Nonlinear motor control techniques

1. A method of controlling a high-speed servomotor to attain optimal performance and stability margins across an operational range encompassing the entire torque versus speed curve of the servomotor, comprising:

partitioning the servomotor's torque versus speed curve into operating regions;

calculating a set of control parameters for each operating region;

storing the control parameters for each operating region in a look-up table;

selecting control parameters from the look-up table based on the current operating region of the servomotor; and

utilizing various multi-input multi-output controller functions optimized for the current operating region on various harmonic and fundamental components of a feedback signal to produce an output voltage command for controlling the servomotor.

2. The method of claim 1 , wherein selection of the control parameters is based on electrical current and speed.

3. The method of claim 1 , wherein the feedback signal is decomposed through the use of a transform to produce the various harmonic and fundamental components.

4. The method of claim 3 , wherein the transform used to decompose the feedback signal is a fast Fourier transform.

5. The method of claim 3 , wherein the transform used to decompose the feedback signal is a wavelet transform.

6. The method of claim 1 , further comprising utilizing a loop transfer recovery to increase controller robustness, wherein loop transfer recovery includes:

increasing the spectral density of a fictitious noise disturbance at the control output until acceptable robustness properties are obtained;

identifying a set of control parameters at the acceptable robustness level; and

creating a new current controller with suboptimal performance based on the identified control parameters.

7. The method of claim 1 , wherein the set of control parameters include at least one parameter selected from a group including:

quadrature axis voltage (V);

quadrature axis current (A);

axis stator resistance (Ω);

quadrature axis inductance (H);

electrical speed (rad/s);

rotor magnet flux linkage (V·s/rad);

direct axis voltage (V);

direct axis current (A); and

direct axis inductance (H).

8. A method of controlling a servomotor to enhance torque loop response time, minimize current ripple, and improve torque output for a given motor size, comprising:

obtaining a feedback current measurement;

converting the feedback current measurement into a digital signal;

decomposing the feedback current measurement into various harmonic and fundamental components through a transform function;

transforming the harmonic components into a dq reference frame via reverse transformation;

controlling each of the various harmonic and fundamental components each with a separate multi-input multi-output current controller to produce a control output for each component;

converting the control output for each component back into the proper reference frame via forward transformation;

aggregating the individual control output for each component into a single control output in the form of a voltage command to an inverter; and

operating the servomotor according to the aggregated control output.

9. The method of claim 8 , wherein the transform used to decompose the feedback current measurement is a fast Fourier transform.

10. The method of claim 8 , wherein the transform used to decompose the feedback current measurement is a wavelet transform.

11. The method of claim 8 , further comprising the use of loop transfer recovery to maintain operational robustness of the servomotor.

12. The method of claim 10 , wherein loop transfer recovery includes:

increasing the spectral density of fictitious noise disturbance at the control output until acceptable robustness properties are obtained;

identifying a set of control parameters at the acceptable robustness level; and

creating a new current controller with suboptimal performance based on the identified control parameters.

13. A system for controlling a high-speed servomotor to attain optimal performance and stability margins across an operational range encompassing the entire torque speed curve of the servomotor, comprising:

an AC synchronous or a brushless DC servomotor;

a power supply; and

a motor controller, comprising:

an analog to digital converter;

a digital to analog converter;

a memory, wherein the memory includes:

control parameters for the operational range, the operational range divided into a plurality of operating regions, each operating region assigned a look-up table, wherein, the operating regions are defined by partitioning the servomotor's torque versus speed curve based on a specified speed range; and

various multi-input multi-output controller functions optimized for the current operating region; and

a processor, wherein the processor is operable to:

select control parameters and controller functions from the look-up table based on the current operating region of the servomotor; and

utilize the various multi-input multi-output controller functions on various harmonic and fundamental components of a feedback signal to produce an output voltage command for controlling the servomotor.

14. The system of claim 13 , wherein selection of the control parameters and controller functions is based on electrical current and speed.

15. The system of claim 13 , wherein the processor decomposes the feedback signal through the use of a transform to produce the various harmonic and fundamental components.

16. The system of claim 15 , wherein the transform used to decompose the feedback signal is a fast Fourier transform.

17. The system of claim 15 , wherein the transform used to decompose the feedback signal is a wavelet transform.

18. The system of claim 13 , wherein the processor is further operatable to utilize a loop transfer recovery to increase controller robustness.

19. The system of claim 13 , wherein the set of control parameters include at least one parameter selected from a group including:

quadrature axis voltage (V);

quadrature axis current (A);

axis stator resistance (Ω);

quadrature axis inductance (H);

electrical speed (rad/s);

rotor magnet flux linkage (V·s/rad);

direct axis voltage (V);

direct axis current (A); and

direct axis inductance (H).

20. A servomotor controller for linearizing control of a servomotor over the entire operational ranges of the torque versus speed curve, comprising:

a analog to digital converter;

a digital to analog converter;

a memory, wherein the memory includes:

control parameters for the operational range divided into a plurality of operating regions, a look-up table provided for each operating region, wherein, the operating regions are defined by partitioning the servomotor's torque versus speed curve based on a specified speed range; and

various multi-input multi-output controller functions optimized for the current operating region; and

a processor, wherein the processor is operable to:

monitor various servomotor indices including electrical current and speed to determine the servomotor's present operating region;

retrieve control parameters and controller functions based on the servomotor's current operating region from the look-up table;

select an appropriate multi-input multi-output current control function optimized for the current operating region;

calculate a control gain for the current operating region utilizing the multi-input multi-output current control function selected for the current operating region; and

operate the servomotor according to the optimal control gain for the current operating region.

21. A system for controlling a servomotor to attain optimal performance and stability margins across an operational range encompassing the entire torque versus speed curve of the servomotor, comprising:

a AC synchronous or brushless DC servomotor; and

a motor controller which includes:

a memory, wherein the memory includes:

control parameters for a plurality of operating regions in a look-up table, wherein, the operating regions are defined by partitioning the servomotor's torque versus speed curve based on a specified speed range; and

various multi-input multi-output controller functions optimized for each operating region;

a processor, wherein the processor includes:

a means for monitoring an electrical current index and a speed index of the servomotor;

a means for selecting control parameters from the look-up table based on the current operating region of the servomotor; and

a means for utilizing the various multi-input multi-output controller functions on various harmonic and fundamental components of a feedback signal to produce an output voltage command for controlling the servomotor.