JPH06323930A - Disurbing magnetic-field noise compensation device of magnetostrictive torque sensor - Google Patents

Abstract

PURPOSE:To remove a noise component from a torque output signal by a method wherein a disturbing magnetic field generated by the rotation of a motor or an electromagnetic brake and a noise generated in a detection coil by only the influence of the eccentricity of a torque transmission shaft are detected. CONSTITUTION:Signals from detection coils are input respectively to initial-stage amplifiers 201, 202, amplified signals are full-wave-rectified 203, 204, rectified signals are differentially amplified 205 and an amplified signal is then input to a differential amplifier circuit 209. On the other hand, a signal from a dummy detection coil is amplified by an initial-stage amplifier 206, an exciting frequency component is then removed by a notch filter 207, and an amplified signal is gain-regulated 208, and a gain-regulated signal is input to the differential amplifier circuit 209. Then, a noise component is removed from a torque signal by the differential amplifier circuit 209, and torque output signal is then output through a filter 210. That is to say, since a magnetostrictive film does not exist in a part in which the dummy coil has been installed, only an influence due to magnetic fields (an exciting magnetic field and a disturbing magnetic field by the rotation of a motor or the like) and due to eccentricity appears. Only the noise component is removed from the signal from the dummy detection coil, and the noise component is removed from the torque signal by the circuit 209.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compensating device for noise caused by a disturbance magnetic field of a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art An example of the structure of a conventional magnetostrictive torque sensor and the structure of a signal processing circuit are shown in FIGS. In FIG. 3, 301 is a torque transmission shaft, 302 and 303 are magnetostrictive films formed in the directions of 45 ° and −45 ° with respect to the axial direction, 304 is an exciting coil, and 305 is a detecting coil.
In FIG. 4, 401 and 402 are first-stage amplifiers, 403,
Reference numeral 404 is a full-wave rectification circuit, 405 is a differential amplifier, 406 is a filter circuit, 407 is an oscillation circuit, and 408 is a power amplifier. When torque is applied in the direction of the arrow in FIG. 3, a tensile stress is applied to the magnetostrictive film 302 and a compressive stress is applied to the magnetostrictive film 303, and the magnetic permeability of each magnetostrictive film changes in the opposite direction. By exciting the exciting coil of 304 of FIG. 3 by the exciting circuit composed of 407 and 408 of FIG.
The change in the magnetic permeability is detected by the change in the voltage of the detection coil, and is processed by the signal processing circuit in FIG. 4 to detect the torque in both the positive and negative directions.

[0003]

However, according to the conventional method,
When this torque sensor is incorporated in a motor or an electromagnetic brake, there is a problem that a disturbance magnetic field generated by the rotation of the motor or the electromagnetic brake causes noise in the torque output signal due to the eccentricity of the torque transmission shaft. The noise problem due to the disturbance magnetic field becomes more pronounced as the torque sensor is arranged closer to the motor and electromagnetic brake. Therefore, an object of the present invention is to remove this noise.

[0004]

In order to solve the above problems, the present invention relates to a magnetostrictive film formed at 45 ° with respect to the rotational axis direction of the torque transmission shaft and the rotational axis direction of the torque transmission shaft.
A magnetostrictive film formed at 45 °, two exciting coils and two detecting coils, a dummy exciting coil and a dummy detecting coil, and a full-wave rectifying circuit for full-wave rectifying the detecting coil signals on the magnetostrictive film. A first differential amplifier circuit that differentially amplifies an output signal of the full-wave rectifier circuit, a notch filter circuit that removes an excitation frequency component from a signal of the dummy detection coil, and a signal level of the dummy detection coil And a second differential amplifier circuit that takes a differential between the output signal of the gain adjustment circuit and the output signal of the first differential amplifier circuit.

[0005]

According to the above means, the noise generated in the detection coil can be detected only by the influence of the disturbance magnetic field generated by the rotation of the motor or the electromagnetic brake and the eccentricity of the torque transmission shaft without depending on the applied torque. As a result, only the noise component can be removed from the torque detection signal.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a torque sensor of the present invention, and FIG. 2 is a signal processing circuit block diagram thereof. In FIG. 1, 101
Is a torque transmission shaft, 102 and 103 are magnetostrictive films, 104 is an exciting coil, 105 is a detecting coil, 106 is a dummy exciting coil, and 107 is a dummy detecting coil. Although the detection coil is shown outside the exciting coil in the figure, the arrangement of the detecting coil and the exciting coil may be interchanged. In FIG. 2, 201 and 202 are first-stage amplifiers, 203 and 204 are full-wave rectifier circuits, 205 is a differential amplifier, 206 is a first-stage amplifier, 207 is a notch filter circuit, 208 is a gain adjusting circuit, and 209 is a differential amplifier. , 210 is a filter circuit, 2
Reference numeral 11 is an oscillation circuit, and 212 is a power amplifier for amplifying an output signal of the oscillation circuit into electric power. Next, the operation of the signal processing block diagram of FIG. 2 will be described. The signal of the detection coil 105 is
The signals are input to the first-stage amplifiers 201 and 202, respectively, and after signal amplification, full-wave rectification by the full-wave rectification circuits 203 and 204, differential amplification by the differential amplification circuit 205, and input to the next differential amplification circuit 209. Become a signal. On the other hand, the signal detected by the dummy detection coil 107 is input to the first-stage amplifier 206, the signal is amplified, the excitation frequency component is removed by the notch filter 207 having the excitation frequency f ₀ as the cutoff frequency, and then the gain adjustment circuit 208. To the input signal of the next differential amplifier circuit 209. The differential amplifier circuit 209 removes noise components from the torque signal, and then outputs the torque output signal through the filter circuit 210. When the torque sensor of FIG. 1 is incorporated in a motor or an electromagnetic brake, the detection coil on the magnetostrictive films 102 and 103 is affected by a magnetic field according to the rotation angle of the motor (or the electromagnetic brake) due to the rotation of the motor or the operation of the electromagnetic brake. Appears as noise. If the magnitudes of these disturbance magnetic fields are the same for the two detection coils, then 2
Although the influence of this magnetic field is canceled by the differential amplifier of 05, since the magnetostrictive films 102 and 103 have different distances from the magnetic field generation source, the influence of the disturbance magnetic field appearing in these detection coils causes an imbalance, and the differential It appears as noise even after amplification. Since the portion where the dummy coils 106 and 107 are installed does not have a magnetostrictive film, the dummy detection coil 107
Does not depend on the torque, and only the effects of the magnetic field and eccentricity appear. A notch filter 207 having an excitation frequency as a cutoff frequency is applied to the dummy detection coil signal,
The excitation frequency component is removed and only the signal corresponding to the magnetic field is extracted. Then, the gain adjusting circuit adjusts the signal level. The signal level is adjusted by rotating the motor or the electromagnetic brake so as to match the ripple level due to the magnetic field corresponding to the rotation angle appearing in the differential amplifier 205.
In practice, the motor or the electromagnetic brake may be operated, the final torque signal may be monitored, and adjustment may be made so that the ripple due to the magnetic field is eliminated. By taking the difference between the output of the differential amplifier 205 and the output of the gain adjusting circuit 208, the ripple due to the disturbance magnetic field is removed.

[0007]

As described above, according to the present invention, it is possible to obtain a torque signal that is not affected by the disturbance magnetic field generated by the motor or the electromagnetic brake.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a torque sensor showing an embodiment of the present invention.

FIG. 2 is a block diagram of a torque sensor signal processing circuit showing an embodiment of the present invention.

FIG. 3 Conventional example of torque sensor

FIG. 4 is a block diagram of a conventional torque sensor signal processing circuit.

[Explanation of symbols]

 101, 301 Torque transmission shaft 102, 103, 302, 303 Magnetostrictive film 104, 304 Excitation coil 105, 305 Detection coil 106 Dummy excitation coil 107 Dummy detection coil 201, 202, 206, 401, 402 First stage amplifier 203, 204, 403, 404 Full-wave rectifier circuit 205, 209, 405 Differential amplifier circuit (differential amplifier) 207 Notch filter circuit 208 Gain adjustment circuit 210, 406 Filter circuit 211, 407 Oscillation circuit 212, 408 Power amplifier

Continuation of the front page (72) Inventor Mitsuaki Ikeda No. 2 Kurosaki Shiroishi, Hachimannishi-ku, Kitakyushu City, Fukuoka Yasukawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A torque sensor for detecting a torque applied to a torque transmission shaft in a non-contact manner as a change in magnetic permeability of a magnetostrictive film, wherein the magnetostrictive film is formed at 45 ° with respect to the rotational axis direction of the torque transmission shaft. And a magnetostrictive film formed at −45 ° with respect to the rotational axis direction of the torque transmission shaft, two exciting coils and two detecting coils, a dummy exciting coil and a dummy detecting coil, and the detecting coil on the magnetostrictive film. A full-wave rectifier circuit for full-wave rectifying each signal, a first differential amplifier circuit for differentially amplifying an output signal of the full-wave rectifier circuit, and a notch filter for removing an excitation frequency component from the signal of the dummy detection coil A circuit, a gain adjustment circuit that adjusts the signal level of the dummy detection coil, and a second differential amplification circuit that takes a differential between the output signal of the gain adjustment circuit and the output signal of the first differential amplifier circuit. A disturbance magnetic field noise compensating device for a magnetostrictive torque sensor, comprising: a width circuit.