Remote control of CAN-based
industrial equipment using
Internet technologies
Prof. Dr.-Ing. Gerhard Gruhler, University of Applied
Sciences Reutlingen,
Steinbeis Technology Transfer Center Automation (STA),
Germany
Remote control - CAN bus
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For demonstration purposes the
described systems are online 7
days / 24 hours and
can be accessed by everyone
from all over the world.
Remote control - CAN bus
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CAN is not only used to great extent in cars
and other mobile applications but also in
industrial equipment, machine control,
building control, medical and other devices
in
the service/public area. Due to the global
market place, in most these fields remote
system access becomes more and more
important.
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ISO 11898 defines the Physical
Layer.
• The CAN bus [CANbus] is a Balanced
(differential) 2-wire interface running over
either a Shielded Twisted Pair (STP), Unshielded Twisted Pair (UTP), or Ribbon
cable. Each node uses a Male 9-pin D
connector. The Bit Encoding used is: Non
Return to Zero (NRZ) encoding (with bitstuffing) for data communication on a
differential two wire bus
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A number of different data rates are defined, with 1Mbps
(Bits per second) being the top end, and 10kbps the
minimum rate. All modules must support 20kbps. Cable
length depends on the data rate used. Normally all the
devices in a system transfer uniform and fixed bit-rates.
The maximum line length is 1Km, 40 meters at 1Mbps.
Termination resistors are used at each end of the cable.
The worst-case transmission time of an 8-byte frame with
an 11-bit identifier is 134 bit times (that's 134 microseconds
at the maximum baud rate of 1Mbits/sec).
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Advantages:
These are e.g.:
- more reliable communication channels,
- use of PC-based standard technologies
and software like TCP/IP-stack, web
servers, browsers, Java, XML etc.
- significant cost reduction for
development, equipment and operation
- less effort in particular on the client´s
side: usually the client just needs a
standard web browser,
- worldwide availability of internet access
at low costs
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The range of possible remote access
applications and the related benefit is large:
- remote production and machine data
collection,
- remote system monitoring,
- remote error detection,
- remote observation purposes, also for
security reasons,
- customer support for programming and
running the system, help for bug fixing,
- remote device parameterisation,
- software/firmware updates via internet,
- better support for maintenance staff,
- sometimes even avoiding service trips,
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direct system control by remote
operator interface,
- and last but not least better marketing
support: some device manufacturers not
only provide the usual bunch of
documentation on their web-site but start
to make accessible real devices for
demonstration purposes to their
perspective customers.
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High-level web interfaces
High-level remote access to a KUKA robot via internet and CAN
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High-level web interfaces
High-level remote programming and control concept for a FESTO handling robot
using CAN
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Remote access to and monitoring of
lower CAN layers
CAN Message Manager's web interface
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Remote access to and monitoring of
lower CAN layers
Concept of extending CAN systems over the internet using CAN-TCP/IP-CAN
gateways
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Remote access to and monitoring of
lower CAN layers
Software structure of CAN-TCP/IPCAN gateways
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PC-based and embedded systems
for web
server and client
Examples of embedded web servers, partially available with CAN interface
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PC-based and embedded systems
for web
server and client
Remote access concept, not capable of passing firewalls.
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PC-based and embedded systems
for web
server and client
Modified access method, to overcome firewalls
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