Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-10807635-B2
Application number	US-201816479254-A
Country	US
Kind code	B2
Filing date	Feb 13, 2018
Priority date	Feb 13, 2017
Publication date	Oct 20, 2020
Grant date	Oct 20, 2020

Abstract

An electric power steering apparatus of a vector control system that drives and controls a motor by an inverter and applies an assist torque to a steering system of a vehicle, including the first compensation function to perform a dead time (DT) compensation based on respective phase motor terminal voltages and respective phase duty command values, the second compensation function to perform a DT compensation based on steering assist command values, the third compensation function to perform the DT compensation based on dq-axis current command values, and a temperature detecting section to detect temperature of ECU, wherein the correction of the DT compensation is performed based on the temperature, wherein switches of the compensation functions are performed by using a conditional branch due to software and a gradual-changing switch, wherein the dq-axis DT compensation values after the conditional branch and the gradual-changing switch are performed are calculated, and wherein the dq-axis voltage command values are compensated by the dq-axis DT compensation values.

First claim

The invention claimed is:

1. An electric power steering apparatus of a vector control system that calculates dq-axis steering assist command values based on at least a steering torque, calculates dq-axis current command values from said dq-axis steering assist command values, converts dq-axis voltage command values calculated from said dq-axis current command values into duty command values of three phases, drives and controls a three-phase brushless motor by an inverter of a pulse width modulation (PWM) control, and applies an assist torque to a steering system of a vehicle, comprising:
a first compensation function to perform a dead time compensation “A” based on respective phase motor terminal voltages and said duty command values;
a second compensation function to perform a dead time compensation “B” based on said dq-axis steering assist command values; and
a third compensation function to perform a dead time compensation “C” based on said dq-axis current command values,
wherein switches of said first compensation function, said second compensation function and said third compensation function are performed by using a conditional branch due to software and a gradual-changing switch,
wherein dq-axis dead time compensation values are calculated, and
wherein said dq-axis voltage command values are compensated by said dq-axis dead time compensation values.

2. The electric power steering apparatus according to claim 1 , wherein said gradual-changing switch is used in a case that a switch difference of a compensation amount in a switching time is small and said conditional branch is used in a case that a quickness of switch timing is needed.

3. The electric power steering apparatus according to claim 1 ,
wherein a motor rotational angle, a motor rotational velocity and an inverter applying voltage are further used in calculations of said first compensation function, said second compensation function and said third compensation function.

4. The electric power steering apparatus according to claim 1 , further comprising:
a temperature detecting section to detect a temperature of said inverter or a temperature near said inverter,
wherein said temperature detecting section performs dead time corrections of said dead time compensation “B” and said dead time compensation “C” based on said temperature.

5. An electric power steering apparatus of a vector control system that calculates dq-axis steering assist command values based on at least a steering torque, calculates dq-axis current command values from said dq-axis steering assist command values, converts dq-axis voltage command values calculated from said dq-axis current command values into duty command values of three phases, drives and controls a three-phase brushless motor by an inverter of a pulse width modulation (PWM) control, and applies an assist torque to a steering system of a vehicle, comprising:
a dead time compensating section “A” to calculate a compensation value “CA” based on respective phase motor terminal voltages, said duty command values, a motor rotational angle, a motor rotational velocity and an inverter applying voltage;
a dead time compensating section “B” to calculate a compensation value “CB” based on said dq-axis steering assist command values, said motor rotational angle, said motor rotational velocity and said inverter applying voltage;
a dead time compensating section “C” to calculate a compensation value “CC” based on said dq-axis current command values, said motor rotational angle, said motor rotational velocity and said inverter applying voltage; and
a compensation value switching section to input said compensation value “CA”, said compensation value “CB”, said compensation value “CC”, and a switch condition which is determined by said dq-axis steering assist command values, said dq-axis current command values and said motor rotational velocity, to perform a switching of said compensation value “CA”, said compensation value “CB” and said compensation value “CC” using a conditional branch due to software and a gradual-changing switch depending on a judged condition, and to calculate dq-axis dead time compensation values,
wherein said dq-axis voltage command values are compensated by said dq-axis dead time compensation values.

6. The electric power steering apparatus according to claim 5 ,
wherein said compensation value switching section comprises:
a switch judging section to input said dq-axis current command values and said motor rotational velocity, perform a switch judgment and output a switch judgment flag;
a conditional branch section to input said compensation values “CB” and “CC” and output dq-axis compensation values “CD” using said conditional branch based on said switch judgment flag;
a gradual-changing section to judge said gradual-changing switch based on said dq-axis steering assist command values and calculate gradual-changing ratios; and
a gradual-changing switching section to input said compensation value “CA” and said dq-axis compensation values “CD” and calculate and output said dq-axis dead time compensation values using said gradual-changing ratios.

7. The electric power steering apparatus according to claim 6 ,
wherein said gradual-changing section comprises:
a gradual-changing switch judging section to judge said gradual-changing switch based on said dq-axis steering assist command values and output an UP-DOWN judgment flag; and
a gradual-changing ratio calculating section to calculate said gradual-changing ratios based on said UP-DOWN judgment flag.

8. The electric power steering apparatus according to claim 7 ,
wherein said gradual-changing ratios are a gradual-changing ratio “RA” for said compensation value “CA” and a gradual-changing ratio “RBC” for said compensation values “CB” and “CC”, and
wherein said gradual-changing switching section comprises:
a first multiplying section to multiply said compensation value “CA” with said gradual-changing ratio “RA”;
a second multiplying section to multiply said dq-axis command “CD” with said gradual-changing ratio “RBC”; and
an adding section to add with a multiplied result of said first multiplying section and a multiplied result of said second multiplying section and output said dq-axis dead time compensation values.

9. An electric power steering apparatus of a vector control system that calculates dq-axis steering assist command values based on at least a steering torque, calculates dq-axis current command values from said dq-axis steering assist command values, converts dq-axis voltage command values calculated from said dq-axis current command values into duty command values of three phases, drives and controls a three-phase brushless motor by an inverter of a pulse width modulation (PWM) control, and applies an assist torque to a steering system of a vehicle, comprising:
a temperature detecting section to detect a temperature of said inverter or a temperature near said inverter;
a dead time compensating section “A” to calculate a compensation value “CA” based on respective phase motor terminal voltages, said duty command values, a motor rotational angle, a motor rotational velocity and an inverter applying voltage;
a dead time compensating section “B” to calculate a compensation value “CB” based on said dq-axis steering assist command values, said motor rotational angle, said motor rotational velocity, said inverter applying voltage and said temperature;
a dead time compensating section “C” to calculate a compensation value “CC” based on said dq-axis current command values, said motor rotational angle, said motor rotational velocity, said inverter applying voltage and said temperature; and
a compensation value switching section to input said compensation

Assignees

• Nsk Ltd

Inventors

• Takase Hiroaki
• MINAKI Ryo
• Sawada Hideki
• Sugawara Takayoshi

Classifications

• H02P27/08 Primary

  with pulse width modulation · CPC title

• H02M1/385

  with means for correcting output voltage deviations introduced by the dead time · CPC title

• B60L2240/12

  Speed · CPC title

• B62D5/0496

  by using a temperature sensor · CPC title

• H02P21/06

  Rotor flux based control involving the use of rotor position or rotor speed sensors · CPC title