JPH04175626A - Method of compensating characteristic of torque sensor - Google Patents

Abstract

PURPOSE:To obtain the interchangeability among a plurality of sensors by reading characteristic data during operation of a sensor so as to compensate the characteristic of the sensor. CONSTITUTION:When an exciting power source 7 magnetically excites with a constant exciting voltage, detection coils 5, 5 produce a.c. voltage v1, v2 while filters 10, 10 produce d.c. voltages V1, V2. A difference V1- V2 between both outputs is produced on the output side of differential point 11. This difference V1 - V2 is delivered through an A/D converter 12 to a control circuit 13 which process the difference V1 - V2, and then delivers a torque detection signal. Characteristic data such as zero point, a sensitivity and an energizing current which have been measured during the manufacturing process of a torque sensor is written previously in EEPROM 6. When the circuit s energized, the control circuit 13 soon reads the characteristic data from the EEPROM 6 so as to compensate characteristics inherent to the torque sensor 1 in accordance with the characteristic data.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for compensating characteristics of a torque sensor.

Conventional Technology As a means for detecting the magnitude of torque applied to a torque transmission shaft, a magnetostrictive type)~lux sensor is used, for example, as disclosed in Patent No. 1.
It is known from the specification of No. 69326. This magnetostrictive torque sensor has a pair of magnetically anisotropic parts tilted in opposite directions on the outer peripheral surface of a torque transmission shaft, and an excitation coil and a pair of detection coils arranged around these magnetically anisotropic parts. Is it something that has been established or is it common? Such a magnetostrictive torque sensor is used after supplying an alternating current to the excitation coil to bring it into an excitation state.

When a torque is applied to the shaft in this state, the permeability of each magnetically anisotropic part changes depending on its personality.

This change in magnetic permeability appears as a change in the detection signal of each detection coil, so by taking the difference between the detection signals of these pair of detection coils, an output signal proportional to the magnitude of the applied torque can be obtained.

Invention or problem to be solved However, each torque sensor manufactured in a factory does not necessarily have the same characteristics, and in particular, their zero point, sensitivity, excitation current, etc. tend to vary, and the problem is that they are not compatible. be. Another problem is that the zero point and sensitivity characteristics change due to temperature changes during use, that is, the zero point and sensitivity temperature characteristics tend to be different for each torque sensor.

This lacks stability in quality when the torque sensor is mass-produced, and accurate torque measurement cannot be expected.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve these problems and to compensate for the characteristics of a torque sensor accurately and reliably.

Means for Solving the Problems In order to achieve the above object, the present invention forms a magnetically anisotropic part on the outer peripheral surface of a torque transmission shaft, and an excitation part and a detection part are arranged in correspondence with this magnetic anisotropic part. A magnetostrictive torque sensor is provided, and the detection unit outputs a signal corresponding to the magnitude of the torque applied to the torque transmission shaft. is stored in a storage medium within the sensor, and when the sensor is in operation, the characteristic data previously stored in the storage medium is read out, and the sensor characteristics are compensated based on the read characteristic data. .

In this way, information about the characteristics of each sensor is stored inside each individual sensor, and when the sensor is in operation, this information is read out to compensate for the sensor characteristics, allowing accurate torque measurement. It becomes possible.

Embodiment In FIG. 1, l is a magnetostrictive torque sensor and has a torque transmission shaft 2. In FIG. A pair of magnetic anisotropic portions 3, 3 are provided on the outer peripheral surface of the torque transmission shaft 2 and are inclined in opposite directions.
or is formed. An excitation coil 4 and a pair of detection coils 5, 5 provided corresponding to each magnetic anisotropic part 3, 3 are provided around the magnetic anisotropic parts 3, 3. Further, an EEFROM (ROM whose contents can be electrically erased) 6 is provided inside the torque sensor 1.

An AC excitation power source 7 is connected to the excitation coil 4 . Moreover, between these excitation coils 4 and excitation power supply 7,
An excitation current detection circuit 8 composed of a resistor or the like is provided to detect the excitation current flowing through the excitation coil 4.

Each detection coil 5, 5 includes a rectifier circuit 9.9 and a filter 1.
0.10 and each are connected in series, both filters 10
．． 10 is connected to the subtraction point 11.

The subtraction point 11 is connected to a digital control circuit 13 via an A/D converter 12. This control circuit 13
An excitation current detection circuit 8 is also connected to the A/D converter 14 . The control circuit 13 and the EEPROM 6 are connected to each other by a bus 16 including a clock line 15 and the like.

In such a configuration, when excitation is performed at a constant excitation voltage by the excitation power source 7, detection signals vl and v2 in the form of alternating current voltage appear in the detection coils 5, 5, and the filter 10.1
At 0, outputs v, y2 in the form of DC voltage appear. A difference of 100 outputs V+-v2 appears on the output side of the subtraction point 11. This difference VI V2 is sent to the control circuit 13 via the A/D converter 12, processed in the control circuit 13, and then outputted to the outside as a torque detection signal.

When the temperature of the torque sensor 1 changes, the excitation current of the excitation coil 4 changes accordingly.

This change in the excitation current is detected by the excitation current detection circuit 8, and a voltage output as a detection result is supplied to the control circuit 13 via the A/D converter 14.

When no torque is applied to the shaft 2, that is, at a zero point, the value of the torque detection signal must be zero. If the torque detection signal value is not zero,
We have to compensate so that it's either this or Cero. Further, when a constant value of torque is applied to the shaft 2, accurate torque measurement cannot be performed unless the value of the torque detection signal is always constant. In other words, the sensitivity of the torque sensor must always be constant, and if it is not, it must be compensated so that it becomes a constant value.

As mentioned above, the zero point, sensitivity, and excitation current of a torque sensor are not constant due to manufacturing errors or other causes, and it is common that they are not compatible. Therefore,
In order to be able to provide compatibility between each lux sensor, its characteristics are measured during manufacture of the torque sensor.
Characteristic data of the zero point, sensitivity, and excitation current for the torque sensor 1 are written in the EEPROM 6 in advance.

It is also well known that the zero point and sensitivity of a torque sensor change as its temperature changes.

Therefore, the temperature characteristics of these zero points and the temperature characteristics of the sensitivity, which are unique to each torque sensor, are measured at the time of manufacturing the lux sensor 1, and their characteristic data are
6 is written.

The torque sensor 1 manufactured in this manner is connected to the circuit shown in FIG. 1 during use. Then, when the circuit power is turned on, the control circuit 13 or the EEPROM 6 is immediately turned on.
Characteristic data is read out from the torque sensor 1, and various characteristics specific to the torque sensor 1 are compensated for using the read characteristic data. By performing such compensation, it is possible to make each torque sensor 1 compatible, and measurement errors due to temperature changes during use can be prevented.

As mentioned above, when the temperature of the torque sensor 1 changes, the excitation current flowing through the excitation coil 4 changes accordingly. It is possible to detect the temperature of Alternatively, the temperature can also be detected by incorporating a temperature-sensitive resistor or thermistor into the torque sensor 1.

Specifically, compensation for various characteristics is performed using the following equations.

VT = new (Vl-V2) -Vcz) -VT
2 (T) Co-Kc, -KTs (T) Where, V is the torque output, vez is the zero point compatibility data, Kcs is the sensitivity compatibility data, V, , (T) is the zero point temperature characteristic compensation data ,K,,(T
'> is sensitivity temperature characteristic compensation data.

If the compatibility data of the excitation current of the torque sensor l is 1c, the zero point temperature characteristic compensation data VTZ(T) and the sensitivity temperature characteristic compensation data are 1. (T) is calculated from the sensor's excitation current (t, , -1c').

or EEPROM based on the (L, -1c) value
You can also start reading from 6 onwards.

EFFECTS OF THE INVENTION As described above, according to the present invention, various characteristics of the torque sensor are measured during manufacturing, the characteristic data is stored in a storage medium, and this characteristic data is read out when the sensor is in operation. Since the sensor characteristics are compensated by the sensor characteristics, it is possible to provide Lγ conversion between a plurality of sensors, and it is also possible to measure torque with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an example of a 1-lux measuring device for carrying out the method of the present invention. 1... Torque sensor, 6... EEPROM,
8... Excitation current detection circuit, 13... Control circuit. Agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. A magnetic anisotropic portion is formed on the outer circumferential surface of the torque transmission shaft, an excitation portion and a detection portion are provided corresponding to the magnetic anisotropy portion, and the torque is applied to the torque transmission shaft. In a magnetostrictive torque sensor in which a signal corresponding to the magnitude of the torque is output from the detection section, the characteristics of the sensor are measured at the time of manufacturing the sensor, and the characteristic data is stored in a storage medium within the sensor. A method for compensating characteristics of a torque sensor, comprising: reading characteristic data stored in advance in the storage medium when the sensor is in operation, and compensating the sensor characteristics based on the read characteristic data. . 2. The characteristic data stored in the storage medium includes zero point compatibility data, sensitivity compatibility data, excitation current compatibility data, zero point temperature characteristic compensation data, and sensitivity temperature characteristic compensation data. 2. The method of compensating characteristics of a torque sensor according to claim 1, wherein one or more of: