Sick: safety scanner system for outdoor applications

Sick: safety scanner system for outdoor applications. The world’s first certified safety laser scanner system for outdoor use, the OS2000, is available for wherever a scanner solution is the best alternative for protecting outdoor areas. It is suitable for both stationary and mobile personal protection and collision prevention tasks, and meets highly demanding sensor- and safety-oriented requirements – as demonstrated by the example of protecting an outdoor AGV.

The OS2000 combines the proven hardware and software of an LMS Laser Measurement System, specially designed for outdoor applications, with the safety level of the UE4470 safe programmable logic controller, which is certified as a safety component within the sense of the Machine Directive. Typical examples of use of the system solution, which received approval from TÜV Rheinland in late 2007, include door and gate protection, cranes, manned and unmanned vehicles, waterway structures such as bascule bridges or locks, and rail or conveyor systems.

Former Limits of Use for Outdoor Applications

The EN 61496 standard is the basis for developing optical safety sensors. Section 3 makes special reference to scanning systems like the safety laser scanner and clearly defines, for instance, the requirements regarding the reliability of detection capability, or availability (taking into account operating conditions).

However, particular properties of decisive importance for certification have hitherto restricted the use of scanning systems in outdoor areas. These include, in particular, high light sensitivity outdoors and the resultant range restriction, lack of all-weather capability (i.e. low availability in poor weather), and the limited operating temperature range.

The advantages that the laser scanner offers – e.g. barrierfree protection, flexibility of protective field layouts, monitoring functions, as well as simple integration in plant controllers and fieldbus systems – have in the past led to solutions using systems that are not certified.

The disadvantage: each plant must be inspected by the responsible authorities with the aim of obtaining a single-plant permit for use – a time-consuming and costly process for both the producer and the plant user. This is why the calls for scanning systems with EU Type Examination approval for outdoor protection have become increasingly loud.

The OS2000 Eliminates the Former Restrictions on Use

Sick has developed the world’s first safety laser scanner system approved for outdoor use – the OS2000. Laser Measurement Systems of the LMS series, which are designed with a variety of features for outdoor use and have already been proven in several thousand applications (e.g. as a collision-prevention system for container cranes and vehicles, or as building security sensors) form the technological sensor basis.

Thus IP67-protected laser scanners with a scanning angle of 100° or 180°, depending on the task, are available for use at temperatures of between –30 °C and +50 °C. Thanks to powerful specific software algorithms, they are unaffected by reflections from snow or rain, dampness (fog), or strong light incidence. Protective fields can be parameterised and evaluated as desired.

A safety-oriented scanner range of 20 m has been defined for the OS2000. Improved detection properties and greater availability in outdoor use are, however, just some of the demands that a solution must meet to pass the EU Type Examination. There are also special requirements regarding internal monitoring and self-testing of the scanner solution. Thus, in addition to optical testing of detection capability, there must also be a monitoring of the non-redundant output signals within the sensor to controller operating chain.

Flexible Safety Controller Handles Safety-oriented Evaluation, Testing and Connection

The flexible UE4470 safety controller with integrated external device monitoring and parameterisable restart interlock gives the OS2000 system the necessary safety level. The controller, certified in Safety Category 4 (EN 954-1) and SIL 3 (IEC 61508), handles the machineside connection, evaluation of the output signals of up to 3 LMS units, control of cyclical sensor testing on the basis of fixed test targets, and the safety-oriented mastering of faults – a process for which a patent has been applied.

The OS2000 safety laser scanner system thus meets the demands of Performance Level d according to ISO 13849-1 and SIL 2 in compliance with EN 62061. This was confirmed by TÜV Rheinland in late 2007 with its approval for stationary and mobile use and ranges of up to 20 m.

The UE4470 also handles the actual protective field evaluation and the automatic monitoring of cables for short-circuits, cross-circuits, short-circuits to ground or voltage problems. In addition, the UE4470 can take on safety functions such as emergency stop or the monitoring of door contacts, and process the signals of the automation system of a machine or vehicle.

Safe integration in a fieldbus system is also possible.

Example of Use: Protection of an XXL AGV Outdoors

One of the first applications for this solution concept, now approved as the OS2000, was the protection of a free-driving AGV for concrete stones. This is an “XXL” vehicle with rotating, bearing-mounted drive stilts. It can move in any direction at a maximum speed of 1.2 m/s, and obtains its positional data via GPS.

Due to the AGV’s design, there are hazards that require protection both internally, between the stilts, and around the vehicle. The need to evaluate numerous protective systems meant that barrier free area protection using laser scanners was the best operational option. Consequently, the outdoororiented LMS221-S23 with a scanning angle of 180° is used in the OS2000 version here. Four devices form a virtual protective field frame around the vehicle that detects obstacles or persons without contact, and triggers a vehicle stop on detection.

A further laser scanner monitors the internal load-up-take area in order to safely detect persons here, too. The UE4470, as the controller of the OS2000 system, also handles communication with the AGV automation system: on the basis of the current GPS position, individual protective fields are switched off (muting function) when the AGV approaches the conveyor system or set-down spaces in the warehouse.

The GPS position is employed as a muting command via a Profibus gateway to the UE4470, and compared there with the expected position detected by the OS2000. The muting process is only triggered if the GPS position matches the safety-oriented actual position detected. The UE4470 also triggers an emergency stop if the AGV reaches the transfer station on the deal belt too late.

The non-safety-oriented components – GPS, navigation computer, automation system and Profibus gateway – are thus also included in the monitoring of safety functions.

Positive Operating Experience

Whether mobile or stationary, there are a range of outdoor applications in which a scanner solution is the best protective alternative. A certified scanner system for outdoor personal protection, allowing flexible adaptation of monitoring and control functions to cope with a wide variety of conditions is now available in the form of the OS2000.

Thus the OS2000 is “knocking at several open doors” to external areas.

Harald Schmidt
Walter Schneider

Contact:

Sick GmbH,
Düsseldorf, Germany
Tel.: +49 211 5301 0
Fax: +49 211 5301 100
info@sick.de
www.sick.de