CANbus guide V2 - Sensorland

1 Sensor-Technik UKThe CANbus Technology, Pressure and Force Measurement SpecialistThe Engineer s guide to CANbus21st Century vehicles where modularsensors and controls are connected to anetwork backbone are now possiblethanks to the widely used CANbus . Youcan throw away the wiring loom andreplace it with two wires! Smart gaugesand sensors can be directly connected tothe CANbus . Control modules canread/send data, display systems canread/log data and because it is anetwork, it is irrelevant wherecomponents are physically located. Information display panels show thedriver/operator what he needs to of information feeds the servicesystem and panels display informationwhere required, for example next to thevalves on a tanker. CANbus also has thebandwidth to cope with real-time controlas well as data BenefitSoftware set-up Flexible, lower production costStandard protocol Able to connect to different equipmentCommunication Communicate with other equipmentFault diagnostic Error detection for faulty componentsData logging No more false warranty claimsMonitoring Misuse protectionMemory Repeat working functionsInformation Operator can make decisionsImproved logisticsElectronic controls Better operator working conditionsLonger working hoursHydraulic remote No vibration, no hazardsBetter viewingSingle system Combined controlsInformation servicing, Close down facility and error protectionStandard units International regulations and laws approvedFewer mechanical parts High reliability.

2 Minimum failure ratesStandard hardware Exclusive to Sensor-TechnikLower cost Reduced wiring, weightLow servicing costs, fast repairData sheets,brochures and evenwebsites can t explainthe full advantages ofmoving to CANbusWhy CANbus ?Sensor-Technik UK Ltd Tel: 01234 782049 Fax: 01234 782056 Lower cost production, one set ofsoftware, one system and one supplieron a standard communication systemgiving you flexibility: The same assemblycan be set-up via the software toindividual customer applications withouthaving to change any hardware. Communication systems: DifferentCANbus controllers are able tocommunicate with each other over thesame bus, engine to transmission, to the operator panel or to any othercontroller. Easily controlled and consistentlyprecise work: CAN Controllers can belinked together. For example, a controlleron one vehicle can talk to another youcan add machinery on a tractor and it willwork together. Repeat working functionscan be logged by simple selection,giving high repeatable quality of work.

3 Better operator working conditions andlonger working hours: Push switches andjoysticks replace heavy or difficult levers,giving better driver comfort and betterviewing as valve blocks, pipes etc areeliminated from the cab. No vibration,mechanical shocks, fatigue, white fingeretc., and the operator interface can beset up to individual applications. Reduced mechanical components,minimum failures: As the operator panelelectronically talks to the controller, theremoval of the hydraulics in the drivercab can be achieved desirable as newEuropean regulations come into controller can be mounted close tothe hydraulic system, allowing pipeworkto be reduced. Eliminating being in the wrong place ;remote viewing: CANbus can be linkedwith other equipment such as remotecontrols, video cameras and GPS(Global Positioning System) to track avehicle and to ensure it only works whereit has been allocated. Information the key to improvementand saving money: CANbus can bringtogether several systems, such asweighing systems, information logging,statistics, servicing reports, time per joband others.

4 Fast and low cost servicing andbackup: No more wasted investigationinto why a vehicle has a problem; thefault diagnostic with complete errormessage will highlight the problem andit s also available by mobile telephone. Low cost servicing, fewer warrantyclaims: Safety features/error detectioncan be added to ensure equipmentcannot be overloaded or misused andonly correct commands are executed. Inthe event of misuse the process will bestopped and logged. High reliability where it counts, use ofstandard sensors at low cost, no needfor special sensors or new technology:The input/output modules allow you touse your already proven sensors whichare tried and tested although you canof course combine them with up-to-dateCANbus sensors too!Making the move tobus-based control isa big step, but itneedn t be a difficultone. Whether youneed fully approvedcomponents with aproven track recordor complete systemdesigns, we canmeet yourrequirements. Andwe ll be with youevery step of the wayThe benefits of CANbusTel: 01234 782049 Fax: 01234 782056 Sensor-Technik UK Ltd CANbus control units and HMIs (HumanMachine Interfaces) are used in a widevariety of functions in mobile andstationary applications.

5 Via the variousconfigurable inputs and outputs it ispossible to connect all types of sensorsand actuators directly to the controlunit; the user-programmed controllermonitors the system inputs and allowseither closed loop or open loop controlof the outputs. This way, componentssuch as proportional valves can becontrolled directly. Together with extended diagnosticsfunctions and the CAN interface, thesystem offers unmatched in-servicefacilities. In case of failure (such asbroken cables or short circuits) it allowsusers to restore the vehicle to safeconditions and provides service staffwith the right tools for quick and easydiagnostics. With the additionalpossibility of remote (wireless)maintained diagnostics, CANbus iscapable of making a significantcontribution to increased vehicleavailability and productivity. More and more vehicle manufacturersand automotive component suppliersare realising the benefits of the CANbussystem. This technology has nowreached a stage where internationallyagreed standards exist, so that differentmanufacturers electronics cancommunicate together.

6 A typicalmodern truck might have separateelectronic modules controlling engine,automatic gearbox, ABS brakes and on-board hydraulic control. The enginemodule has a sensor reading RPM. Allthe other modules, such as thegearbox, need to know the engine RPMto operate correctly. The engine modulewill broadcast the engine RPM messageon the CANbus , and a moduleconnected to the bus can receive themessage and use that information. Thismeans that the engine RPM sensorneed only be connected to one of themodules. The versatility of CANbus modules isevident from the wide range ofapplications in which they are used:specialised civil engineering; mobilecranes; agricultural/harvestingmachinery; forklift trucks; refusecollection vehicles; steamrollers; aircrafttowing vehicles; road sweepers;excavators; fire engines; militaryequipment; boats; shipyard cranes;diggers; and many othersWhat can CANbus do?Applications include: Engine management Electro-hydraulicsteering systems(steering-by-wire) Hydrostatic drivecontrol (driving-by-wire) All control functionsof working hydraulics Transmission control Automatic levellingand positioning ofplatformsSensor-Technik UK Ltd Tel: 01234 782049 Fax: 01234 782056 Controller Area Network (CAN) wasoriginally developed by Bosch for use inthe automotive industry, but hasestablished itself as the standard bussystem for mobile applications, and isdefined under ISO 11898.

7 CANbussystems exhibit high transfer rates up to1 Mbit/sec and high data transmissionreliability. A number of differentcapabilities (CRC, frame checking,acknowledgement, bit monitoring and bitstuffing) enable the CAN protocol torecognise errors in the transmitted data(caused for example by electromagneticdisturbances) and to correct them. Thiscorrection takes place with very little lossof time, making CANbus extremelyreliable in demanding pair of wires forms the transmissionmedium. The length of the network canbe up to 40m for the maximum 1 Mbit/sectransmission speed, but networks can beup to 1000m in length without the needfor repeaters and are practical fortransmission rates of 80 Kbit/sec or number of nodes on the network isunlimited in theory, but in practicedepends on the type of chip used. Withcommonly used chips, 32, 64 or up to110 nodes per network are possible (or128 with restrictions), whilst further nodescan be accommodated by usingrepeaters or is a multi-master system with linetopology and real-time capability.

8 Unique identifiers contain information notdirectly related to the address of aparticipant, but to the contents of amessage (such as temperature, rotationalspeed or linear speed). All participantscheck out the identifier being transmittedand decide if the type of message isrelevant to themselves. In this way, allmessages can be received from many orall of the participants simultaneously. Theunique identifier also determines thepriority of the message relating to busaccess. Should a number of participantstry to access the bus simultaneously, thehigher priority message is guaranteed togain bus format (11-bit identifier) andextended format (29-bit identifier) are twodifferent message formats that can existon the same physical CANbus . The B specification supports both formats,while CAN A only allows frames with11-bit content-oriented identifiers inthe message, the system achieves a highdegree of configuration flexibility andallows a simple extension of the networkto include further performanceNetworks of up to40m will supporttransfer rates of1 Mbit/sec Networks up to1000m in lengthwithout repeaters arepractical with rates of80 Kbit/sec or lessTel: 01234 782049 Fax: 01234 782056 Sensor-Technik UK Ltd In February of 1986, Robert Boschintroduced the CAN serial bus system atthe SAE congress in Detroit.

9 It wasdesigned to handle short messages,support multi-master access, and offer ahigh degree of reliability. In mid 1987,Intel delivered the first CAN chip, andtoday more than 20 chip manufacturersproduce devices that offer quickly gained a dominatingposition among bus protocols. In 1999close to 60 million CAN controllersmade their way into applications; morethan 100 million CAN devices were soldin the year big advantage of the CAN buscompared to other network solutions isthe price/performance ratio. Price wise,CAN is the most affordable network nextto a regular serial channel. With CAN being a pure data link layerimplementation, higher level applicationlayers have been developed to increaseCAN s suitability for use in specificareas of different J1939As a real-time CAN solution for heavyduty applications, J1939 is suited forequipment used in industries rangingfrom agriculture, construction, andfire/rescue to forestry, materialshandling, and on- and off-highway.

10 Communication systems designedaccording to J1939 standards areEMI/RFI tolerant, free of connectionwires, easy to install, and feature log,record, remote access, and self-diagnosis capabilities. The J1939standards family is maintained toensure CAN device interoperability. CANopenCANopen is a network technologyoptimised for use in industrial controlenvironments, in machine internalnetworks and in embedded systems(any control unit deeply embedded ina device with electronics). In industrialcontrol terms CANopen is a fieldbus .Some fieldbus applications usederivations from RS485 for similarembedded networks. However, withRS485 the network designer/developerneeds to invent many communicationroutines. CANopen, on the other hand,features a pre-defined set of networkcommunication s ahead for CAN?Although the CAN protocol is now 15years old, it is still being enhanced. Forexample, at the beginning of 2000 anISO task force involving a number ofcompanies defined a protocol for thetime-triggered transmission of CANmessages.