Introduction
In the modern warfare, along with the weaponry system’s motorization, automated and the informationization degree’s unceasing enhancement, on army vehicle’s Che Zai the equipment also unceasingly increases, many equipment like trailer-mounted radars, the vehicle carry the optical sight equipment, the vehicle to carry the weapon equipment and so on, needs a stable horizontal platform to take the base, guarantees armament system’s aiming, the track and the precise attack. At the same time, along with networking’s unceasing development, in the vehicles system’s network degree is also getting higher and higher, this requests Che Zai the equipment to be able to carry on the interconnection with other equipment, thus is advantageous in forms the complete bikes supervisory system. At present, the majority equipment carries on the connection in the vehicles through the CAN main line, but its application layer agreement has brought the difficulty not unified for the different manufacturer’s between equipment interconnection.
CANopen is based on CAN (Controller Area Network) main line’s application layer agreement, it by is engaged in the industrial control CiA (CAN in Automation) the member to develop at first. Because CANopen is one kind public, open, the general agreement, moreover concise transparent, easy to develop, therefore after issue soon has obtained the widespread acknowledgment. Now was accepted was already one of CAN high-level agreement standards. Especially in Europe, the CANopen agreement was considered that is in occupies the leading positions based on the CAN industrial system the standard, already applied in many kinds of domains, like all-terrain vehicle, the marine electronic installation, the medical equipment even may also apply in the bus and the railroad, and in view of the profession application, realizes is quite succinct.
At the same time, applies CANopen in the vehicle carries the platform installment, may cause it to hang very conveniently receives on the main line, has like this not only solved interconnection problem between equipment’s, simultaneously also enhanced the intelligence transmission reliability, timely and equipment’s standardization, the opening degree. On the other hand, was already widespread in the overseas CANopen application, but are also very few in the domestic related CANopen article, hoped that to the personnel who is engaged in the CAN bussing technique development supplies some useful information taking advantage of this article, will cause our country’s CAN main line application soon and the international trail connection.
First, CANopen agreement design essence and central content
CAN is in the OSI network model the physical level and the data link layer, but CANopen is based on the CAN application layer, because the field bus usually only includes a webpage, therefore does not need 3rd (transmission level) and 4th (network level), also does not need 5th (conversation level), 6th (description level) function. Is precisely because had the CANopen such application layer agreement existence, thus caused the CAN main line to become a more perfect network system.
1.1 CANopen agreement design essence–Object-oriented
The CANopen agreement in designs, transmitted the data to the main line on to carry on the classification, namely each transmission data was some specific kind of object, thus has realized the object-oriented programming. Each kind of transmission object has its standardized form in CANopen, thus has realized in the application layer structure unification. Like this regardless of from standardized angle, says from the modularized program design angle, the CANopen agreement is a design quite perfect agreement.
Has defined 4 kind of objects in the CANopen agreement’s data transmission Chinese Communist Party (communication pattern), respectively be management object (NMT), service data object (SDO), process data object (PDO) and special function object. And NMT uses for to transmit the master node to the entire network system’s management information, SDO uses for to transmit in network system’s disposition information, PDO uses for to transmit the process data information (e.g. voltage change value), special function object including synchronized object (SYNC), urgent object (Emergency), time reference (Time-Stamp) and so on. Time each kind of object transmission’s frame form has the detailed stipulation in the reference, was not detailed in here introduced. In actual project user, so long as according to the need, must transmit according to a kind of stipulation the data mapped in the corresponding object to be possible.
In 1.2 CANopen agreement central content–Object dictionary (Object Dictionary)
To carry on standardized and the convenience management to each kind of object, has defined the object dictionary concept in the CANopen agreement. It is an order object group, has defined an equipment’s all information, each equipment must have an only object dictionary in the CANopen network system, each equipment’s object dictionary has the structure to be the same, content different characteristic. Through to object dictionary’s object definition only 16 main indices and 8 seat indices, may conveniently in the access object dictionary object. In the CANopen agreement has defined the general object dictionary structure, has stipulated each kind of data in the object dictionary location area. In we establish the equipment object dictionary time, the prime task should concentrate in the definition communication sub-agreed territory (1000~1FFF) and the manufacturer special stator agreed territory (2000~5FFF) part.
The object dictionary played in the entire CANopen agreement has connected the DLL module (communication connection) and the application procedure role. If we want (for example the I/O input value) to deliver an application procedure in data on the CAN main line, we must first determine that which kind of object this data does belong to object dictionary (e.g. I/O mouth input value should for process data object), then the corresponding object and transmits with the DLL module access object dictionary in it according to the corresponding frame form to the CAN main line comes up, thus has completed the data transmission.
Second, the vehicle carries platform data communication system’s realization
2.1 data communication system’s composition
In ours leveling system, the platform uses 4 supports, by 4 1KW, the 24V direct current machines and the reduction gear, the T guide screw connects, in control platform 4 pivot rises or drop. The master-control unit, 4 electrical machinery controller and USB-to-CAN are connected through the CAN main line, the horizon sensor and the hand hold are connected through the RS232 connection and the master-control unit, its structure as shown in Figure 1. And the master control, the electrical machinery controller and the hand hold the embedded equipment which develops voluntarily for us, the electrical machinery controller may realize the accurate electrical machinery position control, the hand holds may provide the manual leveling function. The horizon sensor is CXTD02 which Crossbow Technology Corporation produces, it may send out the precise platform X, Y axis angle mil information by the RS232 mouth; The USB-to-CAN equipment USB-to-CAN compact which produces for German IXXAT Corporation, contained SJA1000 the CAN controller to be possible to complete the news receiving and dispatching, and might signal transmit CAN the signal conversion USB for the superior machine, the superior machine through moved the data which IXXAT Corporation’s surveillance software (miniMON) might on the online observation main line transmit.
in 2.2 systems CAN hardware interface design
The microprocessor uses FUJITSU in the master-control unit and in the electrical machinery controller Corporation’s MB90F543 chip, in itself has inlays the CAN controller, therefore only need add a CAN main line driver, may realize the master-control unit and between 4 electrical machinery controller’s correspondence conveniently. In this system has selected the PCA82C250 receiving and dispatching controller, this chip provides to main line’s differential motion transmission ability and to the CAN controller’s differential motion receptivity, PCA82C250 is the standard CAN transceiver, the experiment demonstrated that so long as main line’s each meter electric capacity is smaller than under the 120pf condition, satisfies the CAN bus transfer distance the standard. The CAN main line actuates the circuit diagram slightly. In order to strengthen main line’s antijamming ability, main line’s correspondence medium uses the belt shielded wire’s twisted pair line.
2.3 object dictionary establishment
Each equipment must have an only object dictionary in the network system, has defined each kind of object attribute (for example ID, the transmit mode and so on). Altogether has 5 nodes in ours system, they by the host from the way work (1 master node and 4 from node), the master-control unit correspondence master node, 4 electrical machinery controllers correspond 4 from the node. Convenient which expands for the system, we suppose 4 from the node node number respectively are 10, 11, 12, 13, uses the pre-definition connection centralism stipulation in each node object dictionary’s object ID 11 ID, it is composed of 4 function codes and 7 node numbers.
Below take master node object dictionary establishment as example explanation object dictionary establishment method. Must first analyze the master node in the network function, thus which kind of object in the determination object dictionary can contain and the integer, then definition object attribute. The master node must support in ours system from the node visit, therefore needs SDO; The master node must transmit the positional information to 4 from the node, must therefore have 4 Tx-PDO and 4 Rx-PDO, each PDO two parts is composed of Tx(Rx)PDO Parameter and Tx(Rx)-PDO the mapping; When in the system has the emergency case time master node to transmit the urgent information, must therefore have 1 emergency instruction urgent object (Emergency Object); To from node transmission positional information preservation in manufacturer special stator agreed territory in (2000~5FFF); Moreover the master node must complete one by one from the node supervisory work, therefore must have the NMT administration module. SDO, the PDO attribute establishment like table 1, 2 show, because 4 pair of PDO attributes do not use besides the mapping value, other attributes basic same, therefore only has given to (from) the node number is 10 from node transmission (receive) PDO establishment.
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Table 1
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Table 2
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Transmits the type 255 expressions in table 2 asynchronous, the event triggering transmission, mapping parameter 0×20000110 according to order from left to right expressed separately the main line takes as 2000H the object dictionary, the sub-index is the 01H 16 figure value (10) maps in PDO. That is will preserve, in the 2000H place positional information maps in PDO to transmit.
After the object dictionary establishment completes must produce EDS (Electronic Data Sheet) to describe this equipment’s object dictionary, master node EDS as shown in Figure 2.
2.3 DLL module realization
MB90F543 has two CAN controllers respectively is CAN0 and CAN1, we only use CAN0, such CAN1 may when the system expansion uses. The CAN controller has the following characteristic:
- Conforms to standard CAN2.0A and CAN2.0B;
- Support through receive long-distance frame transmission data;
- 16 receive, sends the buffer, each buffer has 29 bit ID and 8 byte data, multistage cushion dispositions;
- Each buffer support standard frame and expansion frame many kinds of filtration way;
- The baudrate may from 10Kbit/s to 1Mbit/s.
Uses standard CAN2.0A in our system, the baudrate is 125k/s, and for each kind of message distribution independent buffer, has done this may reduce the interrupt routine the process time, thus enhanced system’s timeliness.
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The DLL module is between the object dictionary and the CAN controller’s communication connection, it must complete the prime task is:
- Carries on the initialization to the CAN controller, including the baudrate establishment and the CAN register initialization and so on;
- To CAN initiation interrupt processing, including:
- 1) when transmission transmits through the access object dictionary each kind of object according to the stipulation frame form to the main line on;
- 2) in receive time the object information which receives writes about the object dictionary in the relevant position.
We use two function - DLL_InitCAN () and DLL_Interrupt() realize the CAN controller’s initialization and the interrupt processing function.
2.4 master-control unit’s application procedure flows
Is disposed one by one in the system from the node the node monitor condition, the master node through examines 4 to judge from node transmission periodic palpitation text (Heartbeat) one by one from the node active status.
Master-control unit’s application procedure flow is: After system electricity the master-control unit first judges one by one from the controller whether to send out the Boot-Up news, if has the Boot-up news to let enter the Operational condition from the node to connect in parallel fashion one by one is judging whether to have palpitation text (Heartbeat) to produce judges various nodes whether to succeed enters the Operational condition, otherwise is wrong through the indicating lamp newspaper, then the gathering horizon sensor outputs X, the Y axis mil information and judges whether in the erroneous belt, then to resolve the position which through the leveling strategy 3 electrical machinery should upper shift or under move (3 spots then to solve a plane), and transmits through the CAN main line the positional information for the electrical machinery controller, electrical machinery controller in movement corresponding positionThe backward master-control unit sends out the confirmation news, the master-control unit after receiving the confirmation news, gathers the position signal which once more horizon sensor outputs, if the position error stops in the erroneous belt model of domestic virtue data transmission, otherwise circulates the above process. Its flow chart as shown in Figure 3.
3 experimental results
The entire platform has achieved the satisfactory effect in the leveling process, the leveling time in 2min, the leveling precision can achieve 3 ‘, this from, on the one hand has confirmed the communication system’s reliability. To the observed data transmission process, we may real-time demonstrate the data transmission intuitively through movement monitor program (miniMON) in the superior machine the entire process, regardless of this says from the system debugging aspect from the system test aspect is very meaningful. Time systems operation’s data communication as shown in Figure 4. Through the surveillance data’s transmission, we may even more confirm the data transmission the reliability.
4 concluding remark
The vehicle carries equipment’s network, the standardization is composes the vehicle to carry a supervisory system’s important condition, simultaneously is also the vehicle carries an important direction which the equipment develops. The CANopen agreement takes the CAN main line’s application layer agreement, has the broad application prospect in the vehicles domain. This article through carries the vehicle the platform to make tallies the CANopen agreement standardized installment, thus strengthened equipment’s extendibility simultaneously also to enhance the data transmission reliability, might satisfy in the modernized war the army vehicle to carry equipment’s request.
