Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
  • H02P6/10—Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
  • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
  • B60L15/02—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles characterised by the form of the current used in the control circuit
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
  • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
  • B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
  • H02P23/04—Arrangements or methods for the control of AC motors characterised by a control method other than vector control specially adapted for damping motor oscillations, e.g. for reducing hunting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
  • B60L2210/00—Converter types
  • B60L2210/10—DC to DC converters
  • B60L2210/14—Boost converters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
  • B60L2210/00—Converter types
  • B60L2210/20—AC to AC converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/62—Hybrid vehicles
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/64—Electric machine technologies in electromobility
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/72—Electric energy management in electromobility

Definitions

• the present invention relates to a motor drive device and a control method thereof. Particularly, the present invention relates to a motor drive device with a damping control function of output torque, and a method of controlling the motor drive device Background Art
• a hybrid vehicle includes, in addition to a conventional engine, a DC (direct current) power source, an inverter, and a motor driven by the inverter as the power source.
• a DC (direct current) power source In addition to achieving the power source by driving the engine, the DC voltage from the DC power source is converted into AC (alternating current) voltage by the inverter, and the converted AC voltage is used to rotate the motor to achieve power
• An electric vehicle includes a DC power source, an inverter, and a motor driven by the inverter as the power source
• a motor drive device incorporated in such a hybrid vehicle or electric vehicle employs the damping control technique to suppress vehicle vibration caused by deviation in torque control by accurately matching the output torque of the motor with the torque command (for example, refer to Japanese Patent Laying-Open No. 2005- 198402)
• the torque command applied to the motor drive device is an addition of damping torque that is generated based on the waviness component of the motor revolutions or the like with the output torque primarily required of the motor
• some types of hybrid vehicles are configured to allow adjustment of the applied voltage for motor drive (hereinafter, also referred to as "motor drive voltage") according to the motor operating state (the number of revolutions, torque, and the like) by incorporating a level conversion function of DC voltage applied to the motor drive device that controls the motor drive.
• motor drive voltage the applied voltage for motor drive
• the battery qualified as a DC voltage source can be reduced in size. Further, power loss in association with the increased voltage can be reduced to allow higher efficiency of the motor.
• Japanese Patent Laying-Open No. 10-066383 discloses a configuration in which the motor for vehicle running is controlled.
• the DC voltage from a battery is boosted by a voltage-up converter to generate a motor drive voltage, which is converted into AC voltage by the inverter to be used for motor drive control.
• the target value of the motor drive voltage i.e. the voltage command of the voltage-up converter, is determined based on the motor revolution and the torque command.
• a torque command is used to determine the voltage command of the voltage-up converter during execution of damping control set forth above.
• the torque command in damping control corresponds to the primarily required torque added with the damping torque, and has a varying waveform reflecting the waviness component of the number of revolutions. Therefore, the voltage command determined based on such a torque command will vary, likewise the torque command. Such variation in voltage command will cause the voltage-up converter to frequently repeat a voltage-up operation and a voltage-down operation. As a result, the power loss occurring at the voltage-up converter increases to degrade the system efficiency of the motor drive device.
• a smoothing capacitor must be provided at the output side of the voltage-up converter to stabilize the motor drive voltage. Therefore, variation in the voltage command will cause a change in the holding voltage of the smoothing capacitor, such that the stored power will also vary. If a voltage-up operation and voltage-down operation are frequently repeated according to variation in the voltage command, the voltage-up converter is subject to variation of the stored power of the smoothing capacitor in addition to the consumed/generated power of AC motor Ml . As a result, a relatively large current will flow through the voltage-up converter. If this current becomes excessive, the switching element constituting the voltage-up converter may be damaged. Further, increase of the current flowing through the voltage-up converter will increase power loss, and may become the cause of preventing high efficiency of the motor. Disclosure of the Invention
• an object of the present invention is to provide a motor drive device that can execute damping control without increasing the current flowing through a voltage-up converter, and a control method of the motor drive device.
• a motor drive device includes a drive circuit driving a motor, a motor drive control circuit controlling the drive circuit such that output torque of the motor follows a first torque command, a voltage converter for voltage conversion of power from a power source for input to the drive circuit, and a voltage conversion control circuit controlling voltage conversion such that an output voltage matches a voltage command.
• the motor drive control circuit includes a first damping control unit generating damping torque to suppress pulsation of the output torque of the motor with predetermined torque set in advance as an upper limit value, and adding the generated damping torque to target drive torque as the first torque command.
• the voltage conversion control circuit determines the voltage command based on an upper limit value of the damping torque to control the voltage conversion according to the voltage command.
• the torque command employed in the determination of the voltage command at the voltage conversion control unit is set based on damping torque fixed at the upper limit value of the damping torque in the motor drive device set forth above, variation in the voltage command reflecting the damping torque can be suppressed Accordingly, increase of the current flowing through the voltage converter can be suppressed to allow reduction in power loss. Further, since the voltage command constantly meets the motor drive voltage required to output the torque specified by the first torque command, damping control can be conducted stably
• the motor drive device further includes a charge storage unit arranged between the voltage converter and the drive circuit to smooth the converted DC voltage for input to the drive circuit.
• the voltage conversion control circuit includes a second damping control unit adding the upper limit value of the damping torque to the target drive torque as a second torque command, and a voltage conversion control unit determining the voltage command according to the second torque command and a revolution count of the motor to control voltage conversion based on the voltage command.
• the second damping control unit sets the upper limit value of the damping torque such that it becomes lower as the revolution count of the motor becomes higher.
• the voltage command in a high motor revolution mode is set to a relatively low voltage than when the upper limit value of the damping torque is fixed. Accordingly, increase of the current passing through the voltage converter can be suppressed to allow protection of the voltage converter and reduction in power loss. Further, the power source can be protected from charge and discharge caused by excessive power since the input/output limit of the power source can be held in abidance even in the high motor revolution region.
• the second damping control unit includes a damping control instruction unit instructing one of execution and suspension of damping control according to a temporal rate of change of the target drive torque and the revolution count of the motor.
• the second damping control unit takes the target drive torque directly as the second torque command in response to a suspension instruction of damping control.
• the damping control instruction unit instructs only execution of damping control when the input/output power limit value of the power source is lower than a predetermined threshold value.
• the motor drive device further includes a power source temperature detection unit detecting the temperature of the power source.
• the damping control instruction unit determines that the input/output power limit value of the power source is lower than the predetermined threshold value when the detected temperature of the power source is lower than a predetermined temperature.
• a motor drive device includes a drive circuit driving a motor that generates drive torque of a vehicle, a motor drive control circuit controlling the drive circuit such that output torque of the motor follows a first torque command, a voltage converter for voltage conversion of power from a power source for input to the drive circuit, and a voltage conversion control circuit controlling voltage conversion such that an output voltage matches a voltage command.
• the motor drive control circuit includes a first damping control unit generating damping torque to suppress pulsation of the output torque of the motor with predetermined torque set in advance as an upper limit value, and adding the generated damping torque to target drive torque as the first torque command.
• the voltage conversion control circuit includes a second damping control unit setting a second torque command based on an upper limit value of the damping torque, and a voltage conversion control unit determining the voltage command according to the second torque command to control voltage conversion based on the voltage command.
• the second damping control unit sets the upper limit value of the damping torque variable according to the state of the vehicle.
• the second damping control unit sets the upper limit value of the damping torque such that it becomes lower as the vehicle speed becomes higher.
• the second damping control unit sets the upper limit value of the damping torque variable according to the temporal rate of change of the target drive torque.
• the second damping control unit sets the upper limit value of the damping torque such that it becomes higher as the temporal rate of change of the target drive torque becomes higher.
• the damping torque can be always set to a level suitable for suppressing torque pulsation since the magnitude of torque pulsation depends upon the temporal, rate of change of the target drive torque. Therefore, power loss of the voltage converter and motor loss can be reduced while suppressing vehicle vibration.
• the vehicle includes an internal combustion engine generating drive torque of a vehicle by a drive source independent of the motor. The second damping control unit sets the upper limit value of the damping torque such that it becomes relatively high when the internal combustion engine is started or stopped.
• damping control can be conducted effectively when the internal combustion engine is started or stopped at which time the torque pulsation is relatively large.
• the second damping control unit increases the upper limit value of the damping torque at a first rate of change set to avoid exceeding a time constant of the voltage converter in a damping torque upper limit value increase mode, and decreases the upper limit value of the damping torque by a second rate of change that is lower than the first rate of change in a damping torque upper limit value decrease mode.
• the second damping control unit includes a damping control instruction unit instructing one of execution and suspension of damping control according to a temporal rate of change of the target drive torque and the revolution count of the motor, a feedback control unit feedback-controlling the second torque command such that a deviation between the revolution count of the motor and a target revolution count becomes zero when damping control is executed, and a feedback gain adjustment unit adjusting the gain that is to be multiplied by the deviation in feedback control according to the vehicle state, and gradually decreasing the gain towards substantially zero in response to a suspension instruction of damping control.
• a damping control instruction unit instructing one of execution and suspension of damping control according to a temporal rate of change of the target drive torque and the revolution count of the motor
• a feedback control unit feedback-controlling the second torque command such that a deviation between the revolution count of the motor and a target revolution count becomes zero when damping control is executed
• a feedback gain adjustment unit adjusting the gain that is to be multiplied by the deviation in feedback control according to the vehicle state, and gradually decreasing the
• the second damping control unit decreases the upper limit value of the damping torque at a rate of change lower than the rate of change of gain in response to a suspension instruction of damping control, and sets the upper limit value of the damping control to substantially zero in response to the gain arriving at substantially zero
• a control method of a motor drive device including a drive circuit driving a motor, and a voltage converter for voltage conversion of power from a power source for input to the drive circuit includes: a motor drive control step of controlling the drive circuit such that output torque of the motor follows a first torque command, and a voltage conversion control step of controlling voltage conversion such that an output voltage matches a voltage command
• the motor drive control step includes a first damping control step of generating damping torque to suppress pulsation of output torque of the motor with predetermined torque set in advance as an upper limit value, and adding the generated damping torque to target drive torque as the first torque command.
• the voltage conversion control step determines the voltage command based on the upper limit value of the damping torque to control voltage conversion according to the voltage command. Since variation in the voltage command reflecting damping torque can be suppressed by the control method of a motor drive device set forth above, increase of current passing through the voltage converter can be suppressed to reduce power loss. Further, since the voltage command always meets the motor drive voltage required to output torque specified by the first torque command, damping control can be conducted stably.
• the motor drive device further includes a charge storage unit arranged between the voltage converter and the drive circuit to smooth converted DC voltage for input to the drive circuit.
• the voltage conversion control step includes a second damping control step of adding the upper limit value of damping torque to target damping torque as a second torque command, and a voltage conversion control step of determining the voltage command according to the second torque command and a revolution count of the motor to control voltage conversion according to the voltage command.
• the second damping control step sets the upper limit value of damping torque such that it becomes lower as the revolution count of the motor becomes higher. According to the control method of a motor drive device set forth above, increase of current passing through the voltage converter can be suppressed to allow protection of the voltage converter and reduction in power loss. Further, the input/output limit of the power source can be held in abidance even in the high motor revolution region, allowing protection of the power source from charge and discharge caused by excessive power.
• the second damping control step includes a damping control instruction step of instructing one of execution and suspension of damping control according to a temporal rate of change of the target drive torque and revolution count of the motor.
• the target drive torque is directly set as the second torque command.
• the damping control instruction step instructs only execution of damping control when an input/output power limit value of the power source is lower than a predetermined threshold value.
• control method further includes a power source temperature detection step of detecting the temperature of the power source.
• the damping control instruction step determines that the input/output power limit value of the power source is lower than a predetermined threshold value when the detected temperature of the power source is lower than a predetermined temperature.
• a control method of a motor drive device including a drive circuit driving a motor that generates drive torque of a vehicle, and a voltage converter for voltage conversion of power from a power source for input to the drive circuit includes: a motor drive control step of controlling the drive circuit such that output torque of the motor follows a first torque command, and a voltage conversion control step of controlling voltage conversion such that an output voltage matches the voltage command.
• the motor drive control step includes a first damping control step of generating damping torque to suppress pulsation of output torque of the motor with predetermined torque set in advance as an upper limit value, and adding the generated damping torque to a target drive torque as a first torque command.
• the voltage conversion control step includes a second damping control step of setting a second torque command based on the upper limit value of the damping torque, and a voltage conversion control step of determining the voltage command according to the second torque command, and controlling voltage conversion according to the voltage command.
• the second damping control step set the upper limit value of the damping torque variable according to the vehicle state.
• the second damping control step sets the upper limit value of the damping torque such that it becomes lower as the vehicle speed becomes higher.
• the second damping control step sets the upper limit value of the damping torque variable according to the temporal rate of change of the target drive torque. Further preferably, the second damping control step sets the upper limit value of the damping torque such that it becomes higher as the temporal rate of change of the target drive torque becomes higher.
• the damping torque can always be set to a level suitable for suppressing torque pulsation. Accordingly, power loss of the voltage converter and motor loss can be reduced while suppressing vehicle vibration.
• the vehicle includes an internal combustion engine generating drive torque of a vehicle by a drive source independent of the motor.
• the second damping control step sets the upper limit value of the damping torque such that it becomes relatively high when the internal combustion engine is started or stopped.
• damping control can be conducted effectively when the internal combustion engine is started or stopped at which time the torque pulsation becomes relatively larger.
• the second damping control step increases the upper limit value of the damping torque at a first rate of change set to avoid exceeding the time constant of the voltage converter when in a damping torque upper limit value increase mode, and decreases the upper limit value of the damping torque at a second rate of change that is lower than the first rate of change in a damping torque upper limit value decrease mode.
• damping control response can be improved, and discontinuity in output torque caused by a sudden reduction in damping torque can be prevented.
• the second damping control step includes a damping control instruction step of instructing one of execution and suspension of damping control according to a temporal rate of change of the target drive torque and a revolution count of the motor, a feedback control step of feedback-controlling the second torque command such that a deviation between the revolution count of the motor and a target revolution count becomes zero in a damping control execution mode, and a feedback gain adjustment step of adjusting gain to be multiplied by the deviation in feedback control according to a vehicle state, and gradually decreasing the gain towards substantially zero in response to a suspension instruction of damping control
• the second damping control step decreases the upper limit value of the damping torque by a rate of change lower than the rate of change of gain in response to a suspension instruction of damping control, and sets the upper limit value of damping torque to substantially zero in response to the gain arriving at substantially zero.
• the torque command employed in determining the voltage command of the voltage converter is set based on the damping torque fixed at the upper limit value of the damping torque. Accordingly, increase of the current passing through the voltage converter can be suppressed since variation in the voltage command reflecting the damping torque can be suppressed.
• Fig. 1 is a schematic block diagram of a motor drive device according to a first embodiment of the present invention.
• Fig. 2 is a functional block diagram of a control device of Fig. 1.
• Fig. 3 is a functional block diagram of an inverter control circuit of Fig. 2.
• Fig. 4 is a functional block diagram of a converter control circuit of Fig. 2.
• Fig. 5 is a functional block diagram of a converter damping control unit of Fig. 4.
• Fig. 6 is a diagram to describe the relationship between a torque command and a voltage command.
• Fig. 7 is a flow chart to describe voltage conversion control according to the first embodiment of the present invention.
• Fig 8 represents the relationship between a damping torque upper limit value and motor revolution count.
• Fig. 9 is a flow chart to describe voltage conversion control according to a second embodiment of the present invention.
• Fig. 10 is a diagram representing the relationship between the speed of a vehicle in which a motor drive device is incorporated and a damping torque upper limit value.
• Fig. 11 is a diagram to describe a voltage command according to a third embodiment of the present invention.
• Fig. 12 is a flow chart to describe voltage conversion control according to the third embodiment of the present invention.
• Fig. 13 is a diagram to describe a voltage command according to a modification of the third embodiment of the present invention.
• Fig. 14 is a flow chart to describe voltage conversion control according to a modification of the third embodiment of the present invention.
• Fig. 15 is a functional block diagram of a converter damping control unit in a motor drive device according to a fourth embodiment of the present invention.
• Fig. 16 represents the relationship between a vehicle state and a damping torque index.
• Fig. 17 represents the relationship between a damping torque index and damping torque.
• Fig. 18 is a timing chart of a damping control flag, damping torque index, and damping torque.
• Fig. 19 is a flow chart to describe voltage conversion control according to the fourth embodiment of the present invention.
• Fig. 20 is a timing chart of a damping control flag, damping torque index, and damping torque
• Fig. 21 is a timing chart of a damping control flag, damping torque index, feedback gain coefficient, and damping torque. Best Modes for Carrying Out the Invention
• Fig. 1 is a schematic block diagram of a motor drive device according to a first embodiment of the present invention.
• a motor drive device 100 includes a DC power source B, voltage sensors 10 and 13, system relays SRl and SR2, capacitors C land C2, a voltage- up converter 12, an inverter 14, a current sensor 24, a rotation position sensor 26, and a control device 30.
• An AC motor Ml is a drive motor to generate torque for driving the driving wheel of a hybrid vehicle or electric vehicle.
• AC motor Ml is adapted to function as a power generator driven by an engine, and to operate as an electric motor for the engine to start, for example, the engine.
• Voltage-up converter 12 includes a reactor Ll, IGBT (Insulated Gate Bipolar Transistor) elements Ql and Q2, and diodes Dl and D2.
• IGBT Insulated Gate Bipolar Transistor
• Reactor Ll has one end connected to the power supply line of battery B, and the other end connected to the intermediate point between IGBT element Ql and IGBT element Q2, i e. between the emitter of IGBT element Ql and the collector of IGBT element Q2.
• IGBT elements Ql and Q2 are connected in series between the power supply line and earth line.
• the collector of IGBT element Ql is connected to the power supply line
• the emitter of IGBT element Q2 is connected to the earth line.
• diodes Dl and D2 conducting a current flow from the emitter side to the collector side are arranged between the collector and emitter of each of IGBT elements Ql and Q2, respectively.
• Inverter 14 includes an U-phase arm 15, a V-phase arm 16, and a W-phase arm 17.
• U-phase arm 15, V-phase arm 16 and W-phase arm 17 are provided in parallel between the power supply line and earth line.
• U-phase arm 15 is formed of IGBT elements Q3 and Q4 connected in series.
• V-phase arm 16 is formed of IGBT elements Q5 and Q6 connected in series.
• W-phase arm 17 is formed of IGBT elements Q7 and Q8 connected in series.
• diodes D3 - D8 conducting a current flow from the emitter side to the collector side are connected between the collector and emitter of each of IGBT elements Q3 - QS, respectively.
• the intermediate point of each phase arm is connected to each phase end of each phase coil in AC motor Ml .
• AC motor Ml is a 3 -phase permanent magnet motor, having one end of the three coils of the U, V, and W phases connected common to the neutral point.
• the U-phase coil has the other end connected to the intermediate point of IGBT elements Q3 and Q4.
• the V-phase coil has the other end connected to the intermediate point of IGBT elements Q5 and Q6.
• the W-phase coil has the other end connected to the intermediate point of IGBT elements Q7 and Q8.
• the switching elements included in voltage-up converter 12 and inverter 14 are not limited to IGBT elements Ql- Q8, and may be formed of other power elements such as a MOSFET.
• Battery B is a chargeable secondary battery.
• it is a nickel- hydrogen or lithium-ion battery.
• a chargeable accumulator other than a secondary battery, such as a capacitor may be employed.
• Voltage sensor 10 detects DC voltage Vb output from battery B and provides the detected DC voltage Vb to control device 30.
• Capacitor Cl smoothes DC voltage Vb supplied from battery B and provides the smoothed DC voltage Vb to voltage-up converter 12.
• Voltage-up converter 12 boosts DC voltage Vb supplied from battery B and provides the boosted voltage to capacitor C2. Specifically, when voltage-up converter 12 receives a signal PWMC from control device 30, voltage-up converter 12 boosts DC current according to the ON period of IGBT element Q2 by signal PWMC and supplies the boosted DC voltage to capacitor C2. Further, when voltage-up converter 12 receives signal PWMC from control device 30, DC voltage supplied from inverter 12 via capacitor C2 is lowered to charge battery B.
• Capacitor C2 smoothes the DC voltage from voltage-up converter 12 and provides the smoothed DC voltage to inverter 14.
• Voltage sensor 13 detects the voltage across capacitor C2, i.e. output voltage Vh of voltage-up converter 12
• inverter 14 converts the DC voltage into AC voltage based on a signal PWMI from control device 30 to drive AC motor Ml . Accordingly, AC motor Ml is driven so as to generate the required torque specified by the torque command.
• inverter 14 converts the AC voltage generated by AC motor Ml into DC voltage based on signal PWMI from control device 30, and provides the converted DC voltage to voltage-up converter 12 via capacitor C2.
• regenerative braking includes braking in association with regenerative power generation when the driver of the hybrid vehicle or electric vehicle operates the foot brake as well as reducing the vehicle speed (or ceasing acceleration) while effecting regenerative power generation by setting off the accelerator pedal during running without operating the foot brake.
• Current sensor 24 detects motor current MCRT flowing to AC motor Ml, and provides the detected motor current MCRT to control device 30.
• Rotation position sensor 26 is attached to the rotational shaft of AC motor Ml to detect and provide to control device 30 a rotation angle ⁇ n of the rotator of AC motor Ml .
• Control device 30 receives the target value of the drive torque required of AC motor Ml (hereinafter, also referred to as target drive torque) Tbt and motor revolution count Nm from an externally provided ECU (Electric Control Unit), receives output voltage Vh from voltage sensor 13, receives DC voltage Vb from voltage sensor 10, and receives motor current MCRT from current sensor 24. Based on output voltage Vh, target drive torque Tbt, and motor current MCRT, control device 30 generates a signal PWMI to control the switching of IGBT elements Q3 - Q8 of inverter 14 when inverter 14 drives AC motor Ml by a method that will be described afterwards, and provides the generated signal PWMI to inverter 14.
• target drive torque the drive torque required of AC motor Ml
• Nm Electric Control Unit
• control device 30 When inverter 14 drives AC motor Ml, control device 30 generates a signal PWMC based on DC voltage Vb, output voltage Vh, target drive torque Tbt and motor revolution count MRN to control the switching of IGBT elements Ql and Q2 of voltage-up converter 12 by a method that will be described afterwards, and provides the generated signal PWMC to voltage-up converter 12.
• control device 30 generates and provides to system relays SRl and SR2 a signal SE to turn on/off system relays SRl and SR2.
• Fig. 2 is a functional block diagram of control device 30 of Fig. 1.
• control device 30 includes an inverter control circuit 301 and a converter control circuit 302.
• Inverter control circuit 301 generates, when current motor Ml is driven, a signal PWMI to turn on/offlGBT elements Q3 - Q8 of inverter 14 by a method that will be described afterwards, based on target drive torque Tbt, motor current MCRT and output voltage Vh, and provides the generated signal PWMI to inverter 14.
• inverter control circuit 301 During regenerative braking of the hybrid vehicle or electric vehicle in which motor drive device 100 is incorporated, inverter control circuit 301 generates and provides to inverter 14 a signal PWMI to convert the AC voltage generated by AC motor Ml into DC voltage based on target control torque Tbt, motor current MCRT, and output voltage Vh.
• Converter control circuit 302 generates a signal PWMC, based on target drive torque Tbt, motor revolution count Nm, output voltage Vh and DC voltage Vb to turn on/off IGBT elements Ql and Q2 of voltage-up converter 12 by a method that will be described afterwards, and provides the generated signal PWMC to voltage-up converter 12.
• converter control circuit 302 During regenerative braking of the hybrid vehicle or electric vehicle in which motor drive device 100 is incorporated, converter control circuit 302 generates signal PWMC based on target drive torque Tbt, motor revolution count Nm, output voltage Vh and DC voltage Vb to lower the DC voltage from inverter 14, and provides the generated signal PWMC to voltage-up converter 12.
• Fig. 3 is a functional block diagram of inverter control circuit 301 of Fig. 2.
• inverter control circuit 301 includes a damping control unit 40 for the inverter, a phase voltage calculation unit 42 for motor control, and a PWM signal converter 44 for the inverter.
• Inverter damping control unit 40 adds torque to cancel the torque variation (hereinafter, also referred to as damping torque) Tc to target drive torque Tbt from external ECU in order to suppress pulsation occurring at the output torque of AC motor Ml.
• damping torque Tc is generated by extracting the variation component of the number of revolutions from the detected result of motor revolution count Nm and obtaining torque based on a phase opposite to the extracted variation component (damping torque).
• Generated damping torque Tc is added to target drive torque Tbt applied from external ECU. The added result is output to motor control phase voltage calculation unit 42 as torque command Tcmd.
• Motor control phase voltage calculation unit 42 receives input voltage Vh of inverter 14 from voltage sensor 13, motor current MCRT flowing through each phase of AC motor Ml from current sensor 24, and torque command Tcmd from inverter damping control unit 40. Motor control phase voltage calculation unit 42 outputs control inputs Vu*, Vv*, and Vw* of the voltage to be applied to the coil of each phase of AC motor Ml based on the input signals set forth above.
• Inverter PWM signal converter 44 actually generates signal PWMI to turn on/off each of IGBT elements Q3 - Q8 of inverter 14 based on control inputs Vu*, Vv*, and Vw* of the voltage from motor control phase voltage calculation unit 42, and provides the generated signal PWMI to each of IGBT elements Q3 - Q8.
• each of IGBT elements Q3 - Q8 is subject to switching-control to control the current conducted to each phase of AC motor Ml such that AC motor Ml outputs the specified torque. Accordingly, motor drive current MCRT is controlled, and motor torque according to torque command Tcmd is output.
• Fig. 4 is a functional block diagram of converter control circuit 302 of Fig. 2.
• converter control circuit 302 includes a damping control unit 50 for the converter, a voltage command calculation unit 52, a duty ratio converter 54 for the converter, and a PWMC signal converter 56 for the converter.
• Converter damping control unit 50 adds damping torque Tcct to target drive torque Tbt from external ECU to generate torque command Tht that is to be used in the control of voltage-up converter 12. It is to be noted that converter damping control unit 50 sets damping torque
• Tcct to a predetermined value independent of the revolution variation component appearing in motor revolution count Nm by a method that will be described afterwards, different from damping torque Tc generated at inverter damping control unit 40.
• the set damping torque Tcct is added to target drive torque Tbt from external ECU.
• the added result is output to voltage command calculation unit 52 as torque command Tht.
• Voltage command calculation unit 52 calculates the optimum value of inverter input voltage Vh (target value), i.e. voltage command Vht, based on torque command Tht from converter damping control unit 50 and motor revolution count Nm from external ECU, and provides the calculated voltage command Vht to converter duty ratio calculation unit 54.
• target value i.e. voltage command Vht
• Converter PWM signal converter 56 generates a signal PWMC to turn on/off IGBT elements Ql and Q2 of voltage-up converter 12 based on duty ratio DR from converter duty ratio calculation unit 54.
• the generated signal PWMC is output to voltage-up converter 12.
• Fig. 5 is a functional block diagram of converter damping control unit 50 of Fig. 4.
• converter damping control unit 50 includes a damping torque setting unit 501 for the converter, and an adder 502.
• Converter damping torque setting unit 501 fixes damping torque Tcct to a predetermined value that is set in advance for output.
• the predetermined value is set to an upper limit value Tc_max of damping torque Tc that can be set in damping control.
• Damping torque upper limit value Tc_max is preset for damping torque Tc taking into account the stability of damping control.
• damping torque Tcct for converter control is a fixed value independent of motor revolution count Nm, as compared to damping torque Tc generated by inverter damping control unit 40 and that is variable corresponding to motor revolution count Nm.
• damping torque Tcct is fixed to damping torque upper limit value Tc_max.
• Fig. 6 is a diagram to describe the relationship between torque command Tht and voltage command Vht.
• target drive torque Tbt applied from external ECU exhibits a waveform that increases monotonously as indicated by a straight line LNl .
• Torque command Tcmd obtained by adding damping torque Tc generated based on the variation component of motor revolution count Nm with target drive torque Tbt exhibits a waveform that varies above and below target drive torque Tbt, as indicated by line LN2.
• Inverter control circuit 301 controls motor drive current MCRT such that AC motor Ml outputs torque corresponding to torque command Tcmd.
• Motor drive device 100 is characterized in that torque command Tht employed in the calculation of voltage command Vht of voltage-up converter 12 is generated by adding damping torque upper limit value Tc_max to target drive torque Tbt, as indicated by line LN3 in Fig. 6.
• Damping torque upper limit value Tc max is preset in view of preventing damping torque Tc from significantly exceeding the normal variation range by the noise component superimposed on motor revolution count Nm at motor drive device 100.
• torque command Tht becomes independent of the varying component of motor revolution count Nm, and exhibits a waveform without variation.
• voltage command Vht calculated based on this torque command Tht will exhibit a waveform without variation, as indicated by straight line LN5. Therefore, increase in the current passing through voltage-up converter 12 due to variation in voltage command Vht can be prevented. As a result, AC motor Ml can be further improved in efficiency by virtue of reducing power loss of voltage-up converter 12. Additionally, voltage-up converter 12 can be protected from element fracture.
• inverter input voltage Vh can be maintained at a level sufficiently higher than motor drive voltage required to output the torque for damping control, i.e. torque command Tcmd.
• torque command Tcmd motor drive voltage required to output the torque for damping control
• Fig. 7 is a flow chart to describe voltage conversion control according to the first embodiment of the present invention.
• target drive torque Tbt of AC motor Ml is calculated according to the accelerator operation or the like by the driver.
• the calculated target drive torque Tbt is applied to each of inverter control circuit 301 and converter control circuit 302 (step SOl).
• Inverter control circuit 301 extracts the variation component of motor revolution count Nm, and generates damping torque Tc from the revolution variation component, independent of the flow chart of Fig. 7.
• Inverter control circuit 301 adds the generated damping torque Tc with target drive torque Tbt, which is set as torque command Tcmd employed in motor drive control.
• Converter control circuit 302 sets damping torque upper limit value Tc_max to damping torque Tcct (step S02), and adds the set damping torque Tcct with target drive torque Tbt from external ECU, which is set as torque command Tht employed in the calculation of voltage command Vht (step S03).
• voltage command Vht is calculated by equation (1) set forth below based on the set torque command Tht and motor revolution count Nm from external ECU (step S04).
• Vht F (Tht, Nm) (1) where F (Tht, Nm) is a function to calculate motor drive voltage Vh optimum for the target operating state (Tht, Nm) of AC motor Ml.
• step S05 By controlling switching of IGBT elements Ql and Q2 of voltage-up converter 12 based on voltage command Vht (step S05), motor drive voltage Vh sufficient for a torque output specified by torque command Tcmd is applied stably to inverter 14.
• increase in the current passing through the voltage-up converter can be suppressed by suppressing variation of the voltage command.
• power loss at voltage-up converter 12 can be reduced to improve the system efficiency.
• the voltage-up converter can be protected from element fracture.
• torque command Tht at converter control circuit 302 is generated using damping torque Tcct fixed to damping torque upper limit value Tcjnax, independent of inverter control circuit 301.
• motor drive device 100 controls the output torque of AC motor Ml such that the power balance of the entire device does not exceed the input/output limit of battery B. This is directed to preventing charging/discharging of battery B by excessive power. In accordance with motor drive device 100, the power consumed by AC motor
• the motor consumed power and motor generated power are both calculated by multiplying the output torque from AC motor Ml by motor revolution count Nm.
• the upper limit value of torque that may be output from AC motor Ml is calculated such that the calculated motor consumed power and motor generated power do not exceed the input/output limit of battery B Therefore, the calculated upper limit value torque will be limited to become smaller as motor revolution count Nm becomes higher.
• the second embodiment of the present invention is directed to setting damping torque upper limit value Tc_max that is added to target drive torque Tbt to become gradually smaller as motor revolution count Nm becomes higher. Accordingly, charging/discharging of the battery B by excessive power can be prevented regardless of whether motor revolution count Nm is high or low. Further, power loss of voltage-up converter 12 and AC motor Ml can be reduced to realize operation of AC motor Ml at high efficiency
• Fig. 8 is a diagram representing the relationship between damping torque upper limit value Tc_max and motor revolution count Nm.
• damping torque upper limit value Tc_max is fixed to a predetermined value Tc_maxl that is set in advance in the region where motor revolution count Nm is equal to or below a predetermined threshold value Nm_std, as indicated by line LNlO
• damping torque upper limit value Tc_max is set to gradually decrease from the level of predetermined value Tc_maxl according to a higher motor revolution count Nm.
• line LN9 in Fig. 8 represents the relationship between damping torque upper limit value Tc_max and motor revolution count Nm when damping torque upper limit value Tc_max is fixed to predetermined value Tc maxl.
• damping torque upper limit value Tc max variable according to motor revolution count Nm
• the power loss of voltage-up converter 12 and motor loss can be reduced by a level corresponding to the power indicated at region RGN in Fig. 8, as compared to damping torque upper limit value Tc_max taking a fixed value.
• damping torque upper limit value Tc_max taking a fixed value.
• Fig. 9 is a flow chart to describe voltage conversion control according to the second embodiment of the present invention.
• the flow chart of Fig. 9 corresponds to the flow chart of Fig. 7, provided that step SOl in Fig. 7 is modified to steps SOl 1 and S012. Therefore, detailed description of the operation of steps S02 and et seq. will not be repeated.
• target drive torque Tbt of AC motor Ml is calculated according to the accelerator operation or the like by the driver.
• the calculated target drive torque Tbt is applied together with motor revolution count Nm to inverter control circuit 301 and converter control circuit 302 (step SOU).
• Converter control circuit 302 stores, in its internal storage region, a map indicating the relationship between motor revolution count Nm and damping torque upper limit value Tcjnax shown in Fig. 8.
• Converter control circuit 302 selects damping torque upper limit value Tc_max corresponding to the input motor revolution count Nm from the map of Fig. 8 (step S012).
• Damping torque upper limit value Tc_max selected at step SO 12 is set to damping torque Tcct (step SO 12), and added to target drive torque Tbt applied from external ECU. The added result is set to torque command Tht (step S03).
• damping torque upper limit value Tc max is set variable according to motor revolution count Nm to protect battery B and voltage- up converter 12 as well as to realize operation of AC motor Ml at high efficiency.
• improvement of fuel efficiency can be facilitated without degrading the riding comfort of the vehicle by adapting a configuration in which damping torque upper limit value Tc_max is set variable according to the speed of the vehicle in which motor drive device 100 is incorporated.
• Fig. 10 represents the relationship between vehicle speed V of the vehicle in which motor drive device 100 is incorporated and damping torque upper limit value Tc_max.
• damping torque upper limit value Tc_max is set to gradually decrease as the vehicle speed becomes higher, as indicated by line LNl 2.
• the relationship between vehicle speed V and damping torque upper limit value Tc_max when damping torque upper limit value Tc_max is fixed at a constant value Tc_maxl, independent of vehicle speed V, is indicated by line LNI l in Fig. 10.
• damping torque upper limit value Tc_max of line LN 12 is lower than constant value Tc_maxl at the region exceeding predetermined vehicle speed V_std.
• the configuration of decreasing damping torque upper limit value Tcjnax according to a higher vehicle speed V is employed based on the fact that the required damping torque is reduced since the revolution variation component caused by a sudden change in target drive torque Tbt and motor revolution count Nm becomes relatively smaller in proportion to a higher vehicle speed V.
• the torque pulsation is smaller in the region where vehicle speed V is high than in the region where vehicle speed V is low, sufficient riding comfort of a vehicle can be ensured by setting damping torque upper limit value Tc_max to a relatively low value.
• torque command Tht applied to voltage command calculation unit 52 is set to a relatively lower value than torque command Tht when damping torque upper limit value Tc_max is set to a constant value Tc_maxl .
• Voltage command Vht calculated on the basis of torque command Tht also becomes lower as torque command Tht decreases. This eliminates the useless boosting of the motor drive voltage when vehicle speed V is high. Therefore, power loss of voltage-up converter 12 and motor loss can be reduced. Thus, fuel efficiency of the vehicle can be improved.
• damping torque upper limit value variable By setting the damping torque upper limit value variable according to the motor revolution count in the second embodiment of the present invention, charging/discharging of the battery by excessive current can be prevented, and power loss of the voltage-up converter and AC motor can be reduced to allow high frequency operation of the AC motor.
• Damping control is effective to suppress vehicle variation caused by torque pulsation when there is a sudden change in the torque command and/or motor revolution. If damping control is conducted uniformly even in the case where determination is made that effectiveness in damping control is relatively low, i.e. when torque pulsation is relatively low, voltage command Vht will constantly be raised corresponding to the damping torque upper limit value, leading to the problem that power loss of voltage-up converter 12 is increased unfavorably.
• the third embodiment of the present invention is configured to determine the effectiveness/ineffectiveness of damping control and suspend damping control, when determination is made that damping control is not effective, to prevent voltage command Vht from being increased corresponding to damping torque upper limit value Tc_max.
• Fig. 11 is a diagram to describe voltage command Vht according to the third embodiment of the present invention.
• the damping control- flag is set ON when damping control is to be executed, and set OFF when damping control is suspended.
• Execution/suspension of damping control is determined according to the determination result of effective/ineffective damping control by converter damping control unit 50 of converter control circuit 302. Determination of whether damping control is effective or ineffective is made based on target drive torque Tbt and motor revolution count Nm input from external ECU applied to converter damping control unit 50.
• converter damping control unit 50 determines that damping control is effective in response to a sudden change in target drive torque Tbt or motor revolution count Nm. In response to determination of damping control being effective, the damping control flag is set to an on state instructing execution of damping control. In contrast, converter damping control unit 50 determines that damping control is ineffective when target drive torque Tbt and motor revolution count Nm do not change suddenly. In this case, the damping control flag is set to an off state instructing suspension of damping control according to an ineffective damping control determination.
• Converter damping torque setting unit 501 sets damping torque Tcct according to an ON or OFF setting of the damping control flag.
• converter damping torque setting unit 501 outputs damping torque upper limit value Tc_max to adder 502 as damping torque Tcct. Accordingly, the added result of target drive torque Tbt and damping torque Tcct is output to voltage command calculation unit 52 as torque command Tht.
• converter damping torque setting unit 501 sets damping torque Tcct to zero and provides this damping torque to adder 502. Accordingly, target drive torque Tbt is directly output to voltage command calculation unit 52 as torque command Tht.
• Voltage command calculation unit 52 calculates voltage command Vht based on the input torque command Tht for each of an execution mode and suspension mode of damping control. As indicated by line LN6 in Fig. 11, the calculated voltage command Vht is raised corresponding to damping torque Tcct with respect to voltage command Vhti calculated based on target drive torque Tbt from time tl to time t2, and time t3 onward, during which the damping control flag is ON. During the period from time t2 to time t3 when the damping control flag is OFF, voltage command Vht is equal to voltage command Vhti calculated based on target drive torque Tbt.
• Fig. 12 is a flow chart to describe voltage conversion control according to a third embodiment of the present invention.
• target drive torque Tbt of AC motor Ml is calculated based to an accelerator operation or the like by the driver.
• the calculated target drive torque Tbt is applied together with motor revolution count Nm to both inverter control circuit 301 and converter control circuit 302 (step SOU).
• Converter control circuit 302 first determines whether damping control is effective/ineffective based on target drive torque Tbt and motor revolution count Nm.
• the damping control flag is set to an on state or an off state according to the determination result.
• Converter damping torque setting unit 501 determines whether the damping control flag is ON or not (step SO 13). When determination is made that the damping control flag is ON at step SO 13, i.e. determination of damping control being effective, converter damping torque setting unit 501 sets damping torque upper limit value Tc_max to damping torque Tcct (step S02). The set damping torque Tcct is added with target drive torque Tbt from external ECU, and set to torque command Tht employed in the calculation of voltage command Vht (step S03). When determination is made that the damping control flag is OFF at step SOl 3, i.e. determination of damping control being ineffective, converter damping torque setting unit 501 directly sets target drive torque Tbt as torque command Tht (step SO 14).
• Torque command Tht set at each of steps S03 and SO 14 is provided to voltage command calculation unit 52.
• Voltage command calculation unit 52 calculates voltage command Vht based on torque command Tht and motor revolution count Nm from external ECU (step S04). By controlling the switching of IGBT elements Ql and Q2 of voltage-up converter 12 based on the calculated voltage command Vht (step S05), motor drive voltage Vh of a level sufficient to output the torque specified by torque command Tcmd can be applied stably to inverter 14. [Modification]
• Battery B has the power that can be input and output limited, as mentioned before. The limit thereof becomes stricter as the temperature of battery B becomes lower. If power exceeding the input/output limit of battery B is charged or discharged according to the switching between execution and suspension of damping control when the battery temperature is low, voltage surge will occur instantaneously at the DC voltage of battery B, leading to the possibility of damaging battery B.
• the present modification is directed to a configuration in which switching from execution to suspension of damping control is not carried out and execution of damping control is continued when the battery temperature is low.
• Fig. 13 is a diagram to describe voltage command Vht according to the modification of the third embodiment.
• Fig. 14 is a flow chart to describe voltage conversion control according to the modification of the third embodiment.
• target drive torque Tbt of AC motor Ml is calculated according to an accelerator operation or the like by the driver.
• the calculated target drive torque Tbt is applied together with motor revolution count Nm to inverter control circuit 301 and converter control circuit 302 (step SOU).
• Converter control circuit 302 first determines whether damping control is effective/ineffective based on target drive torque Tbt and motor revolution count Nm.
• the damping control flag is set to an on state or an off state according to the determination result.
• Converter damping torque setting unit 501 determines whether the damping control flag is ON or not (step SO 13). When determination is made that the damping control flag is ON, i.e. when determination is made that damping control is effective at step SO 13, converter damping torque setting unit 501 sets damping torque upper limit value Tc_max to damping torque Tcct (step S02). The set damping torque Tcct is added with target drive torque Tbt from external ECU to be set as torque command Tht used for the calculation of voltage command Vht (step S03) When determination is made that the damping control flag is OFF, i.e. when determination is made that damping control is ineffective at step SO 13, converter damping torque setting unit 501 determines whether the temperature of battery B is at most a predetermined threshold value (step SO 130).
• damping torque upper limit value Tc_max is set to damping torque Tcct, likewise the case where damping control is effective (step S02).
• target drive torque Tbt is directly set as torque command Tht (step SO 14). Torque command Tht set at each of steps S03 and S014 is provided to voltage command calculation unit 52.
• Voltage command calculation unit 52 calculates voltage command Vht based on torque command Tht and motor revolution count Nm from external ECU (step S04). By controlling switching of IGBT elements Ql and Q2 of voltage-up converter 12 based on the calculated voltage command Vht (step S05), motor drive voltage Vh of a level sufficient for output of torque specified by torque command Tcmd is applied stably to inverter 14
• Fig. 15 is a functional block diagram of a converter damping control unit in a motor drive device according to a fourth embodiment of the present invention.
• the motor drive device of the fourth embodiment is similar to motor drive device 100 of Fig. 1, provided that converter damping control unit 50 shown in Fig. 5 is replaced with a converter damping control unit 50A shown in Fig. 15. Therefore, description of similar elements will not be repeated.
• converter damping control unit 50A includes a damping torque index determination unit 503, a converter damping torque setting unit 501 A, and an adder 502.
• Damping torque index determination unit 503 receives an input signal from various elements of the vehicle via external ECU. These input signals include, for example, vehicle speed V detected by a vehicle speed sensor, an accelerator press-down amount detected by an accelerator pedal position sensor, a signal IG indicating the operation state of ignition (IG), and target drive torque Tbt.
• Damping torque index determination unit 503 determines the vehicle state based on these input signals. Specifically, determination is made whether the vehicle is in an extremely low running mode or not based on vehicle speed V. Further, determination is made whether the vehicle is accelerating or not based on the accelerator press-down amount. Further, determination is made whether the engine is at an engine startup or stop state based on signal IG.
• damping torque index determination unit 503 determines a damping torque index Kc with respect to the determined vehicle state. Damping torque index Kc is used for setting damping torque Tcct. Damping torque Tcct is represented by a function of damping torque index Kc, as in the following equation (2):
• Tcct Tccv_tbl (Kc) (2) where Tccv_tbl (x) is a function to calculate damping torque Tcct corresponding to x.
• Determination of the damping torque index is carried out by preparing a table indicating the relationship between the vehicle state and damping torque index shown in Fig. 16, and selecting a damping torque index corresponding to the determined vehicle state from the preset table.
• a damping torque index Kc is set corresponding to each of a plurality of vehicle states. For example, damping torque index Kc is set to "0" when the vehicle is in an extremely low speed mode. When the vehicle corresponds to a speed other than the extremely low speed, i.e. when in a low/middle vehicle speed or high vehicle speed mode, damping torque index Kc is set to " 1 ".
• damping torque index Kc is set to "2" when the engine is in an engine startup mode or in an engine stop mode. Additionally, when target drive torque Tbt suddenly changes or when the accelerator press-down amount suddenly changes, damping torque index Kc is set to "3".
• the set states of the vehicle are not limited thereto. For example, damping torque index Kc corresponding to the state of the running road of the vehicle (road roughness information) obtained from a navigation device or the like can be set to "4" when the roughness of the road is relatively great.
• Damping torque index determination unit 503 selects a damping torque index Kc corresponding to the vehicle state determined based on various input signals from the table of Fig. 16, and provides the selected damping torque index Kc to damping torque setting unit 50A. Upon receiving selected damping torque index Kc, damping torque setting unit 50A inserts damping torque index Kc to equation (2) set forth above to calculate damping torque Tcct.
• Fig. 17 is a diagram representing the relationship between damping torque index Kc and damping torque Tcct.
• damping torque Tcct calculated based on damping torque index Kc indicates a different value for each damping torque index Kc.
• damping torque Tcct takes a variable value set to a different value corresponding to the vehicle state.
• the motor drive device differs from the motor drive device of the first embodiment that has damping torque Tcct fixed to damping torque upper limit value Tc_max.
• Fig. 18 is a timing chart of the damping control flag, damping torque index Kc and damping torque Tcct generated based on Figs. 16 and 17.
• damping torque Tcct is set to the next highest value when in an extremely low speed mode in which waviness occurs in motor revolution count Nm or in an acceleration mode in which the target drive torque or accelerator press-down amount suddenly changes although the torque pulsation is lower than that in an engine startup mode/engine stop mode.
• damping torque Tcct is set to the lowest value when running steadily such as in a low/middle speed mode or high speed mode in which torque pulsation is relatively low.
• sufficient damping torque required for execution of damping control can be set appropriately according to the vehicle state.
• Fig. 19 is a flow chart to describe voltage conversion control according to the fourth embodiment of the present invention.
• target drive torque Tbt of AC motor Ml is calculated according to an accelerator pedal operation or the like by the driver.
• the calculated target drive torque Tbt is applied together with motor revolution count Nm to inverter control circuit 301 and converter control circuit 302 (step SOl 1).
• Converter control circuit 302 first determines the effectiveness/ineffectiveness of damping control based on target drive torque Tbt and motor revolution count Nm.
• the damping control flag is set to an on state or an off state according to the determination result.
• Damping torque index determination unit 503 determines whether the damping control flag is ON or not (step SO 13). When determination is made that the damping control flag is ON at step SO 13, i.e. determination is made that damping control is effective, damping torque index determination unit 503 determines the vehicle state based on various input signals (step S020). Then, damping torque index Kc corresponding to the determined vehicle state is selected from the table of Fig. 16 to determine damping torque index Kc (step S021). The determined damping torque index Kc is output to damping torque setting unit 501 A. Damping torque setting unit 50 IA calculates damping torque Tcct based on damping torque index Kc (step S022).
• the calculated damping torque Tcct is added with target drive torque Tbt from external ECU to be set as torque command Tht (step S03).
• converter damping torque setting unit 501 directly sets target drive torque Tbt as torque command Tht (step SO 14).
• Torque command Tht set at each of steps S03 and SO 14 is provided to voltage command calculation unit 52.
• Voltage command calculation unit 52 calculates voltage command Vht based on torque command Tht and motor revolution count Nm from external ECU (step S04). Then, the switching of IGBT elements Ql and Q2 of voltage-up converter 12 is controlled based on the calculated voltage command Vht (step S05). Motor drive voltage Vh sufficient to output torque specified by torque command Tcmd is applied stably to inverter 14.
• damping torque Tcct When damping torque Tcct is altered according to the vehicle state, damping torque Tcct varies in a stepped manner according to the switching of damping torque index Kc, as described with reference to Fig. 18. Since torque command Tht also varies in a stepped manner correspondingly, voltage command Vht calculated based on torque command Vht will change in a stepped manner.
• the present modification has the rate of change set to avoid exceeding the time constant in the voltage-up operation of voltage-up converter 12 when damping torque Tcct increases, as shown in Fig. 20. Accordingly, unstable damping control caused by insufficient torque can be prevented.
• the present first modification is directed to setting the rate of change when damping torque Tcct decreases to a relatively low value with respect to the rate of change when damping torque Tcct increases, taking into consideration vehicle vibration due to a sudden change in the output torque, to decrease the output torque gently, as shown in Fig. 20.
• such adjustment in the rate of change of damping torque Tcct is executed by converter damping torque setting unit 50A shown in Fig. 15.
• a predetermined feedback gain coefficient Kfb is multiplied by the PI control gain (P gain Kp, I gain Ki) to increase or decrease the Pi control gain.
• Fig. 21 is a timing chart of the damping control flag, damping torque index Kc, feedback gain coefficient Kfb, and damping torque Tcct.
• Feedback gain coefficient Kfb is set to be gradually reduced towards zero to avoid generation of discontinuity in the output torque set forth above when switching from execution to suspension of damping control.
• damping control is substantially suspended.
• damping torque Tcct decreases mildly at a predetermined rate of change when switching from execution to suspension of damping control.
• the predetermined voltage rate is set to become lower than the decreasing rate of the feedback gain coefficient. This is to prevent damping control from being forced to be suspended as a result of damping torque Tcct attaining 0 Nm at a earlier timing than feedback gain coefficient Kfb.
• the present modification is directed to forcing damping torque Tcct to 0 Nm in response to feedback gain coefficient Kfb arriving at zero. Accordingly, damping torque Tcct is set to 0 Nm at the timing of damping control being suspended. Therefore, useless boosting is prevented and power loss at voltage-up converter 12 can be further reduced. As a result, further improvement of the fuel efficiency of the vehicle is allowed.
• damping torque Tcct is to be increased immediately at a rate of change not exceeding the time constant of the boosting operation, as indicated previously in the first modification.
• such adjustment in the rate of change of damping torque Tcct is executed by converter damping torque setting unit 50A shown in Fig. 15.
• damping torque sufficient required for execution of damping control is appropriately set according to the vehicle state in the fourth embodiment of the present invention, useless increase in the voltage command caused by the damping torque being set higher than necessary can be prevented. Therefore, power loss at the voltage-up converter and motor loss can be reduced without .degrading the riding comfort of the vehicle, and fuel efficiency of the vehicle can be improved
• the present invention can be employed in a motor drive device with a damping control function of output torque.

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