| 主权项 |
1. An electric power steering apparatus comprising a torque sensor to detect a steering torque applied to a steering mechanism, a steering assist command value calculating section to calculate a steering assist command value, a motor for generating an assist force that assists steering of a steering wheel, and a motor drive control section to calculate an assist amount based on said steering assist command value and to control drive of said motor through a driving section comprising a bridge of Field Effect Transistors (FETs), wherein said electric power steering apparatus further comprising:
a power voltage monitoring section to determine by comparing a power voltage detection value with a threshold; an assist amount correcting section to calculate an assist correction gain based on an assist continuation permissible time from said power voltage monitoring section; a multiplying section to multiply said steering assist command value by said assist correction gain; and a torque input processing section to input said steering torque and a switching signal from said power voltage monitoring section and to output said steering torque or an alternative value to said steering assist command value calculating section; wherein as said power voltage detection value becomes low, said assist continuation permissible time becomes short based on a drive possible characteristic of said FET; wherein an assist control is continued by multiplying said steering assist command value with said assist correction gain corresponding to characteristics of a voltage and a time; and wherein, when said power voltage monitoring section determines that said power voltage detection value drops and said dropped power voltage detection value becomes less than or equal to an assist operation possible power voltage, said power voltage monitoring section outputs said assist continuation permissible time based on said dropped power voltage detection value, and when said power voltage monitoring section determines that said power voltage detection value further drops and said further dropped power voltage detection value becomes less than or equal to a torque sensor minimum operation voltage, said power voltage monitoring section outputs said switching signal so that an input to said steering assist command value calculating section is switched from said steering torque to said alternative value. |
