How Does an AGV Navigate Safely?
This is an article first published in Workplace Material Handling and Safety Magazine at https://www.workplacepub.com/material-handling/agvs/how-does-an-agv-navigate-safely/https://www.workplacepub.com/material-handling/agvs/how-does-an-agv-navigate-safely/
Automated Guided Vehicles (AGVs) represent the next step in the evolution of the assembly line. AGVs are set to transform manufacturing in the near future. As the name suggests, the operations of AGVs are completely automated― no human guides the vehicle. It is natural to doubt whether AGVs can cause accidents like cars on the road. But the fact is, AGVs are actually safer than cars driven by human operators.
Once you have an understanding of how AGVs navigate, you will recognize how and why AGVs are a much safer option than traditional conveyance.
AGVs need to know their position in the manufacturing plant or assembly line to navigate effectively. There are two ways to determine position: relative and absolute. Absolute position measurement uses the absolute position as it is mapped. Whereas, in the relative positioning method, the position is calculated relative to a reference point determined in the factory. With this basic information, we can take a look into the different navigation methods employed by AGVs and how safety is ensured while working along with people.
Here is an example of how magnetic tapes are used to control the AGV. Magnetic tapes, which are available as self-adhesive tape and are easy to install, are laid on the track. The AGV then moves only over the magnetic tape.
The advantage here is the low cost of implementation. It is also easy to shift the operations from one area to another. To add additional areas to be covered, the system just needs additional magnetic tape and the rest can be expanded at the software end, implemented with minimal disruption.
Safety with Magnetic Navigation
Magnetic strips will be clearly visible on the factory floor. AGVs move only along the track laden with magnetic tapes. People can easily avoid the track to avoid collision with the vehicle. The vehicles will also be equipped with proximity sensors. Proximity sensors detect any object in its path by emitting magnetic radiation. There should not be any object in the path of the AGV as it has a dedicated track. The controls are coded in such a way that the AGV stops movement if any object is detected in its path.
It is much similar to optical navigation. Instead of magnetic tapes, paint or bright-colored normal tapes are used. The vision sensor system can detect the tapes that have clear contrast with the factory floor and centers the vehicle over the tape. Another way of implementation is to have barcoded tapes. It is particularly helpful to implement tracks that diverge and converge. The path can be easily changed with this system.
Safety with Optical Navigation
AGVs with optical navigation can also implement proximity sensors. Once an object is detected in the path, it stops automatically. Another way is to detect people and obstacles using the optical sensors equipped with the AGV. Depending on the capability of the optical sensors and the software associated with them, optical sensors can be used to detect obstacles in the path. Proximity sensors are the easier and cheaper option as sensing obstacles with optical sensors require higher software and processing capabilities.
Light Detection & Ranging
Light Detection and Ranging (LiDAR) is a relatively new technology that has seen wide adoption in autonomous vehicles. It functions similarly to Sonar or Sound Navigation and Ranging. Instead of sound waves, laser pulses are sent out in every direction of the AGV. The LiDAR sensor detects the laser pulses that reflect off the objects and walls around it. This can be used to construct a useful 3-dimensional map of the environment. This map is updated in real-time. Since lasers are much faster than sound, the area can be mapped really fast and is also updated multiple times every second.
Safety with LiDAR Navigation
As mentioned earlier, LiDAR uses laser technology to obtain a three-dimensional map of its environment. It clearly indicates the obstacles and other objects in the surroundings. This can be used to chart a path. Unlike the previous modes of navigation, LiDAR-enabled AGVs do not depend on a track to navigate. They can weave in and out of any path with great flexibility. When it detects an object in its path, it can reroute in such a way as to avoid the obstacle.
The fast lasers are used to update the environmental model multiple times in a second. It helps to detect moving objects, the direction and the speed of movement. Complex algorithms can work out the trajectory of the moving object and can chart a path to avoid the moving object. In that way, LiDAR provides a dynamic safety mechanism.
Miscellaneous Safety Features
AGVs can use a mix of the safety features mentioned above. In addition to that, it can also employ sound and light-based signals to alert of its presence.
- Sound: AGVs can be equipped with sound systems that will warn people around of their proximity. It can be implemented so it beeps continuously while it is in operation or beeps only when it detects an obstacle in its path. Proximity sensors or other object detection technology already available can be used to trigger the warning sounds. This will help to clear the path.
- Light: AGV can be equipped with normal light or strobe lights to indicate its presence. Strobe lights catch the attention of the people around and they are bound to move out of the way. Lights can also be used to indicate various states of AGV or the manufacturing process.
- Rerouting: Here the AGV changes its course to accommodate the objects in its path. A combination of sensors and computer algorithms can be used to change the path to avoid obstacles. WMHS
AGVs not only provide operational efficiency compared to the traditional assembly line, but also superior protection to the people around its operation. AGVs can be used to eliminate the hazards of traditional assembly line conveyance. Get in touch with the team at RedViking to learn more about how AGVs can help your operations (www.redviking.com)