# US 11,121,654 B2 · Dynamic stability control for electric motor drives using stator flux oriented control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,121,654 B2 - Document ID: US11121654B2 - Status: Granted - Kind: B2 - Application number: 16/588,526 - Filed: 2019-09-30 - Published: 2021-04-01 - Granted: 2021-09-14 - Earliest claimed: 2019-09-30 - Assignees: SF Motors, Inc. - Applicants: SF Motors, Inc. - Inventors: Apoorva Athavale; Ruonan Zhou; Chen-Yen Yu; Yifan Tang - Web page: https://patentgrep.com/patent/US11121654B2 ## CPC - H02P 21/0003: {Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control} - H02P 21/09: Field phase angle calculation based on rotor voltage equation by adding slip frequency and speed proportional frequency - B60L 15/025: {using field orientation; Vector control; Direct Torque Control [DTC]} - B60L 15/20: for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed - B60W 30/02: Control of vehicle driving stability - B60L 2220/12: Induction machines - B60L 2240/423: Torque - B60L 2240/429: Current - Y02T 10/64: Electric machine technologies in electromobility - Y02T 10/72: Electric energy management in electromobility - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Dynamic stability control for electric motors is provided. The system determines, for an electric motor of the electric vehicle, a slip frequency indicating a difference between a synchronous speed of a magnetic field of the electric motor and a rotating speed of a rotor of the electric motor. The system compares the slip frequency with a threshold. The system activates, responsive to the slip frequency greater than or equal to the threshold, a slip limiter to adjust a current command to generate an adjusted current command that causes a reduction in the slip frequency. The system deactivates, responsive to an external torque command less than a subsequent current command received subsequent to transmission of the adjusted current command, the slip limiter. ## Claims ### Claim 1 A system to maintain torque in an electric vehicle, comprising: a vehicle stability control system comprising one or more processors to: determine, for an electric motor of the electric vehicle, a slip frequency indicating a difference between a synchronous speed of a magnetic field of the electric motor and a rotating speed of a rotor of the electric motor; compare the slip frequency with a threshold; activate, responsive to the slip frequency greater than or equal to the threshold, a slip limiter to adjust a current command to generate an adjusted current command that causes a reduction in the slip frequency; and deactivate, responsive to an external torque command less than a subsequent current command received subsequent to transmission of the adjusted current command, the slip limiter, wherein the external torque command corresponds to an indication to accelerate movement of the electric vehicle, and the electric motor comprises an induction motor. ### Claim 2 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: determine an electrical angular velocity; determine a mechanical angular velocity; and determine the slip frequency based on a difference between the electrical angular velocity and the mechanical angular velocity. ### Claim 3 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: identify a stator voltage command vector, a stator current vector, and a mechanical angle position; determine a stator flux vector based on the stator voltage command vector, the stator current vector, and the mechanical angle position; determine an electrical angular velocity based on the stator flux vector; determine a mechanical angular velocity; and determine the slip frequency based on a difference between the electrical angular velocity and the mechanical angular velocity. ### Claim 4 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: determine a slip error between the threshold and the slip frequency determined for the electric motor; and generate the adjusted current command based on the slip error. ### Claim 5 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: determine a difference between the slip frequency and the threshold; input the difference into a proportional-integral controller to output a compensation q-axis current command; receive a torque command; determine the current command based on the torque command; and determine the adjusted current command based on the compensation q-axis current command and the current command. ### Claim 6 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: receive a torque command responsive to the indication to accelerate movement of the electric vehicle; determine the current command based on the torque command; and adjust the current command to generate the adjusted current command responsive to receipt of the torque command to accelerate movement of the electric vehicle, wherein the adjusted current command causes acceleration of the movement of the electric vehicle that is different from the current command based on the torque command received responsive to the indication to accelerate movement of the electric vehicle. ### Claim 7 (depends on 1) The system of claim 1, comprising the vehicle stability control system to: detect the slip frequency greater than the threshold responsive to a q-axis current regulator increasing the slip frequency responsive to a torque command exceeding a pull-out torque; and activate, responsive to the slip frequency greater than the threshold, the slip limiter to manage oscillations in a q-axis current, manage oscillations in torque, or prevent an overcurrent fault. ### Claim 8 A method of maintaining torque in an electric vehicle, comprising: determining, by a vehicle stability control system comprising one or more processors, for an electric motor of the electric vehicle, a slip frequency indicating a difference between a synchronous speed of a magnetic field of the electric motor and a rotating speed of a rotor of the electric motor; comparing, by the vehicle stability control system, the slip frequency with a threshold; activating, by the vehicle stability control system, responsive to the slip frequency greater than or equal to the threshold, a slip limiter to adjust a current command to generate an adjusted current command that causes a reduction in the slip frequency; and deactivating, by the vehicle stability control system, responsive to an external torque command less than a subsequent current command received subsequent to transmission of the adjusted current command, the slip limiter, wherein the external torque command corresponds to pushing an accelerator in the electric vehicle, and the electric motor comprises an induction motor. ### Claim 9 (depends on 8) The method of claim 8, comprising: determining an electrical angular velocity; determining a mechanical angular velocity; and determining the slip frequency based on a difference between the electrical angular velocity and the mechanical angular velocity. ### Claim 10 (depends on 8) The method of claim 8, comprising: identifying a stator voltage command vector, a stator current vector, and a mechanical angle position; determining a stator flux vector based on the stator voltage command vector, the stator current vector, and the mechanical angle position; determining an electrical angular velocity based on the stator flux vector; determining a mechanical angular velocity; and determining the slip frequency based on a difference between the electrical angular velocity and the mechanical angular velocity. ### Claim 11 (depends on 8) The method of claim 8, comprising: determining a slip error between the threshold and the slip frequency determined for the electric motor; and generating the adjusted current command based on the slip error. ### Claim 12 (depends on 8) The method of claim 8, comprising: determining a difference between the slip frequency and the threshold; inputting the difference into a proportional-integral controller to output a compensation q-axis current command; receiving a torque command; determining the current command based on the torque command; and determining the adjusted current command based on the compensation q-axis current command and the current command. ### Claim 13 (depends on 8) The method of claim 8, comprising: receiving a torque command responsive to an indication to accelerate movement of the electric vehicle; determining the current command based on the torque command; and adjusting the current command to generate the adjusted current command responsive to receipt of the torque command to accelerate movement of the electric vehicle, wherein the adjusted current command causes acceleration of the movement of the electric vehicle that is different from the current command based on the torque command received responsive to the indication to accelerate movement of the electric vehicle. ### Claim 14 (depends on 8) The method of claim 8, comprising: detecting the slip frequency greater than the threshold responsive to a q-axis current regulator increasing the slip frequency responsive to a torque command exceeding a pull-out torque; and activating, responsive to the slip frequency greater than the threshold, the slip limiter to manage oscillations in a q-axis current, manage oscillations in torque, or prevent an overcurrent fault. ### Claim 15 A system to maintain torque in an electric vehicle, comprising: a vehicle stability control system comprising one or more processors to: determine, for an electric motor of the electric vehicle, a stator flux angle in a rotor reference frame of the electric motor; compare the stator flux angle with a threshold; activate, responsive to the stator flux angle greater than or equal to the threshold, a stator flux angle limiter to adjust a current command to cause a reduction in the stator flux angle; and deactivate, responsive to an external torque command less than the current command adjusted by the stator flux angle limiter, the stator flux angle limiter, wherein the external torque command corresponds to an indication to accelerate movement of the electric vehicle, and the electric motor comprises a surface permanent magnet motor. ### Claim 16 (depends on 15) The system of claim 15, wherein the threshold corresponds to a pull-out stator flux angle of pi/2. ### Claim 17 (depends on 15) The system of claim 15, comprising the vehicle stability control system to: identify a stator voltage command vector, a stator current vector, and a mechanical angle position; determine a stator flux vector based on the stator voltage command vector, the stator current vector, and the mechanical angle position; and determine the stator flux angle as an angle between the stator flux vector and the stator current vector.