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

Variable RUN Currents for STEP Motors

IP.com Disclosure Number: IPCOM000035089D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Graham, PA: AUTHOR [+2]

Abstract

The objective of this method of running step motors is to get extra power out of the motor when it is needed, but to not supply extra power when it is not needed. By using two run current levels controlled by software, it is possible to change levels in the middle of a profile or for an entire profile. For example, in certain typewriter applications, more power is needed during the acceleration and ribbon feed stages of some ribbon profiles.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Variable RUN Currents for STEP Motors

The objective of this method of running step motors is to get extra power out of the motor when it is needed, but to not supply extra power when it is not needed. By using two run current levels controlled by software, it is possible to change levels in the middle of a profile or for an entire profile. For example, in certain typewriter applications, more power is needed during the acceleration and ribbon feed stages of some ribbon profiles.

There are integrated circuit stepper motor drivers that will selectively provide 100, 60, 19, or 0% of the current available. By changing the information on the driver control lines, it is possible to change current levels before, during, or after a move. Different currents have been used in the past to unbalance phases for micro-positioning and for dropping current to a detent level after a move has been made to conserve on motor and driver power dissipation. According to the present invention, it is possible to change current anywhere during the cycle of drive and for any desired portion of the cycle.

Several control implementations are possible, depending on the primary means of control of the motor step timing.

If a language-based control system such as Stepper Motor Control System (SMCS), which is described in [*] is used, current control within a profile is as simple as inserting the appropriate output port statements at the appropriate points in the profile. An example SMCS listing is shown in which certain control statements are interposed. This is only illustrative of how the statements can be used to control both point of control and length of control. CCURRENT CONTROL ON PORT BITS 0-1 C 00 - OFF C 01 - DETENT C 10 - NORMAL C 11 - BOOST C SELECT BOOST CURRENT PORT XXXXXX11 C DELAY FOR CURRENT RISE + 0,800 800 uS C ACCELERATE MOTOR TO SPEED + 1, 5000 + 1, 4000 + 2, 2000 + 1, 1000 CBELECT NORMAL CURRENT PORT XXXXXX10 C RUN MOTOR AT CONSTANT VELOCITY REPEAT 100 + 1, 1000 ENDREPEAT C START DECELERATION + 1, 1000 + 1, 3000 C SWITCH TO BOOST CURRENT PORT XXXXXX11 C FINISH DECELERATION + 1, 4000 + 1, 5000 C EXTRA DELAY FOR SETTLE-OUT + 0, 10000 C SELECT DETENT CURRENT PORT XXXXXX01

Most microprocessor-based stepper motor control systems are less sophisticated than SMCS. Rather than utilizing a control language to specify the motor profile, the profile is simply stored as a sequence of delay times, with one delay time per step (or group of steps). The next level of sophistication is to intermix control bytes at appropriate points in the sequence of delays, to mark such points as the constant velocity delay. Typically, a control byt...