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Multispeed Carriage Stepper Motor Control and Addressing System for Wafer Handling

IP.com Disclosure Number: IPCOM000083382D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 26K

Publishing Venue

IBM

Related People

Barnett, JA: AUTHOR [+2]

Abstract

This multispeed carriage stepper motor control and addressing system is used for wafer handling, and has eight different methods of dynamic motor control combined in six modes of operation. The modes of operation depend on the distance to be traveled from one address to the next. The eight methods are grouped as: starts, accelerates, runs, decelerates, and stops so that the motor never looses step with the controlled count addressing system. All addresses are referenced to a point at one end of the carriage route. Closed-loop feedback control of the step rate is used so that the motor only steps as fast as it can follow.

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Multispeed Carriage Stepper Motor Control and Addressing System for Wafer Handling

This multispeed carriage stepper motor control and addressing system is used for wafer handling, and has eight different methods of dynamic motor control combined in six modes of operation. The modes of operation depend on the distance to be traveled from one address to the next. The eight methods are grouped as: starts, accelerates, runs, decelerates, and stops so that the motor never looses step with the controlled count addressing system. All addresses are referenced to a point at one end of the carriage route.

Closed-loop feedback control of the step rate is used so that the motor only steps as fast as it can follow.

The next logical motor sequence is not initiated until either the trailing edge or leading edge (T.E., L.E.) in the encoder window is sensed. This window is judiciously positioned between the pole stable states. The lead angle between the rotating field and armature determines the torque and the speed of the motor, and the ability to keep step.

The methods are selected to fit the dynamic load of the carriage. T.E. and
L.E. alone or with delay 1 or 2, shift the lead angle an amount which is less than the 1.8 degrees step angle, but the pulse insertion or reinsertion changes this angle by one pole position. Only one pulse is added and, of course, deleted so there is no count error.

The circuits to implement the above use an up counter to track the position from the starting point in order to control acceleration, and a down counter to determine the position from the end and control deceleration and stopping.

This stepper motor control system is unique, because it provides controlled soft acceleration and deceleration with automatic load variation compensation for high reliability and low maintenance.

Therefore, smaller stepping motors can be used, and the smaller stopping motors are more efficient. However, lower torque stepping motors will reduce system performance if other factors remain the same.

The control used for a long move of 4096 steps or greater is shown during its velocity profile; where T.E. is the trailing edge and L.E. is the leading edge.

A start pulse begins motion which generates a feedback pulse. The trailing edge of this feedba...