The so-called AGV robot, also known as the automatic guided vehicle, is an intelligent handling robot, which can use electromagnetic or magnetic strip and other guiding devices to carry out functional movement along a predetermined route and automatically carry materials. In this process, the construction of automated logistics system needs to fully reflect the automation and flexibility of AGV robot guide vehicle, and expand the scope of application of AGV robot.
1.AGV robot with two drives and two directions
The so-called AGV robot, fully known as automated guided vehicle, also known as automatic guided vehicle, belongs to a kind of wheeled mobile robot. With the rapid development of intelligent and automation technology, more and more robots are applied in various fields, which has become an important direction of technology research and development and scientific and Technological Development in China. Advanced manufacturing technology and factory logistics technology are the research hotspot, and the research on flexible processing and flexible equipment is also more and more extensive. Among them, AGV system is an important equipment and component unit, such as intelligent warehouse, workshop flexible manufacturing and logistics system, etc.
AGV automatic guided vehicle system consists of production line control management system, local area network, dispatching control equipment, remote I / O, ground navigation system, wireless access point, charging station and guided vehicle. In the actual operation of AGV automatic guidance planning system, some auxiliary devices, transportation system and communication system are needed. (Figure 1)
2.Motion model of two-way AGV robot
2.1 3D model
The dual drive two-way AGV robot is composed of guiding body, driving module, traction module and motion module. The model is built by UI group building, and the AGV three-dimensional model is built. AGV motion system consists of 4 universal wheels and 2 driving modules, which are arranged in a central symmetrical way, i.e. 1 driving module drives 2 universal wheels. Driven by the driving module, the AGV robot can move in a straight line and turn direction. The AGV robot can move and work according to the established motion track, complete the factory handling task, and adapt to various complex working conditions.
2.2 operation model
In the design of two-way dual drive AGV robot, kinematic modeling is needed, and the following assumptions need to be made before that: Hypothesis 1, the composition of AGV robot adopts rigid material structure;
Suppose 2, the working plane of AGV robot is smooth and flat. When the robot is moving, only the roller motion is carried out, and no sliding motion is carried out;
Suppose 3, the friction between the gimbal and the ground is very small during the AGV robot's movement, which will not affect the gimbal's movement according to the rotation axis.
In the structural design of two-way dual drive AGV robot, it is necessary to reasonably adjust the distance between the universal wheels driven by two driving modules. In this study, it is assumed that the distance between the driving modules is 650mm, the distance between the driving wheels under each driving module is 237mm, and the radius of each universal wheel used is 75mm. The velocity of four universal wheels, the velocity of the middle point between the universal wheels and the angular velocity of the universal wheels are calculated. Assuming that the AGV robot moves in a straight line according to a given line, it is determined that the velocity of the universal wheel driven by the two driving modules is the same; when the AGV robot moves in a curve according to a given line, the two driving modules need to coordinate with each other and rely on the AGV robot to carry out automatic tracking motion .
3.Kinematics simulation of 3-D two-way AGV robot
3.1 formulation of kinematic simulation scheme
Based on the above discussion, UG software is used to build the three-dimensional model, and the three-dimensional model is imported into Adams for automatic analysis of mechanical system dynamics. MATLAB software is used to carry out mathematical analysis of the data information obtained by the kinematic model, establish the kinematic model, compile the kinematic equation in the MATLAB software environment, carry out kinematic calculation, and draw the kinematic model curve The simulation analysis results are extracted, compared with matlab calculation results, and the technical route is determined.
3.2 establishment of virtual prototype
In the design of dual drive two-way AGV guide vehicle, it is necessary to consider its complex structure and complicated parts. In the kinematic simulation, if Adams is directly used to import the three-dimensional model diagram, the workload will be increased, the simulation difficulty will be increased, and it is very easy to make mistakes. Based on this, based on the consideration of simulation performance, this paper can simplify and transform the three-dimensional model of two-way dual drive AGV robot into Parasolid format, and then use Adams for simulation processing to form a virtual prototype.
After the three-dimensional model is imported, the AGV components without simulation are fixed to avoid the relative motion of these components in the actual motion, and then the four driving wheels and supporting wheels are created with rotation pairs, and the motion pairs are used to connect the remaining components, and the contact between each wheel and the ground is established. After each part of the virtual prototype is connected, the drive wheel is added. A spring is installed on the driver module to increase the positive pressure for the driver module. The spring can be installed between the driving module and the workshop, the spring coefficient setting can be determined, and the technical parameter can be determined as 15N · mm to increase the preload between the driving module and the frame.
After a series of operations, the virtual prototype of AGV robot can run smoothly on the specified line .
3.3 kinematic simulation analysis
In order to simulate the walking characteristics of AGV robot, the moving track of AGV robot is set as follows: linear motion → left turn → linear motion → left turn, and cycle. In motion, the robot will turn left four times. Therefore, in the kinematic simulation analysis, the specific simulation process can be divided into four parts, each part includes a straight-line movement, a left turning movement and a turning walk, so the specific motion stage includes 16 links. In the kinematic simulation analysis, 16 functions should be written for each driving wheel, and the function is determined based on the instantaneous speed of the driving wheel of the robot The critical point velocity is calculated and the step function of four driving wheels is written. In this study, UG software is used to create the three-dimensional model of the two-way AGV robot guide vehicle, and the principle of differential speed between wheels is used,
The kinematics model of the steering motion of the robot guide vehicle is built, and the minimum steering radius of the AGV robot is determined. In kinematic simulation analysis, the motion center points of the two driving modules are set in the marker to realize the projection of the motion track on the ground. The walking track of the robot and the displacement curves of the two driving modules in X and Z directions are determined. Through simulation, it can be determined that the displacement curve of each driving module will produce curve displacement in X and Z directions, which fully reflects the simulation walking state of AGV robot. The displacement curve size and change trend of the two driving modules of the robot during operation can be seen that there is no deviation between the displacement curve and change trend. In actual motion, AGV There are repeated running tracks in the driver module of, and there is no problem of magnetic strip separation.
3.4 comparison theoretical calculation and simulation analysis results
The kinematics model of AGV robot is deduced. According to the specific results, the instantaneous speed and critical speed of the initial driving wheel are determined through ADAMS simulation. MATLAB software is needed to program. The displacement of the two driving module center points of AGV robot in X and Z directions is analyzed, and the data information is extracted. The simulation results are combined with ADAMS software The generated trajectory points are drawn in the same figure, and the simulation curve and theoretical curve formed by the motion trajectory of two driving modules in two directions are determined respectively. The simulation curves and theoretical curves of the two software simulation results are compared, and the deviation of displacement curve of AGV robot is confirmed. The reason of this situation is that the AGV robot will be interfered by many factors when it is turning. Under the interference and influence of the yaw rate, roll force and other factors, the steering angle of the gimbal wheel of the AGV robot is uncertain. Although there is deviation in the displacement curve of AGV robot guide vehicle, the deviation is small, the average deviation is not more than 0.14m, and the deviation degree is within a reasonable range.
In the design and construction of the two-way AGV robot guide vehicle, the three-dimensional model and kinematic model should be built based on the UG software. In the motion of the guide vehicle, the kinematic model of the steering motion will be built by using the principle of wheel differential speed, the minimum steering radius will be determined, and the simulation analysis will be carried out by using the advanced ADAMS software to obtain the simulation curve. Comparing the simulation curve with the theoretical curve, the smaller average deviation is determined, which can prove the rationality of the theoretical analysis of robot motion.
 Liu Xianyang, Wang Dianjun, Liu Zhanmin, et al. Kinematics analysis and Simulation of single drive unidirectional AGV robot [J]. New technology and new technology, 2015 (10): 45-48
 Wang Dianjun, Wu Chao, Chen ya, et al. Design of double drive bidirectional AGV control system [J]. Machine tool and hydraulic, 2017 (5): 16-19, 22