Overhead cranes are used for lifting and moving around heavy materials or objects in a warehouse or factory. To make this operation run without problems the overhead crane needs information about the environment. There is a number of situations in which an automated system, like a sensor, can provide a solution with the right functionalities.
In this article we discuss the functionalities of sensors that provide crucial solutions in industrial applications with overhead cranes. In addition to this a selection of sensors will be highlighted with relative advantages and disadvantages to provide you with an educated choice for a solution.
Safety and control are of utmost importance in an application in which multiple girders have to operate (synchronically) on the same track of the crane. In the event of one of the girders moving in an incorrect position, the center of gravity of the load is deviated. Another risk among these crane girders is a collision as a result of an error in the control system.
The solution for such applications are sensors with a so-called tandem function. This functionality makes it possible to make two overhead crane girders can constantly monitor each others relative position in order to adjust movement speed and positions accordingly. For this, the sensors make us of Time Of Flight-principle (TOF). A signal is sent out from the sensor to a reflector or a receiver. Based on the time difference between the sent and received signal the sensor can determine the distance. When a preferred distance (within the maximum range of a sensor) has been configured, the sensors maintain this distance between the two girders.
Another important functionality that provides a solution in the automation of overhead cranes is the anti-collision function. The sensors that support this function provide an adaptive movement speed of the crane towards an obstacle. This could be another crane or a wall, for example.
Sensors with an anti collision function also make use of the TOF principle (Time Of Flight) to determine a distance. However, this function is used to decrease the movement speed in contrast to the aforementioned tandem function that synchronizes it. The speed with which the crane moves is slowed down gradually. This way a desired speed can be set in order to define a movement speed per distance to an obstacle. This ensures that an overhead crane moves at a normal working speed in the first ten meters to an obstacle and half the speed in the second five meters. By the constant calculation of the distance by sent and received signals the sensor can determine when the movement speed has to be adjusted. The smaller the distance, the more the speed decelerates with gradual transitions until a complete stationary position.
Below here you can find a description of a selection of highlighted sensors that excel in applications with overhead cranes. The mentioned sensors can be used for the tandem function as well as the anti collision function. However, the LAM 5.21 is the only sensor that contains these functions as a built-in and preprogrammed feature. The other two options require a configuration through a PLC, for example (Programmable Logic Controller). Based on this you can make an educated selection for the sensor that suits your preferences and the demands if your application. If it’s still a hard choice to make, then one of our experts is ready to help you with it. Please contact us!
|LAM 5.21||LAM 50||LAM 70|
|Function support||Preprogrammed||To be set by the user||To be set by the user|
|Switching frequency||100 Hz||10 Hz||40 kHz|
|Measurement range with reflector||70 meter||150 meter||270 meter|
|Measurement range without reflector||N.A.||30 meter||125 meter|
|Operating temperature||-10 … +50 °C||-40 … +50 °C||-40 … +60 °C|
|Accuracy||30 mm||+/- 3 mm||+/- 60 mm|