# US 11,906,349 B2 · Methods, systems and devices for determining a resonance frequency of a mechanical system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,906,349 B2 - Document ID: US11906349B2 - Status: Granted - Kind: B2 - Application number: 17/123,285 - Filed: 2020-12-16 - Published: 2021-06-24 - Granted: 2024-02-20 - Earliest claimed: 2019-12-20 - Assignees: Schneider Toshiba Inverter Europe SAS - Applicants: Schneider Toshiba Inverter Europe SAS - Inventors: Al Kassem Jebai; Mohamad Koteich - Web page: https://patentgrep.com/patent/US11906349B2 ## CPC - G01H 13/00: Measuring resonant frequency - H02P 1/04: Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter - B06B 1/0215: {for generating pulses, e.g. bursts of oscillations, envelopes} - H02P 29/02: Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36) - H02P 29/024: Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load - H02P 29/026: {the fault being a power fluctuation} - H02P 29/032: Preventing damage to the motor, e.g. setting individual current limits for different drive conditions - H02P 29/50: Reduction of harmonics - G01H: MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) ## Abstract A method for determining a resonance frequency of a mechanical system including an electric motor coupled to a mechanical load. The method includes starting the motor by providing a supply voltage using a motor controller, and once the electric motor is running at a predefined target rotational speed, applying a first excitation signal comprising a voltage pulse superimposed to the supply voltage. The method further includes measuring a mechanical response of the mechanical system, using a measurement system coupled to the motor, and analyzing the measured response, to determine at least one resonance frequency of the mechanical system. ## Claims ### Claim 1 A method for determining a resonance frequency of a mechanical system comprising an electric motor coupled to a mechanical load, said method comprising: starting the motor by providing a supply voltage using a motor controller; once the electric motor is running at a predefined target rotational speed, applying a first excitation signal comprising a voltage pulse superimposed to the supply voltage; measuring a mechanical response of the mechanical system by measuring stator currents of the motor using a measurement system coupled to the motor, said measurement system comprising one or more current sensors coupled to input terminals of the stator of the motor; and analyzing the measured response, to determine at least one resonance frequency of the mechanical system based on the measured stator currents, wherein determining the resonance frequency of the mechanical system comprises: calculating, from the measured stator currents, corresponding stator current values expressed in a synchronous frame of the motor; calculating phase difference values between the calculated corresponding stator current values; identifying oscillations in the calculated phase difference values; and determining the resonance frequency based on the identified oscillations. ### Claim 2 (depends on 1) The method according to claim 1, wherein the method further comprises applying at least one additional excitation voltage pulse and measuring the corresponding response of the mechanical system, the resonance frequency being determined from the analysis of the measured responses. ### Claim 3 (depends on 2) The method according to claim 2, wherein said at least one additional excitation pulse differs from the first excitation pulse by at least one parameter, such as pulse length, or pulse amplitude, or the time interval between two consecutive pulses. ### Claim 4 (depends on 1) The method according to claim 1, wherein the method further comprises: changing the supply voltage using the motor controller to set the motor into a different rotational speed; once the electric motor is running at the new target rotational speed, applying another excitation signal comprising a voltage pulse superimposed to the supply voltage, using the pulse generator; measuring the new mechanical response of the mechanical system, using the measurement system; analyzing the measured response, to determine at least one resonance frequency of the mechanical system. ### Claim 5 (depends on 1) The method according to claim 1, wherein starting the motor comprises ramping up the supply voltage towards a threshold voltage value, and wherein the motor controller is placed in an open loop control mode once the electric motor is running at the predefined target rotational speed. ### Claim 6 (depends on 1) The method according to claim 1, wherein the method includes determining the type of mechanical coupling between the load and the motor based on the measured mechanical response. ### Claim 7 (depends on 1) A method for driving a mechanical system comprising an electric motor coupled to a mechanical load, said method comprising: determining the resonance frequency of the mechanical system using a method in accordance with claim 1; modifying at least one operating parameter of the motor to avoid generating excitations near or at the determined resonance frequency. ### Claim 8 A device for determining a resonance frequency of a mechanical system comprising an electric motor coupled to a mechanical load, said device comprising a control system configured to: start the motor by providing a supply voltage using a motor controller; once the electric motor is running at a predefined target rotational speed, applying a first excitation signal comprising a voltage pulse superimposed to the supply voltage; measure a mechanical response of the mechanical system by measuring stator currents of the motor using a measurement system coupled to the motor, said measurement system comprising one or more current sensors coupled to input terminals of the stator of the motor; and analyze the measured response, to determine at least one resonance frequency of the mechanical system based on the measured stator currents, wherein determining the resonance frequency of the mechanical system comprises: calculating, from the measured stator currents, corresponding stator current values expressed in a synchronous frame of the motor; calculating phase difference values between the calculated corresponding stator current values; identifying oscillations in the calculated phase difference values; and determining the resonance frequency based on the identified oscillations.