why not just use the pid component that is already in linuxcnc?
On 1/24/2017 7:49 AM, EBo wrote:
> On Jan 24 2017 6:29 AM, andy pugh wrote:
>> On 24 January 2017 at 00:06, John Thornton <j...@gnipsel.com> wrote:
>>> if(enable){
>>> float min_velocity = requested_vel
>>> -(requested_vel*(1/velocity_tol));
>>> if(current_vel > 0 && current_vel >=
>>> min_velocity){vel_status = 1;}
>>> else {vel_status = 0;}
>>>
>>> if(torch_on && arc_ok && vel_status){ // allow correction
>>> //if(volts_requested - volts > volts_limit){
>>> // volts = volts_requested - volts_limit;
>>> //}
>>> //else if(volts_requested + volts > volts_limit){
>>> // volts = volts_requested +volts_limit;
>>> //}
>>> if (abs(volts_requested - volts) > voltage_tol) {
>>> offset += (volts_requested - volts) * p_gain;
>>> }
>>> last_z_in = 0;
>>> }
>>
>> The code for an actual PID is pretty simple.
>>
>> static double olderror, iterm
>> if(torch_on && arc_ok && vel_status){ // allow correction
>> error = (volts_requested - volts)
>> dterm = (error - olderrer) * Dgain
>> olderror = error
>> iterm += error * Igain
>> pterm = error * Pgain
>> if (absf(error) > deadband){
>> offset += pterm + iterm + dterm
>> }
>>
>> Is close. You probably need to initialise olderror intelligently, to
>> avoid a single-cycle crazy value.
> I am not completely convinced that the offset calculation in case of
> "absf(error) > deadband" is sufficient. The various terms might still
> give you an unreasonable offset. Might need to clamp that as well, but
> I am not fully sure what that would imply.
>
> EBo --
>
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