RFID technology

Radio frequency identification (RFID) was used for the first time in the 80s in applications for tracing and access control systems. These wireless AIDC systems allow contactless reading and are successful in manufacturing and in harsh environments where bar code labels could not last. Due to its capability to track moving objects, RFID has established itself in various markets, including automated vehicle identification (AVI) systems.

RFID is the abbreviation for "radio frequency identification" and means contactless radio transmission of data. RFID technology offers the possibility of reading and writing data – contactless and without line-of-sight – on RFID tags, transponders, SMART labels.

Nowadays, radio frequency identification technology is used in a growing number of fields and industries. However, the technology has existed for more than 20 years. RFID is considered to be a sensible complement to bar code technology. While it has for a long time been used predominantly in closed applications (immobilizers in private cars, security systems, etc.), a standard that is applicable

worldwide now allows industry-independent use of RFID along the entire value added chain. When integrating RFID systems, communication with higher-level EDP systems (ERP, production planning, merchandise management or warehouse management systems) plays an important role.

RFID systems consist of a transponder and a writer/reader. The transponder is the data storage.

Figure 3-6: Basic configuration of an RFID system

Radio waves are the transmission medium for an RFID system. Since data exchange is bidirectional, transponder and write/read device are set up symmetrically to one another. Both components feature a chip for processing the radio signals and an antenna. The transponders usually have no separate power supply and are supplied via the field generated by the write/read device.

Data and power transmission can be inductive, capacitive or electromagnetic. Among other things, the transmission mode depends on the carrier frequency that also determines the system range. While capacitor plates (e.g., for chip cards) are used as antennas for capacitive transmission mode and coils for inductive transmission, dipoles are used in the UHF range.

Small micro-chips are integrated in write/read devices and transponders that encode/decode the data to be exchanged and modulate or demodulate it to the carrier frequency for wireless transmission. Multitag operation is based on different multiplex methods. The write/read device has an interface connection via which it can be connected to a computer, a PLC or a network.

Comparison of DMC and RFID

Whether Data Matrix codes (DMC) or radio frequency identification (RFID):

The high data security of both marking or identification systems is convincing, they have proven themselves in multiple applications even in harsh industrial environments and meet the increasing requirement for full traceability of products and processes. At the same time, they save time and work compared with manual marking and detection technologies.

Main criteria for selecting DMC or RFID:

Can the data medium be reused or is it lost at the end of the machining

sequence?

Single or repeated marking/writing properties within the machining sequence ?

Detection distance

Lighting conditions

Sources of interference (ambient temperatures, dirt, etc.)

Table 3-1: Comparison of DMC and RFID

 

Data Matrix code

Like the bar code, the Data Matrix code is an optical code recognition method and its structure makes it particularly suitable for quick, reliable and unique sensing. Unlike the bar code (1D code), the Data Matrix code is two-dimensional. This significantly increases the information density. In addition, the Data Matrix code can be scanned from all angles and – due to redundant data – still be read when individual areas have been damaged.

The Data Matrix code can have a size of 10 x 10 to 144 x 144 fields, but it can also be printed in non-square forms. An uninterrupted frame from top left to bottom right acting as a search element and informing the reader on the three-dimensional position surrounds half the Data Matrix code. The other two sides are surrounded by an alternating black and white pattern that serves as a "clock pulse" and makes the code size quickly denumerable. With its maximum size, this matrix code can transport 1558 extended ASCII characters (eight bits), 2335 ASCII characters (seven bits) or 3116 digits.

The Data Matrix code, initially used in the electrical industry for printed-circuit board marking and in chip manufacturing and also successful in the automotive industry, has meanwhile also become generally known as digital stamp.

Bar codes

When reading a bar code, it is required that the optical representation in the form of light and dark bars differing in width be captured, digitized, recognized by a device and provided on an interface in a machine-understandable data stream. This is performed by the bar-code reader.

One-dimensional bar code

The start code follows after a quiet zone, which usually has a length of 10 module widths. Then come the net characters, i.e. the bar code symbols containing the encoded information. In most cases, a bar code character including the information of a check digit is located behind the net characters. After a stop code, the bar code ends with another quiet zone. The quiet zone supports correct code recognition. Without quiet zones, areas and characters surrounding the bar code could be misinterpreted by the bar code reader. The narrowest occurring bar of a bar code has a width that is referred to as module width. All bars of this width can be named as modules. A module width of 0.25 to 0.6 millimeters can be found frequently in practical operation. In many cases, start and stop code consist of different bar code characters. If they consist of the same character, this character is mostly asymmetric. Due to this, the reader can detect the three-dimensional position of the bar code immediately when capturing the symbology and, if necessary, evaluate the read information rotated by 180 degrees. Different bar

codes meeting most different criteria exist and these criteria can be used to classify them into bar code families. Before deciding in favor of a specific bar code, a printing technology, a location where it is to be applied and a code size, the purpose of the symbology has to be clarified.

What is automatic identification ?

System classification

The possibility of automatically identifying articles and objects to manage, test and control sequences in production and logistics is an essential part of automatic systems. 

In many fields, correct identification of articles in the shortest time, for which automatic identification forms the basis, is a basic requirement for efficient process design. 

The term "automatic identification" summarizes technologies for identification , data capture and data transmission. It includes systems such as :

• Bar code.
• magnetic ink character code (smart label).
• RFID (radio frequency identification).
• OCR (optical character recognition)
• Voice recognition.
• Chip card applications.
• Biometrics.

The figure below provides an overview of all automation identification technologies:

Two-dimensional bar code (Data Matrix code) and RFID technology are the main points of this application. 

The aim of the following sections is to give an understanding of both systems and to show the advantages and possible applications of the two technologies.

Automatic Identification with SIMATIC RF620R and SIMATIC MV440/MV420 Code Reader

Problem
On a production line in the automotive industry, an industrial robot is to mount camshafts into cylinder heads. For quality assurance, a cylinder head coding is to be compared with a camshaft coding. The code of the cylinder head is stored in a rewritable RFID tag, whereas a dot matrix code that is captured optically is printed on the camshaft.


Solution
What makes this solution special is that it is largely independent of the used code detection. The FB45 standard block is used for both RFID and optical code recognition.

Micro Automation: Wireless Tracking with GPS based on GPRS - MAS 41

Automation task:Control of a mobile concrete mixing pump (remote station) shall now be supplemented by a position detection which enables buffering the determined coordinates locally and to make them accessible to a central station via GPRS communication.
A service station connected with the central station via the INTERNET shall have access to these tracking data and display the current position in form of a map.
The coordinates (longitude and altitude) of the concrete mixing pump shall be determined using a GPS receiver.
For the local operation of the concrete mixing pump a text display shall be used which can also represent instructions of the control center.

Automation solution

The automation solution uses the SINAUT Micro SC remote control system with the GPRS modem MD720-3 to visualize process data from the Remote Station via the Central Station.

On Central Station the web server "miniWeb", integrated in WinCC flexible, enables the access from a Service Station using the INTERNET. The web server provides a HTML-page, where the position of Remote Station is displayed on a map from "Google Maps". Other process values can be watched and operated.

Remote Station „concrete mixing pump“
Via a GPS receiver the S7-200 CPU 224XP receives the current position of the concrete mixing pump. The CPU controls and monitors the process values of the concrete mixing pump on demand. The TD 400C text display enables representing the process values and operating the concrete mixer value. Using a 256 KByte memory module the position data are buffered non-volatile. Transmission of the current position or the buffered positions and all process data to the central station occurs using the GPRS modem MD720‑3.

Central Station
The SINAUT MICRO SC is used as a platform for data exchange with the remote station. The internet connection enables receiving the process data from, or send them to the remote station in the course of a GSM/GPRS communication. Parallel to the communication platform SINAUT MICRO SC makes the received process data available as OPC server of a visualization. The visualization in form of WinCC flexible RT enables the access to the process value as OPC client. In this set WinCC flexible works as web server and makes these process values available to web applications.

Service Station
The Microsoft Internet Explorer shall make the process data of the data of all remote stations available in the central station representable and changeable via a HTML page. The MWSL-Script embedded in these HTML pages realizes the access to the WinCC flexible variables. The current position consisting of longitude and altitude is displayed in a map via a Java applet in Google Maps.

Startup Code:For the startup we offer you software examples with test code and test parameters as download. The software examples support you during the first steps and tests with your Micro Automation Sets. They enable quick testing of the hardware and software interfaces between the products described in the Micro Automation Sets.

Standard Chilled Water System Start/Stop Control Sequence Test

Control Sequence Description:
During the "occupied" period, 100% outside air economizer control is used for cooling when the outside air (OA) temperature is less than return air temperature and 72°F. If supply air temperature cannot be maintained with 100% OA the cooling coil is operated simultaneously to maintain set point. The chiller, acting as a second stage to the economizer, is controlled (programmed on/off) as required to maintain the AHU-1 supply air temperature set point (as reset by the greatest VAV cooling demand). The chilled water system is commanded "on" at a supply air temperature set point 1½°F below the OA temperature for 10 minutes and "off" at a set point 1½°F above the OA temperature or an OA temperature of 60°F or less (adjustable) for 10 minutes. If the lead chilled water pump does not start the lag pump is commanded "on". Chiller controls are adjusted to provide 45°F chilled water supply temperature to the HVAC system.

Prerequisites for Initiating Test:

All equipment has been fully checked out and determined operational. No equipment is unduly locked out and no one is working on or might work on the equipment during test. All necessary schedules have been programmed. All necessary monitoring or trend points are available and sufficient memory and data archival capability is available to complete test.

Test Procedure Instructions:

Basic Instructions / Test Conditions - Perform the following tests by monitoring and /or observing each piece of controlled equipment under actual operation. It is permissible to adjust the programmed schedules and/or setpoints for easier testing. If this is done, reprogram to the original schedules and setpoints, or as directed by the building operator, at the conclusion of testing. If the original values are not consistent with energy efficient operation, discuss with the building operator. Perform test on mild to warm day if possible. (1) Observe or adjust conditions such that 100% outside air is being used to cool the building and the chilled water pump is off. Observe or adjust outside air temperature to 2°F above supply air temperature setpoint. Determine if and when chilled water system turns on. Observe chilled water supply temperature. (2) Observe or adjust conditions such that chilled water system is on. Observe or adjust outside air temperature to 2°F below supply air temperature setpoint. Determine if and when chilled water system turns off. (3) Observe or adjust conditions such that chilled water system is on. Observe or adjust outside air temperature to 59°F. Determine if and when chilled water system turns off. (4) Observe or adjust schedule to determine if chilled water system is off during "unoccupied" period.
Measurement Method(s) – Use dataloggers or DDCS input channel trend logs to monitor outside, supply and return air temperatures, chilled water supply temperature, chilled water pump kW (or flow switch status), chiller kW, outside air damper position and cooling supply air (SA) temperature setpoint. Record data at 1-minute intervals. The measurement system employed must be able to record temperature within ± 0.1° F.
Data Analysis - For each test, select a typical condition from the observed data and input the appropriate response in the data form. If trends are used, record the trend file name and ID number, data source file names and storage locations in the data form.
Results to be Obtained / Criteria for Acceptance - Chilled water pump should remain off until supply air temperature setpoint drops 1½°F +1½ or -½°F below outside ambient temperature for 15 ±5 minutes during occupancy. The chiller and then the chilled water pump should shut down when the supply air temperature set point rises 1½°F +1½ or -½°F above the OA temperature or an OA temperature of 60°F ±2°F or less for 15 ±5 minutes during occupancy. Chilled water supply temperature to the HVAC system should be 45°F ±2°F. If any equipment runs during an unoccupied period it is a deficiency.
Reporting - Attach to the data form with appropriate labels all relevant field data, plots and trend logs that validate the results. Annotate any data so that it is clear what it is proving. DDCS trend logs of DDC output signals are not acceptable as proof of operation unless you have first verified and documented (attach) that the output signals accurately represent actual operation. Annotate any logger data and graphs so that it is clear what the data are proving, and attach these to this form.

To ensure that this Commissioning Procedure will not damage any equipment or affect any equipment warranties, have the equipment manufacturer's representative review all test procedures prior to execution. Make all necessary parties aware of the test and that the equipment should not be disturbed.

    

Name and affiliation of party conducting test:
Start & stop time and date of test:
Conditions during test: ____________________________________________________________________________ ________________________________________________________________________________________________
Related Equipment # or ID:	AHU-1	ChWP 1/.2	Chiller 1
Method of Test	Test Data				OK?	Comment #
(1) Observe or adjust conditions such that 100% outside air is being used to cool the building and the chilled water pump is off. Observe or adjust outside air temperature to 2°F above supply air temperature setpoint. Determine if and when chilled water system turns on. Observe chilled water supply temperature.	Time: ChWP Status: OAT: SAT Setpoint: Minutes until chiller on: Ent / Lvg CHW temp: /
(2) Observe or adjust conditions such that chilled water system is on. Observe or adjust outside air temperature to 2°F below supply air temperature setpoint. Determine if and when chilled water system turns off.	Time: ChWP Status: OAT: SAT Setpoint: Minutes until chiller off: Minutes until ChWP off:
(3) Observe or adjust conditions such that chilled water system is on. Observe or adjust outside air temperature to 59°F. Determine if and when chilled water system turns off.	Time: ChWP Status: OAT: SAT Setpoint: Minutes until chiller off: Minutes until ChWP off:
(4) Observe or adjust schedule to determine if is off during "unoccupied" period.	Time: Schedule: Unoccupied ChWP Status:
Data file name(s):
Data file storage location:
Plot name(s):
Observations, notes, deficiencies, and recommendations: #     Comment (attach additional sheets as required) __ ____________________________________________________________________________________________ __ ____________________________________________________________________________________________ __ ____________________________________________________________________________________________
Recommend Acceptance: Yes □ No □ Signature: Date:
Attach to this form with labels all relevant field data, plots and trend logs that validate the results. Annotate any data so that it is clear what it is proving.