Apparatus and method for estimation of initial phase of a brushless motor

A method for estimating an a priori unknown initial phase of a rotor with respect to a stator, wherein the rotor and the stator are parts of a synchronous motor that is not equipped with a capability to directly measure the absolute phase of the rotor with respect to the stator, the method comprising:

• applying to the motor an electric drive signal according to a predetermined oscillating function of time, so as to cause a sequence of displacements of the rotor with respect to the stator;
• collecting data from the motor in response to the electric drive signal;
• performing mathematical computations on the basis of the collected data and a model of dynamic behavior of the motor;
• and
• estimating the initial phase of the rotor with respect to the stator based on the mathematical computations.

A method for estimating an a priori unknown initial phase of a rotor with respect to a stator, wherein the rotor and the stator are parts of a synchronous motor that is not equipped with a capability to directly measure the absolute phase of the rotor with respect to the stator, wherein the dynamic behavior of the motor is modeled by a mathematical model that relates data observable from the motor to the initial phase, the mathematical model characterized by one or more degrees of freedom, the method comprising:

• applying to the motor a plurality of electric drive signals, wherein each electric drive signal is a function of one or more of said one or more degrees of freedom, and each electric drive signal is characterized by a different set of values chosen for said one or more degrees of freedom;
• collecting data from the motor in response to the electric drive signals;
• performing mathematical computations on the basis of the collected data and a model of dynamic behavior of the motor;
• and
• estimating the initial phase of the rotor with respect to the stator based on the mathematical computations.

A system for estimating the initial phase of a brushless motor having a rotor and a stator, and electrical terminals accepting an electric drive signal, the motor characterized by an a priori unknown initial phase of the rotor with respect to the stator, the system comprising:

• a means, connected to the electrical terminals, for producing the electric drive signal;
• a means for measuring an incremental position change of the rotor with respect to the stator and for producing an output signal indicative of the position change;
• a means for causing the driver to produce the electric drive signal according to a predetermined function of time,
• a means for observing the output signal from the position sensor resulting from the electric drive signal, and
• a means for performing mathematical computations on the basis of the observed output signal and a model of dynamic behavior of the motor to estimate the initial phase of the rotor with respect to the stator.