Noise on servo controller/drive


Thread Starter


Here, I have some problem with my servo controller/driver units. I am using this servo controller/driver for a few similar machines. This servo motor is used to perform indexing for a tape-and-reel application. A pin-wheel is mounted on the servo motor shaft and this is used to pull the tape. Besides that there is also a home sensor for detecting the tape's holes. When the sensor is triggered, it shows that the position is reached and I.C chip can be placed into the tape's hole. A fix distance is performed before searching for the home sensor. The problem is my servo motor will sometimes search for home sensor in reverse direction after we run the machine for few thousand indexes. Can anybody here help on this? I believe this is caused by electrical noise but when I put a capacitor of 0.1 micro farad between the home sensor signal and home signal ground, it solved only 2 machines out of 4. The other 2 machines was perfectly run for all these while and suddently with this capacitor, the motor reverse its direction again quite often. Please help.
Have you tried to find the source of the noise and suppress that? Usually it is a contact opening an inductive load such as a motor. You can purchase suppressors to put right across the motor. The suppressor is usually a resistor/capacitor series combination. IEEE put out an electrical noise guide book which discusses the many forms of noise and how to cope with them.
The motor looks like a guillotine once in a while. Make sure also that all signals are fed using, adequate cabling, and certainly not subjected to ground loop occurence.
Thanks for your help. I am confusing about why the problem starts occuring again when I include the capacitor onto the usually-works-fine machines whereas another 2 machines which are heavily affected solved by putting capacitor. Have you come across this?
Putting a capacitor on the receiving end of a signal instead of trying to suppress the source of the noise may result in deterioration of the receiving signal. For instance, if you put a capacitor on the signal line from an encoder to a control, it may drastically affect the highest frequency of pulses that can be transmitted. Since a capacitor might also filter out some noise, it may help performance. Sometimes it helps and sometimes it hurts. Do you have any motors, solenoids, clutches, brakes, etc that are opened with a contactor or relay? If so, suppress them. Tom