Perfect positioning solutions with Data Matrix code

Innovative technologies ensure safety and a high performance level

Pepperl+Fuchs: Technical developments are frequently characterized by the need to compromise. The new PCV positioning system is one of the rare examples where it is futile to look for deficiencies and limitations. It is based on modern technologies such as Data Matrix code and industrial vision and combines practically all the positive features of previous positioning solutions. Extremely large travel ranges, curve and climb capability, high resolution and data integrity, even in harsh industrial environments are just a few of the numerous highlights.

The majority of measures of industrial automation have the objective of ensuring competitive processing and production. So that frequent failures with plant shutdowns or short maintenance intervals do not cancel out most of the savings, plant operators expect high reliability and a long service life from automation components as well as their actual functionality. It is well known in the everyday world of industry that we are not talking about fair weather conditions. Machines and plants are not just continually exposed to dirt and dust, but frequently they must be able to take rough treatment. The same goes for the different positioning systems available on the market.

Data Matrix code stores position information

The new PCV positioning system (Positioning Coded Vision) from Pepperl+Fuchs combines previously unachieved reliability with exceptional performance data. Firstly this is accounted for by the highly redundant Data Matrix code, and secondly by the special configuration and organization of the square codes on a code strip in two rows positioned over each other. While the code strip is mounted along the travel range of the transport unit to be positioned, the camera-based PCV reading head is located on the mobile plant component. It detects the codes, evaluates the position information and transmits the results to a control unit. The PCV system is the world’s first positioning system that uses the Data Matrix code to encode absolute position information. As Data Matrix code currently provides the most effective process for marking and identification, the positioning system can also score with its superior properties. In particular, this applies with regard to barcode solutions.

The Data Matrix positioning system offers considerable travel ranges of up to 10,000 meters with an optional resolution of ±0.1 mm, 1 mm or 10 mm and is therefore also suitable for the largest applications imaginable. This includes monorail conveyors with many branches and parallel sections, loading, crane and lifting units, material handling applications and lifts. Horizontal, vertical or combined operation is possible. As well as curves, the system handles inclines and declines with up to a 30% gradient. A feature is that for the first time in such a positioning system, there is evaluation of height information which allows both of the rows of codes of a conveyor positioned one above the other. Users can extend this principle of placing several code strips over each other in their applications in virtually any way. For control purposes, the PCV system supports up to 1,000 event markers that are attached to the code strip. When the reading head reaches one of the event markers, it actuates a corresponding switching command in real time. Therefore, control actions that must always be performed in the same location are realized without a PLC.

High data integrity by means of integrated error correction

The Data Matrix code was developed at the end of the 1980s for the reliable tracking of parts with clear worldwide markings in air space flight and because of its performance was soon adopted by the automotive industry. Its success continued and it is now recognized by everybody, e.g. on postal items. The advantage of the Data Matrix code compared to the barcode is its storage capacity, which is much greater for the same area. This is due to the two-dimensional pixel matrix, while as a one dimensional code, the barcode only stores data in one direction. The Data Matrix code is not only for encoding simple user-information such as ID numbers, but simultaneously offers plenty of reserve for any data and not least for error correction. While the barcode can only be verified by readings of check digits, due to its special data encryption with data redundancy, the Data Matrix code is in the position of reconstructing a code automatically if parts of it are damaged or covered. With the PCV, the ECC200 code (Error Checking and Correction algorithm) is also applied, which is currently the most secure readable Data Matrix variant. Limit patterns help find the Data Matrix codes quickly and provide a clear reference of the code lines and columns.

As there are two rows on top of each other with Data Matrix codes on the code strip of the positioning system, the reading head detects at least six codes simultaneously. For successful decoding, just one of the three codes in the x direction needs to be correctly readable. This not only provides the PCV system with a previously unknown tolerance for damage, soiling or cover of the code strip, but also further valuable system features.

Therefore the code strip can be interrupted in places by up to 20 mm, e.g. from power rail mountings of an overhead conveyor. Further, Pepperl+Fuchs developers could design the code strip smaller than ever before due to the high information density. It can also easily be attached to the narrowest of mounting sites and allows curve radii of up to 0.1 m.

Evaluation of the ISO 15415 quality parameter

As Data Matrix codes can also become soiled and damaged over time or e.g. provide insufficient contrast due to empty cartridges, there is a clever early warning system. The PCV reading head continuously evaluates the eight quality parameters defined in ISO/IEC 15415. If required, the system informs the user about such quality defects via the protocol and a timely switching output before an actual failure.

The Data Matrix positioning system supports travel speeds of up to 12 m/s. All system components such as camera, LED illumination and microprocessor evaluation are contained in the PCV reading head. In addition, no separate bus connection is required as an RS485 interface is also integrated. The absence of laser diodes and mechanical parts makes the system robust and durable. During commissioning, an alignment aid eases adjustment of the reading head. With a depth of field of ±15 mm, the read distance is 80 mm. The code strips are available in 100 meter rolls, are self-adhesive, manufactured from silicone-free laminated polyester film and are resistant to chemical influences. As well as parameterization of the system via convenient PC software, there is the possibility of configuration via code cards which are simply held in front of the camera. The required code cards can be copied from the operating manual or simply printed out so that service personnel can keep them on their person at all times, without the need for a laptop.

Other important application areas include the commercial vehicle, special vehicle, marine engineering and port systems technology sectors. Various load and slewing cranes, lifting and working platforms, loading units, rotary fire service ladders etc. form the backbone of operational logistics processes as well as other activities. The plants are permanently exposed to moisture, dirt, dust, oil and grease and failures cost the operating company a great deal of money.

Summary: A quantum leap for positioning systems

With the PCV system, Pepperl+Fuchs has brought an innovative positioning system to the market that previous solutions will have to be measured against. High redundancy and data integrity of the Data Matrix Code coupled with the latest camera technology and intelligent evaluation algorithms provides system integrators and users with the current optimum in performance and flexibility. Thanks to its superior properties, it can be accommodated in numerous fields of application in material handling, transport, lifting and loading units, etc.