JP2002272178A - Apparatus for calculating motor speed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate motor speed, taking into consideration brush loss in an electric power steering apparatus, where steering auxiliary force is given to the steering system of an automobile and a vehicle. SOLUTION: The function data of a brush contact voltage drop to a motor circuit current are stored as a map, in a memory 30a in a brush loss correction section 30. The brush loss correction section 30 refers to the map data in the memory 30a and outputs a brush contact voltage drop, corresponding to an inputted motor circuit current. A voltage drop by motor circuit resistance obtained by a motor circuit resistance multiplication section 31 and that by brush contact obtained by the brush loss correction section 30 are subtracted from the voltage command value, and gain correction is made by a gain correction section 33, thus outputting the estimated value of the motor rotational speed (speed).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for calculating the number of rotations of a motor, and more particularly, to the number of rotations of a motor used in an electric power steering apparatus for applying a steering assist force to a steering system of an automobile or a vehicle. It relates to a calculating device.

[0002]

2. Description of the Related Art Generally, an electric power steering apparatus is configured as shown in FIG. In FIG. 3, a steering wheel 1 is provided with a first steering shaft 2.
a and the second steering shaft 2 b via the universal joint 3.

[0003] The second steering shaft 2b is
It is connected to a tie rod 6 of a steering wheel via a pinion 4 and a rack 5. Second steering shaft 2
A motor (b) is provided with a torque sensor 7 for detecting the steering torque of the steering wheel 1 and assisting the steering force of the steering wheel 1 (a DC motor having a brush).
8 is a second steering shaft 2 via a reduction gear 9.
b.

Reference numeral 10 denotes a target current command value obtained from the detected torque of the torque sensor 7, a detected current obtained from a current detector and a voltage detector (not shown), a detected voltage, and the like, and a motor 8 based on the target current command value. Is a controller that controls the current supplied to the controller, and is configured by, for example, a microcomputer.

[0005] The controller 10 and the motor 8
It is driven by a power supply of a battery 12 supplied via a relay 11 which is turned on by turning on a key switch of an ignition key.

In the above-mentioned electric power steering apparatus, in order to correct the target current command value of the motor 8, the motor rotation speed (rotation speed) is calculated from the motor current and the motor voltage.

The calculation of the motor rotation speed is performed by calculating the following formula in the controller 10: ω = {v− (R + sL) i} / K _E (v−Ri) / K _E (1) Had been

In the above equation (1), ω is the motor speed (N), v is the motor voltage, i is the motor current, R is the motor circuit resistance, s is the Laplace operator, L is the inductance,
K _E is a back electromotive force coefficient, since it is there is a response of the number H _Z in PS system, the high frequency component due to the inductance is ignored.

FIG. 4 is a block diagram showing a configuration for obtaining the motor rotation speed (rotation speed) from the above equation (1). FIG.
, 21 is a motor circuit resistance multiplying unit for multiplying the motor current (i) by the motor circuit resistance (internal resistance R). A subtraction unit 22 subtracts the output (Ri) of the motor circuit resistance multiplication unit 21 from the motor voltage (v).

Reference numeral 23 denotes an output (v-Ri) of the subtractor 22.
Is the inverse of the back electromotive force coefficient (1 / K_E) Multiplying factor
A multiplication unit, and an output ｛(v−Ri) of the coefficient multiplication unit 23
/ K _E｝ Is the motor rotation speed (rotation speed).

Conventionally, as disclosed in, for example, JP-A-8-113150, a motor current and a motor voltage are detected at a predetermined sampling period, and the detected values are substituted into a mathematical expression such as the above expression (1). Thus, the number of rotations of the motor is calculated.

[0012]

However, the conventional method of calculating the number of revolutions of the motor does not take into account the brush loss of the motor (the voltage drop due to the brush contact), so that the accuracy of calculating the number of revolutions of the motor when the current is small is low. There was a disadvantage of being low.

That is, as can be seen from the characteristic line of FIG. 5 showing the relationship between the motor circuit current and the motor voltage command value, the measured motor voltage value is smaller than the characteristic line based on Ohm's law of V = IR by the brush contact voltage drop. The value was shifted only by

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a motor rotation speed calculating device capable of obtaining an accurate motor rotation speed in consideration of a brush loss. .

[0015]

According to the present invention, there is provided an apparatus for calculating the number of revolutions of a motor, comprising: a current flowing through a motor having a brush; a voltage drop component caused by a circuit resistance of the motor; A motor rotation speed calculation device for calculating a rotation speed of a motor by calculating a deviation from an applied voltage, characterized by comprising a brush loss correction means for correcting a brush loss component of the deviation.

Further, the brush loss correction means stores function data of the brush contact voltage drop with respect to the motor current as a map.

The voltage applied to the motor uses a motor voltage command value.

The motor is a motor for applying a steering force to a steering mechanism.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to the electric power steering apparatus shown in FIG. In this embodiment, in order to obtain the motor rotation speed (rotation speed) by the controller 10 of the electric power steering apparatus, the above equation (1) is basically calculated. The voltage drop due to the contact is corrected by the brush loss correction unit 30 of FIG.

The memory 30a of the brush loss correction unit 30
2 stores function data of the brush contact voltage drop with respect to the motor circuit current as shown in FIG. The brush loss correction unit 30 outputs a brush contact voltage drop corresponding to the input motor circuit current with reference to the map data in the memory 30a.

Reference numeral 31 denotes a motor circuit resistance multiplying unit for multiplying the motor current by the motor circuit resistance. Reference numeral 32 denotes a subtraction unit that subtracts the output of the brush loss correction unit 30 and the output of the motor circuit resistance multiplication unit 31 from the motor voltage command value.

Reference numeral 33 denotes an output of the subtractor 32,
A gain correction unit having a filter function in addition to multiplying by the coefficient 1 / K _E (gain) described in the above equation (1). The output of the gain correction unit 33 is used as an estimated motor rotation speed (rotation speed). Is used for correcting the target current command value of the motor described above.

The filter function of the gain correction unit 33 is as follows.
It has a low-pass filter that performs noise cut, a high-pass filter that performs zero point correction, and the like.

The estimated motor rotation speed (rotation speed) output from the gain correction unit 33 is obtained by subtracting the voltage drop due to the motor circuit resistance and the voltage drop due to the brush contact from the voltage command value. , The motor rotation speed (rotation speed) is accurate.

Therefore, the rotation speed of the steering assist motor can be accurately estimated, thereby improving the operability at the time of the driving operation (for example, a torque suitable for the driver's feeling can be generated).

The characteristic of the brush contact voltage drop has a complicated inflection point as shown in the graph of FIG. 2, and it is complicated and troublesome to express this by a functional expression. Since this is mapped and used for brush loss correction with reference to the map data, brush loss correction can be performed very easily.

In this embodiment, since the motor voltage command value is used instead of the motor detection voltage, a voltage detection circuit is not required, which simplifies the device configuration and reduces the cost. .

When it is not necessary to simplify the apparatus configuration and reduce the cost, the detected motor voltage may be used instead of the voltage command value.

The present invention is not limited to the application to the electric power steering apparatus, but can also be applied to an apparatus for determining the rotation speed of another motor using a brush. That is, the present invention may be applied to other devices using a DC motor, or devices using a winding type induction motor, a synchronous motor, or the like. In such a case, the same operation and effect as described above can be obtained.

[0030]

As described above, according to the present invention, the following excellent effects can be obtained. (1) According to the first to fourth aspects of the present invention, an accurate motor rotation speed without an error due to brush loss can be obtained. (2) According to the second to fourth aspects of the present invention, since the function data corresponding to the complicated brush contact voltage drop is mapped, the brush loss can be corrected very easily. (3) According to the third and fourth aspects of the present invention, since the motor voltage command value is employed, it is not necessary to provide a voltage detection circuit, which simplifies the device configuration and reduces the cost. (4) According to the invention as set forth in claim 4, in the electric power steering apparatus, the rotation speed of the steering assist motor can be accurately estimated, thereby improving the operability during the driving operation (for example, driving) It can generate torque that matches the sense of the person).

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a brush contact voltage drop and a motor circuit current.

FIG. 3 is a configuration diagram illustrating an example of an electric power steering device.

FIG. 4 is a block diagram showing an example of a conventional motor rotation speed calculation device.

FIG. 5 is a characteristic diagram illustrating a relationship between a motor circuit current and a motor voltage command value.

[Explanation of symbols]

 7 Torque sensor 8 Motor 10 Controller 11 Relay 12 Battery 30 Brush loss correction unit 30a Memory 31 Motor circuit resistance multiplication unit 32 Subtraction unit 33 Gain correction unit

Claims (4)

[Claims] 1. A motor rotation speed calculation for calculating a rotation speed of a motor by calculating a deviation between a voltage applied to the motor and a voltage drop component caused by a current flowing through a motor having a brush and a circuit resistance of the motor. An apparatus for calculating the number of revolutions of a motor, comprising: a brush loss correcting means for correcting the brush loss component of the deviation. 2. The motor rotation speed calculation device according to claim 1, wherein the brush loss correction means stores function data of a brush contact voltage drop with respect to a motor current as a map. 3. The motor rotation speed calculation device according to claim 1, wherein the voltage applied to the motor uses a motor voltage command value. 4. The motor rotation speed calculation device according to claim 1, wherein the motor is a motor that applies a steering force to a steering mechanism.