Linear encoders for future-proof position measurement in hydraulic cylinders

There is an increase in the demand for linear sensors for mobile automation in general and, even more so, for hydraulically driven machines. But the quantitative aspect is just one side of the story. This, according to Alexander Hurt, Head of Linear Encoders Business Unit, SICK AG, Germany.

More and more vehicle manufacturers, integrators, and operations managers are setting their sights on top-quality innovations. Everyone wants the added value that came to be standard within industrial automation long ago: the encoder needs to gather status and process information.

In future, precise, high-performance position measurement is set to come with the added option of performing detailed analyses on the basis of sensor information. This will make it possible, for example, to provide support for assistance systems, avoid sudden machines failures, optimise maintenance routines, and improve machine availability on the whole. Within the field of hydraulic measurement technology for mobile automation, the linear encoders in SICK’s MAX product family are currently the only devices of their kind to offer this added value. They operate in line with the robust operating principle of magnetostriction, provide extensive diagnostic functions (the first sensors of their kind), and offer added value for mobile machines that will continue to be relevant as we head into the future.

Innovation with magnetostriction

One key feature of the new SICK linear encoders is their full mechanical compatibility with existing cylinder constructions that are already prepared for integration into a path measurement system. Integration into hydraulic cylinders is therefore guaranteed to be a quick and easy process.

Inside these linear encoders, there are various technologies and innovations when compared to the market standard. On the basis of more than 25 years of experience in linear path measurement technology for mobile machines, SICK STEGMANN began by studying the market requirements and then went on to develop a radical new sensor concept. The main features include the use of magnetostriction, the optimisation of the power density by minimising measurement dead zones, and the integration of diagnostic and prognostic functionalities that can be used to avoid machine downtimes and improve operational plans and maintenance routines for entire fleets.

Magnetostriction technology offers a number of benefits when linear encoders are used in hydraulic machines. Position measurement is absolute – the precise piston position is detected as soon as on-board voltage is supplied when the machine is started up. There is no need for a reference run, as is the case with incremental sensors.

During operation, magnetostriction is exceptionally reliable, wear-free, and even robust, proving particularly resistant to mechanical stress and extreme electrical influences, such as those caused by radiated or coupled faults in the on-board power supply of a vehicle. The high level of operational safety of the MAX linear encoder as a device within vehicles that requires approval is certified by the E1 approval mark issued by the German Federal Motor Transport Authority.