The function of the suspension is to adjust the positive pressure on the steering wheel, ensuring that the positive pressure on the steering wheel is not too small to cause slippage. In order to prevent traction failure, it is necessary to ensure that the positive pressure of the steering wheel is not too large, which will lead to excessive traction current and cause a series of problems or even cause the steering wheel to overload.
The most commonly used part of the suspension is the spring, which uses the compressed elasticity of the spring to automatically adjust the positive pressure on the steering wheel to ensure the normal operation of the AGV . At the same time, most suspension mechanisms have a device that can adjust the initial compression or pr-compression of the spring , thereby It greatly improves the design margin and the convenience of later adjustment. The structural type of the suspension and the selection parameters of the spring are very important. The normal operation of AGV has a decisive impact on it. A well-designed suspension system can improve the adaptability and operation efficiency of AGV to the environment. The stability of the line.
Below we take the most common gear train with 4 auxiliary wheels and 2 steering wheels as an example .Before
calculation, we must first clarify the two parallel
The reference plane is: one is the reference plane based on the ground plane, and the other is the reference
plane based on the vehicle frame as the wheel system installation surface
For the sake of simplicity, we assume that the two auxiliary wheels on one side, the steering wheel and the suspension are at the same height, and the unevenness of the ground is the same as the ground level. The surface can be symmetrical or asymmetrical. The simplified simulation diagram is shown below:
As shown in the figure above, the steering wheel repeatedly moves up and down based on the ground plane when running, like the Lankan hexagram. The spring coefficient selected for the suspension The size and pre-compression of the spring must meet the following three conditions:
when fully loaded, the steering wheel does not slip on the concave surface of the ground and does not The steering wheel can be overloaded, and there are no auxiliary wheels hanging in the air at ground level when the vehicle is empty .An AGV Heavy 3 t, carrying cargo weight 5 t (Cargo center of gravity coincides with vehicle center of gravity/center ), steering wheel maximum load 2 t, The sliding friction coefficient is 0.3, the rolling friction coefficient is0.03, and it needs to run smoothly on a ground with a flatness of ±10 mm . How to choose the stiffness coefficient and pre-compression of the suspension spring?
According to the question, assume that the pre-compression of the suspension spring is L. That is, it is compressed by L when the ground is flat , by L-10 mm when the ground is concave , and by L-10 mm when the ground is convex. The surface is compressed by L+10mm, and the spring constant is K.When the fully loaded AGV steering wheel is at -10 mm from the ground, the weight on one side is 4 t. To ensure sufficient traction on the steering wheel, you must satisfy:
0.3*F positive pressure 1>=(4- F positive pressure 1)*0.03 F Positive pressure i>=0.36t=360kg K>=360/(L-10)
When the steering wheel of an empty AGV is at 0 mm above the ground, the weight on one side is 1.5T, and the positive pressure of any of the two auxiliary wheels must be ensured . Not less than 0, then it must satisfy:
F Positive pressure 2<=1.5/2=750kg and Pressure Shrink quantity For L K<=750/L
When the fully loaded AGV steering wheel is at +10 mm from the ground, the weight on one side is 4T. To ensure that the positive pressure on the steering wheel is less than 2T, the following conditions must be met
K<=2000/(L+10)
Based on the above calculation formula, the calculation results have three sets of data, as shown in the following :
From the above table, we can conclude that the combination of spring stiffness coefficient and pre-compression is the key to suspension design. How important it is that the frame mechanism has an adjustable device for the initial compression or pre-compression of the spring .
Summarize :
This article not only introduces the key requirements for AGV suspension design, but also details how to quickly calculate spring stiffness and pre-compression. Method, in actual work, the optimal spring stiffness coefficient and pre-compression can be selected according to the calculation results. Analysis is the most important thing. Please do not simply apply or take certain content out of context as your reference.
