cnc-club.ru

Код: Выделить всё

    The three most important pins are 'command', 'feedback', and
    'output'.  For a position loop, 'command' and 'feedback' are
    in position units.  For a linear axis, this could be inches,
    mm, metres, or whatever is relavent.  Likewise, for a angular
    axis, it could be degrees, radians, etc.  The units of the
    'output' pin represent the change needed to make the feedback
    match the command.  As such, for a position loop 'Output' is
    a velocity, in inches/sec, mm/sec, degrees/sec, etc.

    Each loop has several other pins as well.  'error' is equal to
    'command' minus 'feedback'.  'enable' is a bit that enables
    the loop.  If 'enable' is false, all integrators are reset,
    and the output is forced to zero.  If 'enable' is true, the
    loop operates normally.

    The PID gains, limits, and other 'tunable' features of the
    loop are implemented as parameters.  These are as follows:

    Pgain	Proportional gain
    Igain	Integral gain
    Dgain	Derivative gain
    bias	Constant offset on output
    FF0		Zeroth order Feedforward gain
    FF1		First order Feedforward gain
    FF2		Second order Feedforward gain
    deadband	Amount of error that will be ignored
    maxerror	Limit on error
    maxerrorI	Limit on error integrator
    maxerrorD	Limit on error differentiator
    maxcmdD	Limit on command differentiator
    maxcmdDD	Limit on command 2nd derivative
    maxoutput	Limit on output value

    All of the limits (max____) are implemented such that if the
    parameter value is zero, there is no limit.

    A number of internal values which may be useful for testing
    and tuning are also available as parameters.  To avoid cluttering
    the parameter list, these are only exported if "debug=1" is
    specified on the insmod command line.

    errorI	Integral of error
    errorD	Derivative of error
    commandD	Derivative of the command
    commandDD	2nd derivative of the command

    The PID loop calculations are as follows (see the code for
    all the nitty gritty details):

    error = command - feedback
    if ( abs(error) < deadband ) then error = 0
    limit error to +/- maxerror
    errorI += error * period
    limit errorI to +/- maxerrorI
    errorD = (error - previouserror) / period
    limit errorD to +/- maxerrorD
    commandD = (command - previouscommand) / period
    limit commandD to +/- maxcmdD
    commandDD = (commandD - previouscommandD) / period
    limit commandDD to +/- maxcmdDD
    output = bias + error * Pgain + errorI * Igain +
             errorD * Dgain + command * FF0 + commandD * FF1 +
             commandDD * FF2
    limit output to +/- maxoutput