function as shown in fig9 the gain k is determined from the transfer function for a required low pass filter time constant u03c4 l and a desired damping ration u03be the root locus method for graphically representing pole movement in the complex plane is useful for visualizing the algebra the basic rule requires open loop poles to move towards open loop zeroes as k changes from zero to infinity excess poles move toward radially spaced asymptotes the corresponding root locus diagram is show in fig1 a reasonable upper limit on gain k is obtained by placing complex poles at the optimal damping ratio u03be 0 707 represented as 45 u00b0 lines critically damped poles u03be 1 0 set a reasonable lower limit on k the single pole is interpreted as the decay following error u03c4 e while the pole pair indicates the dynamic response system u03c4 s approximate algebraic relationships between system parameters and pole locations are given below for u03c4 i gt gt u03c4 l equ4 exact relationships between system parameters and pole locations are given as for equ5 the above described feed forward li controller was implemented on the system 10 of fig1 as mentioned the li controller measures the interaction between the sewing machine and the fabric being sewn and adjusts the feed mechanism such that the desired output is obtained in operation an exemplary easing profile was used in the form shown in fig1 a 11b and 11c the profile is entered into the controller 70 by specifying the desired offsets at certain locations along the desired.