Rotary encoders Safety level for mobile vehicles

Related Vendor

Wuxi InfiMotion Technology Co., Ltd.

Safety first – this applies to mobile vehicles and especially for Automated Guided Vehicles (AGVs) and Autonomous Mobile Robots (AMRs) without direct monitoring by persons. Various sensors, such as those from TWK, ensure safety.

Be it the steering angle, wheel speed, vehicle tilt, or vehicle vibration: these measurements must be quickly and securely captured in an AGV or AMR and then transmitted to the control system via a fast safety interface. The industrial standards Profisafe over Profinet, Failsafe over EtherCAT (FSoE), and CANopen Safety are suitable as interfaces.

The safety level is at least SIL2 or even SIL3

Safe communication between the sensor and control system is ensured by transmitting additional CRC checksums or by dual data transmission – both normal and bit-inverted. The safety level is at least SIL2 (IEC 61508) or PLd (ISO 13849). For some applications, even SIL3.

The TBSN/TRSN model series comprises encoders for high demands on functional safety. They are certified with the classification SIL3 and conform to ISO 26262 ASIL-D. Thus, they can be used in particularly safety-critical applications, such as in public road traffic. Examples include remotely controlled vehicles that are moved without a driver present. They are remote-controlled from a workstation. The operator can remotely steer a vehicle equipped with cameras and remote technology to the desired destination from his station, which is equipped with monitors, pedals, and a steering wheel. And, of course, back again. Fast internet according to the 5G standard is envisioned for transmission to the vehicle.

Output via CANopen Safety

The position value is captured redundantly and processed independently in two microprocessors. The output is via the CANopen Safety protocol. The single-turn variant TBSN offers a resolution of up to 65,536 steps per revolution. In the multi-turn variant TRSN, an additional 4096 revolutions are captured.

Thanks to a housing made of magnetically shielding stainless steel, these devices can be placed directly on a motor without distorting the measurement result. The same is ensured by high EMC/ESD resistance.

An operating temperature range of -40 °C to 70 °C and protection class up to IP69K allow for use even under adverse environmental conditions – including high shock and vibration loads. The design, with just a 42 mm outer diameter, can also be used in confined spaces.

Further examples of rotary encoders in miniature form include devices with a very short housing depth of, for example, 30 mm with a CANopen Safety interface or fully redundant devices with CANopen or analog output, which, although not certified, can also be used for safety-oriented applications due to their redundancy.

The safety functions of the sensors can be supplemented, upon request, with safety switching outputs in the backlash-free cam switchgear NOCx or in the vibration sensors NVx for condition monitoring. Custom solutions and additional interfaces are also possible.