JP5699972B2 - Twin resolver type torque sensor and electric power assist device - Google Patents

Description

  The present invention relates to a twin resolver type torque sensor and an electric power assist device, and in particular, a twin resolver type torque sensor that detects torque transmitted from an input shaft to an output shaft via a torsion bar using two resolvers, and The present invention relates to an electric power assist device that calculates a target motor current to be passed through an assist motor based on detected torque.

  2. Description of the Related Art Conventionally, a twin resolver type torque sensor that detects torque transmitted from an input shaft to an output shaft through a torsion bar using two resolvers is known (see, for example, Patent Documents 1 and 2). In this twin resolver type torque sensor, each of the two resolvers outputs a sine wave signal whose amplitude changes in a sine wave shape and a cosine wave signal whose amplitude changes in a cosine wave shape according to the rotation of the shaft. Then, in each of the resolvers, the rotation angle is detected based on the sine wave signal and the cosine wave signal, and the torque is detected based on the difference between both rotation angles.

  In the torque sensor described in Patent Document 1, when a signal failure occurs in which any one of the output signals of the two resolvers becomes abnormal, it is normal among the output signals of the resolver in which the signal failure has occurred. Based on the amplitude of the output signal, the amplitude of the output signal when the abnormal output signal is normal is estimated. Based on the estimated amplitude and the amplitude of the normal output signal, a signal failure is detected. The rotation angle on the side where the generated resolver is provided is calculated. Then, the torque is detected based on the difference between the rotation angle on the side where the resolver where the signal failure has occurred and the rotation angle on the side where the resolver where no signal failure has occurred.

  Further, in the torque sensor described in Patent Document 2, when a signal failure occurs in which any one of the output signals of the two resolvers becomes abnormal, the rotation angle on the resolver side where the signal failure has occurred. However, it is detected based on the value of the normal output signal of the resolver, the rotation angle immediately before the occurrence of the abnormality, and the rotation angle on the resolver side where no signal failure has occurred, and the torque is detected.

  Therefore, according to the torque sensors disclosed in Patent Documents 1 and 2, even if an abnormality occurs in any one of the output signals of the two resolvers, it is possible to detect torque with a certain degree of accuracy. As a result, it is possible to continue the motor assist according to the torque.

JP 2010-286310 A JP 2003-337006 A

  By the way, when a signal failure occurs in which any one of the two resolver output signals becomes abnormal, the output signal of the resolver in which the signal failure has occurred is detected as a signal failure. It is conceivable to substitute with an output signal of a resolver in which no occurrence occurs. However, for example, if an abnormality occurs in the cosine wave signal of one resolver and the above substitution is performed on the cosine wave signal of the other resolver, the rotation detected by both resolvers is near the electrical angles of 90 ° and 270 °. There is a disadvantage that the difference in angle becomes zero and the detected torque becomes zero. In addition, when an abnormality occurs in the sine wave signal of one resolver and the above substitution is performed on the sine wave signal of the other resolver, the same situation occurs in the vicinity of the electrical angles of 0 ° and 180 °. For this reason, it is difficult to accurately obtain the torque to some extent over the entire electrical angle range of 0 ° to 360 ° simply by performing the above-described substitution.

  The present invention has been made in view of the above points, and even when an abnormality occurs in any one of the output signals of a pair of resolvers, the torque is applied to some extent over the entire electrical angle range of 0 ° to 360 °. Provided are a twin resolver type torque sensor capable of accurately detecting, and an electric power assist device capable of obtaining a target motor current based on the detected torque with a certain degree of accuracy over the entire electric angle range of 0 ° to 360 °. For the purpose.

  The object is to provide a first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and a torsion bar connected to the input shaft via a torsion bar. A second resolver that outputs the sine wave signal and the cosine wave signal in accordance with the rotation of the connected output shaft; the rotation angle of the input shaft based on the output signal of the first resolver; and the output signal of the second resolver A torque detector for detecting torque transmitted from the input shaft to the output shaft via the torsion bar based on a difference between the rotation angle of the output shaft and the twin resolver torque sensor. When an abnormality is detected in any one of the output signals of the first resolver and the second resolver, the output value of the one output signal is changed to the output value of the other output signal. An alternative means for substituting, the torque detecting means, a gain correcting means for correcting the gain of the estimated torque detected by using the output value of the one output signal obtained by the alternative means, and a predetermined electrical angle Replacement means for replacing the estimated torque with a predetermined value in the vicinity; post-interpolation torque detection means for detecting the estimated torque obtained by the gain correction means and the replacement means as the torque when the abnormality is detected; This is achieved by a twin resolver type torque sensor having

  Further, the above object is to provide a first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and a torsion bar on the input shaft. A second resolver that outputs the sine wave signal and the cosine wave signal according to the rotation of the output shaft connected via the first resolver, the rotation angle of the input shaft based on the output signal of the first resolver, and the second resolver Torque detection means for detecting torque transmitted from the input shaft to the output shaft via the torsion bar based on a difference from a rotation angle of the output shaft based on an output signal, and detected by the torque detection means An electric power assist device comprising: target motor current calculation means for calculating a target motor current to be passed to the assist motor provided on the output shaft side based on the torque. When an abnormality is detected in any one of the output signals of the first resolver and the second resolver, the output value of the one output signal is replaced with the output value of another output signal. The target motor current calculation means gains the calculated motor current calculated based on the torque detected using the output value of the one output signal obtained by the substitution by the substitution means. Gain correcting means for correcting, replacing means for replacing the calculated motor current with a predetermined value in the vicinity of a predetermined electrical angle, and the calculated motor current obtained by the gain correcting means and the replacing means when the abnormality is detected This is achieved by an electric power assist device having post-interpolation target motor current calculation means for calculating as a target motor current.

  Further, the above object is to provide a first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and a torsion bar on the input shaft. A second resolver that outputs the sine wave signal and the cosine wave signal according to the rotation of the output shaft connected via the first resolver, the rotation angle of the input shaft based on the output signal of the first resolver, and the second resolver Torque detection means for detecting torque transmitted from the input shaft to the output shaft via the torsion bar based on a difference from a rotation angle of the output shaft based on an output signal, and detected by the torque detection means Target rotational angular velocity calculating means for calculating a target rotational angular velocity based on the torque, and an assist motor provided on the output shaft side so that the rotational angular velocity matches the target rotational angular velocity. A target motor current calculating means for calculating a target motor current to be passed through the first power resolver, wherein there is an abnormality in any one of the output signals of the first resolver and the second resolver. An alternative means for substituting the output value of the one output signal with the output value of another output signal when detected, wherein the torque detection means is the one output signal obtained by substituting with the alternative means Gain correction means for correcting the estimated torque detected by using the output value, replacement means for replacing the estimated torque with a predetermined value in the vicinity of a predetermined electrical angle, and the gain correction when the abnormality is detected. And a post-interpolation torque detecting means for detecting the torque obtained by the replacing means as the torque, and the target rotational angular velocity calculating means includes the torque detecting means. Achieved by an electric power assist device that increments the target rotational angular velocity when the torque detected by the means is greater than or equal to a threshold, and decrements the target rotational angular velocity when the torque is less than the threshold. .

  According to the present invention, even if an abnormality occurs in any one of the output signals of a pair of resolvers, the torque can be detected with a certain degree of accuracy over the entire electrical angle range of 0 ° to 360 °, or the detected torque Can be obtained with a certain degree of accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of an electric power assist apparatus provided with the twin resolver type torque sensor which is 1st Example of this invention. It is a figure for demonstrating the torque detection principle by the twin resolver type torque sensor of a present Example. It is an internal block diagram of the arithmetic unit which the electric power assist apparatus of a present Example has. It is a figure showing the time waveform of an example of the steering torque detected when a resolver is normal in a present Example. It is a figure showing the flow of the process implement | achieved when abnormality generate | occur | produces in any one output signal among all the output signals of a resolver in a present Example. It is a figure for demonstrating the interpolation process performed when one output signal is abnormal among all the output signals of a resolver in a present Example. It is a figure for demonstrating the effect of the interpolation process in a present Example. It is a figure showing the flow of the process implement | achieved when abnormality generate | occur | produces in any one output signal among all the output signals of a resolver in 2nd Example of this invention. It is a figure for demonstrating the interpolation process performed when one output signal is abnormal among all the output signals of a resolver in a present Example. It is a figure for demonstrating the effect of the interpolation process in a present Example. It is a figure showing the flow of the processing implement | achieved when abnormality generate | occur | produces in any one output signal among all the output signals of a resolver in 3rd Example of this invention. It is a figure for demonstrating the interpolation process performed when one output signal is abnormal among all the output signals of a resolver in a present Example. It is a figure for demonstrating the effect of the interpolation process in a present Example.

  Hereinafter, specific embodiments of a twin resolver torque sensor and an electric power assist device according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of an electric power assist device 12 including a twin resolver torque sensor 10 according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the principle of torque detection by the twin resolver torque sensor 10 of this embodiment. FIG. 3 shows an internal block diagram of the arithmetic unit included in the electric power assist device 12 of this embodiment.

  The electric power assist device 12 of this embodiment is mounted on a steering system for vehicle steering. This steering system includes a steering shaft 16 connected to a steering wheel 14 operated by a vehicle driver, a pinion 18 provided on the steering shaft 16, a rack 20 engaged with the pinion 18, and balls on both ends of the rack 20. And a wheel connected via a joint, a tie rod, and a knuckle arm.

  In the above configuration, when the steering wheel 14 is operated by the vehicle driver, the pinion 18 rotates accordingly, and the rack 20 is displaced in the longitudinal direction along the vehicle width direction. When the rack 20 is displaced along the vehicle width direction, the tie rod and the knuckle arm operate, and the wheels are steered. That is, the steering system has a function of turning the wheel by a steering operation by the driver by converting the rotational movement of the pinion 18 into the straight movement in the longitudinal direction of the rack 20.

  The electric power assist device 12 uses an electric motor to assist the torque required when the vehicle driver operates the steering wheel 14 to steer the wheel in order to reduce the burden of the steering operation by the vehicle driver. Power steering system. The steering shaft 16 includes an input shaft 22 fixed to the steering wheel 14 side, an output shaft 24 connected to the rack 20 side, and a torsion bar 26 interposed between the input shaft 22 and the output shaft 24. ing. The torsion bar 26 is twisted according to the steering torque applied to the steering wheel 14. The torsion angle of the torsion bar 26 is limited to a predetermined range by a mechanical stopper.

  The electric power assist device 12 includes a twin resolver torque sensor (hereinafter simply referred to as a torque sensor) 10 for detecting a steering torque applied to the steering wheel 14. The torque sensor 10 outputs a signal corresponding to the angle difference Δθ (= θ1−θ2) between the rotation angle θ1 of the input shaft 22 and the rotation angle θ2 of the output shaft 24, that is, the torsion angle Δθ of the torsion bar 26. The torsion angle Δθ of the torsion bar 26 corresponds to the steering torque applied to the steering wheel 14 when the driver operates the steering wheel 14. Therefore, the torque sensor 10 outputs a signal corresponding to the steering torque applied to the steering wheel 14 by the steering operation by the driver.

  The electric power assist device 12 also includes a calculation device 30 that performs various calculations such as steering torque detection calculation and target motor current calculation calculation. The torque sensor 10 described above is connected to the arithmetic device 30. The output signal of the torque sensor 10 is supplied to the arithmetic device 30. The arithmetic device 30 is an electronic control unit mainly composed of a microcomputer. The arithmetic unit 30 detects the torsion angle Δθ of the torsion bar based on the output signal of the torque sensor 10, and multiplies the magnitude of the torsion angle Δθ by the spring constant of the torsion bar to apply the steering torque T applied to the steering wheel 14. Is detected.

  The electric power assist device 12 also includes an electric motor 32. The electric motor 32 is, for example, a three-phase AC motor. The electric motor 32 includes a stator that is fixed to a housing on the vehicle body side that covers the rack 20, and a rotor that is engaged with the rack 20 and rotatably supported by the housing via a bearing. In the electric motor 32, when the rotor is rotated by excitation of the stator, the rack 20 is displaced in the longitudinal direction along the vehicle width direction. That is, in the electric power assist device 12, the electric motor 32 generates a torque that displaces the rack 20 along the vehicle width direction by its rotational drive (that is, an assist torque that assists the steering torque by the driver).

  An arithmetic device 30 is connected to each phase of the electric motor 32. The calculation device 30 calculates an assist torque to be applied to the rack 20 based on the steering torque T detected by the torque sensor 10. Specifically, an assist torque proportional to the steering torque T is calculated. The calculated assist torque may be in accordance with the vehicle speed, and specifically, the assist torque may be reduced as the vehicle speed increases. When calculating the assist torque, the arithmetic device 30 calculates a target motor current necessary for driving the electric motor 32 so that the assist torque is applied to the rack 20. Then, power is supplied from the power supply 34 to the electric motor 32 so that the target motor current flows through the electric motor 32.

  In order to simplify the control method of the electric motor 32, the arithmetic unit 30 performs dq conversion in which a three-phase AC current or voltage is expressed by two axes. In the current control that flows through the stator coil of the electric motor 32, a current value represented by a dq coordinate system that rotates with the rotor is used. In this dq coordinate system, the d axis is the direction in which the magnetic flux flows by the magnet attached to the motor rotor, and the q axis is the direction orthogonal to the d axis. Of the current flowing through the stator coil, the d-axis current representing the d-axis component is a component that generates magnetic flux, and the q-axis current representing the q-axis component is a component that generates rotational torque. The arithmetic unit 30 commands the voltage application to the electric motor 32 so that the target motor current flows in each phase of the electric motor 32.

  In the above configuration, when the steering wheel 14 is operated by a vehicle occupant, the electric motor 32 is driven so that an assist torque corresponding to the steering torque T is applied to the rack 20. Specifically, the drive of the electric motor 32 is performed such that a larger assist torque is generated as the steering torque T is larger. The assist torque may be a value corresponding to the vehicle speed of the vehicle. Specifically, the assist torque may be set to decrease as the vehicle speed increases. Therefore, according to the electric power assist device 12 of the present embodiment, it is possible to reduce the burden of the steering operation by the vehicle occupant using the electric motor 32.

In the present embodiment, the torque sensor 10 includes a resolver 40 for detecting a steering torque applied to the steering wheel 14. Specifically, the torque sensor 10 includes a first resolver 42 which outputs a signal corresponding to the rotation angle θ1 of the input shaft 22, the second resolver 44 which outputs a signal corresponding to the rotation angle θ2 of the output shaft 24 have. That is, the resolver 40 includes a first resolver 42 and a second resolver 44.

  The first resolver 42 outputs a signal of m cycles (for example, 5 cycles) in the process in which the input shaft 22 makes one mechanical rotation with respect to the vehicle body side, that is, a signal having the same level every mechanical angle 360 ° / m. It is configured to output. In this regard, the output signal of the first resolver 42 is a signal whose axial multiplication angle is mx. Further, the second resolver 44 is a signal of n cycles (for example, 6 cycles) in the process in which the output shaft 24 makes one mechanical rotation with respect to the vehicle body side, that is, at the same level for every mechanical angle 360 ° / n. It is configured to output a signal. In this regard, the output signal of the second resolver 44 is a signal with an axial multiplication angle of nx. The values m and n are preferably different from each other.

  As shown in FIG. 2, each resolver 42, 44 has an excitation coil 46 to which an excitation signal with a constant frequency is applied, and a sin coil 48 and a cos coil 50 that generate signals by applying the excitation signal to the excitation coil 46. It has. The sin coil 48 and the cos coil 50 extend in directions orthogonal to each other. Each of the sin coil 48 and the cos coil 50 has a sine wave shape corresponding to the target rotation angle position θ (that is, θ1 or θ2) when an excitation signal (= A · sinωt) having a constant frequency is supplied to the excitation coil 46. Current and voltage. Specifically, the sin coil 48 outputs a sine wave signal (sin phase output; = a · sin ωt · sin θ) whose amplitude changes in a sine wave shape according to the target rotation angle position θ, and the cos coil 50. Outputs a cosine wave signal (cos phase output; = a · sin ωt · cos θ) whose amplitude changes in a cosine wave shape in accordance with the target rotation angle position θ. At this time, the sin coil 48 and the cos coil 50 output electrical signals whose phases are shifted by an electrical angle of 90 ° with a mechanical angle of 360 ° / m or 360 ° / n as one cycle.

  The arithmetic device 30 includes an input side rotation angle detection unit 52 and an output side rotation angle detection unit 54. The input side rotation angle detection unit 52 is connected to the sin coil 48 and the cos coil 50 of the first resolver 42, and the sine wave signal sin θ <b> 1 supplied from the sin coil 48 and the cosine wave signal supplied from the cos coil 50. Based on cos θ1, the rotation angle θ1 of the input shaft 22 is detected. The output-side rotation angle detection unit 54 is connected to the sin coil 48 and the cos coil 50 of the second resolver 44, and the sine wave signal sin θ <b> 2 supplied from the sin coil 48 and the cosine supplied from the cos coil 50. Based on the wave signal cos θ2, the rotation angle θ2 of the output shaft 24 is detected.

  The arithmetic device 30 also has a torque detection unit 56 and a target motor current calculation unit 58. The torque detection unit 56 is connected to the output of the input side rotation angle detection unit 52 and the output of the output side rotation angle detection unit 54, and the rotation angle θ <b> 1 of the input shaft 22 detected by the input side rotation angle detection unit 52. The angle difference (rotation angle difference) with the rotation angle θ2 of the output shaft 24 detected by the output side rotation angle detection unit 54 is calculated, and the angle difference is detected as the twist angle Δθ of the torsion bar 26. Then, the steering torque T applied to the steering wheel 14 is detected by multiplying the magnitude of the twist angle Δθ by the spring constant of the torsion bar. The target motor current calculation unit 58 is connected to the output of the torque detection unit 56 and drives the electric motor 32 so that an appropriate assist torque is applied to the rack 20 based on the detected steering torque T. The target motor current (specifically, the q-axis current) necessary for the calculation is calculated.

  FIG. 4 shows a time waveform of an example of the steering torque detected when the resolver 40 is normal in this embodiment. FIG. 5 shows a flow of processing realized when an abnormality occurs in any one of the output signals of the first and second resolvers 42 and 44 of the resolver 40 in this embodiment. The figure is shown. FIG. 5 shows a state where an abnormality has occurred in the cosine wave signal cos θ1 of the first resolver 42.

  In the present embodiment, the arithmetic unit 30 determines whether the sine wave signals (sin phase output) sin θ1, sin θ2 and the cosine wave signals (cos phase output) cos θ1, cos θ2 of the first and second resolvers 42, 44 of the resolver 40 are abnormal. judge. For example, when the output of each phase of the resolvers 42 and 44 is not within a predetermined range near “0” and exceeds a predetermined threshold, it is determined that the resolvers 42 and 44 are in a normal state, while the output thereof Is within a predetermined range near “0” and below a predetermined threshold value, it is determined that a disconnection abnormality has occurred in one of the output signals of the resolvers 42 and 44.

  Here, if an abnormality in the output of the resolvers 42 and 44 is detected using the above method, if the target rotation angles θ1 and θ2 are not detected and estimated, the electric motor 32 is caused by the abnormality. It becomes impossible to generate the assist torque used. Therefore, the system of the present embodiment generates assist torque using the electric motor 32 even if a disconnection abnormality occurs in any one of the sine wave signals and cosine wave signals of the resolvers 42 and 44. In order to continue the control, the rotation angle of the target by the resolvers 42 and 44 in which the abnormality has occurred is detected with high accuracy. Hereafter, the characteristic part of the system of a present Example is demonstrated.

  In this embodiment, when the arithmetic unit 30 determines that an abnormality has occurred in any one of the output signals of the resolvers 42 and 44, the output in which the abnormality has occurred in accordance with a predetermined rule. A process of substituting the output value of the signal with the output value of another output signal is performed. Specifically, when an abnormality occurs in the output signals sin θ1 and cos θ1 of the first resolver 42 on the input shaft 22 side, the output signals sin θ2 and cos θ2 of the second resolver 44 on the output shaft 24 side are substituted, while the output shaft When abnormality occurs in the output signals sin θ2 and cos θ2 of the second resolver 44 on the 24 side, the output signals sin θ1 and cos θ1 of the first resolver 42 on the input shaft 22 side are substituted. For example, when an abnormality occurs in the cosine wave signal cos θ1 of the first resolver 42, as shown in FIG. Substitute with value.

  When an abnormality occurs in the output signals sin θ1 and cos θ1 of the first resolver 42, the input side rotation angle detection unit 52 of the arithmetic unit 30 estimates the rotation angle θ1 ′ as the rotation angle θ1 of the input shaft 22 using the alternative value. . For example, as shown in FIG. 5, when an abnormality occurs in the cosine wave signal cos θ1 of the first resolver 42, the sine wave signal sin θ1 of the first resolver 42 and the cosine wave signal cos θ2 of the second resolver 44 that is an alternative value. Based on the above, the rotation angle θ1 ′ of the input shaft 22 is estimated. In this case, the torque detection unit 56 uses the reference detection unit 56a to estimate the rotation angle θ1 ′ of the input shaft 22 and the rotation angle θ2 of the output shaft 24 detected based on the output signal of the second resolver 44. Is estimated as the torsion angle Δθ ′ of the torsion bar 26, and the steering torque T ′ is estimated.

  Further, when an abnormality occurs in the output signals sin θ2 and cos θ2 of the second resolver 44, the output side rotation angle detection unit 54 of the arithmetic unit 30 uses the alternative value to set the rotation angle θ2 ′ as the rotation angle θ2 of the output shaft 24. presume. For example, when an abnormality occurs in the sine wave signal sin θ2 of the second resolver 44, the output shaft is based on the cosine wave signal cos θ2 of the second resolver 44 and the sine wave signal sin θ1 of the first resolver 42 that is an alternative value. The rotation angle θ2 ′ of 24 is estimated. In this case, the torque detection unit 56 detects the rotation angle θ1 of the input shaft 22 detected based on the output signal of the first resolver 42 by the reference detection unit 56a, the estimated rotation angle θ2 ′ of the output shaft 24, and Is estimated as the torsion angle Δθ ′ of the torsion bar 26, and the steering torque T ′ is estimated.

  When there is no abnormality in any of the output signals of the resolvers 42 and 44, the steering torque T detected by the torque detector 56 does not drop over the entire electrical angle range of 0 ° to 360 °. (FIG. 4). On the other hand, when any one of the output signals of the resolvers 42 and 44 is abnormal, the estimated steering torque T ′ estimated by the torque detector 56 is in the electrical angle range of 0 ° to 360 °. In FIG. 5, a drop occurs.

  Specifically, when the sinusoidal signal sin θ1 or sin θ2 is replaced with the occurrence of an abnormality, the estimated steering torque T ′ drops near the electrical angles of 0 ° and 180 °, and the electrical angles 0 ° and 180 °. Thus, the estimated steering torque T ′ becomes zero. Further, when the cosine wave signal cos θ1 or cos θ2 is replaced due to the occurrence of an abnormality, the estimated steering torque T ′ drops near the electrical angles of 90 ° and 270 °, and the estimated steering is performed at the electrical angles of 90 ° and 270 °. Torque T ′ becomes zero. The waveform of the drop in the estimated steering torque T ′ is sinusoidal with respect to the electrical angle because the output signal in which the abnormality has occurred is replaced with the same sine wave signal or cosine wave signal among the normal output signals. It is formed.

  On the other hand, when the arithmetic unit 30 determines that an abnormality has occurred in any one of the output signals of the resolvers 42 and 44, the output signal in which the abnormality has occurred is a sine wave signal (sin phase). Output) or cosine wave signal (cos phase output) and output shaft 24 or input shaft based on the output signals of resolvers 44 and 42 in which both the sine wave signal and cosine wave signal are normal. In detecting the rotation angle θ2 or θ1 of 22, the electrical angle in the normal resolver 44, 42 is detected.

  When the output signal in which the abnormality has occurred is a sine wave signal of the resolver 42 or 44, the arithmetic unit 30 determines whether the detected electrical angle is in the vicinity of the electrical angle of 0 ° or in the vicinity of the electrical angle of 180 °. On the other hand, if the output signal in which the abnormality has occurred is a cosine wave signal of the resolver 42 or 44, the detected electrical angle is within the 90 ° electrical angle vicinity range or the 270 ° electrical angle vicinity range. It is discriminated whether or not there is. This “neighborhood” indicates a predetermined vertical range with respect to the reference value, and is set to ± 10 °, for example.

  FIG. 6 is a diagram for explaining an interpolation process performed when one of the output signals of the resolvers 42 and 44 is abnormal in this embodiment. FIG. 7 is a diagram for explaining the effect of the interpolation processing in this embodiment.

  When the arithmetic unit 30 determines that any one of the output signals of the resolvers 42 and 44 is abnormal, as described above, the reference detection unit 56a uses the rotation angle θ1 and the rotation angle θ2 as described above. If the steering torque T ′ is estimated based on the angle difference between the rotation angle θ1 ′ and the rotation angle θ2, the interpolation unit 56b then performs gain correction on the estimated steering torque T ′. To do. The gain correction of the estimated steering torque T ′ in the interpolation unit 56b is performed by changing the gain G in accordance with the electrical angle so as to suppress the obtained steering torque T from falling in a sine wave shape.

  Specifically, when the output signal in which an abnormality has occurred is a sine wave signal of the resolver 42 or 44, the gain G gradually increases from near 0 ° to 90 ° from near 0 ° to 180 ° in electrical angle. It becomes smaller toward “1” and gradually increases from “1” from 90 ° to around 180 ° and becomes very large around an electrical angle of 180 °, and from around 180 ° to 360 ° (= 0 °). ) In the vicinity, it gradually decreases toward “1” from around 180 ° to 270 °, and gradually increases from “1” from around 270 ° to around 360 °, and becomes very large around 360 ° electrical angle.

  On the other hand, when the output signal in which an abnormality has occurred is a cosine wave signal of the resolver 42 or 44, the gain G gradually increases from “1” in the vicinity of an electrical angle of 0 ° to 90 ° as shown in FIG. It becomes very large near the electrical angle of 90 °, gradually decreases from “90” to 180 ° from “90” to 180 °, and gradually decreases toward “1” and from “180” to “270”. It gradually increases from 1 ”and becomes very large in the vicinity of the electrical angle of 270 °, and gradually decreases toward“ 1 ”from the vicinity of the electrical angle of 270 ° to 360 ° (= 0 °).

  Thus, when the gain correction of the estimated steering torque T ′ is performed by the interpolation unit 56b, the estimated steering torque T ′ is interpolated according to the detected electrical angle, thereby suppressing the sine wave from dropping. T is obtained (T = G · T ′). For this reason, according to the present embodiment, even if any of the output signals of the resolvers 42 and 44 is replaced as described above, the obtained steering torque T is suppressed from falling in a sine wave shape.

  Further, when the output signal in which the abnormality has occurred is a sine wave signal of the resolver 42 or 44, the arithmetic unit 30 determines that the detected electrical angle is not within the electrical proximity range of 0 ° or the electrical proximity range of 180 °. In such a case, the gain correction is performed by the interpolation unit 56b. On the other hand, when it is determined that the detected electrical angle is within the electrical angle vicinity range of 0 ° or the electrical angle vicinity of 180 °, the interpolation unit 56b uses the estimated steering torque T ′ from the reference detection unit 56a. Without detection, the steering torque T is detected. Specifically, the estimated steering torque T ′ from the reference detection unit 56a is replaced with a predetermined value, for example, obtained immediately before the electrical angle enters the 0 ° electrical angle vicinity range or 180 ° electrical angle vicinity range. The value (previous value) of the steering torque T is maintained or the previous value is further corrected and detected as the current steering torque T.

  The arithmetic unit 30 also determines that the detected electrical angle is not within the electrical proximity range of 90 ° or the electrical proximity range of 270 ° when the output signal in which the abnormality has occurred is the cosine wave signal of the resolver 42 or 44. In such a case, the gain correction is performed by the interpolation unit 56b. On the other hand, when it is determined that the detected electrical angle is within the electrical angle vicinity range of 90 ° or within the electrical angle vicinity range of 270 °, the interpolation unit 56b uses the estimated steering torque T ′ from the reference detection unit 56a. Without detection, the steering torque T is detected. Specifically, the estimated steering torque T ′ from the reference detection unit 56a is replaced with a predetermined value, and obtained, for example, immediately before the electrical angle enters the 90 ° electrical angle vicinity range or 270 ° electrical angle vicinity range. The value (previous value) of the steering torque T is maintained or the previous value is further corrected and detected as the current steering torque T.

  Thus, in the vicinity of the electrical angle at which the estimated steering torque T ′ becomes zero, the previous value exceeding zero or the like is used as the steering torque T by the interpolation unit 56b. For this reason, according to the present embodiment, any one of the output signals of the resolvers 42 and 44 is caused by abnormality, and thus the same sine wave signal or cosine wave signal among the normal output signals as described above. In the case where the estimated steering torque T ′ is zero, it is avoided that the obtained steering torque T becomes zero (see FIG. 7).

  When the torque detection unit 56 detects the steering torque T in the interpolation unit 56b when an abnormality occurs in any of the output signals of the resolvers 42 and 44, the torque detection unit 56 directs the value of the steering torque T to the target motor current calculation unit 58. Output. Then, the target motor current calculation unit 58 calculates a target motor current for driving the electric motor 32 based on the steering torque T.

  Therefore, according to this embodiment, when an abnormality such as disconnection occurs in the sine wave signal (sin phase output) of one resolver 42, 44 of the output signals of the pair of resolvers 42, 44, 0 ° and 180 °. It is possible to avoid the steering torque T used for calculating the target motor current from being a small value near zero near the electrical angle of °, and the cosine wave signal ( When an abnormality such as disconnection occurs in the cos phase output), the steering torque T used for calculating the target motor current is avoided to be a small value near zero near the electrical angles of 90 ° and 270 °. can do.

  In this regard, according to the torque sensor 10 of the present embodiment, even when an abnormality occurs in any one of the output signals of the pair of resolvers 42 and 44, the steering torque over the entire electrical angle range of 0 ° to 360 °. It is possible to detect T with a certain degree of accuracy. Moreover, it is avoided that the obtained steering torque T becomes excessive in the entire electric angle range of 0 ° to 360 °. Therefore, the target motor current based on the detected steering torque T can be obtained with a certain degree of accuracy over the entire electric angle range of 0 ° to 360 °, and as a result, the electric motor 32 is used to assist the steering operation by the driver. Assist torque can be generated, and assist control for reducing the burden of steering operation by the driver using the electric motor 32 can be temporarily continued.

  In the first embodiment described above, the torque detector 56 of the arithmetic device 30 is in the “torque detection means” described in the claims, and the arithmetic device 30 is abnormal among all the output signals of the resolvers 42 and 44. The interpolating unit 56b corrects the gain of the estimated steering torque T ′ by substituting the output value of one output signal with the output value of another output signal for “alternative means” described in the claims. In the “gain correction means” described in the claims, the interpolation unit 56b replaces the estimated steering torque T ′ with the previous value in the vicinity of the electrical angle at which the estimated steering torque T ′ becomes zero. In the “replacement means” described in the range, a value obtained by the gain correction by the interpolation unit 56b and a value obtained by substitution near the electrical angle at which the estimated steering torque T ′ becomes zero are detected as the steering torque T. Is the scope of claims The "interpolated torque detecting means" described in, corresponds respectively.

  In the first embodiment described above, the estimated steering torque T ′ estimated after one of the output signals of the resolvers 42 and 44 is replaced is interpolated. In contrast, in the second embodiment of the present invention, in the configuration shown in FIGS. 1 to 3, instead of interpolation of the estimated steering torque T ′ in the torque detector 56, the target in the target motor current calculator 58 is used. This is realized by interpolating the motor current.

  FIG. 8 is a diagram showing a flow of processing realized when an abnormality occurs in any one of the output signals of the first and second resolvers 42 and 44 of the resolver 40 in the present embodiment. Indicates. FIG. 8 shows a state where an abnormality has occurred in the cosine wave signal cos θ1 of the first resolver 42.

  In the present embodiment, when the arithmetic unit 30 determines that any one of the output signals of the resolvers 42 and 44 is abnormal, it is determined in advance as in the first embodiment. In accordance with the rules, the output value of the output signal in which the abnormality has occurred is replaced with the output value of another output signal. Specifically, when an abnormality occurs in the output signals sin θ1 and cos θ1 of the first resolver 42, the input side rotation angle detection unit 52 of the arithmetic unit 30 uses the alternative value as the rotation angle θ1 of the input shaft 22 to rotate the rotation angle. θ1 ′ is estimated, and the torque detector 56 calculates an angular difference between the estimated rotation angle θ1 ′ of the input shaft 22 and the rotation angle θ2 of the output shaft 24 detected based on the output signal of the second resolver 44. The steering torque T is detected as the torsion angle Δθ of the torsion bar 26. Further, when an abnormality occurs in the output signals sin θ2 and cos θ2 of the second resolver 44, the output side rotation angle detection unit 54 of the arithmetic unit 30 uses the alternative value to set the rotation angle θ2 ′ as the rotation angle θ2 of the output shaft 24. Then, the torque detector 56 estimates the angular difference between the rotation angle θ1 of the input shaft 22 detected based on the output signal of the first resolver 42 and the estimated rotation angle θ2 ′ of the output shaft 24 torsion bar 26. And a steering torque T is detected.

  If the arithmetic unit 30 determines that an abnormality has occurred in any one of the output signals of the resolvers 42 and 44, is the output signal in which the abnormality has occurred a sine wave signal (sin phase output)? Alternatively, it is determined whether the signal is a cosine wave signal (cos phase output), and the rotation angle θ2 of the output shaft 24 or the input shaft 22 is based on the output signals of the resolvers 44 and 42 in which both the sine wave signal and the cosine wave signal are normal. Alternatively, in detecting θ1, the electrical angle in the normal resolvers 44 and 42 is detected.

  When the output signal in which the abnormality has occurred is a sine wave signal of the resolver 42 or 44, the arithmetic unit 30 determines whether the detected electrical angle is in the vicinity of the electrical angle of 0 ° or in the vicinity of the electrical angle of 180 °. On the other hand, if the output signal in which the abnormality has occurred is a cosine wave signal of the resolver 42 or 44, the detected electrical angle is within the 90 ° electrical angle vicinity range or the 270 ° electrical angle vicinity range. It is discriminated whether or not there is. This “neighborhood” indicates a predetermined vertical range with respect to the reference value, and is set to ± 10 °, for example.

  FIG. 9 is a diagram for explaining an interpolation process performed when one of the output signals of the resolvers 42 and 44 is abnormal in the present embodiment. FIG. 10 is a diagram for explaining the effect of the interpolation processing in this embodiment.

  Information on the steering torque T detected by the torque detector 56 is supplied to the target motor current calculator 58. When the arithmetic unit 30 determines that any one of the output signals of the resolvers 42 and 44 is abnormal, the target motor current calculation unit 58 starts with the steering torque from the torque detection unit 56. Based on T, a target motor current Ibase serving as a reference necessary for driving the electric motor 32 is calculated so that an appropriate assist torque is applied to the rack 20. Then, the reference target motor current Ibase is gain-corrected. The gain correction of the reference target motor current Ibase is performed by changing the gain G in accordance with the electrical angle so as to suppress the obtained target motor current I from falling in a sine wave shape as the steering torque T falls. Is called.

  Specifically, when the output signal in which an abnormality has occurred is a sine wave signal of the resolver 42 or 44, the gain G gradually increases from near 0 ° to 90 ° from near 0 ° to 180 ° in electrical angle. It becomes smaller toward “1” and gradually increases from “1” from 90 ° to around 180 ° and becomes very large around an electrical angle of 180 °, and from around 180 ° to 360 ° (= 0 °). ) In the vicinity, it gradually decreases toward “1” from around 180 ° to 270 °, and gradually increases from “1” from around 270 ° to around 360 °, and becomes very large around 360 ° electrical angle.

  On the other hand, when the output signal in which the abnormality has occurred is a cosine wave signal of the resolver 42 or 44, the gain G gradually increases from “1” in the vicinity of the electrical angle of 0 ° to 90 °, and near the electrical angle of 90 °. It becomes very large, gradually decreasing from “90” to 180 ° from “90” to 180 ° and gradually increasing from “1” from 180 ° to 270 °. It becomes very large near the electrical angle 270 °, and gradually decreases toward “1” from the electrical angle 270 ° to 360 ° (= 0 °).

  When the target motor current calculation unit 58 corrects the gain of the reference target motor current Ibase in this way, the reference target motor current Ibase is interpolated according to the detected electrical angle, thereby suppressing a sine wave drop. The target motor current I is obtained (I = G · Ibase). For this reason, according to the present embodiment, the target motor to be supplied to the electric motor 32 even if the steering torque T obtained by replacing the output signal of any one of the resolvers 42 and 44 as described above falls in a sine wave shape. The current I is suppressed from dropping in a sine wave shape.

  Further, when the output signal in which the abnormality has occurred is a sine wave signal of the resolver 42 or 44, the arithmetic unit 30 determines that the detected electrical angle is not within the electrical proximity range of 0 ° or the electrical proximity range of 180 °. If so, the target motor current calculation unit 58 performs the above gain correction. On the other hand, when it is determined that the detected electrical angle is within the electrical angle vicinity range of 0 ° or the electrical angle vicinity of 180 °, the target motor current calculation unit 58 sets the reference target motor current Ibase based on the steering torque T. The target motor current I is calculated without using it. Specifically, the reference target motor current Ibase based on the steering torque T from the torque detector 56 is replaced with a predetermined value, for example, the electrical angle is in the vicinity of the electrical angle of 0 ° or in the vicinity of the electrical angle of 180 °. The value (previous value) of the target motor current I obtained immediately before entering is held or the previous value is further corrected to calculate the current target motor current I.

  The arithmetic unit 30 also determines that the detected electrical angle is not within the electrical proximity range of 90 ° or the electrical proximity range of 270 ° when the output signal in which the abnormality has occurred is the cosine wave signal of the resolver 42 or 44. If so, the target motor current calculation unit 58 performs the above gain correction. On the other hand, when it is determined that the detected electrical angle is within the electrical angle vicinity range of 90 ° or within the electrical angle vicinity range of 270 °, the target motor current calculation unit 58 determines the reference target motor current Ibase based on the steering torque T. The target motor current I is calculated without using it. Specifically, the reference target motor current Ibase based on the steering torque T from the torque detector 56 is replaced with a predetermined value, for example, the electrical angle is in the vicinity of the electrical angle of 90 ° or in the vicinity of the electrical angle of 270 °. The value (previous value) of the target motor current I obtained immediately before entering is held or the previous value is further corrected to calculate the current target motor current I.

  As described above, the target motor current calculation unit 58 uses the previous value exceeding zero as the target motor current I near the electrical angle at which the detected steering torque T and the reference target motor current Ibase are zero. For this reason, according to the present embodiment, any one of the output signals of the resolvers 42 and 44 is caused by abnormality, and thus the same sine wave signal or cosine wave signal among the normal output signals as described above. In the case where the detected steering torque T and the reference target motor current Ibase are zero, it is avoided that the obtained target motor current I becomes zero (see FIG. 10).

  Therefore, according to this embodiment, when an abnormality such as disconnection occurs in the sine wave signal (sin phase output) of one resolver 42, 44 of the output signals of the pair of resolvers 42, 44, 0 ° and 180 °. In the vicinity of the electrical angle of °, the calculated target motor current can be prevented from becoming a small value near zero, and the cosine wave signal (cos phase output) of one of the resolvers 42 and 44 is disconnected. When the abnormality occurs, it is possible to avoid that the calculated target motor current becomes a small value near zero near the electrical angles of 90 ° and 270 °.

  In this regard, according to the electric power assist device 12 of the present embodiment, even when an abnormality occurs in any one of the output signals of the pair of resolvers 42 and 44, the entire electrical angle range of 0 ° to 360 ° is obtained. It is possible to calculate the target motor current I with a certain degree of accuracy. Moreover, it is avoided that the target motor current I to be obtained becomes excessive in the entire electrical angle range of 0 ° to 360 °. For this reason, the assist torque for assisting the steering operation by the driver using the electric motor 32 can be generated, and the assist control for reducing the burden of the steering operation by the driver using the electric motor 32 is temporarily continued. It is possible. Further, since the fluctuation amount of the motor current to the electric motor 32 is small, it is possible to improve the occurrence of the catch in the steering operation process.

  In the second embodiment described above, the torque detector 56 of the arithmetic unit 30 includes the “torque detector” described in the claims, and the target motor current calculator 58 includes the “target” described in the claims. Claim that the calculation device 30 replaces the output value of one output signal in which an abnormality has occurred among all the output signals of the resolvers 42 and 44 with the output value of another output signal in the “motor current calculation means”. The target motor current calculation unit 58 performs a gain correction of the reference target motor current Ibase based on the steering torque T in the “gain correction unit” described in the claims. In the “replacement means” described in the claims, the calculation unit 58 replaces the reference target motor current Ibase with the previous value or the like in the vicinity of the electrical angle at which the reference target motor current becomes zero. It is described in the claims that the value obtained by the motor current calculation unit 58 by gain correction and the value obtained by replacing near the electrical angle at which the reference target motor current becomes zero are calculated as the target motor current. It corresponds to “post-interpolation target motor current calculation means”.

  In the first and second embodiments described above, an assist torque proportional to the steering torque T is calculated, and a target motor current necessary for driving the electric motor 32 is calculated so that the assist torque is applied to the rack 20. Then, assist control is performed so that the target motor current flows through the electric motor 32. In contrast, in the third embodiment of the present invention, in the configuration shown in FIGS. 1 to 3, the target steering angular velocity is obtained according to the steering torque T so that the actual steering angular velocity matches the target steering angular velocity. This is realized by calculating a target motor current to be supplied to the electric motor 32 and performing assist control so that the target motor current flows through the electric motor 32.

  FIG. 11 is a diagram showing a flow of processing realized when an abnormality occurs in any one of the output signals of the first and second resolvers 42 and 44 of the resolver 40 in the present embodiment. Indicates. FIG. 11 shows a state where an abnormality has occurred in the cosine wave signal cos θ1 of the first resolver 42. FIG. 12 is a diagram for explaining an interpolation process performed when one of the output signals of the resolvers 42 and 44 is abnormal in this embodiment. FIG. 13 is a diagram for explaining the effect of the interpolation processing in this embodiment.

  In the present embodiment, the arithmetic unit 30 detects the steering torque T by the torque detector 56 as in the first embodiment. Even when an abnormality occurs in any one of the output signals of the pair of resolvers 42 and 44, the steering torque T is interpolated by performing the gain correction as described above. Then, the value of the steering torque T is output toward the target motor current calculation unit 58. The target motor current calculation unit 58 calculates a target motor current for driving the electric motor 32 based on the steering torque T.

  Specifically, the target motor current calculation unit 58 first obtains a target steering angular velocity of a steering system such as the steering shaft 16 according to the steering torque T from the torque detection unit 56. It is determined whether or not the steering torque T from the torque detector 56 is equal to or greater than a predetermined threshold value. When the initial value of the target steering angular velocity is set to zero and it is determined that the steering torque is equal to or greater than the threshold value, target steering is performed. The angular velocity is incremented by a predetermined amount. On the other hand, when it is determined that the steering torque is less than the threshold value, the target steering angular velocity is decremented by a predetermined amount.

  Information on the steering angular velocity actually generated in the steering system is input to the target motor current calculation unit 58. The target motor current calculation unit 58 calculates the target motor current that should flow through the electric motor 32 so that the actual steering angular velocity matches the target steering angular velocity calculated as described above.

  Accordingly, also in this embodiment, as in the first embodiment, an abnormality such as disconnection occurs in the sine wave signal (sin phase output) of one resolver 42, 44 among the output signals of the pair of resolvers 42, 44. In this case, the steering torque T used for calculating the target motor current near the electrical angles of 0 ° and 180 ° can be avoided from becoming a small value near zero. When an abnormality such as disconnection occurs in the cosine wave signals (cos phase output) of 42 and 44, the steering torque T used for calculating the target motor current is near zero near the electrical angles of 90 ° and 270 °. Can be avoided.

  In this regard, according to the torque sensor 10 of the present embodiment, even when an abnormality occurs in any one of the output signals of the pair of resolvers 42 and 44, the steering torque over the entire electrical angle range of 0 ° to 360 °. It is possible to detect T with a certain degree of accuracy. Moreover, it is avoided that the obtained steering torque T becomes excessive in the entire electric angle range of 0 ° to 360 °. For this reason, the driver uses the electric motor 32 by performing feedback control so that the steering angular speed of the steering system matches the target steering angular speed based on the detected steering torque T and causing the target motor current to flow through the electric motor 32. Assist torque for assisting the steering operation can be generated, and assist control for reducing the burden of steering operation by the driver using the electric motor 32 can be temporarily continued. Further, since the feedback control of the steering angular velocity is performed, it is possible to improve the deterioration of the steering shaft 16 steering wheel return.

  In the third embodiment described above, the torque detector 56 of the arithmetic device 30 is set to “torque detection means” described in the claims, and the arithmetic device 30 is abnormal among all output signals of the resolvers 42 and 44. The interpolating unit 56b corrects the gain of the estimated steering torque T ′ by substituting the output value of one output signal with the output value of another output signal for “alternative means” described in the claims. In the “gain correction means” described in the claims, the interpolation unit 56b replaces the estimated steering torque T ′ with the previous value in the vicinity of the electrical angle at which the estimated steering torque T ′ becomes zero. In the “replacement means” described in the range, a value obtained by the gain correction by the interpolation unit 56b and a value obtained by substitution near the electrical angle at which the estimated steering torque T ′ becomes zero are detected as the steering torque T. Is the scope of claims The "interpolated torque detecting means" described in, corresponds respectively.

  In the third embodiment, the target motor current calculation means 58 obtains the target steering angular velocity of the steering system in accordance with the steering torque T from the torque detector 56 according to the claims. The target motor current calculation unit 58 calculates the target motor current to be supplied to the electric motor 32 so that the actual steering angular speed matches the target steering angular speed. It corresponds to “motor current calculation means”.

  In the third embodiment, the target steering angular velocity is set according to the steering torque T after interpolation such as gain correction is performed on the steering torque T from the torque detector 56 as in the first embodiment. The target motor current to be passed through the electric motor 32 is calculated so that the actual steering angular velocity matches the target steering angular velocity, and assist control is performed so that the target motor current flows through the electric motor 32. However, the target steering angular velocity is obtained according to the estimated steering torque T ′ without performing interpolation such as gain correction, and immediately before the electrical angle enters the range near the electrical angle where the estimated steering torque T ′ becomes zero. The obtained target steering angular velocity value (previous value) may be held or the previous value may be further corrected and detected as the current target steering angular velocity.

  By the way, in said 1st-3rd Example, although the twin resolver type torque sensor 10 and the electric power assist apparatus 12 are applied to the power steering system mounted in a vehicle, this invention is limited to this. Instead, it may be applied to a system other than the vehicle.

DESCRIPTION OF SYMBOLS 10 Twin resolver type torque sensor 12 Electric power assist apparatus 22 Input shaft 24 Output shaft 26 Torsion bar 30 Arithmetic apparatus 32 Electric motor 40 Resolver 42 1st resolver 44 2nd resolver 52 Input side rotation angle detection part 54 Output side rotation angle detection part 56 Torque detection unit 56a Reference detection unit 56b Interpolation unit 58 Target motor current calculation unit

Claims (7)

A first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and an output shaft connected to the input shaft via a torsion bar A second resolver that outputs the sine wave signal and the cosine wave signal according to the rotation of the first resolver, the rotation angle of the input shaft based on the output signal of the first resolver, and the output shaft based on the output signal of the second resolver A torque detector that detects torque transmitted from the input shaft to the output shaft via the torsion bar based on a difference between the rotation angle and the twin resolver torque sensor,
Substitution for substituting the output value of one output signal with the output value of another output signal when an abnormality is detected in one of the output signals of the first resolver and the second resolver With means,
The torque detecting means includes
Gain correction means for gain correcting the estimated torque detected using the output value of the one output signal obtained by substitution by the substitution means;
Replacement means for replacing the estimated torque with a predetermined value in the vicinity of a predetermined electrical angle;
When said abnormality is detected, the interpolated torque detecting means for detecting the estimated torque obtained by the gain correction means and said substituting means as the torque,
A twin resolver torque sensor. 2. The twin resolver torque according to claim 1, wherein the replacing means replaces the estimated torque near a predetermined electrical angle with the value of the torque obtained immediately before entering the vicinity of the predetermined electrical angle. Sensor.   The twin resolver torque sensor according to claim 1 or 2, wherein the gain correction means corrects the estimated torque with a gain corresponding to an electrical angle. A first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and an output shaft connected to the input shaft via a torsion bar A second resolver that outputs the sine wave signal and the cosine wave signal according to the rotation of the first resolver, the rotation angle of the input shaft based on the output signal of the first resolver, and the output shaft based on the output signal of the second resolver Torque detection means for detecting torque transmitted from the input shaft to the output shaft via the torsion bar based on the difference between the rotation angle and the torque detected by the torque detection means, An electric power assist device comprising: a target motor current calculating means for calculating a target motor current to be passed through an assist motor provided on the output shaft side;
Substitution for substituting the output value of one output signal with the output value of another output signal when an abnormality is detected in one of the output signals of the first resolver and the second resolver With means,
The target motor current calculation means includes
Gain correction means for gain-correcting a calculated motor current calculated based on the torque detected using the output value of the one output signal obtained by substitution by the substitution means;
Replacing means for replacing the calculated motor current with a predetermined value near a predetermined electrical angle;
An interpolated target motor current calculating means for calculating the calculated motor current obtained by the gain correcting means and the replacing means as the target motor current when the abnormality is detected;
An electric power assist device comprising: 5. The electric motor according to claim 4, wherein the replacement means replaces and holds the calculated motor current near a predetermined electrical angle with a value of the target motor current obtained immediately before entering the vicinity of the predetermined electrical angle. Power assist device.   The electric power assist device according to claim 4 or 5, wherein the gain correction means corrects the calculated motor current with a gain corresponding to an electrical angle. A first resolver that outputs a sine wave signal whose amplitude changes in a sine wave shape according to the rotation of the input shaft and a cosine wave signal whose amplitude changes in a cosine wave shape, and an output shaft connected to the input shaft via a torsion bar A second resolver that outputs the sine wave signal and the cosine wave signal according to the rotation of the first resolver, the rotation angle of the input shaft based on the output signal of the first resolver, and the output shaft based on the output signal of the second resolver Torque detection means for detecting torque transmitted from the input shaft to the output shaft via the torsion bar based on the difference between the rotation angle and the target rotation based on the torque detected by the torque detection means Target rotational angular velocity calculating means for calculating an angular velocity, and a target motor to be supplied to the assist motor provided on the output shaft side so that the rotational angular velocity matches the target rotational angular velocity. The electric power assist device comprising: a target motor current calculating means for calculating a current, a,
Substitution for substituting the output value of one output signal with the output value of another output signal when an abnormality is detected in one of the output signals of the first resolver and the second resolver With means,
The torque detecting means includes
Gain correction means for gain correcting the estimated torque detected using the output value of the one output signal obtained by substitution by the substitution means;
Replacement means for replacing the estimated torque with a predetermined value in the vicinity of a predetermined electrical angle;
A post-interpolation torque detecting means for detecting the estimated torque obtained by the gain correcting means and the replacing means as the torque when the abnormality is detected;
And having
The target rotational angular velocity calculating unit increments the target rotational angular velocity when the torque detected by the torque detecting unit is equal to or greater than a threshold value, and on the other hand, calculates the target rotational angular velocity when the torque is less than the threshold value. An electric power assist device that decrements.

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