Anders Wallin wrote: >> I believe there are a few people using the Pico Systems brush PWM servo >> amp with >> mesa controller boards. >> > > We are using this combination on our mill. I'm not using any special > boot-up HAL code for the servo amp. > Anders, I believe you are using the BRUSHLESS version of our servo amp, which does not need this trickery. It is provided by the CPLD built into the board. > When dry-testing the servos on the bench (no load attached), this > boot-up sometimes causes the servo > to spin in one direction, causing a following error. > In practice with a load attached and with a tuned PID-loop there are > no problems. I guess the encoder input is noisy > enough, or the PID-settings are such, that the drive gets the required > boot-up dir/pwm anyway, and with the load attached > this never causes a following error on our mill. > Very interesting about the spinning. The brushless amp gets just one pulse of 400 or 800 ns (depending on version) to reset the driver chips, and it does the low side first, and the high side after, so it is impossible to move the motors in that case. So, I think your spinning at power up is from a badly-tuned PID loop making the transition from open-loop to closed-loop.
I used the prototype of the brush servo amps for a while before realizing this problem. Sometimes the motors would be "limp" and then suddenly the servos would "lock" and hold position. So, I had to implement a software fix for it, as the boards were already designed, and the brush version has no smarts, just a few CMOS gate chips. I think I will need to come up with a hal module to implement this. Unfortunately, I can't really test it as I don't have a Mesa 5i20. Jon ------------------------------------------------------------------------------ Protect Your Site and Customers from Malware Attacks Learn about various malware tactics and how to avoid them. Understand malware threats, the impact they can have on your business, and how you can protect your company and customers by using code signing. http://p.sf.net/sfu/oracle-sfdevnl _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
