Self tuning method and apparatus for permanent magnet sensorless control

• US 7,339,344 B2
• Filed: 07/21/2006
• Issued: 03/04/2008
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Borisavljevic, Ana
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US11/459,230
• Publication Number:
  US 20070046246A1
• Time in Patent Office: 592 Days
• Field of Search: 318/719, 318/721, 318/723, 318/808
• US Class Current: 318/723
• CPC Class Codes: H02P 21/16 Estimation of constants, e.g. the rotor time constant
• CPC Class Codes: H02P 21/18 Estimation of position or speed
• CPC Class Codes: H02P 21/26 Rotor flux based control
• CPC Class Codes: H02P 21/32 Determining the initial rotor position H02P21/34 takes precedence
• CPC Class Codes: H02P 6/20 Arrangements for starting H02P6/08 takes precedence

Abstract

A plurality of parameters of a Permanent Magnet Synchronous Motor (PMSM) is determined by a motor controller for differentiating between a plurality of PMSMs. This is achieved by first applying regulated DC motor currents at a commanded fixed rotor angle and measuring a quadrature voltage; parking the PMSM at standstill, Then, after selecting an initial set of controller parameters; applying the quadrature voltage equal to zero and measuring a time constant. Then, accelerating the PMSM with a constant torque up to a preset target speed and measuring a total acceleration time t_accelerate until the preset target speed ω_target is reached. After regulating a stator current at 0 value, measuring the quadrature voltage and a freewheeling motor speed ω_freewheel immediately after applying the 0 stator current; and calculating an electrical constant K_E of the PMSM; a load inertia J; and a set of parameters for the controller.

Claims

1. A method 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.

2. 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.

3. 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).

4. 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

$k_E=\frac{V_q}{{\omega }_{}}$

freewheel .

5. 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.

6. 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 .

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

8. 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.

9. 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.

10. 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.

11. 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.

12. The method of claim 11, wherein the friction coefficient is calculated as

$F=1.5·$

p ·

λ

·

I steady ·

1 ω

steady .

13. 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

$-\frac{F}{{\mathrm{\omega <br><br>}}_{{\mathrm{target}}_{\mathrm{accelerate}}}}<br><br>\int <br><br>{\mathrm{\omega <br><br>}}_r<br><br>d<br><br>t.$

14. A method of measuring 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:

performing a first stage by

applying regulated DC motor currents at a commanded fixed rotor angle, parking the PMSM at standstill, whereby a quadrature voltage applied across the PMSM windings is proportional to a stator resistance and to an applied park current, and

selecting an initial set of controller parameters;

performing a second stage by

applying the quadrature voltage equal to zero,

accelerating the PMSM with a constant torque up to a preset target speed in accordance with a time constant corresponding to an exponential decay of a quadrature current, and

regulating a stator current at 0 value using a total acceleration time to the preset target speed, which the stator current is at 0 value when regulated DC motor currents are at zero value; and

performing a third stage by calculating

an electrical constant of the PMSM based on the values of the applied quadrature voltage and a free motor speed immediately after applying the 0 stator current,

a load inertia based on the previously measured total acceleration time, and

a set of parameters for the controller based on the determined motor parameters.

15. 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.

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

17. 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

$[\begin{array}{c}{i}_{\alpha }\end{array}$

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

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\left[\begin{array}{cc}\cos <br><br>\left({\mathrm{\theta <br><br>}}_r\right)& \sin <br><br>\left({\mathrm{\theta <br><br>}}_r\right)\\ -\sin <br><br>\left({\mathrm{\theta <br><br>}}_r\right)& \cos <br><br>\left({\mathrm{\theta <br><br>}}_r\right)\end{array}\right]<br><br>\left[\begin{array}{c}{i}_{\mathrm{\alpha <br><br>}}\\ i_{\mathrm{\beta <br><br>}}\end{array}\right]$

 

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

$\left[\begin{array}{c}{v}_{\mathrm{\alpha <br><br>}}\\ v_{\mathrm{\beta <br><br>}}\end{array}\right]=\left[\begin{array}{cc}\cos <br><br>\left({\mathrm{\theta <br><br>}}_r\right)& -\sin <br><br>\left({\mathrm{\theta <br><br>}}_r\right)\\ \sin <br><br>\left({\mathrm{\theta <br><br>}}_r\right)& \cos <br><br>\left({\mathrm{\theta <br><br>}}_r\right)\end{array}\right]<br><br>\left[\begin{array}{c}{v}_d\\ v_q\end{array}\right]$

 

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

$\left[\begin{array}{c}{v}_A\\ v_B\\ v_C\end{array}\right]=\left[\begin{array}{cc}1& 0\\ -0.5& \frac{\sqrt{3}}{2}\\ -0.5& -\frac{\sqrt{3}}{2}\end{array}\right]<br><br>\left[\begin{array}{c}{v}_{\mathrm{\alpha <br><br>}}\\ v_{\mathrm{\beta <br><br>}}\end{array}\right]$

 

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.