Typical control system and structure of industrial robot

- Dec 22, 2020-

Abstract: Industrial robots are composed of three basic parts: main body, drive system and control system. The main body is the base and the actuator, including the arm, wrist and hand, and some robots also have a walking mechanism. Most industrial robots have 3 to 6 degrees of freedom of movement, of which the wrist usually has 1 to 3 degrees of freedom of movement; the drive system includes a power device and a transmission mechanism to make the actuator produce corresponding actions; the control system is based on the input The program sends instruction signals to the drive system and actuators, and controls them.

Keywords: industrial robot, control system, structure system

(1) Functions to be achieved by the industrial robot control system

  The robot control system is an important part of the robot, which is used to control the manipulator to complete specific tasks. Its basic functions are as follows:

     (1) Memory function: storage of work sequence, movement path, movement mode, movement speed and information related to the production process.

     (2) Teaching function: offline programming, online teaching, indirect teaching. Online teaching includes teaching box and guided teaching.

     (3) Contact function with peripheral equipment: input and output interface, communication interface, network interface, synchronization interface.

     (4) Coordinate setting function: There are four coordinate systems: joint, absolute, tool, and user-defined. (5) Man-machine interface: teaching box, operation panel, display screen.

     (6) Sensor interface: position detection, vision, touch, force, etc.

     (7) Position servo function: robot multi-axis linkage, motion control, speed and acceleration control, dynamic compensation, etc.

     (8) Fault diagnosis safety protection function: system status monitoring during operation, safety protection under fault status and fault self-diagnosis.

(2) Composition of industrial robot control system (Figure 1)

    (1) Control computer: the dispatch and command organization of the control system. Generally, microcomputers and microprocessors have 32-bit, 64-bit, etc., such as Pentium series CPUs and other types of CPUs.

    (2) Teaching box: teaches the robot's work trajectory and parameter settings, as well as human-computer interaction, has its own independent CPU and storage unit, and realizes information interaction with the host computer through serial communication.

    (3) Operation panel: It is composed of various operation buttons and status indicators, and only completes basic function operations. (4) Hard disk and floppy disk storage: peripheral memory for storing robot working programs.

    (5) Digital and analog input and output: input or output of various status and control commands.

    (6) Printer interface: record various information that needs to be output.

    (7) Sensor interface: It is used for automatic detection of information and realizes the compliant control of the robot. Generally, it is force, touch and vision sensors.

    (8) Axis controller: complete the position, speed and acceleration control of each joint of the robot.

    (9) Auxiliary equipment control: It is used to control auxiliary equipment that cooperates with the robot, such as gripper positioner. (10) Communication interface: Realize the exchange of information between robots and other equipment, generally serial interfaces, parallel interfaces, etc.

    (11) Network interface

               1) Ethernet interface: Direct PC communication of several or single robots can be realized through Ethernet, the data transmission rate is up to 10Mbit/s, and the application program can be programmed directly on the PC with windows library functions, and the TCP/IP communication protocol can be supported , Load data and programs into each robot controller through the Ethernet interface.

               2) Fieldbus interface: supports a variety of popular fieldbus specifications, such as Device net, AB Remote I/O, Interbus-s, profibus-DP, M-NET, etc.

(3) Classification of industrial robot control system

     (1) Program control system: Apply a certain regular control function to each degree of freedom, and the robot can realize the required space trajectory.

      (2) Adaptive control system: When the external conditions change, in order to ensure the required quality or to improve the control quality with the accumulation of experience, the process is based on the observation of the status of the operating machine and the servo error, and then adjust the non The parameters of the linear model until the error disappears. The structure and parameters of this system can change automatically with time and conditions.

    (3) Artificial intelligence system: It is impossible to compile motion programs in advance, but requires real-time determination of the control function according to the surrounding state information obtained during the motion. Drive mode: See industrial robot drive system. Exercise mode:

    (4) Point type: The robot is required to accurately control the pose of the end effector, regardless of the path; (5) Trajectory: The robot is required to move according to the taught trajectory and speed.

    (6) Control bus: International standard bus control system. Use international standard bus as the control bus of the control system, such as VME, MULTI-bus, STD-bus, PC-bus.

    (7) Self-defined bus control system: The bus defined by the manufacturer itself is used as the control system bus.

    (8) Programming method: Physical setting programming system. The operator sets a fixed limit switch to realize the program operation of starting and stopping, which can only be used for simple picking and placing operations.

    (9) Online programming: The memory process programming method of operating information is completed through human teaching, including direct teaching (ie hand-to-hand teaching) analog teaching and teaching box teaching.

    (10) Offline programming: do not teach directly to the actual robot, but separate from the actual operating environment, generate a teaching program, and generate the robot's operating trajectory remotely by using advanced robots and programming languages.

(4) The structure of the robot control system The robot control system can be divided into three categories according to its control mode.

    (1) Centralized Control System (Centralized Control System): A computer is used to realize all control functions. It has a simple structure and low cost, but it has poor real-time performance and is difficult to expand. This structure is often used in early robots. 2 shown. The PC-based centralized control system takes full advantage of the openness of PC resources, and can achieve good openness: a variety of control cards, sensor devices, etc. can be integrated into the control through standard PCI slots or through standard serial ports and parallel ports. System. The advantages of a centralized control system are: low hardware costs, easy information collection and analysis, easy to achieve optimal control of the system, better integrity and coordination, and more convenient PC-based system hardware expansion. Its shortcomings are also obvious: the system control lacks flexibility, and the control danger is easy to concentrate. Once a failure occurs, its impact is wide and the consequences are serious; because the real-time requirements of industrial robots are very high, when the system performs a large number of data calculations.