Electric power steering apparatus

An electric power steering apparatus located on a vehicle that calculates a current command value based on a steering torque detected by a torque sensor and a velocity and provides a steering system with an assist torque generated by an assist torque motor based on said current command value, comprising:

• said torque sensor and said assist torque motor both physically connected to a processor;
• said processor including:
• an end hitting detector:
• that detects end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque, and
• that outputs an end hitting detection signal,
• wherein said end hitting detector further comprises:
• a first comparator that detects that said steering torque exceeds a given steering torque value and outputs a detection signal 1;
• a second comparator that detects that said differential steering torque exceeds a given differential steering torque value and outputs a detection signal 2;
• a sign determiner that determines that signs of said steering torque and said differential steering torque are the same and outputs a determination signal;
• and
• an outputter that outputs said end hitting detection signal when said determination signal is outputted;
• a counter that counts a number 1 of times of end hitting detected by said end hitting detector;
• a memory that stores and keeps a total number of times of end hitting;
• and
• a current limit value calculator that calculates a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting from said counter and said total number of times of end hitting from said memory,
• wherein said current command value is limited based on said current limit value calculated by said current limit value calculator.

An electric power steering apparatus located on a vehicle that calculates a current command value based on a steering torque detected by a torque sensor and a velocity and provides a steering system with an assist torque generated by an assist torque motor based on said current command value, comprising:

• said torque sensor and said assist torque motor both physically connected to a processor;
• said processor including:
• an end hitting detector:
• that detects end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque, and
• that outputs an end hitting detection signal;
• a counter that counts a number 1 of times of end hitting detected by said end hitting detector;
• a memory that stores and keeps a total number of times of end hitting;
• and
• a current limit value calculator that calculates a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting from said counter and said total number of times of end hitting from said memory,
• wherein an output characteristic of said current limit value calculator is constant before said number 2 of times of end hitting reaches a given value 2, and gradually becomes a nonlinearly small value when said number 2 of times of end hitting exceeds said given value 2, and
• wherein said current command value is limited based on said current limit value calculated by said current limit value calculator.

An electric power steering apparatus located on a vehicle that calculates a current command value based on a steering torque detected by a torque sensor and a velocity and provides a steering system with an assist torque generated by an assist torque motor based on said current command value, comprising:

• said torque sensor and said assist torque motor both physically connected to a processor;
• said processor including:
• an end hitting detector:
• that detects end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque, and
• that outputs an end hitting detection signal;
• a counter that counts a number 1 of times of end hitting detected by said end hitting detector;
• a memory that stores and keeps a total number of times of end hitting;
• and
• a current limit value calculator that calculates a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting from said counter and said total number of times of end hitting from said memory,
• wherein an output characteristic of said current limit value calculator is constant before said number 2 of times of end hitting reaches a given value 3, decreases to a constant value 1 in a staircase pattern when said number 2 of times of end hitting is within a range of said given value 3 to a given value 4 (said given value 4>said given value 3 holds), and decreases to a constant value 2 (said constant value 2<said constant value 1 holds) in a staircase pattern when said number 2 of times of end hitting exceeds said given value 4, and
• wherein said current command value is limited based on said current limit value calculated by said current limit value calculator.

An electric power steering apparatus located on a vehicle that calculates a current command value based on a steering torque detected by a torque sensor and a velocity and provides a steering system with an assist torque generated by an assist torque motor based on said current command value, comprising:

• said torque sensor and said assist torque motor both physically connected to a processor;
• said processor including:
• an end hitting detector:
• that detects end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque, and
• that outputs an end hitting detection signal;
• a counter that counts a number 1 of times of end hitting detected by said end hitting detector;
• a memory that stores and keeps a total number of times of end hitting;
• and
• a current limit value calculator that calculates a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting from said counter and said total number of times of end hitting from said memory,
• wherein an output characteristic of said current limit value calculator decreases to a constant value 3 in a staircase pattern when said number 2 of times of end hitting exceeds a given value 5, and
• wherein said current command value is limited based on said current limit value calculated by said current limit value calculator.

An electric power steering apparatus located on a vehicle that calculates a current command value based on a steering torque detected by a torque sensor and a velocity and provides a steering system with an assist torque generated by an assist torque motor based on said current command value, the apparatus comprising:

• said torque sensor and said assist torque motor both physically connected to a processor;
• a memory configured to store a plurality of software instructions physically connected to said processor;
• and
• said processor configured to execute said plurality of software instructions, said plurality of software instructions comprising:
• detecting end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque;
• outputting an end hitting detection signal;
• counting a number 1 of times of end hitting detected;
• storing a total number of times of end hitting;
• and
• calculating a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting and said total number of times of end hitting,
• wherein an output characteristic of said calculated current limit value is constant before said number 2 of times of end hitting reaches a given value 1, and gradually becomes a linearly small value when said number 2 of times of end hitting exceeds said given value 1, and
• wherein a current command value is limited based on said calculated current limit value.

A method of calculating a current command value for an electric power steering apparatus located on a vehicle based on a steering torque detected by a torque sensor and a velocity, the method comprising:

• detecting steering torque by said torque sensor that is physically connected to a processor;
• detecting, by said processor, end hitting based on said steering torque and a differential steering torque obtained by differentiating said steering torque;
• outputting an end hitting detection signal;
• counting, by said processor, a number 1 of times of end hitting detected;
• storing, in a memory that is physically connected to said processor, a total number of times of end hitting;
• calculating, by said processor, a current limit value depending on a number 2 of times of end hitting obtained by adding said number 1 of times of end hitting and said total number of times of end hitting,
• wherein an output characteristic of said calculated current limit value is constant before said number 2 of times of end hitting reaches a given value 1, and gradually becomes a linearly small value when said number 2 of times of end hitting exceeds said given value 1, and
• wherein a current command value is limited based on said calculated current limit value;
• and
• providing a steering system with an assist torque generated by a motor based on said current command value.