# US 11,309,819 B2 · Initial rotor position detection in a brushless DC motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,819 B2 - Document ID: US11309819B2 - Status: Granted - Kind: B2 - Application number: 17/361,636 - Filed: 2021-06-29 - Published: 2021-12-16 - Granted: 2022-04-19 - Earliest claimed: 2017-09-22 - Applicants: Janislav Sega - Inventors: Janislav Sega - Web page: https://patentgrep.com/patent/US11309819B2 ## CPC - H02P 6/182: using back-emf in windings - H02P 25/03: with brushless excitation - H02P 6/14: Electronic commutators - H02P 6/18: without separate position detecting elements - H02P 6/185: using inductance sensing, e.g. pulse excitation - H02P 23/14: Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage - H02P 27/04: using variable-frequency supply voltage, e.g. inverter or converter supply voltage - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) A method as claimed in claim 1 wherein the method is applied to each of the series of phase coils. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 3) 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. ### Claim 5 (depends on 4) 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. ### Claim 6 (depends on 5) 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. ### Claim 7 (depends on 6) A method as claimed in claim 6 further comprising calculating a rotor position from the correlated measurements. ### Claim 8 (depends on 6) A method as claimed in claim 6 further comprising calculating a rotor rotation direction from the correlated measurements. ### Claim 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. ### Claim 10 (depends on 9) 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. ### Claim 11 (depends on 10) 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. ### Claim 12 (depends on 11) 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. ### Claim 13 (depends on 12) A method as claimed in claim 12 further comprising calculating a rotor position from the correlated measurements. ### Claim 14 (depends on 12) A method as claimed in claim 12 further comprising calculating a rotor rotation direction from the correlated measurements.