Brushless motor

• US 5,563,481 A
• Filed: 05/01/1995
• Issued: 10/08/1996
• Est. Priority Date: 04/13/1992
• Status: Expired due to Term

• Current Assignee: Smith & Nephew Incorporated (Smith & Nephew PLC)
• Original Assignee: Smith and Nephew Endoscopy Inc (Smith & Nephew PLC)
• Inventors: Krause, Kenneth W.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/431,615
• Time in Patent Office: 526 Days
• Field of Search: 318/138, 318/254, 318/439, 318/480, 318/569, 318/594, 318/600, 318/601, 388/937, 388/907.5
• US Class Current: 318/400.09
• CPC Class Codes: A61B 17/32002 with continuously rotating, oscillating or reciprocating cutting instruments
• CPC Class Codes: A61B 2090/031 torque limiting
• CPC Class Codes: G05B 19/232 with speed feedback only
• CPC Class Codes: G05B 2219/35455 Foot pedal
• CPC Class Codes: G05B 2219/36464 Position, teach, store extreme, full open, closed positions
• CPC Class Codes: G05B 2219/37165 Derive pulse from commution position, build into brushless motor
• CPC Class Codes: G05B 2219/41092 References, calibration positions for correction of value position counter
• CPC Class Codes: G05B 2219/41321 Brushless dc motor
• CPC Class Codes: G05B 2219/45118 Endoscopic, laparoscopic manipulator
• CPC Class Codes: G05B 2219/49382 Movement reciprocating
• CPC Class Codes: H02H 7/0822 Integrated protection, motor control centres
• CPC Class Codes: H02H 7/0858 by reversing, cycling or reducing the power supply to the motor
• CPC Class Codes: H02P 6/06 Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H02P 6/24 Arrangements for stopping
• CPC Class Codes: H02P 6/34 Modelling or simulation for control purposes
• CPC Class Codes: H02P 8/30 Holding position when stopped
• CPC Class Codes: Y10S 388/937 Hand tool

Abstract

A wholly digital motor-control system for surgical instruments is disclosed. The signal processor and drive-controller communicate digitally through optical fibers. The system provides fail-safe shutdown in the event that communication ceases for longer than a predetermined time, torque limitation and control of complex movement patterns.

Claims

1. An all-digital control system for a motor having an armature, comprising:

(a) a main digital signal processor for supplying a digital input command signal indicative of a desired motor operation;

(b) a drive controller in digital communication with the main processor, for generating, for each phase of the motor, and in response to the command signal, a digital commutation signal to move the armature, and a digital pulse width modulated signal having a duty cycle established by the input command signal;

(c) switching means in digital communication with the controller, for generating, for each phase, and in response to each commutation signal and each pulse width modulated signal, a digital two-state control signal having an on-state which lasts for said duty cycle;

(d) means in digital communication with the controller, for generating, for each phase, a digital tachometer signal indicative of armature position;

(e) said controller being further operative for processing the tachometer signal, to generate a digital output signal indicative of the actual armature speed or position, and for communicating the digital output signal to the main processor, said controller including a look-up table having bit patterns, each corresponding to a different armature position.

2. The system according to claim 1, wherein the main processor and the drive controller are interconnected by, and digitally communicate through, a parallel bus or serial optical fibers.

3. The system according to claim 2, wherein said pulse width modulated signal for a second phase is superimposed on said pulse width modulated signal for a first phase to provide a compound motion of said motor.

4. The system according to claim 3 further comprising a connector adapted to connect a surgical instrument to said system so that said compound motion is provided by a motor in the surgical instrument.

5. The system according to claim 4 where said motor is a linear motor having fore and aft motion.

6. The system according to claim 5 wherein said instrument is a reciprocating rasp with a first signal driving said rasp with a stroke length of about 250 thousandths of an inch, and a second signal driving said rasp with a stroke length of about 20 to 40 thousandths of an inch.

7. The system according to claim 5 wherein the force in each motion of said instrument is exclusively controlled by the duty cycle of each of said first-phase and second-phase pulse width modulated signals.

8. The system according to claim 1, further comprising a second look-up table for modulating said pulse width modulated signal.

9. The system according to claim 1, wherein the pulse width modulated signal has two states, and wherein the controller includes timer means having a timer output signal whose duration is established by the state of the pulse width modulated signal.

10. The system according to claim 1, wherein the controller includes watchdog timer means having a predetermined watchdog time, and wherein the controller includes shutdown means for ceasing generation of the commutation signals upon elapse of said watchdog time without receipt of the input command signal.

11. The system according to claim 1, wherein the command signal provides oscillatory motion of a rotary motor, said motor further comprising an output for connection to a surgical instrument so that the system inputs said oscillatory motion to said instrument.

12. The system according to claim 11, wherein said surgical instrument is an oscillatory shaver.

13. The system according to claim 12, wherein said shaver oscillates 360°

in each direction at a rate of approximately 120 rpm.

14. The system according to claim 1, wherein said motor is a rotary motor and comprises an output for connection to a surgical instrument, and said system further comprising a control for limiting torque applied to said output so that said torque limiting control regulates the duty cycle of said pulse width modulated signal and excessive torque is not applied to said instrument.

15. The system according to claim 14, wherein said torque limiting control compares motor speed as indicated by said digital tachometer signal with the corresponding duty cycle of the control signal which is proportional to motor torque.

16. An all-digital speed control system for a motor having an armature, comprising:

(a) a main digital signal processor for supplying a digital input speed signal indicative of a desired armature speed;

(b) a drive controller in direct digital communication with the main processor, for generating, for each phase of the motor, and in response to the input speed signal, a digital commutation signal to move the armature, and a digital pulse width modulated signal having a duty cycle established by the input speed signal;

(c) switching means in digital communication with the controller, for generating, for each phase, and in response to each commutation signal and each pulse width modulated signal, a digital two-state speed control signal having an on-state which lasts for said duty cycle;

(d) means in direct digital communication with the controller, for generating, for each phase, a digital tachometer signal indicative of armature position;

(e) said controller being further operative for processing the tachometer signal, to generate a digital output speed signal indicative of the actual armature speed, and for directly digitally communicating the output speed signal to the main processor, said controller including a look-up table having commutation bit patterns, each corresponding to a different armature position.

17. The system according to claim 16, wherein the duty cycle of the pulse width modulated signal lies in an approximate range between 5% and 95%.

18. The system according to claim 16, wherein the pulse width modulated signal is carried on a signal carrier having a frequency of approximately 3.9 kHz.

19. The system according to claim 16, wherein the pulse width modulated signal has two states, and wherein the controller includes timer means having a timer output signal whose duration is established by the state of the pulse width modulated signal.

20. The system according to claim 16, wherein the controller includes watchdog timer means having a predetermined watchdog time, and wherein the controller includes shutdown means for ceasing generation of the commutation signals upon elapse of said watchdog time without receipt of the input speed signal.

21. An all-digital control system for a motor having an armature, comprising:

(a) a main digital signal processor for supplying a digital input command signal indicative of a desired armature speed;

(b) a drive controller in digital communication with the main processor, for generating, for each phase of the motor, and in response to the command signal, a digital commutation signal to move the armature, and a digital pulse width modulated signal having a duty cycle established by the input command signal;

(c) switching means in digital communication with the controller, for generating, for each phase, and in response to each commutation signal and each pulse width modulated signal, a digital two-state control signal having an on-state which lasts for said duty cycle;

(d) means in digital communication with the controller, for generating, for each phase, a digital tachometer signal indicative of armature position;

(e) said controller being further operative for processing the tachometer signal, to generate digital output signal indicative of the actual armature speed, and for communicating the digital output signal to the main processor; and

(f) a look-up table in the main processor adapted to provide a signal to said drive controller in response to said digital output signal indicative of the actual armature speed, that indicates a voltage or electrical drive energy needed to produce said desired armature speed.

22. The system according to claim 21 wherein signals between said processor and said controller are optical.

23. The system of claim 21, wherein said controller directly digitally communicates the output speed signal to the main processor.

24. The system of claim 23, wherein signals between said processor and said controller are optical.