JP2008199792A - Sensor signal processor and motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow high-accurcy measurements at low cost, using a sensor that uses a bridge circuit. <P>SOLUTION: The motor controller 1 comprises two sensors 3, 4, amplifying means 5, 6 corresponding to the sensors, and a motor control means 7. The motor control means 7 comprises a switch control part 35 that turns on/off a transistor 16, provided to the grounding side of the sensors 3, 4, and a timer 34. The timer 34 outputs a signal to the signal control part 35 as specified time interval elapses, and makes the transistor 16 turn off for a prescribed time interval. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sensor signal processing device that processes a sensor signal, and a motor control device that includes the sensor signal processing device and controls driving of the motor.

As a type of sensor that outputs an electrical signal in response to a pressure change, a sensor in which a Wheatstone bridge circuit is formed by four strain gauges is known. For example, in the bridge circuit disclosed in Patent Document 1, a signal is extracted from an intermediate position between the voltage source and the ground terminal. Each strain gauge is formed under the same conditions and has the same electrical and physical properties. For example, the strain gauge is formed by applying a semiconductor film forming technique to a diaphragm substrate. The signal taken out from the bridge circuit is input to an amplifying means comprising a differential amplifier and amplified to a predetermined signal level.
Japanese Utility Model Publication No. 6-25224

However, in the conventional configuration, if there are variations in the resistance elements of the differential amplifier circuit, the signal fluctuates and it may be difficult to perform highly accurate measurement. The cause of variations in the resistance elements of the differential amplifier circuit is that an offset error, a gain error, etc. occur when the temperature changes due to variations in the resistance temperature coefficient. In particular, the offset error has a large effect when the amplification factor is designed to be high, so when amplifying a minute signal, it is necessary to use a resistance element having a low resistance temperature coefficient. The resistance element was expensive.
The present invention has been made in view of such circumstances, and a main object of the present invention is to enable high-precision measurement at a low cost with a sensor using a bridge circuit.

The invention according to claim 1 of the present invention for solving the above-mentioned problem is constituted by a bridge circuit including a resistor, and in use, the first input terminal is connected to a constant voltage power source, the second input terminal is grounded, A sensor signal processing apparatus that has a sensor that outputs a signal from two output terminals, and that processes an output signal from the sensor, the amplifier being connected to the output terminal and amplifying the signal output from the sensor And a signal processing unit for processing the amplified signal amplified by the amplifying means, and at least one between the first output terminal and the constant voltage power source or between the second input terminal and the ground. A switch capable of opening and closing is provided, and the signal processing unit includes a switch control unit that controls opening and closing of the switch, and a timing control that generates a timing at which the switch control unit opens the switch And a storage unit that stores an amplification signal when the switch is opened, and an arithmetic unit that corrects the amplification signal when the switch is closed using the amplification signal stored in the storage unit. It was set as the sensor signal processing apparatus.
This sensor signal processing device opens the switch at the timing generated by the timing control unit. Since the current flowing through the sensor becomes zero, the amplified signal at this time becomes an offset error between the sensor and the amplifying means. Therefore, a correct sensor signal can be obtained by correcting the amplified signal obtained when the switch is closed again with an offset error signal.

According to a second aspect of the present invention, in the sensor signal processing device according to the first aspect, the timing control unit is a timer that outputs a signal for opening the switch to the switch control unit every predetermined time. And
This sensor signal processing device corrects the sensor signal by controlling the opening and closing of the switch at regular intervals using a timer.

According to a third aspect of the present invention, in the sensor signal processing device according to the first aspect, the timing control unit detects a voltage value of the constant voltage power source, and the voltage value reaches a predetermined value when the voltage value reaches a predetermined value. It is a voltage detection part which outputs the signal which opens a switch to the said switch control part, It is characterized by the above-mentioned.
This sensor signal processing device corrects the sensor signal by controlling the switch using the voltage value as a trigger.

According to a fourth aspect of the present invention, in the sensor signal processing device according to any one of the first to third aspects, the sensor has two sensors, and each of the sensors uses four magnetoresistive elements. A bridge circuit is formed, and the other sensor is arranged to be rotated by 45 ° with respect to one of the sensors.
This sensor signal processing device outputs signals having different phases from a pair of sensors. When processing a pair of signals having different phases, a sensor signal with high accuracy can be obtained by performing correction.

According to a fifth aspect of the present invention, in the sensor signal processing device according to any one of the first to fourth aspects, the switch is provided on the ground side of the sensor.
In this sensor signal processing device, when the switch is closed, the current flowing through the sensor becomes substantially zero, so that correction becomes easy.

According to a sixth aspect of the present invention, there is provided a motor control device for controlling drive of a motor, wherein the motor drive unit switches a current to be supplied to the motor, and is provided for detecting the rotation of the motor. A pair of sensors forming a circuit and the first input terminal of each of the pair of sensors and a constant voltage power source or at least one of the second input terminal and the ground can be controlled to be opened and closed. A switch connected to each output terminal of the pair of sensors, amplifying means for amplifying a signal, a switch control unit for controlling opening and closing of the switch, and a timing at which the switch control unit opens the switch A timing control unit, a storage unit that stores an amplification signal when the switch is opened, and an amplification signal that is stored when the switch is closed are stored in the storage unit. A motor control device comprising: a calculation unit that corrects using the amplified signal that has been corrected; and a motor control unit that outputs a motor drive signal to the motor drive unit based on the signal corrected by the calculation unit It was.
The motor control device closes the switch at the timing generated by the timing control unit, and corrects the sensor signal using the signal at this time. By performing the correction, information on the rotational position of the motor can be obtained with high accuracy.

According to a seventh aspect of the present invention, in the motor control device according to the sixth aspect, the timing control unit is a timer that outputs a signal for opening the switch to the switch control unit every predetermined time. Features.
This motor control device corrects the sensor signal at regular intervals using a timer to detect the rotational position of the motor with high accuracy.

According to an eighth aspect of the present invention, in the motor control device according to the sixth aspect, the timing control unit detects a voltage value of the constant voltage power source, and the voltage value reaches a predetermined value. It is a voltage detection part which outputs the signal which opens a switch to the said switch control part, It is characterized by the above-mentioned.
The motor control device corrects the sensor signal using the voltage value as a trigger. For example, correction is always performed when the power is turned on.

In the sensor signal processing apparatus according to the present invention, it is possible to easily detect the offset error of the sensor and the amplification means. Since the offset error can be corrected, a correct sensor signal can be obtained even if an inexpensive element is used for the amplifying means, and the cost of the apparatus can be reduced.
In the sensor signal processing device according to the present invention, the rotational position of the motor can be correctly detected by performing offset correction at a predetermined timing. The rotation control of the motor can be performed with high accuracy.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Note that the same reference numerals are given to the same components in each embodiment. In addition, overlapping explanation is omitted.

(First embodiment)
FIG. 1 shows a schematic configuration of a motor control device including a sensor signal processing device. The motor control device 1 includes two sensors 3 and 4 disposed close to the motor 2, two amplifying means 5 and 6 that receive respective signals from the sensors 3 and 4, and each amplifying means 5 and 6. Motor control means 7 for generating a motor drive signal for driving the motor 2 based on the amplified signal output from the motor, and a motor drive unit 8 for controlling energization to the motor.

The two sensors 3 and 4 are magnetoresistive sensors each composed of a Wheatstone bridge using four magnetoresistive elements R1 to R4, and are arranged close to a magnet fixed to a rotating shaft (not shown) of the motor 2. ing. The sensors 3 and 4 are arranged with a 45 ° phase shift as viewed from the rotation axis of the motor 2. Each sensor 3, 4 has four terminals 11, 12, 13, 14 corresponding to the connection locations of the magnetoresistive elements R 1 to R 4. The first input terminal 11 of the first sensor 3 is connected to a constant voltage power supply 15. The second input terminal 12 is grounded via a transistor 16 that is a switching element. First and second output terminals 13 and 14 provided between the first input terminal 11 and the second input terminal 12 are connected to the first amplifying means 5.
In the second sensor 4, each of the first and second input terminals 11 and 12 is connected to the constant voltage power supply 15 and the transistor 16. The first and second output terminals 13 and 14 are connected to the second amplifying means 6.

  The first amplifying means 5 is composed of a differential amplifier circuit. In the differential amplifier circuit, a plurality of resistors R11 to R14 and an operational amplifier 17 are used. The output of the first amplifying unit 5 is connected to the input unit 31 of the motor control unit 7. The second amplifying unit 6 has the same configuration and is connected to the input unit 31 of the motor control unit 7.

  The motor control means 7 includes a signal processing unit 21 that processes sensor signals and a motor control unit 22 that generates drive signals. The signal processing unit 21 includes an input unit 31, a storage unit 32 including a memory, a calculation unit 33 including a CPU (Central Processing Unit), a timer 34 serving as a timing control unit, and a switch control unit 35. . The switch control unit 35 is connected to the transistor 16 and has a function of switching opening and closing of the transistor 16 (hereinafter referred to as ON and OFF). The calculation unit 33 is connected to the motor control unit 22 so as to be able to output a sensor signal described later.

The operation in this embodiment will be described.
First, processing for performing offset correction of the sensors 3 and 4 and the amplification means 5 and 6 will be described with reference to the flowchart of FIG. The timer 34 generates a timer signal at a predetermined timing (Yes in step S101), and the switch control unit 35 turns off the transistor 16 (step S102). Examples of the timing at which the timer 34 outputs a timer signal include the timing immediately before the angle detection.
At this time, the current flowing through the Wheatstone bridge circuit of each of the sensors 3 and 4 becomes zero. Since the transistor 16 is provided on the ground side, the voltage input to each of the amplifying means 5 and 6 can be within the common-mode input voltage range. Therefore, if there is no offset error, the outputs of the amplifying means 5 and 6 should be the specified values (in this case, 2.5 V). When there is an offset error in each sensor 3, 4 or each amplifying means 5, 6, the output of each amplifying means 5, 6 is shifted by the amount of the offset error.

  Therefore, after waiting for a predetermined time (step S103), the amplified signals amplified by the amplification means 5 and 6 are taken in from the input unit 31 (step S104). Since the amplified signal at this time is a signal corresponding to the offset error as described above, this signal is stored in the storage unit 32 as a correction value (step S105). Thereafter, the switch control unit 35 turns on the transistor 16 (step S106). In order to stabilize the outputs of the sensors 3 and 4, after waiting for a predetermined time (step S107), a new amplified signal is taken in from the input unit 31 (step S108).

  The computing unit 33 computes the sensor signal by subtracting the correction value stored in the storage unit 32 from the current amplified signal fetched from the input unit 31 (step S109). The sensor signal that is the calculation result is output to the motor control unit 22 (step S110). And the motor control part 22 outputs a motor control signal to the motor drive part 8 based on a sensor signal (step S110). The motor control unit 22 specifies the rotational position of the motor 2 based on the sensor signal, and calculates excitation switching timing. Then, in accordance with the excitation switching timing, a motor control signal is output to the motor drive unit 8 to control power supply to the motor 2. The motor 2 rotates the rotor according to the current supplied from the motor drive unit 8.

In this embodiment, in a sensor signal processing apparatus having a pair of sensors 3 and 4, a pair of amplifying means 5 and 6, and a signal processing unit 21, the transistor 16 is turned off in accordance with the timing generated by the timer 34. Since the current flowing through 4 can be made zero, offset correction can be performed even during operation of the motor 2. Conventionally, offset correction must be performed after rotational control is performed so that the magnetic field applied to the magnetic resistance becomes zero, and control is difficult when two sensors having different phases are included. In this form, offset correction can be easily performed.
Since the offset correction can be performed including the amplifying means 5 and 6, even if the resistance temperature coefficients of the resistors R11 to R14 have a large variation, a sensor signal with a small error can be obtained. The amplifying means 5 and 6 can be constructed from inexpensive parts.
Since the sensor signal processing device is used for controlling the motor 2, the rotational position of the motor 2 can be detected with high accuracy.

  Here, a modification is shown in FIG. In addition to the transistor 16 connected to the second input terminal 12 of the sensors 3 and 4, a transistor 41 is also provided between the first input terminal 11 and the constant voltage power supply 15. The transistor 41 is a switching element capable of opening / closing control. Each of the transistors 16 and 41 is connected to the switch control unit 35 of the signal processing unit 21. When offset correction is performed, both the transistors 16 and 41 are turned OFF so that the current flowing through the bridge circuit of the sensors 3 and 4 is zero. Alternatively, only the transistor 41 on the constant voltage power supply 15 side may be turned off. Even in these cases, offset correction can be performed in the same manner as described above.

(Second Embodiment)
FIG. 4 shows a schematic configuration of a motor control device including a sensor signal processing device. In the motor control device 51, the signal processing unit 21 includes a voltage detection unit 52 instead of a timer. The voltage detection unit 52 is connected to the sensors 3 and 4 so as to detect the potential of the first input terminal 11 of the sensors 3 and 4, that is, the power supply voltage of the constant voltage power supply 15. In the signal processing unit 21, the input unit 31 and the switch control unit 35 are connected.

The operation of the motor control device 51 will be described with reference to the flowchart of FIG. When the power supply of the motor control device 51 is turned on and a voltage is applied from the constant voltage power supply 15 to the sensors 3 and 4, the voltage detection unit 52 detects the voltage value of the constant voltage power supply 15 (step S201).
When the voltage value of the constant voltage power supply 15 is detected, the switch control unit 35 turns off the transistor 16 for a predetermined time (step S202). When the current flowing through the Wheatstone bridge circuit of each sensor 3, 4 becomes zero and there is an offset error in each sensor 3, 4 or each amplifying means 5, 6, the output of each amplifying means 5, 6 is offset error. Shift a lot.

  After waiting for a predetermined time (step S203), the amplified signal is detected by the input unit 31 (step S204) and stored in the storage unit 32 (step S205). Thereafter, steps S205 to S211 are performed as a normal operation. Each of these steps S205 to S211 is the same as steps S105 to S111 in the first embodiment. The rotation of the motor 2 is controlled based on the motor control signal generated from the sensor signal.

In this embodiment, offset correction is performed each time the control device is turned on, so that the rotational position of the motor 2 can always be detected correctly.
As shown in FIG. 3, a transistor 41 may be connected to the constant voltage power supply 15 side as a switching element.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
For example, in the configuration of FIG. 3, depending on the configuration of the differential amplifier circuit, both the two transistors 16 and 41 may be turned off.
The switching element is not limited to a transistor as long as the switching control from the motor control means 7 is possible.
The timer 34 may output a command signal to the switch control unit 35 at a predetermined time interval regardless of the timing at which the angle is detected.
The application of the sensor signal processing device is not limited to motor control. For example, when the sensor signal processing device is used for detecting the distortion of an object, electric resistance elements are used for the sensors 3 and 4. In this case, the number of sensors 3 and 4 may be one, or three or more.

It is a block diagram which shows the structure of the motor control apparatus which concerns on embodiment of this invention. It is a flowchart which shows the process which shifts to normal operation | movement after performing offset correction | amendment for every predetermined time. It is a block diagram which shows the structure of the motor control apparatus in the case of having two switching elements. It is a block diagram which shows a structure provided with a voltage detection part. It is a flowchart which shows the process which shifts to normal operation | movement after offset correction is performed at the time of power-ON.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,51 Motor control apparatus 2 Motor 3, 4 Sensor 5, 6 Amplifying means 7 Motor control means 8 Motor drive part 11 1st input terminal 12 2nd input terminal 13 1st output terminal 14 2nd output terminal 15 Constant voltage power supply 16, 41 Transistor (switch)
21 Signal Processing Unit 22 Motor Control Unit 32 Storage Unit 33 Calculation Unit 34 Timer (Timing Control Unit)
35 Switch control unit 52 Voltage detection unit (timing control unit)

Claims (8)

A bridge circuit including a resistor, and in use, the first input terminal is connected to a constant voltage power source, the second input terminal is grounded, and a sensor that outputs signals from two output terminals is provided. A sensor signal processing device for processing the output signal of
Amplifying means connected to the output terminal and amplifying a signal output from the sensor;
A signal processing unit for processing the amplified signal amplified by the amplification means,
A switch capable of opening and closing is provided between at least one of the first output terminal and the constant voltage power source or between the second input terminal and the ground, and the signal processing unit controls opening and closing of the switch. A switch control unit; a timing control unit that generates a timing for the switch control unit to open the switch; a storage unit that stores an amplification signal when the switch is opened; and an amplification signal when the switch is closed. A sensor signal processing apparatus comprising: an arithmetic unit that performs correction using the amplified signal stored in the storage unit.   The sensor signal processing apparatus according to claim 1, wherein the timing control unit is a timer that outputs a signal for opening the switch to the switch control unit every predetermined time.   The timing control unit is a voltage detection unit that detects a voltage value of the constant voltage power supply and outputs a signal for opening the switch to the switch control unit when the voltage value reaches a predetermined value. The sensor signal processing device according to claim 1, wherein   There are two sensors, and each of the sensors forms a bridge circuit using four magnetoresistive elements, and the other sensor is rotated by 45 ° with respect to one of the sensors. The sensor signal processing device according to claim 1, wherein the sensor signal processing device is a sensor signal processing device.   5. The sensor signal processing device according to claim 1, wherein the switch is provided on a ground side of the sensor. 6. A motor control device for controlling drive of a motor,
A motor drive unit for switching a current to be supplied to the motor;
A pair of sensors provided to detect the rotational position of the motor and having a bridge circuit formed of magnetoresistive elements;
A switch that is provided between at least one of the pair of sensors and the first input terminal and the constant-voltage power supply, or between each of the second input terminal and the ground, and capable of opening and closing;
Amplifying means for amplifying a signal connected to each output terminal of the pair of sensors;
A switch control unit for controlling opening and closing of the switch;
A timing control unit that generates a timing at which the switch control unit opens the switch; and
A storage unit for storing an amplified signal when the switch is opened;
An arithmetic unit that corrects the amplified signal when the switch is closed using the amplified signal stored in the storage unit;
A motor control unit that outputs a motor drive signal to the motor drive unit based on the signal corrected by the calculation unit;
A motor control device comprising:   The motor control device according to claim 6, wherein the timing control unit is a timer that outputs a signal for opening the switch to the switch control unit every predetermined time.   The timing control unit is a voltage detection unit that detects a voltage value of the constant voltage power supply and outputs a signal for opening the switch to the switch control unit when the voltage value reaches a predetermined value. The motor control device according to claim 6, characterized in that:

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