Sensor Fusion: Combination of draw wire sensor and inclinometer

Kubler 10/1/2017

Sensor FusionMobile cranes, reach stackers, telehandlers and similar mobile work machines generally use draw wire sensors to define the position of the telescopic boom. In addition, information about boom inclination is of crucial importance for safe vehicle operation. Kubler now combines these sensors in one single housing. This saves costs and installation space.

The reach stacker has the container firmly in its grasp. The wind is blowing sea spray over the docks. There is a smell of salt, a humid veil is covering everything. The boom of the reach stacker vibrates while the huge vehicle roars across the worn-out asphalt of the port area towards the container loading area. A vivid image of a standard process of harbor logistics - and a "nightmare" for the sensors mounted on the boom. They are directly exposed to the harsh environmental conditions - salt, humidity and vibrations.

And still, the technique must perform hardest work. Load monitoring must function perfectly. Tipping over must imperatively be prevented. This is principally the task of the position sensors, which measure the boom extension length and inclination. In order to optimize robustness, installation work and economic efficiency, Kubler implemented a simple and ingenious product idea: the combination of inclination angle and extension length measurement in one single device.

The new draw wire systems C100 and D125 of the Base-Line category are equipped with an integrated inclinometer and are moreover available as redundant sensors. They are predestined for vehicles with telescopic and erectable work equipment. The measuring range reaches up to 10 m. 
Standard sensors reach their limits

Various sensors are integrated in a mobile work machine to measure length, inclination and angle. Requirements are high. The sensors used until now have been developed mainly for the general mechanical engineering and are therefore not always sufficiently robust, compact and reliable.

This is where many sensors reach their limits, as they are exposed day after day to various environmental influences. In addition, they often require extensive installation work due to wiring, different connection types or inappropriate sensor size. Safety monitoring even requires, in spite of unfavorable space conditions, the installation of multiple and redundant sensors. In the event of a failure, troubleshooting can take hours.

Robust and space-saving integration

The newly developed draw wire systems C100 and D125 will from now on allow length and inclination measurement with one single device. Thanks to the compact design and the integrated inclinometer, these draw wire systems are particularly easy to integrate in any existing or new application.

Connection is very easy with a 5-pole M12 connector and a supply voltage of 5-30 V DC or 9-30 V DC. The plastic housing, the IP67 protection level and the wide temperature range of -40 to +85 °C ensure confident and long service life in outdoor applications. With a diameter of 0.9 mm, the ringfastened wire is particularly robust. This linear measuring system also operates with a wire pull-out angle of up to 10°. The C100 draw wire system is designed for a measuring length up to 5 m, the D125 up to 10 m. The linearity of respectively ± 0.1 % and ±0.5 % of the measuring range ensures sufficient accuracy. Maximum travel speed is 1 m/s.

Kubler offers a wide choice of sensor types for configuring the draw wire system, featuring the usual interfaces of this branch (analog, incremental, CANopen, relay output, switching output). The current safety concepts require the installation of redundant sensor solutions. This means an increase of the global costs, more installation work, and leads to installation space problems.

The new C100 and D125 draw wire systems are available as redundant measuring systems and offer for the whole length the advantages of a compact sensor. The draw wire systems are also available without integrated inclinometer and can therefore be used also for other applications. From monitoring the support position up to the vertical stroke of a fork lift. With these integrated sensors combination, Kubler offers the machine manufacturers a robust and space-saving system that meets the harsh requirements of mobile work machines.