JP4442009B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle-mounted electric power steering device that assists a driver in steering.
[0002]
[Prior art]
As an electric power steering device for mounting on a vehicle for assisting the driver's steering, for example, Japanese Patent Laid-Open No. 10-236323: Control device for electric power steering device and Japanese Patent No. 2874275: DC motor Those described in “Rotational speed, acceleration detection device” and the like are generally known.
[0003]
In these conventional technologies, the steering assist torque (or steering assist current) with respect to the steering torque is designed to increase as the vehicle speed decreases, and increases linearly with respect to the steering torque near the origin. It is designed to do. That is, in these graphs of steering assist torque versus steering torque in the prior art, the steering assist torque increases according to a positive proportionality constant in the vicinity of the origin.
[0004]
However, when the steering torque is small, the driver often does not intend to steer (change the direction). In such a case, if the steering assist torque acts on the steering mechanism, the steering assist torque is unnecessary. In addition, the steering stability may deteriorate.
[0005]
As a slight countermeasure against such a problem, for example, as shown in FIG._AThe method etc. which control can be considered. FIG. 9 shows the assist torque T with respect to the conventional steering torque τ._AIt is a graph of.
Thus, by providing a relatively wide dead zone (−T0 ≦ τ ≦ T0), unnecessary steering assist torque as described above is eliminated, and a temporary effect can be seen in improving steering stability.
An example of calculating assist torque with such a dead zone can be found in, for example, Japanese Patent Application Laid-Open No. 07-132845: Electric Power Steering with Learning Function.
[0006]
[Problems to be solved by the invention]
However, even in these conventional techniques, it is still difficult to obtain sufficient stability near the neutral position of the steering angle, and particularly when the vehicle is traveling straight at high speed, the steering feeling near the neutral position of the steering angle is light. Under the present circumstances, the stability (stabilization) of the steering sensation, that is, the so-called “neutral feeling” is not sufficiently obtained or is difficult to obtain.
[0007]
For example, it is not impossible to improve such a neutral feeling by increasing the spring constant of the torsion bar provided in the steering mechanism. However, when such measures are taken, the following new problems Is derived.
(1) The measurement accuracy of a torque sensor that detects steering torque decreases.
(2) In order to increase the spring constant of the torsion bar without reducing the measurement accuracy of the torque sensor, it is necessary to improve the steering mechanism (hardware) centering on the torsion bar, which increases the manufacturing cost. Invite.
[0008]
The present invention has been made in order to solve the above-mentioned problems, and the purpose of the present invention is to compare the electric power steering apparatus that can appropriately obtain the so-called “neutral feeling” as described above in terms of manufacturing cost and the like. It is to be realized at a reasonable price.
[0009]
[Means for Solving the Problems]
  In order to solve the above problems, the following means are effective.
  That is, the first means is an assist torque T for assisting the driver's steering._AIn an electric power steering apparatus having a steering mechanism having a motor for imparting power and a control device for driving and controlling the motor, a steering torque for a steering wheelτAs an independent variable x (-a ≦ x ≦ a), satisfying “x> 0 => f (x) ≦ 0” and “f (−x) = − f (x)”, and approximately one sine of one cycle Neutral compensation torque T represented by a function f (x) having a wave shape, a substantially sawtooth shape, or a substantially inclined N shape._C Assist torque T that changes according to the value of steering torque τ _A The neutral feeling compensation torque T _C TheIncluding one of the terms or components that constitute the torque command value for the motor,Assist torque T _A Is described, approximated, or calculated by a polynomial composed of odd or higher order terms of the steering torque τ within a predetermined range of “−b ≦ x ≦ b, a <b”. Features.
[0012]
  Also,SecondMeans of the aboveFirstIn the means, the maximum value of the function f (x) is set to the vehicle speed V of the vehicle._nIt is to increase almost monotonously.
[0013]
  Also,ThirdMeans of the firstOr secondIn the means, the wavelength of one waveform of the function f (x) or the upper limit value a of the domain of the independent variable x is set as the vehicle speed V_nIt is to increase almost monotonously.
[0014]
  Also,4thThe above means are the first to the above.ThirdIn any one of the means, the neutral feeling compensation torque T_CIn the vicinity of the origin of “T_C= F (x) = 0 (−ε ≦ x ≦ ε ≦ a) ”.
[0015]
  Also,5thThe above means are the first to the above.4thIn any one of the means, the function f or the physical quantity used as the independent variable x of the function f is dynamically changed.
  The above-described problems can be solved by the above means.
[0016]
[Operation and effect of the invention]
In FIG. 1, the typical graph explaining the basic concept (action principle) of this invention is shown. In FIG. 1A, the independent variable x of the function f is a steering torque τ with respect to the steering wheel, a steering angle θ based on the neutral position of the steering wheel, or a related value (for example, ξ or Θ described later). These are physical quantities having a clockwise direction from the driver's seat toward the steering wheel as a positive direction.
[0017]
For example, when the steering angle θ based on the neutral position of the steering wheel is selected as the independent variable x,₀≦ θ ≦ a₀In the steering angle range near the origin, the torque T in the vertical axis direction_CCompensates for the spring constant of the torsion bar, so this torque T_CQuasi-generates (compensates) the torque that the torsion bar with a moderate spring constant exerts on the steering wheel as an effective result. However, the sign on the vertical axis is also the positive direction in the clockwise direction from the driver's seat toward the steering wheel.
[0018]
Further, in a steering mechanism having a torsion bar, when the rotational speed of the steering wheel is low, the steering angle θ and the steering torque τ based on the neutral position are proportional in the vicinity of the origin. Accordingly, even when the steering torque τ for the steering wheel is selected as the independent variable x, the torque T in the vertical axis direction is also selected._C(= F (x)) makes it possible to artificially generate (compensate), as an effective result, a torque that is approximately the same as the torque that an appropriate torsion bar exerts on the steering wheel.
[0019]
Therefore, using the function f (x) as shown in FIG._C) Acts on the steering mechanism, a moderate neutral feeling can be realized without modifying the steering mechanism such as adding a new torsion bar to the conventional steering mechanism.
[0020]
FIG. 1B shows that | x | ≧ a₀T in the region_CIt is a graph which shows the change of = f (x). These regions (| x | ≧ a₀) Change rate (| dT_C/ Dx |) is too large, | x | = a₀Since the total torque command value T for the motor changes abruptly in the vicinity of, there is a possibility that the steering feeling may become uncomfortable. The rate of change (| dT_C/ Dx |) is too small, the neutrality compensation torque T is reached even in a region where neutrality is not required._CMay be generated and the original ideal assist torque may not be realized.
Therefore, for example, in the example of FIG. 1B, the upper limit value a of the domain of the independent variable x (the intercept coordinate with the x axis when x> 0 of the function f (x)) is₁, A₂, A_ThreeEtc. are good.
[0021]
Further, these functions f (x) may be constituted by a sine wave or the like as shown in FIG. The shape of these functions f (x) can be constituted by a substantially sine wave shape or a substantially saw wave shape of one cycle, or a substantially inclined N shape.
[0022]
FIG. 2 shows an assist torque T with respect to the steering torque τ in a fragmentary manner illustrating the embodiment (second means) of the present invention._AIt is a graph of. In this graph, the steering torque τ is selected as the independent variable x in FIG. 1B, and a = a₂= T₀A new assist torque T according to the present invention is obtained by adding (adding) the function f (τ) to the conventional assist torque shown in FIG._AIs configured.
For example, in this way, the neutrality compensation torque T of the present invention_CBy adding (adding) (= f (x)) as one of the terms constituting the torque command value for the motor, the present invention can be specifically implemented.
[0023]
Further, a new assist torque T according to the present invention having a shape as shown in FIG._AIs described or approximated in a predetermined region of “−b ≦ τ ≦ b” by, for example, a polynomial composed of odd or higher order terms of the steering torque τ as shown in the following equation (1). can do.
[Expression 1]
T_A= F (τ) = c₁τ + c_Threeτ^Three+ C_Fiveτ^Five                  ... (1)
Further, from the function value of the derivative described in the following equation (2), the spring constant near the neutral position of the steering mechanism (τ≈0) is the coefficient c of the first-order term of the equation (1).₁It can be seen that it can be optimized by adjusting.
[Expression 2]
f ′ (0) = c₁(<0) ... (2)
[0024]
Usually, assist torque T_AAre often calculated by an interpolation process based on table data or the like, but the assist torque T is also calculated by an arithmetic process based on such description or approximation._ACan be calculated.
Therefore, assist torque T_AAs a calculation method, a convenient processing method may be selected from among these in consideration of data processing speed (calculation speed), system development ease, maintenance / expandability, memory usage, and the like.
[0025]
Further, the upper limit value a of the independent variable x and the maximum value of the function f (x) as described above are set as the speed V of the running vehicle._nIf it is increased substantially monotonically according to the speed, the neutral compensation torque T increases as the vehicle travels at high speed (straightly)._CAs a result, the driver is able to_nTherefore, a moderately stable neutral feeling can be obtained.
[0026]
Also, neutral compensation torque T_CIn the vicinity of the origin of (= f (x)), “T_C= 0 (−ε ≦ x ≦ ε ≦ a) ”, a neutral feeling compensation torque T corresponding to the measurement accuracy of the independent variable x is provided._CCan be generated. For example, when the steering angle θ is selected as the independent variable x, the neutral position θ of the steering angle₀It may take some time before is accurately determined. Neutral position θ₀This is the case when the vehicle is automatically learned from the running state.
[0027]
For example, in such a case, by providing the dead zone as described above, the neutral feeling compensation torque T in the direction opposite to the original desired direction is provided._CThe fear of acting will disappear.
In addition, by such a method, a small play area is formed in the vicinity of the neutral position, so that a neutral feeling with a slight margin can be realized.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
(First embodiment)
FIG. 3 is a hardware configuration diagram of the electric power steering apparatus 100 according to each embodiment of the present invention.
[0029]
A steering wheel (steering wheel) 11 is attached to one end of the steering shaft 10, and a pinion shaft 13 supported by a gear box 12 is coupled to the other end. The pinion shaft 13 is engaged with a rack shaft 14 fitted in the gear box 12, and both ends of the rack shaft 14 are connected to steering wheels (not shown) via ball joints or the like, although not shown. Yes. Further, a brushless DC motor M (hereinafter simply referred to as “motor M”) for applying assist torque is connected to the steering shaft 10 via two gears 17.
[0030]
The DC motor M is supplied with motor drive currents iu, iv, and iw for the three phases U, V, and W via the current detector 115 from the drive circuit 113 of the motor control device 110.
Further, the steering shaft 10 is provided with a torque detector 15 for detecting the magnitude and direction (steering torque τ) of the manual steering force applied from the driver to the steering wheel (handle) 11.
[0031]
The motor M has a built-in resolver R / D (rotation angle sensor) for detecting the rotation angle, and the CPU 111 outputs a phase signal n (6 bits) of the motor M output from the resolver R / D. Information; 0 ≦ n <63) is input, and the rotation angle θ of the motor M_M(Phase: 0 ≦ θ_M<2π) is calculated.
[0032]
The motor control device 110 includes a CPU 111, a ROM 112b, a RAM 112a, a drive circuit 113, an input interface (IF) 114, a current detector 115, and the like. The drive circuit 113 includes a battery (not shown), a PWM converter, a PMOS drive circuit, and the like, and supplies electric power to the motor M by changing the drive current to a sine wave by chopper control.
[0033]
The CPU 111 of the motor control device 110 includes a torque sensor 15 used for detecting the phase signal n and the steering torque τ of the steering wheel, a vehicle speed V_nAn output signal (measured value) from the speedometer 50 or the like used for calculating the vehicle speed is input via the input interface (IF) 114. The CPU 111 determines a torque value (command torque T) to be output from the motor M based on a predetermined torque calculation from these input values, and further, based on the command torque T, each current of the d-axis and the q-axis. Command value (id^*, Iq^*). However, in this embodiment, “id^*= 0 ”.
[0034]
FIG. 4 is a block diagram showing a logical configuration of the motor control device 110 for driving and controlling the motor M of the electric power steering device 100 according to the first embodiment. The torque current conversion unit 280 of FIG.^*Is based on the command torque T, and is mainly a iq^*-T map (table data) etc.
The steering torque calculation unit 330 includes a low-pass filter (first-order lag filter), a phase compensation unit, and the like (not shown).
[0035]
The command torque calculation unit 200 calculates the phase θ of the motor M calculated by the angle detection unit 310._MFurther, the steering torque τ of the steering wheel calculated by the steering torque calculator 330 and the vehicle speed V calculated by the vehicle speed calculator 320_nOr the steering wheel rotation angle θ calculated by the steering angle calculation unit 500_HBased on the above, a desired torque value (command torque T) to be output is calculated.
For example, the angle detector 310 calculates the rotation angle (phase) θ of the motor M according to the following equation (3) based on the output value n (6-bit signal) of the resolver R / D._MIs calculated.
[Equation 3]
θ_M= 2πn / 64 (3)
[0036]
The command torque calculation unit 200 mainly uses assist torque T_AAssist torque calculation unit 210 for calculating the inertia compensation torque T_KInertia compensation torque calculator 220 for calculating the torque and damper torque T_DDamper / torque calculator 230 for calculating the torque and steering wheel return torque T_RIt is comprised from the handle | steering-wheel return torque calculating part 240 grade | etc., Which calculates these. The command torque calculation unit 200 calculates the command torque T according to the following equation (4).
[Expression 4]
T = T_A+ T_K+ T_D+ T_R                                  (4)
[0037]
FIG. 5 shows the steering torque τ to the assist torque T in the first embodiment._AIt is a graph which calculates | requires. The assist torque calculation unit 210 performs an assist torque T based on this graph by interpolation processing or the like._AIs calculated.
The main features of this graph are as follows.
[0038]
(1) In a predetermined region of “−b ≦ τ ≦ b”, it can be approximated by the above equation (1).
(2) Point symmetry with respect to the origin O.
(3) Vehicle speed V_nIn the middle speed region and the high speed region, in the vicinity of the origin, a substantially sine wave shape of one cycle satisfying “τ> 0 → f (τ) ≦ 0” and “f (−τ) = − f (τ)”. Neutral compensation torque T expressed by function f (τ)_CIs added to the conventional assist torque having the shape shown in FIG. 9, and the assist torque T shown in FIG._AIs formed.
[0039]
(4) When τ> 0, vehicle speed V_nThe larger the value, the assist torque T_AIs small. However, the clockwise direction is positive, and here T_AThe absolute value of is not described.
(5) When τ <0, vehicle speed V_nThe larger the value, the assist torque T_AIs big. However, the clockwise direction is positive, and here T_AThe absolute value of is not described.
(6) The amplitude (maximum value) of the function f (τ) having the substantially sine wave shape is the vehicle speed V_nThe bigger is the bigger.
[0040]
(7) The wavelength of the function f (τ) having the substantially sinusoidal shape described above (the upper limit of the domain of the function f) is determined by the vehicle speed V_nThe bigger is the bigger.
(8) In the region of | τ | ≧ b, the assist torque T_AIndicates a constant value.
(9) The value of the minute interval (−ε ≦ x ≦ ε ≦ a) near the origin of the function f (τ), and hence the assist torque T_AThe value in the minute interval (−ε ≦ x ≦ ε ≦ a) near the origin of the value indicates a constant value 0. That is, in the vicinity of the origin, the assist torque T_AHas a dead zone, and the width ε of the dead zone is determined by the vehicle speed V_nThe larger is the smaller.
[0041]
FIG. 6 shows the steering torque τ with respect to the steering angle θ according to the first embodiment._nIt is a graph which shows the result measured by (approx. 100 km / h). However, in this graph, Grf1 is the conventional assist torque T shown in FIG._AAnd T0 is the upper limit value of the definition area of the dead zone in FIG. 9.
The steering angle α indicates a rotation angle from a neutral position (steering angle origin) that balances when a steering torque of T0 is applied to the steering wheel.
[0042]
Further, Grf2 in FIG. 6 represents the assist torque T in the first embodiment in FIG._A5 is a graph when steering assistance is performed.
As can be seen from FIG. 6, the apparent effective (effective) spring constant in the vicinity of the origin of the torsion bar in the first embodiment is larger than that in the prior art (Grf1). That is, the assist torque T of the first embodiment of FIG._AIt can be seen that a stable neutral feeling can be obtained near the neutral position (origin) if the motor torque is controlled based on the above.
[0043]
Further, if the neutral feeling is compensated by such a method, it is not necessary to modify the program and is used in the interpolation process as shown in FIG._AOnly by changing the table data of the graph for determining the desired neutrality compensation torque T (FIG. 9 → FIG. 5)._CCan be realized.
[0044]
(Second embodiment)
In the first embodiment described above, the neutrality was compensated by improving the data map used in the assist torque calculation unit 210 of FIG. 4 from the conventional one (FIG. 9 → FIG. 5). In the second embodiment, the assist torque calculation unit 210 of FIG. 4 is not changed from the conventional one (use of FIG. 9). Instead, the “neutral compensation torque calculation unit 250” is newly replaced with each torque of FIG. By adding in parallel to the arithmetic units 210 (using FIG. 9), 220, 230, and 240, compensation for neutrality is performed in substantially the same manner as described above.
[0045]
That is, in the second embodiment, the total command torque T is calculated by the above-described equation (not shown) by a new command torque calculation unit 201 (not shown) that is very similar to the command torque calculation unit 200 (FIG. 4) of the first embodiment. It calculates according to following Formula (5) instead of 4).
[Equation 5]
T = T_A+ T_K+ T_D+ T_R+ T_C                            ... (5)
[0046]
FIG. 7 is a block diagram showing a logical configuration of the neutrality compensation torque calculation unit 250 of the second embodiment. The neutrality compensation torque calculation unit 250 detects the vehicle speed V detected in real time._n, Steering torque τ, and steering wheel rotation angle θ_HBased on the neutral compensation torque T_CDetermines the value of.
[0047]
The neutral position learning unit 251 is a known or arbitrary method that uses a vehicle speed V_n, Steering torque τ, and steering wheel rotation angle θ_HBased on the steering angle θ (≡θ_H−θ₀) Neutral position θ₀Is estimated statistically.
The effective area limiting unit 252 is a neutral feeling compensation torque T centered on the steering angle θ = 0 (neutral position)._CThe effective range related to the steering angle θ is quantitatively defined by the gain G3.
However, the necessity of the function of the effective area limiting unit 252 depends on the structure (specifications) of the torque sensor 15 centering on the torsion bar. Therefore, the effective area limiting unit 252 has the structure of the torque sensor 15. Depending on (specification) etc., it is not necessary.
[0048]
The vehicle speed dependent gain G1 calculation unit 253 is configured to provide a neutral feeling compensation torque T._CThe magnitude (absolute value) is the vehicle speed V_nThe gain G1 is determined so as to increase monotonously.
The vehicle speed dependent gain G2 calculating unit 254 determines that the wavelength of the function f (the upper limit value of the domain of the independent variable ξ) is the vehicle speed V._nThe gain G2 is determined so as to increase monotonously. Here, μ is an appropriate positive constant, and may be, for example, about 1 to 1/2.
[0049]
As illustrated in FIG. 1C, the waveform forming unit 255 is configured to compensate for the neutral feeling compensation torque T._CSpecify the waveform. The function f is an abbreviation of one cycle that satisfies “x> 0 => f (x) ≦ 0” and “f (−x) = − f (x)” with the variable ξ (≡G2 · τ) as an independent variable. It has a sinusoidal shape.
The neutral compensation torque T is achieved by the above functions._CIs determined as in the following equation (6).
[Formula 6]
T_C= G3 · G1 · f (τ / (μ + G1)) (6)
[0050]
For example, by such a method, the neutrality compensation torque T_CIf the steering torque τ is small in the steering angle region other than the vicinity of the neutral position (θ≈0) by the action of the effective region limiting unit 252, the neutral feeling compensation torque T_CIs suppressed, and a natural and smooth steering feeling can be obtained.
[0051]
Further, by providing a “neutral compensation torque calculation unit 250” as described above independently of the conventional assist torque calculation unit 210, the assist torque T is formed in the form as shown in FIG._AThere is no need to rewrite the data map. Therefore, assist torque T_ASince the neutral feeling compensation can be performed without rewriting the data map, the independence of each of the torque calculation units 210, 220, 230, 240, and 250 can be ensured. Maintenance and expandability can be maintained.
[0052]
(Third embodiment)
FIG. 8 is a block diagram showing a logical configuration of the neutrality compensation torque calculator 260 of the third embodiment. The neutrality compensation torque calculation unit 260 detects the vehicle speed V detected in real time._n, Steering torque τ, steering wheel rotation angle θ_H, And motor rotation angle θ_MBased on the neutral compensation torque T_CIs used in place of the “neutral compensation torque calculator 250” of the second embodiment.
[0053]
The neutral position learning unit 261, the effective region limiting unit 262, the vehicle speed dependent gain G1 calculating unit 263, the vehicle speed dependent gain G2 calculating unit 264, and the waveform forming unit 265 of the third embodiment are respectively the same as those of the second embodiment. The neutral position learning unit 251, the effective region limiting unit 252, the vehicle speed dependent gain G1 calculating unit 253, the vehicle speed dependent gain G2 calculating unit 254, and the waveform forming unit 255 have substantially the same functions.
[0054]
Therefore, in the third embodiment, the neutral feeling compensation torque T_CIs determined as in the following equation (7).
[Expression 7]
T_C= G3 · G1 · F ((θ_H−θ₀) / (Μ + G1)) (7)
[0055]
However, the effective area limiting unit 262 described above is based on the steering speed ω estimated by the steering speed estimation unit 266 and the neutral feeling compensation torque T centered on the steering speed ω = 0._CThe effective range related to the steering speed ω is quantitatively defined by the gain G3.
However, here, the steering speed estimation unit 266 determines the rotation angle θ of the motor M._MThe steering speed ω is estimated based on the rate of change of the steering torque τ with respect to time.
As a result of the action of the effective region limiting unit 262 as described above, the necessary amount of neutrality compensation torque T only in the steering speed region where neutral feeling is required, that is, in the low speed steering region where ω≈0._CIs output.
[0056]
In the first embodiment, the neutral feeling compensation torque T_CSince the steering angle θ is not used for the generation of the second embodiment, this method uses the neutral feeling compensation torque calculation section 250 (FIG. 7) of the second embodiment or the neutral feeling compensation torque calculation section 260 of the third embodiment. It is superior to the method using (FIG. 8) in the following points.
That is, in the method of using the neutral position learning units 251 and 261, the neutral position θ₀Since it takes time to accurately obtain the neutral sense compensation torque T_CCannot be generated accurately.
[0057]
However, neutral compensation torque T_COriginally, vehicle speed V_nIs particularly required in a high-speed region where a large value is large. Therefore, the neutral feeling compensation torque calculating section 250 (FIG. 7) of the second embodiment or the neutral feeling compensation torque calculating section 260 (FIG. 8) of the third embodiment. ) To neutralize compensation torque T_CThe above method of producing is also sufficiently useful.
Moreover, since these methods can be designed independently of the conventional assist torque calculation unit (210) as described above, they may be advantageous in terms of maintenance and development.
[0058]
In addition, as the methods of the first to third embodiments, a suitable or best method may be selected based on the measurement accuracy of various physical quantity detection sensors such as a steering angle sensor and a torque sensor.
For example, in each of the above-described embodiments, high detection accuracy is required for the steering angle θ in the order of the third embodiment, the second embodiment, and the first embodiment. Only in the steering angle region (near θ≈0) and the desired steering speed region (near ω≈0), the desired amount of neutrality compensation torque T_CTherefore, it is desirable to adopt the third embodiment when high detection accuracy is obtained with respect to the steering angle θ.
[0059]
Alternatively, as described above, the neutral position θ₀For example, the above embodiments may be dynamically switched and executed in the order of the first embodiment, the second embodiment, and the third embodiment.
The selection of these implementation methods may be determined according to the actual specific and detailed specifications of the hardware configuration centering on various sensors shown in FIG.
[0060]
In each of the above embodiments, the handle rotation angle θ_HIs obtained by the steering angle calculation unit 500 of FIG._HMay be detected directly by a known or arbitrary steering sensor (steering angle sensor). Such a hardware configuration is particularly effective when high detection accuracy is required for the steering angle θ described above.
[Brief description of the drawings]
FIG. 1 is a schematic graph illustrating a basic concept (operation principle) of the present invention.
FIG. 2 illustrates an assist torque T with respect to a steering torque τ illustrating a fragmentary embodiment (second means) of the present invention._AChart.
FIG. 3 is a hardware configuration diagram of an electric power steering apparatus 100 according to each embodiment of the present invention.
FIG. 4 is a block diagram showing a logical configuration of a motor control device 110 that drives and controls the motor M of the electric power steering device 100 according to the first embodiment of the present invention.
FIG. 5 shows an assist torque T with respect to a steering torque τ according to the first embodiment of the present invention._AGive a graph.
FIG. 6 is a graph showing a result of measuring a steering torque τ with respect to a steering angle θ according to the first embodiment of the present invention.
FIG. 7 is a block diagram showing a logical configuration of a neutrality compensation torque calculator 250 according to the second embodiment of the present invention.
FIG. 8 is a block diagram showing a logical configuration of a neutral feeling compensation torque calculator 260 according to the third embodiment of the present invention.
FIG. 9 shows assist torque T with respect to steering torque τ in the prior art._AChart.
[Explanation of symbols]
M: Motor
R / D: Resolver (rotational angle sensor of motor M)
n ... Resolver output signal
θ_M... Motor rotation angle (phase: 0 ≦ θ_M<2π)
θ_H… Handle rotation angle
θ_O… Handle neutral position
θ… steering angle (θ_H−θ_O)
V_n… Vehicle speed
τ… Steering torque
ω… Steering speed
T: Command torque
T_A... assist torque
T_C... Neutral compensation torque
10 ... Steering shaft
11 ... Steering wheel (handle)
100 ... Electric power steering device
110 ... Motor control device
111 ... CPU
200 ... Command torque calculation unit
210 ... Assist torque calculation unit
250 ... Neutral feeling compensation torque calculation section (second embodiment)
260 ... Neutral compensation torque calculation unit (third embodiment)
251,
261 ... Neutral position learning unit
252
262 ... Effective area restriction part
253
263 ... Vehicle speed dependent gain G1 calculation unit
254
264 ... Vehicle speed dependent gain G2 calculation unit
255
265 ... Waveform forming section
f, F ... Function to generate neutral feeling compensation torque
x: Independent variable of the function that generates neutrality compensation torque (general form)
a ... Upper limit of independent variable x

Claims (5)

The electric power steering apparatus having a steering mechanism having a motor that applies assist torque T _A for assisting the steering of the driver, and a control unit for driving and controlling said motor,
With the steering torque τ for the steering wheel as an independent variable x (−a ≦ x ≦ a),
“X> 0 => f (x) ≦ 0” and “f (−x) = − f (x)” are satisfied,
and,
The neutral feeling compensation torque T _C represented by a function f (x) having a one-cycle substantially sine wave shape, a substantially sawtooth wave shape, or a substantially inclined N shape is changed according to the value of the steering torque τ. By including the assist torque T _A as one of the terms or components, the neutral feeling compensation torque T _C is included as one of the terms or components constituting the torque command value for the motor,
The assist torque T _A is described, approximated by a polynomial composed of odd-order or higher-order terms of the steering torque τ within a predetermined range of “−b ≦ x ≦ b, a <b”. Alternatively , an electric power steering apparatus characterized by being calculated . 2. The electric power steering apparatus according to claim 1 , wherein the maximum value of the function f (x) increases substantially monotonously with respect to a vehicle speed V _n of the vehicle. The wavelength of the waveform of one cycle of the function f (x) or the upper limit value a of the domain of the independent variable x increases substantially monotonously with the vehicle speed V _n of the vehicle. The electric power steering apparatus according to claim 1 or 2 . The neutral sense compensation torque T _C is at the origin near the _{"T C = f (x) =} 0 (-ε ≦ x ≦ ε ≦ a) " made claims 1 to 3 characterized by having a dead zone The electric power steering device according to any one of the above. The function f, or electric power steering device according to any one of claims 1 to 4, characterized in that dynamically changes the physical quantity to be used as the independent variable x of the function f.

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