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Structural analysis of welding roller carrier

Source of the article:admin popularity:Time of publication:2021-1-3

1. Anti channeling mechanical actuator
 
The axial movement of the weldment on the roller carrier means that the weldment itself is in spiral motion. If measures can be taken, the left rotation of the weldment on the roller carrier can be changed to right rotation in time, or the right rotation can be changed to left rotation, until the weldment is no longer in spiral motion.
 
At present, there are three kinds of actuators that can accomplish this task
 
(1) Jack up actuator
 
The roller on the ground side of the driven roller carrier can move up and down to offset the axis of the weldment and change the axial component of the weight of the weldment. The advantages of this method are high sensitivity, but the disadvantages are high cost and large volume.
 
(2) Offset actuator
 
The rollers on both sides of the driven roller carrier can be offset in the same direction along its vertical center line, so as to change the axial friction component between the roller and the weldment. This adjustment method has the advantage of high sensitivity, but the biggest disadvantage is that it has too much wear on the roller.
 
(3) Translational actuator
 
The rollers on both sides of the driven roller carrier can move horizontally perpendicular to the axis line of the weldment at the same time, so as to achieve the purpose of adjusting the axis line of the weldment and the included angle of the roller axis. The advantages of this adjustment method are good stability, low manufacturing cost, simple structure and no additional installation space.
 
2. Driving wheel speed control
 
In order to make the weldment rotate smoothly with stepless speed regulation, two driving modes are generally adopted: DC speed regulation and AC frequency conversion speed regulation. Due to the defects of high failure rate and high cost in DC speed regulation, AC variable frequency speed regulation is selected. With the development of electronic technology, AC frequency control has been able to meet the needs of various tonnage welding roller carrier.
 
In order to make the distance between the rollers of the welding roller carrier convenient and reliable, and the combination convenient, it is suggested to adopt the design scheme that the driving wheel is driven separately, that is, each driving wheel is driven by a motor and a deceleration mechanism separately. However, here we should pay attention to solve the problem of synchronization of each driving wheel, and try to choose the same characteristics and measured use in the selection of motor and reducer structure. In the driving mode, it is recommended to use a set of driving source, each driving wheel motor in parallel.
 
3. Detection of axial movement of weldment
 
The purpose of detecting the axial displacement of the weldment is to detect the axial displacement of the weldment. In principle, it can be detected on the side of the weldment cylinder wall and on the end face of the weldment. It is not easy to make a reliable sensor because the vertical rotation component of the cylinder wall is removed, and the influence of slipping, rough surface and dirt is added. At present, the detection method of the end face of the weldment is a common detection method, which is inevitably affected by the uneven direction of the end face of the weldment perpendicular to its axis, so it is required to process the end face of the weldment. However, for large weldments, the higher the accuracy required, the greater the difficulty and cost. It is very important to reduce the requirement of face machining. For example, the process requires that the axial displacement of the weldment is not greater than ± 2mm, but the measured end surface roughness of the weldment is greater than ± 2mm. Under this condition, whether the axial displacement of the weldment can be prevented is one of the important indexes to measure whether the anti displacement roller carrier is practical.
 
4. Fuzzy control
 
For a weldment, especially for a large weldment, it is difficult to know the perpendicularity and unevenness of its testing end face relative to its axis. It is sometimes unrealistic to rigidly stipulate that the machining error of the end face should not exceed a certain value. Under this condition, how to achieve the goal of anti channeling for different weldments, even zero channeling, is the key.
 
For the control system such as anti channeling roller carrier, in the case of many uncertain factors affecting the axial movement of weldment, fuzzy control can be used to achieve the control purpose. Fuzzy control is to use computer to simulate human's way of thinking and control according to human's operation rules, that is to use computer to realize human's control experience. Fuzzy mathematics can be used to describe the fuzzy concepts such as process variables and control actions and the relationship between them. According to these fuzzy relationships and the detected values of process variables at each time, the control variables at that time can be obtained by fuzzy logic reasoning. Fuzziness and precise control are dialectic relations. Computer carries out fuzzy control by imitating human thinking, while human brain's heavy control experience is a fuzzy control rule composed of fuzzy conditional sentences. Therefore, it is necessary to transform the input signal from the precise quantity to the fuzzy quantity. Firstly, the sampling value of the input signal is transformed into a point on the corresponding domain (range transformation), and then it is transformed into a fuzzy subset on the domain. On the contrary to fuzzification, the process of defuzzification is to transform the fuzzy control function obtained in the process of reasoning into precise control quantity.
 
Welding roller carrier
 
Welding roller carrier
 
However, it is not enough to solve the problem only by using fuzzy control theory in order to achieve the goal of anti channeling for the control system that the end error of controlled weldment is greater than the precision of anti channeling. Because the end error of the weldment is greater than the requirement of anti channeling accuracy, whether the offset sent by the sensor is caused by the end error of the weldment or by the axial movement of the weldment, the computer can't distinguish from the signal sent only, and the error size and shape of different weldments are different.
 
5. Adaptive control
 
Adaptive control has the ability to modify its own characteristic parameters to adapt to the dynamic characteristics of the controlled plant and disturbance. In the adaptive system, the algorithm we use is "parameter tracking algorithm". That is, the computer automatically tracks the signal and preset the action threshold. These parameters are not fixed in the control process. Generally speaking, let the computer remember the shape of the end face of the weldment first, and then distinguish the real displacement. In this way, the problem is simple, as long as the channeling momentum is controlled and the end error is ignored. Following this idea, after a period of adjustment, the weldment can achieve "zero movement" in its axial direction. The length of the adaptive process depends on the end face error of the weldment. For the weldment with an end face error of 5mm, the displacement can be limited to ± 2mm after about 15min, and the weldment can maintain "zero displacement" after about 0.5h.

Keywords of this article:Structural,analysis,welding,ro