CN-122001204-A - Dead time compensation for brushless DC motor control

Abstract

A method of operating an inverter for a brushless direct current (BLDC) motor includes driving a high-side switch to conduct current between a DC high node and an output node connected to the BLDC motor for a conduction period in each of a plurality of operation periods, driving a low-side switch to a conduction state to conduct current between the output node and a DC low node after a dead time after the conduction period, receiving a duty cycle command, determining an adjusted duty cycle representing the conduction period as part of the operation period, determining a duty cycle difference signal as a difference between an initial duty cycle based on the duty cycle command and the adjusted duty cycle, and determining a feedback duty cycle offset signal based on the duty cycle difference signal. The adjusted duty cycle is calculated based on the feedback duty cycle offset signal.

Inventors

• WANG TAIBIN
• ZUO MENGNAN
• LIU YONGFEI
• LU FEI

Assignees

• 操纵技术IP控股公司

Dates

Publication Date

20260508

Application Date

20241107

Claims (20)

1. 1. A method of operating an inverter for a brushless direct current, BLDC, motor, the method comprising: driving a high-side switch to a conductive state in each of a plurality of operation cycles to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period; Driving a low-side switch to an on state after a dead time after the on period to selectively conduct current between the output node and a DC low node, wherein a DC voltage is applied between the DC low node and the DC high node; Receiving a duty cycle command; Determining a duty cycle representing the adjustment of the on period as part of an operation period of the plurality of operation periods; determining a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command, and Determining a feedback duty cycle offset signal based on the duty cycle difference signal, Wherein determining the adjusted duty cycle comprises calculating the adjusted duty cycle based on the feedback duty cycle offset signal.
2. 2. The method of claim 1, wherein the inverter comprises a plurality of phase drivers, each phase driver configured to supply a corresponding DC power to the BLDC motor via a corresponding output node.
3. 3. The method of claim 1, wherein the initial duty cycle is equal to the duty cycle command.
4. 4. The method of claim 1, further comprising determining the initial duty cycle by applying a time delay response to the duty cycle command.
5. 5. The method of claim 1, wherein determining the feedback duty cycle offset signal further comprises calculating the feedback duty cycle offset signal by a proportional-integral PI controller and based on the duty cycle difference signal.
6. 6. The method of claim 1, wherein determining the adjusted duty cycle based on the feedback duty cycle offset signal further comprises: determining a final duty cycle offset signal based on the feedback duty cycle offset signal, and The final duty cycle offset signal is added to the duty cycle command to determine the adjusted duty cycle.
7. 7. The method of claim 6, wherein determining the final duty cycle offset signal based on the feedback duty cycle offset signal further comprises: Determining a polarity of current between the output node and the BLDC motor; determining a feed forward duty cycle offset signal based on the dead time and polarity of the current between the output node and the BLDC motor, and Subtracting the feedback duty cycle offset signal from the feedforward duty cycle offset signal to determine the final duty cycle offset signal.
8. 8. The method of claim 7, wherein determining the feed forward duty cycle offset signal based on the dead time and a polarity of the current between the output node and the BLDC motor further comprises: determining whether a polarity of the current between the output node and the BLDC motor is non-negative; setting the feed forward duty cycle offset signal based on the dead time in response to the polarity of the current between the output node and the BLDC motor being non-negative, and The feed forward duty cycle offset signal is set to zero in response to the polarity of the current between the output node and the BLDC motor being negative.
9. 9. The method of claim 1, wherein the BLDC motor is configured to at least one of apply an assist torque to a steering system of a vehicle or control the steering system.
10. 10. A method of operating an inverter for a brushless direct current, BLDC, motor, comprising: driving a high-side switch to a conductive state in each of a plurality of operation cycles to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for a conductive period; Driving a low-side switch to an on state after a dead time after the on period to selectively conduct current between the output node and a DC low node, wherein a DC voltage is applied between the DC low node and the DC high node; Receiving a duty cycle command; determining a current between the output node and the BLDC motor; Determining a feed forward duty cycle offset signal based on the current between the output node and the BLDC motor; Determining an adjusted duty cycle based on the feed-forward duty cycle offset signal and the duty cycle command, and The on period is determined based on the adjusted duty cycle and a duration of an operating period of the plurality of operating periods.
11. 11. The method of claim 10, wherein the inverter comprises a plurality of phase drivers, each phase driver configured to supply a corresponding DC power to the BLDC motor via a corresponding output node.
12. 12. The method of claim 10, wherein determining the feed forward duty cycle offset signal further comprises: Determining a polarity of the current between the output node and the BLDC motor, and The feed forward duty cycle offset signal is determined based on the dead time and a polarity of the current between the output node and the BLDC motor.
13. 13. The method of claim 12, wherein determining the feed forward duty cycle offset signal further comprises: determining whether a polarity of the current between the output node and the BLDC motor is non-negative; setting the feed forward duty cycle offset signal based on the dead time in response to the polarity of the current between the output node and the BLDC motor being non-negative, and The feed forward duty cycle offset signal is set to zero in response to the polarity of the current between the output node and the BLDC motor being negative.
14. 14. The method of claim 10, the method further comprising: Determining a feedback duty cycle based on an on-time of the on-period divided by a total time of a corresponding one of the plurality of operation periods; Determining a duty cycle difference signal as a difference between an initial duty cycle and the feedback duty cycle, wherein the initial duty cycle is based on the duty cycle command, and Determining a feedback duty cycle offset signal based on the duty cycle difference signal, Wherein determining the adjusted duty cycle based on the feed forward duty cycle offset signal and the duty cycle command comprises determining the adjusted duty cycle further based on the feedback duty cycle offset signal.
15. 15. The method of claim 14, wherein determining the feedback duty cycle offset signal further comprises calculating the feedback duty cycle offset signal by a proportional-integral PI controller and based on the duty cycle difference signal.
16. 16. The method of claim 14, wherein determining the adjusted duty cycle based on the feedforward duty cycle offset signal and the duty cycle command further comprises: subtracting the feedback duty cycle offset signal from the feedforward duty cycle offset signal to determine a final duty cycle offset signal, and The final duty cycle offset signal is added to the duty cycle command to determine the adjusted duty cycle.
17. 17. A system for operating a brushless direct current, BLDC, motor, the system comprising: A DC power supply comprising a DC high node and a DC low node, wherein a DC voltage is present between the DC low node and the DC high node; An inverter having a phase driver configured to apply DC power to the BLDC motor via an output node connected to the BLDC motor, wherein the phase driver includes a high-side switch configured to selectively conduct current between the DC high node and the output node, and a low-side switch configured to selectively conduct current between the output node and the DC low node, and A controller configured to: driving the high-side switch to an on state for an on period in each of a plurality of operation periods; driving the low-side switch to an on state after a dead time after the on period; Receiving a duty cycle command; Determining a duty cycle representing the adjustment of the on period as part of an operation period of the plurality of operation periods; determining a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command, and Determining a feedback duty cycle offset signal based on the duty cycle difference signal, Wherein determining the adjusted duty cycle comprises the controller calculating the adjusted duty cycle based on the feedback duty cycle offset signal.
18. 18. The system of claim 17, wherein the controller is further configured to: determining a final duty cycle offset signal based on the feedback duty cycle offset signal, and The final duty cycle offset signal is added to the duty cycle command to determine the adjusted duty cycle.
19. 19. The system of claim 18, wherein the controller is further configured to: Determining a polarity of current between the output node and the BLDC motor; determining a feed forward duty cycle offset signal based on the dead time and polarity of the current between the output node and the BLDC motor, and Subtracting the feedback duty cycle offset signal from the feedforward duty cycle offset signal to determine the final duty cycle offset signal.
20. 20. The system of claim 17, wherein the BLDC motor is configured to at least one of apply an assist torque to a steering system of a vehicle or control the steering system.

Description

Dead time compensation for brushless DC motor control Technical Field The present disclosure relates to control techniques for driving a brushless DC (BLDC) motor. More particularly, the present disclosure relates to control techniques that compensate for the effect of dead time in a driver for a BLDC motor. Background Vehicles such as cars, trucks, sport utility vehicles, cross-country vehicles, minivans, boats, aircraft, all-terrain vehicles, recreational vehicles, or other suitable forms of vehicles typically include a steering system, such as an Electric Power Steering (EPS) system, a steer-by-wire (SbW) steering system, a hydraulic steering system, or other suitable steering system. Steering systems of such vehicles typically control various aspects of vehicle steering, including providing steering assistance to an operator of the vehicle, controlling steerable wheels of the vehicle, and the like. Brushless DC (BLDC) motors have various applications. One such application is to provide steering torque in EPS systems or SbW steering systems. The inverter may be used to conduct current from a Direct Current (DC) power source to windings of the BLDC motor by selectively conducting current between either a DC positive node or a DC negative node and an output node. Dead time may be used to prevent shorting that might otherwise result from both the DC positive node and the DC negative node being connected to the output node at the same time. However, such dead time may have undesirable effects, such as non-linear operation, which may adversely affect the control of the BLDC motor. Disclosure of Invention An aspect of the disclosed embodiments includes a method of operating an inverter for a brushless direct current (BLDC) motor. The method includes driving a high-side switch to an on state in each of a plurality of operation periods to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for an on period, driving a low-side switch to an on state after a dead time after the on period to selectively conduct current between the output node and a DC low node, wherein a DC voltage is applied between the DC low node and the DC high node, receiving a duty cycle command, determining an adjusted duty cycle representative of the on period as part of the operation periods in the plurality of operation periods, determining a duty cycle difference signal as a difference between an initial duty cycle and the adjusted duty cycle, wherein the initial duty cycle is based on the duty cycle command, and determining a feedback duty cycle offset signal based on the duty cycle difference signal. Determining the adjusted duty cycle includes calculating the adjusted duty cycle based on the feedback duty cycle offset signal. Another aspect of the disclosed embodiments includes a method of operating an inverter for a brushless direct current (BLDC) motor. The method includes driving a high-side switch to an on state to selectively conduct current between a DC high node and an output node connected to the BLDC motor and for an on period during each of a plurality of operation periods, driving a low-side switch to an on state to selectively conduct current between the output node and a DC low node after a dead time after the on period, wherein a DC voltage is applied between the DC low node and the DC high node, receiving a duty cycle command, determining a current between the output node and the BLDC motor, determining a feed-forward duty cycle offset signal based on the current between the output node and the BLDC motor, determining an adjusted duty cycle based on the feed-forward duty cycle offset signal and the duty cycle command, and determining the on period based on the adjusted duty cycle and the duration of an operation period of the plurality of operation periods. Another aspect of the disclosed embodiments includes a system for operating a brushless direct current (BLDC) motor. The system for operating the BLDC motor includes a DC power source including a DC high node and a DC low node, wherein the DC low node and the DC high node have a DC voltage therebetween, an inverter having a phase driver configured to apply DC power to the BLDC motor via an output node connected to the BLDC motor, and a controller. The phase driver includes a high side switch configured to selectively conduct current between the DC high node and the output node, and a low side switch configured to selectively conduct current between the output node and the DC low node. The controller is configured to drive the high-side switch to an on state for an on period in each of a plurality of operation periods, drive the low-side switch to an on state after a dead time after the on period, receive a duty cycle command, determine an adjusted duty cycle representing the on period as part of the operation periods in the plurality of operation periods, determine a duty cycle difference signal as a difference between