Method and device for measuring speed of permanent magnet synchronous motor

Patent metadata

Field	Value
Publication number	US-10451647-B2
Application number	US-201715455062-A
Country	US
Kind code	B2
Filing date	Mar 9, 2017
Priority date	Dec 31, 2016
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

A method for measuring speed of a permanent magnet synchronous motor includes: acquiring a number K of pulse signals received in a current measuring period and outputted by an incremental encoder; acquiring a first duration S n-1 between a time point when a pulse is last received in a previous measuring period and a time point when the previous measuring period ends, and a second duration S n between a time point when a pulse is last received in the current measuring period and a time point when the current measuring period ends; calculating a third duration T 0 , measured between the time point when the pulse is last received in the previous measuring period and the time point when the pulse is last received in the current measuring period, according to the length T of the current, measuring period, the first duration S n-1 and the second duration S n ; and calculating a motor speed v according to formula:

v
=

K

K
0

×

1

T
⁢

⁢
0

.

First claim

What is claimed is:

1. A method for measuring speed of a permanent magnet synchronous motor, comprising:
providing a device electronically coupled to an incremental encoder of the permanent magnet synchronous motor;
acquiring, by the device, a number K of pulse signals received in a current measuring period and outputted by the incremental encoder, the current measuring period having a length of T;
acquiring a first duration S n-1 measured between a time point when a pulse is last received in a previous measuring period and a time point when the previous measuring period ends, and a second duration S n measured between a time point when a pulse is last received in the current measuring period and a time point when the current measuring period ends;
calculating a third duration T 0 , measured between the time point when the pulse is last received in the previous measuring period and the time point when the pulse is last received in the current measuring period, according to the length T of the current measuring period, the first duration S n-1 and the second duration S n ; and
calculating a motor speed v according to the following formula:

v
=

K

K
0

×

1

T
⁢

⁢
0

,

 where K 0 is a number of the pulses outputted by the incremental encoder when the permanent magnet synchronous motor rotates for one revolution;
wherein the step of acquiring the second duration S n measured between the time point when the pulse is last received in the current measuring period and the time point when the current measuring period ends, comprises:
resetting a high frequency timer when receiving the pulse outputted by the incremental encoder;
the high frequency timer incrementing a count value if the permanent magnet synchronous motor rotates in a forward direction;
the high frequency timer decrementing a count value if the permanent magnet synchronous motor rotates m a reverse direction; and
acquiring a time value from the high frequency timer as the second duration S n when the current measuring period ends.

2. The method of claim 1 , wherein the current measuring period is started and terminated by the interruption timer, the length T of the current measuring period equals to a ratio of a preset value of the interruption tinier to an interruption clock frequency, and the time value from the high frequency tinier equals to a ratio of the count value in a register of the high frequency timer to clock frequency of the high frequency timer.

3. The method of claim 1 , wherein the step of acquiring the number K of pulse signals received in the current measuring period and outputted by the incremental encoder comprises:
setting a value of a counter that acquires the pulse signals to zero when the current measuring period starts, and the value of the counter when the current measuring period ends is determined to be the number of pulse signals received in the current measuring period and outputted by the incremental encoder.

4. The method of claim 1 , wherein the step of calculating the third duration T 0 , measured between the time point when the pulse is last received in the previous measuring period and the time point when the pulse is last received in the current measuring period, comprises:
when the permanent magnet synchronous motor rotates in a forward direction, the third duration T 0 is calculated according to the following, formula: T 0 =T−S n +S n-1 ;
when the permanent magnet synchronous motor rotates in a reverse direction, the third duration T 0 is calculated according to the following formula: T 0 =T−S n-1 +S n .

5. A device for measuring speed of a permanent magnet synchronous motor, wherein the device is electronically coupled to an incremental encoder of the permanent magnet synchronous motor, and the device comprises:
a counter configured to acquire a number K of pulse signals received in a current measuring period and outputted by the incremental encoder, the current measuring period having a length of T;
a timing module configured to acquire a first duration S n-1 measured between a time point when a pulse is last received in a previous measuring period and a time point when the previous measuring period ends, and a second duration S n measured between a time point when a pulse is last received in the current measuring period and a time point when the current measuring period ends;
a first calculating module configured to calculate a third duration T 0 , measured between the time point when the pulse is last received in the previous measuring period and the time point when the pulse is last received in the current measuring period, according to the length T of the current measuring period, the first duration S n-1 and the second duration S n ; and
a second calculating module configured to calculate a motor speed v, according to the following formula:

v
=

K

K
0

×

1

T
⁢

⁢
0

,

 where K 0 is a number of the pulses outputted by the incremental encoder when the permanent magnet synchronous motor rotates for one revolution;
wherein the first calculating module comprises a direction determining module, a first calculating unit and a second calculating unit;
the direction determining module is configured to select the first calculating unit or the second calculating unit;
the first calculating unit is configured to, when the permanent magnet synchronous motor rotates in a forward direction, calculate the third duration T 0 according to the following formula: T 0 =T−S n +S n-1 ; and
the second calculating unit is configured to, when the permanent magnet synchronous motor rotates in a reverse direction, calculate the third duration T 0 according to the following formula: T 0 =T−S n-1 +S n .

6. The device of claim 5 , wherein the timing module comprises a resetting unit and a high frequency timer, the resetting unit is configured to reset the high frequency timer when receiving the pulse outputted by the incremental encoder, and the high frequency timer increments a count value if the permanent magnet synchronous motor rotates in a forward direction, and decrements a count value if the permanent magnet synchronous motor rotates in a reverse direction.

7. The device of claim 6 , further comprising an interruption timer, wherein the current measuring period is started and terminated by the interruption timer, the length T of the current measuring period equals to a ratio of a preset value of th

Assignees

• Ubtech Robotics Corp

Inventors

• Xiong Youjun
• Fan Wenhua
• Zhang Lifu
• Xiao Jianyun

Classifications

• G01P3/481 Primary

  of pulse signals · CPC title

• G01D5/243

  influencing the phase or frequency of AC · CPC title

• G01P3/486

  delivered by photo-electric detectors · CPC title

• G01P3/36

  Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light (G01P3/68 takes precedence; gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams G01C19/64) · CPC title