On Thu, Feb 3, 2011 at 2:25 PM, andy pugh <bodge...@gmail.com> wrote:
> On 3 February 2011 19:56, Igor Chudov <ichu...@gmail.com> wrote: > > >> Assuming that the input to the PID is position, then I have a feeling > >> you could get the same effect by using a very large gain on FF1 with a > >> limit (maxcmdD) set to ever so slightly less than the current required > >> to move the table. > > > Since you apparently know a lot about how PID loop is implemented (I just > > looked into pid.c myself after seeing your older message), would you > think > > that adding a friction compensation is relatively straightforward? > > Well, first I would try doing what I suggested with the existing PID > parameters, and see if that helps at all. > > > tmp1 += *(pid->fffgain) * sign( command - feedback ) > > > > where sign( ... ) is a function that returns +1 if its argument is above > 0, > > 0 if its argument is 0, and -1 if argument is < 0. > > x/absf(x) is close to that function, but will have a problem with zero. > ( (x == 0) ? 0 : absf(x) / x ) > should work. > > Andy, I will just do it in a way that is easiest to read. So, you think that adding this to PID is sensible? I can try to code something and use it for a while. The default value of fffgain is obviously 0, so having it available would be backwards compatible. I will, of course, not commit anything. i ------------------------------------------------------------------------------ The modern datacenter depends on network connectivity to access resources and provide services. The best practices for maximizing a physical server's connectivity to a physical network are well understood - see how these rules translate into the virtual world? http://p.sf.net/sfu/oracle-sfdevnlfb _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
