Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Single Microcomputer Control of Simultaneously Active Stepper Motors

IP.com Disclosure Number: IPCOM000048823D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 4 page(s) / 89K

Publishing Venue

IBM

Related People

Scheibl, FJ: AUTHOR

Abstract

There exists a class of machines (such as wheel printers and industrial robots) that accomplish their function by simultaneously activating stepper motors to produce the choreographed motion of separate mechanisms. Disclosed is a system whereby multiple stepper motors may be sequenced concurrently using a single microprocessor with a single timer.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 40% of the total text.

Page 1 of 4

Single Microcomputer Control of Simultaneously Active Stepper Motors

There exists a class of machines (such as wheel printers and industrial robots) that accomplish their function by simultaneously activating stepper motors to produce the choreographed motion of separate mechanisms. Disclosed is a system whereby multiple stepper motors may be sequenced concurrently using a single microprocessor with a single timer.

An example of a machine having multiple stepping motors is shown in Fig. 1. This wheel printer executes a print-character operation by running stepper motor 101 to drive belt 102 which causes print mechanism 103 to escape to the desired print position 104. Concurrent with this motion, stepper motor 105 activates mechanism 106 which advances the ribbon 107 to the next print position. Also concurrent with the above motion, stepper motor 108 rotates print wheel 109 until the desired character petal 110 is positioned in front of the hammer 111. When the above motions are complete, the hammer 111 is activated to cause the desired character petal 110 to strike the ribbon 107 which prints a character on the paper 113.

The motions described in the above example must occur at the same time to maximize print speed.

The actual control of the motor comprises activating selected windings in a precisely timed sequence so as to maximize speed yet not "break phase" (get out of step with the driving waveform) or cause excessive ringing or overshoot to occur. This is typically accomplished with a microcomputer 200, as shown in Fig. 2, using a three-phase stepping motor 201 as an example.

The three-phase windings in motor 201 are activated by an analog drive circuit 202 controlled by an output port 203 from the microprocessor 205. When one of the three output ports that control a phase is active, current is made to flow in the corresponding motor phase windings. Stored in the microprocessor's ROS (read-only storage) program store 204 is a table of values called the motor "profile" which defines the timing of the changes in the phase control outputs which cause the motor 201 to step. The complexity of the profiles is determined by the motor's characteristics and operating environment (load torque, friction, inertial load, etc.) as well as desired operating speed, and could be quite complex.

The stored program which controls the operation is illustrated by the flowchart in Fig. 3, and comprises generally writing the next phase pattern to the output port, getting the next delay value from the stored profile, waiting until the delay is finished, and repeating until the desired number of steps have been taken.

In order to reduce costs, a single-chip microcomputer 200 may be employed to perform this function, and would replace everything within the dotted lines in Fig. 2. In a multiple motor configuration (such as the wheel printer or a robot) where the motor profiles are likely to be considerably different from one another, a separate microcom...