Unconnected Motor, Drive Control Device Thereof, And Electric Power Steering Device Using Drive Control Device Of Unconnected Motor

• US 20080067960A1
• Filed: 11/24/2005
• Published: 03/20/2008
• Est. Priority Date: 11/24/2004
• Status: Abandoned Application

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Maeda, Masahiro, Miura, Tomohiro, Itakura, Yusuke
• Application Number:
  US11/664,605
• Publication Number:
  US 20080067960A1
• Time in Patent Office: Days
• US Class Current: 318/400.02
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: H02P 21/06 Rotor flux based control involving the use of rotor position or rotor speed sensors

Abstract

A drive control device of an unconnected motor capable of resolving power shortage and increasing motor output without using a boost circuit, and an electric power steering device using the unconnected motor. The drive control device comprises an unconnected motor (12) having a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which armature winding Lu to Lw of a plurality (N number) of phases are independently arranged, a pair of inverter circuits (34a, 34b) individually connected to both ends of each armature winding, and a drive control circuit (15) which drives the pair of inverter circuits (34a, 34b) with a predetermined number (e.g. 2N) of PWM drive control signals.

Claims

1. An unconnected motor, comprising a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged, wherein for each armature winding, at least one of either a back emf waveform or a drive current waveform of is arranged to be a pseudo rectangular wave.

2. The unconnected motor according to claim 1, wherein the pseudo rectangular wave is formed by superimposing a sinusoidal wave with a high harmonic component thereof.

3. The unconnected motor according to claim 1, wherein the pseudo rectangular wave is formed by superimposing a sinusoidal wave signal with any or a plurality of a third, fifth and seventh harmonic component thereof.

4. An unconnected motor, comprising a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged, wherein an Nth harmonic current is arranged to be conductive through each armature winding.

5. A drive control device of an unconnected motor, comprising:

an unconnected motor having a rotor in which permanent magnets are allocated, and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged;

a pair of inverter circuits, individually connected to both ends of each armature winding, which supplies a drive signal which arranges a current waveform of each armature winding to assume a pseudo rectangular wave-shape; and

a drive control circuit for drive-controlling the pair of inverter circuits.

6. The drive control device of an unconnected motor according to claim 5, wherein the drive control circuit is arranged to form control signals for the pair of inverters based on a pseudo rectangular wave-shaped voltage waveform including high harmonic waves of each armature windings of the unconnected motor.

7. The drive control device of an unconnected motor according to claim 5, wherein the drive control circuit is configured to form control signals for the pair of inverters based on a corrected current command value corrected by superimposing a high harmonic component onto a phase current command value for each armature winding of the unconnected motor.

8. The drive control device of an unconnected motor according to claim 5, wherein the drive control device comprises an electrical angle sensing circuit which senses electrical angles of the unconnected motor, wherein the drive control circuit comprises:

a phase current target value computing section having a phase current target value calculation section which respectively outputs a phase current target value on which a high harmonic component has been superimposed for each armature winding of the unconnected motor based on the electrical angle sensed by the electrical angle sensing means, and a phase current command value calculation section which calculates phase current command values for the armature windings of the unconnected motor by multiplying each phase current target value calculated by the phase current target value calculation section by a control current command value;

a motor current sensing circuit which senses a phase current of each armature winding; and

a current control section which controls a drive current for each armature winding based on the phase current command value and the phase current.

9. The drive control device of an unconnected motor according to claim 8, wherein the phase current target value calculation section comprises a storage table which stores a relationship between a phase current command value waveform on which a high harmonic component is superimposed, which has the same waveform as an induced voltage waveform onto which a high harmonic component is superimposed, and an electrical angle of the unconnected motor for armature windings in the unconnected motor, and is arranged to reference the storage table based on an electrical angle sensed by the electrical angle sensing circuit in order to calculate a phase current target value.

10. An electric power steering device, characterized in that a drive device of an unconnected motor according to claim 5 is used.

11. An electric power steering device, comprising:

a steering torque sensing section which senses steering torques;

an unconnected motor having a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged, a pair of inverter circuits individually connected to both ends of each armature winding, which arranges a current waveform of each armature winding to assume a pseudo rectangular wave-shape; and

a drive control circuit for outputting control signals to the pair of inverter based on steering torque sensed by the steering torque sensing section.

12. The electric power steering device according to claim 11, wherein the drive control circuit is arranged to form control signals for the pair of inverters based on a phase current target value of each armature winding of the unconnected motor corresponding to a back emf waveform including a high harmonic component of each armature winding, and on a torque command value based on the steering torque.

13. The electric power steering device according to claim 11, wherein the drive control circuit comprises:

a phase current command value computing section which calculates a phase current command value for each armature winding based on the steering torque sensed value;

a motor current sensing circuit which senses a phase current of each armature winding; and

a current control section which controls a drive current for each armature winding based on the phase current command value and the phase current.

14. The electric power steering device according to claim 13, further comprising an electrical angle sensing circuit which senses electrical angles of the unconnected motor, wherein the phase current command value computing section comprises:

a phase current target value calculation section which calculates a phase current target value corresponding to a back emf including a high harmonic wave, corresponding to each armature winding of the unconnected motor based on the electrical angle; and

a phase current command value calculation section which calculates a phase current command value for each armature winding based on the phase current target value and the steering torque sensed value.

15. The electric power steering device according to claim 11, wherein the drive control circuit is arranged to form a control signal for the pair of inverters by superimposing a high harmonic component on a command voltage for each armature winding, calculated based on a deviation between phase current command value of each armature winding of the unconnected motor calculated based on the steering torque sensed value, and a current sensed value of each armature winding.

16. The electric power steering device according to claim 13, wherein the current control section comprises:

a current controller which calculates, based on a deviation between the phase current command value and the phase current, a phase voltage command value;

a high harmonic wave superposition section which calculates a corrected phase voltage command value by superimposing a high harmonic component on a phase voltage command value calculated by the current controller; and

a pulse width modulation section which generates a control signal, consisting of a pulse width modulation signal, to be supplied to the pair of inverters based on the corrected phase voltage command value from the high harmonic wave superposition section.

17. A drive control device of an unconnected motor, comprising:

an unconnected motor having a rotor in which permanent magnets are allocated, and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged;

a pair of inverter circuits individually connected to both ends of each armature winding; and

a drive control circuit for drive-controlling the pair of inverter circuits, wherein the drive control circuit is arranged to drive the pair of inverter circuits with a predetermined number of PWM drive control signals.

18. The drive control device of an unconnected motor according to claim 17, wherein the drive control circuit is arranged to drive the pair of inverter circuits with 2N number of PWM drive control signals.

19. The drive control device of an unconnected motor according to claim 17, wherein the drive control circuit is arranged to output 2N number of PWM drive control signals to a pair of inverter circuits, wherein N number of PWM drive control signals are supplied to an upper arm of one of the inverter circuits and a lower arm of the other inverter circuit, and the remaining N number of PWM drive control signals are supplied to the lower arm of the former inverter circuit and an upper arm of the latter inverter circuit.

20. The drive control device of an unconnected motor according to claim 17, wherein the drive control circuit is arranged so that a voltage developed between terminals of each armature winding is adjustable.

21. The drive control device of an unconnected motor according to claim 20, wherein the drive control circuit comprises:

a vector control phase command value calculation section which calculates a phase current command value for each armature winding using vector control;

a motor current sensing circuit which senses a phase current of each armature winding; and

a current control section which controls a drive current for each armature winding based on the phase current command value and the phase current.

22. The drive control device of an unconnected motor according to claim 21, wherein the current control section comprises:

a computing control section which calculates a phase voltage command value based on a deviation between the phase current command value and the phase current;

a voltage limiting section which limits a maximum value of the phase voltage command value calculated by the computing control section;

a duty command value calculation section which calculates a duty command value based on the phase voltage command value limited by the voltage limiting section;

a phase conversion section which phase-converts the duty command value calculated by the duty command value calculation section into a number of armature windings to calculate a phase duty command value; and

a drive control signal formation section which forms a predetermined number of PWM drive control signals to be supplied to the pair of inverters based on the phase duty command value outputted from the phase conversion section.

23. The drive control device of an unconnected motor according to claim 21, wherein the drive control signal formation section comprises:

a first computing section which computes a first phase duty command value for one of the inverters based on the phase duty command value outputted from the phase conversion section;

a second computing section which computes a second phase duty command value for the other inverter based on the phase duty command value;

a first PWM circuit which forms a PWM drive control signal for the former inverter based on the first phase duty command value outputted from the first computing section; and

a second PWM circuit which forms a PWM drive control signal for the latter inverter based on the second phase duty command value outputted from the second computing section.

24. The drive control device of an unconnected motor according to claim 23, wherein either the first computing section or the second computing section is arranged to output a phase duty command value with a duty ratio of 50% to a corresponding PWM circuit.

25. The drive control device of an unconnected motor according to claim 23, further comprising a gain setting section which sets a gain for the phase duty command value, wherein the second computing section is arranged to compute the second phase duty command value based on a value obtained by multiplying the phase duty command value outputted from the phase conversion section by the gain.

26. The drive control device of an unconnected motor according to claim 25, wherein the gain setting section is arranged to set a gain based on a q-axis phase voltage command value formed by the current control section.

27. An electric power steering device, characterized in that a drive device of an unconnected motor according to claim 20 is used.

28. An electric power steering device, comprising:

a steering torque sensing section which senses steering torques;

an unconnected motor having a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged, which generates steering assist force for a steering system, a pair of inverter circuits individually connected to both ends of each armature winding; and

a drive control circuit for outputting a predetermined number of drive control signals to the pair of inverter circuits based on steering torque sensed by the steering torque sensing section.

29. An electric power steering device according to claim 28, wherein the drive control circuit is arranged to output 2N number of PWM drive control signals to a pair of inverter circuits, wherein N number of drive control signals are supplied to an upper arm of one of the inverter circuits and a lower arm of the other inverter circuit, and the remaining N number of drive control signals are supplied to the lower arm of the former inverter circuit and an upper arm of the latter inverter circuit.

30. The electric power steering device according to claim 28, wherein the drive control circuit comprises:

a vector control phase command value calculation section which uses vector control to calculate a phase current command value for each armature winding based on the steering torque sensed value;

a motor current sensing circuit which senses a phase current of each armature winding; and

a current control section which controls a drive current for each armature winding from the pair of inverters based on the phase current command value and the phase current.

31. The electric power steering device according to claim 30, wherein the current control section comprises:

a computing control section which calculates a phase voltage command value based on a deviation between the phase current command value and the phase current;

a voltage limiting section which limits a maximum value of the phase voltage command value calculated by the computing control section;

a duty command value calculation section which calculates a duty command value based on the phase voltage command value limited by the voltage limiting circuit;

a phase conversion section which phase-converts the duty command value calculated by the duty command value calculation section into a number of armature windings to calculate a phase duty command value; and

a drive control signal formation section which forms a predetermined number of PWM drive control signals to be supplied to the pair of inverters based on the phase duty command value outputted from the phase conversion section.

32. The electric power steering device according to claim 30, wherein the drive control signal formation section comprises:

a first computing section which computes a first phase duty command value for one inverter based on the phase duty command value outputted from the phase conversion section;

a second computing section which computes a second phase duty command value for the other inverter based on the phase duty command value outputted from the phase conversion section;

a first PWM circuit which forms a PWM drive control signal for the former inverter based on the first phase duty command value outputted from the first computing section; and

a second PWM circuit which forms a PWM drive control signal for the latter inverter based on the second phase duty command value outputted from the second computing section.

33. The electric power steering device according to claim 32, wherein either the first computing section or the second computing section is arranged to output a phase duty command value with a duty ratio of 50% to a corresponding PWM circuit.

34. The electric power steering device according to claim 32, further comprising a gain setting section which sets a gain for the phase duty command value, wherein the second computing section is arranged to compute the second phase duty command value based on a value obtained by multiplying the phase duty command value outputted from the phase conversion section by the gain.

35. The electric power steering device according to claim 32, further comprising a rotational velocity sensing section which senses a rotational velocity of the unconnected motor, wherein the gain setting section is arranged to set the gain based on a steering torque sensed by the steering torque sensing section and a motor rotational velocity sensed by the rotational velocity sensing section.

36. The electric power steering device according to claim 35, wherein the gain setting section comprises a gain calculation table which uses the gain as a parameter to express a relationship between the steering torque and motor rotational velocity.

37. The electric power steering device according to claim 34, wherein the gain setting section is arranged to compute a gain based on a q-axis phase voltage command value formed by the current control section.

38. An electric power steering device, comprising:

an unconnected brushless motor having a rotor in which permanent magnets are allocated, and a stator opposing the rotor, in which a plurality of N-phases of armature windings are independently arranged without interconnection;

steering torque sensing means which senses steering torques inputted to a steering system;

a plurality (N-number) of inverter circuits, to which both ends of each armature winding of the unconnected brushless motor are respectively connected, which individually supplies a drive signal to each armature winding;

current sensing means allocated to either a ground-side or a power-side of each inverter circuit; and

a drive control section which drive-controls each inverter circuit based on winding current sensed by the current sensing means and steering torque sensed by the steering torque sensing means.

39. The electric power steering device according to claim 38, wherein the current sensing means is arranged to sense voltage between terminals of a current sensing resistor inserted to either a ground-side or a power-side of each inverter circuit, and the drive control section has A/D conversion means for performing A/D conversion by sampling voltage between terminals sensed by the current sensing means, wherein a sampling timing of the A/D conversion means is determined based on a duty ratio of a pulse width modulation signal supplied to each armature winding.

40. The electric power steering device according to claim 39, wherein switching of sampling timings of the A/D conversion means is set so that a duty ratio of a pulse width modulation signal has hysteresis characteristics of a predetermined width across a 50% point.

41. The electric power steering device according to claim 38, wherein the current sensing means is arranged to sense voltage between terminals of a current sensing resistor inserted to either a ground-side or a power-side of each inverter circuit, and the drive control section has A/D conversion means for performing A/D conversion by sampling voltage between terminals sensed by the current sensing means, wherein a sampling timing of the A/D conversion means is determined for each armature winding based on a direction and size of a drive current thereof.

42. The electric power steering device according to claim 41, wherein switching of sampling timings of the A/D conversion means in the invention according to claim 41 is set so that a drive current of the armature winding has hysteresis characteristics of a predetermined width across a zero-point.

43. A drive control device of an unconnected motor, comprising:

an unconnected brushless motor having a rotor in which permanent magnets are allocated, and a stator in which a plurality (N number) of phases of armature windings are independently arranged without mutual interconnection to oppose the rotor;

inverter circuits individually connected to both ends of each armature winding, which supply a drive signal to each armature winding;

a drive control section which drive-controls the inverter circuits;

an abnormality detection section which respectively detects current/voltage abnormalities of each armature winding; and

an abnormal-time control section which drives the unconnected brushless motor while suppressing braking force generated by the unconnected brushless motor when a current/voltage abnormality is detected in one of the armature windings by the abnormality detection section.

45. The drive control device of an unconnected motor according to claim 43, wherein the abnormal-time control section is arranged, in the event that a current/voltage abnormality is detected in one of the armature windings by the abnormality detection section, to suspend drive control of a drive element of only an inverter circuit corresponding to the relevant armature winding.

46. The drive control device of an unconnected motor according to claim 43, wherein the abnormality detection section is arranged to detect an abnormality of a drive element which composes an inverter circuit as well as an abnormality of a motor harness between the relevant inverter circuit and an armature winding of the unconnected brushless motor.

47. The drive control device of an unconnected motor according to claim 43, wherein the drive control section is configured to form control signals for the inverter circuits based on a current command value corrected by superimposing a high harmonic component onto a phase current command value for each armature winding of the unconnected motor.

48. An electric power steering device, characterized in that a drive control device of an unconnected motor according to claim 43 is used.

44. A drive control device of an unconnected motor, comprising:

an unconnected brushless motor having a rotor in which permanent magnets are allocated, and a stator in which a plurality (N number) of phases of armature windings are independently arranged without mutual interconnection to oppose the rotor;

inverter circuits individually connected to both ends of each armature winding, which supply a drive signal to each armature winding;

a drive control section which drive-controls the inverter circuits;

an abnormality detection section which respectively detects current/voltage abnormalities of each armature winding;

an abnormal-time control section which drives the unconnected brushless motor while suppressing braking force generated by the unconnected brushless motor when a current/voltage abnormality is detected in one of the armature windings by the abnormality detection section;

a rotational velocity sensing section which senses a rotational velocity of the unconnected brushless motor; and

a motor velocity suppression section which suppresses the rotational velocity of the unconnected brushless motor when the motor rotational velocity sensed by the rotational velocity sensing section is greater than or equal to a set velocity, in the event that a current/voltage abnormality is detected the armature windings by the abnormality detection circuit.

49. An electric power steering device, comprising:

a steering torque sensing section which senses a steering torque;

an unconnected brushless motor, having a rotor in which permanent magnets are allocated and a stator in which a plurality (N number) of phases of armature windings are independently arranged without mutual interconnection to oppose the rotor, which generates steering assist force for a steering system;

inverter circuits individually connected to both ends of each armature winding, which supply a drive signal to each armature winding;

a drive control section which drive-controls the inverter circuits based on a steering torque sensed by the steering torque sensing section;

an abnormality detection section which respectively detects current/voltage abnormalities of each armature winding; and

an abnormal-time control section which drives the unconnected brushless motor while suppressing braking force generated by the unconnected brushless motor when a current/voltage abnormality is sensed in one of the armature windings by the abnormality detection section.

51. The electric power steering device according to claim 49, wherein the drive control section comprises:

a phase current command value computing section which calculates a phase current command value for each armature winding based on the steering torque;

a motor current sensing section which senses a phase current of each armature winding; and

a current control section which controls a drive current for each armature winding based on the phase current command value and the phase current.

52. The electric power steering device according to claim 51, further comprising an electrical angle sensing circuit which senses electrical angles of the unconnected motor, wherein the phase current command value computing section comprises:

a phase current target value calculation section which respectively calculates a phase current target value corresponding to a back emf including a high harmonic component, corresponding to each armature winding of the unconnected motor based on the electrical angle; and

a phase current command value calculation section which calculates a phase current command value for each armature winding based on the phase current command value and the steering torque sensed value.

50. An electric power steering device, comprising:

a steering torque sensing section which senses a steering torque;

an unconnected brushless motor having a rotor in which permanent magnets are allocated and a stator in which a plurality (N number) of phases of armature windings are independently arranged without mutual interconnection to oppose the rotor;

inverter circuits individually connected to both ends of each armature winding, which supply a drive signal to each armature winding;

a drive control section which drive-controls the inverter circuits based on a steering torque sensed by the steering torque sensing section;

an abnormality detection section which respectively senses current/voltage abnormalities of each armature winding;

an abnormal-time control section which drives the unconnected brushless motor while suppressing braking force generated by the unconnected brushless motor when a current/voltage abnormality is sensed in one of the armature windings by the abnormality detection section;

a rotational velocity sensing section which senses a rotational velocity of the unconnected brushless motor; and

a motor velocity suppression section which suppresses the rotational velocity of the unconnected brushless motor when the motor rotational velocity sensed by the rotational velocity sensing section is greater than or equal to a set velocity in the event that a current/voltage abnormality is detected in one of the armature windings by the abnormality detection circuit.

53. An electric power steering device, comprising:

a steering torque sensing section which senses steering torques;

an unconnected brushless motor, having a rotor in which permanent magnets are allocated and a stator opposing the rotor, in which phase coils of a plurality (N number) of phases are independently arranged without mutual interconnection, which generates steering assist force for a steering system;

inverter circuits individually connected to both ends of each phase coil, which supplies a drive signal to each phase coil;

a drive control section which drive-controls the inverter circuit based on a steering torque sensed by the steering torque sensing section; and

an abnormality detection section which detects abnormalities in a conduction control system including the respective phase coils and the inverters based on a voltage between terminals of each phase coil.

54. The electric power steering device according to claim 53, wherein the inverter circuits are respectively connected to both ends of each phase coil.

55. The electric power steering device according to claim 54, wherein the inverter circuits, connected to both ends of each phase coil, are driven at opposite phases to each other.

56. The electric power steering device according to claim 53, wherein the abnormality detection section comprises:

a voltage addition section which adds voltages developed across each phase coil; and

an abnormality judgment section which compares the added voltage added by the voltage addition section with a set voltage range based on a power supply voltage supplied to the conduction control system in order to judge whether a short-to-power/short-to-ground has occurred in the conduction control system.

57. The electric power steering device according to claim 53, wherein the abnormality detection section comprises:

a voltage addition section which adds voltages developed across each phase coil;

a bias circuit which applies a bias voltage of around half of the power supply voltage of the conduction control system at a high impedance to the terminal voltages of both ends of each phase coil; and

an abnormality judgment section which compares the added voltage added by the voltage addition section with a set voltage range based on a power supply voltage supplied to the conduction control system in order to judge whether a short-to-power/short-to-ground has occurred in the conduction control system.

58. The electric power steering device according to claim 53, wherein the abnormality detection section comprises:

a voltage addition section which adds voltages developed across each phase coil;

a bias circuit which applies a bias voltage of around half of the power supply voltage of the conduction control system at a high impedance to the terminal voltage of either one of the ends of each phase coil; and

an abnormality judgment section which compares the added voltage added by the voltage addition section with a set voltage range based on a power supply voltage supplied to the conduction control system in order to judge whether a short-to-power/short-to-ground and a open abnormality has occurred in the conduction control system.

59. The electric power steering device according to claim 56, wherein the abnormality judgment section is arranged to judge that a short-to-power/short-to-ground fault has occurred when a state in which the added voltage added by the voltage addition section deviates from the set voltage range continues for more than a predetermined period of time.

60. The electric power steering device according to claim 59, wherein the abnormality judgment section is arranged to calculate an average value of added voltages added by the voltage addition section, and to judge whether the average value deviates from the set voltage range.

61. The electric power steering device according to claim 56 wherein the abnormality judgment section is arranged to detect a voltage change in the added voltages added by the voltage addition section, and judge that a short-to-power/short-to-ground fault has occurred when a voltage change has occurred.