Programmable dual-phase digital motor control with sliding proportionality

• US 5,774,626 A
• Filed: 11/16/1995
• Issued: 06/30/1998
• Est. Priority Date: 11/16/1995
• Status: Expired due to Fees

• Current Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Shenk, Edwin K.
• Primary Examiner(s): Martin, David S.
• Application Number:
  US08/558,737
• Time in Patent Office: 957 Days
• Field of Search: 388/803-815, 388/816-822
• US Class Current: 388/815
• CPC Class Codes: B41J 19/205 Position or speed detectors therefor
• CPC Class Codes: H02P 7/2855 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
• CPC Class Codes: H02P 7/2913 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value

Abstract

A digital motor control is described which is programmable and has dual digital phase with sliding proportionality such that the motor control adaptively alters a speed of a motor by both changing sign and altering motor speed proportionally to an amount of motor speed error.

Claims

1. A digital motor control system for controlling the rotational speed of a motor driven by a drive voltage, said digital motor control system comprising:

sensor means coupled to the motor so as to produce a pulse signal comprising a series of pulses occurring at a frequency representative of the rotational speed of the motor;

a flip-flop in electrical communication with said pulse signal, said flip-flop generating a flip-flop output signal comprising a series of pulses, each said flip-flop pulse having a rising edge corresponding to the rising edge of a sensor means pulse, and a falling edge corresponding to the rising edge of the subsequent sensor means pulse;

reset means in electrical communication with said flip-flop output signal pulses, said reset means generating a first set of reset pulses corresponding to the rising edges of said flip-flop pulses and a second set of reset pulses corresponding to the falling edges of said flip-flop pulses;

oscillator means having a substantially fixed frequency;

first binary counter means in electrical communication with said oscillator means and said first set of reset pulses, for generating a first reference signal corresponding to the rising edges of said flip-flop pulses;

second binary counter means in electrical communication with said oscillator means and said second set of reset pulses, for generating a second reference signal corresponding to the falling edges of said flip-flop pulses;

first comparator means in electrical communication with said flip-flop and said first binary counter for comparing said first reference signal with said pulse signal and transmitting a first adjustment pulse corresponding to the rising edges of said flip-flop pulse;

second comparator means in electrical communication with said flip-flop and said second binary counter for comparing said second reference signal with said pulse signal and transmitting a second adjustment pulse corresponding to the falling edges of said flip-flop pulse and

switch means in electrical communication with said first and second comparator means for altering the drive voltage to the motor in response to said adjustment pulses to control the speed of the motor.

2. The motor control system according to claim 1 wherein said first and second comparator means transmit a go faster signal or a go slower signal indicative of whether said reference signal is faster or slower, respectively, as compared to said pulse signal.

3. The motor control system according to claim 1 wherein said switch means is an analog switch which varies drive voltage proportional to the duration of said adjustment pulses.

4. The motor control system according to claim 3 wherein said analog switch comprises voltage adjustment means which controls the drive voltage in response to an electrical signal.

5. The motor control system according to claim 4 wherein said voltage adjustment means is a transistor and the electrical signal is a current is a current flowing to a base of the transistor.

6. The motor control system according to claim 5 wherein said voltage adjustment means is a series pass transistor.

7. The motor control system according to claim 4 wherein said analog switch further comprises amplifier means for boosting the electrical signal to drive said voltage adjustment means.

8. The motor control system according to claim 4 wherein said analog switch further comprises energy storage means for storing energy sufficient to provide the electrical signal to maintain the speed of the motor in the absence of said adjustment pulses.

9. The motor control system according to claim 8 wherein said energy storage means is a capacitor.

10. The motor control system according to claim 1 wherein said switch means is a digital switch which is normally closed and opens in response to said adjustment pulses for a duration substantially equal to the duration of said adjustment pulses.

11. The motor control system according to claim 10 wherein said digital switch is a transistor alternating between a cutoff mode for discontinuing the drive voltage to the motor thus slowing the motor, and a saturation mode for passing the drive voltage to the motor thus accelerating the speed of the motor.

12. The motor control system according to claim 1 further comprising filter means in electrical communication with said first comparator means for converting said first adjustment pulse from said first comparator means into analog voltage levels proportional to the magnitude of the difference between said pulse signal and said reference signal, and said switch means is an analog switch which varies drive voltage in response to said analog voltage levels.

13. The motor control system according to claim 1 wherein said first comparator means is a digital comparator which adjusts the speed of the motor in response to a predetermined value.