JP6191128B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus having an auxiliary power source.

  A conventional electric power steering apparatus has an electric motor for assisting steering and an auxiliary power source connected to a main power source. A conventional electric power steering device has a main power when the power consumed by the device is equal to or higher than a charge / discharge threshold value that is a reference value for switching charging from the main power source to the auxiliary power source and discharging from the auxiliary power source to the electric motor. Power is supplied to the electric motor from the power supply and auxiliary power supply. Patent Document 1 shows an example of the configuration of a conventional electric power steering apparatus.

JP 2010-23821 A

  When the vehicle urgently avoids an obstacle and a collision avoidance target such as a preceding vehicle that travels in front of the vehicle, the driver performs sudden steering, and thus the steering speed increases. For this reason, since the electric power steering apparatus performs assist according to the steering speed at the time of sudden steering, the rotation speed of the electric motor is increased. For this reason, it is preferable that the voltage applied to the electric motor is high.

  In the conventional electric power steering device, since the electric power is supplied from the main power supply and the auxiliary power supply to the electric motor when the power supply power is equal to or higher than the charge / discharge threshold, the voltage applied to the electric motor when the power supply power is equal to or higher than the charge / discharge threshold. Becomes higher. However, when the vehicle urgently avoids the collision avoidance target, the power supply power is not always equal to or higher than the charge / discharge threshold. For this reason, there is room for improvement in the supply of electric power to the electric motor when the vehicle urgently avoids the collision avoidance target.

  The present invention was created based on the above background, and provides an electric power steering device capable of appropriately supplying electric power to an electric motor when a vehicle urgently avoids a collision avoidance target. With the goal.

(1) This means “is connected to an electric motor that generates an assist torque for assisting steering of a steering component based on the steering torque, and a main power source that supplies electric power to the electric motor, and is discharged to the electric motor. A possible auxiliary power supply, a first power supply form that supplies power from the main power supply to the electric motor, and a motor control device that switches between the main power supply and a second power supply form that supplies power from the auxiliary power supply to the electric motor; The motor control device is based on at least one of a collision time and a steering speed, which is a time for the vehicle to reach the collision avoidance object, or a vehicle speed, a relative distance between the vehicle and the collision avoidance object, and a steering speed. Based on this, it is determined whether the degree of urgency for avoiding the collision avoidance object is high or low. It has a time control, when the urgency of emergency avoidance of the vehicle is high, having an electric power steering device "to increase the discharge speed of the auxiliary power supply.

In the electric power steering apparatus, the second power supply mode is set during emergency avoidance of the vehicle by emergency control. For this reason, compared with the structure which changes from the 1st power supply form to the 2nd power supply form by the conventional power supply electric power more than a charging / discharging threshold value, electric power is appropriately supplied to an electric motor at the time of emergency avoidance of a vehicle. In the electric power steering device, when the urgent degree of emergency avoidance of the vehicle is high, the amount of electric power supplied to the electric motor increases or the increase rate of the electric energy increases. For this reason, the electric power required for the electric motor can be quickly supplied. Further, when the urgent degree of emergency avoidance of the vehicle is low, the amount of electric power supplied to the electric motor is reduced, or the increase rate of the electric energy is reduced. For this reason, a rapid change in the assist torque can be suppressed.

  (2) One mode of the above means is that “the motor control device is charged from the main power source to the auxiliary power source and the auxiliary power source is supplied from the electric power steering device consumed by the assist control for assisting steering. When the charge / discharge threshold value that is a reference value for switching the discharge to the electric motor is equal to or higher than normal control for changing from the first power supply form to the second power supply form, and when the vehicle avoids emergency, An electric power steering device for changing from normal control to emergency control ”.

  In the electric power steering apparatus described above, when the vehicle avoids an emergency, the control is changed from the normal control to the emergency control. Therefore, even if the power supply power is less than the charge / discharge threshold, the first power supply form is changed to the second power supply form. The For this reason, electric power is appropriately supplied to the electric motor during emergency avoidance of the vehicle.

  The electric power steering apparatus can appropriately supply electric power to the electric motor when the vehicle urgently avoids the collision avoidance target.

The block diagram which shows the structure of the vehicle of embodiment. The circuit diagram showing the circuit composition of the electric power steering device of an embodiment. It is a map regarding the electric power steering apparatus of an embodiment, and is a map which shows the relationship between collision time, steering speed, and urgency. The flowchart which shows the process sequence of the power supply control performed by the motor control apparatus of embodiment. The block diagram which shows the control structure of the vehicle of other embodiment.

With reference to FIG. 1, the structure of the vehicle 1 is demonstrated.
A vehicle 1 includes a steering wheel as a steering component 2, two front wheels 3F, two rear wheels 3R, a battery as a main power source 4, an external environment detection device 5, a vehicle speed sensor 6, a drive shaft 7, and electric power steering. Apparatus (hereinafter referred to as “EPS10”).

  The main power supply 4 supplies power to the external environment detection device 5, the EPS 10, and a plurality of auxiliary devices (not shown) mounted on the vehicle 1. Examples of auxiliary machines include wipers, air conditioners, car navigation devices, and the like.

  The external environment detection device 5 is an object that needs to avoid the collision of the vehicle 1 in front of the traveling direction of the vehicle 1 (hereinafter, “vehicle traveling direction”) (hereinafter, “collision avoidance target”). The presence or absence of is detected. Examples of the collision avoidance target object include a preceding vehicle that travels in front of the vehicle traveling direction, or a passerby and a stationary obstacle (for example, a wall) that exist in front of the vehicle traveling direction. Examples of the external environment detection device 5 include a radar system using laser and millimeter wave radio waves, and a stereo image processing system using a stereo camera. The external environment detection device 5 includes a detection unit 5A such as a camera and a radar that detects the front of the vehicle 1 in the traveling direction.

  When the collision avoidance target is detected by the detection unit 5A, the external environment detection device 5 detects the relative distance between the vehicle 1 and the collision avoidance target (hereinafter, “relative distance DA”), and the vehicle 1 and the collision avoidance target. Relative speed (hereinafter referred to as “relative speed VA”). The external environment detection device 5 outputs a signal including the relative distance DA and the relative speed VA to the motor control device 40 of the EPS 10.

The vehicle speed sensor 6 transmits a vehicle speed signal to the motor control device 40 of the EPS 10 through the in-vehicle communication network.
The EPS 10 includes an EPS main body 20, an assist device 30, a motor control device 40, an auxiliary power supply device 50, a torque sensor 60, and a steering angle sensor 70. The EPS 10 has a configuration in which power is supplied from the main power supply 4 and the auxiliary power supply device 50 to the assist device 30 via the motor control device 40. The EPS 10 assists the operation of the steering component 2 by the assist device 30.

  The EPS main body 20 includes a steering shaft 21, a rack shaft 22, a rack and pinion mechanism 23, and two tie rods 24. In the EPS main body 20, the steering shaft 21 rotates as the steering component 2 rotates. The EPS main body 20 changes the turning angle of the front wheel 3F by converting the rotation of the steering shaft 21 into the reciprocating motion of the rack shaft 22 by the rack and pinion mechanism 23.

  The assist device 30 includes an electric motor 31 as a three-phase brushless motor and a speed reduction mechanism 32 as a worm gear. The assist device 30 transmits a force for rotating the steering shaft 21 (hereinafter referred to as “assist torque TA”) to the steering shaft 21 by transmitting it to the steering shaft 21 in a state where the rotation of the electric motor 31 is decelerated via the speed reduction mechanism 32. Give.

The torque sensor 60 transmits a torque signal to the motor control device 40 of the EPS 10 through the in-vehicle communication network.
The steering angle sensor 70 transmits a steering angle signal to the motor control device 40 of the EPS 10 through the in-vehicle communication network.

  The motor control device 40 twists a torsion bar (not shown) connected to an intermediate portion of the steering shaft 21 based on the torque signal of the torque sensor 60, that is, torque applied to the steering shaft 21 as the steering component 2 is operated. The magnitude and direction of (hereinafter “steering torque τ”) are calculated. The motor control device 40 calculates an angle (hereinafter, “steering angle θ”) at which the steering shaft 21 rotates with the rotation of the steering component 2 based on the steering angle signal of the steering angle sensor 70. The motor control device 40 calculates the steering speed ω based on the steering angle θ. The motor control device 40 calculates the traveling speed of the vehicle 1 (hereinafter “vehicle speed V”) based on the vehicle speed signal of the vehicle speed sensor 6. The motor control device 40 performs assist control for assisting steering by the steering component 2 and power control for controlling the operation of the power supplied to the EPS 10.

  The motor control device 40 has normal control and emergency control as power control. The normal control controls the supply form of power to the electric motor 31 by the main power supply 4 and the auxiliary power supply device 50 during normal operation of the vehicle 1. In the emergency control, when the vehicle 1 urgently avoids a collision avoidance target, the power supply form to the electric motor 31 by the main power supply 4 and the auxiliary power supply device 50 is controlled.

With reference to FIG. 2, detailed configurations of the motor control device 40 and the auxiliary power supply device 50 will be described.
The motor control device 40 includes a microcomputer (hereinafter “microcomputer 41”), a motor drive circuit 44, a current sensor 45, and a voltage sensor 46. The motor control device 40 controls the voltage applied to the motor drive circuit 44 (hereinafter “motor drive voltage VMD”).

  In the current sensor 45, the output level of the voltage signal changes according to the magnitude of the actual current supplied to the electric motor 31 (hereinafter “motor current IM”). The current sensor 45 outputs a voltage signal to the motor control unit 43 of the microcomputer 41.

  In the voltage sensor 46, the output level of the voltage signal changes according to the voltage between the auxiliary power supply 50 and the motor drive circuit 44, that is, the magnitude of the motor drive voltage VMD. The voltage sensor 46 outputs a voltage signal to the power management unit 42 of the microcomputer 41.

  The microcomputer 41 has a power management unit 42 and a motor control unit 43. The microcomputer 41 controls the charging / discharging operation of the auxiliary power supply device 50 in the power management unit 42. The microcomputer 41 controls the operation of the motor drive circuit 44 in the motor control unit 43.

  The power management unit 42 controls operations of the relay 51, the booster circuit 53, and the charge / discharge circuit 54 of the auxiliary power supply device 50. The power management unit 42 outputs a relay signal SR for controlling the operation of the relay 51 to the relay 51. The power management unit 42 outputs boost signals SB 1 and SB 2 for controlling the operation of the boost circuit 53 to the boost circuit 53. The power management unit 42 outputs charge / discharge signals SCD 1 and SCD 2 for controlling the operation of the charge / discharge circuit 54 to the charge / discharge circuit 54. In the power management unit 42, the relative distance DA and the relative speed VA of the external environment detection device 5 (see FIG. 1) and the steering speed ω calculated from the steering angle θ of the steering angle sensor 70 (see FIG. 1) are input. Is done.

  The motor control unit 43 generates a motor control signal SM in the assist control. Specifically, the motor control unit 43 calculates a target assist torque based on the steering torque τ and the vehicle speed V. The motor control unit 43 generates the motor control signal SM by executing current feedback control so that the motor current IM matches the current command value corresponding to the target assist torque. The motor control unit 43 then outputs a motor control signal SM to the motor drive circuit 44. The target assist torque increases as the absolute value of the steering torque τ increases or as the absolute value of the vehicle speed V decreases.

  The motor drive circuit 44 has a known configuration in which two switching elements (MOSFETs) are connected in series to the coils (not shown) of each phase of the electric motor 31. In the motor drive circuit 44, the two switching elements of each phase of the electric motor 31 are alternately switched between the on state and the off state. The motor drive circuit 44 applies the motor drive voltage VMD to the electric motor 31 as PWM drive by switching the ON state and the OFF state of each switching element.

  The auxiliary power supply 50 is formed separately from the main power supply 4. The auxiliary power supply device 50 is connected in series with the main power supply 4. The auxiliary power supply device 50 includes a relay 51, a current sensor 52, a booster circuit 53, a charge / discharge circuit 54, and an auxiliary power supply 55 as a capacitor. The auxiliary power supply 50 is discharged to the electric motor 31 via the motor control device 40 by the auxiliary power supply 55.

  The relay 51 is disposed between the main power supply 4 and the booster circuit 53. The relay 51 switches between an on state in which the main power supply 4 supplies power to the motor drive circuit 44 and an off state in which the main power supply 4 does not supply power to the motor drive circuit 44.

  The current sensor 52 is disposed between the relay 51 and the booster circuit 53. In the current sensor 52, the output level of the voltage signal changes according to the magnitude of the output current of the main power supply 4 (hereinafter referred to as “battery current IB”). The current sensor 52 outputs a voltage signal to the power management unit 42.

  The booster circuit 53 boosts the output voltage based on the voltage of the main power supply 4 (battery voltage), that is, the voltage at the connection point P1 between the main power supply 4 and the auxiliary power supply device 50 (hereinafter referred to as “output voltage V1”). The auxiliary power supply 55 can be charged by being applied to a connection point P2 which is an output terminal 55.

  The booster circuit 53 includes a pair of switching elements 53A and 53B and a booster coil 53C. The booster circuit 53 has a configuration in which one end of a booster coil 53C is connected to a connection point P3 of a pair of switching elements 53A and 53B connected in series. The booster circuit 53 has a configuration in which the output voltage V1 is applied to the other end of the booster coil 53C.

  MOSFETs are employed as the pair of switching elements 53A and 53B. The switching element 53A on the upper stage side is connected to the output terminal (connection point P2) of the auxiliary power supply 55 at one end. The switching element 53A is connected to the lower switching element 53B at the other end. The switching element 53B is grounded at one end. The switching element 53B is connected to the connection point P3 at the other end. Each of the switching elements 53A and 53B switches between an on state and an off state based on the boost signals SB1 and SB2 of the power management unit 42.

  The charge / discharge circuit 54 is connected in series with the booster circuit 53. The charge / discharge circuit 54 includes a pair of switching elements 54A and 54B. The charge / discharge circuit 54 has a configuration in which a pair of switching elements 54A and 54B are connected in series to each other. The charge / discharge circuit 54 is connected to the motor drive circuit 44 at a connection point P4 between the pair of switching elements 54A and 54B.

  MOSFETs are employed for the pair of switching elements 54A and 54B. The switching element 54A on the upper stage side is connected to the output terminal (connection point P2) of the auxiliary power supply 55 at one end. The switching element 54A is connected to the lower switching element 54B at the other end. The switching element 54B is connected to the main power supply 4 through the relay 51 and the current sensor 52 at one end.

  Each of the switching elements 54A and 54B periodically switches between an on state that is a conducting state and an off state that is a non-conducting state based on the charge / discharge signals SCD1 and SCD2 of the power management unit 42. When the switching element 54A is in an ON state, the switching element 54A can be discharged from the auxiliary power supply 55 to the motor drive circuit 44. When the switching element 54A is in the OFF state, the switching element 54A cannot discharge from the auxiliary power supply 55 to the motor drive circuit 44. When the switching element 54B is in the ON state, the power can be supplied from the main power supply 4 to the motor drive circuit 44 via the switching element 54B. When the switching element 54B is in the OFF state, power cannot be supplied from the main power supply 4 to the motor drive circuit 44 via the switching element 54B.

  The auxiliary power supply 55 is connected in parallel with the booster circuit 53 and the charge / discharge circuit 54 between the booster circuit 53 and the charge / discharge circuit 54. The auxiliary power supply 55 is connected to the connection point P2 at one end and is connected to the connection point P5 between the current sensor 52 and the switching element 54B at the other end. The auxiliary power supply 55 employs an electric double layer capacitor.

The operation of the relay 51 will be described.
The relay 51 is switched between an on state and an off state based on the relay signal SR of the power management unit 42. The relay 51 is switched from the off state to the on state when an ignition switch (not shown) of the vehicle 1 is turned on. The relay 51 is switched from the on state to the off state when the ignition switch is turned off.

The operation of the booster circuit 53 will be described.
The booster circuit 53 applies the boosted voltage V3 generated by switching the lower-stage switching element 53B from the on state to the off state to the output terminal (connection point P2) of the auxiliary power supply 55. Specifically, in the booster circuit 53, the switching element 53B is turned on when it is turned on, and one end of the booster coil 53C is grounded. The booster circuit 53 superimposes the induced voltage generated in the booster coil 53C when the switching element 53B is switched from the off state to the on state, and outputs the superimposed voltage on the output voltage V1. Note that the switching element 53A on the upper stage side has a function of preventing current from flowing back (backflow) from the auxiliary power supply 55 side to the booster circuit 53 side.

The operation of the charge / discharge circuit 54 will be described.
The charging / discharging circuit 54 includes a first power supply form in which the auxiliary power supply 55 can be charged by the main power supply 4 based on the combination of the ON state and the OFF state of the switching elements 54A and 54B, and the auxiliary power supply 55 is the motor drive circuit 44. The second power supply mode that enables discharge is switched. The switching elements 54A and 54B are controlled by the power management unit 42 so that they are not turned on at the same time.

  In the first power supply mode, the upper switching element 54A is turned off and the lower switching element 54B is turned on. In the first power supply mode, the battery current IB of the main power supply 4 is supplied to the auxiliary power supply 55 and supplied to the motor drive circuit 44 via the switching element 54B. In the first power supply mode, the auxiliary power supply 55 is not discharged to the motor drive circuit 44 because the switching element 54A is in the off state. In the first power supply mode, the motor drive voltage VMD is the output voltage V1.

  In the second power supply mode, the upper switching element 54A is turned on and the lower switching element 54B is turned off. In the second power supply mode, the main power supply 4 and the auxiliary power supply 55 are connected in series with each other. In the second power supply mode, the auxiliary power supply 55 discharges to the motor drive circuit 44 in addition to the power supply to the motor drive circuit 44 of the main power supply 4. In the second power supply mode, the motor drive voltage VMD is the sum of the output voltage V1 and the output voltage V2 of the auxiliary power supply 55.

  In the second power supply configuration, the DUTY ratio as a ratio of the ON state in one cycle of switching of the ON state and the OFF state of the switching element 54A, and the ON in one cycle of switching of the ON state and the OFF state of the switching element 54B. A value other than 100% of the DUTY ratio as the state ratio is also used. For this reason, the motor drive voltage VMD is changed according to the DUTY ratio of the switching elements 54A and 54B. Specifically, the motor drive voltage VMD increases as the DUTY ratio of the switching element 54A increases. When the DUTY ratio of the switching element 54A becomes 100%, the motor drive voltage VMD becomes the maximum value. When the DUTY ratio of the switching element 54A is 50%, the value becomes half of the maximum value of the motor drive voltage VMD.

The normal control executed by the power management unit 42 of the motor control device 40 will be described.
“Power supply power PS” indicates the power of the main power supply 4 consumed by the EPS 10 by the assist control. The power source power PS is calculated based on the battery current IB. The “charge / discharge threshold KE” indicates a reference value for switching charging from the main power supply 4 to the auxiliary power supply 55 and discharging from the auxiliary power supply 55 to the motor drive circuit 44. The charge / discharge threshold KE is set in advance by a test or the like.

  The motor control device 40 sets the charge / discharge circuit 54 to the second power supply mode when the power supply power PS is equal to or higher than the charge / discharge threshold KE in normal control, and performs charge / discharge when the power supply PS is less than the charge / discharge threshold KE. The circuit 54 is set to the first power supply configuration.

  The motor control device 40 is configured to suppress the auxiliary power supply 55 from having a shortage of capacity when the charge / discharge circuit 54 is changed from the first power supply form to the second power supply form in the normal control. The discharge is controlled as follows.

  The motor control device 40 increases the motor drive voltage VMD as the difference between the power source PS and the charge / discharge threshold KE increases. Specifically, the motor control device 40 increases the DUTY ratio of the switching element 54A as the difference between the power source PS and the charge / discharge threshold KE increases.

  Further, when the motor control device 40 changes the charge / discharge circuit 54 from the first power supply form to the second power supply form in the normal time control, the sudden change in the assist torque TA caused by the sudden change in the motor drive voltage VMD. In order to suppress this, the discharge of the auxiliary power supply 55 is controlled as follows.

  The motor control device 40 gradually increases the DUTY ratio of the switching element 54A from a state where the DUTY ratio of the switching element 54A is 0% by a predetermined increase width. Accordingly, the motor control device 40 gradually decreases the DUTY ratio of the switching element 54B from the state where the DUTY ratio of the switching element 54B is 100% by a predetermined reduction width. As a result, the motor drive voltage VMD gradually increases.

  The increase width of the DUTY ratio of the switching element 54A is determined based on the time constant of the transfer function in the power feedback control that is the PID control. The increasing width of the DUTY ratio of the switching element 54A decreases as the time constant increases. The time constant is set in advance. The power feedback control indicates control for changing the motor drive voltage VMD so that the power supply power PS matches the charge / discharge threshold KE when the power supply power PS is larger than the charge / discharge threshold KE.

The emergency control executed by the power management unit 42 of the motor control device 40 will be described.
In the emergency control, the motor control device 40 changes the charge / discharge circuit 54 from the first power supply form to the second power supply form when the vehicle 1 urgently avoids the collision avoidance target (hereinafter referred to as “emergency avoidance”). . Specifically, the motor control device 40 changes the DUTY ratio of the switching element 54A from 0% to 100%. The motor control device 40 determines whether or not it is an emergency avoidance based on the relative distance DA and the relative speed VA by the external environment detection device 5 and the steering speed ω. Specifically, the motor control device 40 determines that the emergency avoidance is performed when the relative distance DA is equal to or less than the reference relative distance KD, the relative speed VA is equal to or greater than the reference relative speed KV, and the steering speed ω is equal to or greater than the reference steering speed Kω. .

  Note that the reference relative distance KD is a distance between the vehicle 1 and the collision avoidance object that is recognized that the vehicle 1 needs to urgently avoid the collision avoidance object. The reference relative distance KD is set in advance by a test or the like. The reference relative speed KV is a relative speed between the vehicle 1 and the collision avoidance object that is recognized that the vehicle 1 needs to urgently avoid the collision avoidance object when the relative distance DA is the reference relative distance KD. The reference relative speed KV is preset by a test or the like. The reference steering speed Kω is a steering speed when the vehicle 1 urgently avoids the collision avoidance target. The reference steering speed Kω is preset by a test or the like.

  In the emergency control, the motor control device 40 controls the discharge of the auxiliary power supply 55 as follows based on the urgency (hereinafter referred to as “emergency DX”) for the vehicle 1 to avoid the collision avoidance target. That is, the motor control device 40 changes the DUTY ratio of the switching element 54A to 100% more quickly when the emergency degree DX is higher than when the emergency degree DX is low. Specifically, the motor control device 40 directly changes the DUTY ratio of the switching element 54A from 0% to 100% when the urgency DX is high. When the degree of urgency DX is low, the motor control device 40 changes the DUTY ratio of the switching element 54A from 0% to 100% with a predetermined increase width. Note that the increase width of the DUTY ratio of the switching element 54A is equal to the increase width of the DUTY ratio of the switching element 54A that is normally controlled.

  Hereinafter, the discharge form of the auxiliary power supply 55 that directly changes the DUTY ratio of the switching element 54A from 0% to 100% will be referred to as a “first discharge form”. Further, a discharge form of the auxiliary power supply 55 that gradually changes the DUTY ratio of the switching element 54A from 0% to 100% with a predetermined increase width is shown as a “second discharge form”. The amount that the auxiliary power supply 55 discharges to the electric motor 31 per unit time in the first discharge mode (hereinafter, “discharge rate”) is higher than the discharge rate of the auxiliary power supply 55 in the second discharge mode.

With reference to FIG. 3, the determination of the degree of urgency DX by the power management unit 42 (both see FIG. 2) of the motor control device 40 will be described.
The motor control device 40 determines the degree of urgency DX based on a map MP indicating the relationship between the time when the vehicle 1 reaches the collision avoidance target (hereinafter, “collision time TC”) and the steering speed ω. The map MP is an emergency region RD formed by a range equal to or shorter than a collision time (hereinafter referred to as “reference collision time TX”) calculated based on the reference relative distance KD and the reference relative speed KV and a range equal to or higher than the reference steering speed Kω. Have The emergency region RD is divided into a region having a high emergency level DX (hereinafter, “high emergency level region RU”) and a region having a low emergency level DX (hereinafter, “low emergency level region RL”).

  The motor control device 40 calculates the collision time TC based on the relative distance DA and the relative speed VA. Then, the motor control device 40 determines that the urgency DX is high when the coordinates of the collision time TC and the steering speed ω are within the high urgency region RU in the map MP. The motor control device 40 determines that the urgency DX is low when the coordinates of the collision time TC and the steering speed ω are within the low urgency region RL.

  The operation of the EPS 10 will be described with reference to FIGS. “Comparative EPS” indicates a configuration in which emergency control is omitted from power control of the motor control device 40 of the EPS 10. In addition, the electric motor, the charge / discharge circuit, the auxiliary power supply, and the switching element for discharging the auxiliary power supply constituting the comparative EPS are referred to as “comparative electric motor”, “comparative charge / discharge circuit”, “comparative auxiliary power supply”, and “ It is shown as “comparative switching element”.

  The comparative EPS is set to the second power supply mode when the power supply power is equal to or higher than the charge / discharge threshold value KE. However, since the comparative EPS does not have emergency control, the comparative charging / discharging circuit is not always set to the second power supply mode during emergency avoidance. Specifically, in the comparative EPS, when the power supply power is less than the charge / discharge threshold KE, the comparative charge / discharge circuit maintains the first power supply configuration even during emergency avoidance. That is, the comparative EPS does not set the comparative charging / discharging circuit to the second power supply mode unless the power supply power becomes equal to or higher than the charging / discharging threshold value KE during emergency avoidance. For this reason, in comparative EPS, it may be difficult to appropriately supply electric power to the comparative electric motor during sudden steering for emergency avoidance.

  In addition, when the comparative charge / discharge circuit is changed from the first power supply configuration to the second power supply configuration, the comparative EPS gradually increases the DUTY ratio of the comparative switching element with a predetermined increase width. For this reason, in the comparative EPS, particularly when the urgency degree DX is high, the motor drive voltage applied to the comparative electric motor gradually rises even though the urgency degree DX is high. For this reason, it may be difficult to quickly supply the power of the comparative auxiliary power source to the comparative electric motor.

  In the comparative EPS, when the comparative charging / discharging circuit is changed from the first power supply form to the second power supply form, the motor drive voltage is increased as the difference between the power supply power and the charge / discharge threshold value KE increases. For this reason, in the comparative EPS, particularly when the urgency degree DX is high, the motor drive voltage applied to the comparison electric motor is determined when the power supply power is slightly larger than the charge / discharge threshold KE even though the urgency degree DX is high. The rise is small. Therefore, the power supplied to the comparative electric motor may be insufficient.

  On the other hand, the EPS 10 of this embodiment changes from normal control to emergency control when emergency avoidance is performed by power control. Thereby, EPS10 sets the charging / discharging circuit 54 to a 2nd power supply form at the time of emergency avoidance. For this reason, in the EPS 10, electric power is supplied from the auxiliary power supply 55 to the electric motor 31 during sudden steering for emergency avoidance. Accordingly, the EPS 10 can appropriately supply power to the electric motor 31 during emergency avoidance.

  In addition, when the emergency degree DX is high, such as when the collision time TC is short and the steering speed ω is high during emergency avoidance, the EPS 10 directly changes the DUTY ratio of the switching element 54A from 0% to 100% (first discharge) Form). Thereby, the electric power of the auxiliary power supply 55 is promptly supplied to the electric motor 31. For this reason, the motor drive voltage VMD rises rapidly. Further, the motor drive voltage VMD increases to the maximum value. Therefore, a shortage of power supplied to the electric motor 31 is suppressed.

  On the other hand, when the emergency degree DX is low, such as when the collision time TC is long and the steering speed ω is low during emergency avoidance, the EPS 10 gradually increases the DUTY ratio of the switching element 54A within a predetermined increase range (second discharge). Form). Thereby, the motor drive voltage VMD rises gently. For this reason, even at the time of emergency avoidance, when the emergency degree DX is low, a rapid change in the assist torque TA is suppressed.

  With reference to FIG. 4, the process sequence of the power supply control by the motor control apparatus 40 is demonstrated. The power control is repeatedly executed every predetermined time. In the following description with reference to FIG. 4, each component of the vehicle 1 denoted by a reference sign indicates each component of the vehicle 1 described in FIG. 2.

  The motor control device 40 determines whether or not emergency avoidance is in step S11. When an affirmative determination is made in step S11, that is, during emergency avoidance, the motor control device 40 executes emergency control after step S12. On the other hand, when a negative determination is made in step S11, that is, when it is not during emergency avoidance, the motor control device 40 executes normal time control after step S21.

  In emergency control, the motor control device 40 sets the charge / discharge circuit 54 to the second power supply mode in step S12. Then, the motor control device 40 determines whether or not the emergency degree DX is high in step S13. When an affirmative determination is made in step S13, the motor control device 40 sets the discharge form of the auxiliary power supply 55 to the first discharge form in step S14. On the other hand, when a negative determination is made in step S13, the motor control device 40 sets the discharge form of the auxiliary power supply 55 to the second discharge form in step S15.

  In the normal control, the motor control device 40 determines whether or not the power supply PS is greater than or equal to the charge / discharge threshold KE in step S21. When a negative determination is made in step S21, the motor control device 40 sets the charge / discharge circuit 54 to the first power supply mode in step S22.

  If the determination in step S22 is affirmative, the motor control device 40 sets the charge / discharge circuit 54 to the second power supply configuration in step S23. In step S24, the motor control device 40 calculates the DUTY ratio of each switching element 54A, 54B from the difference between the power source PS and the charge / discharge threshold KE. In step S25, the motor control device 40 executes PWM driving of the switching elements 54A and 54B in accordance with the DUTY ratio of the switching elements 54A and 54B.

The EPS 10 of the present embodiment has the following effects.
(1) The motor control device 40 of the EPS 10 sets the charge / discharge circuit 54 to the second power supply mode at the time of emergency avoidance. Therefore, it is avoided that the charge / discharge circuit 54 is not changed from the first power supply form to the second power supply form at the time of emergency avoidance as compared with the power supply control of the comparative EPS. Therefore, electric power is appropriately supplied to the electric motor 31 during emergency avoidance.

  (2) The motor control device 40 changes from normal control to abnormal control during emergency avoidance. According to this configuration, the charge / discharge circuit 54 is changed from the first power supply form to the second power supply form even when the power supply power PS is less than the charge / discharge threshold KE during emergency avoidance. Accordingly, the EPS 10 appropriately supplies power to the electric motor 31 at the time of emergency avoidance as compared with the power control of the comparative EPS. Further, the EPS 10 promptly changes the charge / discharge circuit 54 from the first power supply configuration to the second power supply configuration when the power supply PS is sufficiently smaller than the charge / discharge threshold KE during emergency avoidance, as compared with the power control of the comparative EPS. Can be changed.

  (3) The motor control device 40 sets the auxiliary power supply 55 in the first discharge mode when the urgency level DX is high, and sets the auxiliary power supply 55 in the second discharge mode when the urgency level DX is low. According to this configuration, when the degree of urgency DX is high, a shortage of power supplied to the electric motor 31 is suppressed by rapidly increasing the motor drive voltage VMD. When the urgency DX is low, a rapid change in the assist torque TA is suppressed by gradually increasing the motor drive voltage VMD. For this reason, even at the time of emergency avoidance, if the emergency degree DX is low, it is possible to prevent the driver from being given a steering feeling that gives a sense of incongruity due to a sudden change in the assist torque TA.

  (4) The motor control device 40 gradually increases the DUTY ratio of the switching element 54A within a predetermined increase width when the charge / discharge circuit 54 changes from the first power supply form to the second power supply form in the normal control. . According to this configuration, when the charge / discharge circuit 54 is changed from the first power supply form to the second power supply form, the DUTY ratio of the switching element 54A is directly changed from 0% to 100%. Thus, the motor drive voltage VMD is suppressed from increasing rapidly. Therefore, during the normal operation of the vehicle 1, since a sudden change in the assist torque TA is suppressed, it is possible to suppress the driver from being given a steering feeling that gives a sense of discomfort due to the sudden change in the assist torque TA. The

  The electric power steering apparatus includes an embodiment different from the above embodiment. Hereinafter, the modification of the said embodiment as other embodiment of this electric power steering device is shown. The following modifications can be combined with each other.

  In the motor control device 40 of the embodiment, the relative distance DA and the relative speed VA of the external environment detection device 5 are input. The motor control device 40 according to the embodiment determines whether or not emergency avoidance is based on the relative distance DA, the relative speed VA, and the steering speed ω. However, the determination of whether or not it is during emergency avoidance is not limited to the content exemplified in the embodiment. For example, as shown in FIG. 5, the modified motor control device 40 determines whether or not emergency avoidance is based on an emergency avoidance instruction signal of the vehicle control device 8 formed separately from the motor control device 40. . Specifically, the modified external environment detection device 5 inputs a signal including the relative distance DA and the relative speed VA to the vehicle control device 8. Further, the steering angle sensor 70 of the modified example inputs a steering signal to the vehicle control device 8. The vehicle control device 8 calculates the steering angle θ based on the steering angle signal. Then, the vehicle control device 8 calculates the steering speed ω based on the steering angle θ. The vehicle control device 8 determines whether or not it is during emergency avoidance based on the relative distance DA, the relative speed VA, and the steering speed ω. When the vehicle control device 8 determines that it is during emergency avoidance, the vehicle control device 8 outputs an emergency avoidance instruction signal to the motor control device 40 of the modified example. When the motor control device 40 according to the modified example receives the emergency avoidance instruction signal, the motor control device 40 determines that the emergency avoidance is in progress.

  The motor control device 40 of the embodiment sets the charge / discharge circuit 54 to the second power supply mode when the power supply power PS is equal to or higher than the charge / discharge threshold KE in the normal control, and the power supply power PS is less than the charge / discharge threshold KE At this time, the charge / discharge circuit 54 is set to the first power supply mode. However, the setting of each power supply mode of the charge / discharge circuit 54 is not limited to the content exemplified in the embodiment. For example, the motor control device 40 of the modified example sets the charge / discharge circuit 54 to the second power supply mode when the main power supply 4 fails in the normal control, and the charge / discharge circuit when the main power supply 4 does not fail. 54 is set to the first power supply configuration. The failure of the main power supply 4 includes that the battery current IB becomes “0” and the output voltage V1 drops suddenly even though the motor drive circuit 44 is operating.

  The motor control device 40 of the embodiment determines whether or not the emergency level DX is high based on a map indicating the relationship between the collision time TC, the steering speed ω, and the emergency level DX. However, the determination of the urgency DX is not limited to the content exemplified in the embodiment. For example, the motor control device 40 according to the modified example determines that the degree of urgency DX is high when the collision time TC is equal to or less than a preset collision time. The set collision time is shorter than the reference collision time TX. Further, the motor control device 40 of another modified example determines that the degree of urgency DX is high when the steering speed ω is equal to or higher than a preset set steering speed. The set steering speed is higher than the reference steering speed Kω.

  The motor control device 40 according to the embodiment determines the urgency DX based on the collision time TC and the steering speed ω. However, the determination of the urgency DX is not limited to the content exemplified in the embodiment. For example, the modified motor control device 40 determines the emergency DX based on the vehicle speed V, the relative distance DA, and the steering speed ω. Specifically, the motor control device 40 of the modified example determines that the vehicle is in emergency avoidance when the vehicle speed V is equal to or greater than the reference travel speed VX, the relative distance DA is equal to or less than the reference relative distance KD, and the steering speed ω is equal to or greater than the reference steering speed Kω. To do. The reference travel speed VX is a vehicle speed that is recognized as the vehicle 1 that needs to be urgently avoided when the relative distance DA is the reference relative distance KD. The reference traveling speed VX is set in advance by a test or the like.

  The motor control device 40 according to another modification is configured such that when the external environment detection device 5 determines that there is a collision avoidance object ahead of the vehicle 1 in the vehicle traveling direction, the vehicle speed V is equal to or higher than the reference travel speed VX. When the steering speed ω is equal to or higher than the reference steering speed Kω, it is determined that emergency avoidance is in progress.

  -The motor control apparatus 40 of embodiment changes the discharge rate of the auxiliary power supply 55 based on the emergency DX. However, the operation of the auxiliary power supply 55 based on the urgency DX is not limited to the content exemplified in the embodiment. For example, the motor control device 40 according to the modified example changes the total amount (hereinafter, “discharge amount”) that the auxiliary power supply 55 discharges to the electric motor 31 based on the urgency DX. Specifically, the motor control device 40 according to the modified example changes the DUTY ratio of the switching element 54A from 0% to 50% when the urgency DX is low. The motor control device 40 according to the modified example changes the DUTY ratio of the switching element 54A from 0% to 100% when the urgency DX is high. For this reason, in the motor control device 40 of the modified example, the discharge amount when the urgency level DX is high is larger than the discharge amount when the urgency level DX is low. Note that the DUTY ratio of the switching element 54A when the urgency DX is low may be a value other than 50%. In addition, the motor control device 40 according to another modified example changes both the discharge speed and the discharge amount of the auxiliary power supply 55 based on the urgency DX.

  The motor control device 40 of the embodiment variably sets the motor drive voltage VMD based on the difference between the power source power PS and the charge / discharge threshold value KE when the power source power PS is greater than or equal to the charge / discharge threshold value KE. However, the motor drive voltage VMD when the power source power PS is equal to or higher than the charge / discharge threshold KE is not limited to the content exemplified in the embodiment. For example, the modified motor control device 40 sets the motor drive voltage VMD to a constant value when the power source power PS is equal to or greater than the charge / discharge threshold KE.

  -EPS10 of embodiment has the electric motor 31 as a three-phase brushless motor. However, the configuration of the electric motor 31 is not limited to the content exemplified in the embodiment. For example, the EPS 10 according to the modification has a brush motor instead of a three-phase brushless motor as the electric motor 31.

  When the charge / discharge circuit 54 is changed from the first power supply form to the second power supply form, the motor control device 40 according to the embodiment sets the DUTY ratio of the switching element 54A to a predetermined value from the state where the DUTY ratio of the switching element 54A is 0%. It gradually increases with the increase. However, the operation of the switching element 54A when the charge / discharge circuit 54 is changed from the first power supply form to the second power supply form is not limited to the contents exemplified in the embodiment. For example, the modified motor control device 40 changes the DUTY ratio of the switching element 54A from the 0% state to a predetermined DUTY ratio. Further, the motor control device 40 of another modification changes the DUTY ratio of the switching element 54A from 0% to 100%.

  In the charge / discharge circuit 54 of the embodiment, MOSFETs are employed as the switching elements 54A and 54B. However, the types of the switching elements 54A and 54B are not limited to the contents exemplified in the embodiment. For example, the charging / discharging circuit 54 according to the modified example employs switching elements having other configurations such as IGBTs as the switching elements 54A and 54B.

In the EPS 10 of the embodiment, a plurality of auxiliary power supplies 55 may be provided.
The auxiliary power supply device 50 of the embodiment has an auxiliary power supply 55 as a capacitor. However, the configuration of the auxiliary power supply device 50 is not limited to the content exemplified in the embodiment. For example, the auxiliary power supply device 50 according to the modification includes a secondary battery such as a lithium ion battery instead of the capacitor as the auxiliary power supply 55.

  In the embodiment, the auxiliary power supply 55 employs an electric double layer capacitor. However, the type of the auxiliary power supply 55 is not limited to the content exemplified in the embodiment. For example, the auxiliary power supply 55 according to the modified example employs a lithium ion capacitor instead of the electric double layer capacitor.

Next, technical ideas that can be grasped from the above embodiment will be described.
(A) The motor control device includes a relative distance between the vehicle and an emergency avoidance target that the vehicle needs to avoid urgently, a relative speed between the vehicle and the emergency avoidance target, and the steering component. The electric power steering apparatus according to any one of claims 1 to 3, wherein it is determined whether or not the vehicle is to be urgently avoided based on a steering speed based on steering.

  (B) The motor control device determines the degree of urgency based on a time until the vehicle reaches an emergency avoidance target that the vehicle needs to avoid and a steering speed based on steering of the steering component. The electric power steering apparatus according to claim 3 for determination.

  τ ... steering torque, DX ... emergency, KE ... charge / discharge threshold, PS ... power supply power, TA ... assist torque, 1 ... vehicle, 2 ... steering components, 4 ... main power supply, 10 ... EPS (electric power steering device), 31 ... Electric motor, 40 ... Motor controller, 55 ... Auxiliary power supply.

Claims (2)

An electric motor for generating an assist torque for assisting steering of the steering component based on the steering torque;
An auxiliary power source connected to a main power source for supplying power to the electric motor and capable of discharging to the electric motor;
A motor control device that switches between a first power supply mode that supplies power from the main power supply to the electric motor, and a second power supply mode that supplies power from the main power supply and the auxiliary power supply to the electric motor;
The motor control device
The collision avoidance object is determined based on at least one of the collision time and the steering speed, which is the time for the vehicle to reach the collision avoidance object, or based on the vehicle speed, the relative distance between the vehicle and the collision avoidance object, and the steering speed. Determine if the urgency to avoid is high or low,
When the vehicle emergency avoidance, the second has an emergency control to set the power mode, at high the urgency of emergency avoidance of the vehicle, the electric power steering device for increasing the discharge speed of the auxiliary power supply. The motor control device is a reference for switching power source power of the electric power steering device consumed by assist control for assisting steering from charging to the auxiliary power source from the main power source and discharging from the auxiliary power source to the electric motor. When the value is equal to or higher than the charge / discharge threshold value, it has normal time control to change from the first power supply form to the second power supply form
The electric power steering apparatus according to claim 1, wherein when the vehicle avoids an emergency, the normal control is changed to the emergency control.