JP6222895B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

2. Description of the Related Art In recent years, there has been proposed an electric power steering device that controls the amount of current that flows through an electric motor according to the magnitude of the steering force of a steering wheel detected by a torque sensor.
For example, the electric power steering device described in Patent Document 1 is an electric motor that assists the steering force of the steering by supplying power to the steering mechanism of the steering, a torque sensor that detects the steering force of the steering, and a detection by this torque sensor. And a control circuit for controlling the amount of current flowing through the electric motor in accordance with the magnitude of the steering force. The torque sensor includes a torsion bar that coaxially connects the input shaft and the output shaft, a magnet attached to the end of the input shaft, a set of magnetic yokes attached to the end of the output shaft, and this set of The magnetic sensor is configured to detect the magnetic flux density generated between the magnetic yokes.

JP 2003-149062 A

The output value from the torque sensor includes mechanical frictional resistance generated in a steering system such as a steering wheel and an input shaft as a disturbance. Therefore, a phenomenon (hysteresis) occurs in which the output value of the torque sensor when steering the steering wheel from left to right and the output value of the torque sensor when steering from right to left are different.
Therefore, it is desirable to improve steering feeling and safety by controlling the amount of current supplied to the electric motor in consideration of hysteresis.

  For this purpose, the present invention provides a detection means for detecting a value corresponding to the steering torque of the steering wheel, and a target current calculation for calculating a target current supplied to the electric motor based on the detection value detected by the detection means. Means for calculating the steering torque using a reference target current corresponding to the detection value detected by the detection means and an adjustment value corresponding to the detection value detected by the detection means. When the absolute value is large, the absolute value of the target current is smaller than the reference target current when the steering wheel is in the direction of additional turning of the steering wheel, and when the absolute value is in the direction of return of the steering wheel, the reference target is reached. The electric power steering apparatus is characterized in that the target current is calculated to be larger than the current.

Here, the target current calculation means uses the reference target current and the adjustment value, and when the steering torque is small and the absolute value of the target current is in the direction of increasing the steering wheel. The target current may be calculated so as to be smaller than the reference target current when the steering target is larger than the reference target current and in the steering wheel return direction.
In addition, the adjustment value of the target current calculation unit may be reversed in sign when the absolute value of the detection value detected by the detection unit is smaller or larger than a predetermined value.

  The target current calculation means includes a reference target current calculation means for calculating the reference target current, a target current adjustment means for setting the adjustment value, and an addition means for adding the reference target current and the adjustment value. The target current adjusting means includes a determining means for determining a correction amount based on a detection value detected by the detecting means, and a correction amount determined by the determining means in accordance with an operation direction of the steering wheel. And output means for correcting and outputting the corrected correction amount as the adjustment value.

  Further, when the steering torque direction is positive when one direction of the steering wheel is positive and negative when the other rotational direction is negative, the determination means of the target current calculation means is the correction The sign of the amount is determined to be negative if the absolute value of the detected value detected by the detecting means is smaller than a predetermined value, and positive if it is larger, and the output means increases the steering torque. If the steering torque is decreasing, the value obtained by multiplying the correction amount by -1 may be used as the adjustment value, and the correction amount may be used as the adjustment value.

  According to the present invention, since the amount of current supplied to the electric motor is controlled in consideration of hysteresis, the steering feeling can be improved and the safety can be improved.

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 figure which shows the correlation of the reference target current and steering torque which a reference target current calculation part calculates. It is a schematic block diagram of a reference target current calculation part. It is a schematic block diagram of a control part. It is a figure which shows the phenomenon (hysteresis) from which the operation direction of a steering wheel differs from the output value from a torque detection part. It is a schematic block diagram of a target current adjustment part. It is a figure which shows the relationship between a detected torque signal and a correction amount. It is a flowchart which shows the procedure of the correction amount determination process which a correction amount determination part performs. It is a flowchart which shows the procedure of the increase / decrease degree determination process which an increase / decrease degree determination part performs. It is a flowchart which shows the procedure of the output process which an output part performs. It is a figure which shows the relationship between the steering torque and target current in the steering device which concerns on this Embodiment.

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 device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  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 106 a is formed at the lower end portion 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 connected to the lower connection shaft 108 via a torsion bar in a steering gear box 107. Inside the steering gear box 107, a torque sensor 109 that outputs an electrical signal (for example, a voltage signal) corresponding to the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106 is provided.

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. Electric motor 110 according to the present embodiment is a three-phase brushless motor. The magnitude and direction of the actual current that actually flows through the electric motor 110 is detected by the motor current detector 33 (see FIG. 6). The reduction mechanism 111 includes a worm wheel (not shown) that rotates together with the pinion shaft 106, and a worm gear that is attached to the output shaft of the electric motor 110 and meshes with the worm wheel.
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 and the output value of the vehicle speed sensor 170 that detects the vehicle speed Vc, which is the moving speed of the automobile.

  The steering device 100 configured as described above detects a value corresponding to the steering torque T applied to the steering wheel 101 based on an output from the torque sensor 109, and the electric motor 110 based on the detected value. And the torque generated by the electric motor 110 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 steering device 100.
The control device 10 is an arithmetic logic operation circuit including a CPU 11, a ROM 12, a RAM 13, and the like.
The control device 10 receives an electric signal output from the torque sensor 109 and a vehicle speed signal v obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal.
Then, the control device 10 detects a value corresponding to the steering torque T based on a signal input from the torque sensor 109, and based on an output value (detected torque signal Tp) from the torque detector 310. The target auxiliary torque is calculated, the target current calculating unit 20 for calculating the target current IT necessary for the electric motor 110 to supply the target auxiliary torque, and the target current IT calculated by the target current calculating unit 20 is used. And a control unit 30 that performs feedback control and the like.

First, the torque detector 310 will be described in detail.
The torque detector 310 calculates the steering torque T based on the signal input from the torque sensor 109, and outputs the detected torque signal Tp obtained by converting the calculated steering torque T into an electric signal (voltage signal) to the target current calculator 20. Output. A map indicating the relationship between the electrical signal output from the torque sensor 109 and the steering torque T is stored in the ROM 12, and the torque detection unit 310 substitutes the electrical signal from the torque sensor 109 in this map. A steering torque T is calculated. Alternatively, a function indicating the relationship between the electric signal from the torque sensor 109 and the steering torque T is incorporated, and the torque detector 310 calculates the steering torque T by substituting the electric signal from the torque sensor 109 into this function. May be. Note that the torque detection unit 310 sets the torsion bar twist amount to zero and outputs the steering torque T in the right rotation direction as a positive value and the steering torque T in the left rotation direction as a negative value from the state.

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 reference target current calculation unit 21 that calculates a reference target current IB that serves as a reference in setting the target current, and an adjustment current that adjusts the reference target current IB calculated by the reference target current calculation unit 21. A target current adjustment unit 22 that sets (calculates) IA; and an addition unit 23 that adds the reference target current IB calculated by the reference target current calculation unit 21 and the adjustment current set by the target current adjustment unit 22. Yes.

FIG. 4 is a diagram showing a correlation between the reference target current IB calculated by the reference target current calculation unit 21 and the steering torque T. Although FIG. 4 illustrates the case where the steering torque T is positive, the reference target current IB when the steering torque T is negative is point-symmetric with respect to the reference target current IB and zero when the steering torque T is positive. Become.
The reference target current calculation unit 21 roughly determines the reference target current based on the output value (detected torque signal Tp) from the torque detection unit 310 so that the steering torque T and the reference target current IB have the relationship shown in FIG. IB is calculated. Hereinafter, the reference target current calculation unit 21 will be described in detail.

FIG. 5 is a schematic configuration diagram of the reference target current calculation unit 21.
The reference target current calculation unit 21 calculates a base current calculation unit 211 that calculates a reference base current for setting the reference target current IB, and inertia compensation current calculation that calculates a current for canceling the moment of inertia of the electric motor 110. And a damper compensation current calculation unit 213 for calculating a current for limiting the rotation of the motor. The reference target current calculation unit 21 includes a reference target current determination unit 215 that determines the reference target current IB based on outputs from the base current calculation unit 211, the inertia compensation current calculation unit 212, the damper compensation current calculation unit 213, and the like. I have. Further, the reference target current calculation unit 21 includes a phase compensation unit 216 that performs phase compensation of the torque signal Tp.

  The base current calculation unit 211 calculates a base current based on the torque signal Ts in which the torque signal Tp is phase-compensated by the phase compensation unit 216 and the vehicle speed signal v from the vehicle speed sensor 170, and information on this base current is obtained. A base current signal Imb including the same is output. The base current calculation unit 211 may detect 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 12, for example. The base current is calculated by substituting Tp and the vehicle speed signal v.

  The inertia compensation current calculation unit 212 calculates an inertia compensation current for canceling the inertia moment of the electric motor 110 and the system based on the torque signal Tp and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on the current. Output. Note that the inertia compensation current calculation unit 212 is detected in, for example, a map indicating the correspondence between the torque signal Tp, the vehicle speed signal v, and the inertia compensation current, which is created based on an empirical rule and stored in the ROM 12 in advance. An inertia compensation current is calculated by substituting the torque signal Tp and the vehicle speed signal v.

  The damper compensation current calculation unit 213 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Tp, the vehicle speed signal v, and the rotation speed signal Nms 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 213 indicates the correspondence between the torque signal Tp, the vehicle speed signal v, the rotation speed signal Nms, and the damper compensation current, which are created based on empirical rules in advance and stored in the ROM 12, for example. A damper compensation current is calculated by substituting the detected torque signal Tp, vehicle speed signal v, and rotation speed signal Nms into the map.

  The reference target current determination unit 215 determines the reference target current based on the base current calculated by the base current calculation unit 211, the inertia compensation current calculated by the inertia compensation current calculation unit 212, and the damper compensation current calculated by the damper compensation current calculation unit 213. IB is determined, and a reference target current signal Ib including information on this current is output. The reference target current determination unit 215, for example, 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 in the ROM 12. The target current is calculated by substituting it into a map showing the correspondence between the compensation current and the target current.

Although the target current adjustment unit 22 will be described in detail later, the target current adjustment unit 22 determines the adjustment current IA and outputs an adjustment current signal Ia including information on the adjustment current IA.
The adding unit 23 adds the reference target current IB calculated by the reference target current calculating unit 21 and the adjustment current IA set by the target current adjusting unit 22, and outputs the added current to the control unit 30 as the target current IT. . In other words, the adding unit 23 finally adds a value obtained by adding the reference target current signal Ib that is the output value from the reference target current calculating unit 21 and the adjustment current signal Ia that is the output value from the target current adjusting unit 22. Output as target current addition signal It.

The target current calculation unit 20 receives the torque signal Tp, the vehicle speed signal v, and the rotation speed signal Nms obtained by converting the rotation speed Nm of the electric motor 110 into an output signal. The rotational speed signal Nms is, for example, a sensor configured to detect a rotational position of a rotor (rotor) of the electric motor 110 that is a three-phase brushless motor (for example, a rotor configured by a resolver, a rotary encoder, or the like that detects the rotational position of the rotor). It can be exemplified that the output signal of the position detection circuit is obtained by differentiating.
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. .

Next, the control unit 30 will be described in detail. FIG. 6 is a schematic configuration diagram of the control unit 30.
The control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and a motor current detection unit 33 that detects the actual current Im that actually flows through the electric motor 110. And have.
The motor drive control unit 31 is based on a deviation between the target current IT finally determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 that performs feedback control, and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current IT finally determined by the target current calculating unit 20 and the actual current Im detected by the motor current detecting unit 33, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.
The deviation calculation unit 41 outputs a deviation value between the target current addition signal It that is an output value from the target current calculation unit 20 and the motor current signal Ims that 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 IT and the actual current Im coincide with each other. For example, the input deviation signal 41a is proportionally processed with a proportional element. A signal is output, a signal obtained by integration processing by an integration element is output, and these signals are added by an addition operation unit 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 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32, and converts the detected actual current Im into a motor current signal Ims. And output.

  In the steering device 100 configured as described above, the output value from the torque sensor 109 includes mechanical frictional resistance generated in the steering system such as the steering wheel 101 and the lower connecting shaft 108 as a disturbance. Therefore, the output value of the torque sensor 109 when steering the steering wheel 101 from left to right (hereinafter sometimes referred to as “right rotation”) and the output value when steering from the right to left (hereinafter referred to as “left rotation”). A phenomenon (hysteresis) different from the output value of the torque sensor 109 occurs.

FIG. 7 is a diagram illustrating a phenomenon (hysteresis) in which the operation direction of the steering wheel 101 and the output value Tp from the torque detection unit 310 are different.
Since the output value of the torque sensor 109 differs depending on the operation direction of the steering wheel 101, the output value Tp (detected torque signal Tp) from the torque detector 310 differs depending on the operation direction of the steering wheel 101. Therefore, as shown in FIG. 7, even if the steering torque T of the steering wheel 101 is the same, the output value Tp from the torque detection unit 310 when the steering wheel 101 rotates counterclockwise is when the steering wheel 101 rotates clockwise. Becomes larger than the output value Tp from the torque detection unit 310.
In view of such matters, in the steering device 100 according to the present embodiment, the reference target current IB that changes in accordance with the detected torque signal Tp output from the torque detector 310 as shown in FIG. The target current adjusting unit 22 is provided to correct the corrected value.

FIG. 8 is a schematic configuration diagram of the target current adjustment unit 22.
The target current adjustment unit 22 is based on the correction amount determination unit 221 that determines the correction amount α based on the detected torque signal Tp output from the torque detection unit 310 and the detection torque signal Tp output from the torque detection unit 310. An increase / decrease degree determination unit 222 for determining increase / decrease in the steering torque T. The target current adjustment unit 22 determines the adjustment current IA based on the correction amount α determined by the correction amount determination unit 221 and the increase / decrease of the steering torque T determined by the increase / decrease degree determination unit 222. The output unit 223 outputs an adjustment current signal Ia including information on the determined adjustment current IA to the addition unit 23.

FIG. 9 is a diagram showing the relationship between the detected torque signal Tp and the correction amount α.
The correction amount determination unit 221 determines the correction amount α based on the detected torque signal Tp output from the torque detection unit 310. For example, an optimal correction amount α corresponding to the detected torque signal Tp output from the torque detector 310 based on an empirical rule is previously derived as shown in FIG. A map showing the correspondence between the detected torque signal Tp and the optimum correction amount α is created in advance and stored in the ROM 12. Then, the correction amount determination unit 221 calculates the correction amount α by substituting the detected torque signal Tp into a map that is created in advance and stored in the ROM 12 and indicating the correspondence between the detected torque signal Tp and the correction amount α. To do. Alternatively, the correction amount α may be calculated by substituting the detected torque signal Tp into a relational expression between the detection torque signal Tp and the correction amount α created in advance.

  As shown in FIG. 9, in the present embodiment, the correction amount α is a minus sign when the absolute value of the detected torque signal Tp is smaller than a predetermined value To, and the absolute value of the detected torque signal Tp. If the value is greater than a predetermined value To, it is a plus sign. That is, the sign of the correction amount α is inverted depending on whether the absolute value of the detected torque signal Tp is smaller or larger than the predetermined value To.

The increase / decrease degree determination unit 222 increases / decreases the steering torque T at the current time when the torsion bar twist amount is zero, the right steering torque T is positive, and the left steering torque T is negative. Determine. The increase / decrease degree determination unit 222 determines the increase / decrease in the steering torque T at the present time from the history of the detected torque signal Tp periodically input from the torque detection unit 310.
More specifically, the increase / decrease degree determination unit 222 is an average value of past k detected torque signals Tp including the latest detected torque signal Tp (n) among the detected torque signals Tp stored in the RAM 13. The average value Tpave (n) is calculated this time, and the latest detected torque signal Tp (n) is not included, that is, the past k torque signals Tp inputted before the latest detected torque signal Tp (n) A previous average value Tpave (n−1), which is an average value, is calculated. For example, when k is 2, Tpave (n) = (Tp (n) + Tp (n−1)) / 2, Tpave (n−1) = (Tp (n−1) + Tp (n−2)) / 2.

  Then, the increase / decrease degree determination unit 222 calculates the average value change ΔTpave (= Tpave (n) −Tpave (n−1) obtained by subtracting the previous average value Tpave (n−1) from the current average value Tpave (n). )), The degree of increase or decrease of the steering torque T is determined. The increase / decrease degree determination unit 222 determines that the increase amount is large when the average value change ΔTpave is larger than a predetermined first determination value, and is set when the steering torque T is increasing. Increase determination is set in the RAM 13. On the other hand, the increase / decrease degree determination unit 222 determines that the amount of decrease is large when the average value change ΔTpave is smaller than a predetermined second determination value, and when the steering torque T is decreasing. The decrease determination to be set is set in the RAM 13. Further, when the average value change ΔTpave is equal to or smaller than the first determination value, the increase / decrease degree determination unit 222 clears the increase determination set in the RAM 13 and the average value change ΔTpave is equal to or larger than the second determination value. In the case, the decrease determination set in the RAM 13 is cleared. It can be exemplified that the first determination value is a positive value and the second determination value is a negative value.

  When the increase determination is set in the RAM 13, the output unit 223 sets the current obtained by multiplying the correction amount α determined by the correction amount determination unit 221 by “−1” as the current adjustment current IA (n). At the same time, an electric signal corresponding to the determined adjustment current IA (n) is output as the current adjustment current signal Ia (n). When the reduction determination is set in the RAM 13, the output unit 223 determines the correction amount α determined by the correction amount determination unit 221 as the current adjustment current IA (n) and the determined adjustment current IA. An electrical signal corresponding to (n) is output as the current adjustment current signal Ia (n). Further, when neither increase determination nor decrease determination is set in the RAM 13, the output unit 223 makes the current adjustment current IA (n) the same as the previous adjustment current IA (n-1), and the current adjustment current IA (n-1). As the signal Ia (n), the same signal as the adjustment current signal Ia (n−1) output last time is output.

Next, correction amount determination processing performed by the correction amount determination unit 221 will be described using a flowchart.
FIG. 10 is a flowchart illustrating a procedure of correction amount determination processing performed by the correction amount determination unit 221. The correction amount determination unit 221 periodically executes this correction amount determination process, for example, every 10 ms.
First, the correction amount determination unit 221 reads the latest detection torque signal Tp (n) output from the torque detection unit 310 and stored in the RAM 13 (step (hereinafter simply referred to as “S”) 1001).
Next, the correction amount determination unit 221 determines the correction amount α based on the latest detected torque signal Tp (n) read in S1001 and the map stored in the ROM 12 (S1002).

Next, an increase / decrease degree determination process performed by the increase / decrease degree determination unit 222 will be described using a flowchart.
FIG. 11 is a flowchart illustrating a procedure of an increase / decrease degree determination process performed by the increase / decrease degree determination unit 222. The increase / decrease degree determination unit 222 executes the increase / decrease determination process periodically, for example, every 10 ms.
The increase / decrease degree determination unit 222 first reads the detected torque signal Tp (n) output from the torque detection unit 310 and stored in the RAM 13 (S1101). Thereafter, the current average value Tpave (n) is calculated (S1102) and the previous average value Tpave (n−1) is calculated (S1103), and the average value change ΔTpave is calculated (ΔTpave = Tpave (n) −Tpave (n) -1)) (S1104).

Thereafter, the increase / decrease degree determination unit 222 determines whether or not the average value change ΔTpave calculated in S1104 is larger than the first determination value (S1105). When the average value change ΔTpave is larger than the first determination value (Yes in S1105), the increase determination is set in the RAM 13 (S1106), and the decrease determination set in the RAM 13 is cleared (S1107).
On the other hand, when the average value change ΔTpave is not larger than the first determination value (No in S1105), it is determined whether or not the average value change ΔTpave calculated in S1104 is smaller than the second determination value (S1108). ). When the average value change ΔTpave is smaller than the second determination value (Yes in S1108), the decrease determination is set in the RAM 13 (S1109), and the increase determination set in the RAM 13 is cleared (S1110). On the other hand, if the average value change ΔTpave is not smaller than the second determination value (No in S1108), in other words, if the average value change ΔTpave is greater than or equal to the second determination value and less than or equal to the first determination value, the RAM 13 The increase determination set in (1) is cleared (S1111), and the decrease determination is cleared (S1112).

Next, output processing performed by the output unit 223 will be described using a flowchart.
FIG. 12 is a flowchart illustrating a procedure of output processing performed by the output unit 223. The output unit 223 executes this output process periodically, for example, every 10 ms.
First, the output unit 223 determines whether or not the increase determination is set in the RAM 13 (S1201). When the increase determination is set (Yes in S1201), the current value obtained by multiplying the correction amount α determined by the correction amount determination unit 221 by “−1” is the current adjustment current IA (n) (= − 1 × α) and an electrical signal corresponding to the determined adjustment current IA (n) is output as the current adjustment current signal Ia (n) (S1202).

  On the other hand, when the increase determination is not set (No in S1201), it is determined whether or not the decrease determination is set in the RAM 13 (S1203). When the decrease determination is set (Yes in S1203), the correction amount α determined by the correction amount determination unit 221 is determined as the current adjustment current IA (n) (= α) and the determined adjustment current IA An electrical signal corresponding to (n) is output as the current adjustment current signal Ia (n) (S1204).

  On the other hand, when the decrease determination is not set (No in S1203), the current adjustment current IA (n) is made the same as the previous adjustment current IA (n-1), and the current adjustment current signal Ia (n) is The same signal as the adjustment current signal Ia (n-1) output last time is output (S1205).

FIG. 13 is a diagram showing a relationship between the steering torque T and the target current IT calculated by the target current calculation unit 20 in the steering device 100 according to the present embodiment. The relationship between the steering torque T and the target current IT calculated by the target current calculator 20 is indicated by a solid line. In FIG. 13, the relationship between the steering torque T and the reference target current IB calculated by the reference target current calculation unit 21 is indicated by a broken line.
As described above, since hysteresis occurs in the output value from the torque sensor 109, the reference target current IB calculated by the reference target current calculation unit 21 with respect to the steering torque T is as shown by the broken line in FIG. The reference target current IB is different between the value of the reference target current IB when the wheel 101 is rotated to the right (in the direction of increase in the right direction) and the value of the reference target current IB during rotation of the wheel 101 (in the direction of return to the left).

  In the steering device 100 according to the present embodiment, as shown in FIG. 9, when the absolute value of the detected torque signal Tp output from the torque detector 310 is small, the correction amount α is set to a negative value. Is done. When the increase amount of the steering torque T is large, in other words, when the steering wheel 101 rotates to the right, a value obtained by adding a value obtained by multiplying the reference target current IB calculated by the reference target current calculation unit 21 to the correction amount α by −1 is obtained. The current is calculated as the target current IT by the target current calculation unit 20. Further, when the amount of decrease in the steering torque T is large, in other words, when the steering wheel 101 is rotated counterclockwise, a current having a value obtained by adding the correction amount α to the reference target current IB calculated by the reference target current calculation unit 21 is a target current calculation. The target current IT is calculated by the unit 20. Therefore, according to the target current calculation unit 20 according to the present embodiment, when the steering torque T is small, the reference target current is calculated when the steering wheel 101 rotates clockwise due to the hysteresis of the detected torque signal Tp. The difference between the reference target current IB calculated by the unit 21 and the reference target current IB calculated by the reference target current calculation unit 21 during counterclockwise rotation is reduced. In other words, when the steering torque T is small, the target current IT calculated by the target current calculation unit 20 according to the present embodiment does not include the target current adjustment unit 22 and the addition unit 23, but the reference target current calculation unit 21. Of the target current calculation unit 20 (hereinafter referred to as “target current calculation unit 20 according to another embodiment”) configured to output the reference target current IB calculated by the above as the target current IT calculated by the target current calculation unit 20 as it is. Compared to the case, the difference between the target current IT when the steering wheel 101 rotates to the right and the target current IT when the steering wheel 101 rotates to the left becomes smaller. As a result, according to the target current calculation unit 20 according to the present embodiment, when the steering torque T is small, the target current that is closer to the operation of the steering wheel 101 is set, so that the steering feeling is improved.

  On the other hand, as shown in FIG. 9, when the absolute value of the detected torque signal Tp output from the torque detector 310 is large, the correction amount α increases in the positive direction as the absolute value increases. Set to When the steering wheel 101 rotates to the right, a current having a value obtained by adding a value obtained by multiplying the reference target current IB calculated by the reference target current calculation unit 21 to the correction amount α by −1 is set to the target current IT by the target current calculation unit 20. When the steering wheel 101 is rotated counterclockwise, a current having a value obtained by adding the correction amount α to the reference target current IB calculated by the reference target current calculation unit 21 is calculated by the target current calculation unit 20 as the target current IT. . Therefore, according to the target current calculation unit 20 according to the present embodiment, when the steering torque T is large, the reference target current is calculated when the steering wheel 101 rotates clockwise due to the hysteresis of the detected torque signal Tp. The difference between the reference target current IB calculated by the unit 21 and the reference target current IB calculated by the reference target current calculation unit 21 during left rotation increases. In other words, when the steering torque T is large, the target current IT calculated by the target current calculation unit 20 according to the present embodiment is compared with the target current IT calculated by the target current calculation unit 20 according to another embodiment. The difference between the target current IT when the steering wheel 101 rotates to the right and the target current IT when it rotates to the left increases. That is, when the steering torque T is large, the target current calculation unit 20 according to the present embodiment is based on the reference target current IB calculated by the reference target current calculation unit 21 when the steering wheel 101 is in the increasing direction. Is smaller and the target current IT is calculated so as to be larger than the reference target current IB calculated by the reference target current calculation unit 21 when the steering wheel 101 is in the return direction. Thereby, for example, when the steering wheel 101 is turned back from the increase in the clockwise direction, the assist torque in the clockwise direction of the electric motor 110 in the steering device 100 according to the present embodiment is related to another mode. Since it becomes larger than the assist torque in the steering device 100 having the configuration including the target current calculation unit 20, the behavior of the vehicle can be stabilized.

  As described above, in the steering device 100 according to the present embodiment, the target current IT is adjusted in consideration of hysteresis in a wide region when the steering torque T is small and large, so that the steering feeling ( (Steering characteristics) can be improved, and steering feeling and safety can be improved. In addition, since only the output value from the torque sensor 109 is used as a parameter, both improvement in steering feeling and improvement in safety are realized with a simple configuration.

  Moreover, the target current IT with respect to the steering torque T can be arbitrarily changed by arbitrarily changing the relationship between the detected torque signal Tp and the correction amount α illustrated in FIG. Therefore, for each vehicle on which the steering device 100 according to the present embodiment is mounted, it is possible to easily set the hysteresis in consideration.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 21 ... Reference target current calculation part, 22 ... Target current adjustment part, 23 ... Addition part, 30 ... Control part, 100 ... Electric power steering apparatus, 101 ... Steering wheel (handle) 109, torque sensor, 110, electric motor, 221, correction amount determination unit, 222, increase / decrease degree determination unit, 223, output unit, 310, torque detection unit.

Claims (4)

Detection means for detecting a value corresponding to the steering torque of the steering wheel;
Target current calculation means for calculating a target current to be supplied to the electric motor based on the detection value detected by the detection means;
With
When the absolute value of the steering torque is large, the target current calculation unit uses a reference target current according to the detection value detected by the detection unit and an adjustment value according to the detection value detected by the detection unit. The absolute value of the target current is smaller than the reference target current when the steering wheel is in the increasing direction of the steering wheel, and larger than the reference target current when the steering wheel is in the return direction of the steering wheel. To calculate the target current ,
The target current calculating means uses the reference target current and the adjustment value, and when the absolute value of the steering torque is small and the absolute value of the target current is in the direction of increasing the steering wheel, An electric power steering apparatus characterized in that the target current is calculated so as to be smaller than the reference target current when the steering target is larger than the reference target current and in the steering wheel return direction . The adjustment value of the target current calculation means to claim 1, characterized in that the sign is reversed in the case large and if the absolute value of the detected value detected by the detection unit is smaller than a predetermined value The electric power steering apparatus as described. The target current calculation means includes reference target current calculation means for calculating the reference target current, target current adjustment means for setting the adjustment value, and addition means for adding the reference target current and the adjustment value. Prepared,
The target current adjusting means corrects and corrects a correction amount determined by the determining means according to a direction of operation of the steering wheel, a determining means for determining a correction amount based on a detection value detected by the detecting means. the electric power steering apparatus according to claim 1 or 2, characterized in that the correction amount and an output means for outputting, as the adjustment value. When the steering torque direction is one direction of rotation of the steering wheel is positive, and the other direction of rotation is negative,
The determination means of the target current calculation means determines the sign of the correction amount to be negative when the absolute value of the detection value detected by the detection means is smaller than a predetermined value, and positive when it is larger. When the steering torque is increasing, the output means uses the value obtained by multiplying the correction amount by −1 as the adjustment value, and when the steering torque is decreasing. The electric power steering apparatus according to claim 3 , wherein the correction amount is the adjustment value.

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