Terminal chassis positioning



A vast amount of freight is shipped around the world in shipping containers. At each point of transfer from one transport means to another, for example in ports and harbours, there is a tremendous number of containers that must be unloaded, transferred to a temporary stack, and later loaded on to another ship or to another form of transport.

The point of transfer of a container between a crane and a truck can be a source of delay. Usually a crane is positioned over one or more parallel loading/unloading lanes on which a truck or other vehicle stands to receive a load from or unload a container to the crane. It is important that the truck driver positions the truck chassis accurately under the crane. Inaccurate positioning of the truck chassis leads to delay in the process of transferring containers. 


This page describes a chassis positioning system done with our SIRRAH sensor TS19 protected against harbour environment and associated to beacons especially designed for this application. It improves efficiency of container handling as well as safety.

This system can give a X position. It is giving not only the final position but also an indication of the direction to move in order to reach the final position. It can be used with a trailer travelling on both side of the crane legs’ : between legs or on the back way. It can be used also to position the empty trailer before receiving the container.


         Sensor                              Protective housing


              LED Facet                               Beacon                    Complete beacon Ref. BMA1245 


Our system is made of two Sirrah SI19 sensors : one to look between the crane legs’ and one to look on the back side. It should be connected to the PLC through a serial line RS422. An option is available with a Profibus interface.

A beacon should be installed on each trailer. This beacon is a BMA1245 type.
Power is a 24VDC supply following the general power supply recommendation for trucks.
Led device are two : to be installed on each side of the trailer.
Angle of the beacon is +/- 25° ; measuring angle of the sensor is +/-9°.
The system resolution is better than +/-1cm at low frequency (10Hz) and better than +/- 4cm at high frequency (100Hz).


Measuring the angular position of one beacon with high accuracy, SI19 sensor will be able to check the trailer position regarding the expected position. For example, the sensor on the crane and the beacon on the trailer could be installed so that the final position corresponds to a 0° position on the Sirrah.

Sensor is slightly down inclined to avoid a direct sun irradiation on the sunset when oriented west and to avoid water standing on the front part of the box.

We worked on a project with 2 sensors with Dutch company TES Industrial Systems concerning the complete drive and control system for two 82/65-tons Ship-To-Shore container cranes.
The system works as follows :
The crane is fitted with two position sensors, both mounted in the centre of the crane at the landside travel boogie. One of the sensors is "looking" towards landside, one is "looking" towards waterside. Two traffic lights provide the truck drivers with information about the position of the trailer in respect to the centre of the crane. The trailers are fitted with two infrared transmitting beacons. One on each side, in the centre of the trailer. If there is no beacon detected by the sensor, the traffic light shows only green. It will remain green as long as the trailer is not in the centre. When the trailer is in the centre of the crane (some tolerance is allowed, while this can be overcome by the spreaders flippers) the traffic light shows only red.
The traffic light shows both red and green when the trailer is passed the centre, meaning the truck driver has to reverse until the light shows only red.


The crane is capable of semi-automatic loading/unloading and with this system the containers are always in the centre of the crane. Changes in the position of the crane in respect to the containers are not necessary anymore.
That means less time per move, thus more moves per hour. 

Download Application Note

Réalisation SYSTONIC 2008