Absolute redundant rotary encoder tracks angles and paths

By Mathias Roth, Branch Manager of Mobile Automation at SIKO • Edited by Lisa Eitel || Safety guidelines for mobile machines and their requirements have always influenced new mobile-machine builds. Now with the release of EN ISO 13849, new rules dictate how to reliably record angles and displacements.

In fact, draft standards such as EN 13000 for mobile cranes or EN 1175 for forklifts go further, requiring additional measures.

It’s not always possible to find sensors to fulfill such standards and satisfy requirements for service life. Plus such sensors might not be available with the necessary flexibility in terms of interfaces or connection technology.

SIKO now sells a suitable encoder for mobile machines to solve this problem. With the newVW58MR redundant absolute rotary encoder, SIKO offers a rotary encoder that allows its customers to keep a firm grasp on angles and paths, even under the most extreme conditions. The rotary encoder has a category 2 construction, allowing it to be used up to SIL2 and Pld.

TheVW58MR rotary encoder uses magnetic scanning technology. A measurement range of 4,096 revolutions (12-bit Multiturn) is over 16,384 steps (14-bit). A new and reliable gear design lets the multiturn track revolutions. Unlike battery-powered or self-contained multiturn setups, this gearing reliably tracks position for years. Two galvanically separated sensor units track position autonomously. Absolute position and speed are fed to controls through one of three interface options:

• Two separate CANopen interfaces

• A bus-in bus-out setup and two node IDs

• CANopen Safety interface

VW58MR encoder tough enough to withstand extreme environments

The VW58MR withstands harsh weather with protection class IP65/IP67 and a build that works in -40 °C to + 85 °C. One version has a housing that resists salt spray; this one also sports especially strong double ball bearings for high axial and radial loads on the shaft.

Encoder also has internal functions to simplify integration

Encoder software records slewing-ring position. Because the encoder often connects to the slewing ring via an external gear (which can cause uneven gear ratios) conversion to a 0° to 360° value is sometimes hard for machine manufacturers. This is because the position of the slewing ring should always be able to be resolved into 360° —no matter how often the slewing ring turns in one direction … and even if the rotary encoder exceeds its internal zero point after 4,096 revolutions.

SIKO software in the WV58MR rotary encoder lets users configure the number of teeth for the slewing ring and the number of teeth for the external gear in the rotary encoder — so manufacturers can generate any gear ratio. That way, the encoder returns the position and speed of the slewing ring via the interface (so the builder doesn’t need to recalculate position). Plus machine builders can use one encoder, no matter the slewing-ring size.

The WV58MR also has redundant sensors specifically for mobile machines. It can be employed in safety-critical applications up to Performance Level PLd. Thanks to its particularly robust design and special variants of housings it is ideally suited for heavy-duty use in mobile machines. Other features: