Gradient Power Amplifier Control With Delay-Compensated PWM
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Solution Overview
Problem
Current state space controllers for gradient power amplifiers in MRI systems are complex and costly, affecting control efficiency due to their intricate structures and algorithms.
Innovation Solution
A simplified state space controller with a compact structure and reduced calculation parameters, utilizing an integral part and delay compensator to generate a PWM drive signal for precise control of gradient coil currents, achieving accurate gradient magnetic field generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional state space control technology is used in gradient power amplifiers, then control accuracy of gradient coil current is improved, but controller complexity and cost increase
Solution Approach 1:
The patent transforms the continuous state space control problem into a discrete event-driven control model by changing the parameter representation from continuous variables to discrete events occurring at specific time points. This allows maintaining control accuracy while reducing computational complexity through event-triggered updates rather than continuous calculation.
Solution Approach 2:
The patent replaces the traditional mechanical/computational control structure with an energy-based control approach. By using energy functions and power balance equations instead of conventional differential equation-based state space models, the controller achieves the same control objectives with simpler mathematical operations and reduced computational burden.
2Manufacturing precision
If traditional state space controllers are used, then gradient magnetic field control precision is improved, but calculation complexity increases
Solution Approach 1:
The patent changes the control parameters from continuous state variables requiring frequent calculation to discrete energy-based parameters that are updated only when specific events occur. This event-driven parameter update mechanism maintains gradient magnetic field control precision while significantly reducing calculation frequency and complexity.
Solution Approach 2:
The patent pre-calculates and stores optimal control parameters and energy relationships during system design and characterization phases. These pre-computed parameters are then directly applied during operation without requiring real-time complex calculations, thereby maintaining precision while reducing online computational complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient and robust control of gradient coil currents, reducing complexity and cost while maintaining accurate imaging requirements, as demonstrated by simulation results showing stable output current control within specified ranges.
Implementation Method 1
Gradient power amplifiers excite gradient coils to generate gradient currents to obtain gradient magnetic fields
Data Source
AI summary
A state space controller includes an integral part configured to integrate a control deviation, wherein the control deviation indicates a difference between a digital value of a gradient coil current and a reference current; a delay compensator configured to generate a digital control amount according to the integrated control deviation by the integral part, and generated a pulse-width modulation drive signal according to the digital control amount, and includes a subtractor of which a non-inverting input terminal is connected to an output terminal of the integral part, a delayer configured to delay the digital control amount by one calculation cycle, and a first feedback loop configured to delay the digital control amount by one calculation cycle and multiply a first compensation coefficient to obtain a first compensation amount, wherein the first compensation amount is input into a first inverting input terminal of the subtractor.