Surgical machine and method for controlling and/or regulating a surgical machine

• US 7,362,062 B2
• Filed: 01/03/2007
• Issued: 04/22/2008
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Aesculap AG (B. Braun Holding GmbH & Co. KG)
• Original Assignee: Aesculap AG (B. Braun Holding GmbH & Co. KG)
• Inventors: Schneider, Juergen, Hoegerle, Roland Alois, Konrath, Harald
• Primary Examiner(s): Masih; Karen
• Application Number:
  US11/649,717
• Publication Number:
  US 20070154192A1
• Time in Patent Office: 475 Days
• Field of Search: 318/254, 318/138, 318/439, 318/609, 318/432, 318/434, 388/815, 388/928.1, 388/800, 388/930
• US Class Current: 318/254.1
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

To improve a surgical machine with a sensorless electric motor comprising a rotor and at least two motor windings, and with a motor controller for controlling and/or regulating the electric motor, so that the electric motor is operable with optimum efficiency at low rotational speeds and a starting of the motor in accordance with the purpose, also under load, is enabled, it is proposed that a space vector pulse width modulation (SVPWM) method for controlling and/or regulating the electric motor, in which all motor windings are able to be simultaneously supplied with electric current, be performable with the motor controller. A method for controlling and/or regulating a surgical machine is also proposed.

Claims

1. Surgical machine, comprising:

a sensorless electric motor comprising a rotor and at least two motor windings, and

a motor controller for at least one of controlling and regulating the electric motor,

wherein;

a space vector pulse width modulation (SVPWM) method (A) for said at least one of controlling and regulating the electric motor, in which all motor windings are able to be simultaneously supplied with electric current, is performable with the motor controller;

a rotor position of the electric motor is determinable for said at least one of controlling and regulating the supplying of the at least two motor windings with electric current; and

to determine the rotor position of the electric motor at least one of the at least two motor windings is separable from a power supply of the machine for a time interval t_interrupt, a CEMF (counterelectromotive force) of the at least one of the at least two motor windings is measurable during the time interval t_interrupt, and the position of the rotor is calculatable from the measured CEMF (counterelectromotive force).

2. Machine in accordance with claim 1, wherein the motor controller comprises a control unit and a power unit.

3. Machine in accordance with claim 2, wherein the power unit respectively comprises two power transistors for each of the at least two motor windings.

4. Machine in accordance with claim 1, wherein the electric motor is an electronically commutated brushless DC motor.

5. Machine in accordance with claim 1, wherein all motor windings are simultaneously separable from the power supply of the machine for the time interval t_interrupt.

6. Machine in accordance with claim 1, wherein voltages applied to the at least two motor windings are measurable before or at a start of the time interval t_interrupt or before measuring of the CEMF (counterelectromotive force), and that motor winding at which a lowest voltage is measured is connectable to a predetermined voltage potential.

7. Machine in accordance with claim 6, wherein the predetermined voltage potential is ground.

8. Machine in accordance with claim 1, wherein the CEMF (counterelectromotive force) during the time interval t_interrupt is not measured until after a transient time t_transient.

9. Machine in accordance with claim 6, wherein in order to determine the CEMF (counterelectromotive force), a voltage course is measurable at the motor winding or motor windings not connected to the predetermined voltage potential, and the transient time t_transient corresponds at least to a time t_constant until the voltages applied to the motor winding or motor windings not connected to the predetermined voltage potential are constant or almost constant over a course of time.

10. Machine in accordance with claim 1, wherein a constant value is predetermined for the time interval t_interrupt.

11. Machine in accordance with claim 1, wherein the time interval t_interrupt is alterable.

12. Machine in accordance with claim 11, wherein a duration of the time interval t_interrupt is predeterminable such that during the time interval t_interrupt voltages applied to the motor winding or motor windings not connected to a predetermined voltage potential assume a constant or almost constant voltage value over a course of time.

13. Machine in accordance with claim 9, wherein the time interval t_interrupt is at least one of increasable when the time t_constant is greater than the time interval t_interrupt, and reducible when the time t_constant is less than the time interval t_interrupt.

14. Machine in accordance with claim 9, wherein the time interval t_interrupt is alterable, in particular, increasable or reducible, stepwise per revolution.

15. Machine in accordance with claim 1, wherein:

a specified position of the rotor is comparable with an actual position of the rotor as determined from the CEMF (counter-electromotive force) measurement, and

a field angle of the space vector pulse width modulation (SVPWM) is adjustable in accordance with a difference determined between the specified position and the actual position of the rotor.

16. Machine in accordance with claim 1, wherein the CEMF (counterelectromotive force) is only measurable after a motor current of at least one of the at least two motor windings has dropped to zero.

17. Machine in accordance with claim 1, wherein a mains-independent power supply, is provided for supplying the machine with power.

18. Machine in accordance with claim 17, wherein the mains-independent power supply and the motor controller form a unit, and the unit is detachably connectable to the machine.

19. Machine in accordance with claim 17, wherein the motor controller comprises a connection circuit, which does not connect a processor of the motor controller to the mains-independent power supply until the electric motor is connected to the motor controller.

20. Machine in accordance with claim 1, wherein the electric motor comprises three motor windings.

21. Surgical machine, comprising:

a sensorless electric motor comprising a rotor and at least two motor windings, and

a motor controller for at least one of controlling and regulating the electric motor,

wherein;

a space vector pulse width modulation (SVPWM) method (A) for said at least one of controlling and regulating the electric motor, in which all motor windings are able to be simultaneously supplied with electric current, is performable with the motor controller,

an entire rotational speed range of the surgical machine is divided into at least one lower rotational speed range for low rotational speeds and at least one upper rotational speed range for higher rotational speeds than those in the at least one lower rotational speed range, and

the space vector pulse width modulation (SVPWM) method (A) is performable in the at least one lower rotational speed range.

22. Machine in accordance with claim 21, wherein a second method for said at least one of controlling and regulating the surgical machine, comprising a pulse width modulation (PWM) method (B), is performable in the at least one upper rotational speed range.

23. Machine in accordance with claim 21, wherein a rotational speed limit value (D_limit1, D_limit2) between the at least one lower rotational speed range and the at least one upper rotational speed range is alterable.

24. Machine in accordance with claim 21, wherein a switchover from the space vector pulse width modulation (SVPWM) method (A) to the pulse width modulation (PWM) method (B) takes place at a first switchover rotational speed (D_limit1), and a switchover from the pulse width modulation (PWM) method (B) to the space vector pulse width modulation (SVPWM) method (A) takes place at a second switchover rotational speed (D_limit2).

25. Machine in accordance with claim 21, wherein the switchover from the space vector pulse width modulation (SVPWM) method (A) to the pulse width modulation (PWM) method (B) takes place automatically at a transition from the at least one lower rotational speed range to the at least one upper rotational speed range, and vice versa.

26. Method for at least one of controlling and regulating a surgical machine with a sensorless electric motor comprising a rotor and at least two motor windings, and with a motor controller for said at least one of controlling and regulating the electric motor, comprising:

performing a space vector pulse width modulation (SVPWM) method with the motor controller.

27. Method in accordance with claim 26, wherein the motor controller comprises a control unit and a power unit.

28. Method in accordance with claim 27, wherein the power unit respectively comprises two power transistors for each of the at least two motor windings.

29. Method in accordance with claim 26, wherein the electric motor is a brushless DC motor.

30. Method in accordance with claim 26, wherein a rotor position of the electric motor is determined for said at least one of controlling and regulating the supplying of the at least two motor windings with electric current.

31. Method in accordance with claim 30, wherein to determine the rotor position of the electric motor, at least one of the at least two motor windings is separated from a power supply of the machine for a time interval t_interrupt, a CEMF (counterelectromotive force) of the at least one of the at least two motor windings is measured during the time interval t_interrupt, and the position of the rotor is calculated from the measured CEMF (counterelectromotive force).

32. Method in accordance with claim 31, wherein all motor windings are simultaneously separated from the power supply of the machine for the time interval t_interrupt.

33. Method in accordance with claim 31, wherein voltages applied to the at least two motor windings are measured before or at a start of the time interval t_interrupt or before measuring of the CEMF (counterelectromotive force), and that motor winding at which a lowest voltage is measured is connected to a predetermined voltage potential.

34. Method in accordance with claim 33, wherein the predetermined voltage potential is ground.

35. Method in accordance with claim 31, wherein the CEMF (counter-electromotive force) during the time interval t_interrupt is not measured until after a transient time t_transient.

36. Method in accordance with claim 33, wherein to determine the CEMF (counterelectromotive force), a voltage course is measured at the motor winding or motor windings not connected to the predetermined voltage potential, and the transient time t_transient corresponds at least to a time t_constant until the voltages applied to the motor winding or motor windings not connected to the predetermined voltage potential are constant or almost constant over a course of time.

37. Method in accordance with claim 31, wherein a constant value is predetermined for the time interval t_interrupt.

38. Method in accordance with claim 31, wherein the time interval t_interrupt is altered during operation of the machine.

39. Method in accordance with claim 38, wherein a duration of the time interval t_interrupt is predetermined such that during the time interval t_interrupt voltages applied to the motor winding or motor windings not connected to a predetermined voltage potential assume a constant or almost constant voltage value over a course of time.

40. Method in accordance with claim 36, wherein the time interval t_interrupt is at least one of increased when the time t_constant is greater than the time interval t_interrupt, and reduced when the time t_constant is less than the time interval t_interrupt.

41. Method in accordance with claim 38, wherein the time interval t_interrupt is periodically altered, in particular, increased or reduced, stepwise, in particular, per revolution.

42. Method in accordance with claim 31, wherein after measuring the CEMF (counterelectromotive force), all motor lines are reconnected to the power supply of the machine.

43. Method in accordance with claim 31, wherein:

a specified position of the rotor is compared with an actual position of the rotor as determined from the measurement of the CEMF (counterelectromotive force), and

a field angle of the space vector pulse width modulation (SVPWM) is adjusted in accordance with a difference determined between the specified position and the actual position of the rotor.

44. Method in accordance with claim 31, wherein the CEMF (counter-electromotive force) is only measured after a motor current of at least one of the at least two motor windings has dropped to zero.

45. Method in accordance with claim 26, wherein a mains-independent power supply is used for supplying the machine with power.

46. Method in accordance with claim 45, wherein the mains-independent power supply and the motor controller form a unit, and the unit is connected to the machine before the machine is put into operation.

47. Method in accordance with claim 45, wherein a processor of the motor controller is not connected to the mains-independent power supply until the electric motor is connected to the motor controller.

48. Method in accordance with claim 26, wherein the electric motor comprises three motor windings.

49. Method in accordance with claim 26, wherein:

an entire rotational speed range of the surgical machine is divided into at least one lower rotational speed range for low rotational speeds and at least one upper rotational speed range for higher rotational speeds than those in the at least one lower rotational speed range, and

the space vector pulse width modulation (SVPWM) method is performed in the at least one lower rotational speed range.

50. Method in accordance with claim 49, further comprising:

performing a pulse width modulation (PWM) method for said at least one of controlling and regulating the surgical machine in the at least one upper rotational speed range.

51. Method in accordance with claim 49, wherein a rotational speed limit value between the at least one lower rotational speed range and the at least one upper rotational speed range is altered.

52. Method in accordance with claim 49, wherein a switchover from the space vector pulse width modulation (SVPWM) method to the pulse width modulation (PWM) method takes place at a first switchover rotational speed, and a switchover from the pulse width modulation (PWM) method to the space vector pulse width modulation (SVPWM) method takes place at a second switchover rotational speed.

53. Method in accordance with claim 49, wherein the switchover from the space vector pulse width modulation (SVPWM) method to the pulse width modulation (PWM) method takes place automatically at a transition from the at least one lower rotational speed range to the at least one upper rotational speed range, and vice versa.