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Sina, thank you. Do you have any good idea on how to check my encoder transition signals to see if it has illegal transitions or not?

thank you, steve, you are really helpful.

Thank you, Brian, but we don’t have a left or right limit switch on our rail, there is only an index pulse switch, when the carriage hit it, and an index pulse will be sent. Can I do it in this way, I will move the carriage at a fixed length several times and get corresponding counts numbers to see if they are approximate, if not, then we get huge problem with our encoder.

Sina, based on your analysis, I think there’s one thing I can do. I will monitor the phase search error status bit when doing the commutation test next time. If the controller detect an angular value less than 22.5 degrees, that bit will be set. If this is confirmed, what should I do next?

As is stated in the manual, when doing the commutation test, the motor should lock in six distinct positions and move in one direction, but when I do that, I found that after each step, the motor was not locked, I saw it swaying there (move back and forth, gently though), and there is no distinct positions, it will not stop swaying until the commutation test ends , then we got a very uneven counts number. The reason behind it, in my opinion, is the air-film, which provides little friction, what’s more, our marble rail is kind of oblique due to carriage gravity, every time I open the air valve, the carriage is float and tends to stay in one position where I believe is the lowest position along the marble rail. Regarding to the count error problem, I tend to believe there is interference which cause the encoder interpolator making illegal transitions.

Sina, could you please tell me where did you get this acceptable transition table? I have searched in my manuals, no results. Is there any other info were given in that section?

Okay, Brian, I will try again. what do you say about the encoder problems with my air-float rail?

we have two machines,one of them is air-float rail(has encoder problems), another is Parker positioner (parker's linear motor and renishaw's encoder).The one with commutation problems is not tuned yet .With Parker positioner, the commutation test can go smoothly,so does the open loop test, after finish the open loop test, I can Issue $ command to phase the motor and close the servo loop, the only problem with the pisitioner is the weird PID servo loop tuning problem with the same parameters.

Definitely it will cause motor vibration, I dare not do that , aha. I am not going to destroy my machine.

I really appreciate your help, Brian. I am trapped by doing the step move by the strange behavior with the same parameters, I know that onsite help is not accessible and this PID tuning really needs a lot of patience, but we will should first solve that weird problem.

Unfortunately we have, I have observed the pulse with an oscilloscope, it was a square wave.

No moves are allowed before the controller phase the motor successfully, though we can force the motor to move, but it's dangerous, right ? How could I know if my motor has been phased right or not ? One way come into my mind is from the Phase-reference error bit, but there is no guarantee on that, that’s what the manual tells us. You all may be very familiar with the Tool provided by Deltatau Called “Turbo/Umac Setup Pro” , It can help us to configure the controller, Step1: choose you controller type, Accessory options,; Step 2: Set Servo IC frequency ,…. When we come to Step 5, it will allow you to make a move so as to set the commutation parameters Ixx70, Ixx71, In this process , the motor will locked in six distinct positions, after doing that the program will popup a window showing the counts number the controller has detected during the move, if the six counts number is consistent and approximate to your motor and encoder specifications, you will be led to do the open loop test, this test will set the phasing search routine parameters Ixx73 and Ixx74. if I fail the commutation test (let’s call it, what happened when I do this is the six counts number are not even) and force this test to pass by changing the motor parameter (length of pole pair), then change it back in the popup I variable confirmation window, after I finish doing the open loop test and the velocity curve is correct, am I able to issue a $ command to close the servo loop.

Where can I find the definition of the encoder count error flag? Under what circumstances will this bit be set? The corresponding variable is M118 for encoder 1. I know we are in the Deltatau forum, but I still hope there is someone can help. I checked the manuals ,there is only one section relevant to this problem, that is the Encoder SCLK frequency, which is specified by I 7003, now my encoder pulse frequency is 5 MHZ, As is stated in the manual, the Encoder SCLK frequency should be at least four times larger than the pulse frequency. so I set I 7003 to 2556, which means the SCLK frequency is 39.14MHZ, obviously, that is far more enough, but the encoder count error flag M118 still jumps to 1 after I set it to 0 from the Terminal Window, and I can read from the Position Window that the position value for motor 1 is fluctuating, about 10 counts, sometimes larger. Our linear motor is stay afloat; there is an air film beneath. As for the EMI, we use the shielded twisted pair cable for the encoder and the controller, the shield case has been grounded. Analysis for this problem both from hardware and software perspective (mainly Variables setting) will be very welcome. Thank you all!

It's an old machine, since we now have a new controller , we need to replace the old one. The resolution of our encoder is 0.1 microns/count, 1000 counts will make 0.1 mm. It drives me crazy because I found the same parameters added to the PID filter will make different behaviour, sometimes overshoot, sometimes sluggish, i totally don't get it, could anybody give me some help? What should I bear in mind when tuning the servo loop?

thank you, sina. what are the differences if the PMAC is commutating the motor and not closing the current loop? Also, can I use an O command to make a motor move ? For instance , #1 O10, is intended to add 10% voltage of what I169 has specified to motor 1, the amplifier will respond to that voltage and output phase current to the motor windings, thus cause motor move . Is that possible before a phasing reference has been successfully established? I believe so, because controller will not check for phase search error in open loop mode.