JP4763821B2 - Angle correction circuit, RD converter, and angle detection device - Google Patents

Description

  The present invention relates to an RD converter that converts a resolver signal output from a resolver that detects a rotation angle of a motor into a digital output angle, and an angle detection device including the RD converter, and more particularly to a configuration that satisfactorily corrects an angle error of the resolver. .

  Since the resolver normally has an angle error, it is necessary to correct the angle error in order to perform highly accurate angle detection.

  A method for correcting such a resolver angle error is described in Patent Document 1. In Patent Document 1, the output angle of the RD converter (R / D converter) when the resolver is rotated at a constant rotation number in advance is compared with the angle data reference obtained by measuring the resolver rotation over time, The angle error characteristic of the resolver is calculated and recorded in the correction memory, and the angle error characteristic is recorded in the correction memory in the form of an angle after correction with respect to the output angle of the RD converter.

  During operation, the output angle of the RD converter is input to the correction memory, and the corrected angle corresponding to the input output angle is output from the correction memory, thereby obtaining an angle in which the angle error is corrected. It has become.

JP-A-10-170531

  As described above, the correction of the angle error of the resolver described in Patent Document 1 is performed for the output angle of the RD converter. However, the angle error characteristic of the resolver via the RD converter varies depending on the rotational speed of the resolver, and the angle error that varies depending on the rotational speed cannot be handled by the correction method described in Patent Document 1. That is, there is a problem that the angle error cannot be corrected.

  In view of such problems, an object of the present invention is to provide an angle correction circuit that can correct an angle error satisfactorily even if the angle error characteristic of the resolver fluctuates depending on the rotational speed of the resolver. An object of the present invention is to provide an RD converter and an angle detection device provided with such an angle correction circuit.

  According to the first aspect of the present invention, the angle correction circuit added to the angle calculation circuit for converting the detected angle θ of the resolver signal output from the resolver of the one-phase excitation / two-phase output into the digital output angle φ is a digital output. A correction data unit that receives the angle φ and outputs the angle error of the resolver with respect to the digital output angle φ as correction data, a filter that has the same characteristics as the transfer function of the angle calculation circuit, and that receives the correction data; A subtractor that subtracts the output of the filter from the digital output angle φ and outputs a corrected angle.

  In the invention of claim 2, in the invention of claim 1, the correction data section stores the angle error of the resolver in the memory, reads the angle error for the input digital output angle φ from the memory, and outputs it as correction data.

In the invention of claim 3, in the invention of claim 1 or 2, the transfer function of the filter is:
K (τ ₁ s + 1) / (τ ₂ s ³ + s ² + Kτ ₁ s + K)
Where s: Laplace operator
K: Gain constant
τ ₁ : first time constant
τ ₂ : A second time constant.

  According to a fourth aspect of the present invention, the RD converter converts an angle θ detected by a resolver signal output from a one-phase excitation / two-phase output resolver into a digital output angle φ, and the first to third aspects. The angle correction circuit is provided.

  According to the invention of claim 5, the angle detection device comprises a resolver for one-phase excitation and two-phase output, an RD converter according to claim 4, and an excitation signal generator for supplying an excitation signal to the resolver and the RD converter. Prepare.

  According to the angle correction circuit of the present invention, even if the angle error characteristic of the resolver varies depending on the number of revolutions of the resolver, the angle error can be corrected well. Therefore, if this angle correction circuit is added to the angle calculation circuit that performs angle conversion processing, that is, if the RD converter is configured by the angle calculation circuit and the angle correction circuit, highly accurate angle detection is possible regardless of the error of the resolver. It can be performed.

The block diagram which shows the basic structural example of RD converter and an angle detection apparatus. The block diagram which simplified the structure of FIG. The graph which shows an example (only a fundamental frequency component) of the angle error characteristic of a resolver. The graph which shows the characteristic of RD converter of FIG. FIG. 5 is a graph showing a response of an output angle when a resolver angle θ _t having no error is input to the RD converter having the characteristics shown in FIG. 4 and an output angle error at that time. The graph which shows the response (angle error) of the output angle when angle error (theta) _e is input into RD converter which has the characteristic shown in FIG. The graph which shows the output angle error at the time of performing the conventional correction | amendment in the RD converter which has the characteristic shown in FIG. The block diagram which shows the structure of one Example of the RD converter by this invention. A is a block diagram in which the configuration of the angle calculation circuit in FIG. 8 is simplified, and B is a block diagram in which the block diagram of A is modified. The graph which showed the output angle error of the RD converter shown in FIG. 8 compared with the case where error correction is not performed (conventional example). The block diagram for demonstrating the production | generation and writing of correction data.

  First, the principle of calculating the angle of the resolver / RD converter will be described.

  FIG. 1 shows a basic configuration example of an RD converter together with a resolver and an excitation signal generator.

The resolver 10 has one-phase excitation and two-phase output, and the first resolver signal S1 and the second resolver signal S2 output from the resolver 10 are input to the RD converter 20. An excitation signal is input from the excitation signal generator 30 to the resolver 10 and the RD converter 20. When the excitation signal is sin ωt, the resolver signals S1 and S2 are
S1: cos θ sin ωt
S2: sin θ sin ωt
It becomes. θ represents the detection angle of the resolver 10.

  In this example, the RD converter 20 includes a first multiplier 21, a second multiplier 22, a subtractor 23, a synchronous detection circuit 24, a controller 25, a SIN ROM 26, and a COS ROM 27. The RD converter 20 converts the detected angle θ of the resolver signals S1 and S2 into a digital output angle φ in an angle calculation loop including such components and outputs the digital output angle φ.

  A digital output angle φ is input to the SIN ROM 26, and the SIN ROM 26 generates a sine value sin φ of the digital output angle φ and outputs it to the multiplier 21. Similarly, the COS ROM 27 generates a cosine value cos φ of the digital output angle φ from the digital output angle φ and outputs it to the multiplier 22.

The multiplier 21 multiplies the resolver signal S1 and sin φ and outputs the multiplied value to the subtractor 23. The multiplier 22 multiplies the resolver signal S2 and cos φ, and the multiplied value is subtracted by the subtractor 23. Output to. The subtracter 23 subtracts the output of the multiplier 21 from the output of the multiplier 22 and outputs the subtraction value to the synchronous detection circuit 24. The signal input from the subtractor 23 to the synchronous detection circuit 24 is
sin ωt (sin θ cos φ−cos θ sin φ)
= Sin ωt sin (θ−φ)
It becomes.

The synchronous detection circuit 24 synchronously detects this signal with reference to the excitation signal sin ωt input from the excitation signal generator 30, removes sin ωt, and controls the control deviation sin (θ−φ) that is the detection output. Output to the device 25. Since the controller 25 controls the digital output angle φ so that the control deviation sin (θ−φ) becomes zero, as a result, θ = φ, and the detected angle θ is converted into the digital output angle φ and output. As shown in FIG. 1, the transfer function of the controller 25 is represented by (K / s ² ) · {(τ ₁ s + 1) / (τ ₂ s + 1)}.

Here, when θ≈φ, the output of the synchronous detection circuit 24 is
sin (θ−φ) = θ−φ
The configuration of FIG. 1 can be simplified as shown in FIG.

  Next, the angle error characteristic of the resolver will be described.

  The angle error of the resolver is an error depending on the resolver angle. An example is shown in FIG. Note that the angle error actually has a frequency component that is an integral multiple of the resolver rotation speed, but here, for the sake of explanation, only the fundamental frequency component is shown in a simplified manner.

Here, an ideal resolver angle with no error is θ _t, and the angle error shown in FIG. 3 is θ _e . When the resolver rotates at the rotation speed Vrps, the detection angle θ of the resolver is
θ _t = 360 × V × t (t: time [s])
θ _e = sin θ _t
θ = θ _t + θ _e
It becomes.

  The following describes how the output of the RD converter 20 ′ becomes when this θ is input to the RD converter 20 ′ shown in FIG. 2.

The gain constant K, the first time constant τ ₁ , and the second time constant τ ₂ of the transfer function of the controller 25 in FIG.
K = 2 × 10 ⁶
τ ₁ = 1 × 10 ⁻³
τ ₂ = 1 × 10 ⁻⁴
Then, the characteristics of the RD converter 20 ′ are as shown in FIG.

A response when an ideal resolver angle θ _t having no error is input to the RD converter 20 ′ will be described.

Since the characteristic of the RD converter 20 ′ is a secondary system, when the rotational speed V is constant, the difference between the resolver angle θ _t and the output angle φ after a certain time is zero. FIG. 5 shows the response between the resolver angle θ _t and the output angle φ of the RD converter 20 ′ at the resolver rotation speed of 1000 rps, and the angular error (φ−θ _t ) at that time.

Next, the response will be described when the input angle error theta _e in the RD converter 20 '.

θ _e is represented by θ _e = sin θ _t , and periodically varies. Therefore, output characteristics vary depending on the input frequency. When the resolver is rotated at 1000 rps, the signal is 1000 Hz. When this signal is input to the RD converter 20 ′, the amplitude is 0.3 times the phase shown in FIG. 4 and the phase is delayed by 117 °. FIG. 6 shows responses when the resolver rotational speed is 10 rps and 1000 rps. It can be seen that the output angle error characteristic output from the RD converter 20 ′ differs depending on the difference in the rotational speed of the resolver.

As described above, when the detected angle θ of the resolver is input to the RD converter, the output angle φ of the RD converter varies depending on the rotational speed of the resolver by adding the characteristics of the RD converter to θ _e that is the angle error of the resolver. To do. When the output angle phi of the RD converter, the error due to the angle error of the resolver and phi _e, an ideal detection angle is no error was phi _t,
φ = φ _t + φ _e
And φ _e has a rotational speed dependency.

  In the method for correcting the angle error of the resolver described in the above-mentioned Patent Document 1, since the output angle of the RD converter is corrected, the angle error that varies depending on the rotational speed of the resolver cannot be dealt with. Assuming that the RD converter having the characteristics shown in FIG. 4 is used, the angle error is calculated in accordance with the low speed rotation (for example, 10 rps), and correction data is created, the high speed rotation (for example, 1000 rps) is performed as shown in FIG. Then, an error will remain.

  Examples of the present invention will be described below.

  FIG. 8 shows the configuration of an embodiment of an RD converter equipped with an angle correction circuit according to the present invention, together with a resolver and an excitation signal generator. The parts corresponding to those in FIG. The detailed explanation is omitted.

  In this example, the angle calculation circuit 40 and the angle correction circuit 50 corresponding to the RD converter 20 shown in FIG. 1 constitute an RD converter. The angle correction circuit 50 includes a correction data unit 51, a filter 52, and a subtracter 53.

  As in the case of FIG. 2, the angle calculation circuit 40 is simplified as sin (θ−φ) = θ−φ when θ≈φ as shown in FIG. 9A, and the configuration shown in FIG. 9A is further modified. Then, the configuration shown in FIG. 9B is obtained.

The transfer function of the angle calculation circuit 40 ″ shown in FIG. 9B is as shown in FIG.
K (τ ₁ s + 1) / (τ ₂ s ³ + s ² + Kτ ₁ s + K)
The filter 52 of the angle correction circuit 50 has the same transfer function as this transfer function. That is, the filter 52 has the characteristics of the angle calculation loop of the angle calculation circuit 40. In the above transfer function, s is a Laplace operator, K is a gain constant, τ ₁ is a first time constant, and τ ₂ is a second time constant.

  On the other hand, a memory (RAM or ROM) is used for the correction data section 51, and angle error data of the resolver 10 is recorded as correction data.

The digital output angle calculated by the angle calculating circuit 40 phi are input to the correction data part 51, the correction data part 51 outputs the angle error theta _e of the resolver 10 for the digital output angle phi as correction data. This correction data has the same rotational speed as that of the resolver 10.

The correction data is input to the filter 52, and the characteristics of the angle calculation loop of the angle calculation circuit 40 are given by the filter 52. That is, the angle error θ _e of the resolver 10 passes through the angle calculation circuit 40 and has a rotation speed dependency, and has a constant value with respect to the angle and the same rotation speed as that of the resolver 10. The angle error θ _e that is correction data passes through the filter 52 and becomes an angle error corresponding to the rotation speed, that is, φ _e .

The output of the filter 52 and the digital output angle φ of the angle calculation circuit 40 are input to a subtractor 53, which subtracts the output of the filter from the digital output angle φ. The output φ ′ of the subtractor 53 is
φ '= φ-φ _e
= Φ _t + φ _e −φ _e
= Φ _t
Next, without depending on the rotational speed, it can be obtained accurately corrected to remove the angular error theta _e of the resolver 10 angle phi '.

Figure 10 is when the resolver 10 is like having a angular error theta _e of -1 ° ~ + 1 ° during one revolution, without Ali error correcting an output angle error of the RD converter, i.e. the angle correction circuit as described above FIG. 10A shows a response when the resolver rotational speed is 10 rps, and FIG. 10B shows a response when the resolver rotational speed is 1000 rps.

These views 10A, as is apparent from B, according to the RD converter having the angle correction circuit 50 according to the present invention, favorably corrected regardless of the rotation speed, due to the angle error theta _e of the resolver 10 outputs the angle error can do.

  Hereinafter, a method of generating correction data (angle error data of the resolver 10) recorded in the correction data unit 51 will be described.

  As shown in FIG. 11, an angle sensor 60 such as a rotary encoder serving as an angle reference is attached to the rotation axis of the resolver 10, and an output of the angle sensor 60 and a digital output angle φ of the angle calculation circuit 40 are corrected data generation device 70. To enter. The resolver 10 is rotated at a low speed (about 1 rps), and the difference between the output of the angle sensor 60 and the digital output angle φ at that time is taken to generate angle error data of the resolver 10 for one rotation.

When the acquisition of the angle error data is completed, the angle error data is written into the correction data unit 51 by the correction data writing device 80. The correction data unit 51 stores the angle error data in the memory. The address input of the memory and the angle input by the data output angle error output, the correction data part 51 the angular error theta _e for the digital output angle φ inputted extracted from the memory and outputs it as correction data. The angle error data stored in the memory is represented by θ _e0 to θ _en , and n = 2 ¹² −1 if the angle calculation circuit 40 has a 12-bit resolution.

  During actual operation, the angle sensor 60, the correction data generation device 70, and the correction data writing device 80 shown in FIG. 11 are not necessary, and the corrected angle φ ′ in which the angle error of the resolver 10 is corrected is output from the angle correction circuit 50. The

  When RAM is used for the correction data unit 51, since no data is input when the power is turned on, the angle error data acquired in advance by the correction data generation device 70 and recorded in the external memory is written in the correction data. Write by device 80. At this time, if there are individual differences in the angle error characteristics of the resolver, it is desirable to write the necessary ones from the previously obtained angle error data patterns in the RAM. When the recombination frequency of the resolver is low, correction data may be rewritten only when necessary using an EEPROM. If the angle error characteristic is constant, it may be configured as a ROM, and the memory should be selected according to the operating environment.

  As described above, according to the angle correction circuit of the present invention, it is possible to satisfactorily correct the angle error that fluctuates depending on the rotational speed of the resolver, and the RD converter is configured by adding this angle correction circuit to the angle calculation circuit. Thus, an RD converter that outputs a highly accurate angle can be obtained.

  Further, by providing such an RD converter, a resolver, and an excitation signal generator, an angle detection device that can accurately detect the rotation angle of the motor can be configured.

Claims (5)

An angle correction circuit that is added to an angle calculation circuit that converts a detection angle θ of a resolver signal output from a resolver of one-phase excitation and two-phase output into a digital output angle φ,
A correction data unit that receives the digital output angle φ and outputs the angle error of the resolver with respect to the digital output angle φ as correction data;
A filter that has the same characteristics as the transfer function of the angle calculation circuit and that receives the correction data;
An angle correction circuit comprising: a subtracter that subtracts the output of the filter from the digital output angle φ to output a corrected angle. The angle correction circuit according to claim 1,
The angle correction circuit, wherein the correction data section stores an angle error of the resolver in a memory, reads out the angle error with respect to the input digital output angle φ from the memory, and outputs it as the correction data. The angle correction circuit according to claim 1 or 2,
The transfer function of the filter is
K (τ ₁ s + 1) / (τ ₂ s ³ + s ² + Kτ ₁ s + K)
Where s: Laplace operator
K: Gain constant
τ ₁ : first time constant
τ ₂ : An angle correction circuit that is a second time constant. An angle calculation circuit for converting a detection angle θ of a resolver signal output from a resolver of one-phase excitation and two-phase output into a digital output angle φ;
An RD converter comprising the angle correction circuit according to claim 1. 1-phase excitation and 2-phase output resolver,
An RD converter according to claim 4;
An angle detection apparatus comprising: an excitation signal generator that supplies an excitation signal to the resolver and the RD converter.

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