A signal loss fault analysis

Our factory mainly produces panels. For those things that weigh hundreds of pounds, transport vehicles are indispensable for moving around the factory. So the most common type of vehicle in our factory is the shuttle bus. This type of vehicle is similar to a train and runs on steel rails.

The electrical equipment is mainly composed of travel motor, positioning motor, and servo control module. In addition, there are two induction switches, one is used for positioning tight, that is, to ensure that the tracks are consistent, and the plates can pass between adjacent tracks during transportation. The other is for positioning loose, which is a signal to confirm that the shuttle bus is in a state where it can move.

Today at work, the operator called to say that the shuttle bus was stuck (the positioning mechanism was stuck on the positioning pile, making the car unable to move normally) and could not move. After receiving the call, I rushed to the scene quickly. I had dealt with this problem of pile jamming frequently before, so I felt it was relatively simple.

The solution is to reverse the phase sequence of the positioning motor wires so that the positioning motor can rotate in reverse, so that the stuck part will come off the pile. After arriving at the site this time, I observed that the positioning mechanism was not stuck on the positioning pile, but the entire shuttle bus could not move, and the state was very similar to that of a stuck pile.

I checked the positioning motor, the travel motor and the two sensor switches that determine the position, and there was no problem, but the shuttle bus just couldn't move, which was a bit troublesome. Because I had never encountered such a problem before, I could only look up the electrical drawings to see if there was a soft fault somewhere.

After checking for a long time, there was no problem. However, when I looked at the operation screen, I found that when the sensor switch received the sensing signal, the corresponding module did not respond. So I called the old master and he said that there was a problem with the display module and it did not display when sensing.

Based on this problem, I rotated the positioning mechanism and found that the sensor switch was actuated in a place where it should not be tightly positioned because it was close to the guide rail of the positioning mechanism. This action would cause the system to determine that the shuttle bus was in a tightly positioned state and could not move, and the display module had a problem, so the shuttle bus could not move.

I turned off all the power of the shuttle bus and restarted it, and adjusted the position of the sensor switch of the positioning mechanism. The problem was solved when I tried it again. In fact, it was because there was a wrong action in the middle, and the positioning mechanism was in the wrong position, which finally caused the entire shuttle bus to be stuck and unable to move. So far, this problem has been solved, and it doesn't seem complicated at all.

For many machines that we have not repaired, we must consult the old master about some hidden problems of the machine, because these places may cause you to misjudge the fault. Sometimes some seemingly simple faults have problems that are difficult to find. Perhaps a simple signal loss can keep you busy for a long time. Maintenance experience is really important.