controller 14 for positioning control fig4 a and 4b demonstrate movement of the stitching module along the alpha axis this movement is implemented by an alpha axis drive assembly 40 which tilts yoke assembly 23 and in turn stitching head assembly 8 and stitching horn assembly 10 because of the low speeds power requiremements and positioning accuracy tolerance requirements for movement along this axis the alpha drive utilizes a permanent magnet motor 41 which is controlled by the controller through a typical scr motor control circuit 42 to tilt yoke 23 the shaft of this motor engages a curved sector gear 43 best seen in fig4 b mounted on the back of the yoke at the bottom operating in conjunction with the alpha drive is a swivel axis assembly 44 on which yoke 23 is rotatably mounted through a shaft and bearing assembly so as to allow it to tilt and move along the alpha axis the design of sector gear 43 permits an alpha axis rotation of the stitching head and horn of plus or minus 15 degrees movement along the alpha axis is measured by an alpha axis encoder 45 which transmits this information to controller 14 for tilt control to prevent excessive tilt over travel limit switches 46 are also provided swivel axis assembly 44 has a truss like construction and is mounted on top of a platform shaped base assembly 50 movement of the.