Automated Guided Vehicles (also known as AGVs) are often used in warehouses to perform the logistics operations. Think of moving loads on very high racks to a conveyor belt or collecting requested pallets. In this article we will discuss the application of laser distance sensors in AGVs: what are the possibilities and which sensor is suitable for your problem?
How does a laser distance sensor work in AGV's?
AGVs move horizontally and vertically to navigate to the correct warehouse rack but also to reach a pallet on a higher rack. High level order pickers, for example, can reach a pallet up to 12 meters high. In order for this navigation through the racks and the positioning relative to it to operate smoothly, the AGV needs information about its environment. The laser distance sensors provide this step-by-step as follows:
1. Emitting a laser beam
2. Receiving a reflection
Mounted laser distance sensors emit high frequency laser beams. A beam reaches an obstacle like a person or another AGV. Beams are used not only to detect or measure horizontally, but also vertically. Laser distance sensors are ideal for distances from 30 meters to 3000 meters, depending on the model and application.
The object on which the laser beam shines is reflected. The reflection serves as input for the sensor to detect not only objects and people but also the relative distance to them. This reflection is guided to the integrated light sensor by the optics .
3. Processing the signal
The received reflection has reached the light sensor, which enables it to be evaluated. The distance can be determined on the basis of the time course between the emission of the light beam and the receiving of the reflection. This principle is called the lead time or time-of-flight. If the distance to an object is known, it can be determined whether it is a permissible value. When collisions are prevented, this answers the question of whether it is a safe distance or not.
Once the signal has been processed and the sensor has determined that the distance is safe, judging the values according to the preset parameters allows the AGV to continue driving. This is done by the output signal that the sensor transmits to the AGV. In the case of an object that is too close to the vehicle, the AGV receives a different output from the sensor, which may slow it down or stop it immediately.
Examples of applications
The size of of warehouses diverge from conventional (6-10 meters high) up to high-rise warehouses of 40 meters. The applications described below are present in these warehouses, independent from the size. Laser distance sensors that are used in these applications contribute to a logistic optimization of your warehouse and warehouse activities.
Positioning for logistic optimization
Detection of objects
For activities in pick-and-place applications of AGV's the laser distance sensors are useful, not only because they can reach very big distances, but they also do this very fast and extremely precise. The laser sensors can be applied to reach distances up to 3000 meters and offer a measurement accuracy down to milimeters. Because of this, process errors that cause loss of time will be prevented.
The AGV's provided with laser distance sensors can be positioned within the warehouse. An operator as well as the AGV then knows where it is located. This ensures that the AGV knows its way to the desired racks and pallets.
Anti-collision from obstacle detection
Human detection (safety)
During the navigation to the right pallet or rack, the obstacles and objects the AGV encounters should also be noted. The laser distance sensors determine the distance to an obstacle and can adapt the movement speed to prevent a collision. This way, accidents and errors are prevented by the AGV and unnecessary costs in time and money, which arise from damage and downtime, can be spared.
The laser distance sensors can detect objects as well as people. When using these sensors, physical damage will be prevented by slowing down or stopping the AGV's if a person is detected in an area where vehicles are operating. The laser distance sensor forms a basis for personal safety, however for a certified security, the use of certified machine safety components is recommended.
Which sensor is best suited for your challenge?
Below an overview is given of our sensor solutions with their differences in specifications for comparison:
|Measuring range*||Measuring range**||Switching frequency||Price range|
|LAM 50 series||30 m||150 m||Tot 50 Hz||€|
|LAM 70 series||125 m||250 m||Tot 40 kHz||€€|
|LAM 300 series||300 m||3000 m||Tot 10 kHz||€€€|
|LAM 1200 series||600 m||1200 m||Tot 400 Hz||€€€€|
*) Maximum range on natural surfaces
**) Maximum range on target board and/or reflector