Browse Prior Art Database

Universal Stepper Motor Controller

IP.com Disclosure Number: IPCOM000111921D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 146K

Publishing Venue

IBM

Related People

Christiansen, H: AUTHOR

Abstract

For a document scanner device with automatic document separation from a feeder station, automatic document alignment, document feed through the camera station and document distribution into 8 different pockets, a system is designed to independently control four stepper motors. Stepper motor control was not the only task the processor has to perform. Additional tasks are communication to a host system (PS/2*) via a RS232 link, host command interpretation and execution, document position sensor monitoring and providing timing signals for 2 line cameras. The solution reduces microprocessor power dedicated to motor control and to allow multiple motors to be controlled, and makes the control program flexible enough so that it can be reused for other projects requiring stepper motor control.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Universal Stepper Motor Controller

      For a document scanner device with automatic document
separation from a feeder station, automatic document alignment,
document feed through the camera station and document distribution
into 8 different pockets, a system is designed to independently
control four stepper motors.  Stepper motor control was not the only
task the processor has to perform.  Additional tasks are
communication to a host system (PS/2*) via a RS232 link, host command
interpretation and execution, document position sensor monitoring
and providing timing signals for 2 line cameras.  The solution
reduces microprocessor power dedicated to motor control and to allow
multiple motors to be controlled, and makes the control program
flexible enough so that it can be reused for other projects requiring
stepper motor control.

      The High Speed Output (HSO) System and the integrated RS232
interface is the reason to use the 80196KC Microcontroller.  The high
speed outputs can be connected to the clock inputs of up to four SGS
L297 stepper motor drivers.  The 80196KC HSO System utilizes a 16-bit
counter incrementing every microsecond at nominal processor clock
frequency of 16 MHz and a CAM Register holding 8 commands which HSO
Pin to switch to a certain state and the time when to switch the
output pin.  All 8 time values in the CAM are compared to the timer's
actual time within one microsecond by the processor hardware and the
output switches without processor overhead.  Therefore, the switching
is accurate on the microsecond.  A bit of the HSO command indicates
that an interrupt has to occur after this event.  The L297 Stepper
Motor Controller generates four phase drive signals for two-phase
bipolar and four-phase unipolar step motors.  The motor can be driven
in half-step, full-step and wave-drive mode.  An on-chip chopper
permits control of the current in the motor windings.  The current is
controlled by comparing the voltage of current sense resistors with a
reference voltage (V ref).  The controller requires a driver circuit
SGS L298N or equivalent connected to the phase outputs to drive the
motor current.  This driver is not shown in the block diagram.  The
current is controlled binary (low, high) by switching resistor
networks connected to V ref and the current 1 to n outputs of the
74LS574 Register in this application.  An alternate possibility to
control the current is to use the processor's pulse-width modulation
capability to provide V ref via an RC network.  Up to four SGS L297
Stepper Motor Drivers may be connected via two 74LS574 8-Bit
Registers to the microcontroller's address and data bus (memory
mapped I/O).  The processor writes the motor direction, operating
mode and current into these registers.

      A stepper motor must be accelerated / decelerated using a
table.  These tables are individual to the motor characteristics and
the attached torque and inertia.The tables contain 128 values...