State space feedback controller in the digital domain for an MRI gradient coil power supply

Patent metadata

Field	Value
Publication number	US-9541618-B2
Application number	US-201113995505-A
Country	US
Kind code	B2
Filing date	Dec 15, 2011
Priority date	Dec 20, 2010
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A state space feedback controller operates in the digital domain for the regulation of the current supply to MRI gradient coils from a multiple-bridge PWM power amplifier. The P1-controller includes an integration part (for the integration of the difference between the demand current and the measured gradient coil current) and a subsequent P-controlled system which in turn includes a delay compensator/stabilizer and a plant. The delay compensator/stabilizer includes a multi-path feedback loop by means of which its digital output signal is fed back through delay blocks, on the one hand, and through filter units, on the other hand. The filter units model the transfer functions of a gradient coil output filter for the gradient coil voltage and the output current of the amplifier inverter units, respectively. In the plant, a filter unit, which models the gradient coil transfer function, is connected in series to a delay chain for the delay of the measurement value of the gradient coil current.

First claim

The invention claimed is:

1. A method for operating an MRI gradient magnet system for generating gradient magnetic fields, by driving gradient coil currents through gradient coils of the gradient magnet system, wherein the gradient coil currents are controlled by a controller which is realized in the form of a state space feedback controller in the digital domain and which generates a digital output value by means of which a pulse-width modulated voltage is generated for driving the gradient coil currents through the gradient coils with a predetermined waveform wherein a control deviation is integrated which is generated in the form of a difference between the gradient coil current and a reference current,
the digital output value (u) is generated from the integrated control deviation, for delay compensation, and
the digital output value (u) is fed back and delayed by one clock cycle, two clock cycles, and three clock cycles and then subtracted from the digital output value (u).

2. A digital amplifier system for operating an MRI gradient magnet system for generating gradient magnetic fields, by driving gradient coil currents through gradient coils (GC) of the gradient magnet system, wherein the amplifier system comprises a digital controller (Con) for controlling the gradient coil currents, which controller (Con) is realized in the form of a state space feedback controller in the digital domain for generating a digital output value (u) by means of which a pulse-width modulated voltage is generated for driving the gradient coil currents through the gradient coils with a predetermined waveform,
wherein the controller (Con) comprises an integration part (GI) for integrating a control deviation which is generated in the form of a difference between the gradient coil current and a reference current,
wherein the controller (Con) comprises a delay compensator (G STAB ) for generating the digital output value (u) from the integrated control deviation, and
wherein the delay compensator (G STAB ) comprises a feedback loop by means of which the digital output value (u) is fed back and delayed by one, two and three clock cycles and then subtracted from the digital output value (u).

3. The digital amplifier system according to claim 2 , wherein the delay compensator (G STAB ) comprises a feedback loop by means of which the digital output value (u) is fed back via a transfer function (G UC , G IC ) of a gradient coil output filter (F) for a gradient coil voltage (u C ) and an output current (i C ) and then subtracted from the digital output value (u).

4. The digital amplifier system according to claim 2 , wherein the controller (Con) comprises a transfer function (GGC) in series to a delay chain for the measurement value of the gradient coil current (i GC ) of an A/D converter (A/D), by means of both of which the gradient coil current is generated from the digital output value (u).

5. A digital amplifier system for a magnetic resonance gradient magnet system which includes gradient coils configured to generate gradient magnetic fields in response to driving gradient coil currents, the amplifier system comprising:
a digital controller configured to control the gradient coil currents, the digital controller including a state space feedback controller in a digital domain configured to generate a digital output value for generating a pulse-width modulated voltage for driving the gradient coil currents through the gradient coils with a predetermined waveform;
the digital controller further including an integration circuit configured to integrate a control deviation, the control deviation being generated from a difference between the gradient coil current and a reference current;
the digital controller further including a delay compensation circuit configured to generate the digital output value from the integrated control deviation; and
the delay compensator includes a feedback loop configured to delay the digital output value by one, two, and three clock cycles and subtract the digital output signal delayed by one, two, and three clock cycles from the current digital output value.

Assignees

• Scheel Thomas
• Hattrup Christian
• Koninl Philips Electronics Nv

Inventors

• Scheel Thomas
• Hattrup Christian

Classifications

• G01R33/3852 Primary

  Gradient amplifiers; means for controlling the application of a gradient magnetic field to the sample, e.g. a gradient signal synthesizer · CPC title