Initial rotor position detection in a brushless DC motor
View Patent ↗A method of operating a Brushless Direct Current Motor (BLDCM), the BLDCM of the type including: a series of concentric independently activated electromagnetic phase coils interacting with a series of permanent magnets to provide relative movement therebetween, the phase coils having temporal periods of activation time and deactivation time, the method including the steps of: (a) activating at least one of the phase coils for a short period of activation; and (b) measuring the voltage response across the phase coil of the deactivated phase coil during the short period of activation to determine the rotor position.
1. A method of operating a Brushless Direct Current Motor (BLDCM), the BLDCM of the type including: a series of concentric independently activated electromagnetic phase coils interacting with a series of permanent magnets to provide relative movement therebetween, the phase coils having temporal periods of activation time and deactivation time, the method including the steps of:
(a) activating at least one of the phase coils for a short period of activation, and applying a preceding short duration pulse to demagnetize the BLDCM stator core before measuring the voltage response across the phase coil; and
(b) measuring the voltage response across the phase coil of the deactivated phase coil during the short period of activation to determine the rotor position.
2. A method as claimed in claim 1 wherein the method is applied to each of the series of phase coils.
3. A method as claimed in claim 1 further comprising the step of:
(c) measuring the voltage response during the on-time activation of the activation time across the phase coil (Von) and utilizing the on-time of the open phase winding voltages to determine an estimated rotor position.
4. A method as claimed in claim 3 further comprising the steps of:
(d) activating the low-side power transistor switches of the phase coil during the off-time interval of the pulse measurement; and
(e) measuring the voltage response during the off-time activation across the phase coil (Voff), and utilizing both the on-time and off-time activation (Von, Voff) of the open phase winding voltages to determine an estimated rotor position.
5. A method as claimed in claim 4 further comprising the step of:
(f) measuring the on-time voltage level (Vs) and off-time voltage level (Vsoff) of the supply voltage to the BLDCM to correct open phase voltage measurements (Von, Voff) for power supply voltage fluctuations.
6. A method as claimed in claim 5 wherein said step (f) further comprises:
correlating the measured on-time (Von) and off-time (Voff) open phase voltages using on-time (Vs) and off-time (Vsoff) supply voltage measurements to form a series of correlated measurements.
7. A method as claimed in claim 6 further comprising calculating a rotor position from the correlated measurements.
8. A method as claimed in claim 6 further comprising calculating a rotor rotation direction from the correlated measurements.
9. A method of operating a Brushless Direct Current Motor (BLDCM), the BLDCM of the type including: a series of concentric independently activated electromagnetic phase coils interacting with a series of permanent magnets to provide relative movement therebetween, the phase coils having temporal periods of activation time and deactivation time, the method including the steps of:
(a) activating at least one of the phase coils for a short period of activation;
(b) measuring the voltage response across the phase coil of the deactivated phase coil during the short period of activation to determine the rotor position; and
(c) measuring the voltage response during the on-time activation of the activation time across the phase coil (Von) and utilizing the on-time of the open phase winding voltages to determine an estimated rotor position.
10. A method as claimed in claim 9 further comprising the steps of:
(d) activating the low-side power transistor switches of the phase coil during the off-time interval of the pulse measurement; and
(e) measuring the voltage response during the off-time activation across the phase coil (Voff), and utilizing both the on-time and off-time activation (Von, Voff) of the open phase winding voltages to determine an estimated rotor position.
11. A method as claimed in claim 10 further comprising the step of:
(f) measuring the on-time voltage level (Vs) and off-time voltage level (Vsoff) of the supply voltage to the BLDCM to correct open phase voltage measurements (Von, Voff) for power supply voltage fluctuations.
12. A method as claimed in claim 11 wherein said step (f) further comprises:
correlating the measured on-time (Von) and off-time (Voff) open phase voltages using on-time (Vs) and off-time (Vsoff) supply voltage measurements to form a series of correlated measurements.
13. A method as claimed in claim 12 further comprising calculating a rotor position from the correlated measurements.
14. A method as claimed in claim 12 further comprising calculating a rotor rotation direction from the correlated measurements.