AGVs are self-propelled vehicles whose movement is guided by software and sensors. Most AGVs move along a set path, but as mentioned above, AMRs often have more advanced technology with dynamic navigation.

AGV navigation

AGV navigation can be guided using one or more of the following mechanisms:

• Magnetic guide tape --Some AGVs have magnetic sensors and use magnetic tape to travel along the track.
• Wired Navigation - Some AGVs travel along wired paths embedded in the floor of the facility. The wires transmit signals, which the AGVs detect via antennas or sensors.
• Laser target navigation - With this method, reflective tape is mounted on objects such as walls, stationary machinery, and utility poles.The AGV is equipped with a laser transmitter and receiver. The laser light is reflected from the tape within the line of sight and is used to calculate the angle and distance between the object and the AGV.
• Inertial (gyroscopic) navigation - Some AGVs are controlled by a computerized system that verifies that the AGV is on the correct course with the help of a transponder embedded in the floor of the facility.
• Visual Guidance - The infrastructure for visually guiding AGVs does not require modifications. Cameras record features along the route and the AGV relies on these recorded features for navigation.
• Geo-guided - Like visually guided AGVs, AGVs using geo-guidance require no infrastructure modifications. Geo-guided AGVs recognize objects in their surroundings and determine their location in real time to navigate throughout the facility.
• LiDAR - LiDAR (Light Detection and Ranging) is a state-of-the-art navigation technology that utilizes sensors that emit laser pulses to measure the distance between a robot and objects in its surroundings. This data is compiled to create a 360-degree map of the environment, allowing the robot to navigate through the facility and avoid obstacles without any additional infrastructure.6 River Systems uses LiDAR navigation technology to enable its AGVs to navigate through the warehouse without changing infrastructure and to adapt to new environments if the layout of the warehouse floors changes.

AGV steering

AGV steering is controlled using differential control, steering wheel control, or a combination of the two:

• Differential Control - This is the most common type of steering control for AGVs. Differential control uses two separate drive wheels. Each drive wheel rotates at a different speed. To move forward or backward, both drives are driven at the same speed. Differential control is the simplest steering control option for AGVs and does not require additional steering motors or mechanisms. It is typically used for AGVs that operate in tight spaces or near machines. it is not used for towing applications as it can cause the trailer to break while turning.
• Steering Wheel Control - This type of steering control is similar to the steering control of a car or truck. In steering wheel control, the drive wheel is the steering wheel. Steering wheel control is more precise and smoother steering than differential control. It is typically used in traction applications and can also be controlled by the operator.
• Combination Steering - This is a combination of differential control and steering wheel control. AGVs using combination steering have two independent steering/drive motors on opposite corners of the AGV and swivel casters on the other two corners. AGVs using combination steering can turn in any direction like a car and can also travel in any direction in differential steering mode.

Traffic control for AGVs

Traffic control measures include area control, collision avoidance, or a combination of both:

• Area control - Simple to install and easily scalable, area control is a common method of traffic control for AGVs. A wireless transmitter transmits a signal in a designated area, and the AGV contains a sensor that receives the signal and transmits it back to the transmitter. If the area is clear, a "clear" signal is sent, allowing the AGV to enter or pass through the area. If there is another AGV in the area, a "stop" signal is sent to alert the other AGV trying to enter that the area is not clear. In this case, the waiting AGV will stop and wait until the first AGV moves out of the area and the transmitter signals "clear". Another way to use area control is to equip each AGV with its own transmitter, allowing it to send a "No Entry" signal to other AGVs approaching the area.
• Collision Avoidance - AGVs using collision avoidance area control are equipped with sensors that send signals and wait for a response to determine if an object is in front of them. These sensors may be acoustic sensors, which work similarly to radar, or optical sensors, which use infrared sensors. Both work on similar principles. Bumper sensors are another type of collision avoidance sensor. Many AGVs are equipped with bumper sensors as a fail-safe device. When the bumper sensors sense physical contact, they stop to avoid a collision.
• Combination Control - AGVs that use combination control are equipped with both collision control sensors and area control sensors to provide more robust collision avoidance in all situations. For example, an AGV can use area control as its primary traffic control system, but can also be equipped with crash sensors as a backup in case the area control system fails.