Absolute encoders: Maintain precise position even when unpowered

Storage systems

Racking systems have linear and rotating movements. For this purpose, these systems must be monitored and positioned with precision.

1. Vertical monitoring: 

   Accurate vertical positioning helps prevent errors that could lead to misplaced items, reducing the time and effort needed to locate and retrieve products.

   By knowing the exact position of each item, the system can quickly and accurately move to the desired location, minimizing downtime and increasing throughput. This precision is particularly important in high-density storage environments where space is limited and the margin for error is small.

   Accurate vertical positioning helps avoid collisions and mechanical failures that could occur if items are not correctly aligned. This not only protects the goods being stored but also ensures the longevity and smooth operation of the storage and retrieval equipment.

2. Shaft position and bearing operating time

   Precise shaft position monitoring ensures accurate and reliable movement of the racking system mechanisms. This precision is essential for the correct placement and retrieval of items, minimizing errors and increasing the efficiency of the system. 

   Tracking bearing operating hours helps in predictive maintenance. By monitoring the usage and wear of bearings, maintenance can be scheduled proactively before failures occur. This reduces unexpected downtime and extends the lifespan of the equipment, leading to more reliable and cost-effective operations.

AGVs and forklifts

For navigation, absolute encoders are used with AGVs and forklifts to monitor speed and steering angle due to their reliability and precision.

For pallet positioning, they are used to monitor fork width and fork height.

1. Speed monitoring in rpm
   For speed monitoring, absolute encoders measure the rotational position of the vehicle’s wheels or motor shafts. By tracking the exact position over time, the system can calculate the rotational speed (rpm) accurately. This data is used to control the vehicle’s speed, ensuring smooth acceleration and deceleration, and maintaining consistent operation.
2. Steering angle
   Absolute encoders provide precise feedback on the position of the steering mechanism. This allows the control system to know the exact angle of the wheels at any given moment, which is essential for navigating tight spaces and making precise turns. The encoder’s ability to retain position information even after power loss ensures that the vehicle can resume operations without needing recalibration, enhancing reliability and efficiency in automated environments.
3. Fork width
   Absolute encoders measure the distance between the forks. This is required for handling different pallet sizes and types accurately and efficiently. By providing real-time data on the fork width, the system can automatically adjust the forks to the correct width for each pallet, ensuring secure and stable handling.
4. Fork height
   Absolute encoders monitor the vertical position of the forks. This is important for stacking pallets at different heights and for retrieving pallets from various levels. The encoder ensures that the forks are positioned at the correct height, preventing collisions and ensuring smooth and safe operations. The precise height data also helps in optimizing the stacking process, making it more efficient and reliable.

Cut to length

Cut-to-length applications require precise length measurements to accurately cut the material into sections. This family of encoders has both a digital input and output. A position sensor can be used as a trigger to reset the encoder position to zero. After the desired count is reached, an output is sent directly to the machine for the cutting operation. This eliminates time delays and resulting mechanical displacements when signals are sent through a PLC.

1. Light spot
2. Photelectric sensor
3. IO-Link multi-turn absolute encoder

The y-splitter EVC847 makes connection easy.

ifm's absolute encoders use magnetic technology.

Magnetic encoders use Hall-effect sensors to detect rotary movements. The sensors detect the orientation of a permanent magnet attached to the shaft. A microprocessor then calculates the angle of rotation of the shaft from the sensor signals.

• High resolution and accuracy but smaller package and lower price point
• Fewer components for more robust solution
• Programmable resolution and output
• Variants available with IO-Link for process transparency

1 = Magnet, 2 = Hall sensor, 3 = Wiegand wire

Single-turn encoders

Single-turn encoders divide a mechanical revolution (0…360°) into a certain number of measure steps determined by the resolution of the encoder.

Multi-turn encoders

Multi-turn encoders provide a unique coded value consisting of the location on the disc (resolution) and the location of the gear train (revolutions).