KR101509578B1 - Apparatus and method for calculating absolute position of driving shaft - Google Patents

Abstract

The present invention relates to an apparatus and a method for calculating an absolute position of a driving shaft in order to calculate the absolute position of the driving shaft of a harmonic drive connected to a motor. According to the present invention, the apparatus for calculating the absolute position of the driving shaft comprises: an incremental encoder; a potentiometer; and a control unit. The incremental encoder measures and outputs a first rotation amount of an output shaft while installed in the output shaft of the motor. The potentiometer measures and outputs a second rotation amount of the driving shaft while installed in the driving shaft of the harmonic drive connected to the output shaft of the motor. The control unit calculates the absolute position of the driving shaft on the basis of the first rotation amount and the second rotation amount inputted from the incremental encoder and the potentiometer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to an apparatus having a drive shaft, and more particularly, to an apparatus and method for calculating an absolute position of a drive shaft capable of calculating an absolute position of a drive shaft of a harmonic drive connected to a motor.

Drives with drive shafts, such as motors or actuators, are used in a variety of devices. Particularly, these actuators are used in robots, and compact actuators are required in the fingers and joints of robots.

When driving the apparatus through such a driver, it is important to grasp the absolute position of the drive shaft. In order to grasp the absolute position of the drive shaft in general, the apparatus performs an initial operation to find the reference position of the driver at initial drive.

Therefore, in order to use the device, a minimum space is required to perform the initial operation of the actuator. However, there is a problem in that, when a space is not secured enough to perform the initial operation of the driver, the device can not be used. Even if the space is secured, in the course of performing the initial operation, if the object is located in the area where the initial operation is performed, there is a risk of damage or safety accident.

In order to solve such a problem, an absolute position calculating device using magnet is used as an apparatus for estimating the absolute position of a drive shaft without performing an initial operation.

However, since the conventional absolute position calculating device has a large size, it can not be applied to a compact drive module installed at a place where the installation space is narrow like a joint of a robot.

Korean Patent Publication No. 2010-0052484 (2010.05.19.)

Accordingly, an object of the present invention is to provide an apparatus and method for calculating the absolute position of a drive shaft, which can be installed in a compact drive module to calculate the absolute position of the drive shaft.

It is another object of the present invention to provide an apparatus and method for calculating the absolute position of a drive shaft capable of calculating an absolute position of a drive shaft of a harmonic drive connected to a motor.

In order to achieve the above object, the present invention provides an absolute position calculating device for a drive shaft including an incremental encoder, a potentiometer and a control unit. The incremental encoder is installed on the output shaft of the motor and measures and outputs the first rotation amount of the output shaft. The potentiometer is installed on a drive shaft of a harmonic drive connected to an output shaft of the motor to measure and output a second rotation amount of the drive shaft. The control unit calculates an absolute position of the drive shaft based on the first rotation amount and the second rotation amount input from the incremental encoder and the potentiometer.

In the apparatus for calculating an absolute position of a drive shaft according to the present invention, the control unit reciprocally drives the drive shaft at a predetermined angle to receive a plurality of second rotations detected by the potentiometer, and averages the plurality of second rotations The initial position of the drive shaft can be calculated.

In the apparatus for calculating an absolute position of a drive shaft according to the present invention, the controller estimates the absolute position value of the drive shaft in one of the first and second amounts of rotation input after calculating the initial position, A correction value is calculated based on a difference value of one measured value, and the absolute position of the drive shaft can be calculated by adding the calculated correction value to the estimated absolute position value.

In the apparatus for calculating an absolute position of a drive shaft according to the present invention, the controller applies the second rotation amount to a prediction step of a Bayes filter to estimate an absolute position value of the drive shaft, The absolute position of the drive shaft can be calculated in addition to the absolute position value by estimating the correction value calculated by applying the estimated value of the first full amount and the measured value of the first turn amount to the correction step.

In the apparatus for calculating an absolute position of a drive shaft according to the present invention, the control section estimates an absolute position value of the drive shaft by applying the first rotation amount to an estimation step of a bass filter, The absolute position of the drive shaft can be calculated in addition to the absolute position value obtained by applying the measurement value of the second whole amount to the correction step and the calculated correction value.

In the drive shaft absolute position calculating device according to the present invention, the base filter may include a Kalman filter or a particle filter.

The control unit may further include a control unit that receives a first rotation amount of the output shaft measured and output by an incremental encoder provided on an output shaft of the motor and receives a first rotation amount of the output shaft measured by a potentiometer installed on a drive shaft of a harmonic drive connected to an output shaft of the motor, The control unit includes a step of calculating an absolute position of the drive shaft based on the first amount of rotation and the second amount of rotation input from the incremental encoder and the potentiometer The absolute position of the drive shaft is calculated.

In the method of calculating the absolute position of the drive shaft according to the present invention, the step of calculating the absolute position of the drive shaft may be such that the control unit reciprocally drives the drive shaft at a predetermined angle to receive a plurality of second rotation amounts measured by the potentiometer And the controller may calculate an initial position of the drive shaft by averaging the plurality of second rotations.

In the method of calculating the absolute position of the drive shaft according to the present invention, the step of calculating the absolute position of the drive shaft may be such that, after calculating the initial position, Calculating a correction value based on a difference between the estimated value of the other one of the first and second amounts of rotation and the other one of the measured values, and the controller calculates And calculating an absolute position of the drive shaft in addition to a correction value and an estimated absolute position value.

The absolute position calculating device of the drive shaft according to the present invention can be installed in a compact drive module to calculate the absolute position of the drive shaft. That is, since the incremental encoder is provided on the output shaft of the motor and the potentiometer is provided on the drive shaft of the harmonic drive, the absolute position calculating device can calculate the absolute position of the drive shaft by fusing the information obtained from the incremental encoder and the potentiometer have.

Since the incremental encoder and the potentiometer can be mounted on the output shaft of the motor and the drive shaft of the harmonic drive, respectively, the present invention can be applied to a compact drive module.

1 is a view showing a drive module including an absolute position calculating device for a drive shaft according to an embodiment of the present invention.
2 is a flowchart illustrating a method of calculating an absolute position of a drive shaft according to an embodiment of the present invention.
3 is a detailed flowchart of the calculating step of FIG.

In the following description, only parts necessary for understanding embodiments of the present invention will be described, and descriptions of other parts will be omitted to the extent that they do not disturb the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a drive module including an absolute position calculating device for a drive shaft according to an embodiment of the present invention.

1, a driving module 100 according to the present embodiment includes a motor 10 having an output shaft 15, a harmonic drive 20 having a driving shaft 21, (Hereinafter referred to as 'absolute position calculating device') of the drive shaft 21 for calculating the absolute position of the drive shaft 21.

The motor 10 transmits the rotational force necessary for rotating the object connected to the driving module 100 through the output shaft 15. The motor 10 includes a motor case 17, a rotor 11, a stator 13 and an output shaft 15. An output shaft 15 is coupled to the center of the rotor 11 and a stator 13 is installed to surround the rotor 11. [ The rotor (11) and the stator (13) are protected by a motor case (17). At this time, the output shaft 15 is hollow and provides a space in which the drive shaft 21 can be installed, and both ends protrude from both sides of the motor case 17.

The harmonic drive 20 is connected to an output shaft 15 protruded to one side of the motor 10 and the drive shaft 21 protrudes to the other side of the motor 10 through the hollow of the output shaft 15. The harmonic drive 20 decelerates in accordance with the rotation of the output shaft 15 in accordance with the reduction gear ratio to rotate the drive shaft 21.

The absolute position calculating device 30 calculates the absolute position of the rotating drive shaft 21. The absolute position calculating device 30 includes an incremental encoder 31, a potentiometer 33,

The incremental encoder 31 is provided on the output shaft 15 of the motor 10 and measures the first rotation amount of the output shaft 15 and outputs it to the control unit 35. [ The incremental encoder 31 is an encoder for simply converting the number of on / off pulses according to the amount of rotation of the output shaft 15 and outputting it, and provides the relative position value of the output shaft 15. At this time, the incremental encoder 31 may be installed on the output shaft 15 protruding toward the opposite side to the side on which the harmonic drive 20 is mounted, with the motor case 17 as the center.

The potentiometer 33 is installed on the drive shaft 21 of the harmonic drive 20 connected to the output shaft 15 of the motor 10 and measures the second rotation amount of the drive shaft 21 and outputs it to the control unit 35. The potentiometer 33 is installed on the drive shaft 21 protruding through the hollow of the output shaft 15 on the side where the incremental encoder 31 is installed. This potentiometer 33 is a variable resistor that changes the rotational displacement of the drive shaft 21 to a change in electrical resistance and provides information on the absolute position value of the rotating drive shaft 21. [ However, since the potentiometer 33 uses the variable resistance principle, there is an error in the information provided by the potentiometer 33. [ The potentiometer 33 may be of a wire type, a conductive plastic type, a cermet type, or a hybrid type, and it is preferable to use a thin type so as to be applicable to the compact driving module 100.

The control unit 35 performs the overall control operation of the driving module 100 including the absolute position calculating device 30. [ The control unit 35 calculates the absolute position of the drive shaft 21 together with the drive control of the motor 10. [ That is, the control unit 35 calculates the absolute position of the drive shaft 21 based on the first rotation amount and the second rotation amount received from the incremental encoder 31 and the potentiometer 33.

The control unit 35 can calculate the absolute position of the drive shaft 21 as follows.

First, the control unit 35 calculates the initial position of the drive shaft 21. In other words, the control unit 35 reciprocally drives the drive shaft 21 at a predetermined angle to receive a plurality of second rotations detected by the potentiometer 33. The control unit 35 calculates the initial position of the drive shaft 21 by averaging the plurality of second rotations.

The reason why the drive shaft 21 is reciprocally driven at a certain angle to calculate the initial position of the drive shaft 21 at this time is based on the variable resistance principle on the characteristics of the potentiometer 33. Therefore, The reliability of the amount of rotation is deteriorated. Therefore, by calculating the initial position of the drive shaft 21 by averaging a plurality of second rotations obtained from the potentiometer 33 through reciprocating drive at a certain angle, the reliability of the calculated initial position can be secured.

The predetermined angle for rotating the drive shaft 21 may be several degrees. For example, when the reduction ratio of the motor 10 and the harmonic drive 20 is 100 to 1, the reduction ratio may be 100degree on the basis of the incremental encoder 31 at the motor end. As the number of reciprocating driving increases, the reliability of the calculated initial position can be increased. However, since it takes time to calculate the initial position in proportion to the number of reciprocating driving, the number of reciprocating driving is determined in the range of 3 to 10 .

Next, the control unit 35 calculates the initial position and then estimates the absolute position of the drive shaft 21 in one of the first and second amounts of rotation input. The control unit 35 calculates the correction value based on the difference between the remaining one estimated value and the remaining one measured value. The control unit 35 can increase the accuracy of the calculated absolute position of the drive shaft 21 by calculating the absolute position of the drive shaft 21 in addition to the absolute position value estimated by the calculated correction value.

The control unit 35 may use a Bayes filter when calculating the absolute position of the drive shaft 21. [ The base filter may be a Kalman filter or a particle filter, but is not limited thereto.

For example, the control unit 35 uses the measured value of the potentiometer 33 in the prediction step and calculates the absolute position of the drive shaft 21 using the measured value of the incremental encoder 31 in the correction step Can be calculated. In other words, the control section 35 applies the second rotation amount to the estimation step of the bass filter to estimate the absolute position value of the drive shaft 21. [ The control unit 35 calculates the absolute position of the drive shaft 21 in addition to the absolute position value obtained by applying the estimated value of the first turn amount and the measured value of the first turn amount to the correction step can do.

Alternatively, the control unit 35 can use the measured value of the incremental encoder 31 in the estimation step and calculate the absolute position of the drive shaft 21 using the measured value of the potentiometer 33 in the correction step. In other words, the control section 35 applies the first rotation amount to the estimation step of the bass filter to estimate the absolute position value of the drive shaft 21. [ The control unit 35 can calculate the absolute position of the drive shaft 21 in addition to the absolute position value estimated by applying the estimated value of the second rotation amount and the measured value of the second rotation amount to the correction step.

A method of estimating the absolute position of the drive shaft 21 using a Kalman filter as a base filter will be described below.

The absolute position value of the drive shaft 21 estimated in the estimation step can be expressed by Equation 1 when the second rotation amount of the potentiometer 33 is used.

: t시간에서의 추정한 구동축의 절대 위치값here

: Absolute position value of drive shaft estimated at time t

: (t-1)시간에서의 구동축의 절대 위치값

: Absolute position value of drive shaft at (t-1) time

: 노이즈

: noise

에서 t=1인 경우, 구동축의 초기 위치값이 된다.

, T = 1, it becomes the initial position value of the drive shaft.

The correction value for Equation (1) can be expressed by Equation (2).

: t시간에서 증분형 엔코더로 측정한 회전량here

: Amount of rotation measured with incremental encoder at time t

: t시간에서 증분형 엔코더로 측정될 회전량의 추정값

: an estimate of the amount of rotation to be measured by the incremental encoder at time t

The absolute position of the drive shaft 21 that reflects the absolute position value of the drive shaft 21 estimated according to Equation 1 and the correction value according to Equation 2 can be calculated through Equation (3).

Where K is the Kalman gain.

On the other hand, the absolute position value of the drive shaft 21 estimated in the estimation step can be expressed by Equation (4) when the second rotation amount of the incremental encoder 31 is used.

: t시간에서의 추정한 구동축의 절대 위치값here

: Absolute position value of drive shaft estimated at time t

: (t-1)시간에서의 구동축의 절대 위치값

: Absolute position value of drive shaft at (t-1) time

: 노이즈

: noise

에서 t=1인 경우, 구동축(21)의 초기 위치값이 된다. 여기서

는

즉, 포텐셔미터(33)로 산출한 초기 위치값을 사용할 수 있다.

The value of the initial position of the drive shaft 21 is obtained. here

The

That is, the initial position value calculated by the potentiometer 33 can be used.

The correction value for Equation (4) can be expressed by Equation (5).

: t시간에서 포텐셔미터로 측정한 회전량here

: the amount of rotation measured with a potentiometer at time t

: t시간에서 포텐셔미터로 측정될 회전량의 추정값

: Estimation of the amount of rotation to be measured with the potentiometer at time t

The absolute position of the drive shaft 21 reflecting the absolute position value of the drive shaft 21 and the correction value according to Equation (5) according to Equation (4) can be calculated through Equation (6).

Thus, the absolute position calculating device 30 according to the present embodiment can be installed in the compact drive module 100 to calculate the absolute position of the drive shaft 21. In other words, the absolute position calculating device 30 has a structure in which the incremental encoder 31 is provided on the output shaft 15 of the motor 10 and the potentiometer 33 is provided on the drive shaft 21 of the harmony drive 20 , The absolute position of the drive shaft 21 can be calculated by fusing the information obtained from the incremental encoder 31 and the potentiometer 33.

Since the incremental encoder 31 and the potentiometer 33 can be installed on the output shaft 15 of the motor 10 and the drive shaft 21 of the monitor drive 20, ).

A method of calculating the absolute position of the drive shaft 21 using the absolute position calculating device 30 of the drive shaft 21 according to this embodiment will now be described with reference to FIGS. 1 to 3. FIG. 2 is a flowchart illustrating an absolute position calculating method of the drive shaft 21 according to an embodiment of the present invention. And Fig. 3 is a detailed flowchart of the calculating step of Fig.

The control unit 35 receives the first rotation amount of the output shaft 15 of the motor 10 from the incremental encoder 31 driven by the motor 10 and the first rotation amount of the output shaft 15 of the harmonic drive 20 from the potentiometer 33, And the second rotation amount of the drive shaft 21 of the drive shaft 21 is inputted. That is, when the motor 10 is driven under the control of the control unit 35, the harmonic drive 20 connected to the motor 10 is also driven. At this time, the incremental encoder 31 senses the first rotation amount of the output shaft 15 of the motor 10 and outputs it to the control unit 35. The potentiometer 33 senses the second rotation amount of the drive shaft 21 of the harmonic drive 20 and outputs it to the control unit 35.

In step S60, the control unit 35 calculates the absolute position of the drive shaft 21 on the basis of the first rotation amount and the second rotation amount.

The step of calculating the absolute position of the drive shaft 21 according to step S60 may be performed as shown in FIG. First, the control unit 35 calculates the absolute position of the driving shaft 21 at the initial stage of driving, and then calculates the absolute position of the driving shaft 21 with respect to the rotation of the driving shaft 21.

First, in step S61, the control unit 35 reciprocally drives the drive shaft 21 at a predetermined angle to receive the second rotation amount measured by the potentiometer 33. [ In step S63, the controller 35 calculates the initial position of the drive shaft 21 by averaging the plurality of second rotations.

Next, after calculating the initial position of the drive shaft 21 in step S65, the controller 35 estimates the absolute position value of the drive shaft 21 in one of the input first and second rotation amounts. For example, when the second full amount is used, the control unit 35 estimates the absolute position value of the drive shaft 21 according to Equation (1). When the first full amount is used, the controller 35 estimates the absolute position value of the drive shaft 21 according to Equation (4).

Next, in step S67, the controller 35 calculates a correction value based on the difference between the estimated value of the remaining one of the first and second amounts of rotation and the other measured value. For example, when the second whole amount is used, the control unit 35 can calculate the correction value by applying the estimated value of the first rotation amount and the measured value of the first rotation amount to the correction step according to the equation (2). When the first whole amount is used, the control unit 35 can calculate the correction value by applying the estimated value of the second rotation amount and the measured value of the second rotation amount to the correction step according to the equation (5).

In step S69, the control unit 35 calculates the absolute position of the drive shaft 21 by adding the calculated correction value and the estimated absolute position value. For example, when the second whole amount is used, the controller 35 calculates the absolute position of the drive shaft 21 estimated according to Equation (1) and the absolute position of the drive shaft 21 reflecting the correction value according to Equation (2) 3 can be calculated. When the first full amount is used, the controller 35 calculates the absolute position of the drive shaft 21 reflecting the absolute position value of the drive shaft 21 and the correction value according to Equation (5) according to Equation (4) Can be calculated.

As described above, in the absolute position calculating method of the drive shaft 21 according to the present embodiment, the initial absolute position of the drive shaft 21 is calculated through the potentiometer 33 and then the absolute position of the drive shaft 21 is measured by the potentiometer 33 and the incremental encoder 31 Since the absolute position of the drive shaft 21 is calculated by fusing the estimated value of the absolute position of the drive shaft 21 and the correction value based on the actual potentiometer 33 and the measured value measured by the incremental encoder 31, The accuracy of the absolute position of the drive shaft 21 can be improved.

It should be noted that the embodiments disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: Motor
11: Rotor
13: Stator
15: Output shaft
17: Motor case
20: Harmonic drive
21:
30: Absolute position calculating device of drive shaft
31: Incremental encoder
33: Potentiometer
35:
100: drive module

Claims (9)

delete An incremental encoder installed on an output shaft of the motor for measuring and outputting a first rotation amount of the output shaft;
A potentiometer installed on a drive shaft of a harmonic drive connected to an output shaft of the motor to measure and output a second rotation amount of the drive shaft;
And a controller for calculating the absolute position of the drive shaft based on the incremental encoder and the first and second amounts of rotation input from the potentiometer,
Wherein,
Wherein the control unit calculates the initial position of the drive shaft by reciprocating the drive shaft at a predetermined angle to receive a plurality of second rotational amounts detected by the potentiometer and averaging the plurality of second rotational amounts, Output device. 3. The apparatus of claim 2,
Estimating an absolute position value of the drive shaft in one of first and second rotational amounts inputted after calculating the initial position and calculating a correction value based on a difference value between the remaining one estimated value and the remaining one measured value, And the absolute position of the drive shaft is calculated by adding the calculated correction value to the estimated absolute position value. The apparatus of claim 3,
The second rotation amount is applied to a prediction step of a Bayes filter to estimate an absolute position value of the drive shaft and an estimated value of the first rotation amount and a measured value of the first rotation amount And calculates the absolute position of the drive shaft in addition to the absolute position value obtained by applying the correction value calculated by applying the correction value to the correction step. The apparatus of claim 3,
The absolute value of the position of the drive shaft is estimated by applying the first rotation amount to the estimation step of the Bayes filter and the correction value calculated by applying the estimated value of the second rotation amount and the measured value of the second rotation amount to the correction step, And calculates the absolute position of the drive shaft in addition to the absolute position estimated value. The method according to claim 4 or 5,
Wherein the Bayes filter includes a Kalman filter or a particle filter. delete The control unit receives the first rotation amount of the output shaft measured and output by the incremental encoder provided on the output shaft of the motor and receives the second rotation amount of the output shaft measured by the potentiometer installed on the drive shaft of the harmonic drive connected to the output shaft of the motor Inputting the whole amount;
And the controller calculates an absolute position of the drive shaft based on the first rotation amount and the second rotation amount received from the incremental encoder and the potentiometer,
Wherein the step of calculating the absolute position of the drive shaft comprises:
The control unit reciprocally drives the driving shaft at a predetermined angle to receive a plurality of second rotations measured by the potentiometer.
Calculating a first position of the drive shaft by averaging the plurality of second rotations;
And calculating an absolute position of the drive shaft based on the absolute position of the drive shaft. 9. The method of claim 8, wherein calculating the absolute position of the drive shaft comprises:
After calculating the initial position, the controller estimates the absolute position value of the drive shaft in one of the first and second amounts of rotation input;
Wherein the controller calculates a correction value based on a difference between the estimated value of the remaining one of the first and second amounts of rotation and the other measured value;
Wherein the controller calculates an absolute position of the drive shaft in addition to the calculated correction value and the estimated absolute position value;
And calculating an absolute position of the drive shaft based on the absolute position of the drive shaft.

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