Servo Motor Based on CAN Bus Communication Control

1. Introduction

CAN (Controller Area Network) bus is an effective support for distributed control or real-time control of the serial communication local area network, due to its high-performance, high-reliability, real-time and its unique design, has been widely used in the control system data communication between the detection and the implementing agencies, the rise in the industrial areas of application craze.

servo motor structure is compact, easy to control, stable operation, fast response excellent properties, has increasingly become an important modern industrial automation systems actuator. The high degree of automation, need precise control of speed, position, torque and other occasions, such as printing machinery, paper machinery, textile machinery, industrial robots, high-speed elevators, CNC machine tools and other important industries have been widespread applications.

Germany Lenze servo motor production due to the CAN bus interface, it easily hooked up to the CAN bus via the CAN bus data transfer and control, expanded functionality and application range of the servo motor, servo motor more more flexibility for modern industrial control systems.

2. CAN Bus characteristics

As a dedicated network used in the field of industrial automation, CAN bus has the following advantages:

(1) Use simple and convenient. Many CAN controller chip such SJA1000T, Philips 82C250 CAN physical layer and the data link layer in use when the user needs to do only two things: to initialize the CAN controller, CAN bus data for send and receive operations.

(2) highly efficient and reliable. CAN uses short frame structure, the data frame length of the data field up to 8B, the transmission speed (the maximum communication rate of up to 1Mbps), low probability of interference. Meanwhile, CAN bus as a multi-master node, each node by bus arbitration control of the bus, and has improved error handling mechanism to ensure the safe and reliable interference environment data transmission.

(3) system scalability. CAN bus is the encoding of the message-oriented, rather than equipment-oriented coding, it is very convenient and flexible to add or delete a CAN node, easy system expansion.

3. Servo motor access CAN network

Lenze servo motor servo controller provides dedicated CAN bus interface X4 Like other CAN nodes, using ordinary twisted pair as a communication medium is easily connected to the industrial control system based on CAN bus

Lenze servo controller and the servo motor between the use of the rotary transformer or the photoelectric encoder to create feedback to form a high-precision servo control system, the servo motors in real time to its running status and operation information uploaded to the servo controller. As a node on the CAN bus, the servo controller can not only communicate with the host host PC to receive through the CAN bus operation, control and parameter setting command; servo controller also fast data exchange between mutual coordination or control relationship.

Host host patch support CAN communications adapter card supports CAN bus, is responsible for the management of the entire operation of the system and work status monitoring. CAN bus has been widely applied in the industrial control, many companies have launched a support CAN bus interface adapter card, such as Advantech PCL-841 communication card, Beijing the HK-CAN20 Huakong communication card, Beijing Sanxing The company Intelligent CAN-PC bus adapter card PCCAN and so on, the user can through these interface adapter, to run the complex task of communication, digital communication and coordination and management between the CAN node with the host host.

4. Servo controller function module based on CAN bus data channels

Lenze servo dc motor servo controller with internal function module library, such as the common logic function modules, the arithmetic function modules, the type of signal conversion module, ramp function module, phase the integral module as well as special number frequency input and output modules , the number of frequency processing module, the servo control processing modules, the speed setting processing module, and so on. Users use of these functional blocks can be freely configured flow of signals of the controller so that the controller can be easily adapted to different practical applications.

In order to achieve based on CAN bus applications, the servo controller provides a dedicated CAN bus module group CAN-IN with the CAN-OUT data channels as a process, process data transmission. Among them, the function block CAN-IN1 and CAN-OUT1 only for communication and data transfer between the servo controller with the host host. CAN-IN1 input function block for receiving the upper host data information, CAN-IN1 8B of the data space available for the user configuration, the binary signal can be provided to other internal functions module, the 16-bit analog signal, a speed signal 16 as well as a 32-bit phase signals and other control signals. Upper host to configure the CAN-IN1 practical application module to send commands to achieve servo motor speed for a given motor fast stop motor reversing switch, the normal mode of the motor speed and constant low speed switching, motor enabled motor is not allowed and other various functions. Similarly, CAN-OUT1 function module also 8B data space available to the user to provide real-time motor status information, the actual speed of the motor, the motor of the actual phase can configure up bit host.

Function blocks CAN-IN2, CAN-IN3 and CAN-OUT2 CAN-OUT3 used for servo controller for rapid data exchange between. As long as the configuration of a servo controller of the CAN-OUT2 or CAN-OUT3 correspondence relationship with another servo controller CAN-IN2 or CAN-IN3, can establish a data transmission channel between the servo controller, the motor is running. during a servo controller data information to another servo controller common: the speed of the servo controller given by computing processing speed as another servo controller given signal, so that the ratio of 2 servo motor speed run. This feature is for the coordination between the multiple servo motor control is important. Host host can monitor the transmission of such data on the CAN bus.

At the same time, the servo controller also offers 2-way parameter parameters of input channels and 2 output channels. CAN bus, the host host by 2 the road parameters input channel, set to modify various parameters of the servo controller, such as the acceleration and deceleration of the servo motor, gear box speed ratio, level contact number, etc.; 2-way parameter output channel reading the various parameters of the servo controller, such as the current temperature of the servo motor, the current configuration of the acceleration and deceleration time, and the actual motor voltage and current, etc., so long as it is able to find the parameters of the code table of the servo controller the parameters are basically able to read.

Own related data information through the CAN bus interface and the respective data channel, the servo motor can be transmitted to the CAN bus; also can receive the various data required by the servo motor manufacturer from the bus information and control commands.

5. CAN communication protocol

High as the real-time requirements of industrial control the underlying network, CAN protocol is divided into three layers: the physical layer, data link into the layer and application layer. There are four different frame formats: CAN communication protocol data frame, remote frame, error frame and overload frame.

In practical applications due to the CAN communication protocol is given only the common requirements need to be protocol specific, and to create the applicable rules of the protocol. According to the characteristics of the servo motor servo controller and follow the CAN communication protocol standards developed servo controller communication protocol rules. The servo controller of each information frame is divided into two parts: a header and data fields. Header 2B, the front 11 as an identifier, and then an RTR bit, and finally the data length of 4 bits DLC (i.e. issued by the actual length of data, in bytes). The data domains occupancy 8B. 11-bit message identifier reaction priority level of the nodes, bus arbitration is achieved through it, the identifier of the information frame is smaller, and the information frame has a higher priority. In addition to the the bus state special information, the servo controller identifier of the information transmitted by the formula:

Information identifier = reference identifier + set controller node address

Servo controller node address can be set in the parameter code table. Provisions of the uniform of the reference identifier of the information, the servo controller, such as: synchronous trigger signal a reference identifier is 128, the reference identifier from the controller information of the channel of the CAN-OUT1 384, and transmitted to the controller CAN -IN1 information of the channel of the reference identifier is 512, and sent to the controller via the parameter channel 1 reference identifier is 1536, and received information via the parameter channel 1 reference identifier is compared to 1408.

For the 8B data fields, users need to use the principle to be followed in accordance with the specific information to be sent to. For example, via the parameter channel parameter settings, one byte command code byte parameters corresponding index number 2, 3, 4 bytes for the parameter corresponding times index after four bytes is the size of the parameter to be set data; want to send information to a servo controller of the process data channel CAN-IN1, direct data transmission, there is no command code, and no index number.

6. The upper host of software design

Communicate via the CAN bus control servo motor control signal flow in the internal the configured servo controller for the actual application requirements, and based CAN interface function modules and data channel, and the rest need to be addressed to the host host software design problems.

Because the host host plugged CAN communications adapter generally provide the driving function of the CAN, in the process of preparation of PC software, with the CAN bus communication part can directly call the appropriate function As host and CAN communication main tasks: the initialization of the CAN adapter, CAN packet send CAN packets reception, there are ready-made function can be used to provide a convenient user CAN communicate. CAN communication adapter card initialization initialize the various registers of the adapter card, set interrupt vector, the necessary parameters of the baud rate of the communication card, and the interrupt mask, to make preparations for the normal communication. CAN packet transmission, we must first determine the 11 information packet identifier, fill in the header, and fill in the need to send the data in the data field, sent to all CAN nodes or specific CAN node by sending function on. For the use of the receive function of the received CAN message packet through its 11 information identifier, to determine its source, for processing the data of the data fields, to obtain a valid information to be displayed or stored, and in accordance with the control needs to send control commands .

Host host It is through the CAN driver function continues to call, send control command or parameter setting command to the induction motor servo controller, drive servo motor start and stop operation; receive from the speed of the servo motor servo controller phase, the direction of rotation, torque, and other various data and state information, and analysis processing, and then follow the actual control of the system need to give the servo controller sends the appropriate commands to drive the motor, the servo motor run always by user the requirements change, enabling the management and control of the servo motor.

Lenze servo motor CAN interface introduced to improve the level of automation of the servo motor, communication and control in the industrial control network is more convenient, flexible and reliable servo motor.

CAN bus is more widely used in modern industrial control systems, servo motor with CAN interface provides a broad application prospects.