# US 10,863,919 B2 · Method and system for gradient power amplifier debugging

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- Number: US 10,863,919 B2
- Document ID: US10863919B2
- Status: Granted
- Kind: B2
- Application number: 16/313,154
- Filed: 2016-08-12
- Published: 2019-05-23
- Granted: 2020-12-15
- Earliest claimed: 2016-08-12
- Assignees: Shanghai United Imaging Healthcare Co., Ltd.
- Applicants: Shanghai United Imaging Healthcare Co., Ltd.
- Inventors: Mingyu Xue; Bin Cao; Xu Chu
- Web page: https://patentgrep.com/patent/US10863919B2

## CPC

- G01R 33/3852: {Gradient amplifiers; means for controlling the application of a gradient magnetic field to the sample, e.g. a gradient signal synthesizer}
- G01R 33/341: comprising surface coils
- G01R 33/385: using gradient magnetic field coils
- G01R 33/543: {Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence)}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

The present application discloses a gradient power amplifier debugging method and system. The method may comprise initializing a control unit of the gradient power amplifier debugging system; retrieving a characteristic output of the control unit; computing a load inductance parameter L according to the characteristic output; and adjusting the control parameter of the control unit according to the load inductance parameter L. The control unit may comprise a close-loop control sub-unit, or a feedforward control sub-unit. The characteristic output may be representative of the difference between an output signal and an input signal of the gradient power amplifier debugging system. The control parameter may comprise a proportional coefficient, an integral coefficient, or a cutoff frequency of the filter.

## Claims

### Claim 1

A control method for debugging a gradient power amplifier for driving a gradient coil of a magnetic resonance system, the gradient power amplifier comprising a control unit, which comprises: a close-loop control sub-unit configured to produce a characteristic output based on an input signal and an output signal of the gradient power amplifier; and a feedforward control sub-unit including a load model with load parameters related to the gradient coil, the method comprising:
initializing parameters of the close-loop control sub-unit and the feedforward control sub-unit with default values, wherein the load parameters are initialized to default load parameters;
retrieving a characteristic output of the close-loop sub unit, the characteristic output representing differences between the default load parameters and real load parameters;
computing the real load parameters according to the characteristic output of the close-loop sub unit; and
adjusting the parameters of the close-loop sub-unit and feedforward sub-unit according to the real load parameters.

### Claim 2

A gradient power amplifier, comprising:
a control unit, comprising a close-loop control sub-unit and a feedforward control sub-unit;
an initialization unit configured to initialize the control unit with default parameters, wherein the default parameters comprises default load parameter;
a data retrieval unit configured to retrieve a characteristic output of the close-loop control sub-unit, the characteristic output representing differences between the default load parameters and real load parameters;
a load parameter identification unit, configured to compute the real load parameters according to the characteristic output; and
a control parameter adjustment unit, configured to adjust the one or more control parameters of the control unit according to the computed real load parameter.

### Claim 3

A magnetic resonance system comprising:
a gradient coil configured to generate a gradient magnetic field;
a gradient power amplifier configured to drive the gradient coil;
a processor comprising:
a close-loop control sub-unit configured to produce a characteristic output based on an input signal and an output signal of the gradient power amplifier;
a feedforward control sub-unit including a load model with load parameters related to the gradient coil; and
a storage unit configured to store executable instructions which, when executed by the processor, causes the processor to implement:
retrieving a characteristic output of the close-loop control sub-unit, the characteristic output represents differences of between the default load parameters and the real load parameters;
computing the real load parameters according to the characteristic output of the close-loop control sub-unit; and
adjusting one or more control parameters of the control unit according to the real load parameter.

### Claim 4 (depends on 1)

The method of claim 1, wherein
the close-loop control sub-unit comprises at least a proportional integral (PI) controller or a proportional integral differential (PID) controller.

### Claim 5 (depends on 4)

The method of claim 4, wherein the characteristic output comprises at least an integral output of the close-loop control sub-unit.

### Claim 6 (depends on 1)

The method of claim 1, wherein the load model comprises at least a load inductance L and/or a load resistance R, and the difference between the default load parameters and real load parameters comprises:
a difference resistance ΔR between a default load resistance R of the load model and a real load resistance R′; and/or
a difference inductance ΔL between a default load inductance L of the load model and a real load inductance L′.

### Claim 7 (depends on 6)

The method of claim 6, wherein retrieving the characteristic output comprises:
retrieving a first characteristic output of the close-loop control unit when the gradient power amplifier outputs a pulse signal of a first amplitude; and
retrieving a second characteristic output of the close-loop control unit when the gradient power amplifier outputs a pulse signal of a second amplitude;
the first amplitude and the second amplitude are not lower than a first threshold, and the first threshold may be such that a difference between the first characteristic output and the second characteristic output is only dependent on the load resistance parameter R of the load model.

### Claim 8 (depends on 7)

The method of claim 7, wherein the load resistance parameter is obtained by the following method:
computing a difference resistance ΔR between the default load resistance parameter R of the load model and the real load resistance R′, according to the first characteristic output and the second characteristic output; and
adjusting the load resistance of the load model to ΔR+R, according to the difference resistance ΔR and the default load resistance R of the load model.

### Claim 9 (depends on 6)

The method of claim 6, wherein retrieving the characteristic output further comprises:
retrieving a third characteristic output of the closed-loop control unit when the gradient power amplifier outputs a pulse signal of a third amplitude, wherein the pulse signal of the third amplitude comprises a rising time of Tramp, and the rising time Tramp is not lower than a second threshold, such that a characteristic output in the rising time Tramp is only dependent on the load inductance L of the load model.

### Claim 10 (depends on 9)

The method of claim 9, wherein the load parameter comprises the load inductance, and the load inductance is obtained by the following method:
computing a difference inductance ΔL between the default load inductance L of the load model and the real load inductance L′, according to the third characteristic output and the rising time Tramp; and
adjusting the load inductance of the load model to ΔL+L, according to the difference inductance ΔL and the default load inductance L of the load model.

### Claim 11 (depends on 6)

The method of claim 6, wherein the close-loop control sub-unit comprises at least a proportional integral (PI) controller, the parameters of the closed-loop control sub-unit comprises control parameters, and the control parameters comprise a proportional coefficient Kp and an integral coefficient Ki of a PI controller.

### Claim 12 (depends on 11)

The method of claim 11, wherein adjusting the control parameters of the closed-loop control sub unit comprises adjusting a value of the proportional coefficient Kp to αL, wherein α is a constant.

### Claim 13 (depends on 11)

The method of claim 11, wherein adjusting the control parameters of the closed-loop control sub unit further comprises adjusting a value of the integral coefficient Ki to βL′, wherein β is a constant.

### Claim 14 (depends on 4)

The method of claim 4, wherein the close-loop control sub-unit further comprises a first digital low-pass filter.

### Claim 15 (depends on 11)

The method of claim 11, wherein adjusting the control parameters of the closed-loop control sub unit comprises:
comparing the real load inductance L′ to a threshold;
adjusting the proportional coefficient Kp to α1L′ and the integral coefficient Ki to β1L′, if the real load inductance L′ is lower than the threshold, wherein α1 is a constant, and β1 is a constant; and
adjusting the proportional coefficient Kp to α2L′ and the integral coefficient Ki to β2L′, if the real load inductance L′ is higher than the threshold, wherein α2 is a constant, and β2 is a constant.

### Claim 16 (depends on 15)

The method of claim 15, wherein the initializing comprises initializing a cutoff frequency of the first digital low-pass filter to an initial cutoff frequency.

### Claim 17 (depends on 16)

The method of claim 16, wherein adjusting the parameters of the close-loop control sub-unit comprises:
comparing the real load inductance L′ to a threshold;
adjusting the cutoff frequency of the first digital low-pass filter to a first cutoff frequency, if the real load inductance L′ is lower than the threshold; and
adjusting the cutoff frequency of the first digital low-pass filter to a second cutoff frequency, if the real load inductance L′ is higher than the threshold.

### Claim 18 (depends on 17)

The method of claim 17, wherein the first cutoff frequency or the second cutoff frequency equals to the initial cutoff frequency.

### Claim 19 (depends on 11)

The method of claim 11, wherein the close-loop control sub-unit comprises a second and a third digital low-pass filter with their specific cutoff frequency, and adjusting the control parameters of the control unit comprises:
comparing the real load inductance L′ to a threshold; and
switching between the second digital low-pass filter and the third digital low-pass filter according to the result of the comparison.

### Claim 20 (depends on 3)

The system of claim 3, further comprising a first digital low-pass filter and a second digital low-pass filter, wherein when executed by the processor, the executable instructions further cause the processor to implement:
comparing the real load parameter to a threshold; and
switching between the first digital low-pass filter and the second digital low-pass filter based on a result of the comparison.