Function block instantiation - field bus control system The function block model

in a wide range of field bus technology, developed by fieldbus foundation of foundation fieldbus in the field of engineering automation received widespread support. Foundation fieldbus is a kind of is completely distributed automation system, main function is to the industrial production process measurement, signal transmitting, control, etc. FF H1 low-speed bus standard issued in 1996. With the mature of Ethernet technology, FF made FFHSE specification, the specification defines a kind of based on high speed Ethernet fieldbus technology. To realize the control function of the automatic control system, on H1 and HSE application layer increases the user layer. User layer includes the standardization of FF are defined and the function block application process, function block constitutes the automation control system in the main part of the control function.

function block model

in the FF fieldbus system, industrial control system of function block application process definition in user layer, including resources, function blocks and transformation, as well as to meet the needs of the control system and the increasing number of various objects, such as link object, trends, etc.

in the architecture field equipment application process, resources of network hardware and software objects, contains some hardware and physical properties in the field devices. The resource block defines the corresponding parameters used to describe the state of the resources, and by implementing a specific algorithm to control to the operation of the equipment resources. In the applications of user layer, function block FB represents the application performs the basic function of the automatic control, industrial control system is to define the major means of monitoring and control functions. By defining a function block, make the automatic control function of the industrial control system independent of the input/output (as much as possible IO) Equipment. Function block based on the specified algorithm and combined with its embedded parameters to deal with input parameters, the output provided to other function block or transform to perform control functions.

define transform block is designed to make function block and IO device isolated, these IO devices include sensors, actuators, and switch. Transform block controlled by independent interface for use by the function block access to the IO device, at the same time, the transform block also perform calibration and linear functions. Link object provides the corresponding relation between input and output, function block as the exchange of information mapping in the control system. At the scene of the FF fieldbus control system, the equipment or equipment of the exchange process of internal data and events are defined through the connection object.

function block instantiation

in the process of establishing control system, the field device control applications need is uncertain. Even build a good control system, also may be because the needs of the functionality or performance to add a new device, which requires the equipment such as IO equipment can provide perfect function. But the field devices are usually embedded devices, its operating system USES embedded operating system. So the field devices with limited resources available, and at the same time realize all functions of field devices to demand too much. For the IO device, multi-channel analog input ( MAI) Function block is responsible for the analog data acquisition, multiple discrete input ( MDI) The function block is responsible for the digital data acquisition, each MAI or MDI function block can collect data node is certain. In general, each function block types and the number of field devices in the custom before they leave. If the size of the control system has changed, the original installation field device can meet the needs of the control system. And if allowed to control engineers can according to the actual need to increase the type and number of function block in the field devices, can greatly reduce the complexity of the control system, to save the time and cost control system upgrade need, thus improve the production efficiency and benefits.

function block instantiation mechanism

to achieve the instantiation of the function block and other objects, in the foundation fieldbus user layer specification defines the object of the Action. Through the study of the operation of objects, can be in control system requires an object or a function block, in the field devices needed to create the object or function block. Can delete existing in the field device object or function block. Object contains three parameters, in the form of a structure is defined as:

among them, the first parameter to indicate action taken, value of 0, 1 or 2, 0 means no any operation, 1 is instantiated by parameter specifies the function block or object, 2 said request removal by parameter specifies the function block or object. The second parameter said instantiated, or delete operation when the object of action, the parameter values are device description file ( DD) In view of the specific function block or objects defined by the value. The third parameter is equal to 0 or 1, its value must be zero, when performing delete operation is equal to 2, the value of the parameter object is to delete the function block or serial number, is said to be deleted which one by a specified function block or object. Instantiation of operation through the configuration software implementation, users choose to instantiate the function block, configuration software to the specified field devices FMS write requests. Field device receives the FMS written request, first of all determine whether the equipment in the have defined the instantiation specifies the type of function block in the operation of the request. If this equipment is defined in this type of function block, is performed to instantiate operation, dynamic to apply for a piece of memory, the size of the memory that is instantiated request operation specified in the type of function block size. Then the template copy to a new application for the type of function block of memory.