CANbus comms take position in the warehouse

Sensor-Technik has applied CANbus absolute position encoders to a fleet of forklift trucks.

With automatic collection of goods from, and placement in, storage bays prevalent in modern warehouses, precision feedback is essential to ensure that the computer controlled forklifts are in the correct position.

Sensor-Technik was asked for a sensing solution that could be fitted on the back of an electric motor to provide accurate absolute position information.

The position information also need to be part of a closed loop with the motor to compensate for overshoot.

The solution also had to provide security interlocks for the mainframe computer to eliminate the possibility of damage through overrun.

A CANbus absolute position encoder was chosen.

This assured a simple interface to the mainframe computer and meant each forklift truck could have its own system, with the onboard computer reading the output and controlling the motor accordingly.

The solution had the added benefit that information could be easily sent to all forklift trucks.

This provided a means to enable the closest forklift truck to a given item to make the collection, eliminating complex addressing and significantly reducing communications times.

To meet security requirements, mechanical switches were mounted on the back of the encoder to stop the vehicle in the case of overrun.

The software and hardware setup were by no means trivial, but the biggest problem was to mount the encoder in the small space available without compromising airflow to the motor.

Sensor-Technik solved the problem by modifying the cable entry and connections.

The CANbus communications are both secure and proven, giving high reliability and assured system integrity - the key to making this automated positioning system possible.

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