High accuracy lift-height sensor makes forklifts safer

Citation

(2005), "High accuracy lift-height sensor makes forklifts safer", Sensor Review, Vol. 25 No. 3. https://doi.org/10.1108/sr.2005.08725caf.003

High accuracy lift-height sensor makes forklifts safer

High accuracy lift-height sensor makes forklifts safer

Keywords: Packaging, Sensors

For manufacturing and warehousing companies, logistics is now a key business driver. Materials have to be shipped and transferred along supply chains at high speed in order to meet customer demand. As a result, manufacturers and logistics service providers are constantly looking for ways of reducing material transfer times and to optimise the flow of goods through the factory, warehouse and supply chain.

Some companies have now optimised their logistics and material flows using draw-wire displacement sensors on forklift trucks, for example. When raising and lowering loads by forklift truck, safety margins normally have to be adhered to, so that when rounding a corner, braking or accelerating for example, the truck is not placed in a dangerous, tilted position. If the lift height of the load can be measured accurately, the optimum “safe” driving speed can then be determined. Still- Wagner, a manufacturer of innovative forklift trucks based in Reutlingen, Germany, is utilising a special Micro- Epsilon draw-wire displacement sensor, to measure the lift height on its forklift trucks. The system, which uses a custom-designed Micro-Epsilon P600 series sensor, is completely failsafe so that truck operators cannot deliberately or accidentally cause critical driving conditions. The system optimises the speed of the truck and improves the safety by automatically bringing the load to the correct lift height, to speed up the movement of materials to the appropriate shelf height in the warehouse (Plate 3).

Plate 3 The Micro-Epsilon P600 is completely failsafe so that truck operators cannot deliberately or accidentally cause critical driving conditions

The P600 sensor is a special, custom designed draw-wire sensor. It has a much slimmer construction (width of 87mm) than the company's standard P60 draw-wire sensor so that it could be fitted into a very tight installation space on Still-Wagner's trucks (Plate 4).

Plate 4 Micro-Epsilon's standard P60 draw-wire sensor (above left) and the customised P600 draw-wire sensor used on Still-Wagner's forklift trucks (above right)

Safe operation guaranteed

Thomas Birchinger, Product Manager draw-wire sensors at Micro-Epsilon explained: “If the truck operator has to raise the forks 15m to reach the racking where the goods are stored, the temptation for the driver may then be to accelerate away quickly with the forks still high, which can be dangerous. Our P600 sensor simultaneously measures absolute precision using a potentiometer and an encoder reading. If there is a difference between the two output signals, the truck is then automatically placed in a safe mode”.

The P600 is designed to operate redundantly. Two electrically indepen- dent signals – a potentiometer output and an encoder output – ensure that a high level of safety is achieved. The high accuracy sensor has a potentiometer output that achieves a repetitive accuracy of < 0.05 per cent and a linearity of < ± 0.1 per cent. The encoder output has a resolution of < 0.05 per cent and a linearity of < ± 0.05 per cent. The operating temperature range for the P600 is from 0°C up to 50°C but there is also a special cold store version for temperatures down to - 20°C. The P600 also has a sensing range of up to 15,000mm, ten times further than the standard P60 sensor.