System for controlling motors for synchronous operation

• US 4,629,956 A
• Filed: 12/13/1985
• Issued: 12/16/1986
• Est. Priority Date: 10/09/1981
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Kawamura, Hideaki, Amemiya, Yoichi, Nozawa, Ryoichiro
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): BERGMANN, SAUL
• Application Number:
  US06/808,811
• Time in Patent Office: 368 Days
• Field of Search: 318/625, 318/606, 318/415, 318/616, 318/636
• US Class Current: 318/625
• CPC Class Codes: G05B 19/253 with speed feedback only
• CPC Class Codes: G05B 19/41 characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path G05B19/25, G05B19/31, G05B19/37, G05B19/39, G05B19/40 take precedence
• CPC Class Codes: G05B 2219/41434 Feedforward FFW
• CPC Class Codes: G05B 2219/42162 Model reference adaptive control MRAC, correction fictive-real error, position
• CPC Class Codes: G05B 2219/50216 Synchronize speed and position of several axis, spindles
• CPC Class Codes: H02P 5/51 Direct ratio control
• CPC Class Codes: H02P 5/56 Speed and position comparison between the motors by electrical means

Abstract

There is disclosed a system for controlling a plurality of motors including a spindle motor of a machine tool to rotate synchronously at command speeds. The system comprises a numerical control unit for generating as positional commands trains of distributed pulses having frequencies corresponding to commanded speeds of rotation respectively for the motors, positional control feedback circuits respectively for the motors for producing speed command outputs from the trains of distributed pulses and detected signals indicative of positions of the motors, and speed control feedback circuits respectively for the motors for controlling the speed of the motors based on the speed command outputs and detected signals indicative of speeds of rotation of the motors.

Claims

1. A system for controlling motors including a reference motor, such that the motors rotate at command speeds in synchronism and have respective rotational positions, said system comprising:

numerical control means, operatively connected to receive commanded speeds of rotation, for generating as positional commands synchronized distributed pulse trains having frequencies corresponding to the commanded speeds of rotation for respective ones of the motors;

positional control feedback circuits, operatively connected to respective ones of said motors and to receive respective ones of said positional command pulse trains, for producing speed command outputs in accordance with respective ones of said positional command pulse trains and said respective rotational positions;

speed control feedback circuits, operatively connected between respective ones of said positional control feedback circuits and respective ones of said motors, for controlling the speed of the motors based on said speed command outputs and said speeds of rotation of the motors;

detector means, operatively connected to said respective ones of the motors, for generating feedback pulses corresponding to the rotational positions of the respective motors each time the respective motors rotate through a predetermined angular interval and for applying these signals to said position control feedback circuits as said respective rotational positions;

simulator circuit means, operatively connected to receive respective ones of said positional command pulse trains, for simulating the characteristics of respective positional and speed control feedback in combination with corresponding ones of said motors, and for generating pulses responsive to said simulations; and

correction circuit means, operatively connected to said corresponding ones of said motors, to said positional and said speed control feedback circuits and to said simulator circuit means, for correcting the rotational positions of the motors in response to differences between the feedback pulses and the pulses generated by said simulator circuit means.

2. A system according to claim 1, said positional control feedback circuits having detectors for generating feedback pulses each time the motors rotate through predetermined angular intervals, further including simulator circuits provided respectively for the motors for being supplied with said trains of distributed pulses and for simulating the characteristics of the servo loops, error registers provided respectively for the motors for storing the differences between the numbers of the feedback pulses and the numbers of pulses generated by said simulator circuits, correction circuits provided respectively for the motors for generating position correcting pulses in response to the contents of said error registers, and synchronism correcting means provided respectively for the motors except said reference motor for producing outputs in response to a ratio of the speed of rotation of the reference motor to the speed of rotation of the other motors and to the content of the error register for the reference motor.

3. A system according to claim 1, said positional control feedback circuits having detectors for generating feedback pulses as said signals indicative of the positions of the motors each time the motors rotate through predtermined angular intervals, further including simulator circuits provided respectively for the motors for being supplied with said trains of distributed pulses and for simulating the characteristics of the servo loops, error registers provided respectively for the motors for storing the differences between the numbers of the feedback pulses and the numbers of pulses generated by said simulator circuits, correction circuits provided respectively for the motors except the reference motor for generating position correcting pulses in response to the contents of said error registers, and synchronism correcting means provided respectively for the motors except said reference motor for producing outputs in response to a ratio of the speed of rotation of the reference motor to the speed of rotation of the other motors and to the content of the error register for the reference motor, to thereby correct the positions of the other motors based on the outputs from said synchronism correcting means.