Selecting crane and trolley positioning requires matching accuracy, speed, environment, and control needs. For short travel, absolute encoders on wheels or gearboxes are cost-effective. They give reliable feedback, but wheel slip can reduce accuracy. Laser distance sensors are widely used for trolley positioning. They provide millimeter accuracy over long runways, but need clear line of sight and stable reflectors.

In dusty, hot, or foggy areas, lasers may struggle. RFID and barcode systems are robust alternatives. They provide absolute position at discrete points, ideal for parking, zone control, and anti-collision. Continuous motion needs interpolation or extra sensors. Indoor cranes often use laser radar, vision, or UWB for flexible layouts. These track multiple cranes and obstacles. GNSS suits outdoor gantry cranes and large yards, though accuracy and update rate vary.

Key factors include repeatability, resolution, update rate, communication protocol, and safety certification. A fast PLC must read the sensor quickly. Choose PROFINET, EtherNet/IP, Modbus TCP, or CANopen to match the controller. For safety, use redundant sensors or certified encoders. Plan for maintenance: dirty lenses, damaged reflectors, and loose tags cause downtime. Mount sensors protected but accessible. Test in the real environment.

A hybrid approach works best: laser for continuous trolley travel, encoders for hoist and RFID for end stops. Define needs, compare accuracy and cost, verify integration, and plan service.