JP2011058979A - Electric power steering device, control method of the same, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of generating a steering assist torque based on an alternative steering torque, even when a failure occurs in a part of a torque sensor. <P>SOLUTION: This device includes: a target current calculation part 20 for calculating a target current to be supplied to an electric motor based on a steering torque; a first coil and a second coil wherein each inductance is changed mutually in a reverse direction corresponding to the steering torque; a torque detection circuit 250 for outputting by a hardware, a voltage VT corresponding to a difference between a first voltage and a second voltage based on the inductance change of the first coil and the second coil; a voltage operation part 351 for operating a voltage VTFS corresponding to a difference between both voltages by a software; and a voltage value setting part 352 for diagnosing whether the voltage VT is normal or not, based on the voltage VT and the voltage VTFS, and setting as information on the steering torque based on calculation by the target current calculation part 20, the voltage VT when the voltage VT is normal, and the voltage VTFS when the voltage VT is abnormal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric power steering device, a control method for an electric power steering device, and a program.

In recent years, there has been proposed an electric power steering device that includes an electric motor in a steering system of a vehicle and assists a driver's steering force with the power of the electric motor. The control device that controls the steering assist torque performs energization control of the electric motor based on the steering torque detected by the torque sensor, for example.
In such an electric power steering device, when an abnormality occurs in the torque sensor, an appropriate steering assist torque cannot be obtained. Therefore, when a signal abnormality of the torque sensor is detected, the current supplied to the electric motor is reduced. It has been proposed to stop the steering assist (see, for example, Patent Document 1).

JP 2004-210065 A

  If the steering assist is always stopped when an abnormality occurs in the torque sensor, the operation of the steering wheel becomes heavy and the burden on the driver increases. Therefore, even if an abnormality occurs in a part of the torque sensor, if it is possible to estimate the steering torque by another method, the steering assist torque is generated based on the alternative steering torque, It is desirable to reduce the burden on the driver.

  For this purpose, the present invention provides a calculation means for calculating a target current to be supplied to an electric motor based on a steering torque, and a first coil and a second coil whose inductances change in opposite directions according to the steering torque. And a first voltage based on a change in inductance of the first coil and a second voltage based on a change in inductance of the second coil, and outputting a third voltage corresponding to the difference between the two by hardware And the first voltage and the second voltage are input, the fourth voltage corresponding to the difference between the two voltages is calculated by software, the third voltage based on the third voltage and the fourth voltage A diagnostic means for diagnosing whether or not the three voltages are normal, and the third voltage when the diagnostic means diagnoses that the third voltage is normal; The fourth voltage, said calculating means is an electric power steering apparatus characterized by comprising setting means for setting the information on the steering torque based to calculated.

Here, the output means is a differential amplifier, and the arithmetic means multiplies a value obtained by subtracting the second voltage and the first voltage by an amplification degree of the differential amplifier, It is preferable to calculate the fourth voltage by adding a bias voltage.
And a voltage relationship diagnosing means for diagnosing whether or not the correlation between the first voltage and the second voltage is normal based on the first voltage and the second voltage. When the diagnosis unit diagnoses that the third voltage is abnormal, the voltage relationship diagnosis unit diagnoses that the correlation between the first voltage and the second voltage is normal. 4 voltages are set as information on the steering torque based on the calculation by the calculation means, and when the correlation between the first voltage and the second voltage is diagnosed abnormally, the electric motor is driven. It is preferable to set an assist stop signal to stop.

  From another point of view, the present invention relates to a first coil and a second coil whose inductances change in opposite directions according to a steering torque, a first voltage based on an inductance change of the first coil, and the second coil. The second voltage based on the inductance change of the output voltage, the output means for outputting the third voltage according to the difference between the two voltages by hardware, and the third voltage output by the output means for the target current to be supplied to the electric motor. An electric power steering apparatus comprising: a calculation means for calculating based on a voltage, wherein the first voltage and the second voltage are input, and a fourth voltage corresponding to a difference between the two voltages is calculated by software Means for diagnosing whether or not the third voltage is normal based on the third voltage and the fourth voltage, and the calculating means comprises the diagnostic Means the third when diagnosed voltage is abnormal, an electric power steering device, characterized in that based on the fourth voltage instead of the third voltage when calculating the target current.

  From another point of view, the present invention includes a calculating unit that calculates a target current to be supplied to the electric motor based on the steering torque, a first coil whose inductance changes in opposite directions according to the steering torque, and The second coil, the first voltage based on the inductance change of the first coil and the second voltage based on the inductance change of the second coil are input, and the third voltage corresponding to the difference between the two voltages is output by hardware Output means for controlling the electric power steering apparatus, wherein the first voltage and the second voltage are input, a fourth voltage corresponding to a difference between the two voltages is calculated by software, and the first voltage If the third voltage is diagnosed based on the three voltages and the fourth voltage, and if the third voltage is diagnosed, the third voltage is determined to be abnormal. That when diagnosed as the fourth voltage, a control method of an electric power steering apparatus characterized by said calculating means is set as the information on the steering torque based on the calculated.

  From another viewpoint, the present invention provides a computer with a function of calculating a target current to be supplied to the electric motor based on the steering torque, and a pair of inductances that change in opposite directions according to the steering torque. A third voltage is input from a circuit that inputs a first voltage based on an inductance change of one of the coils and a second voltage based on an inductance change of the other coil and outputs a third voltage corresponding to the difference between the two voltages. A function of acquiring a voltage, a function of inputting the first voltage and the second voltage, calculating a fourth voltage according to a difference between the two voltages by software, and the third voltage and the fourth voltage. Based on the function of diagnosing whether or not the third voltage is normal, and the third voltage when diagnosing that the third voltage is normal and the third voltage when diagnosing that the third voltage is abnormal. 4 voltage Is a program for realizing the function of setting the information on the steering torque function for the calculation is based to calculate.

  According to the present invention, even when an abnormality occurs in a part of the torque sensor, the steering assist torque can be generated based on the alternative steering torque, so that the burden on the driver can be reduced. .

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of the control apparatus of an electric power steering apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a motor drive control part, a motor drive part, and a motor current detection part. It is a figure which shows schematic structure in a steering gear box. It is a schematic block diagram of a torque detection circuit. It is a schematic block diagram of a torque value setting part. It is a figure which shows the relationship between a 1st voltage, a 2nd voltage, a torque detection voltage, and steering torque. It is a flowchart which shows the procedure of the setting process which a voltage value setting part performs. It is a coordinate map which shows the relationship between a 1st voltage and a 2nd voltage. It is a flowchart which shows the procedure of a voltage relationship diagnostic process.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
An electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle. In the present embodiment, the configuration applied to an automobile is used. Illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering shaft 102 and the upper connection shaft 103 are connected via a universal joint 103a, and the upper connection shaft 103 and the lower connection shaft 108 are connected via a universal joint 103b.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106a is formed at the lower end of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is coupled to the lower coupling shaft 108 via a torsion bar 112 (see FIG. 5) in a steering gear box 107. Inside the steering gear box 107, a torque sensor 109 is provided as an example of a steering torque detecting means for detecting the steering torque of the steering wheel 101 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106.

The steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a speed reducing mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106.
Further, the steering device 100 includes a motor current detection unit 33 (see FIG. 2) that detects the magnitude and direction of the actual current that actually flows through the electric motor 110, and a motor voltage detection unit that detects the voltage across the terminals of the electric motor 110. 160.
The steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives the output value of the torque sensor 109, the output value of the vehicle speed sensor 170 that detects the vehicle speed of the vehicle, and the output value of the motor voltage detector 160.

  The electric power steering apparatus 100 configured as described above detects the steering torque applied to the steering wheel 101 by the torque sensor 109, drives the electric motor 110 according to the detected torque, and generates the electric motor 110. Torque is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10 of the electric power steering device 100.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 calculates a target auxiliary torque based on the steering torque, and calculates a target current necessary for the electric motor 110 to supply the target auxiliary torque, and a target current calculation unit 20. The motor drive control part 31 which controls the action | operation of the electric motor 110 based on the target electric current calculated by this, and the motor drive part 32 which drives the electric motor 110 are provided. Further, the control device 10 includes a motor current detection unit 33 that detects an actual current that actually flows through the electric motor 110, and the target current calculation unit 20 and the like detect the actual current detected by the motor current detection unit 33. Is converted into an output signal.
In addition, the control device 10 includes a torque value setting unit 35 that outputs a torque signal Td toward the target current calculation unit 20 based on a signal input from a torque detection circuit 250 described later. The torque value setting unit 35 will be described in detail later.

Next, the target current calculation unit 20 will be described in detail. FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current that serves as a reference for setting the target current, an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110, and It has. The target current calculation unit 20 estimates the rotation speed of the electric motor 110 based on the damper compensation current calculation unit 23 that calculates a current that limits the rotation of the motor, the motor current signal Im, and the motor terminal voltage signal Vm. And a motor rotation speed estimation unit 24. Further, the target current calculation unit 20 includes a final target current determination unit 25 that determines a final target current based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. I have.

The target current calculation unit 20 includes a vehicle speed signal v obtained by converting the vehicle speed detected by the vehicle speed sensor 170 into an output signal, and a motor obtained by converting the voltage detected by the motor voltage detection unit 160 into an output signal. The terminal voltage signal Vm, the motor current signal Im obtained by converting the actual current detected by the motor current detection unit 33 into an output signal, and the torque signal Td output from the torque value setting unit 35 are input.
Since a signal from the vehicle speed sensor 170 or the like is input to the control device 10 as an analog signal, the analog signal is converted into a digital signal by an A / D conversion unit (not shown) and is taken into the target current calculation unit 20. .

  The base current calculation unit 21 calculates a base current based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170, and information on the base current is obtained. The base current signal Ims including it is output. Note that the base current calculation unit 21 detects the detected torque signal on a map indicating the correspondence between the torque signal Ts, the vehicle speed signal v, and the base current, which is previously created based on an empirical rule and stored in the ROM, for example. The base current is calculated by substituting Ts and the vehicle speed signal v.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current for canceling out the moment of inertia of the electric motor 110 and the system based on the torque signal Td and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on this current. Output. The inertia compensation current calculation unit 22 is detected on a map showing the correspondence between the torque signal Td, the vehicle speed signal v, and the inertia compensation current, which is created based on an empirical rule and stored in the ROM, for example. An inertia compensation current is calculated by substituting the torque signal Td and the vehicle speed signal v.

The damper compensation current calculation unit 23 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nm of the electric motor 110, and information on this current A damper compensation current signal Id including is output. The damper compensation current calculation unit 23 indicates the correspondence between the torque compensation signal Td, the vehicle speed signal v, the rotation speed signal Nm, and the damper compensation current, which are previously created based on empirical rules and stored in the ROM, for example. A damper compensation current is calculated by substituting the detected torque signal Td, vehicle speed signal v, and rotational speed signal Nm into the map.
The motor rotation speed estimation unit 24 estimates the rotation speed of the electric motor 110 based on the actual current detected by the motor current detection unit 33 and the voltage detected by the motor voltage detection unit 160 (see FIG. 1). To do.

  The final target current determination unit 25 includes the base current signal Ims output from the base current calculation unit 21, the inertia compensation current signal Is output from the inertia compensation current calculation unit 22, and the damper compensation output from the damper compensation current calculation unit 23. A final target current is determined based on the current signal Id, and a target current signal IT including information on this current is output. For example, the final target current determination unit 25 previously created a compensation current obtained by adding the inertia compensation current to the base current and subtracting the damper compensation current based on an empirical rule, and stored it in the ROM. The final target current is calculated by substituting it into a map indicating the correspondence between the compensation current and the final target current.

Next, the motor drive control unit 31, the motor drive unit 32, and the motor current detection unit 33 will be described in detail.
FIG. 4 is a schematic configuration diagram of the motor drive control unit 31, the motor drive unit 32, and the motor current detection unit 33.
The motor drive control unit 31 performs feedback control based on the deviation between the target current calculated by the target current calculation unit 20 and the actual current supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110 are included.

The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current calculated by the target current calculating unit 20 and the actual current detected by the motor current detecting unit 33, and the deviation becomes zero. And a feedback (F / B) processing unit 42 for performing feedback processing.
The deviation calculation unit 41 outputs a deviation value between the target current signal IT, which is an output value from the target current calculation unit 20, and the motor current signal Im, which is an output value from the motor current detection unit 33, as a deviation signal 41a.

The feedback (F / B) processing unit 42 performs feedback control so that the target current and the actual current match. For example, the input deviation signal 41a is proportionally processed by a proportional element. A signal obtained by the integration processing by the integration element is output, and the addition calculation unit adds these signals to generate and output a feedback processing signal 42a.
The PWM signal generation unit 60 generates the PWM signal 60a based on the output value from the feedback control unit 40, and outputs the generated PWM signal 60a.

The motor drive unit 32 drives a motor drive circuit 70 in which four power field effect transistors are connected in an H-type bridge circuit configuration, and drives the gates of two field effect transistors selected from the four. And a gate drive circuit unit 80 for switching the field effect transistor. The gate drive circuit unit 80 selects two field effect transistors according to the steering direction of the steering wheel 101 based on the PWM signal (drive control signal) 60a output from the PWM signal generation unit 60, and selects the selected 2 The field effect transistors are switched.
The motor current detection unit 33 detects the value of the motor current (armature current) flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor 71 connected in series with the motor drive circuit 70, and outputs the motor current signal Im. To do.

Next, the torque sensor 109 will be described.
The torque sensor 109 has two coils 121 and 122, which will be described later, a mechanism for changing the inductances L1 and L2 of the two coils 121 and 122 according to the operation of the steering wheel 101, and the inductances L1 and L2. And a torque detection circuit 250 (see FIG. 6) that outputs a voltage corresponding to the steering torque based on the change.

FIG. 5 is a diagram showing a schematic configuration in the steering gear box 107.
The lower connecting shaft 108 is rotatably supported with respect to the steering gear box 107 via a bearing 113, and the pinion shaft 106 is rotatably supported with respect to the steering gear box 107 via a bearing 114. . The lower connecting shaft 108 and the pinion shaft 106 are coaxially connected via a torsion bar 112.

A serration 106b is provided on the outer peripheral surface of the end portion side of the lower coupling shaft 108 in the axial direction of the pinion shaft 106, and a cylindrical core 115 is fitted to the serration 106b. The core 115 can move in the axial direction of the pinion shaft 106.
The lower connecting shaft 108 is provided with a cylindrical slider pin 108a that protrudes from the outer peripheral surface in a direction orthogonal to the axial direction. Further, the pinion shaft 106 is formed with a long hole 106c which is elongated in the circumferential direction at a portion on the end side on the lower connecting shaft 108 side, and the core 115 is formed in a direction having an angle with respect to the axial direction. An elongated slot 115a is formed. The slider pin 108a of the lower connecting shaft 108 is fitted into the long hole 106c and the long hole 115a so as to penetrate the pinion shaft 106 and the core 115.

  Two coils 121 and 122 arranged in the axial direction so as to face the outer peripheral surface of the core 115 are disposed outside the core 115 in the steering gear box 107 via the outer peripheral surface of the core 115 and a gap. Is provided. The two coils 121 and 122 are arranged on opposite sides with respect to the axial movement center of the core 115.

  As described above, the configured torque sensor 109 operates as follows. That is, when a torsional force is applied to the lower connecting shaft 108, a rotational force is transmitted to the pinion shaft 106 via the torsion bar 112. However, the torsion bar 112 is elastically deformed and the lower connecting shaft 108 and the pinion shaft 106 are A relative displacement in the rotational direction occurs between the two. The relative displacement in the rotational direction moves the core 115 in the axial direction through the fitting between the slider pin 108a of the lower connecting shaft 108 and the elongated hole 115a of the core 115. When the core 115 moves in the axial direction, the area surrounding the outer peripheral surface of each of the coils 121 and 122 changes, and when the area on one coil side of the coils 121 and 122 increases, the area on the other coil side decreases. . When the area surrounding the outer periphery of the coil core 115 increases, the magnetic loss increases and the coil inductance decreases. Conversely, when the area surrounding the coil core 115 decreases, the magnetic loss decreases and the coil inductance increases. Therefore, when the torque that moves the core 115 toward the coil 121 acts, the inductance L1 of the coil 121 decreases and the inductance L2 of the coil 122 increases. On the contrary, when the torque that moves the core 115 toward the coil 122 acts, the inductance L1 of the coil 121 increases and the inductance L2 of the coil 122 decreases.

Next, the torque detection circuit 250 will be described.
FIG. 6 is a schematic configuration diagram of the torque detection circuit 250. For example, the torque detection circuit 250 is configured on the same control board as the control device 10.
One end of the coil 121 and one end of the coil 122 are connected to the torque detection circuit 250, and each end is connected to the emitter terminal of the transistor 253 via resistors 251 and 252, respectively. In the transistor 253, a constant voltage is applied to the collector terminal, and an AC voltage is input to the base terminal.
In addition, the other end of the coil 121 and the other end of the coil 122 are connected, a signal line extends from the connection portion, and the signal line is connected to a connection terminal of the torque detection circuit 250. The other end of the coil 121 and the other end of the coil 122 are grounded.

A signal line 256 extending from a terminal to which one end of the coil 121 is connected is connected to a smoothing circuit 258 via a capacitor 257, and a signal line 259 extending from a terminal to which one end of the coil 122 is connected is smoothed via a capacitor 260. The circuit 261 is connected.
In the above configuration, a bridge circuit is configured by the coils 121 and 122 and the resistors 251 and 252, an oscillation voltage is input to the bridge circuit, and the output voltage is smoothed by the smoothing circuits 258 and 261. The first voltage V1 is output from the smoothing circuit 261, and the second voltage V2 is output.

  The first voltage V1 is applied to an inverting input terminal of a differential amplifier 265 that is an operational amplifier (differential amplifier) via a resistor 262, and the second voltage V2 is applied to a non-inverting input terminal of the differential amplifier 265 via a resistor 263. Entered. The differential amplifier 265 functions as a differential amplifier with negative feedback applied by a resistor 266. The bias voltage V0 (for example, 2.5 V) is input to the non-inverting input terminal of the differential amplifier 265. With this configuration, the differential amplifier 265 multiplies the difference between the first voltage V1 and the second voltage V2 by an amplification factor A, and adds the bias voltage V0 to the torque detection voltage VT (= (V2−V1) × A + V0). ). Then, the torque detection voltage VT is input to the control device 10. Further, the first voltage V <b> 1 and the second voltage V <b> 2 are output from the torque detection circuit 250 to the control device 10.

Next, the torque value setting unit 35 of the control device 10 will be described.
FIG. 7 is a schematic configuration diagram of the torque value setting unit 35.
The torque value setting unit 35 has a voltage calculation unit 351 that calculates a torque voltage by software based on the first voltage V1 and the second voltage V2, and outputs the calculation result as the torque calculation voltage VTFS. The torque value setting unit 35 also outputs a torque signal Td output to the target current calculation unit 20 based on the torque calculation voltage VTFS input from the voltage calculation unit 351 and the torque detection voltage VT input from the torque detection circuit 250. The voltage value setting unit 352 that sets which of the torque detection voltage VT and the torque calculation voltage VTFS is used as the control voltage serving as the basis of the control, and the control voltage output from the voltage value setting unit 352 is converted into torque And a converter 353 that outputs the torque signal Td.

The voltage calculation unit 351 calculates the torque calculation voltage VTFS by substituting the input first voltage V1 and second voltage V2 into the following equation (1).
VTFS = (V2−V1) × A + V0 (1)
A is the above-described amplification degree, and V0 is the same as the bias voltage.
That is, the differential amplifier 265 outputs the torque detection voltage VT in hardware, whereas the voltage calculation unit 351 derives the torque calculation voltage VTFS in software. In other words, the differential amplifier 265 of the torque detection circuit 250 inputs the first voltage and the second voltage, and outputs the torque detection voltage VT as a third voltage corresponding to the difference between the two voltages by hardware. On the other hand, the voltage calculation unit 351 of the torque value setting unit 35 inputs the first voltage and the second voltage, and calculates the calculation voltage VTFS as the fourth voltage according to the difference between the two voltages by software. Since the first voltage V1 and the second voltage V2 are input as analog signals, these analog signals are converted into digital signals by an A / D conversion unit (not shown).

  The voltage value setting unit 352 receives the torque detection voltage VT output from the torque detection circuit 250, the first voltage V1 and the second voltage V2, the calculation voltage VTFS output from the voltage calculation unit 351, and the like. Then, the voltage value setting unit 352 sets which of the torque detection voltage VT and the torque calculation voltage VTFS is used as the control voltage as the voltage that is the basis of the torque signal Td output to the target current calculation unit 20. A setting process is performed for setting or outputting an assist OFF signal for stopping the driving of the electric motor 110 by determining that an abnormality has occurred in the torque sensor 109 or setting a signal to be output to the conversion unit 353. Execute. This setting process will be described in detail later.

  When the torque detection voltage VT or the torque calculation voltage VTFS is input as the control voltage from the voltage value setting unit 352 as the control voltage, the conversion unit 353 converts the control voltage into a torque signal Td corresponding to the steering torque. And output to the target current calculation unit 20. Further, the converter 353 sets the current supplied to the electric motor 110 to the target current calculator 20 and the motor drive controller 31 to zero when the assist OFF signal is input from the voltage value setting unit 352. A signal to prohibit driving is output.

Hereinafter, a method for recognizing the steering torque based on the control voltage input from the voltage value setting unit 352 will be described.
FIG. 8 is a diagram illustrating the relationship between the first voltage V1, the second voltage V2, the torque detection voltage VT, and the steering torque. In the coordinates of FIG. 8, the vertical axis represents voltage and the horizontal axis represents steering torque. The right direction of the horizontal axis is the right steering torque, the left direction is the left steering torque, and the origin 0 is the neutral point. FIG. 8 is when the torque sensor 109 operates normally.

As shown in FIG. 8A, when the right steering torque increases, the core 115 moves to the coil 121 side due to the relative rotation of the lower connecting shaft 108 and the pinion shaft 106, and the inductance L2 of the coil 122 increases. Since the induced electromotive force is increased and the inductance L1 of the coil 121 is decreased to reduce the induced electromotive force, the second voltage V2 is increased and the first voltage V1 is decreased. On the other hand, when the left steering torque is increased, the second voltage V2 is decreased and the first voltage V1 is increased. Therefore, the torque detection voltage VT, which is the output of the differential amplifier 265 obtained by multiplying the difference between the first voltage V1 and the second voltage V2 by A and adding a bias voltage, is, as shown in FIG. Becomes a slope line rising rightward through the bias voltage V0. Then, the steering torque can be recognized from the torque detection voltage VT based on the slope line of the torque detection voltage VT shown in the graph of FIG.
Then, the conversion unit 353 outputs a torque signal Td corresponding to the recognized steering torque to the target current calculation unit 20.

Next, setting processing performed by the voltage value setting unit 352 will be described using a flowchart.
FIG. 9 is a flowchart illustrating a procedure of setting processing performed by the voltage value setting unit 352. The voltage value setting unit 352 periodically performs this setting process.
First, voltage value setting unit 352 diagnoses whether torque detection voltage VT is abnormal based on torque detection voltage VT and operation voltage VTFS (step (hereinafter simply referred to as “S”) 501. ). This is because the torque detection voltage VT is compared with the torque calculation voltage VTFS, and when the difference is less than a predetermined value, it is determined that the torque detection voltage VT is normal, and the difference is determined in advance. When the value is equal to or greater than the value, the torque detection voltage VT is determined to be abnormal. Since the torque detection voltage VT is input as an analog signal, the analog signal is converted into a digital signal by an A / D conversion unit (not shown).

  Thereafter, it is determined whether or not the torque detection voltage VT is determined to be abnormal as a result of the diagnosis processing in S501 (S502). If a negative determination is made in S502, that is, if it is determined that the torque detection voltage VT is normal, the torque detection voltage VT is set as a control voltage, and the torque detection voltage VT is output to the conversion unit 353. (S503). On the other hand, when an affirmative determination is made in S502, that is, when it is determined that the torque detection voltage VT is abnormal, the voltage for diagnosing whether or not the relationship between the first voltage V1 and the second voltage V2 is normal. A relationship diagnosis process is performed (S504). This voltage relationship diagnosis process will be described in detail later.

  And it is discriminate | determined as a result of the voltage relationship diagnostic process of S504 whether the relationship between the 1st voltage V1 and the 2nd voltage V2 was determined to be normal (S505). If an affirmative determination is made in S505, that is, if it is determined that the relationship between the first voltage V1 and the second voltage V2 is normal, the first voltage V1 output from the torque detection circuit 250 and the second voltage V2 The voltage V2 is determined to be a reliable value, the calculated voltage VTFS derived from these values is set as a control voltage, and the torque calculated voltage VTFS is output to the conversion unit 353 (S506). On the other hand, if a negative determination is made in S505, that is, if it is determined that the relationship between the first voltage V1 and the second voltage V2 is abnormal, it is determined that an abnormality has occurred in the torque sensor 109 and the electric motor is operated. An assist OFF signal for stopping the driving of the motor 110 is output to the conversion unit 353 (S507).

Next, the voltage relationship diagnosis process described above will be described.
FIG. 10 is a coordinate map showing the relationship between the first voltage V1 and the second voltage V2.
This coordinate map is stored in the ROM of the control device 10, and the first voltage V1 in the normal state is set to the xy coordinates with the x axis set to the first voltage V1 and the y axis set to the second voltage V2. An ideal relationship characteristic curve L of the second voltage V2 is obtained in advance, and an upper limit curve Lu and a lower limit curve Ld having a predetermined width with respect to the ideal relationship characteristic curve L are set.

  Since the first voltage V1 and the second voltage V2 move symmetrically, the ideal relationship characteristic curve L in FIG. 10 is a curve with a slope falling to the right, and is an upper limit set above and below the ideal relationship characteristic curve L. The widths of the curve Lu and the lower limit curve Ld are set such that no erroneous detection occurs. The first voltage V1 and the second voltage V2 are voltages branched on the downstream side of the smoothing circuit 258 and the smoothing circuit 261, respectively. Therefore, the ideal relationship characteristic curve L is a curve including the characteristics of the smoothing circuits 258 and 261. The upper limit curve Lu and the lower limit curve Ld are curves in consideration of the characteristics of the smoothing circuits 258 and 261.

Hereinafter, the procedure of the voltage relationship diagnosis process performed by the voltage value setting unit 352 will be described using a flowchart. FIG. 11 is a flowchart showing the procedure of the voltage relationship diagnosis process.
First, the voltage value setting unit 352 derives a value V2u on the upper limit curve Lu and a value V2d on the lower limit curve Ld corresponding to the first voltage V1 (S601). Thereafter, it is determined whether or not the second voltage V2 is not less than V2d and not more than V2u (S602). If an affirmative determination is made in S602, it is determined that the relationship between the first voltage V1 and the second voltage V2 is normal (S603). On the other hand, if a negative determination is made in S602, it is determined that the relationship between the first voltage V1 and the second voltage V2 is abnormal (S604). By performing this voltage relationship diagnosis processing, the voltage value setting unit 352 can easily grasp, for example, that one of the smoothing circuit 258 and the smoothing circuit 261 has failed.

  In the steering device 100 configured as described above, when the voltage value setting unit 352 performs the above-described setting process, the torque detection voltage VT output from the torque detection circuit 250 is determined to be normal. Torque detection voltage VT is output to conversion unit 353 to be used as a control voltage. On the other hand, if it is determined that the torque detection voltage VT is abnormal, it is determined that an abnormality has occurred in the differential amplifier 265 that outputs the torque detection voltage VT, and the torque detection voltage VT is not used as a control voltage. To. When it is determined that an abnormality has occurred in the differential amplifier 265, when the relationship between the first voltage V1 and the second voltage V2 is normal, the first voltage V1 and the second voltage V2 are normal. As an example, the torque calculation voltage VTFS is used as a control voltage instead of the torque detection voltage VT. Thereby, even if a failure occurs in a part of the torque sensor 109, the assist can be switched and continued, and the burden on the driver can be reduced.

  When the torque calculation voltage VTFS is used as the control voltage, it is also preferable to set the assist amount by the electric motor 110 to a limit that is limited to the assist amount when the torque detection voltage VT is used as the control voltage. is there. As means for limiting the assist amount, an increase in the control dead zone, a decrease in the assist gain, and the like can be considered.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 31 ... Motor drive control part, 32 ... Motor drive part, 33 ... Motor current detection part, 35 ... Torque value setting part, 351 ... Voltage calculation part, 352 ... Voltage value setting , 353 ... conversion unit, 100 ... electric power steering device, 101 ... steering wheel, 109 ... torque sensor, 110 ... electric motor, 160 ... motor voltage detector, 170 ... vehicle speed sensor

Claims (6)

Calculating means for calculating a target current to be supplied to the electric motor based on the steering torque;
A first coil and a second coil whose inductances change in opposite directions according to the steering torque;
An output means for inputting a first voltage based on an inductance change of the first coil and a second voltage based on an inductance change of the second coil, and outputting a third voltage according to a difference between the two voltages by hardware;
Calculating means for inputting the first voltage and the second voltage and calculating a fourth voltage according to a difference between the two voltages by software;
Diagnostic means for diagnosing whether or not the third voltage is normal based on the third voltage and the fourth voltage;
The steering based on the calculation means calculating the third voltage when the diagnosis means diagnoses that the third voltage is normal, and the fourth voltage when the diagnosis means is abnormal. Setting means for setting as information about torque;
An electric power steering apparatus comprising: The output means is a differential amplifier;
The calculation means calculates the fourth voltage by multiplying a value obtained by subtracting the second voltage and the first voltage by an amplification factor of the differential amplifier and adding a bias voltage of the differential amplifier. The electric power steering apparatus according to claim 1. Voltage relationship diagnosis means for diagnosing whether or not the correlation between the first voltage and the second voltage is normal based on the first voltage and the second voltage;
When the diagnosis unit diagnoses that the third voltage is abnormal, the setting unit diagnoses that the correlation between the first voltage and the second voltage is normal. The fourth voltage is set as information related to the steering torque based on the calculation by the calculation means, and when the correlation between the first voltage and the second voltage is diagnosed, the electric motor The electric power steering apparatus according to claim 1 or 2, wherein an assist stop signal for stopping driving of the motor is set. A first coil and a second coil whose inductances change in opposite directions according to the steering torque;
An output means for inputting a first voltage based on an inductance change of the first coil and a second voltage based on an inductance change of the second coil, and outputting a third voltage according to a difference between the two voltages by hardware;
Calculating means for calculating a target current to be supplied to the electric motor based on the third voltage output by the output means;
An electric power steering apparatus comprising:
Calculating means for inputting the first voltage and the second voltage and calculating a fourth voltage according to a difference between the two voltages by software;
Diagnostic means for diagnosing whether or not the third voltage is normal based on the third voltage and the fourth voltage;
Further comprising
When the diagnosis unit diagnoses that the third voltage is abnormal, the calculation unit is based on the fourth voltage instead of the third voltage when calculating the target current. Electric power steering device. Calculating means for calculating a target current to be supplied to the electric motor based on the steering torque;
A first coil and a second coil whose inductances change in opposite directions according to the steering torque;
An output means for inputting a first voltage based on an inductance change of the first coil and a second voltage based on an inductance change of the second coil, and outputting a third voltage according to a difference between the two voltages by hardware;
A control method for an electric power steering apparatus comprising:
The first voltage and the second voltage are input, a fourth voltage corresponding to the difference between the two voltages is calculated by software,
Diagnosing whether the third voltage is normal based on the third voltage and the fourth voltage,
When the third voltage is diagnosed as normal, the third voltage is used as the information about the steering torque based on the calculation by the calculation means when the third voltage is diagnosed as abnormal. A method for controlling an electric power steering apparatus, comprising: setting. On the computer,
A function of calculating a target current to be supplied to the electric motor based on the steering torque;
The first voltage based on the inductance change of one of the pair of coils whose inductances change in opposite directions according to the steering torque and the second voltage based on the inductance change of the other coil are input to both voltages. A function of acquiring the third voltage from a circuit that outputs a third voltage according to the difference between
A function of inputting the first voltage and the second voltage and calculating a fourth voltage corresponding to a difference between the two voltages by software;
A function of diagnosing whether or not the third voltage is normal based on the third voltage and the fourth voltage;
Information related to the steering torque based on the calculation of the third voltage when the third voltage is diagnosed as normal and the fourth voltage when the third voltage is diagnosed as abnormal. Program to realize the function to be set as.

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