Practical “CANopener” for programmable encoders and inclination sensors

06May

posted by: Martin Hummel and Clemens Merkle, SICK Stegmann

The process for integrating sensors into a CANopen fieldbus differs for nearly every single automation system and, until recently, has required specialist knowledge of control solutions.

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This work is now a thing of the past thanks to the compact, portable PGT-12-Pro programming tool: programmable absolute encoders and inclination sensors with CANopen interfaces are incorporated into this communication protocol without any need for programming. A real-life “CANopener”...

The PGT-12-Pro is the world’s first portable programming tool for sensors with a CANopen interface and is currently designed for configuring and connecting programmable AHS/AHM36 absolute encoders and inclination sensors in the TMS/TMM61 and TMS/TMM88 product lines with a CANopen interface or an analogue output. New sensor variants with CANopen and new functions for the programming tool can be installed easily via a firmware update. Storing configurations to the device’s SD card is just as easy. When replacing a device, they can be transferred quickly and also cloned for any number of identical applications and configurations. When used as a basis for wire draw encoders and inclination sensors, the CANopen combination of the PGT-12-Pro and the specified absolute encoders is an interesting automation package for the areas of commercial vehicles, agricultural and forestry machines, and industrial, municipal and special vehicles.

Compact and with CANopen: the programmable AHS/AHM36 encoders

The PGT-12-Pro is the latest advance in SICK encoder programming tools, ideally suited to market and user needs. One of the product families that benefits from the tool is the AHS/AHM36 line of programmable absolute encoders in the 36-mm compact housing. While the AHS36 single turn version offers practical 14-bit resolution, the AHM36 battery-less multiturn version with transmission gear provides a full 26-bit resolution. A rare feature for encoders in the 36 mm class, encoder variants with a compact, universal cable outlet and IP69K enclosure rating will be available especially for installation into vehicles (where space is often tight) from the end of 2016 onwards.

Both encoder variants offer an assortment of adjustments that the PGT-12-Pro can access directly. This includes properties like the number of increments, the pre-set value, the rotation or count direction, or the sampling rate for calculating the speed. Measuring ranges can be defined individually, as can the thresholds for speeds or temperatures. The round axis functionality can also be adjusted with the help of the programming tool. As a result, the AHM36 can be freely adapted to any gear stage across the entire resolution. This saves the need for complex machine modifications, transmission calculations, and controller programming – thereby saving money during installation, commissioning, maintenance, and service. The encoder’s operating parameters (e.g. the maximum temperatures and speeds reached or the current shaft position) can also be read out at any time, not only via the control unit but also using the PGT-12-Pro. When using the encoders in measurement-based SICK wire draw systems (a common application in mobile automation), the number of changes in rotation direction can indicate wear-and-tear in the wire draw mechanism; thanks to the programming tool, these signs can be detected at any early stage. All of this information helps to avoid the risk of unscheduled machine stops as well as optimising availability.

When it comes to integration into CANopen, all relevant parameters can be adjusted in the encoders using the PGT-12-Pro. The node ID – already configured upon delivery – is easy to adjust in the event of conflicting addresses. The encoder’s baud rate can be adjusted to the conditions in the fieldbus, as can the frequency and type of parameter transfer. This allows the data transmission load to be optimised and, with it, the speed in the bus. With variable PDO mapping (PDO: process data object), the objects to be transmitted can be freely assigned to the encoder using the programming tool. The control unit also does not have to be programmed when choosing between node guarding and the heartbeat protocol as the method for monitoring the CANopen nodes. Users will also find that the option to use the portable programming tool in the design office, on the machine, or in vehicles out in the field alike makes their work a lot easier – an argument that also applies to programming inclination sensors with an analogue and CANopen interface.

Capacitive inclination sensors: the ideal addition

The inclination sensors from the TMS/TMM product family are a logical addition to the SICK portfolio in the area of position detection and distance measurement. The single-axis sensors with a 360° inclination range and the dual-axis designs for inclinations in the range of +/- 90° are based on a capacitive measurement principle (MEMS: micro-electro-mechanical system). Applying a high level of precision, they measure aspects such as tilts, sloping positions, angles, and levelling for rotation and horizontal axes. The portfolio ranges from space-saving inclination sensors with analogue outputs and installation-friendly versions with a CANopen interface to programmable, high-precision sensors. When combined with AHS/AHM36 absolute encoders and wire draw encoders in the EcoLine or HighLine product families, they provide a universal solution to demanding sensor requirements, particularly in the area of mobile automation.

The highly rugged TMS/TMM inclination sensors are available in an array of different construction sizes and housing materials and with both analogue and CANopen interfaces. They can also be adjusted using the programming tool, just like the absolute encoders in the AHS/AHM36 CANopen product family. In the CANopen versions of the inclination sensors, the PGT-12-Pro can be used to adjust aspects such as the zero positions of the x and y axes, the pre-set value, the change in the rotation direction on both axes, and digital filters. It can read out values for the x and y inclination angle. In terms of the node ID, baud rate, and CANopen node monitoring, the CANopen connection offers the same level of comfort and the same look and feel as the encoders – operators always work with the same interface that they are already familiar with. Furthermore, the PGT-12-Pro allows the output for analogue inclination sensors to be configured. Users are able to configure the angle measuring range, the lower and upper threshold for the output signal, and the change in rotation direction, along with the type and limit frequency of the digital filter. Whether you are using CANopen or an analogue interface, the programming tool is ready to go at the touch of a button without you needing to install external hard- or software, while still offering several language options. The option to update the firmware makes sure that new encoders and inclination sensors – as well as new programming functions – can be installed at any time.

The all-in-one solution – and more – for mobile automation

The PGT-12-Pro programming tool, the absolute encoders from the AHS/AHM36 product family, the EcoLine/HighLine wire draw encoders, and the TMS/TMM inclination sensors form a perfectly tuned all-in-one solution that is easy to integrate into CANopen. They meet fundamental requirements for the automation of mobile machines, such as commercial vehicles, agricultural and forestry machines, and industrial, municipal and special vehicles. They can also be used in transport logistics, e.g., in manned forklift trucks or automated guided systems and assembly platforms with the corresponding handling kinematics. The PGT-12-Pro is the world’s first mobile programming tool of its kind and successfully proves its worth as a CANopener – a practical gateway for sensors into the world of CANopen field bus topologies.