JPH11160099A - Rotational position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the operational accuracy of an R-D (resolver-digital) converter by suppressing fluctuation of voltage signal between two-phase outputs of a resolver. SOLUTION: A rotational position detector comprises a single phase excitation two-phase output type resolver 1, and an R-D converter 3 for converting the analog output signal therefrom into a digital signal wherein a circuit A for regulating the maximum amplitude of two-phase output voltage uniformly is provided between the resolver 1 and the R-D converter 3. The regulating circuit A comprises variable resistors 41-44, 51-54 for determining the input/ output ratio thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational position detecting device, and more particularly to a resolver digital output.
It relates to a circuit input to a converter.

[0002]

2. Description of the Related Art There is a resolver as a sensor capable of detecting the rotational position of the shaft of various devices by an absolute angle. As shown in FIG. 3, a rotational position detection device using such a resolver includes a resolver a as a sensing unit that outputs an analog signal,
A resolver-to-digital converter (hereinafter referred to as R-converter) as an electric circuit unit that converts and processes an analog signal output from the analog signal into a digital signal that can be interfaced to a CPU.
B).

In general, a resolver includes one rotor and two stators. As shown in FIG. 4, a V.sin is wound around a winding of the rotor by an excitation circuit c shown in FIG.
When the signal ωt is excited, a signal V ₁ = V · sin ωt · sin θ V ₂ = V · sin ωt · cos θ is obtained as an output using the shaft angle θ as a parameter on the two windings of the stator. Input to D converter.

As shown in FIG. 4, the RD converter has a multiplication type DA converter as a main internal configuration.
It has a rectifier, an integrator, a voltage controlled oscillator (VCO) and an up / down counter. In this RD converter, when the digital angle φ generated by the up / down counter is used as an input of the cosine DA converter and V ₁ is used as a reference input, a signal of V · sinωt · sin θ · cos φ is obtained. Similarly, on the sine DA converter side, a signal of V · sinωt · cosθ · sinφ is obtained. The difference between these two signals is taken by an error amplifier at the next stage, and the signals are summarized as follows.
nφ). Where sinωt is an AC signal, s
in (θ-φ) is a DC signal. The rectifier then demodulates this signal using the same signal as the signal excited by the resolver. As a result, only a signal proportional to sin (θ−φ) can be obtained. This DC signal passes through the integrator and is input to the VCO, and a pulse is sent from the VCO to the up / down counter. This operation is continued until the state of sin (θ−φ) → 0. When this value is close to 0, θ-
φ → 0. When this operation is completed, θ = φ, and the input angle θ is obtained as the digital angle φ.

In the control of a motor which needs to detect a rotational position, a rotational position sensor is used as shown in FIGS.
When using a resolver of the one-phase excitation two-phase output method as shown in (1), the accuracy of the voltage signal of the two-phase output input from the resolver a to the RD converter b has a great influence on the rotational position detection accuracy. Therefore, in the conventional rotational position detecting device, a mechanism (for example, a voltage dividing circuit) for matching the output voltage from the resolver a to the input specification of the R-D converter b is provided in a portion d surrounded by a dotted frame in FIG. And providing a common-mode noise removing mechanism (for example, a differential input circuit).

[0006]

However, in the above-mentioned conventional mechanism, although high accuracy is required for elements such as resistors used in itself, the two-phase output unavoidable in the resolver a itself (unresolved). The balance does not remove the error given to the calculation processing result by the R-D converter b, and is not useful for improving the rotational position detection accuracy of the entire system. Therefore, even if the above-described mechanism is used for a combination of a resolver and an R-D converter having an essentially high output accuracy, it is difficult to precisely control the electric motor by detecting the rotational position with high accuracy.

Therefore, the present invention eliminates the variation of the voltage signal between the two-phase outputs of the resolver with a simple configuration, thereby reducing the R signal.
-Effectively use the arithmetic processing function by the D converter,
A first object is to provide a rotational position detecting device capable of improving the detection accuracy of the entire system.

A second object of the present invention is to provide a specific means for removing the variation of the voltage signal between the two-phase outputs.

[0009]

In order to achieve the first object, the present invention provides a resolver of a one-phase excitation two-phase output type, and a resolver-digital converter for converting an analog signal output from the resolver into a digital signal. .In a rotational position detecting device comprising a converter, the resolver and the resolver
An adjusting circuit for uniformly adjusting the maximum amplitude of the two-phase output voltage input from the resolver to the resolver-digital converter is provided between the digital converter and the digital converter.

Further, in order to achieve the second object, the adjustment circuit is provided with an adjustment resistor for determining an input / output ratio of the adjustment circuit.

[0011]

According to the first aspect of the present invention, such a configuration is adopted.
According to the present invention, the maximum amplitude (maximum value) of each of the two-phase voltages output according to the rotational position of the resolver is different from that of the conventional voltage dividing circuit which adjusts the gain of each of the two phases. Can be adjusted by the adjustment circuit to make them even, so that the variation between resolver two-phase output voltages is absorbed and the influence of the adjustment circuit is not affected, improving the rotational position detection accuracy as a system. It is possible to do. Therefore, when this device is used for controlling the electric motor, the electric motor can be optimally controlled with high accuracy. In particular, suppressing variation in motor output characteristics leads to improvement in performance quality.
In addition, high-precision rotation position detection enables stable motor control up to high rotation, making it possible to make full use of the output characteristics of the motor. This also contributes to downsizing in designing a motor to satisfy output characteristics. Furthermore, since structural errors due to uneven winding of the resolver can be adjusted, the required structural accuracy of the resolver can be reduced.

Next, according to the configuration of the second aspect, it is only necessary to tune the adjustment resistance of the adjustment circuit to adjust the maximum amplitude of each of the two-phase voltages and make them equal to each other. With a simple configuration,
It leads to cost reduction.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a system configuration of a rotational position detecting device according to the embodiment. In this device, a resolver 1 is a known type in which a single-phase winding is excited at a predetermined frequency by an excitation circuit 2 and a sine (sin) wave signal and a cosine (cos) wave signal are output from the other two-phase windings. The R-D converter 3 is also formed of a known device composed of an integrated circuit element that performs an arithmetic process on the two signals and outputs a predetermined digital signal.

According to the present invention, an adjusting circuit A constituting a differential amplifier is interposed in each of the sine wave signal line 4 and the cosine wave signal line 5 of the resolver 1. The adjustment circuit A includes operational amplifiers (operational amplifiers) 40 and 50 and four variable resistors 41 to 44 and 51 to 54 for the signal lines 4 and 5, respectively. Input terminals are connected to respective output windings of the resolver 1 via variable resistors 41, 43, 51, 53, and output terminals of the operational amplifiers 40, 50 are connected to input terminals of the R-D converter 3. Further, a variable resistor 4 for adjusting the amount of feedback is provided between the output terminals of the operational amplifiers 40 and 50 and one of the input terminals.
2 and 52, and the other input terminals of the operational amplifiers 40 and 50 are grounded via variable resistors 44 and 54. In the drawing, reference numeral 6 denotes a reference signal line for inputting a reference signal of the excitation voltage to the RD converter 3.

In the device having such a configuration, the sine wave signal (V _sin ) and the cosine wave signal (V _sin ) as shown in FIG. V _cos ) is output. FIG. 2 shows a two-phase voltage waveform of the input level of the RD converter, that is, a state at a resolver rotation angle of 360 ° of V _sin · V _cos (excitation waveform is arbitrary). Based on the relationship between the two signals, the sine wave signal (V _sin ) is 0 and the cosine wave signal (V _cos ) is calculated and processed by the RD converter 3 as shown by a circled arrow at the bottom of the figure. Is maximum (indicated by an upward arrow in the figure), sin
When the wave signal (V _sin ) is maximum and the cos wave signal (V _cos ) is 0, 90 ° (indicated by a right-pointing arrow in the figure), the sin wave signal (V _sin ) is 0, and the cos wave signal (V 180 ° (indicated by a downward arrow in the figure) when the _cos ) is the minimum, the sin wave signal (V _sin ) is the minimum and c
When the os-wave signal (V _cos ) is 0, it is determined to be 270 ° (indicated by a left-pointing arrow in the figure).

Next, a description will be given of a method of adjusting the adjustment circuit in the one-phase excitation two-phase output resolver having a shaft angle multiplier of 1. In this case, resolver electrical angle (rotation angle) 0 ° or the maximum value of V _{c os} output voltage at 180 ° with (V _cmax), similarly the maximum value of V _sin output voltage in the electrical angle of 90 ° or 270 ° (V _smax 1), the resistance R ₁ , R ₂ or r ₁ , r ₂ of each variable resistor in FIG. 1 is adjusted for each phase. Here, the excitation voltage V
The _in, the two-phase output voltage from V _in = E · sinωt resolver, each _{V sin = k · E · sinωt} · sinθ V cos = k · E · sinωt · cosθ ( Here, k resolver transformation ratio, the θ Resolver rotation angle)
Then, the variation due to the winding unevenness of the resolver alone becomes the variation of the transformation ratio (k) of each of the two-phase outputs. Therefore, if each transformation ratio is k _s and k _c , V _sin ′ = k _s E · sinωt · sinθ V _cos ' = k _c · E · sinωt · cosθ

[0017] Thus, two-phase input voltage at R-D converter terminal level shown in FIG. _{2, V sin R / D = r} 1 / R 1 · k s · E · sinωt ·
sin θ V _{cos R / D} = r ₂ / R ₂ · k _c · E · sin ωt ·
cos θ. Here, in order to make the maximum amplitude of each phase voltage equal, r ₁ or R ₁ , r ₂ or R ₂ may be adjusted so that the following relationship is satisfied. R ₁ · r ₂ : r ₁ · R ₂ = k _s : k _c By doing so, a two-phase analog with the same maximum amplitude and capable of accurately processing the resolver output signal at an arbitrary position by the R-D converter It can be a signal.

As described in detail above, according to this rotational position detecting device, the output ratio is changed to an arbitrary value according to the specification of the R-D converter 3 by adjusting the variable resistance in the differential amplifier, and the resolver The two-phase output can be balanced with high accuracy, including the voltage error of the two-phase output signal output from 1 and the error of the resistance element of the differential amplifier circuit. Thereby, the detection accuracy as the rotational position detecting device can be improved. In addition, since a virtual ground point is separately formed in the differential amplifier circuit, the ground line of each of the two-phase output is set to R
This eliminates the need to guide the signal to the −D converter 3, so that a ground line for signal output is not looped in the RD converter 3, thereby preventing a detection error due to a ground loop. Further, external noise can be canceled by a differential circuit configuration. in addition,
Since errors in the structure of the resolver (such as uneven windings) can be adjusted by this circuit, the required accuracy in the structure of the resolver can be reduced.

As described above, the present invention has been described in detail based on one embodiment. However, the present invention is not limited to the disclosed contents of the above embodiment, and various details can be set within the scope of the claims. Needless to say, the present invention can be implemented by changing the specific configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of a rotational position detecting device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a two-phase voltage waveform of an RD converter input level and a rotational position in the device.

FIG. 3 is a block diagram showing a system configuration of a conventional rotational position detecting device.

FIG. 4 is a circuit diagram showing details of a conventional rotational position detecting device.

[Explanation of symbols]

Reference Signs List 1 resolver 3 R-D converter (resolver-digital converter) A adjustment circuit 41-44 variable resistor (adjustment resistor) 51-54 variable resistor (adjustment resistor)

Claims (2)

[Claims] 1. A rotational position detecting device comprising: a resolver of a one-phase excitation two-phase output type; and a resolver-digital converter for converting an analog signal output from the resolver into a digital signal, wherein the resolver and the resolver-digital converter A rotational position detecting device, further comprising an adjusting circuit for uniformly adjusting the maximum amplitude of a two-phase output voltage input from the resolver to the resolver-digital converter, between the converter and the converter. 2. The rotational position detection device according to claim 1, wherein the adjustment circuit includes an adjustment resistor that determines an input / output ratio of the adjustment circuit.