JP2011102093A - Booster - Google Patents

Abstract

An object of the present invention is to provide a high-commercial voltage booster that eliminates the need to limit the output more than necessary by reducing the control gain for boosting according to this current when excessive current flows transiently. To do.
An input limiting current value (Iin) that becomes a limiting value of an input current value (Iin) according to a state quantity of a booster circuit (130) from a target current value (Iobj) set based on a request value on a load side. Iinmax) is set, a feedback control gain (Pv) of the output voltage value (Vout) is calculated according to the input current value (Iin) and the input limited current value (Iinmax), and is output to the control means (120). Correction means (110). This correction means (110) corresponds to the target voltage value (Vobj) as the difference (ΔIin) between the input current value (Iin) and the input limit current value (Iinmax) becomes smaller than the predetermined values (ΔIinA, ΔIinB). The feedback control gain (Po) is reduced.
[Selection] Figure 1

Description

  The present invention relates to a booster device that includes a booster circuit that boosts a voltage input from a power supply voltage and controls boosting.

  The DC booster circuit (DC-DC converter) is composed of an electronic switch, a diode, an inductance, a capacitor, and the like, and controls to convert the primary side voltage to a higher output voltage. Many electric components are installed in recent automobiles (hereinafter referred to as “vehicles”), and boosting the voltage leads to miniaturization and weight reduction of parts and wiring. It plays an important role. As an electrical component, for example, there is a rack and pinion type electric power steering device (hereinafter referred to as “EPS” (Electric Power Steering)). This EPS is equipped with an electric motor, and a DC-DC converter is mounted on a vehicle. The voltage of the battery or generator is boosted to supply power to the motor.

  However, when the battery is deteriorated, a large current flows through the electric motor of the EPS and the battery voltage is greatly reduced, and there is a possibility that the operation of the EPS is stopped or the power supply system of the entire automobile is down (see Patent Document 1).

  In view of this situation, in the output control of the conventional DC-DC converter, the upper limit value of the output current is set according to the specification of the DC-DC converter, and when the output current exceeds the set upper limit value, the output is A technique for limiting the above is disclosed. This output restriction is provided to prevent the DC-DC converter from being overloaded and the power supply source from being overloaded.

JP 2007-151247 A

  However, in general, the predetermined processing interval in the rack and pinion type EPS is about 0.5 ms as one cycle. The steering operation that hits the rack end is performed, and an excessive current flows transiently for about 3 ms, and approximately six processes are executed. Under such circumstances, with the technique disclosed in Patent Document 1, there is a risk that the upper limit value of the output current may not be in time. Further, if the current is limited only by setting a certain upper limit value, the current changes in the vicinity of the upper limit value, and the circuit element may be overheated. Furthermore, in the control that limits the upper limit value of the output current, when excessive current flows transiently, it is assumed that power supply shortage may occur temporarily, and the control process may be reset depending on the magnitude of power supply shortage. There is also a risk.

  A power supply system such as a DC-DC converter usually includes a large-capacity capacitor, and a current charged in the capacitor flows. Therefore, the current flowing from the capacitor can be determined only by limiting the output current. There is a possibility that it cannot be restricted.

A battery and a small generator are applied to a power supply source (primary power source) of a DC-DC converter mounted on an automobile. Since the steering operation that hits the rack end is not performed when the vehicle is traveling normally, the battery is dominant in the power supply source at this time. For this reason, if more power than expected is taken from the primary power supply, there is a risk of battery voltage drop or fuse fusing, affecting other systems or the operation of the DC-DC converter itself. May give. As described above, in the output control of the conventional DC-DC converter, in a system that requires a transient output, shortage of power supply or the like temporarily occurs, and the merchantability of the control device using the DC-DC converter. There was a risk of adverse effects.

  The present invention has been made in view of the above-described background, and has a highly productive booster (DC-DC converter) that does not limit the output of the DC-DC converter more than necessary when excessive current flows transiently. ).

  The present invention relates to a booster (100) that boosts an input voltage and outputs the boosted voltage to a connected load (M). The device includes a booster circuit (130) that boosts the input voltage, and feedback control of an output voltage value (Vout) from the booster circuit (130) to control the output voltage value (Vout) to the load (M). Control means (120) for controlling the boost value of the booster circuit (130) so as to approach the target voltage value (Vobj) set based on the request, and an input current value (Iin) to at least the booster circuit (130) ) Including a state quantity detection means (102) for detecting a state quantity of the booster circuit (130), a target current value (Iobj) set based on the required value on the load side, and the detected state quantity Current setting means (101) for setting an input limiting current value (Iinmax) which is a limiting value of the input current value (Iin), and the detected input current value (Iin) Correction means for calculating a feedback control gain (Pv) of the output voltage value (Vout) according to a difference (ΔIin) from the determined input limit current value (Iinmax) and outputting the feedback control gain (Pv) to the control means (120) 110). The correction means (110) is configured to decrease the feedback control gain (Po) corresponding to the target voltage value (Vobj) as the difference (ΔIin) becomes smaller than a predetermined value (ΔIinA, ΔIinB). ing.

  According to the above configuration, feedback control is performed when a transient current increase approaches the input limit current value according to the difference between the input current value and the input limit current value set based on the load-side required value. Since the gain is lowered, the problem that the current limit is not in time as in the prior art can be solved. Here, since the input current value is a basic element of the boost control circuit, the addition of a new circuit can be avoided, and a low-cost and space-saving boost device can be realized.

  In addition, according to the above configuration, since the control gain is reduced only when a large current flows, the rapid fluctuation of the input current is reduced. This prevents an excessive current from flowing in the element that controls the input current, so that it is possible to avoid applying an excessively rated element and to reduce the fuse capacity that prevents the input current from overshooting. it can. Therefore, it is possible to provide a stable booster at low cost without changing the basic booster circuit configuration.

  Further, according to the above configuration, the control gain is not operated until the difference between the input current value and the input limit current value reaches a predetermined value, so that normal responsiveness is maintained until near the current value that needs to be controlled. Since the control gain is decreased as the difference becomes smaller thereafter, an excessive input current can be prevented while maintaining the responsiveness.

  In the configuration, the state quantity includes a characteristic of the load, an output current value (Iout), and a temporal change of the output current value, and the current setting unit (101) includes the characteristics of the load, and It is preferable that the input limit current value (Iinmax) is set based on at least one of the output current value (Iout) and / or the temporal change of the output current value, or both.

  According to the above configuration, the input limiting current value is set from the load characteristics, the actual output current value, the slope obtained from the temporal change in the output current value, etc., so that the control gain can be reduced at an appropriate time. it can. Here, the load characteristic is, for example, EPS mounted on a vehicle. In addition to basic steering characteristics such as electric motor characteristics, steering gear ratio, and variable gear ratio, load such as friction as a whole EPS accompanying steering Is also included. The required value of the axial force of the EPS motor is set in consideration of such load characteristics, and the input current can be estimated based on the required value of the axial force.

  In the above configuration, the correction means (110) calculates a correction coefficient (ki, 112) corresponding to the difference between the input current value and the input limited current value based on a preset map, and this correction coefficient It is preferable that the correction is performed by multiplying the feedback control gain (Po) by (ki).

According to the above configuration, since the map can be set according to the characteristics of the system in which the booster is mounted, a stable booster can be provided at low cost without changing the basic booster configuration. Can do.

  The present invention also provides a booster (200) that boosts an input voltage and outputs the boosted voltage to a connected load (M), the booster circuit (230) that boosts the input voltage, and the booster circuit (230). The boost voltage value of the booster circuit (230) is controlled so that the output voltage value (Vout) from the feedback circuit is feedback-controlled so that the output voltage value approaches the target voltage value (Vobj) set based on a request for the load (M). Control means (220) for controlling the state, state quantity detection means (202) for detecting a state quantity of the booster circuit (230) including at least an output current value (Iout) from the booster circuit (230), and the load Output limit current value (Iout) which becomes a limit value of the output current value (Iout) from the target current value (Iobj) set based on the requested value on the side and the detected state quantity bj) and the output voltage value (Vout) according to the difference (ΔIout) between the detected output current value (Iout) and the set output limit current value (Ioutobj). And a correction means (220) for calculating the feedback control gain (Pv) and outputting the feedback control gain (Pv) to the control means. The correction means (220) has a difference (ΔIout) smaller than a predetermined value (ΔIoutA, ΔIoutB). Accordingly, the feedback control gain (Po) corresponding to the target voltage value (Vobj) can be reduced.

  In the configuration, the state quantity includes a characteristic of the load (M), the detected output current value (Iout), and a temporal change of the output current value, and the current setting unit (201) includes: The input limit current value (Ioutobj) is set based on at least one of the output current value (Iout) and the temporal change in the output current value, or both state quantities together with the characteristics of the load (M). It can also be configured.

  In the above configuration, the correction means (210) calculates a correction coefficient (kout, 212) according to a difference between the output current value (Iout) and the output limit current value (Ioutobj) based on a preset map. The correction may be performed by calculating and multiplying the feedback control gain (Po) by the correction coefficient (kout).

  The load (M) of the present invention may be a steering assist electric motor (11) of an electric power steering device (1) mounted on a vehicle and driven and controlled in accordance with a driver's steering input.

  In the above-described configuration, the electric power steering apparatus includes a steering angle detection unit that detects a steering angle, and the required value on the load side is estimated from the detected steering angle and a steering direction. can do.

  ADVANTAGE OF THE INVENTION According to this invention, when an excessive electric current flows transiently, the booster (DC-DC converter) with high commercial property which does not restrict | limit an output more than necessary can be provided.

It is a block diagram which shows the structure of the pressure | voltage rise apparatus concerning 1st Embodiment of this invention. It is a flowchart which shows the process of control concerning 1st Embodiment of this invention. It is a key map of control concerning a 1st embodiment of the present invention. It is a block diagram which shows the structure of the pressure | voltage rise apparatus concerning 2nd Embodiment of this invention. It is a flowchart which shows the process of control concerning 2nd Embodiment of this invention. It is a schematic block diagram of the electric power steering apparatus provided with the pressure | voltage rise apparatus concerning 3rd Embodiment of this invention. It shows an example of the load characteristic in the electric power steering apparatus provided with the booster according to the third embodiment of the present invention, and shows the axial force required for the motor and the input current that generates this axial force. Showing the relationship.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Referring to FIG. 1, a booster 100 according to the present embodiment includes a state quantity detection unit (state quantity detection unit) 102, a current setting unit (current setting unit) 101, a correction unit (correction unit) 110, and a control. Section (control means) 120 and a booster circuit 130. When the booster 100 is mounted on a vehicle, the state quantity detection unit 102, the current setting unit 101, the correction unit 110, and the control unit 120 are electronic control units (hereinafter referred to as “ECUs” (hereinafter referred to as “ECUs”). Electronic Control Unit)). The ECU is a kind of computer, and includes a processor (hereinafter referred to as “CPU”) that executes computation, a storage area that temporarily stores various data, and a random access memory (hereinafter referred to as “working area” for computation by the processor). RAM ”), a read-only memory (hereinafter referred to as“ ROM ”) in which various programs used by the processor and various data used for computations are stored in advance, and results of computations by the processor and each part of the engine system A rewritable nonvolatile memory for storing data to be stored is provided. The nonvolatile memory can be realized by a RAM with a backup function that is always supplied with a voltage even after the system is stopped.

  The booster circuit 130 includes a series circuit of a coil L and a second switching element SW2 disposed between the battery B and an externally connected load M, and the coil between the coil L and the second switching element SW2. A first switching element SW1 is provided for passing an exciting current to L and shutting it off. As the first and second switching elements SW1 and SW2, transistors (for example, MOS-FETs) can be used. The output side of the second switching element SW2 is grounded via a capacitor C.

  A PWM (Pulse width modulation) output unit 124 of the control unit 120, which will be described later, converts the duty ratio Duty (n) set by the control unit 120 into a duty ratio drive signal, and outputs the first and second switching elements. Send to SW1 and SW2. The switching operation of the booster circuit 130 is performed by PWM control based on the duty ratio Duty (n), energy is accumulated and released in the coil L, and the output side of the second switching element SW2 has a high voltage at the time of emission. It becomes. When the high voltage is repeatedly generated, the capacitor C is charged, and a boosted voltage is obtained and output to the load M. The configuration of the booster circuit 130 is an example, and is not limited to such a configuration. For example, a diode may be applied to the second switching element SW2.

  A current sensor P1 is disposed between the battery B and the coil L to send a signal corresponding to the detected current, and a voltage application point P2 is applied to the connection point between the capacitor C and the load M of the booster circuit 130. Is provided for voltage detection.

  In addition to the signals from the current sensor P1 and the voltage application point P2, the state quantity detection unit 102 acquires the output current value from the booster circuit 130 and the characteristics of the load M by a current sensor (not shown). Here, the characteristics of the load M are, for example, the characteristics of the current and voltage of a motor such as a two-phase, three-phase, and brushless, and include the load state and loss when actually mounted on the system. is there. In addition, a current gradient that is a temporal change in the output current value is calculated. The state quantity acquired or calculated by the state quantity detection unit 102 is sent to the current setting unit 101 as a signal.

  The current setting unit 101 acquires and reads the target current value Iobj and the signal sent from the state quantity detection unit 102. The target current value Iobj is set, for example, when the above-described ECU detects a request for the load M to the booster 100 using a communication means such as an in-vehicle network (CAN: Controller Area Network). The current setting unit 101 calculates the input current limit value Iinmax from the target current value Iobj, the characteristics of the load M sent from the state quantity detection unit 102, the temporal change of the output current value, the current value of the output current value, and the like. And sent to the correction unit 110. With this configuration, the input current limit value Iinmax can be set according to the system characteristics.

  In the calculator 111, the correction unit 110 subtracts the input current value Iin sent from the current sensor P1 from the input current limit value Iinmax to calculate a difference ΔIin (absolute value). The coefficient k calculation unit 112 of the correction unit 110 calculates a correction coefficient ki for correcting the voltage control gain based on the difference ΔIin. The relationship between the difference ΔIin and the correction coefficient ki can be set in advance and stored in a memory as a map as shown as an example in the figure.

  Referring to the illustrated map, as the difference ΔIin becomes smaller than the predetermined values ΔIinA and ΔIinB and approaches 0, the correction coefficient ki changes so as to decrease the voltage control gain. That is, when the difference ΔIin is large, the correction coefficient ki is set to 1 to compensate for the shortage, and the correction coefficient ki is made smaller as the difference ΔIin becomes smaller. This map is an example, and the map can be set as appropriate according to the characteristics of the system in which the booster is mounted.

  Next, the correction unit 110 corrects the basic control gain Po by multiplying the basic control gain Po by the correction coefficient ki and calculates the feedback control gain Pv. The calculated feedback control gain Pv is sent to the control unit 120. Here, the basic control gain Po is, for example, a feedback control gain set by the ECU based on load characteristics and the like.

  The control unit 120 acquires signals of the target voltage value Vobj, the feedback control gain Pv sent from the correction unit 110, and the output voltage value Vout detected at the voltage application point P2. Here, the target voltage value Vobj is set, for example, when the above-described ECU detects a required value of the load on the booster 100 using a communication unit such as an in-vehicle network.

  The control unit 120 calculates a difference between the target voltage value Vobj and the output voltage value Vout in the calculator 121, and calculates Pv × (Vobj−Vout) obtained by multiplying the difference by the feedback control gain Pv in the calculator 122. The arithmetic unit 123 sets the duty ratio Duty (n) corrected by adding to the duty ratio Duty (n−1) which is the previous value. The PWM output unit 124 converts the corrected duty ratio Duty (n) into a duty ratio drive signal and sends it to the first and second switching elements SW1 and SW2. Note that the duty ratio Duty (n−1) that is the previous value can be stored in the memory.

  With this configuration, the booster 100 according to the present embodiment can realize a low-cost, space-saving and stable booster by controlling the control gain for boosting with the input current to the booster circuit 130.

  Next, an example of the correction process according to the present embodiment will be described with reference to FIG. 2. Since this process overlaps with the description of the apparatus configuration described above, a brief description will be given. Specifically, these processes can be realized by the state quantity detection unit 102, the current setting unit 101, the correction unit 110, and the control unit 120. If it is the pressure | voltage rise apparatus 100 mounted in the vehicle, these processes can be stored as a program in the memory of ECU, for example, and it can be comprised so that it may be repeatedly performed with a predetermined | prescribed process interval.

  Referring to FIG. 2, the current setting unit 101 reads the target current value Iobj set by the ECU or the like (step S201), and the target current value Iobj and the characteristics of the load M sent from the state quantity detection unit 102, The input current limit value Iinmax is calculated from the temporal change of the output current value, the current value, and the like (step S202).

  Subsequently, the correction unit 110 calculates the difference ΔIin by subtracting the input current value Iin sent from the current sensor P1 from the input current limit value Iinmax (step S203), and the coefficient k calculation unit 112 is based on the difference ΔIin. Thus, a correction coefficient ki for correcting the voltage control gain is calculated (step S204). Next, the correction unit 110 corrects the basic control gain Po by multiplying the basic control gain Po by the correction coefficient ki, and calculates the feedback control gain Pv (S205). Here, as shown in FIG. 1, the correction coefficient ki is set to 1 when the difference ΔIin is larger than the predetermined values ΔIinA and ΔIinB, and becomes smaller as the difference ΔIin becomes smaller than the predetermined values ΔIinA and ΔIinB. It can be calculated using a map that changes as follows. The predetermined values ΔIinA and ΔIinB are appropriately set depending on the system.

  Subsequently, the control unit 120 calculates a difference between the target voltage value Vobj and the output voltage value Vout, calculates Pv × (Vobj−Vout) obtained by multiplying the difference by the feedback control gain Pv, and becomes the previous value. The duty ratio Duty (n) corrected by adding to the duty ratio Duty (n-1) is set (step S206), and this process is terminated.

  Next, with reference to FIG. 3, a difference between one embodiment to which the present process is applied and a comparative example to which conventional control is applied will be described. FIG. 3 shows a time chart of current and voltage when an excessive current suddenly flows. For example, in a rack-and-pinion type EPS, a steering operation that hits the rack end is performed, and the excessive current becomes transient. Corresponds to the case of flowing into Although the unit of time on the horizontal axis is not shown in FIG. 3, the current may rise on the order of several microseconds (μsec).

  First, referring to a comparative example to which conventional control is applied, since the control gain is high when the current rises, the amount of overshoot of the current is large, and accordingly, the voltage drop is also large. Depending on the magnitude of this voltage shortage, the control process may be reset. In addition, when the limit is performed when a constant current value is reached as in Patent Document 1, it is difficult to follow a sudden current increase, and the limited current changes in the vicinity of the upper limit value. As a result, the circuit elements may be heated.

  Next, referring to the embodiment, the control gain is the same as the control using the basic control gain Po so as to compensate for the shortage of power supply at the beginning of the rapid current increase. However, when the current approaches the input current limit value Iinmax, in other words, when the difference ΔIin decreases and exceeds the predetermined values ΔIinA and ΔIinB, the control gain is multiplied by, for example, the correction coefficient ki shown in the map of FIG. And the amount of current overshoot can be suppressed. For this reason, the voltage drop is also reduced, and it is possible to prevent a shortage of power supply or the like from occurring temporarily and adversely affecting the commerciality of the DC-DC converter.

  As described above, the process of the present embodiment described above is different from the control technique disclosed in Patent Document 1 in which the control is performed when a certain current value is reached, as well as the conventional control, and the feedback control is always performed according to the current. Since the gain is corrected, it is possible to cope with a steep increase in power.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings. In addition, about the part which overlaps with above-described 1st Embodiment, and the structure of the same function, the same referential mark is attached | subjected and description is abbreviate | omitted and it demonstrates centering on a different part. Referring to FIG. 4, in the booster 200 according to the present embodiment, unlike the first embodiment, a current sensor P <b> 1 is disposed between the second switching element SW <b> 2 of the booster circuit 230 and the load M to output current. The value Iout is detected.

  Next, the process of this embodiment will be described with reference to FIG. The current setting unit 201 reads the target current value Iobj set by the ECU or the like (step S301), and compares the target current value Iobj, the characteristics of the load M sent from the state quantity detection unit 202, and the temporal value of the output current value. The input current limit value Ioutobj is calculated from the change, the current value, etc. (step S302).

  Subsequently, the correction unit 210 calculates a difference ΔIout by subtracting the input current value Iout sent from the current sensor P1 from the input current limit value Ioutobj (step S303), and the coefficient k calculation unit 212 is based on the difference ΔIout. Thus, the correction coefficient kout for correcting the voltage control gain is calculated (step S304). Next, the correction unit 210 corrects the basic control gain Po by multiplying the basic control gain Po by the correction coefficient kout, and calculates the feedback control gain Pv (S305). Here, the correction coefficient kout can be set to 1 to compensate for the shortage when the difference ΔIout is large, as shown in FIG. 4, and a map that changes so that the value decreases as the difference ΔIout decreases can be used.

  Subsequently, the control unit 220 calculates a difference between the target voltage value Vobj and the output voltage value Vout, calculates Pv × (Vobj−Vout) obtained by multiplying the difference by the feedback control gain Pv, and becomes the previous value. The duty ratio Duty (n) corrected by adding to the duty ratio Duty (n-1) is set (step S306), and this process is terminated.

  According to the above configuration, since the control gain is reduced only when the output current becomes large and approaches the limit value, the step-up of the commercial output without limiting the output of the transient output current more than necessary. An apparatus can be provided.

<Third Embodiment>
Next, an embodiment in which the steering assist motor of an EPS (electric power steering apparatus) that is driven and controlled according to the driver's steering input is the load M will be described. The basic configuration and function of the booster are not described because the booster described in the first and second embodiments is applied. In FIG. 6, the boost control device 12 is assumed to include the state quantity detection unit 102, the current setting unit 101, the correction unit 110, and the control unit 120 of FIG. 1. Reference numeral 13 denotes the battery B of the booster circuit 130 in FIG. 1 and other circuit portions. The motor 11 corresponds to the load M in FIG.

  FIG. 6 shows a schematic configuration of the electric power steering device EPS1 for a vehicle according to the present embodiment. As shown in the figure, the EPS 1 is configured by a steering system that steers the front wheels W and W when the driver operates the steering wheel 2. One end of a steering shaft 3 is coaxially and integrally coupled to the steering wheel 2, and a rack and pinion mechanism 5 is connected to the other end of the steering shaft 3 via a connecting shaft 4 having a universal joint. . The rack and pinion mechanism 5 includes a pinion 6 on the steering shaft side and a rack shaft 7 on which rack teeth 7a meshing with the pinion 6 are formed. Convert to reciprocating linear motion (vehicle width direction). The left and right front wheels W, W are connected to both ends of the rack shaft 7 via tie rods 8, 8, and the front wheels W, W are steered to the left and right by the reciprocating linear motion of the rack shaft 7.

  The EPS 1 includes a motor 11 installed coaxially with the rack shaft 7 and a boost control device 12 that drives and controls the motor 11 via the boost unit 13 in order to generate assist torque that assists the driver's steering operation. It has. The motor 11 is a brushless DC motor having an embedded magnet structure having a plurality of phases (for example, three phases of U phase, V phase, and W phase). The voltage boost control device 12 is controlled by vector control based on the dq axis current component. Is driven and controlled.

  The EPS 1 boosts the voltage from the battery B by the booster 13 based on the motor control signal from the boost controller 12, supplies the boosted voltage to the motor 11, and drives the motor 11 to generate assist torque. The assist torque of the motor 11 is converted into thrust via a ball screw mechanism 9 provided coaxially with the rack shaft 7 and acts on the rack shaft 7 to assist the driver's steering operation.

  The EPS 1 further includes a motor current detecting means 14 for detecting a current flowing through the motor 11, a steering torque sensor 15 for detecting a steering torque acting on the pinion 6, and a vehicle speed sensor for outputting a vehicle speed signal corresponding to the traveling speed of the vehicle. 16, battery voltage detection means 17 for detecting the voltage of the battery B, motor atmosphere temperature detection means 18 for detecting the ambient temperature of the motor 11, and the rotor angle of the motor 11, that is, the magnetic pole of the rotor from a predetermined reference rotation position And a rotation sensor 32 including a resolver, an encoder, and the like that detect a state quantity related to the rotation angle.

  A necessary target current is set from the assist torque calculated based on the detection signals of the motor current detection means 14, the steering torque sensor 15, the vehicle speed sensor 16, the battery voltage detection means 17, and the motor ambient temperature detection means 18. The boost control device 12 executes the correction described in the first and second embodiments, and outputs a motor control signal corresponding to the target current to the boost unit 13.

  Here, an example of load characteristics for calculating the assist torque in the EPS 1 will be described with reference to FIG. The load characteristics include basic characteristics such as the characteristics of the motor 11, steering gear ratio, and variable gear ratio, as well as loads such as friction of the EPS 1 as a whole due to turning. In consideration of such load characteristics, a required value of the axial force of the motor 11 is set, and a target input current (target current) is estimated based on the required value of the axial force. FIG. 7 shows an example of this load characteristic, and shows the relationship between the axial force required for the motor 11 and the input current for generating this axial force. In addition, the arrow in FIG. 7 represents the direction of steering.

  As shown in FIG. 7, the axial force required for the motor 11 can be expressed by two physical quantities, the turning direction (arrow) and the steering angle. Referring to FIG. 7A, when the occupant steers to the right from the straight traveling state, the axial force (solid line) required for the motor 11 increases monotonously. And the increase amount of the axial force with respect to an angle becomes so large that it approaches a right end. In order to realize the transition of the axial force, an input current (broken line) supplied to the motor 11 is estimated.

  On the other hand, referring to FIG. 7 (b), when the occupant steers the steering from the right end to the left end, the axial force (solid line) required for the motor 11 is opposite to that when turning to the right. However, referring also to FIG. 7A, the transition of the axial force of the left steering is vertically symmetrical with respect to the horizontal axis of the axial force 0 as compared with the case of the right steering, and the angle is the same as that of the right steering. The amount of increase in the axial force increases with increasing distance to the left end. In order to realize the transition of the axial force, the input current (broken line) supplied to the motor 11 is estimated, and referring also to FIG. 7A, the transition of the input current is compared with the case of the right steering. It is symmetrical with respect to the vertical axis of current 0.

  As described above, the required value based on the load characteristic of the EPS 1 is estimated from the steering angle and the direction in which the steering is performed, so that a necessary input current can be estimated and an assist torque for assisting the driver's steering operation is generated. The axial force of the motor 11 and the input current for generating this axial force can be estimated. The graph shown in FIG. 7 is stored in the memory of the boost control device 12 as a map, and the input current can be estimated from the state quantity detected using this map.

  The motor current detection means 14 is formed of, for example, a current transformer provided for each winding of the motor 11 and detects the magnitude and direction of the motor current that actually flows through the motor 11. Then, the motor current detection means 14 feeds back a motor current signal corresponding to the motor current to the boost control device 12.

  A steering torque sensor 15 disposed in the steering gear box detects the magnitude and direction of manual steering torque by the driver. Then, the steering torque sensor 15 transmits an analog electric signal corresponding to the detected steering torque to the boost control device 12 as a steering torque signal.

  The vehicle speed sensor 16 detects the vehicle speed Vs as the number of pulses per unit time, and transmits an analog electric signal corresponding to the detected number of pulses to the boost control device 12 as a vehicle speed signal. Note that the vehicle speed sensor 16 may be a dedicated one for the EPS 1, or a vehicle speed sensor of another system may be used.

  The battery voltage detecting means 17 is a voltage sensor that detects the terminal voltage of the battery B, detects the voltage of the DC power supplied to the boosting unit 13, and boosts the analog electric signal corresponding to the detected voltage as the battery voltage signal. It transmits to the control apparatus 12.

  The motor ambient temperature detection means 18 is disposed in the vicinity of the motor 11 and detects the ambient temperature of the motor 11. The detected motor ambient temperature TM is converted into a corresponding analog electrical signal and transmitted to the boost control device 12 as an ambient temperature signal.

  By mounting the boost control device 12 including the state quantity detection unit, the current setting unit, the correction unit, and the control unit described in the first and second embodiments in the EPS 1 having such a configuration, for example, Even if the steering operation that hits the rack end is performed and excessive current flows transiently, the control gain is reduced only when the output current is large, so the transient output current is output more than necessary. It is possible to realize boost control with high merchantability without limitation.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and can be modified and used without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Steering apparatus 2 Steering wheel 10 Electric power steering apparatus 11 Motor 12 Boosting control apparatus 13 Boosting part 14 Motor current detection means 15 Steering torque sensor 16 Vehicle speed sensor 17 Battery voltage detection means 18 Motor atmosphere temperature detection means 19 Target current setting part 32 Rotation Sensor 100, 200 Booster 101, 201 Current setting unit 102, 202 State quantity detection unit 110, 210 Correction unit 112, 212 Coefficient k calculation unit 120, 220 Control unit 124, 224 PWM (pulse width modulation) output unit 130, 230 Booster circuit B Battery C Capacitor L Coil M Load (motor)
SW1, SW2 switching element

Claims (8)

A booster that boosts an input voltage and outputs the boosted voltage to a connected load,
A booster circuit for boosting the input voltage;
Control means for controlling the boost value of the booster circuit so that the output voltage value from the booster circuit is feedback-controlled so that the output voltage value approaches a target voltage value set based on a request for the load;
State quantity detection means for detecting a state quantity of the booster circuit including at least an input current value to the booster circuit;
Current setting means for setting an input current limit value to be a limit value of the input current value from the target current value set based on the load-side required value and the detected state quantity;
A correction unit that calculates a feedback control gain of the output voltage value according to a difference between the detected input current value and the set input limit current value, and outputs the feedback control gain to the control unit;
The boosting device according to claim 1, wherein the correction unit decreases a feedback control gain corresponding to the target voltage value as the difference becomes smaller than a predetermined value. The state quantity includes a characteristic of the load, an output current value, and a temporal change of the output current value.
The current setting means sets the input limit current value based on at least one of the output current value and the temporal change of the output current value, or both state quantities together with the characteristics of the load. The boosting device according to claim 1.   The correction means calculates a correction coefficient according to a difference between the input current value and the input limit current value based on a preset map, and multiplies the correction coefficient by the feedback control gain to perform the correction. The step-up device according to claim 1, wherein the step-up device is performed. A booster that boosts an input voltage and outputs the boosted voltage to a connected load,
A booster circuit for boosting the input voltage;
Control means for controlling the boost value of the booster circuit so that the output voltage value from the booster circuit is feedback-controlled so that the output voltage value approaches a target voltage value set based on a request for the load;
State quantity detection means for detecting a state quantity of the booster circuit including at least an output current value from the booster circuit;
A current setting means for setting an output limit current value to be a limit value of the output current value from the target current value set based on the request value on the load side and the detected state quantity;
A correction unit that calculates a feedback control gain of the output voltage value according to a difference between the detected output current value and the set output limit current value, and outputs the feedback control gain to the control unit;
The boosting device according to claim 1, wherein the correction unit decreases a feedback control gain corresponding to the target voltage value as the difference becomes smaller than a predetermined value. The state quantity includes a characteristic of the load, the detected output current value, and a temporal change of the output current value,
The current setting means sets the input limit current value based on at least one of the output current value and the temporal change of the output current value, or both state quantities together with the characteristics of the load. The boosting device according to claim 4.   The correction means calculates a correction coefficient according to a difference between the output current value and the output limit current value based on a preset map, and multiplies the feedback control gain by the correction coefficient to perform the correction. 6. The boosting device according to claim 4, wherein the boosting device is performed.   The load is a motor for assisting steering of an electric power steering apparatus mounted on a vehicle and driven and controlled in accordance with a driver's steering input. The booster described in 1. The electric power steering device includes a steering angle detection means for detecting a steering angle,
The booster according to claim 7, wherein the required value on the load side is estimated from the detected steering angle and a steering direction.

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