Self tuning method and apparatus for permanent magnet sensorless control

Claim 3

The method of claim 1 , wherein the saliency of the PMSM is negligible and q and d axis inductances are equal to a PMSM inductance L and the regulated DC motor currents i q(ref) =I park and i d(ref) are equal to 0.

Claim 4

The method of claim 1 , wherein when stator current is regulated at 0, the applied quadrature voltage is equal to the Electro Motive Force (EMF).

Claim 5

The method of claim 3 , further comprising a step of calculating an electrical constant K E of the PMSM based on the measured values of the quadrature voltage and free motor speed as k E = V q ω freewheel .

Claim 6

The method of claim 4 , wherein the electrical constant of the PMSM is equal to (p·λ), where λ is an amplitude of a flux induced by the permanent magnets of the rotor in stator phases and p is a number of pole pairs.

Claim 7

The method of claim 5 , wherein the step of calculating of the load inertia is based on the measured total acceleration time as J = 1.5 · p · λ · I acc · t accelerate ω target .

Claim 8

The method of claim 1 , further comprising a step of filtering the applied quadrature voltage to attenuate noise.

Claim 9

The method of claim 1 , further comprising a step of waiting for a period of time after the regulated DC currents and applied before parking the PMSM.

Claim 10

The method of claim 1 , wherein the stator resistance R during the parking step is calculated as R=v q /I park based on the measured value of the quadrature voltage.

Claim 11

The method of claim 9 , the PMSM inductance is calculated based on the known time constant as T s ·R=L where R is the stator resistance.

Claim 12

The method of claim 1 , further comprising a step of estimating a friction coefficient F once a constant motor speed ω steady corresponding to a steady current i q =I steady is reached in the accelerating step.

Claim 13

The method of claim 11 , wherein the friction coefficient is calculated as F = 1.5 · p · λ · I steady · 1 ω steady .

Claim 14

The method of claim 11 , further comprising a step of correcting the calculation of the friction coefficient given as J = 1.5 · p · λ · I acc · t accelerate ω target by a factor of - F ω target accelerate ⁢ ∫ ω r ⁢ ⅆ t .

Claim 17

A controller for performing a Pulse Width Modulation (PWM) drive of a Permanent Magnet Synchronous Motor (PMSM) and for determining PMSM parameters to differentiate between a plurality of PMSMs, the controller comprising: an outer speed loop for setting the desired speed of the PMSM; a first inner current loop for regulating a quadrature component i q of the motor current; a second inner current loop for regulating a direct component i d of the motor current, the motor current i d being the equivalent motor stator current projected onto a d-axis aligned with a rotor field, and the motor current i q being the equivalent motor stator current projected on a q-axis, which is perpendicular to the rotor field; and a speed observer circuit having an input of voltages v α and v β and currents i α and i β and outputting an angular position of a rotor θ r and an observed rotor speed ω obs , wherein each of the loops includes a compensator, whose parameters can be adjusted based on measured motor parameters, further comprising a processor for measuring the motor parameters that implements the steps of determining a plurality of parameters of a Permanent Magnet Synchronous Motor (PMSM) by a motor controller to differentiate between a plurality of PMSMs, the method comprising the steps of: applying regulated DC motor currents at a commanded fixed rotor angle; measuring a quadrature voltage v q after an initial transient has elapsed, the quadrature voltage being applied across the PMSM windings; parking the PMSM at standstill, whereby the quadrature voltage is proportional to a stator resistance and to the applied park current I park ; selecting an initial set of controller parameters; applying the quadrature voltage equal to zero; measuring a time constant T s corresponding to an exponential decay of a quadrature current i q ; accelerating the PMSM with a constant torque up to a preset target speed; measuring a total acceleration time t accelerate until the preset target speed ω target is reached; regulating a stator current at 0 value, whereby the stator current is at 0 value when currents i q(ref) and i d(ref) are both at zero value; measuring the quadrature voltage and a freewheeling motor speed ω freewheel immediately after applying the 0 stator current; calculating an electrical constant K E of the PMSM based on the measured values of the applied quadrature voltage and the freewheeling motor speed; calculating a load inertia J based on the previously measured total acceleration time; and calculating a set of parameters for the controller based on the determined motor parameters.

Claim 18

A controller for performing a Pulse Width Modulation (PWM) drive of a Permanent Magnet Synchronous Motor (PMSM) and for determining PMSM parameters to differentiate between a plurality of PMSMs, the controller comprising: an outer speed loop for setting the desired speed of the PMSM; a first inner current loop for regulating a quadrature component i q of the motor current; a second inner current loop for regulating a direct component i d of the motor current, the motor current i d being the equivalent motor stator current projected onto a d-axis aligned with a rotor field, and the motor current i q being the equivalent motor stator current projected on a q-axis, which is perpendicular to the rotor field; and a speed observer circuit having an input of voltages v α and v β and currents i α and i β and outputting an angular position of a rotor θ r and an observed rotor speed ω obs , wherein each of the loops includes a compensator, whose parameters can be adjusted based on measured motor parameters, further comprising a processor for measuring the motor parameters that implements the steps of determining a plurality of parameters of a Permanent Magnet Synchronous Motor (PMSM) by a motor controller to differentiate between a plurality of PMSMs, the method comprising the steps of: applying regulated DC motor currents at a commanded fixed rotor angle; measuring a quadrature voltage v q after an initial transient has elapsed, the quadrature voltage being applied across the PMSM windings; parking the PMSM at standstill, whereby the quadrature voltage is proportional to a stator resistance and to the applied park current I park ; selecting an initial set of controller parameters; applying the quadrature voltage equal to zero; measuring a time constant T s corresponding to an exponential decay of a quadrature current i q ; accelerating the PMSM with a constant torque up to a preset target speed; measuring a total acceleration time t accelerate until the preset target speed ω target is reached; regulating a stator current at 0 value, whereby the stator current is at 0 value when currents i q(ref) and i d(ref) are both at zero value; measuring the quadrature voltage and a freewheeling motor speed ω freewheel immediately after applying the 0 stator current; calculating an electrical constant K E of the PMSM based on the measured values of the applied quadrature voltage and the freewheeling motor speed; calculating a load inertia J based on the previously measured total acceleration time; and calculating a set of parameters for the controller based on the determined motor parameters.

Claim 19

The controller of claim 15 , wherein the controller operates on the Field Oriented Control (FOC) principle to regulate a speed of the PMSM.

Claim 20

The controller of claim 15 , wherein the inner current loops determine quadrature component i q of the motor current and the direct component i d of the motor current by (a) receiving gate pulse signals from each switch and the DC bus voltage supply current, (b) determining current values i a , i b and i c of PMSM windings, (c) performing a Clarke transformation [ i α i β ] = [ 1 0 0 0 1 3 - 1 3 ] ⁡ [ i A i B i C ] on the determined current values to determine current values i α and i β , (d) performing a Park transformation [ i d i q ] = [ cos ⁡ ( θ r ) sin ⁡ ( θ r ) - sin ⁡ ( θ r ) cos ⁡ ( θ r ) ] ⁡ [ i α i β ] on the current values i α and i β , to determine current values i q and i d , (e) converting the current values i q and i d into corresponding voltage values v q and v d , (f) performing a reverse Park transformation [ v α v β ] = [ cos ⁡ ( θ r ) - sin ⁡ ( θ r ) sin ⁡ ( θ r ) cos ⁡ ( θ r ) ] ⁡ [ v d v q ] on the voltage values v q and v d , to determine voltage values v α and v β , and (g) performing the reverse Clarke transformation [ v A v B v C ] = [ 1 0 - 0.5 3 2 - 0.5 - 3 2 ] ⁡ [ v α v β ] on the voltage values v α and v β , to determine voltages V a , V b , and V c required to drive the PMSM at the desired speed sets by the outer control loop.