Inductive Consumer Current Control via Internal Model Feedback
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Solution Overview
Problem
Existing methods for controlling the amperage of electric current through inductive consumers, such as solenoid valves in motor vehicles, face inaccuracies due to hysteresis-like behavior caused by self-induction, making precise current intensity setting difficult.
Innovation Solution
The method employs an Internal Model Control (IMC) approach, where a first controller determines the average load voltage and a second controller sets the target current level, using a model of the consumer to regulate current intensity, and an inverted transfer function to determine the superimposed current, thereby simplifying parameterization and reducing application effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse width modulation is used to control current intensity, then the consumer can be actuated with adjustable current levels, but hysteresis-like behavior due to self-induction causes inaccuracies in current intensity setting
Solution Approach 1:
The patent implements a feedback control mechanism where the actual current flowing through the inductive consumer is continuously measured and compared with the desired current. Based on this comparison, the control device adjusts the pulse width modulation duty factor dynamically to compensate for hysteresis effects and achieve accurate current intensity setting despite the inductive behavior of the load.
Solution Approach 2:
The control device calculates the required pulse duty factor in advance based on the desired current intensity and the measured actual current. By determining the appropriate duty factor before applying the pulse signal, the system can preemptively compensate for the hysteresis-like behavior caused by self-induction, ensuring more accurate current control.
2Ease of operation
If the switching device is used to apply or interrupt power supply, then current intensity can be controlled, but voltage jumps and overvoltages can damage the inductive consumer
Solution Approach 1:
The patent introduces a freewheeling element (such as a diode) connected in parallel with the inductive consumer. This intermediary component provides a safe path for the inductive current when the switching device interrupts the power supply, preventing voltage spikes and overvoltages that would otherwise damage the consumer. The freewheeling element acts as a mediator between the switching device and the inductive load.
Solution Approach 2:
The control device monitors the current and switching state to anticipate potential overvoltage conditions. By controlling the switching timing and duty factor appropriately, and ensuring the freewheeling path is available, the system cushions against voltage jumps before they can cause damage to the inductive consumer.
3Device complexity
If conventional control methods are used, then the system is simple to implement, but parameterization is complex and application effort is high due to hysteresis compensation requirements
Solution Approach 1:
The control device automatically determines the pulse duty factor based on real-time measurements of the actual current and the desired current, without requiring manual parameterization or tuning. The system self-adjusts to compensate for hysteresis effects and adapts to varying operating conditions, eliminating the need for complex parameter settings and reducing application effort.
Solution Approach 2:
The patent dynamically changes the pulse duty factor parameter based on the measured actual current and desired current. Instead of using fixed parameters that require complex tuning, the system continuously adjusts the duty factor to achieve accurate current control, simplifying the implementation while maintaining precision.
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
This approach allows for more accurate regulation of current intensity, reducing the influence of dynamic disturbances in the supply voltage and ensuring stable control, while minimizing the risk of damage from voltage jumps.
Implementation Method 1
The freewheeling element is used in particular to protect the consumer from overvoltages, which can occur when the power supply to the inductive consumer is interrupted by means of the switching device, primarily as a result of self-induction.
Data Source
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AI summary
The invention relates to a method for the closed-loop control of the current intensity (Iact) of the electrical current flowing through an inductive consumer (3), wherein the consumer is connected in series with a switching apparatus (5) and a current measurement device (4) and is connected in parallel with a freewheeling element (7), and the switching apparatus (5) is actuated for adjusting the current intensity (Iact) during a pulse width modulation period. Provision is made here for a mean load voltage (UmL) to be set during the pulse width modulation period to be determined from an input current intensity (IE) by means of a first controller (13), which mean load voltage is set in the pulse width modulation period by means of the switching apparatus (5) at the consumer (3), wherein the mean load voltage (UmL) or a setpoint load voltage (UsL) determined by means of a second controller (22) from a predetermined setpoint current intensity (Iset) is supplied to a model (15) matched to the consumer (3), and wherein the input current intensity (IE) is determined from the difference between the predetermined setpoint current intensity (Iset) and a differential variable (ΔI) between an actual current intensity (Iact) through the consumer (3) and a model current intensity (Imodel) determined by means of the model (15). The invention furthermore relates to a circuit arrangement (1).