Method and system for controlling an electric motor with compensation for time delay in position determination

• US 8,723,460 B2
• Filed: 06/27/2011
• Issued: 05/13/2014
• Est. Priority Date: 02/23/2011
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Wu, Long, Shaw, Robert, Kusumba, Srujan
• Primary Examiner(s): Masih, Karen
• Application Number:
  US13/169,533
• Publication Number:
  US 20120212162A1
• Time in Patent Office: 1,051 Days
• Field of Search: 318/400.02, 318/798, 318/690, 318/700, 318/727, 318/400.28, 318/400.08, 318/443, 318/434, 318/811
• US Class Current: 318/400.02
• CPC Class Codes: H02P 21/14 Estimation or adaptation of machine parameters, e.g. flux, current or voltage

Abstract

A sensor detects position data for a rotor of the motor at a first time. A data processor receives the detected position data associated with a first time delay. A sensing circuit senses an analog current at the motor during a second time delay. An analog-to-digital converter converts the analog current to a digital current data during a third time delay. The fourth time delay is detected between actual current reading instant and position reading instant in a data processor. The digital phase current data is transformed into measured direct and quadrature axes control current data based on synchronization or temporal alignment of the position data with the actual measured analog phase current at the starting time by compensating the position data by a sum of the second time delay, the third time delay and the fourth time delay, where the first time delay is subtracted from the sum.

Claims

1. A method for controlling a motor, the method comprising:

detecting, by a sensor, position data for a rotor of the motor at a first time;

receiving, by a data processor, the detected position data associated with a first time delay;

sensing, by a sensing circuit, an analog phase current at the motor by operating during a second time delay;

converting, by an analog-to-digital converter, the analog current to a digital current data during a third time delay;

detecting a fourth time delay between an actual current reading instant and a position reading instant in a data processor;

transforming the digital current data into measured direct and quadrature axes control current data based on synchronization or temporal alignment of the position data with the actual measured analog current at the starting time by compensating the position data by a sum of the second time delay, the third time delay and the fourth time delay, where the first time delay is subtracted from the sum, wherein the first time delay comprises a time period associated with transmission of a sensor signal from the sensor and receipt of the sensor signal at the data processor;

the second time delay comprises a time period when the sensing circuit senses an analog control current at motor windings of the motor via the sensor signal;

the third time delay comprises a time period associated with the analog-to-digital conversion and storage process in the analog-to-digital converter; and

the fourth time delay comprises a time period or offset from a phase current reading to a position data reading and determination in the data processor.

2. The method according to claim 1 wherein the analog current comprises analog three phase current and wherein digital current data comprises digital three phase current.

3. The method according to claim 1 wherein the first time delay comprises a time period associated with transmission of a sensor signal from the sensor and receipt of the sensor signal at the data processor;

the second time delay comprises a time period when the sensing circuit senses an analog control current at motor windings of the motor via the sensor signal;

the third time delay comprises a time period associated with the analog-to-digital conversion and storage process in the analog-to-digital converter; and

the fourth time delay comprises a time period or offset from a phase current reading to a position data reading and determination in the data processor.

4. The method according to claim 1 wherein the receiving of the detected position data at a data processor is communicated via a first data bus from the sensor to a field programmable gate array (FPGA) and a second data bus from the field programmable gate array to a digital signal processor (DSP), the first data bus comprising a serial data bus and the second bus comprising a parallel bus.

5. The method according to claim 1 wherein the transforming or converting of three-phase current readings into actual direct and quadrature-axes current data comprises establishing an adjusted direct-quadrature axes for the motor by the data processor, where the adjustment relates to the applying the temporal alignment to a raw direct-quadrature axes determined by the raw position sensor reading.

6. The method according to claim 1 wherein the transforming or converting of three-phase current readings into actual dq-axis currents comprises adjusting the transformation angle or rotor position angle, defined from phase-A magnetic axis to the positive direct axis.

7. The method according to claim 1 wherein the second time delay in the hardware sensing stage is determined by the following equation.

8. The method according to claim 1 wherein the transforming further comprises:

converting three-phase detected currents readings into actual direct and quadrature axes current data using actual position data of the rotor, which may be advanced in time from the detected position data in the data processor at the second time due to serial and parallel bus communication.

9. The method according to claim 1 further comprising:

applying, by the data processor, an additional compensation to the raw detected rotor position data reading in the data processor consistent with the following equation to adjust the hardware sensing stage delay, analog-to-digital conversion stage delay, currents reading and position reading difference delay in the data processor as well as raw position advancement due to serial and parallel bus communication;

10. A method for controlling a motor, the method comprising:

detecting, by a sensor, position data for a rotor of the motor at a first time;

receiving the detected position data at a data processor at a second time, wherein a first time delay is defined between the first time and the second time;

sensing an analog three phase control current at the motor by a hardware sensing stage that operates during a second time delay defined between the starting time and a third time;

converting, by an analog-to-digital converter, the analog three phase current to a digital three phase current data during a third time delay defined between the third time and a fourth time;

detecting the time difference between actual current reading instant and position reading instant in the data processor as a fourth time delay between the fourth time and second time; and

transforming, at the data processor, the digital three phase current data into measured direct-axis control current data and quadrature-axis control current data based on synchronization or temporal alignment of the position data with the actual measured three phase currents at the starting time by compensating the position data by a sum of the second time delay, the third time delay and the fourth time delay, where the first time delay is subtracted from the sum, wherein the first time delay comprises a time period associated with transmission of a sensor signal from the sensor and receipt of the sensor signal at the data processor;

the second time delay comprises a time period when the hardware sensing stage senses an analog control current at motor windings of the motor via the sensor signal;

the third time delay comprises a time period associated with the analog-to-digital conversion and storage process in the analog-to-digital converter; and

the fourth time delay comprises a time period or offset from a phase current reading to a position data reading and determination in the data processor.

11. The method according to claim 10 wherein the receiving of the detected position data at a data processor is communicated via a first data bus from the sensor to a field programmable gate array (FPGA) and a second data bus from the field programmable gate array to a digital signal processor (DSP), the first data bus comprising a serial data bus and the second bus comprising a parallel bus.

12. The method according to claim 10 wherein:

the sensing of the three phase actual currents further comprises first sensing by a current transducer and then adjusting the output of the current transducer by an amplifier;

the converting further comprises converting the analog values to digital values after sampling-hold delay; and

the detecting the time difference further comprises reading the three phase digital currents which were read by the data processor from peripheral registers of the analog-to-digital converter.

13. The method according to claim 10 wherein the transforming or converting of three-phase current readings into actual direct and quadrature-axes current data comprises establishing an adjusted direct-quadrature axes for the motor by the data processor, where the adjustment relates to the applying the temporal alignment to a raw direct-quadrature axes determined by the raw position sensor reading.

14. The method according to claim 10 wherein the transforming or converting of three-phase current readings into actual dq-axis currents comprises adjusting the transformation angle or rotor position angle, defined from the positive direct axis to a phase-A magnetic axis.

15. The method according to claim 10 wherein the hardware sensing stage comprises:

a low pass filter having a filter output;

a two stage operational amplifier configuration with an amplifier input and an amplifier output, the amplifier output coupled to the filter input; and

a current transducer with a transducer input and a transducer output, the transducer output is coupled to the amplifier input.

16. The method according to claim 10 wherein the second time delay in the hardware sensing stage is determined by the following equation:

17. The method according to claim 10 wherein the transforming further comprises:

converting three-phase detected currents readings into actual direct and quadrature axes current data using actual position data of the rotor, which may be advanced in time from the detected position data in the data processor at the second time due to serial and parallel bus communication.

18. The method according to claim 10 further comprising:

applying, by the data processor, an additional compensation to the raw detected rotor position data reading in the data processor consistent with the following equation to adjust the hardware sensing stage delay, analog-to-digital conversion stage delay, currents reading and position reading difference delay in the data processor as well as raw position advancement due to serial and parallel bus communication;

19. A system for controlling a motor, the system comprising:

a sensor for detecting position data for a rotor of the motor at a first time;

a data processor for receiving the detected position data associated with a first time delay;

a sensing circuit for sensing an analog phase current at the motor by operating during a second time delay;

an analog-to-digital converter for converting the analog current to a digital current data during a third time delay;

a data processor for detecting a fourth time delay between an actual current reading instant and a position reading instant in the data processor;

a phase converter for transforming the digital current data into measured direct and quadrature axes control current data based on synchronization or temporal alignment of the position data with the actual measured analog current at the starting time by the data processor'"'"'s compensating the position data by a sum of the second time delay, the third time delay and the fourth time delay, where the first time delay is subtracted from the sum, wherein the first time delay comprises a time period associated with transmission of a sensor signal from the sensor and receipt of the sensor signal at the data processor;

the second time delay comprises a time period when the sensing circuit senses an analog control current at motor windings of the motor via the sensor signal;

the third time delay comprises a time period associated with the analog-to-digital conversion and storage process in the analog-to-digital converter; and

the fourth time delay comprises a time period or offset from a phase current reading to a position data reading and determination in the data processor.

20. The system according to claim 19 wherein the analog current comprises analog three phase current and wherein digital current data comprises digital three phase current.

21. The system according to claim 19 wherein:

a first data bus for coupling the sensor to a data port capable of communication with the data processor;

the data processor comprising a field programmable gate array coupled to a digital signal processor via a second data bus; and

detected position data communicated via the first data bus from the sensor to the field programmable gate array and from the field programmable gate array to the digital signal processor (DSP).

22. The system according to claim 21 wherein the first data bus comprises a serial data bus and the second bus comprises a parallel bus.