Motor control circuit

• US 6,013,991 A
• Filed: 12/15/1997
• Issued: 01/11/2000
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Philipp, Chris
• Primary Examiner(s): Masih, Karen
• Application Number:
  US08/990,605
• Time in Patent Office: 757 Days
• Field of Search: 318/139, 318/114, 318/119, 318/280, 388/907, 388/937, 388/931
• US Class Current: 318/139
• CPC Class Codes: A61B 17/1626 Control means; Display units
• CPC Class Codes: A61B 2017/00367 Details of actuation of instruments, e.g. relations between pushing buttons, or the like, and activation of the tool, working tip, or the like
• CPC Class Codes: A61B 2017/00734 battery operated
• CPC Class Codes: H01H 2300/014 Application surgical instrument
• CPC Class Codes: H01H 9/06 Casing of switch constituted by a handle serving a purpose other than the actuation of the switch, e.g. by the handle of a vacuum cleaner
• CPC Class Codes: H02P 25/032 Reciprocating, oscillating or vibrating motors
• CPC Class Codes: H02P 3/06 for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
• CPC Class Codes: H02P 7/03 for controlling the direction of rotation of DC motors
• CPC Class Codes: H03K 17/97 using a magnetic movable element
• CPC Class Codes: Y10S 388/907 Specific control circuit element or device
• CPC Class Codes: Y10S 388/931 Electric generator or magnet as auxiliary load
• CPC Class Codes: Y10S 388/937 Hand tool

Abstract

A motor controller for regulating the application of current to the windings of a motor in order to both control the actuation of the motor rotor and the braking of the rotor. The motor controller includes a speed control circuit regenerating a signal representative of the user-selected speed, a direction controller to signal if the motor is to be driven in the forward, reverse or oscillatory motion and a speed override circuit. There is also a current sensor for monitoring the current drawn by the motor, a brake controller and an energization circuit. The energization circuit regulates the application of a current to the motor to cause the rotation or braking of the rotor. When the motor is to be oscillated, each time the direction controller circuit transitions a FORWARD/REVERSE signal, the speed override circuit causes the energization circuit to momentarily apply energization signals to the motor based on the application of a zero-speed, user-speed signal. During such transitions, the current sensor sends a signal to the energization controller to make it appear that the motor is drawing in a large amount of current. Whenever the motor is operating at a speed higher than the user-speed, the brake controller causes the energization controller to apply braking current to the motor. However, if the rotor is not turning, the brake controller inhibits the assertion of the braking current.

Claims

1. A motor controller for applying energization signals to a motor configured to be rotated in a forward direction and in a reverse direction at variable speeds in response to the application of selected energization signals thereto, said motor control circuit including:

a speed control circuit connected to a user-set speed switch that monitors the state of the speed switch and that generates a USER-SPEED signal representative of a user-set speed for the motor;

a direction control circuit responsive to a user-set direction signal that generates a FORWARD/REVERSE signal, wherein depending on the state of the user-set direction signal, said direction controller generates a FORWARD/REVERSE signal, a FORWARD/REVERSE signal or a signal that oscillates between the FORWARD/REVERSE signal and the FORWARD/REVERSE signal;

an energization circuit for receiving the FORWARD/REVERSE signal from the direction control circuit and said USER-SPEED signal from said speed control circuit and that is connected to a power source and the motor, wherein said energization circuit is configured to apply energization signals from the power source to the motor to cause said motor to rotate at a specific speed in response to said USER-SPEED signal and in a specific direction in response to the application of a FORWARD/REVERSE signal thereto, wherein, when said FORWARD/REVERSE signal is in a FORWARD/REVERSE state, said motor controller causes said motor to rotate in the forward direction and when said FORWARD/REVERSE signal is in a FORWARD/REVERSE state, said motor controller causes said motor to rotate in the reverse direction; and

a speed override circuit connected to said direction circuit, that receives the user-set direction signals and that is connected to said energization circuit for controlling the application of energization signals by said energization circuit to the motor, wherein, when said FORWARD/REVERSE signal transitions between the FORWARD/REVERSE and the FORWARD/REVERSE signal states, said speed override circuit causes said energization circuit for a period of time to apply zero-speed energization signals to the motor equivalent to those applied when a zero-speed USER-SPEED signal is received regardless of the state of the USER-SPEED signal.

2. The motor control circuit of claim 1, wherein:

a braking circuit selectively asserts a BRAKE signal;

said energization circuit receives the BRAKE signal and, in response to receiving the BRAKE signal, applies signals to the motor to cause braking of the motor; and

said speed override circuit is connected to said braking circuit for causing said braking circuit to assert the BRAKE signal when the FORWARD/REVERSE signal transitions between the FORWARD/REVERSE and FORWARD/REVERSE signal states.

3. The motor controller of claim 2, wherein:

said speed override circuit is configured to receive said USER-SPEED signal and to selectively forward said USER-SPEED signal to said energization circuit wherein, when said FORWARD/REVERSE signal transitions between the FORWARD/REVERSE and FORWARD/REVERSE signals states, said speed override circuit pulses said USER-SPEED signal applied to said energization circuit to the zero-speed USER-SPEED signal for the set period of time; and

the USER-SPEED signal is applied to said braking circuit and said braking circuit asserts the BRAKE signal based on the state of said USER-SPEED signal.

4. The motor controller of claim 1, wherein, when the motor is driven in oscillatory rotation and each time the FORWARD/REVERSE signal transitions, said speed override circuit causes said energization circuit to apply zero-speed energization signals to the motor for a fixed period of time.

5. The motor controller of claim 1, wherein said speed override circuit is configured to receive said USER-SPEED signal and to selectively forward said USER-SPEED signal to said energization circuit wherein, when said FORWARD/REVERSE signal transitions between the FORWARD/REVERSE and FORWARD/REVERSE signals states, said speed override circuit pulses said USER-SPEED signal applied to said energization circuit to the zero-speed USER-SPEED signal for the period of time.

6. The motor controller of claim 1, further including:

a motor monitor connected to the motor for monitoring the speed of the motor and configured to generate a MOTOR-SPEED signal based on the speed of the motor; and

wherein said energization circuit receives said MOTOR-SPEED signal and is configured to apply signals to the motor to cause breaking of the motor when said USER-SPEED signal is less than said MOTOR-SPEED signal.

7. The motor controller of claim 6, wherein said motor monitor includes:

at least one sensor unit for monitoring the position of the rotor that generates a sensor signal; and

a tachometer connected to receive the sensor signal that, based on the sensor signal, generates the MOTOR-SPEED signal.

8. The motor controller of claim 1, wherein said energization circuit is configured to apply zero-speed energization signals to the motor by inhibiting the application of energization signals to said motor.

9. The motor controller of claim 8, wherein said energization controller is further configured to assert signals to the motor to cause braking of the motor and, when acting on the zero-speed USER-SPEED signals, asserts signals to the motor to cause the braking of the motor.

10. The motor controller of claim 1, further including:

a current sensor connected to the motor to monitor the current drawn by the motor, said current sensor being configured to generate a variable CUR+ signal representative of the current drawn by said motor wherein said CUR+ signal is based on a variable volts/amp ratio established by said current sensor in response to a received current sensor control signal and, wherein;

said energization circuit is connected to said current sensor for receiving said CUR+ signal and is further configured to apply energization signals to said motor based on the magnitude of said CUR+ signal; and

said speed overide controller is connected to said current sensor for supplying said current sensor control signal thereto and is further configured so that, when the motor is driven in oscillatory rotation and each time said FORWARD/REVERSE signal transitions, to assert said a current sensor control signal to said current sensor to cause said current sensor to momentarily generate said CUR+ signal based on a first volts/amp ratio and to then generate said CUR+ signal based on a second volts/amp ratio that is different from the first volts/amp ratio.

11. The motor controller of claim 10, wherein the first volts/amp ratio established by said current sensor is greater than the second volts/amp ratio established by said current sensor.

12. A motor controller for applying energization signals to a motor, the motor having a magnetized rotor and a plurality of windings that surround the rotor, the windings being configured to be selectively connected to either a power source or ground so as to cause the energization of the windings, said motor controller including:

a motor monitor connected to the motor for generating a MOTOR-SPEED sensor representative of the speed of the rotor;

a speed controller connected to a user-actuated speed switch, said speed controller configured to generate a USER-SPEED signal in response to the actuation of the speed switch that is representative of a user-selected speed for the rotor;

an energization controller connected to the motor for selectively connecting the windings to a power source or ground, to said motor monitor for receiving said MOTOR-SPEED signal, to said speed controller for receiving said USER-SPEED signal, said motor controller being configured to;

connect the windings to the power source or ground in response to said MOTOR-SPEED signal and said USER-SPEED signal so as to actuate the rotor;

to connect the windings to the power source or ground to cause the deceleration of the rotor in response to a BRAKE-ENABLE signal; and

when said MOTOR-SPEED signal and said USER-SPEED signal indicate the rotor is exceeding the user-selected speed by a given amount, to assert a BRAKE-TRIGGER signal; and

a brake controller connected to said motor monitor for receiving said MOTOR-SPEED signal and to said energization controller for receiving said BRAKE-TRIGGER signal, said brake controller being configured to assert said BRAKE-ENABLE signal to said energization controller when said BRAKE-TRIGGER signal is asserted and said MOTOR-SPEED signal indicates the rotor is moving and after said MOTOR-SPEED signal indicates the rotor has stopped moving, to negate the assertion of said BRAKE-ENABLE signal regardless of the state of said BRAKE-TRIGGER signal.

13. The motor controller of claim 12, wherein said energization controller is configured to selectively connect the windings of a DC motor to the power source or ground.

14. The motor controller of claim 12, wherein said brake controller is further connected to said energization controller to inhibit said energization controller from energizing the windings so as to cause the movement of the rotor whenever said BRAKE-TRIGGER signal is asserted.

15. The motor controller of claim 12, wherein said brake controller is configured to cyclically assert said BRAKE-ENABLE signal in an on/off/on/off pattern.

16. The motor controller of claim 15, wherein said brake controller is configured to cyclically assert said BRAKE-ENABLE signal in an on/off/on/off pattern at a frequency that is a function of motor speed.

17. The motor controller of claim 12, wherein said motor monitor includes:

at least one sensor unit for monitoring the position of the rotor that generates a sensor signal; and

a tachometer connected to receive the sensor signal that, based on the sensor signal, generates the MOTOR-SPEED signal.

18. A motor controller for a motor having a magnetized rotor and a plurality of windings that surround the rotor, the windings being configured to be selectively connected to either a power source or ground so as to cause the energization of the windings, said motor controller including:

a motor monitor connected to said motor for generating a MOTOR-SPEED signal representative of the speed of the rotor;

a speed controller connected to a user-actuated speed switch, said speed controller being configured to generate a USER-SPEED signal in response to an actuation of said speed switch that is representative of a user-selected speed for said rotor;

an energization controller connected to the motor for selectively connecting the windings to the power source or ground, to said motor monitor for receiving said MOTOR-SPEED signal, to said speed controller for receiving said USER-SPEED signal, said energization controller being configured to;

connect the windings to the power source or said ground in response to said MOTOR-SPEED signal and said USER-SPEED signal so as to actuate the rotor;

to connect the windings to the power source or ground to cause the deceleration of said rotor in response to a BRAKE-ENABLE signal;

amplify any difference between said USER-SPEED signal and said MOTOR-SPEED signal to produce an ERROR signal; and

compare said ERROR signal to a fixed signal and when said comparison indicates that said MOTOR-SPEED signal exceeds said USER-SPEED signal, to assert a BRAKE-TRIGGER signal; and

a brake controller connected to said energization controller for receiving said BRAKE-TRIGGER signal, said brake controller being configured to assert said BRAKE-ENABLE signal to said motor controller when said BRAKE-TRIGGER signal is asserted.

19. The motor controller of claim 18, wherein said energization controller is configured to selectively connect the windings of a DC motor to the power source or ground.

20. The motor controller of claim 18, wherein said brake controller is further connected to the motor monitor for receiving said MOTOR-SPEED signal and is further configured to cyclically assert said BRAKE-ENABLE signal to said energization controller when said BRAKE-TRIGGER signal is asserted and said MOTOR-SPEED signal indicates said motor rotor is turning and, after said motor rotor has stopped turning, to negate the assertion of said BRAKE-ENABLE signal regardless of the state of said BRAKE-TRIGGER signal.

21. The motor controller of claim 20, wherein said brake controller is further connected to said energization controller to inhibit said energization controller from energizing the windings to cause the actuation of the rotor whenever said BRAKE-TRIGGER signal is asserted.

22. The motor controller of claim 18, wherein said brake controller is further connected to said energization controller to inhibit said energization controller from energizing the windings to cause the actuation of the rotor whenever said BRAKE-TRIGGER signal is asserted.

23. The motor controller of claim 18, wherein said brake controller circuit delays asserting said BRAKE-ENABLE signal to said energization controller until said BRAKE-TRIGGER signal has been asserted for a select period of time.

24. The motor controller of claim 18, wherein said brake controller is configured to cyclically assert said BRAKE-ENABLE signal in an on/off/on/off pattern.

25. The motor controller of claim 24, wherein said brake controller is configured to cyclically assert said BRAKE-ENABLE signal in an on/off/on/off pattern at a frequency that is a function of motor speed.

26. The motor controller of claim 18, wherein said motor monitor includes:

at least one sensor unit for monitoring the position of the rotor that generates a sensor signal; and

a tachometer connected to receive the sensor signal that, based on the sensor signal, generates the MOTOR-SPEED signal.

27. A motor control circuit for a motor configured to be rotated in a forward direction and in a reverse direction at variable speeds in response to the application of selected energization signals thereto, said motor control circuit including:

a current sensor connected to the motor to monitor current drawn by the motor, said current sensor being configured to generate a variable CUR+ signal representative of the current drawn by the motor wherein said CUR+ signal is based on an adjustable volts/amp ratio established by said current sensor based on a current sensor control signal;

a motor controller connected to the motor for applying energization signals thereto, and to said current sensor for receiving said CUR+ signal, said motor controller being configured to apply energization signals to the motor to cause said motor to rotate at a selected speed in response to the application of a speed signal applied thereto and in response to said CUR+ signal and in a specific direction in response to the application of a FORWARD/REVERSE signal thereto, wherein when said FORWARD/REVERSE signal is in a FORWARD/REVERSE state, said motor controller causes the motor to rotate in the forward direction and when said FORWARD/REVERSE signal is in a FORWARD/REVERSE state, said motor controller causes the motor to rotate in the reverse direction; and

a direction controller connected to user-set direction switches for receiving said direction commands and being configured to generate said FORWARD/REVERSE signal for forwarding to said motor controller in response to setting of the direction switches and connected to said current sensor for generating said current sensor control signal, wherein when said direction signals indicate said motor is to be driven in oscillatory rotation, said direction controller cyclically transitions said FORWARD/REVERSE signal between the FORWARD/REVERSE signal state and the FORWARD/REVERSE signal state and, with each said state transition of said FORWARD/REVERSE signal, said direction controller asserts said current sensor control signal to cause said current sensor to momentarily base said CUR+ signal on a first volts/amp ratio and to subsequently base said CUR+ signal on a second volts/amp ratio.

28. The motor control circuit of claim 27, wherein after each said state transition of the FORWARD/REVERSE signal, the first volts/amp ratio upon which said current sensor momentarily basis said CUR+ signal is greater than the second volts/amp ratio upon which said current sensor subsequently basis said CUR+ signal.

29. The motor control circuit of claim 27, wherein said motor controller is configured to selectively connect the windings of a DC motor to the power source or ground.