JP4138631B2 - Rotation angle detection device and electric power steering device - Google Patents

Description

  The present invention relates to a rotation angle detection device that detects a rotation angle of an output shaft of a motor based on an output signal of a resolver, and an electric power steering device using the rotation angle detection device.

  The resolver of the rotation angle detection device described in Patent Document 1 below has a pair of excitation windings excited by a two-phase sine wave of a fixed period generated by a fixed frequency oscillator, and an output corresponding to the rotation angle of the rotor. And a detection winding for generating the rotation angle of the rotor based on the ratio of the two-phase signal obtained by filtering the double component of the multiplication value of the output of the detection winding and the two-phase sine wave with a low-pass filter. It comes to detect.

In addition, the device disclosed in Patent Document 2 described below detects the rotation angle of the rotor of the motor by processing the output signal of the resolver with a resolver digital converter.
Japanese Patent Publication No.59-13708 JP 2000-55695 A

  By the way, what is described in the above-mentioned patent document 1 is detected based on the two-phase signal output from the low-pass filter because the multiplication component of the multiplication value of the output of the detection winding and the two-phase sine wave is filtered by the low-pass filter. In such a rotation angle, there is a problem in that advance or delay according to the rotation speed and rotation direction of the rotor occurs, and accurate detection of the rotation angle is hindered.

  Moreover, although what was described in the said patent document 2 can detect a rotation angle precisely by using a resolver digital converter, since the resolver digital converter is expensive, there exists a problem that cost increases.

  The present invention has been made in view of the above-mentioned circumstances, and when detecting the rotation angle of the output shaft of the motor from the output signal of the resolver, the rotation angle deviation caused by using the low-pass filter is detected with an inexpensive circuit. The purpose is to correct.

In order to achieve the above object, according to the first aspect of the present invention, a cos θ signal and sin θ obtained by filtering a harmonic component of a signal output from a resolver with a low-pass filter in accordance with the rotation angle θ of the output shaft of the motor. In a rotation angle detection device that calculates tan θ from a signal and applies the value of tan θ to a tan θ → θ conversion map to retrieve the rotation angle θ, motor rotation speed detection means for detecting the rotation speed of the motor, and the rotation direction of the motor Motor rotation direction detection means for detecting, correction value calculation means for calculating a correction value of the rotation angle θ from the rotation speed and rotation direction of the motor, and correction means for correcting the rotation angle θ using the correction value , The data interval of the gradient tan θ in the tan θ → θ conversion map is set more finely in a region smaller than a region where the absolute value of the rotation angle θ is large. A dispensing device is proposed.

  According to the second aspect of the present invention, the rotation angle detecting device according to the first aspect is provided in a brushless motor that assists the steering operation of the driver, and the rotation angle θ of the output shaft detected by the rotation angle detecting device is set. Based on this, an electric power steering apparatus is proposed which controls the energization of the brushless motor.

  Note that the adding means 63 of the embodiment corresponds to the correcting means of the present invention.

  According to the configuration of the first aspect, when the rotation angle θ of the output shaft of the motor is detected using the cos θ signal and the sin θ signal obtained by filtering the harmonic component of the signal output from the resolver by the low pass filter, the influence of the low pass filter is detected. Even if an error of advance or delay occurs in the rotation angle θ, the rotation angle θ is accurately detected by correcting the rotation angle θ with a correction value calculated based on the rotation speed and rotation direction of the motor. be able to. Moreover, since an expensive resolver digital converter is not used, it can be realized at a low cost.

Further, the data interval of the inclination tan θ in the tan θ → θ conversion map for retrieving the rotation angle θ from the value of tan θ is set more finely in the region smaller than the region where the absolute value of the rotation angle θ is large. A constant resolution can be ensured in all regions of the rotation angle θ while minimizing the amount of data.

  According to the configuration of the second aspect, since energization to the brushless motor of the electric power steering device is controlled based on the rotation angle θ of the output shaft detected with high accuracy by the rotation angle detection device, the brushless motor is driven efficiently. It is possible to reduce power consumption, increase output torque, reduce operating noise, and reduce torque ripple.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

1 to 12 show a first embodiment of the present invention. FIG. 1 is an overall perspective view of an electric power steering apparatus, FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. 1, and FIG. 4 is a block diagram showing the calculation flow of the microcomputer of the rotation angle sensor, FIG. 5 is a diagram showing the relationship between the rotation angle θ and the inclination tan θ, and FIG. 6 is a graph showing the rotation angle θ and the inclination tan θ. FIG. 7 is an explanatory diagram of processing for calculating the rotation angle θ from the inclination tan θ, FIG. 8 is a flowchart of the rotation angle calculation processing, and FIG. 9 is a map for searching for a correction value of the rotation angle θ from the rotation angular velocity ω. shows a flow chart of FIG. 10 is the rotational angle correction processing, FIG. 11 is a diagram showing an input waveform and an output waveform of the low-pass filter, 12 is tanθ calculated from Esinθ and Ecosθ low-pass filter outputs ^-1: E It is a diagram showing a waveform of NGLEMONI.

  As shown in FIGS. 1 and 2, a steering shaft 12 that rotates integrally with a steering wheel 11 of an automobile, and a pinion shaft 15 that extends from a gear casing 14 that is integrated with a rack and pinion type steering gear box 13 are paired. The universal joints 16 and 17 and the connecting shaft 18 are connected. Tie rods 19, 19 extending left and right from the steering gear box 13 are connected to the left and right front wheels WL, WR via knuckle (not shown).

  The pinion shaft 15 is rotatably supported via ball bearings 22 and 23 on the gear casing 14 and a cover 21 fixed to the upper surface of the gear casing 14 with bolts 20. A pinion 24 is provided at the lower end of a pinion shaft 15 that protrudes from the gear casing 14 into the steering gear box 13. The pinion 24 is formed in a steering rod 25 that is slidably supported in the left and right directions inside the steering gear box 13. Is engaged with the rack 26.

  A brushless motor 27 as an actuator is supported on the gear casing 14, and a worm 29 provided on the output shaft 28 of the brushless motor 27 meshes with a worm wheel 30 provided on the pinion shaft 15. Accordingly, the torque of the brushless motor 27 is transmitted to the pinion shaft 15 via the worm 29 and the worm wheel 30.

  The electronic control unit U of the power steering apparatus detects the rotation angle of the steering torque sensor 31 that detects the steering torque input to the steering wheel 11, the vehicle speed sensor 32 that detects the vehicle speed, and the output shaft 28 of the brushless motor 27. The rotation angle sensor 33 is connected to a current sensor 34 that detects the actual current flowing through the brushless motor 27, and the electronic control unit U controls the operation of the brushless motor 27 based on signals from these sensors 31 to 34. .

  Specifically, when the steering torque sensor 31 detects the steering torque generated by the driver operating the steering wheel 11, the target current is supplied to the brushless motor 27 so that the steering torque matches the target steering torque. The driver's steering operation is assisted with the output torque of the brushless motor 27. At this time, the target steering torque is corrected according to the vehicle speed detected by the vehicle speed sensor 32 so that the steering operation becomes light when the vehicle is traveling at low speed and the steering operation becomes heavy when the vehicle is traveling at high speed. When the target current is supplied to the brushless motor 27, the actual current flowing through the brushless motor 27 is detected by the current sensor 34, and feedback control is performed so that the actual current matches the target current.

  The brushless motor 27 includes a stator having a plurality of coils and a rotor having a permanent magnet, and it is necessary to switch the supply of three-phase AC to the plurality of coils in accordance with the rotation angle of the rotor (that is, the magnetic pole position of the permanent magnet). Therefore, the rotation angle of the rotor is detected by the rotation angle sensor 33 using a resolver. The more accurately the rotation angle of the output shaft 28 of the brushless motor 27 is detected by the rotation angle sensor 33, the more efficiently the brushless motor 27 is driven to reduce power consumption, increase output torque, reduce operating noise, and reduce torque ripple. Reduction is possible.

  Next, the structure of the rotation angle sensor 33 will be described with reference to FIGS.

The well-known resolver 41 provided in the brushless motor 27 includes a primary winding 42 and two secondary windings 43 and 44 arranged with a phase difference of 90 °. The rectangular wave output from the microcomputer 45 provided in the electronic control unit U is converted into a sine wave through the band-pass filter 46 and further passes through the amplifier 47 to become a sine wave reference signal E ₁ sinωt. Input to the primary winding 42. As a result, the first output signal E ₂ sinωtcos θ corresponding to the rotation angle θ of the output shaft 28 of the brushless motor 27 (that is, the rotation angle of the rotor) is provided to the two secondary windings 43 and 44, and the second output. The signal E ₂ sinωtsinθ is output.

A reference signal E _R1-R2 = E ₁ sin ωt is input to the microcomputer 45 via the differential amplifier 48, and the first output signal E _S1-S3 = E ₂ sin ωt cos θ of the two secondary windings 43 and 44 is input. The second output signal E _S2 -S4 = E ₂ sin ωtsin θ is input through the differential amplifiers 49 and 50, respectively. The reference signal E _R1-R2 and the first and second output signals E _S1-S3 , E _S2-S4 are respectively predetermined voltages (for example, 2.. 5V).

Subsequently, after the multiplier 54 multiplies the reference signal E _R1-R2 and the first output signal E _S1-S3 , it passes through the low-pass filter 55 to remove the harmonic component, thereby outputting the cos output voltage Ecosθ. to _{(E = E 1 E 2/} 2). Similarly, after the multiplier 56 multiplies the reference signal E _R1-R2 and the second output signal E _S2-S4 , it passes through the low-pass filter 57 and removes the harmonic component, thereby obtaining the sin output voltage Esinθ. output to _{(E = E 1 E 2/} 2). Then, the divider 58 divides the sin output voltage by the cos output voltage to calculate tan θ (= Esin θ / E cos θ).

  Here, the functions of the low-pass filters 55 and 57 will be further described with reference to FIGS.

  The broken line in FIG. 11 shows the cosine waveform before and after removing the harmonic component through the low-pass filter 55, and the cos waveform that has been synchronously detected after passing through the multiplier 54 has a sawtooth shape with the harmonic component on it. When it passes through the low-pass filter 55 and the harmonic component is removed, a smooth cos waveform is obtained. Similarly, the solid line in FIG. 11 shows the sin waveform before and after passing through the low-pass filter 57 and removing the harmonic component, and the sin waveform passing through the multiplier 56 and synchronously detected has a harmonic component on it. When the harmonic component is removed by passing through the low-pass filter 57, a smooth sin waveform is obtained. The cos waveform and sin waveform before removing the overtone component include many irregularly generated zero cross points, and in particular, the zero cross point of the cos waveform indicated by circles causes the following problems.

That is, when tan θ is calculated from the cos waveform and the sin waveform, if the double tone component is not removed by the low-pass filters 55 and 57, the value of tan θ diverges at the zero cross point of the cos waveform and cannot be calculated. . As a result, the tan θ ⁻¹ : EANGLEMONI graph shown in FIG. 12 is disturbed as indicated by a broken line, and the original graph indicated by a solid line cannot be obtained. However, in the present embodiment, the above-mentioned problem can be solved by removing irregular components by removing the harmonic components by the low-pass filters 55 and 57 (in particular, the zero cross point of the cosine waveform). it can.

  Subsequently, tan θ is converted into a corresponding rotation angle θ of the output shaft 28 of the brushless motor 27 using a tan θ (tilt) → θ (rotation angle) conversion map 59.

  Table 1 shows a tan θ → θ conversion map 59, and the resolution of the rotation angle θ is set to 10 °, for example. In this case, ten inclinations tan θ are set corresponding to ten rotation angles θ = 0 °, 10 °, 20 °... 80 °, 90 °, but as is apparent from FIGS. Even if the rotation angle θ is changed from 0 ° to 90 ° at 10 ° intervals, which are constant values, the interval of the inclination tanθ does not become a constant value, but increases rapidly as the rotation angle θ increases. For example, the difference in the gradient tan θ between the rotation angle θ of 10 ° and 20 ° is only 0.18, but the difference in the gradient tan θ between the rotation angle θ of 60 ° and 70 ° is It has reached 1.02.

  Therefore, in the tan θ → θ conversion map 59, if the interval of the inclination tan θ is set to a constant value, there is a problem that the resolution of the rotation angle θ becomes coarse in a region where the rotation angle θ is small, and the detection accuracy decreases. In a region where the angle θ is large, there is a problem that the resolution of the rotation angle θ becomes finer than necessary and the amount of map data increases. On the other hand, in this embodiment, the data interval of the inclination tanθ is made fine in the region where the absolute value of the rotation angle θ is small, and the data of the inclination tanθ is coarsened in the region where the absolute value of the rotation angle θ is large. A constant resolution is ensured in all regions of the rotation angle θ while minimizing the amount of data.

  As can be seen from FIG. 7, the graph of tan θ has a cycle of 180 °, and therefore, the inclination tan θ during the rotation of the output shaft 28 of the brushless motor 27, that is, in the range of −180 ° ≦ rotation angle θ ≦ 180 °. Will take the same value twice. For example, the rotation angle θ at which tan θ = 1 becomes θ = −135 ° and θ = 45 °, and the rotation angle θ is not uniquely determined. Therefore, it is necessary to uniquely determine the rotation angle θ within the range of 360 ° from the gradient tan θ according to the sign of the cos output voltage and the sin output voltage. The procedure will be described below with reference to FIGS.

  First, in step S1, the value of the gradient tan θ is calculated from Esin θ / Ecos θ. The value of the inclination tan θ is in the range of −∞ <tan θ <∞, and if tan θ <0 in step S2, that is, the region A (90 ° <θ <180 °) or the region C (−90 °) in FIG. If <θ <0 °), the value of the gradient tan θ is converted from a negative value to a positive value in step S3, and the flag G TAN is set to “0”. On the other hand, if 0 ≦ tan θ in step S2, that is, if the region B (0 ≦ θ ≦ 90 °) or the region D (−180 ° ≦ θ <≦ 90 °) in FIG. TAN is set to “1”. In step S5, the rotation angle θ is retrieved from the inclination tan θ using the tan θ → θ conversion map 59. Thus, if the inclination tan θ is a negative value, the rotation angle θ is searched after converting it to a positive value. Therefore, if the tan θ → θ conversion map 59 is set only in a region where the inclination tan θ is a positive value. As a result, the data amount of the tan θ → θ conversion map 59 can be reduced.

In the subsequent step S6, if the flag G TAN is “0” and tan θ <0, the sign of the rotation angle θ retrieved from the tan θ → θ conversion map 59 is reversed in step S7, and the actual rotation angle θ Is calculated. If Re cos [theta]> 0 Der In the subsequent step S8, that is, if the B region and C region in FIG. 7, directly outputs the rotation angle θ in step S13. On the other hand, if cos θ> 0 is not satisfied in step S8 and sin θ> 0 in step S9, that is, if the rotation angle θ is a negative value in the region A in FIG. 7, the rotation angle θ + π is rotated in step S10. The angle θ is set, and the rotation angle θ is output in step S13. If cos θ> 0 is not satisfied in step S8, sin θ> 0 is not satisfied in step S9, and sin θ <0 is satisfied in step S11, that is, the rotation angle θ is a positive value in the region D of FIG. For example, the rotation angle θ−π is set as the rotation angle θ in step S12, and the rotation angle θ is output in step S13. Thus, by considering which of the regions A to D in FIG. 7 is based on the signs of sin θ and cos θ, −180 ° ≦ rotation angle θ ≦ based on the value of the gradient tan θ. The rotation angle θ can be uniquely determined in the range of 180 °.

By the way, when the cos output voltage Ecosθ is generated by filtering the multiplication value of the reference signal E _R1-R2 and the first output signal E _S1-S3 by the low-pass filter 55 to remove the harmonic component, the low-pass filter 55 As a result, a phase shift occurs in the rotation angle θ. Similarly, when the sin output voltage Esin θ is generated by filtering the multiplication value of the reference signal E _R1-R2 and the second output signal E _{S2-S4 by} the multiplier 56 to remove the double component, 57 causes a phase shift in the rotation angle θ.

  As shown in FIG. 9, since there is a one-to-one relationship between the rotational angular velocity ω of the output shaft 28 of the brushless motor 27 and the phase shift of the rotational angle θ, the rotational angle can be detected if the rotational speed of the brushless motor 27 is detected. A correction value for the phase of θ can be calculated. That is, the rotational speed of the brushless motor 27 is detected by the motor rotational speed detecting means 60 of FIG. 4, the rotational direction of the brushless motor 27 is detected by the motor rotational direction detecting means 61, and the map of FIG. Then, the correction value of the rotation angle θ is calculated, and the correction value is added to the raw rotation angle θ output from the tan θ → θ conversion map 59 by the adder 63 to output the corrected rotation angle θ.

  The above operation will be further described based on the flowchart of FIG.

  First, the previous value θ1 of the rotation angle of the output shaft 28 of the brushless motor 27 is stored in step S21, the current value θ of the rotation angle of the output shaft 28 is calculated in step S22, and the difference between the current value and the previous value is calculated in step S23. The amount of change in the rotation angle is calculated as θ−θ1. In step S24, the rotation angle velocity ω of the output shaft is calculated by dividing the change amount of the rotation angle by the control period.

  If the rotational angular velocity ω is negative in the following step S25, the sign of the rotational angular velocity ω is reversed to a positive value in step S26, and the flag Gω is set to “0”. If is a positive value, the flag Gω is set to “1” in step S27. In step S28, the rotational angular velocity ω is applied to the map of FIG. 9 to search for a correction value of the rotational angle θ. Thus, by converting the negative rotation angular velocity ω to a positive value, the map in FIG. 9 only needs to be set for the positive rotation angular velocity ω, and the amount of map data can be reduced.

  In subsequent step S29, if the flag Gω is “1” and the rotational angle θ is a positive value, the corrected rotational angle θ is calculated by adding the correction value to the rotational angle θ before correction in step S30, If the flag Gω is “0” and the rotation angle θ is negative in step S29, the corrected rotation angle θ is calculated by subtracting the correction value from the rotation angle θ before correction in step S31.

  As described above, the rotation angle θ of the output shaft 28 of the brushless motor 27 can be accurately detected without using an expensive resolver digital converter, which can contribute to the cost reduction of the rotation angle sensor 33.

  Next, a second embodiment of the present invention will be described with reference to FIGS. Among the constituent elements of the second embodiment, those corresponding to the constituent elements of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and redundant description is omitted.

The sample timing generation circuit 64 to which the reference signal E _R1-R2 = E ₁ sinωt is input from the differential amplifier 48 outputs a sample timing signal corresponding to the reference signal E _R1-R2 . The sample and hold circuits 65 and 66 to which the sample timing signal is inputted have the first output signal E _S1-S3 = E ₂ sinωtcos θ and the second output signal E _S2-S4 = E of the two secondary windings 43 and 44. ₂ sin ωtsin θ is sampled and held in synchronization with the sample timing signal. The outputs of the sample and hold circuits 65 and 66 are filtered by the low-pass filters 67 and 68, respectively, and the high frequency components are removed to obtain E ₂ cos θ and E ₂ sin θ (see FIG. 14). The cos output voltage Ecosθ and the sin output voltage Esinθ are generated by correcting so that the midpoint of the amplitude is a common predetermined voltage (for example, 2.5 V) in 52 and 53. The subsequent operation is the same as that of the first embodiment described above.

  According to the second embodiment, in addition to the effects of the first embodiment, a part of the processing performed in the microcomputer 45 in the first embodiment is performed outside the microcomputer 45, whereby the microcomputer 45 Can reduce the load.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, the invention described in claim 1 can be applied to a motor for any application other than the electric power steering apparatus, and the motor is not limited to a brushless motor.

Overall perspective view of electric power steering device 2-2 line enlarged sectional view of FIG. Block diagram showing structure of rotation angle sensor Block diagram showing calculation flow of microcomputer of rotation angle sensor The figure which shows the relationship between rotation angle (theta) and inclination tan (theta). A graph showing the relationship between the rotation angle θ and the inclination tan θ Explanatory drawing of the process which calculates rotation angle (theta) from inclination tan (theta). Flow chart of rotation angle calculation process The figure which shows the map which searches the correction value of rotation angle (theta) from rotation angular velocity (omega) Flow chart of rotation angle θ correction processing Diagram showing input and output waveforms of low-pass filter The figure which shows the waveform of tan (theta) < ^-1 >: EANGLEMONI computed from Esin (theta) and Ecos (theta) which a low-pass filter outputs The block diagram which shows the structure of the rotation angle sensor which concerns on 2nd Example. The block diagram which shows the circuit of the microcomputer of the rotation angle sensor which concerns on 2nd Example.

Explanation of symbols

27 Brushless motor (motor)
28 output shaft 41 resolver 59 tan θ → θ conversion map 60 motor rotation speed detection means 61 motor rotation direction detection means 62 correction value calculation means 63 addition means (correction means)

Claims (2)

From the cos θ signal and the sin θ signal obtained by filtering the harmonic component of the signal output from the resolver (41) according to the rotation angle θ of the output shaft (28) of the motor (27) by the low-pass filter (55, 57, 67, 68). In the rotation angle detection device that calculates tan θ and applies the value of tan θ to the tan θ → θ conversion map (59) to search for the rotation angle θ.
Motor rotation speed detection means (60) for detecting the rotation speed of the motor (27), motor rotation direction detection means (61) for detecting the rotation direction of the motor (27), rotation speed and rotation direction of the motor (27) Correction value calculation means (62) for calculating the correction value of the rotation angle θ from the above, and correction means (63) for correcting the rotation angle θ using the correction value, and the inclination in the tan θ → θ conversion map (59) The rotation angle detecting device is characterized in that the data interval of tan θ is set finer in a region smaller than a region where the absolute value of the rotation angle θ is large .   The brushless motor (27) that assists the steering operation of the driver is provided with the rotation angle detection device according to claim 1, and the brushless motor (27) is based on the rotation angle θ of the output shaft (28) detected by the rotation angle detection device. An electric power steering device that controls energization of the motor.

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