Browse Prior Art Database

Servo System Using Timers

IP.com Disclosure Number: IPCOM000048952D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 71K

Publishing Venue

IBM

Related People

Burke, EJ: AUTHOR [+2]

Abstract

Described is a servo control method for DC motors which has particular advantage in a paper transport, consisting of two DC servo motors which are tandemly connected to two tractor drive shafts. A one-degree motor-driven encoder emitter wheel 10 and two optical sensor assemblies 11 and 12, adjusted for quadrature operation, are used to obtain position, velocity and direction information for a microprocessor 13. The microprocessor 13 directly controls the DC motor 10 during all phases of carriage operation with appropriate algorithms. The basic control scheme for servo control is to sample the velocity of motor 10 and compare it with a preset input. The drive to the motor 10 is then adjusted by digital or analog circuitry to null any difference between the set input and the actual velocity of the motor.

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 53% of the total text.

Page 1 of 3

Servo System Using Timers

Described is a servo control method for DC motors which has particular advantage in a paper transport, consisting of two DC servo motors which are tandemly connected to two tractor drive shafts. A one-degree motor-driven encoder emitter wheel 10 and two optical sensor assemblies 11 and 12, adjusted for quadrature operation, are used to obtain position, velocity and direction information for a microprocessor 13. The microprocessor 13 directly controls the DC motor 10 during all phases of carriage operation with appropriate algorithms. The basic control scheme for servo control is to sample the velocity of motor 10 and compare it with a preset input. The drive to the motor 10 is then adjusted by digital or analog circuitry to null any difference between the set input and the actual velocity of the motor. Hence, motor velocity is controlled by changing the preset input statically or dynamically.

As seen in Fig. 1, timers T1, T2 and T3 are three distinct programmable timers located within a single module, such as a Motorola 6840. The microprocessor 13 is connected to an appropriate peripheral interface adapter to interface with H drive circuitry 14 through OR gates 15 and 16 and with optical sensors 11 and 12. The quadrature signals from sensors 11 and 12 are used to denote motor direction and actual motor displacement as detected by forward and reverse logic circuitry and an up/down counter 17. In this servo control scheme, only the sensor 11 is used by timers T1, T2 and T3 and microprocessor
13.

Upon receipt of a carriage GO command, microprocessor 13 applies a Drive forward (FWD) signal through OR gate 15 to H drive circuitry 14. Motor 10 then begins to accelerate. Microprocessor 13 then conditions timer T1 with the time period between pulses that depicts the servo speed desired. In addition, microprocessor 13 writes the appropriate time-out value to timers T2 and T3 to servo the motor once the motor 10 reaches the desired velocity. The timers T2 and T3 are programmed by microprocessor 13 to operate in a single-shot mode through toggle circuit 18. The time-out value for T2 and T3 is less than the servo time value because forward...