On safe paths


When using the principle of triangulation for navigating automated guided vehicles (AGVs), vehicles are often equipped with two different scanners, one for safety and one for navigation. Now there is a more cost effective alternative, the new Leuze RSL 400 safety laser scanner.

This safety laser scanner not only ensures that AGVs are operated safely by means of protective and warning fields, but also simultaneously captures the measurement values for the navigation software. This means that only one scanner is needed for both safety and navigation.

The measurement value output of the device is optimised for navigation software which functions in according with SLAM (Simultaneous Localisation and Mapping). These characteristics allow the Leuze RSL 400 to precisely determine the position of the AGV.

The navigation software contains an image of the operating area including all fixed boundaries. The current position of the AGV is calculated by comparing the measurement values to this map. This concept is referred to as natural navigation.

Precise navigation

With each revolution of its deflection unit, lasting 40 milliseconds, the safety laser scanner emits 2 700 light pulses. These are scattered in all directions, and parts of the scattered light are transmitted back to the scanner. These are used to calculate the distance to an obstacle.

The more detailed and exact the measurement values of the scanner, the more precisely the AGV can navigate. With an angular resolution of 0.1, the Leuze RSL 400 can capture the environment in detail over the entire measurement range up to 50 metres.

This is achieved through a particularly narrow laser spot that maintains its perpendicular shape over the entire scanning angle. It also reduces incorrect measurements, the likes of which can occur on edges.

In addition to the angular resolution, distance values are also important. The Leuze RSL 400 offers an error accuracy of less than 30 mm resulting in high precision. Use of technology in the device has ensured that the values are not affected by the reflectance of the object, whether it is a reflector or a black wall.

The additional output of the received signal strength value for each beam allows autonomous detection of reflectors by the navigation software. When beams strike a reflector, the values differ greatly from any other environment. This makes simple and reliable detection possible.

Safety is also optimised with the Leuze RSL 400 scanner. The device offers up to 100 switchable protective and warning field pairs. The protective fields can be adapted to the respective movement and load conditions of the AGVs.

Seeing around corners

For example, in 4-field mode with 50 switchable field sets, the Leuze RSL 400 device can monitor up to four protective fields simultaneously. This enables safe and reliable reduction of the speed of the AGV. With its scanning angle of 270°, the device can also cover the front and side areas of AGV at the same time, i.e. it can see around the corner.

With these features and a maximum operating range of 8.25 metres, even large AGVs can be fully safeguarded used only two Leuze RSL 400 scanners.

Countapulse Controls
Clive Robinson
Tel: (011) 615-7556
Email: clive@countapulse.co.za