties – CiA member companies and non-members. Everyone has the same rights and the same duties to use standardized CAN profiles.
All CANopen users benefit from standardized profiles. In order to enable also non CiA members to participate in the development of standardized profiles, CiA has established together with other non-profit organizations Joint Task Forces and Joint Special Interest Groups. Successful examples include the CANopen profile for extruder down-stream devices jointly developed with the Euromap organization, and the CANopen SIIS (subsea instrumentation interface specification) level-2 devices.
Jetter and mobile applications
The Jetter AG known as the first industrial Ethernet supplier has extended its business to CAN-based solutions in mobile applications. Besides CAN-based control systems for truck-mounted applications (e.g. for fire-fighting equipment), the company offers tools for the ISOBUS as standardized in ISO 11783 series. The launched mask-editor is dedicated for designing virtual terminals compliant to the ISO specification, which describes the CAN communication between the implements (e.g. harvesting machines) and the tractor’s generic user interface. In order to design ISO conform masks, the provided JetViewSoft ISO designer tool simplifies the task of the implement manufacturer. The generator virtual terminal software runs on different target systems: Internet browser with HTML masks, Windows CE or other operating systems. The structure of the masks and the elements are object-oriented. Single elements are implemented only once, and will than be referenced (pointer) on different pages. All changes of the element will cause changes on all referenced pages. The generated ISO compliant file is downloadable via the CAN network. The ISOBUS uses J1939-based transport-layer protocols. Typical objects such as pointers, arc, meter, and soft-keys are pre-defined. They can easily be integrated in the virtual terminal library.
In order to strengthen its activity in mobile electronics for off-road and off-highway vehicles, Jetter acquired the Controls Developments (U.K.) developing electro-hydraulic control systems. The British company located in Oxford will be integrated into the Jetter AG; it will be the design center for Jetter’s mobile automation activities. The Jetter AG in Ludwigsburg (Germany) will manage production and administration.
www.jetter.de
Frequency inverter with CANopen-based system bus
In drive engineering, variable-speed drives with three-phase AC motors controlled by frequency inverters are increasingly being used. The coupling of the inverters necessary for the realization of the machine functions is implemented by a parallel connection, which demands a large amount of wiring and is connected with the risk of installation errors due to the large number of cores. To ease the installation and reduce the wiring errors, a simple serial installation with merely two cores on the basis of the system bus can be used with Bonfiglioli’s Active Cube inverters. Not only the reduction of the installation efforts, but also further benefits in application result.
CANopen-based system bus
The system bus of the inverters is a CAN-based communication network. It enables quick exchange of data between the inverters as well as access to parameter data of all the inverters on the system bus from a system bus master.
The functionality of the system bus is closely based on the CANopen standard. The system bus has three PDO channels (Process Data Objects) for each inverter for quick exchange of process data. In addition, two SDO channels (Service Data Objects) exist for parameterization.
Arbitrary data of the inverters can be transmitted via the three PDO channels, each with one transmission and one reception channel. This enables, for example, master/slave configurations and cascading with little effort, high precision and at high speed.
Each transmission channel and reception channel comprises 8 bytes, which can be occupied at will with objects. This results in a flexibility for the various applications. The selection of the transmission objects and assignment of the reception objects is done simply with the VPlus visualization software. No additional configuration tool is necessary.
SDO channel 1 is used for access to the parameters of the inverters on the system bus. This is done with the help of a field bus actuation in the master inverter. A controller can address all the inverters via one field bus actuation.
SDO channel 1 is reserved for a PC-based visualization tool, enabling access to the parameterization of all the inverters parallel to the operation of a control. The number of participants on the system bus is up to 64 inverters. The system bus can be operated with transmission rates of up to 1 Mbit/s and enables an effective useful data rate of 320 kbit/s. In this way, the coupling of functions in the inverters with real time behavior is possible.
Thanks to the use of the CAN technology with the construction elements available there, a component for the realization of the system bus is available. The VPlus visualization software is used for commissioning, enabling the configuration of the system bus in the same way as the parameterization of the functions in an inverter. The user is in an environment, which is familiar to them. Thanks to organized structures, the necessary parameters for the settings of the system bus are easy to see.
Only a few parameters need setting to produce a functional system. With the possibility of transmitting the data existing in one inverter to further inverters, completely new approaches to the realization of applications result.
For example, analog variables of an inverter can be transmitted to further appliances with all the devices receiving precisely the same data. The faults occurring in parallel connection of analogue inputs due to scanning errors and drift are eliminated. Actual figures of an inverter can be transmitted to other inverters as nominal figures. This enables realization of, for example, gear functions and cascading.
If a serial network actuation is used in an inverter configured as a system bus master, all the inverters on the system bus can be addressed by it. In this way, a distinct reduction in costs is achieved by field bus components becoming superfluous.
The entire parameterization of all the inverters is done from the machine controls via the field bus actuation in the master inverter and the system bus. These benefits result here:
- Use of only one RS-485 field bus actuation instead of six.
- Avoidance of wiring for the reference frequency couplings of the electronic gear.
- All the drives can be reached centrally for the controls via the main drive.
An application example is in mechanical engineering. The entire configuration comprises six inverters, which fulfill various functions in the machine. A main drive works with two subsidiary drives in the form of an electronic gear. The nominal speed of the slave inverter is derived from the speed list figure of the master inverter and transmitted to the slave inverter via the system bus (PDO channel). In addition, there are three further subsidiary drives in the drive system. They are actuated by the machine controls via the master inverter and the system bus (SDO channel).
