PLC Control Gantry Crane
Key Points of PLC Control System Design of Gantry Crane
First, the design process
Gantry Crane PLC system design, mainly includes the following links:
1, fully understand the various types of Gantry Crane production process structure, principles, conditions and characteristics.
2, fully understand and determine the functional control requirements of the user. General users, especially those who are not familiar with the characteristics of PLC users, early functional requirements is not complete, and some may also be difficult to achieve. On the basis of understanding the controlled object, take the initiative for the sake of users, introduce the PLC features, for those who do not need to add additional hardware costs and can give full play to the potential of PLC functions, such as automatic counting, equipment operating time record For users to consider; for those who spend a lot of money to achieve, and the effectiveness of the function is not explained to the user, in respect for the views of users on the basis of coordination.
3, to determine the hardware structure of the system except for PLC devices: including all the control functions to achieve the necessary sensors, switch button, actuator and alarm instructions, such as input and output devices.
4, draw the timing diagram and state diagram and other functional flow chart. Depth analysis of system functions, lay the foundation for programming.
5, PLC device selection:
1) the analysis of the system itself needs:
① Determine the number and type of I / O ports required by the system.
② determine the CPU should be the main function.
③ determine the size and type of memory capacity.
④ According to the scene to determine whether the need for remote I / O.
⑤ consider the system work environment requirements.
2) Market Product Analysis:
See which models meet technical requirements, which can basically meet the requirements, in these models, and then the price comparison and measurement, and comprehensively consider the reliability of the product, the timeliness of supply and after-sales service reputation , From which to select the ideal product.
6, the application design and simulation debugging, because the PLC all the control functions are through its application (or user program) and the implementation of the implementation. Therefore, the program design is undoubtedly the key link of PLC application system. Should make full use of PLC various simple and efficient programming instruction function to program.
PLC programming technology points:
① List PLC input / output channel assignment table.
② According to functional flow chart to draw the program flow chart and program structure functional block diagram.
③ program elements used to register at any time, easy to check and avoid duplication.
④ more use of internal relays, to avoid too complex mixed-logic.
⑤ attention to consider the functional requirements of the system did not think of the problem, such as interlocking, interlocking.
⑥ to modify and simplify the program.
⑦ Program the input PLC and use the analog I / O device in accordance with the control requirements for analog debugging.
7, the real machine on-site joint debugging.
This is a complex, complex, and indispensable task that requires the close cooperation of Gantry Crane manufacturers, control equipment manufacturers, users and design and commissioning personnel.
① PLC control cabinet and Gantry Crane on a variety of electrical equipment, the implementation of components connected to determine the accuracy, you can carry out real-site joint debugging.
② First of all, the commissioning of the control loop of each mechanism is carried out to check whether the operation of various relay contactors complies with the logical requirements of each Gantry Crane body, and whether the alarms of various faults are accurate. Otherwise, the application program is modified in the field until accurate.
③ close the main circuit switch mechanism, the body of the no-load test, methods and steps with ②.
④ The final load test machine, the load test must be light load, half load and rated load of the order of progressive, until the entire operation of the equipment in full compliance with the technical specifications of the requirements, in line with national lifting and transport machinery The relevant norms and standards, and ultimately get the user’s approval.
Second, should pay attention to the problem
In order to improve the reliability of the system, in the design process, should pay attention to the following aspects:
1, so that the output module (port) of the load to leave some room. PLC device itself is the most vulnerable to damage the output module is the component. The easiest way to reduce the load on the output port is to add a power amplification link, that is to say, an intermediate relay with a relatively small pull-in power and hold power. In addition, the design and selection should pay special attention to the output characteristics of these output modules.
2, pay attention to the output module of the external circuit protection. To prevent damage to the output port due to external circuit short-circuit and other reasons, can be set in its output short-circuit protection device.
3, interlocking, interlocking software and hardware settings. Purely in the PLC internal logic interlocking and interlocking, often in the circuit failure occurs when the loss of role. Such as the motor’s positive and negative contactor interlock and AC and DC contactor interlock, etc., only in the application program is not enough. Because the contactor tends to appear the main point of “burn” and the main circuit in the coil power is not broken after the break, then give the opposite if the control command will cause a serious short circuit in the main circuit. To solve this problem is to contact the two normally open auxiliary point into the PLC input port, and then in the software they are normally closed way string into the other output coil, you can play a more perfect protection. Coupled with the hardware on the interlock, the more perfect.
4, the PLC power supply requirements and system voltage protection. In the Gantry Crane loading and unloading site, power quality is generally poor, interference, fluctuations, low voltage operation and instantaneous high voltage often occurs, will have an impact on the operation of PLC devices. Although most of the PLC system has a strong ability to adapt to the power, but the use of high-quality power supply will undoubtedly increase the system’s reliability. In the application development to pay special attention to the system of voltage protection, to be considered everywhere the state of pressure when the initial state of the system recovery and interlock.
5, the use of certain anti-jamming measures.
6, to retain spare control means.