CN203287747U - Absolute-type grating control system and control method based on industrial Ethernet bus - Google Patents

Abstract

The utility model discloses an absolute grating control system based on the industrial Ethernet bus. The master station of the numerical control system is sequentially connected to the IO unit, the digital spindle driver, the feed axis driver and the grating adapter slave station PDU through the industrial Ethernet bus. The grating adapter slave station PDU is connected with an X-axis linear grating, a Y-axis linear grating, a Z-axis linear grating and an angle grating. The grating adapter slave station of the utility model can be flexibly adapted to various grating devices, can realize higher communication throughput, communication rate and shorter communication period, and can realize direct high-speed cross communication between the servo system and the grating device, which is a closed-loop vibration The implementation of the suppression function provides simple and powerful technical support. At the same time, the closed-loop control system of the utility model adopts a ring topology, which is easy to connect, and the slave station equipment can be flexibly expanded. The closed-loop control system has multiple system protection functions to ensure safe and effective operation of the system.

Description

Absolute Grating Control System Based on Industrial Ethernet Bus

technical field

The utility model relates to the technical field of industrial Ethernet, in particular to an absolute grating control system based on the industrial Ethernet bus.

Background technique

An automatic control system that consists of a signal forward path and a feedback path to form a closed loop, also known as a feedback control system. This is an automatic control system that includes power amplification and feedback so that the value of an output variable responds to the value of an input variable. After the numerical control device sends out the command pulse, when the command value is sent to the position comparison circuit, if the workbench does not move at this time, that is, when the position feedback signal remains unchanged, the difference between the command and the feedback is amplified by the amplifier to make the servo motor rotate. Transmission components such as ball screw nut pairs drive the machine tool table to move. The position measuring element installed on the machine tool workbench measures the actual displacement of the workbench, and feeds it back to the comparator of the numerical control device for comparison with the command signal, and uses the compared difference for control. If there is a difference between the two, it will be amplified by the amplifier, and then the servo drive motor will be controlled to rotate until the difference is zero, and the table will stop moving.

The current grating closed-loop control mainly adopts two methods: 1. The servo drive directly has a grating control interface; 2. The field bus is used to communicate with the grating through the grating adapter.

Method 1 mainly has the shortcomings of not being able to flexibly adapt to various grating devices, it is difficult to realize multiple system protection functions, and increases the computing load of servo drives; method 2 mainly has the disadvantages of low fieldbus communication rate and small amount of communication data, which is difficult to implement Disadvantages of high-speed cross-communication of servo system and raster device data.

Utility model content

The purpose of the utility model is to overcome the shortcomings and deficiencies of the prior art, and provide an absolute grating control system based on the industrial Ethernet bus.

In order to achieve the above object, the utility model adopts the following technical solutions:

The utility model is an absolute grating control system based on the industrial Ethernet bus, and the numerical control system is connected with each slave station device in a ring topology through the industrial Ethernet bus. The slave station includes sequentially connected IO units, digital spindle drivers, feed axis drivers and The grating adapter slave station PDU, the grating adapter slave station PDU is connected to the linear grating and the angle grating.

Preferably, the grating adapter slave station PDU includes an FPGA master chip, a serial memory EPCS and SDRAM memory, an Ethernet physical chip and dual network interfaces, power conversion, and a grating device serial interface.

Preferably, the FPGA main chip adopts the system-on-chip SOC technology, which can flexibly configure the software and hardware system framework, and the hardware framework structure includes a soft-core main CPU, an internal RAM connected to the soft-core main CPU, a timer, an industrial Ethernet protocol interface and The grating communication protocol module interconnects and communicates through the internal Avalon bus; the soft-core main CPU controls the program, communicates with the grating device in real time through the grating communication protocol module and the grating interface, and communicates with the master CNC system in real time through the industrial Ethernet protocol interface , Feedback the grating device data information to the main system in real time.

Preferably, the digital spindle driver is connected to the spindle motor, the feed axis driver is connected to the feed axis motor, and the IO unit is connected to input and output signals, and interacts with the main system through an industrial Ethernet interface to exchange data in real time to effectively control the movement of the motor and normal operation of IO signals.

Compared with the prior art, the utility model has the following advantages and effects:

1. The grating adapter slave station can flexibly adapt to various grating devices, and can achieve higher communication throughput, communication rate and shorter communication cycle.

2. Direct high-speed cross-communication can be realized between the servo system and the grating device, providing simple and powerful technical support for the implementation of the closed-loop vibration suppression function.

3. The closed-loop control system adopts ring topology, which is easy to connect, and the slave station equipment can be flexibly expanded.

4. The closed-loop control system has multiple system protection functions to ensure the safe and effective operation of the system.

Description of drawings

Fig. 1 is the system topology connection diagram based on the industrial Ethernet bus of the utility model;

Fig. 2 is a schematic diagram of the software and hardware structure of the grating adapter slave station;

Figure 3 is a block diagram of the dual position loop control of the utility model;

Figure 4 grating adapter (Endat2.2/Feedat2.0) slave station control software processing flow.

Detailed ways

The utility model will be further described in detail below in conjunction with the embodiments and accompanying drawings, but the implementation of the utility model is not limited thereto.

Example

As shown in Figure 1 and Figure 2, this embodiment is based on the absolute grating control system of the industrial Ethernet bus, and the numerical control system is connected to each slave station device in a ring topology through the industrial Ethernet bus. It is characterized in that the slave stations include sequential connections IO unit, digital spindle driver, feed axis driver and grating adapter slave station PDU, the grating adapter slave station PDU connects linear grating and angle grating.

The grating adapter slave station PDU includes FPGA main chip, serial memory EPCS and SDRAM memory, Ethernet physical chip and dual network interface, power conversion and grating device serial interface.

The FPGA main chip adopts the system-on-chip SOC technology, which can flexibly configure the software and hardware system framework. The hardware framework structure includes a soft-core main CPU, an internal RAM connected to the soft-core main CPU, a timer, an industrial Ethernet protocol interface, and a grating communication protocol. The modules are interconnected and communicated through the internal Avalon bus; the soft-core main CPU controls the program, communicates with the grating device in real time through the grating communication protocol module and the grating interface, and communicates with the CNC system of the master station through the industrial Ethernet protocol interface in real time. Equipment data information is fed back to the main system in real time.

The digital spindle driver is connected to the spindle motor, the feed axis driver is connected to the feed axis motor, and the IO unit is connected to the input and output signals, and communicates data with the main system in real time through the industrial Ethernet interface to effectively control the movement of the motor and the IO signal of normal operation.

As shown in Figure 4, the absolute grating control method based on the industrial Ethernet bus in this embodiment includes the following key features:

(1) The ring topology connection between the CNC system master station and the servo, digital spindle, IO and grating adapter slave stations based on the industrial Ethernet bus. The system master station automatically recognizes the type of each slave station at the initial stage, and Periodic communication is carried out. For the specific connection method, refer to the system topology connection diagram of the industrial Ethernet bus in Figure 1.

(2) Each grating adapter slave station can connect up to 6 absolute grating devices, and can expand the grating adapter slave station through industrial Ethernet. The absolute gratings currently supported include Heidenhain absolute gratings based on Endat2.2 and Feedat2.0-based absolute gratings Refer to Figure 2 for the hardware design framework of the Fagor absolute grating and grating slave station. The grating adapter slave station adopts the Quartus-ii and SOPC Builder development environment provided by AlteraFPGA to establish a system hardware project. The specific hardware project includes: soft-core CPU, EPCS memory chip , on-chip RAM, SDRAM, Endat2.2 protocol provided by Heidenhain manufacturer or Feedat2.0 protocol provided by Fagor manufacturer, and GSK-Link industrial Ethernet protocol, etc., are connected to each other through Avalon bus to realize FPGA-based SOC software and hardware The system, without changing the hardware, can flexibly support absolute grating devices with protocols from various manufacturers.

(3) After the absolute grating slave station is powered on, the software initializes the peripheral equipment of the system, sets the communication parameters of each grating device, and automatically reads information such as the ID of each grating device, the type of the grating, and the accuracy of the grating, and starts the grating cycle data cycle to interrupt communication ; and through the GSK-Link industrial Ethernet bus, send parameters such as the type of each absolute grating device to the CNC system master station, and then enter the normal communication process.

(4) The PDU slave station system periodically reads the position data of each grating device, and converts it into the actual absolute machine tool position according to the grating type and grating accuracy information obtained in (3), and real-time through the industrial Ethernet bus Feedback to the CNC system.

(5) While the system periodically reads the position data of each grating device, it also obtains the operating status of the grating. When the grating device alarms abnormally, it also feeds back to the CNC system in real time through the industrial Ethernet bus to ensure the safe operation of the system.

The absolute grating control method based on the industrial Ethernet bus can realize the full closed-loop control method of the absolute grating system, including the following key features:

(1) Through the industrial Ethernet bus, the CNC main system takes the absolute position of each grating device fed back as the actual coordinate position of the system machine tool at the initial stage; during the normal operation of the system, the absolute position of each grating device obtained from the system command position and cycle Feedback position data is processed by position PID closed-loop, and the calculated speed command controls the normal operation of the servo slave station system.

(2) Each grating axis device can be enabled or disabled by parameter selection. When the grating device is selected as invalid, the axis control will automatically enter the semi-closed loop control, but the corresponding grating position data can be processed through diagnostic display, which is beneficial for users to debug the grating device.

(3) The position and direction of the grating can also be selected by parameter setting, so it can ensure the effective operation of the PID position closed loop and prevent the abnormal situation of PID positive feedback due to installation and other reasons.

(4) The system realizes the dual position loop function to solve the situation that the machine tool may vibrate when it runs at a higher speed for a machine tool with a relatively large gap under full closed-loop control. Referring to Fig. 3, high control performance like a semi-closed loop is obtained while the machine tool is moving, and high-precision positioning using grating detection is used when stopping.

(5) The system provides the function of setting the zero point of the machine tool. When setting the zero point of the grating, the zero point offset of the set grating is stored in the ferroelectric memory of the CNC system, and it will not disappear even if the system is powered off. In this way, the difference between the periodic feedback grating position and the zero offset value is the actual grating feedback position.

(6) In order to effectively protect the safe operation of the system, in addition to providing the alarm function of the grating device, since the servo encoder adopts an absolute encoder, the difference between the coordinate value of the feedback absolute grating ruler and the coordinate value fed back by the servo encoder exceeds the parameter setting When the allowable range is exceeded, an alarm is generated to ensure the safety of the system operation.

(7) The system has two parameters, static tolerance and dynamic tolerance, which can play two roles: a. When the system is initialized, when the position value of the command and the absolute position value of the feedback grating are within the range of the static tolerance parameter , the system PID closed loop automatically adjusts the grating position value to the commanded position value, otherwise the system command value follows the grating feedback position value. b. When the system is stationary, the maximum allowable deviation is the static over-tolerance parameter value; when the system is in motion, the maximum allowable deviation is automatically switched to the dynamic over-tolerance parameter value, if the deviation between the system command position value and the grating feedback position value When the maximum deviation allowed is exceeded, an over-tolerance alarm will be generated to protect the system.

(8) There are two main types of absolute grating rulers: linear grating and angle grating. The feedback value of the linear grating is consistent with the command value of the system, so PID closed-loop processing can be directly used; while the feedback value of the angle grating always changes within 0 to 360 degrees, but the command coordinate value may be inconsistent with it, so it cannot be directly processed. With PID closed-loop processing, it is also necessary to perform corresponding matching and conversion processing on the feedback grating coordinate values. Conversion method: get the multi-cycle value from the system command coordinates, multiply the multi-cycle value by 360 degrees, and add the coordinate value of the grating feedback to get the converted machine tool feedback coordinate value. At this time, PID full closed loop or double position loop can be performed. operation. It should also be noted that the feedback coordinate value of the raster may jump between 0 degrees and 360 degrees. At this time, the obtained machine tool feedback coordinate value may have a calculation difference of 360 degrees from the command coordinate value, so this needs to be considered The value after the factor is the actual machine tool feedback coordinate value.

(9) The communication protocol between the CNC system and the absolute grating slave station is protected by a two-way handshake flip signal, that is, the command control word of the CNC system and the feedback control word of the grating slave station flip handshake each time, so that each normal communication data Both have flip handshake signals to further ensure the data correctness of system communication.

(10) For the angle grating described in (8), in the case where the rotation axis is always moving in the same direction, in order to ensure the calculation accuracy of the system and prevent the problem of data overflow, the system needs to adopt double-precision floating-point PID closed-loop operation. For this purpose, FPGA hardware is used to realize the closed-loop position control function, which can greatly reduce the system load, and obtain a shorter closed-loop control cycle and system real-time communication cycle, thereby ensuring the effective operation of the closed-loop control.

(11) Grating vibration suppression is a problem that needs to be solved in the fully closed-loop grating control. Since the dual position loop control method mentioned in (4) will result in loss of precision in the machining process, full closed loop control must be used. However, due to the acceleration and deceleration control of the machine tool, there will be a Torsional deformation sometimes produces speed difference and causes vibration of the machine tool. Therefore, the speed fed back by the grating device (that is, the speed of the machine tool) needs to be fed back to the servo system in real time through the bus cross-communication. The difference between the servo motor and the mechanical speed is used as the current (torque) Control considerations to avoid machine tool vibrations.

The above-mentioned embodiment is a preferred implementation mode of the present utility model, but the implementation mode of the present utility model is not limited by the above-mentioned embodiment, and any other changes, modifications and substitutions made without departing from the spirit and principle of the present utility model , combination, and simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present utility model.

Claims (4)

1. An absolute grating control system based on the industrial ethernet bus, connected by the numerical control system with each slave station device in a ring topology through the industrial ethernet bus, it is characterized in that the slave station includes sequentially connected IO units, digital spindle drivers, Feed shaft drive and grating adapter slave station PDU, said grating adapter slave station PDU connects linear grating and angle grating. the 2. the absolute type grating control system based on industrial ethernet bus according to claim 1, is characterized in that, described grating adapter slave station PDU comprises FPGA main chip, serial memory EPCS and SDRAM memory, Ethernet physical chip and Dual network interfaces, power conversion, and serial interface to encoder devices. the 3. the absolute type grating control system based on industrial ethernet bus according to claim 1, is characterized in that, described FPGA main chip adopts system on chip SOC technology, can flexibly configure software and hardware system framework, and hardware framework structure comprises soft core The main CPU, the internal RAM connected to the soft-core main CPU, the timer, the industrial Ethernet protocol interface and the grating communication protocol module are interconnected and communicated through the internal Avalon bus; the soft-core main CPU controls the program through the grating communication protocol module and the grating The interface communicates with the grating device in real time, and communicates with the CNC system of the main station through the industrial Ethernet protocol interface in real time, and feeds back the data information of the grating device to the main system in real time. the 4. The absolute grating control system based on the industrial Ethernet bus according to claim 1, wherein the digital spindle driver is connected to the spindle motor, the feed axis driver is connected to the feed axis motor, and the IO unit Connect the input and output signals, exchange data with the main system in real time through the industrial Ethernet interface, effectively control the movement of the motor and the normal operation of the IO signal. the

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