Type Programmable Automation Controller
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Programmable Automation Controller (PAC) Programmable automation controller (PAC) systems consist of PAC modules, each of which performs a specific function. PAC systems are used in motion control, machine control, machine vision, and other industrial control applications. They include the following types of PAC modules: analog I/O modules, digital I/O modules, relay modules, counter modules, serial modules, servo or stepper controller modules, timer modules, and data acquisition modules. PAC systems with analog I/O modules are used to measure and control industrial automation devices such sensors and actuators. They can also be used to condition high or low voltage signals, thermocouples, resistance temperature detectors (RTD) and strain gauges. PAC systems with digital I/O modules are used to measure and control industrial automation devices such sensors and actuators. PAC systems with data acquisition modules digitize and process multiple sensor or signal inputs for monitoring, analysing and/or controlling systems and processes. PAC systems with serial modules coordinate the flow of data, control signals, and timing information between data terminal equipment (DTE) and data communication equipment (DCE). Programmable automation controller (PAC) systems have backplane slots for adding input/output (I/O) modules and differ by backplane bus type. The VersaModule Eurocard bus (VMEbus) is a popular, 32-bit bus used in industrial, commercial and military applications. VME extensions for instrumentation (VXI) is an electrical and mechanical standard used with automatic test equipment (ATE). Peripheral component interconnect (PCI) is a local bus system designed for high-end computer systems. Compact PCI (cPCI) uses the
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Controlling movement[edit]For a given robot the only parameters necessary to completely locate the end effector (gripper, welding torch, etc.) of the robot are the angles of each of the joints or displacements of the linear axes (or combinations of the two for robot formats such as SCARA). However there are many different ways to define the points. The most common and most convenient way of defining a point is to specify a Cartesian coordinate for it, i.e. the position of the 'end effector' in mm in the X, Y and Z directions relative to the robot's origin. In addition, depending on the types of joints a particular robot may have, the orientation of the end effector in yaw, pitch, and roll and the location of the tool point relative to the robot's faceplate must also be specified. For a jointed arm these coordinates must be converted to joint angles by the robot controller and such conversions are known as Cartesian Transformations which may need to be performed iteratively or recursively for a multiple axis robot. The mathematics of the relationship between joint angles and actual spatial coordinates is called kinematics. See robot controlPositioning by Cartesian coordinates may be done by entering the coordinates into the system or by using a teach pendant which moves the robot in X-Y-Z directions. It is much easier for a human operator to visualize motions up/down, left/right, etc. than to move each joint one at a time. When the desired position is reached it is then defined in some way particular to the robot software in use, e.g. P1 - P5 below.
Transcript of Type Programmable Automation Controller
Programmable Automation Controller (PAC)
Programmable automation controller (PAC) systems consist of PAC modules, each of which performs a specific function. PAC systems are used in motion control, machine control, machine vision, and other industrial control applications. They include the following types of PAC modules: analog I/O modules, digital I/O modules, relay modules, counter modules, serial modules, servo or stepper controller modules, timer modules, and data acquisition modules. PAC systems with analog I/O modules are used to measure and control industrial automation devices such sensors and actuators. They can also be used to condition high or low voltage signals, thermocouples, resistance temperature detectors (RTD) and strain gauges. PAC systems with digital I/O modules are used to measure and control industrial automation devices such sensors and actuators. PAC systems with data acquisition modules digitize and process multiple sensor or signal inputs for monitoring, analysing and/or controlling systems and processes. PAC systems with serial modules coordinate the flow of data, control signals, and timing information between data terminal equipment (DTE) and data communication equipment (DCE).
Programmable automation controller (PAC) systems have backplane slots for adding input/output (I/O) modules and differ by backplane bus type. The VersaModule Eurocard bus (VMEbus) is a popular, 32-bit bus used in industrial, commercial and military applications. VME extensions for instrumentation (VXI) is an electrical and mechanical standard used with automatic test equipment (ATE). Peripheral component interconnect (PCI) is a local bus system designed for high-end computer systems. Compact PCI (cPCI) uses the electrical standards of the PCI bus, but is packaged in a Eurocard. PCI extensions for instrumentation (PXI) is a superset of CompactPCI that adds timing and triggering functions. In terms of ports and interfaces, some programmable automation controller (PAC) systems have an Ethernet, universal serial bus (USB), or video graphics array (VGA) port. Others have a keyboard, mouse, or printer port. Serial PAC systems have RS232, RS422 or RS485 ports. IEEE 1394 or FireWire® (Apple Computer, Inc.) ports are also available.
Communication Standards and Network Protocols
Programmable automation controller (PAC) systems use popular communication standards and network protocols. Ethernet is a local area network (LAN) protocol that supports data transfer rates of 10 Mbps. Transmission control protocol/Internet protocol (TCP/IP) is the basis for standard Internet protocols. Controller area network bus (CANbus) is a high-speed, serial data network designed for harsh electrical environments and real-time control applications. DeviceNet uses the CAN network protocol to connect industrial devices to PAC modules. The process fieldbus or PROFIBUS® (Profibus International) is an open-communication standard used in factory automation, process automation, motion control, and safety applications. The MODBUS® (Modbus-IDA) protocol is an open-standard, vendor-neutral messaging structure for communication between intelligent devices. OPC defines a set of standard interfaces based upon OLE/COM technology and can be re-used by human machine interface (HMI) and supervisory control and data acquisition (SCADA) applications. Java® (Sun Microsystems, Inc.) database connectivity (JDBC) allows PAC modules to access to external structured query language (SQL) databases.
Selection
Selecting programmable automation controller (PAC) systems requires an analysis of regulatory requirements and special features. PAC systems for international markets should comply with Restriction of Hazardous Substances (RoHS), a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of hazardous substances such as lead and mercury. The EU’s Waste Electrical and Electronics Equipment Regulations (WEEE Regulations) are designed to encourage the reuse, recycling and recovery of electrical and electronic equipment such as PAC systems.
Features
Features for programmable automation controller (PAC) systems include surge protection, visual indicators, watchdog timers, and real-clock timers. PAC systems with a reset button, integral power supply, and built-in web server are also available. Hot-swappable PAC systems allow the installation and removal of modules during operation.
Fixed Automation
Fixed automation is a system in which the sequence of processing (or assembly) operations is fixed by the equipment configuration. Each of the operations in the sequence is usually simple, involving perhaps a plain linear or rotational motion or an uncomplicated combination of the two; for example, the feeding of a rotating spindle. It is the integration and coordination of many such operations into one piece of equipment that makes the system complex. Typical features of fixed automation are:
• High initial investment for custom-engineered equipment
• High production rates
• Relatively inflexible in accommodating product variety
Advantages:
Low unit cost Automated material handling High production rate.
Disadvantages:
High initial Investment Relatively inflexible in accommodating product changes.
Flexible Automation
Flexible automation is an extension of programmable automation. A flexible automated system is capable of producing a variety of parts (or products) with virtually no time lost for changeovers from one part style to the next. There is no lost production time while reprogramming the system and altering the physical setup (tooting, fixtures, machine settings). Consequently, the system can produce various combinations and schedules of parts or products instead of requiring that they be made in batches. What makes flexible automation possible is that the differences between parts processed by the system arc not significant. It is a case of soft variety. So that the amount of changeover required between styles is minimal. The features of flexible automation can be summarized as follows:
• High investment for a custom-engineered system
• Continuous production of variable mixtures of products
• Medium production rate
• Flexibility to deal with product design variations
Advantages:
Continuous production of variable mixtures of product. Flexible to deal with product design variation.
Disadvantages:
Medium production rate High investment. High ‘unit cost relative to fixed automation
