The guiding model of AGV robot not only determines the flexibility of the logistics system composed of it but also affects the reliability and configuration cost of the system operation. Until the 1980s, buried electromagnetic induction technology was still only one of the alternative guiding technologies. With the development of electronic technology and the diversification of AGV-oriented technology and guidance methods, the performance of AGV robot is further improved and can adapt to more complex working environments, and the application is more extensive.
The guiding method can be divided into external guiding and internal guiding according to the source of AGV guidance information. The former refers to a process when provided with a guiding information medium such as a wire with a variable-frequency induction electromagnetic field, a magnetic tape or a ribbon on the running path of the vehicle, and the characteristics of the guiding information such as frequency, magnetic field strength, light intensity, etc. are detected by the sensor on the vehicle, then, the information is processed to control the vehicle to travel along the guiding route. The latter, however, involves a pre-setting on the vehicle of the running path, detecting the current position coordinates of the vehicle in real-time during vehicle operation and comparing with the preset values to control the running direction of the vehicle, that is, using the so-called coordinate positioning principle. In addition, the guiding mode can be further divided into a wired and wireless type according to the form of the AGV robot guiding line. Ultrasonic guidance, laser guidance, and optical guidance in an external guide can be referred to as a signal reflection method, and an internal conduction one can be referred to as a reference position setting method.
Among the above various guiding methods, the guiding technologies used mainly include electromagnetic induction technology, laser detection technology, ultrasonic detection technology, light reflection detection technology, inertial navigation technology, image recognition technology, and coordinate recognition technology.
Electromagnetic guidance is divided into a single-frequency system and multi-frequency system guidance. The former is a single-frequency current through the entire line, controlled by the on-off current signal. In this way, it is required to set up a centralized control station and install the on-off interface of the sensing mark and the branch road at the intersections and branches of each line. The latter is an electromagnetic signal with different frequencies on each loop or branch route, and the AGV robot can only operate when it receives an electromagnetic signal of the corresponding frequency. This guiding method has high reliability but requires high flatness of the ground, and it is difficult to change the running path.
In laser detection technology, AGV robot receives the fixed set of 3-point positioning laser signals in real-time, calculates its instantaneous position and running direction by calculation, and then compares it with the set path to guide the vehicle to run.
Optical detection technology is used to guide the running direction of AGV robot. Generally, a ribbon with stable reflectivity is laid on the running path. The vehicle is provided with a photoelectric sensor that emits and receives reflected light and compares the detected signals to adjust the running direction of the vehicle.
Ultrasonic testing technology uses the wall or similar objects to position and guide the reflected signals of ultrasonic waves, thus improving the flexibility of the path under certain circumstances. At the same time, since the mirror surface is not required to be provided, the guiding cost is also reduced. However, the application is still very difficult when the reflection of the operating environment is more complicated.
Moreover, there are other guiding technologies like inertial navigation technology, image recognition technology, and coordinate detection technology, which are not frequently used as the ones mentioned above.