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High Precision, High Velocity, Rectangular Coordinate Positioner

IP.com Disclosure Number: IPCOM000047808D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Barnett, JA: AUTHOR [+2]

Abstract

Linear stepping motors used in X-Y positioning systems permit high throughput by providing linear velocities in excess of 20 in/sec. Unfortunately, the step size (.0333 in/step or 30 steps/inch) prevents fine positional displacement using conventional drive involving full or half step winding sequencing. State-of-the-art mini/micro stepping techniques allow positioning within the cardinal step of any stepper motor. However, these techniques involve difference current level control of the motor windings. Resulting positional accuracy is influenced greatly by individual motor parameters and system friction. This problem is solved with the use of a second or vernier positioning device which is fixed to the primary X-Y positioning system. This device consists of a rotary stepper motor driving a high accuracy leadscrew.

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High Precision, High Velocity, Rectangular Coordinate Positioner

Linear stepping motors used in X-Y positioning systems permit high throughput by providing linear velocities in excess of 20 in/sec. Unfortunately, the step size
(.0333 in/step or 30 steps/inch) prevents fine positional displacement using conventional drive involving full or half step winding sequencing. State-of-the-art mini/micro stepping techniques allow positioning within the cardinal step of any stepper motor. However, these techniques involve difference current level control of the motor windings. Resulting positional accuracy is influenced greatly by individual motor parameters and system friction. This problem is solved with the use of a second or vernier positioning device which is fixed to the primary X- Y positioning system. This device consists of a rotary stepper motor driving a high accuracy leadscrew. The rectangular coordinate positioning system utilizes such a device for each of the X and Y axes. This allows positioning of the X/Y axis to .001 inch per motor step. Finer resolution is achievable through proper selection motor step angle and mechanical hardware, as seen in the figure. In operation, the primary X/Y-axis positioning system, the linear stepping motor, is driven to a position relating to its cardinal step. The vernier X/Y axis is driven to a position relating to its cardinal step, which is within the cardinal step position of the primary X/Y-axis positioning system. Maxim...