JP2008168728A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To locate a section causing a failure when the failure occurs in a control system of an electric power steering device. <P>SOLUTION: This electric power steering device is controlled by an EPS (Electric Power Steering) controller 50, which prevents current from flowing into motor phase current detection circuits 62, 63 when it determines that the currents detected in the motor phase current detection circuits 62, 63 are abnormal. If the EPS controller 50 detects currents in the motor phase current detection circuits 62, 63 even in the condition in which currents do not flow into the motor phase current detection circuits 62, 63, it determines that the motor phase current detection circuits 62, 63 are abnormal. On the other hand, when the EPS controller 50 does not detect currents in the motor phase current detection circuits 62, 63 while currents do not flow into the motor phase current detection circuits 62, 63, it determines that a predriver 60 or a motor driving circuit 61 is abnormal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to control of an electric power steering device that assists steering of a vehicle such as a passenger car or a truck with an electric motor.

  In order to reduce the steering force of vehicles such as passenger cars and trucks, there is a so-called electric power steering (EPS) device that assists steering by an electric motor. The electric power steering device reduces the operating force when the driver operates the steering wheel by applying the driving force of the electric motor to the steering shaft, the rack shaft of the steering mechanism, or the like via a reduction gear.

  Generally, the electric motor of the electric power steering apparatus is feedback-controlled based on the value of current that drives the electric motor. In the electric power steering device, when the control system including the control device fails, the application of the auxiliary steering force by the electric motor is stopped from the viewpoint of avoiding danger. For example, in Patent Document 1, when the terminal voltage of an electric motor to which an auxiliary steering force is applied deviates from a predetermined range, it is determined that a failure has occurred in a control system circuit, and electric power for prohibiting energization of the electric motor is disclosed. A steering device is disclosed.

JP-A-11-147479, paragraphs 0015 to 0026

  By the way, since the technique disclosed in Patent Document 1 does not determine the location of the failure that has occurred in the control system, it may take time to correct the failure and to clarify the cause of the failure. Further, since the technique disclosed in Patent Document 1 does not determine the location of a failure that has occurred in the control system, even when steering assistance can be continued, the motor is uniformly applied regardless of the location of the control system failure. Energization is prohibited and steering assistance is stopped.

  The present invention has been made in view of the above, and an electric power steering apparatus and a method for controlling an electric power steering apparatus that can determine a location where the trouble has occurred when a trouble occurs in the control system of the electric power steering apparatus. The purpose is to provide.

  In order to solve the above-described problems and achieve the object of the present invention, the present invention provides a steering torque detecting means for detecting a steering torque generated in a steering shaft of a vehicle, and an electric motor for applying an auxiliary steering force to a steering mechanism. A current command value calculation unit that calculates a current command value to be supplied to the motor based on at least the steering torque, a current detection circuit that detects a current value of the motor, the current command value, and a current value of the motor An electric power steering apparatus comprising: an electric motor drive control unit that controls the electric motor based on the current detection circuit; and an abnormality determination unit that determines whether or not the current detected from the current detection circuit is abnormal. Is determined to be abnormal, current interruption means for preventing current from flowing to the current detection circuit and power supply to the current detection circuit. In the state where current does not flow, when detecting current from the current detection circuit, detection circuit abnormality determination means for determining that the current detection circuit is abnormal, and in the state where current does not flow to the current detection circuit, Drive current abnormality determining means for determining that the electric motor drive control means is abnormal when no current is detected from the current detection circuit. Thereby, when a malfunction occurs in the control system of the electric power steering apparatus, it is possible to determine the location where the malfunction has occurred.

  Further, according to a preferred aspect of the present invention, the detection circuit abnormality determination unit is configured to detect the current detection when the current abnormality determination unit detects a current exceeding a limit current value that cannot flow through the current detection circuit. It is desirable to determine that the circuit is abnormal.

  According to a preferred aspect of the present invention, when the detection circuit abnormality determination means determines that the current detection circuit is abnormal, the motor is driven without being based on the current value detected by the current detection circuit. It is desirable to control and apply an auxiliary steering force to the steering mechanism.

  Further, according to a preferred aspect of the present invention, the motor drive control means controls the drive of the motor without being based on the current value detected by the current detection circuit, and applies an auxiliary steering force to the steering mechanism. When performing, the electric power steering device is controlled with a stricter limit value than when the auxiliary steering force is applied to the steering mechanism by controlling the driving of the electric motor based on the current value detected by the current detecting circuit. It is desirable to do.

  Further, according to a preferred aspect of the present invention, the electric motor drive control means drives and controls the electric motor by open loop control based on torque input to the electric power steering device, so that an auxiliary steering force to the steering mechanism is obtained. It is desirable to give

  According to a preferred aspect of the present invention, when there are a plurality of the current detection circuits, the motor drive control means controls the motor based on a current value detected by the current detection circuit operating normally. It is desirable to apply drive control to apply an auxiliary steering force to the steering mechanism.

  According to a preferred aspect of the present invention, the electric motor drive control means is configured to reduce the auxiliary steering force applied to the steering mechanism when the speed of a vehicle on which the electric power steering device is mounted is equal to or lower than a predetermined set value. It is desirable to stop granting.

  According to a preferred aspect of the present invention, it is desirable that when the drive control abnormality determining means determines that the motor drive control means is abnormal, the application of the auxiliary steering force to the steering mechanism is stopped.

  In order to solve the above-described problems and achieve the object of the present invention, the present invention provides a steering torque detecting means for detecting a steering torque generated in a steering shaft of a vehicle, and an electric motor for applying an auxiliary steering force to a steering mechanism. A current command value calculation unit that calculates a current command value to be supplied to the motor based on at least the steering torque, a current detection circuit that detects a current value of the motor, the current command value, and a current value of the motor In the control method of an electric power steering apparatus that controls an electric power steering apparatus that includes an electric motor drive control unit that controls the electric motor based on the above, it is determined whether or not the current detected from the current detection circuit is abnormal If the current detected from the procedure and the current detection circuit is abnormal, the current does not flow to the current detection circuit; A procedure for determining that the current detection circuit is abnormal when a current is detected from the current detection circuit in a state where no current flows to the current detection circuit, and a current is supplied to the current detection unit. And a procedure for determining that the motor drive control means is abnormal when no current is detected from the current detection circuit in a state of not flowing. Thereby, when a malfunction occurs in the control system of the electric power steering apparatus, it is possible to determine the location where the malfunction has occurred.

  According to a preferred aspect of the present invention, when a current exceeding a limit current value that cannot flow through the current detection circuit is detected from the current detection circuit, it is determined that the current detection circuit is abnormal. desirable.

  According to a preferred aspect of the present invention, when it is determined that the current detection circuit is abnormal, the motor is driven and controlled based on the current value detected by the current detection circuit, and the steering mechanism is controlled. It is desirable to apply an auxiliary steering force.

  According to a preferred aspect of the present invention, when the electric motor is driven and controlled based on the current value detected by the current detection circuit and the auxiliary steering force is applied to the steering mechanism, the current detection is performed. It is desirable to control the electric power steering apparatus with a stricter limit value than when the auxiliary steering force is applied to the steering mechanism by controlling the driving of the electric motor based on the current value detected by the circuit.

  Further, according to a preferred aspect of the present invention, it is desirable that the electric motor is driven and controlled by open loop control based on torque input to the electric power steering device, and an auxiliary steering force is applied to the steering mechanism. .

  According to a preferred aspect of the present invention, when there are a plurality of the current detection circuits, the electric motor is driven and controlled based on a current value detected by the current detection circuit operating normally, and the steering is performed. It is desirable to apply an auxiliary steering force to the mechanism.

  Further, according to a preferred aspect of the present invention, it is desirable that the application of the auxiliary steering force to the steering mechanism is stopped when the speed of the vehicle on which the electric power steering device is mounted is equal to or lower than a predetermined set value. .

  According to a preferred aspect of the present invention, it is desirable to stop applying the auxiliary steering force to the steering mechanism when it is determined that the electric motor drive control means is abnormal.

  The electric power steering device and the control method for the electric power steering device according to the present invention can determine the location where the malfunction occurs when the malfunction occurs in the control system of the electric power steering device. Further, the electric power steering apparatus and the control method for the electric power steering apparatus according to the present invention can continue the steering assist depending on the location where the trouble occurs.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention described below (hereinafter referred to as an embodiment).

  In this embodiment, in the electric power steering apparatus, when the current detected from the current detection circuit is abnormal, a state in which no current flows to the current detection circuit is intentionally created, and no current flows to the current detection circuit Is characterized in that, based on the current detected from the current detection circuit, an abnormality in the current detection circuit or an abnormality in the motor drive control means of the electric power steering apparatus is determined. For example, when a current is detected from the current detection circuit even though no current flows to the current detection circuit, it is determined that the current detection circuit is abnormal and the current detection unit is in a state where no current flows. When no current is detected from the current detection circuit, it is determined that the motor drive control means of the electric power steering device is abnormal.

  FIG. 1 is a schematic diagram illustrating a configuration of an electric power steering apparatus according to the present embodiment. An electric power steering apparatus 1 according to this embodiment includes a steering wheel 2, a steering shaft 3, a first universal joint 4A, a steering joint 5, a second universal joint 4B, a steering gear input shaft 6 and a steering gear 7, and an electric power steering apparatus. The control device (hereinafter referred to as EPS control device) 50 is configured. The steering shaft 3, the first universal joint 4A, the steering joint 5, the second universal joint 4B, the steering gear input shaft 6, and the steering gear 7 constitute the steering mechanism 1C. The electric power steering device 1 assists the driver to operate the steering wheel 2 by applying an auxiliary steering force to the steering mechanism 1C by the electric motor 9.

  In the electric power steering apparatus 1, the steering torque input to the steering wheel 2 by the driver is transmitted to the steering shaft 3 having the input shaft 3I and the output shaft 3E. The steering shaft 3 is rotatably supported by the casing of the steering mechanism 1C. The steering shaft 3 has one end of the input shaft 3I connected to the steering wheel 2 and the other end connected to one end of the output shaft 3E via a torque sensor 40 as steering torque detecting means. The steering torque input to the steering wheel 2 is first transmitted to the input shaft 3I of the steering shaft 3 and then transmitted to the output shaft 3E via the torque sensor 40.

  The steering torque transmitted to the output shaft 3E of the steering shaft 3 is transmitted to the steering joint 5 via the first universal joint 4A, and further transmitted to the steering gear input shaft 6 via the second universal joint 4B. The steering torque transmitted to the steering gear input shaft 6 is transmitted to the tie rod 8 via the steering gear 7 to steer the steered wheels of the vehicle 100, that is, the left front wheel 101l and the right front wheel 101r. Here, the steering gear 7 is configured in a so-called rack-and-pinion type having a pinion gear 7p connected to the steering gear input shaft 6 and a rack gear 7r meshing with the pinion gear 7p. To convert straight motion.

  A reduction gear 10 is attached to the output shaft 3E of the steering shaft 3. The output generated by the electric motor 9 is amplified through the reduction gear 10 and transmitted to the output shaft 3E. As a result, an auxiliary steering force is applied to the steering mechanism 1 </ b> C via the steering shaft 3 of the electric power steering apparatus 1.

  The torque sensor 40 attached to the input shaft 3I of the steering shaft 3 detects the steering torque transmitted to the input shaft 3I via the steering wheel 2. The torque sensor 40 converts, for example, a steering torque input by the driver into a torsional angular displacement by a torsion bar interposed between the input shaft 3I and the output shaft 3E of the steering shaft 3, and this torsional angular displacement is converted into the torsional angular displacement. It is configured to detect with a potentiometer.

FIG. 2 is a conceptual diagram showing the relationship between the steering torque input to the torque sensor provided in the electric power steering apparatus according to this embodiment and the output value of the torque sensor. As shown in FIG. 2, the torque sensor 40 outputs a predetermined neutral voltage V0 when the steering torque input by the driver is 0. When the steering wheel 2 is operated rightward from this state, the torque sensor 40 is input. A voltage that is higher than the neutral voltage V0 in response to an increase in the steering torque is output. Further, when the steering wheel 2 is operated to the left from the state in which the input steering torque is 0, the torque sensor 40 causes the neutral voltage V0 to be increased according to the increase in the input steering torque. Output a voltage that decreases more than.

  For example, when the driver operates the steering wheel 2 of the electric power steering apparatus 1 to the right with the steering torque T_R, the torque sensor 40 outputs a voltage of V_R. Further, when the driver operates the steering wheel 2 of the electric power steering apparatus 1 to the left with the steering torque T_L, the torque sensor 40 outputs a voltage of V_L. Since the steering torque and the steering direction input to the electric power steering apparatus 1 correspond to the voltage output from the torque sensor 40 on a one-to-one basis, the input to the electric power steering apparatus 1 depends on the value of the voltage output from the torque sensor 40. The magnitude of the steering torque to be applied and the steering direction of the electric power steering apparatus 1 can be determined.

  The voltage value output from the torque sensor 40 is input to the EPS control device 50 as a torque detection value T as shown in FIG. In addition to the torque detection value T, the EPS control device 50 has a detection value v of the vehicle 100 (hereinafter referred to as a vehicle speed detection value) v detected by the vehicle speed sensor 41 and a current value of the motor 9, that is, a flow to the motor 9. Then, a current for driving the electric motor 9, that is, a value of the electric motor driving current (hereinafter referred to as a driving current value) I_d is input. Then, the EPS control device 50 requires a value of current supplied to the motor 9 (hereinafter referred to as a current command value) I_c necessary for causing the motor 9 to generate an auxiliary steering force according to the torque detection value T and the vehicle speed detection value v. Is calculated. The EPS control device 50 feedback-controls the drive current value I_d so that the difference between the calculated current command value I_c and the drive current value I_d becomes zero. Here, the auxiliary steering force is the force of the electric motor 9 transmitted to the output shaft 3E through the reduction gear 10. Next, the configuration of the EPS control device 50 that controls the electric power steering device 1 according to the present embodiment will be described.

  FIG. 3 is a block diagram showing a hardware configuration of an EPS control apparatus that controls the electric power steering apparatus according to the present embodiment. The EPS control device 50 includes a bus 51, a nonvolatile memory 52, an A / D (Analog / Digital) converter 53, an input interface 54, a clock generation circuit 55, a CPU (Central Processing Unit) 56, a ROM (Read Only Memory) 57, RAM (Random Access Memory) 58, RD (Resolver Digital) converter 59, pre-driver 60, motor drive circuit 61, motor phase current detection circuits 62 and 63, total current detection circuit 64, signal amplification means 65, 66 and 70, electric motor Relays 67 and 68, and a power supply relay 69.

  The bus 51 is for transmitting and receiving data among the A / D converter 53, the input interface 54, the clock generation circuit 55, the CPU 56, the ROM 57, the RAM 58, and the like. The A / D converter 53 includes a torque detection value T output from the input torque sensor 40, a drive current value detected from the motor phase current detection circuits 62 and 63, a motor rotation angle signal from the RD converter 59, and the motor 9 The voltage between the terminals is converted into a digital signal.

  The input interface 54 converts the vehicle speed detection value v from the vehicle speed sensor 41 into a digital signal. The ROM 57 is used as a memory for storing a control program for the electric motor 9, a calculation program for PWM (Pulse Width Modulation), a fail safe program, and the like. The RAM 58 is used as a work memory for operating the program. The non-volatile memory 52 is configured by, for example, an EEPROM (Electrically Erasable Programmable Read Only Memory), a flash memory, or the like, and can retain the stored contents even after the EPS controller 50 is de-energized.

  The pre-driver 60 converts a signal representing a torque generated by the electric motor 9 calculated by the CPU 56, that is, a current command value, into pulse command modulated duty command values W, V, U, Wb, Vb, Ub. belongs to. Here, the duty command values W, V, and U represent normal-phase three-phase signals, and the duty command values Wb, Vb, and Ub represent reverse-phase three-phase signals. As shown in FIG. 1, an in-vehicle power supply 11 mounted on the vehicle 100 is connected to the electric motor drive circuit 61, and electric power for driving the electric motor 9 is supplied from the in-vehicle power supply 11. The motor drive circuit 61 is composed of three inverter circuits for generating three-phase currents of W, V, and U. Each inverter circuit includes a switching transistor 61A on the power supply voltage side and a switching transistor on the ground potential side. 61B.

  Positive phase duty command values W, V, U are input to the gate of the switching transistor 61A on the power supply voltage side, and negative phase duty command values Wb, Vb, Ub are input to the switching transistor 61B on the ground potential side. Yes. That is, the switching transistors 61A and 61B on the power supply voltage side and the ground voltage side are complementarily connected, and the torque detection value T, the vehicle speed detection value v, and the feedback current value of the drive current value are alternately repeated by repeating the on / off operation. Based on the above, motor drive currents Iu, Iv, and Iw having pulse widths calculated by the CPU 56 are generated.

  It should be noted that the dead time, that is, the time during which both are turned off, is set so that the switching transistors 61A on the power supply voltage side and the switching transistor 61B on the ground voltage side do not turn on at the same time. It is provided before and after the on-time and the on-time of the negative phase duty command values Wb, Vb, Ub. Thus, by providing the dead time, it is possible to avoid a short circuit between the switching transistors 61A and 61B on the power supply voltage side and the ground voltage side. The RD converter 59 supplies an exciting current to the resolver 42 and outputs an output signal from the resolver 42 to the A / D converter 53 as a rotation angle signal.

  The motor phase current detection circuits 62 and 63 are current detection circuits for detecting the value of the motor drive current, that is, the drive current value, and include, for example, a current-voltage conversion element such as a resistor. The motor phase current detection circuits 62 and 63 detect the motor drive currents Iu and Iw, and output voltages corresponding to the motor drive currents Iu and Iw. The voltages output from the motor phase current detection circuits 62 and 63 are amplified by signal amplification means 65 and 66 such as operational amplifiers, and then input to the A / D converter 53, where they are converted into digital signals and sent to the CPU 56. It is captured. In the CPU 56, the voltage values output from the motor phase current detection circuits 62 and 63 are converted into current values, and the drive current values are obtained.

  The total current detection circuit 64 is provided on the ground voltage terminal side of the electric motor drive circuit 61. The total current detection circuit 64 is a current detection circuit that detects the value of the total current flowing through the motor drive circuit 61, and includes, for example, a current-voltage conversion element such as a resistor. The total current detection circuit 64 detects the total current Ia flowing through the electric motor drive circuit 61 and outputs a voltage corresponding to the total current Ia. The voltage output from the total current detection circuit 64 is amplified by a signal amplifying means 70 such as an operational amplifier, and then input to the A / D converter 53, where it is converted into a digital signal and taken into the CPU 56. Then, in the CPU 56, the voltage value output from the total current detection circuit 64 is converted into a current value, and the total current value is obtained.

  In the present embodiment, the current detection circuit includes signal amplification means 65, 66, and 70, and wiring thereof in addition to the motor phase current detection circuits 62 and 63 and the total current detection circuit 64. That is, in the present embodiment, the current detection circuit includes the motor phase current detection circuits 62 and 63 and the total current detection circuit 64, and elements and wirings existing between them and the CPU 56. In the present embodiment, the motor phase current detection circuits 62 and 63 and the total current detection circuit 64 output voltage values corresponding to the motor drive currents Iu and Iw and the total current Ia. 63 and the total current detection circuit 64 may be provided with a calculation function to directly output a drive current value or a total current value.

  The electric motor relays 67 and 68 are provided between the electric motor drive circuit 61 and the electric motor 9, and the power supply relay 69 is provided between the in-vehicle power supply 11 and the electric motor drive circuit 61. The motor relays 67 and 68 and the power supply relay 69 are opened and closed in response to a command from the CPU 56. When the auxiliary steering force is applied to the steering mechanism 1 </ b> C shown in FIG. 1 by the electric motor 9, the CPU 56 closes the electric motor relays 67 and 68 and the power supply relay 69 to connect the electric motor drive circuit 61 and the electric motor 9. In addition, when the application of the auxiliary steering force is stopped when an overcurrent is detected from the motor phase current detection circuits 62 and 63, the CPU 56 opens at least one of the motor relays 67 and 68 or the power supply relay 69. The power supply to the electric motor 9 is cut off.

  FIG. 4 is a functional block diagram of an EPS control apparatus that controls the electric power steering apparatus according to the present embodiment. FIG. 5 is a flowchart illustrating a processing procedure of the current abnormality processing unit provided in the EPS control device. The functions of the current command value calculation unit 20, the current command value limiting unit 21, the vector control unit 22, the adder 23, the current control unit 24, the abnormality processing unit 26, and the current abnormality processing unit 30 are included in the EPS controller 50 CPU 56. It is realized by.

  The torque detection value T from the torque sensor 40 is A / D converted and then input to the current command value calculation unit 20. The current command value calculation unit 20 has a function of calculating a current command value for driving the electric motor 9 based on the torque detection value T and the vehicle speed detection value v. The current command value calculation unit 20 also has a function of improving the steering feeling of the vehicle 100 on which the electric power steering device 1 is mounted and a function of ensuring safety, such as a steering wheel return compensation function and a motor maximum current control function. Have.

  The motor phase current detection circuits 62 and 63 detect the U-phase and W-phase motor drive currents supplied to the motor 9, and display the drive current value represented by a voltage value corresponding to the magnitude of the detected motor drive current. Output. The drive current value is amplified by analog signal amplifying means 65 and 66, A / D converted by A / D converter 53 shown in FIG. 3, and further amplified by digital signal amplifying means 71 provided in CPU 56. .

  As shown in FIG. 4, the current command value limiting unit 21 limits the current command value based on the rotation speed of the electric motor 9 acquired from the resolver 42. Further, the vector control unit 22 outputs a three-phase current command value representing a current command value of each phase of the U phase, the V phase, and the W phase based on the rotation angle of the electric motor 9 acquired from the resolver 42. This current command value is input to the adder 23 so that the deviation between the current detection value detected from the motor phase current detection circuits 62 and 63 and the current command value calculated by the current command value calculation unit 20 becomes zero. The feedback control is executed. A control switching unit 25 is provided between the vector control unit 22 and the adder 23. The control switching unit 25 has a function of switching between the feedback control and the open loop control described above.

  The current control unit 24 executes so-called PI control that combines proportional control and integral control based on the deviation between the detected current value and the current command value, that is, the control deviation ΔI. An output signal from the current control unit 24 is output to the pre-driver 60, a three-phase drive current is output from the motor drive circuit 61 to the motor 9, and the drive of the motor 9 is controlled.

  The abnormality processing unit 26 is for executing initial diagnosis and fail-safe processing of the electric power steering apparatus 1 shown in FIG. 1 by monitoring the drive current value, the torque detection value T, or the power supply voltage. For example, when the abnormality processing unit 26 detects an abnormality in the electric motor 9, the torque sensor 40, etc., an instruction is given to the current command value calculation unit 20 so as to gradually decrease the auxiliary steering force by the electric motor 9. The current abnormality processing unit 30 is a part that executes the control method of the electric power steering apparatus according to the present embodiment. Next, the current abnormality processing unit 30 will be described together with the processing procedure of the current abnormality processing unit 30.

  As described above, the function of the current abnormality processing unit 30 is realized by the CPU 56 provided in the EPS control device 50. For example, it is realized by causing the CPU 56 to read a computer program that realizes the function of the current abnormality processing unit 30 and executing the computer program. The current abnormality processing unit 30 includes a current abnormality determination unit 31 that functions as a current abnormality determination unit, a current interruption unit 32 that functions as a current interruption unit, a detection circuit abnormality determination unit 33 that functions as a detection circuit abnormality determination unit, and a drive And a drive control abnormality confirmation unit 34 that functions as a control abnormality confirmation unit.

  Based on the drive current value detected by the motor phase current detection circuits 62 and 63 and the total current detected by the total current detection circuit 64, the current abnormality determination unit 31 performs the motor phase current detection circuits 62 and 63 and the total current detection circuit. It is determined whether or not the current detected from 64 is abnormal (step S1). Here, when the current detected from at least one of the motor phase current detection circuits 62 and 63 and the total current detection circuit 64 is abnormal, the current abnormality determination unit 31 detects the current detected from the current detection circuit. It determines with it being abnormal (step S2, Yes).

  When the current abnormality determination unit 31 determines that the current detected from the motor phase current detection circuits 62, 63 and the like is abnormal (Yes in step S2), the current interruption unit 32, for example, motor relays 67 and 68 Is turned OFF, the drive power supplied to the motor drive circuit 61 is turned OFF, or the current command value calculated by the current command value calculation unit 20 is set to 0 A, whereby the motor phase current detection circuits 62 and 63 are detected. (Step S3, motor current interruption).

  When the detection circuit abnormality determination unit 33 detects a current from the motor phase current detection circuits 62, 63, etc. even though the current does not flow to the motor phase current detection circuits 62, 63, etc. (step S4). Yes), it is determined that the motor phase current detection circuits 62 and 63 are abnormal (step S5). In this case, limited steering assistance is performed (step S6). The limited steering assistance is, for example, steering assistance only after the abnormality of the motor phase current detection circuits 62, 63, etc. is established until the vehicle stops.

  Further, the drive control abnormality determination unit 34 does not detect current from the motor phase current detection circuits 62, 63, etc. in a state where no current flows to the motor phase current detection circuits 62, 63, etc. (No in step S4). Then, it is determined that there is an abnormality in the pre-driver 60 that is the motor drive control means, the motor drive circuit 61, etc. (step S7). In this case, the electric power steering apparatus 1 is turned off and the system is stopped (step S8).

  In step S2, if the current abnormality determination unit 31 determines that the current detected from the current detection circuit is not abnormal, the motor phase current detection circuits 62 and 63, the total current detection circuit 64, and the motor drive control means are used. The pre-driver 60, the electric motor drive circuit 61, etc. are all determined to be normal (step S9), and normal steering assistance is continued (step S10).

  Here, in the present embodiment, the motor drive control means includes the pre-driver 60 and the motor drive circuit 61, the power supply relay 69 provided between the in-vehicle power supply 11 and the motor drive circuit 61, wiring, and the motor drive circuit. 61 and motor relays 67 and 68 provided between the motor 61 and the motor 9 and wiring.

  FIG. 6 is a flowchart illustrating a procedure of a control method for the electric power steering apparatus according to the present embodiment. 7 to 10 are timing charts in the control method of the electric power steering apparatus according to the present embodiment. The operation of the electric power steering apparatus 1 according to the method for controlling the electric power steering apparatus according to the present embodiment will be described with reference to these drawings. In the following description, for the sake of convenience, the motor phase current detection circuits 62 and 63 shown in FIG. 3 are targeted, but the motor phase current detection circuits 62 and 63 are also applied to the total current detection circuit 64 shown in FIG. Can be handled in the same way.

  In executing the control method of the electric power steering apparatus according to the present embodiment, the current abnormality determination unit 31 of the current abnormality processing unit 30 shown in FIG. 4 is detected from the motor phase current detection circuits 62 and 63 shown in FIG. A drive current value (hereinafter referred to as a detection circuit current value) I is acquired (step S101). Here, in the following determination, the determination condition is satisfied if at least one of the motor phase current detection circuits 62 and 63 is applicable, and the determination condition is satisfied when both of the motor phase current detection circuits 62 and 63 are not applicable. Make it not exist.

  The current abnormality determination unit 31 determines whether or not a detection circuit current value I larger than a preset limit current value I_i has been detected (step S102). The limit current value I_i in step S102 is set to a value that cannot flow through the motor phase current detection circuits 62 and 63 and cannot be detected from the motor phase current detection circuits 62 and 63. That is, the limit current value I_i is set to a magnitude of current that cannot flow through the electric motor 9. For example, when the power supply line of the electric motor 9 is short-circuited, an overcurrent flows through the power supply line. In this case, the current flowing to the motor 9 is the largest, but the limit current value I_i is set to a current value that cannot flow through the power supply line even when the power supply line of the motor 9 is short-circuited. The That is, the limit current value I_i is set to a value that cannot theoretically be generated in consideration of the specifications of the EPS control device 50, the in-vehicle power supply 11, and the electric motor 9.

  When I> I_i (step S102: Yes, t1 in FIG. 7), the current abnormality determination unit 31 determines whether or not the state where I> I_i has continued for a preset first diagnosis time Δt1 or more. (Step S103). The first diagnosis time Δt1 is t2-t1, as shown in FIG. When the state of I> I_i is less than Δt1 (step S103: No), the current abnormality determination unit 31 determines whether or not the detection circuit current value I is larger than a preset current abnormality determination threshold I_s. (Step S104).

  Here, the current abnormality determination threshold I_s is used to determine whether or not an abnormal current is flowing in the motor phase current detection circuits 62 and 63. For example, the electric power that can be supplied from the motor driving circuit 61 and the electric motor 9 The upper limit value determined from the specifications of the electric power steering device 50, such as the maximum allowable input, etc. For example, if the current abnormality determination threshold value I_s is set to the maximum input current value of the electric motor 9, a current exceeding the current abnormality determination threshold value I_s cannot flow through the electric motor 9. Therefore, when a current exceeding the current abnormality determination threshold I_s is detected from the motor phase current detection circuits 62 and 63, it can be determined that this current is abnormal. The relationship between the limit current value I_i and the current abnormality determination threshold value I_s in step S102 is I_i> I_s as shown in FIG. Note that I_s in FIG. 7 and I_s in FIG. 8 are the same.

  If I> I_s (step S104: Yes, t1 in FIG. 8), the current abnormality determination unit 31 generates a diagnostic flag F1 as shown in FIG. 8 and goes to the RAM 58 of the EPS control device 50 shown in FIG. At the same time, it is determined whether or not the state of I> I_s has continued for a preset second diagnostic time Δt2 or more (step S105). The second diagnosis time Δt2 is t2-t1 as shown in FIG. The diagnosis flag F1 indicates that an abnormal current has flowed through the power supply system to the electric motor 9. When the diagnosis flag F1 is generated, the current abnormality determination unit 31 proceeds to step S105. The diagnosis flag F1 stored in the RAM 58 is stored in the nonvolatile memory 52 of the EPS control device 50 shown in FIG. 3 after the location where the abnormality has occurred is determined.

  When the state of I> I_s continues for Δt2 or more (step S105: Yes), it can be determined that an overcurrent flows through the motor phase current detection circuits 62 and 63. In this case, the current abnormality determination unit 31 determines that the currents detected from the motor phase current detection circuits 62 and 63 are abnormal, and generates a diagnosis flag F3, so that the RAM 58 of the EPS control device 50 shown in FIG. To store. The diagnosis flag F3 indicates that some abnormality has occurred in the power supply system of the electric motor 9 because an abnormal current flowing in the electric power supply system to the electric motor 9 has continued for a predetermined time. When the diagnosis flag F3 is generated, the current abnormality determination unit 31 proceeds to step S106, and proceeds to a procedure for determining the location where the abnormality has occurred. The diagnostic flag F3 stored in the RAM 58 is stored in the nonvolatile memory 52 of the EPS control device 50 shown in FIG. 3 after the location where the abnormality has occurred is determined.

  When an abnormal value of current (overcurrent) that cannot flow during normal control is detected from the motor phase current detection circuits 62 and 63, the causes are as follows: (1) Although it does not flow, due to the abnormality of the motor phase current detection circuits 62 and 63, the detection circuit current value I by the motor phase current detection circuits 62 and 63 shows an abnormal value. (2) The overcurrent actually flows Although there is no problem, it is conceivable that an abnormality has occurred in the pre-driver 60 or the motor drive circuit 61, and (3) an overcurrent actually flows. In any case, since some trouble has occurred in the EPS control device 50, in order to ensure safety, the application of the auxiliary steering force to the steering mechanism 1C of the electric power steering device 1 shown in FIG. 1 is stopped. The Moreover, in the control method of the electric power steering apparatus according to the present embodiment, the location where an abnormality has occurred is determined by the following method.

  When the state of I> I_s continues for Δt2 or more (step S105: Yes), the current interrupting unit 32 of the current abnormality processing unit 30 intentionally creates a state in which no current flows to the motor phase current detection circuits 62 and 63. (Step S106, motor current interruption). In the present embodiment, the current interrupting unit 32 turns off at least the switching transistor 61A on the power supply voltage side and the switching transistor 61B on the ground voltage side that constitute the motor drive circuit 61 shown in FIG. A state in which no current flows to the circuits 62 and 63 is intentionally created.

  Further, the motor relays 67 and 68 and the power supply relay 69 are opened, the pre-driver 60 is turned off, or the current command value calculated by the current command value calculation unit 20 shown in FIG. 4 is set to 0A. Also good. As a result, a state in which no current flows to the motor phase current detection circuits 62 and 63 can be created more reliably. By creating a state in which no current flows to the motor phase current detection circuits 62 and 63, no motor drive current flows to the motor 9, so that the auxiliary steering force for the steering mechanism 1C of the electric power steering device 1 shown in FIG. The grant of is stopped.

  When a state in which no current flows to the motor phase current detection circuits 62 and 63 is created (step S106), the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 of the current abnormality processing unit 30 are connected to the motor phase current detection circuit 62. 63, the detection circuit current value I is obtained again (step S107). Then, the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 determine whether or not the detection circuit current value I is larger than a preset current abnormality determination lower limit value I_mi (step S108). The current abnormality determination lower limit I_mi shown in FIG. 8 is the motor phase current when the current is detected from the motor phase current detection circuits 62 and 63 even though the current does not flow to the motor phase current detection circuits 62 and 63. The size is set such that the detection circuits 62 and 63 can be determined to be abnormal. For example, the current abnormality determination lower limit I_mi is set to a value larger than the value detected as noise.

  When I> I_mi (step S108: Yes), the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 determine whether the state of I> I_mi has continued for a preset third diagnosis time Δt3 or more. Is determined (step S109). The third diagnosis time Δt3 is t3-t2, as shown in FIG.

  When the state of I> I_mi continues for Δt3 or more (step S109: Yes), the detection circuit abnormality determination unit 33 determines that an abnormality has occurred in the motor phase current detection circuits 62 and 63 (step S110). A diagnostic flag F4 is generated and stored in the nonvolatile memory 52 of the EPS control device 50 shown in FIG. This is because in step S106, a current of a predetermined magnitude is detected from the motor phase current detection circuits 62 and 63 even though a state in which no current flows to the motor phase current detection circuits 62 and 63 is intentionally created. This is because it can be determined that there is an abnormality in the motor phase current detection circuits 62 and 63. The phenomenon in which the state of I> I_mi continues for Δt3 or more can be caused by, for example, a short circuit of the drive voltage of the CPU 56 or the like (so-called power fault) in the motor phase current detection circuits 62 and 63.

  Here, the diagnosis flag F4 shown in FIG. 8 is a flag indicating that an abnormality has occurred in the motor phase current detection circuits 62 and 63, and the stored contents of the nonvolatile memory 52 are stored when inspecting or repairing. By reading, it is possible to know the abnormality of the motor phase current detection circuits 62 and 63. Thus, in this embodiment, since the abnormality of the motor phase current detection circuits 62 and 63 can be determined by the above determination procedure, the abnormal part of the EPS control device 50 can be quickly identified, and inspection and repair can be performed. Increases efficiency. When it is determined that an abnormality has occurred in the motor phase current detection circuits 62 and 63, the CPU 56 indicates that an abnormality has occurred in the motor phase current detection circuits 62 and 63 on the instrument panel of the vehicle 100 shown in FIG. It is preferable to display the warning and to prompt the driver's attention.

  When it is determined that an abnormality has occurred in the motor phase current detection circuits 62 and 63 (step S110), it can be determined that no abnormality has occurred in the pre-driver 60 and the motor drive circuit 61 that control the drive of the motor 9. . In this case, the drive of the electric motor 9 can be controlled using the pre-driver 60 and the electric motor drive circuit 61 without any abnormality, and the application of the auxiliary steering force to the steering mechanism 1C of the electric power steering device 1 can be continued.

  However, since an abnormality has occurred in the motor phase current detection circuits 62 and 63, feedback control cannot be performed based on the detection circuit current value I detected from the motor phase current detection circuits 62 and 63. Therefore, the drive of the electric motor 9 is controlled without being based on the detection circuit current value I, and the application of the auxiliary steering force (steering assistance) to the steering mechanism 1C of the electric power steering device 1 is resumed (step S111).

  The method for controlling the drive of the motor 9 without being based on the detection circuit current value I is, for example, an open loop based on a current command value determined from the torque detection value T and the vehicle speed detection value v without performing feedback of the motor drive current. There is control. When executing the open loop control, the control switching unit 25 shown in FIG. 5 switches the control of the electric motor 9 from the feedback control to the open loop control. Thereby, since steering assistance is continued, since an auxiliary steering force is applied to the input torque to the steering wheel 2 by the driver, it is possible to suppress a sense of discomfort given to the driver. In addition, by applying the auxiliary steering force, it is possible to suppress the operation of the steering wheel 2 from becoming suddenly heavy due to the stop of the steering assist, and thus it is possible to ensure safety.

  In resuming the steering assist, as shown at t4 to t5 in FIG. 8, the value of the motor drive current for driving the motor 9, that is, the drive current value is gradually increased, so that the electric power steering device 1 It is preferable to gradually increase the auxiliary steering force for the steering mechanism 1C. That is, the motor drive current according to the input torque to the steering wheel 2 is not supplied to the motor 9 at the same time as the steering assist is resumed, but gradually approaches the motor drive current to the current command value according to the input torque. Is preferred. As a result, when the steering assist is resumed, it is possible to suppress the sudden increase in the steering angle of the steered wheels of the vehicle 100 shown in FIG. Can be made.

  In addition, when driving control of the electric motor 9 without being based on the detection circuit current value I, the electric power steering apparatus 1 is controlled under conditions that are stricter than when the electric motor 9 is driven and controlled based on the detection circuit current value I. It is preferable to determine abnormality of the power steering apparatus 1. This is because some kind of abnormality has occurred in the EPS control device 50, and thus it is necessary to ensure safety. For example, the maximum value of the auxiliary steering force is made smaller than when the electric motor 9 is driven and controlled based on the detection circuit current value I, or the electric motor drive current is higher than when the electric motor 9 is driven and controlled based on the detection circuit current value I. Or decrease the abnormality judgment value such as motor terminal voltage.

  When the steering assist is resumed in step S111, the CPU 56 determines whether or not the steering assist stop condition is satisfied (step S112). In the EPS control device 50, since abnormality has occurred in the motor phase current detection circuits 62 and 63, it is not preferable to continue steering assistance without limitation. Therefore, even if the steering assistance is stopped, the steering assistance is stopped when a sufficient safety can be ensured. In the present embodiment, when the vehicle speed of the vehicle 100 shown in FIG. 1 is equal to or lower than the predetermined set value v_c shown in FIG. 8, it is determined that the steering assist stop condition is satisfied.

  When the steering assist stop condition is not satisfied (step S112: No), the CPU 56 continues the steering assist by controlling the driving of the electric motor 9 without being based on the detection circuit current value I. When the steering assist stop condition is satisfied (step S112: Yes), the CPU 56 generates a control end flag F5 indicating the end of control, stops the steering assist (step S113), and the electric power steering according to the present embodiment. The device control method ends.

  When stopping the steering assist, it is preferable to gradually reduce the assist steering force with respect to the steering mechanism 1C of the electric power steering apparatus 1 by gradually decreasing the drive current value as shown at t6 to t7 in FIG. . That is, it is preferable that the drive current value is gradually brought close to 0 instead of making the drive current value 0 simultaneously with the stop of the steering assist. As a result, when the steering assist is stopped, it is possible to prevent the assist steering force by the electric motor 9 from rapidly decreasing and the steering wheel 2 of the electric power steering apparatus 1 shown in FIG. The feeling of strangeness given can be suppressed.

  Next, it returns to step S102 and demonstrates. When it is determined No in step S102, that is, when I ≦ I_i, the detection circuit current value I may be greater than or equal to the current abnormality determination threshold I_s in step S104. Therefore, if I ≦ I_i, the process proceeds to step S104, and the CPU 56 executes the procedure after step S104 described above.

  Next, it returns to step S103 and demonstrates. If it is determined Yes in step S103, that is, if the state of I> I_i continues for Δt1 or more, the process proceeds to step S110, and the detection circuit abnormality determination unit 33 generates an abnormality in the motor phase current detection circuits 62 and 63. Confirm that you are doing. The limit current value I_i is theoretically not large enough to flow through the motor phase current detection circuits 62 and 63, so that such a value is detected is not an abnormality of the pre-driver 60 or the motor drive circuit 61. It is determined that the motor phase current detection circuits 62 and 63 are abnormal. When the abnormality of the motor phase current detection circuits 62 and 63 is determined, the CPU 56 executes the procedure after step S111. The phenomenon in which the state of I> I_i continues for Δt1 or more can occur due to, for example, a so-called power fault in which the drive voltage of the CPU 56 or the like is short-circuited to the motor phase current detection circuits 62 and 63.

  As described above, by determining the abnormality of the motor phase current detection circuits 62 and 63 using the limit current value I_i that cannot flow through the motor phase current detection circuits 62 and 63, the motor phase current in step S106 is determined. There is no need to execute a procedure for intentionally creating a state in which no current flows to the detection circuits 62 and 63 and a procedure for determining an abnormal point thereafter. As a result, the location where the abnormality has occurred can be quickly determined and the steering assist can be resumed. Therefore, the time from the determination of the location where the abnormality has occurred to the shift to the steering assist can be shortened, and the time when the steering assist is not executed can be shortened. As a result, the uncomfortable feeling given to the driver due to the interruption of the steering assist can be further reduced, and the safety is further improved.

  Next, it returns to step S104 and demonstrates. If it is determined No in step S104, that is, if I ≦ I_s, since no overcurrent has occurred, the current abnormality determination unit 31 performs the motor phase current detection circuits 62 and 63, the pre-driver 60, and the motor drive. It is determined that the circuit 61 is operating normally (step S114). In this case, the control method for the electric power steering apparatus according to the present embodiment ends.

  Next, it returns to step S105 and demonstrates. When it is determined No in step S105, that is, when the state of I> I_s is less than Δt2, it is considered that an error at the time of detection is the cause. Further, even if an overcurrent actually occurs, it is considered that there is no influence on the electric power steering apparatus 1 because the duration time is extremely short. Therefore, the current abnormality determination unit 31 determines that the motor phase current detection circuits 62 and 63, the pre-driver 60, and the motor drive circuit 61 are operating normally (step S114). In this case, the control method for the electric power steering apparatus according to the present embodiment ends.

  Next, it returns to step S108 and demonstrates. When it is determined No in step S108, that is, when I ≦ I_mi, the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 indicate that the state of I ≦ I_mi is a preset third diagnosis time. It is determined whether or not it has continued for Δt3 or more (step S115). The third diagnosis time Δt3 is t3-t2, as shown in FIG.

  When the state of I ≦ I_mi continues for Δt3 or more (step S115: Yes), the drive control abnormality determination unit 34 determines that an abnormality has occurred in the motor drive control means such as the pre-driver 60 and the motor drive circuit 61. (Step S116). Then, as shown in FIG. 9, a diagnostic flag F6 is generated and stored in the nonvolatile memory 52 of the EPS control device 50 shown in FIG. In this case, the CPU 56 stops the system, that is, turns off the power supply of the electric power steering apparatus 1 (step S117) to ensure safety.

  Here, the diagnostic flag F6 is a flag indicating that an abnormality has occurred in the pre-driver 60 or the electric motor drive circuit 61, and by reading the stored contents of the nonvolatile memory 52 when performing inspection or repair, Abnormalities in the pre-driver 60 and the motor drive circuit 61 can be known. As described above, in the present embodiment, it is possible to determine that an abnormality has occurred in the pre-driver 60 or the electric motor drive circuit 61 by the above determination procedure, so that the abnormal part of the EPS control device 50 can be quickly identified in inspection and repair. Can do. As a result, the efficiency of inspection and repair is improved. When it is determined that an abnormality has occurred in the motor phase current detection circuits 62 and 63, the CPU 56 indicates that an abnormality has occurred in the pre-driver 60 or the motor drive circuit 61 on the instrument panel of the vehicle 100 shown in FIG. It is preferable to display the warning and to prompt the driver's attention.

  When the state of I ≦ I_mi is less than Δt3 (step S115: No, FIG. 10), the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 are the motor phase current detection circuits 62, 63 or the pre-driver 60, It is determined that an abnormality has occurred in either one of the motor drive circuits 61 (step S118), a diagnostic flag F7 is generated as shown in FIG. 10, and the nonvolatile memory 52 of the EPS controller 50 shown in FIG. To store. Thereafter, the CPU 56 stops the system (step S117) and ensures safety.

  In step S106, a state in which no current flows to the motor phase current detection circuits 62 and 63 is intentionally created, but the time during which no current is detected from the motor phase current detection circuits 62 and 63 is less than the third diagnosis time Δt3. In this case, it is appropriate to determine that the cause of I> I_s in step S104 is that the motor phase current detection circuits 62 and 63 or either the pre-driver 60 or the motor drive circuit 61 is abnormal. That's why. In this case, the CPU 56 stops the system (step S117) and ensures safety.

  Here, the diagnosis flag F7 is a flag indicating that an abnormality has occurred in the motor phase current detection circuits 62 and 63, the pre-driver 60, and the motor drive circuit 61, and a non-volatile memory is used for inspection and repair. By reading the stored contents of 52, it is possible to know the abnormality of the motor phase current detection circuits 62 and 63, the pre-driver 60 and the motor drive circuit 61. Thus, in this embodiment, since the location where the abnormality may have occurred in the EPS control device 50 can be determined, the abnormal location of the EPS control device 50 can be quickly identified, and the efficiency of inspection and repair can be improved. improves. When it is determined that an abnormality has occurred in the motor phase current detection circuits 62 and 63 and the pre-driver 60 and the motor drive circuit 61, the CPU 56 displays the motor phase current detection circuit on the instrument panel of the vehicle 100 shown in FIG. It is preferable to display a warning that an abnormality has occurred in 62 and 63 and the pre-driver 60 and the electric motor drive circuit 61 so as to call the driver's attention.

  Next, it returns to step S109 and demonstrates. When it is determined No in step S109, that is, when the duration of the state where I> I_mi is less than Δt3, the detection circuit abnormality determination unit 33 and the drive control abnormality determination unit 34 are connected to the motor phase current detection circuit. 62 and 63 and both the pre-driver 60 and the motor drive circuit 61 are determined to be abnormal (step S118), and a diagnostic flag F7 is generated as shown in FIG. The diagnosis flag F7 is as described above.

  In step S106, a current of a predetermined magnitude is detected from the motor phase current detection circuits 62 and 63 by intentionally creating a state in which no current flows to the motor phase current detection circuits 62 and 63. If the third diagnosis time Δt3 is not reached, the cause of I> I_s in step S104 may be that the motor phase current detection circuits 62, 63 or either the pre-driver 60 or the motor drive circuit 61 is abnormal. This is because it is appropriate to judge that it is the cause. In this case, the CPU 56 stops the system (step S117) and ensures safety.

  The electric motor 9 described above may be a brushless electric motor or an electric motor including a brush. Further, the first diagnosis time Δt1 to the third diagnosis time Δt3 described above are set by experiment, analysis, or the like. The first diagnosis time Δt1 to the third diagnosis time Δt3 may all be the same time, or may be different from each other. In the above description, the abnormality of the motor phase current detection circuits 62 and 63 is determined. However, the abnormality of the total current detection circuit 64 can also be determined by the same method. In the present embodiment, since the motor phase current detection circuits 62 and 63 and the total current detection circuit 64 can independently detect currents, the abnormality of the motor phase current detection circuits 62 and 63 and the total current detection circuit 64 is Each can be judged independently.

  When driving control of the electric motor 9 without being based on the detection circuit current value I, the electric motor 9 may be feedback controlled based on the electric motor driving current detected from the current detection circuit operating normally. For example, when a state in which no current flows to the motor phase current detection circuits 62 and 63 is created, a current equal to or higher than the current abnormality determination lower limit I_mi from one of the motor phase current detection circuits 62 and 63 is detected. Is detected for the third diagnostic time Δt3 or more, it can be determined that an abnormality has occurred in the motor phase current detection circuit in which the current has been detected.

  Therefore, by using the motor phase current detection circuit operating normally and the total current detection circuit 64 shown in FIG. 3, the value of the motor drive current flowing through the motor phase current detection circuit where the abnormality has occurred is estimated. Performs feedback control of motor drive current. In this way, since the operational feeling of the electric power steering apparatus 1 can be improved, the uncomfortable feeling given to the driver can be further reduced. Furthermore, when the electric motor 9 is driven and controlled without being based on the detection circuit current value I, the electric motor 9 may be controlled by rotational angle position control of the electric motor 9 using the resolver 42 shown in FIG.

  For the determination in step S102, step S104, etc., the instantaneous value of the detection circuit current value I can be used. In this way, the processing speed can be improved. Further, in the determination in step S102, step S104, etc., an average value or an integral value of the detection circuit current value I in a predetermined time may be used. In this way, the accuracy of determination can be improved.

  In the above description, the procedure for determining an abnormal location when an excessive current is detected from the motor phase current detection circuits 62 and 63 has been described. When an excessive current is detected from the motor phase current detection circuits 62 and 63 due to an abnormality in the motor phase current detection circuits 62 and 63, the drive voltage of the CPU 56 and the like is short-circuited to the motor phase current detection circuits 62 and 63. It is often caused by so-called skylights. On the other hand, there is an abnormality in which no current is detected from the motor phase current detection circuits 62 and 63 even though the electric motor 9 is driven due to a ground fault or disconnection of the current detection circuits 62 and 63. This can occur when the motor phase current detection circuits 62 and 63 and their wirings are in contact with the ground, that is, when a so-called ground fault occurs.

  In this case, for example, the relationship between the current flowing through the motor phase current detection circuits 62 and 63 and the voltage output from the motor phase current detection circuits 62 and 63 is offset. For example, when the motor phase current detection circuits 62 and 63 output a voltage of 0 V (volt) to 5 V (volt), 2.5 V (volt) is 0 A, and 5 V (volt) is the positive maximum current I_max, 0 V ( Volts) is set to the negative maximum current −I_max. In this way, when 0 V (volt) is output from the motor phase current detection circuits 62 and 63 due to the ground fault or disconnection of the current detection circuits 62 and 63, the apparent maximum negative current −I_max Will be detected.

  Then, the limit current value −I_i of the negative current is set to a magnitude that cannot flow through the power supply line to the electric motor 9. Here, -I_max <-I_i. When 0 V (volt) is output from the motor phase current detection circuits 62 and 63 due to a ground fault or disconnection of the current detection circuits 62 and 63, the negative maximum current −I_max is output from the motor phase current detection circuits 62 and 63. Is detected. Since there is a relationship of −I_max <−I_i, when a negative maximum current −I_max is detected, an apparent current that cannot flow through the power supply line to the motor 9 flows. That such a value is detected is not an abnormality of the pre-driver 60 or the motor drive circuit 61 but an abnormality of the motor phase current detection circuits 62 and 63.

  In addition, although the electric power is supplied to the electric motor 9 and it can be confirmed that the electric motor 9 is driven from the detection value from the resolver 42, the electric motor phase current detection is performed due to the ground fault or disconnection of the current detection circuits 62 and 63. When 0 V (volt) is output from the circuits 62 and 63, it may be determined that the motor phase current detection circuits 62 and 63 are abnormal. In this case, since the electric motor 9 is driven, it can be determined that the pre-driver 60 and the electric motor driving circuit 61 are operating normally, and nevertheless, 0 V (volts) from the electric motor phase current detection circuits 62 and 63. Is output, it is determined that the motor phase current detection circuits 62 and 63 are abnormal. By such a method, even when an abnormality occurs in the motor phase current detection circuits 62, 63 and the like due to a ground fault or disconnection of the current detection circuits 62, 63, this can be determined.

  As described above, in the present embodiment, in the electric power steering apparatus, when the current detected from the current detection circuit is abnormal, a state in which no current flows to the current detection circuit is intentionally created, and the current flows to the current detection circuit. Based on the current detected from the current detection circuit in the absence, the abnormality of the current detection circuit or the abnormality of the motor drive control means of the electric power steering apparatus is determined. Thereby, when a malfunction occurs in the control system of the electric power steering apparatus, the location where the malfunction occurs can be determined and determined.

  As described above, the electric power steering device and the control method for the electric power steering device according to the present invention are useful for the electric power steering device, and are particularly suitable for determining the location of a failure occurring in the control system. ing.

It is the schematic which shows the structure of the electric power steering apparatus which concerns on this embodiment. It is a conceptual diagram which shows the relationship between the steering torque input into the torque sensor with which the electric power steering device which concerns on this embodiment is provided, and the output value of a torque sensor. It is a block diagram which shows the hardware constitutions of the EPS control apparatus which controls the electric power steering apparatus which concerns on this embodiment. It is a functional block diagram of the EPS control apparatus which controls the electric power steering apparatus which concerns on this embodiment. It is a flowchart which shows the process sequence of the electric current abnormality process part with which an EPS control apparatus is provided. It is a flowchart which shows the procedure of the control method of the electric power steering apparatus which concerns on this embodiment. It is a timing chart in the control method of the electric power steering device concerning this embodiment. It is a timing chart in the control method of the electric power steering device concerning this embodiment. It is a timing chart in the control method of the electric power steering device concerning this embodiment. It is a timing chart in the control method of the electric power steering device concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 1C Steering mechanism 2 Steering wheel 9 Electric motor 11 Car-mounted power supply 20 Current command value calculating part 21 Current command value limiting part 22 Vector control part 23 Adder 24 Current control part 25 Control switching part 26 Abnormal processing part 30 Current abnormality Processing unit 31 Current abnormality determination unit 32 Current interruption unit 33 Detection circuit abnormality determination unit 34 Drive control abnormality determination unit 40 Torque sensor 41 Vehicle speed sensor 42 Resolver 50 Control device for electric power steering device (EPS control device)
56 CPU
60 Pre-driver 61 Motor drive circuit 62, 63 Motor phase current detection circuit 64 Total current detection circuit 67, 68 Motor relay 69 Power supply relay 100 Vehicle

Claims (16)

Steering torque detecting means for detecting a steering torque generated in a steering shaft of a vehicle, an electric motor for applying an auxiliary steering force to a steering mechanism, and a current command value for calculating a current command value to be supplied to the electric motor based on at least the steering torque In an electric power steering apparatus comprising: an arithmetic unit; a current detection circuit that detects a current value of the electric motor; and an electric motor drive control unit that drives and controls the electric motor based on the current command value and the electric current value of the electric motor.
Current abnormality determining means for determining whether or not the current detected from the current detection circuit is abnormal;
If the abnormality determining means determines that there is an abnormality, a current interrupting means for setting a state in which no current flows to the current detection circuit;
A detection circuit abnormality determining means for determining that the current detection circuit is abnormal when a current is detected from the current detection circuit in a state in which no current flows to the current detection circuit;
Drive current abnormality determining means for determining that the electric motor drive control means is abnormal when no current is detected from the current detection circuit in a state where no current flows to the current detection circuit;
An electric power steering device comprising: The detection circuit abnormality determination means determines that the current detection circuit is abnormal when the current abnormality determination means detects a current exceeding a limit current value that cannot flow through the current detection circuit. The electric power steering apparatus according to claim 1.   When the detection circuit abnormality determining means determines that the current detection circuit is abnormal, the auxiliary steering force for the steering mechanism is controlled by driving the motor without being based on the current value detected by the current detection circuit. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is provided.   When the electric motor drive control means performs drive control of the electric motor without applying the electric current value detected by the current detection circuit and applies an auxiliary steering force to the steering mechanism, the electric current detection circuit detects 4. The electric power steering apparatus according to claim 3, wherein the electric power steering device is controlled with a stricter limit value than when the auxiliary steering force is applied to the steering mechanism by controlling the driving of the electric motor based on a current value. Electric power steering device. The electric motor drive control means includes
5. The auxiliary steering force is applied to the steering mechanism by driving and controlling the electric motor by open loop control based on torque input to the electric power steering device. 6. Electric power steering device.   When there are a plurality of the current detection circuits, the motor drive control means controls the drive of the motor based on the current value detected by the current detection circuit operating normally, and assists the steering mechanism. The electric power steering apparatus according to any one of claims 3 to 5, wherein a force is applied. The electric motor drive control means includes
7. The auxiliary steering force applied to the steering mechanism is stopped when the speed of a vehicle on which the electric power steering device is mounted is equal to or lower than a predetermined set value. The electric power steering device according to claim 1.   3. The electric power according to claim 1, wherein when the drive control abnormality determining means determines that the motor drive control means is abnormal, the application of the auxiliary steering force to the steering mechanism is stopped. Steering device. Steering torque detecting means for detecting a steering torque generated in a steering shaft of a vehicle, an electric motor for applying an auxiliary steering force to a steering mechanism, and a current command value for calculating a current command value to be supplied to the electric motor based on at least the steering torque Controlling an electric power steering apparatus comprising: an arithmetic unit; a current detection circuit that detects a current value of the motor; and a motor drive control unit that controls the drive of the motor based on the current command value and the current value of the motor. In the control method of the electric power steering device to
A procedure for determining whether the current detected from the current detection circuit is abnormal;
When the current detected from the current detection circuit is abnormal, a procedure for preventing current from flowing to the current detection circuit;
In a state where no current flows to the current detection circuit, when a current is detected from the current detection circuit, a procedure for determining that the current detection circuit is abnormal,
In the state where no current flows to the current detection unit, in the case where no current is detected from the current detection circuit, a procedure for determining that the motor drive control means is abnormal,
A control method for an electric power steering apparatus, comprising:   The electric power according to claim 9, wherein when a current exceeding a limit current value that cannot flow through the current detection circuit is detected from the current detection circuit, it is determined that the current detection circuit is abnormal. Steering device control method.   When it is determined that the current detection circuit is abnormal, the motor is driven and controlled based on the current value detected by the current detection circuit, and an auxiliary steering force is applied to the steering mechanism. The control method of the electric power steering device according to claim 9 or 10.   When the electric motor is driven and controlled based on the current value detected by the current detection circuit and an auxiliary steering force is applied to the steering mechanism, the electric motor is based on the current value detected by the current detection circuit. The control of the electric power steering device according to claim 11, wherein the electric power steering device is controlled with a stricter limit value than when the auxiliary steering force is applied to the steering mechanism by controlling the driving of the electric power steering device. Method.   13. The auxiliary steering force is applied to the steering mechanism by controlling the driving of the electric motor by open loop control based on torque input to the electric power steering device. Control method for electric power steering apparatus.   When there are a plurality of the current detection circuits, drive control of the electric motor is performed based on a current value detected by the current detection circuit operating normally, and an auxiliary steering force is applied to the steering mechanism. The method for controlling an electric power steering apparatus according to any one of claims 11 to 13, characterized in that:   15. The application of auxiliary steering force to the steering mechanism is stopped when the speed of a vehicle on which the electric power steering device is mounted is equal to or lower than a predetermined set value. A method for controlling the electric power steering apparatus according to claim 1.   The method for controlling an electric power steering apparatus according to claim 9 or 10, wherein when it is determined that the electric motor drive control means is abnormal, the application of an auxiliary steering force to the steering mechanism is stopped.

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