Method of inverter linearization in electric machines through secondary modulation

A method for applying a voltage command signal within a brushless motor controller, the method comprising:

• determining a desired voltage command signal from a torque command signal and a motor speed signal;
• determining a phase advancing angle from said torque command signal and said motor speed signal;
• determining whether a magnitude of said desired voltage command signal falls between a first value and a second value;
• if said magnitude of said desired voltage command signal falls between said first value and said second value, then modulating a voltage command signal between said first and said second value over a determined sample period;
• and
• generating a set of motor duty cycle commands to be applied to an inverter coupled to said motor, said motor duty cycle commands being generated from a motor position signal, said phase advancing angle and said voltage command signal modulated, regardless of whether said voltage command signal is modulated or not.

An electric power steering system, comprising:

• a steering input device coupled to one or more steerable wheels;
• an assist actuator including an electric motor for providing an assist torque to said one or more steerable wheels, said motor further including an inverter for applying a series of phase voltages thereto;
• and
• a controller for generating a set of control signals to be applied to said inverter, said controller further comprising:
• means for receiving a desired voltage command to be applied to said motor;
• means for determining whether a magnitude of said desired voltage command falls between a first value and a second value;
• and
• means for modulating a voltage command between said first and said second value over a determined sample period if said controller determines that said magnitude of said desired voltage command falls between said first value and said second value, thereby resulting in an application of a modulated voltage command to said motor.

A storage medium, comprising:

• a machine readable computer program code for applying a voltage command signal within a brushless motor controller;
• and
• instructions for causing a computer to implement a method, the method further comprising:
• determining a desired voltage command signal from a torque command signal and a motor speed signal;
• determining a phase advancing angle from said torque command signal and said motor speed signal;
• determining whether a magnitude of said desired voltage command signal falls between a first value and a second value;
• if said magnitude of said desired voltage command signal falls between said first value and said second value, then modulating a voltage command signal between said first and said second value over a determined sample period;
• and
• generating a set of motor duty cycle commands to be applied to an inverter coupled to said motor, said motor duty cycle commands being generated from a motor position signal, said phase advancing angle and said voltage command signal, regardless of whether said voltage command signal is modulated or not.

A computer data signal, comprising:

• code configured to cause a processor to implement a method for applying a voltage command signal within a brushless motor controller, the method further comprising:
• determining a desired voltage command signal from a torque command signal and a motor speed signal;
• determining a phase advancing angle from said torque command signal and said motor speed signal;
• determining whether a magnitude of said desired voltage command signal falls between a first value and a second value;
• if said magnitude of said desired voltage command signal falls between said first value and said second value, then modulating a voltage command signal between said first and said second value over a determined sample period;
• and
• generating a set of motor duty cycle commands to be applied to an inverter coupled to said motor, said motor duty cycle commands being generated from a motor position signal, said phase advancing angle and said voltage command signal, regardless of whether said voltage command signal is modulated or not.