Shunt Resistor Current Detection for Precise Steering Inverter Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric steering systems, inaccuracies in detecting steering assist current due to errors between driving and actual steering assist currents lead to unintended steering torque and vibrations, affecting control precision.
Innovation Solution
An electronic control device using a shunt resistor and current detection circuit, incorporating an operational amplifier and parasitic resistor, to determine steering assist current values based on input/output relational expressions, allowing precise control of the inverter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple current detection method is used, then device complexity is reduced, but measurement precision of steering assist current deteriorates
Solution Approach 1:
The patent introduces a shunt resistor as an intermediary component to convert the steering assist current into a measurable voltage signal. This mediator enables indirect measurement of current through voltage detection, achieving high measurement precision while keeping the detection circuit relatively simple. The shunt resistor Rs is connected in series with the steering motor, and the voltage across it is amplified by an operational amplifier to obtain the steering assist current value.
2Device complexity
If parasitic resistance is not compensated, then device complexity is reduced, but measurement precision deteriorates due to ground potential differences
Solution Approach 1:
The patent applies preliminary anti-action by measuring and compensating for the parasitic resistance voltage drop before it affects the final current measurement. The system separately measures the voltage across the parasitic resistor Rg (between the shunt resistor ground terminal and actual ground) and subtracts this offset voltage from the total measurement. This pre-compensation approach eliminates measurement errors caused by ground potential differences, ensuring high measurement precision without requiring complex real-time adjustment circuits.
3Ease of operation
If driving current is used as approximation, then ease of operation is improved, but reliability of control deteriorates
Solution Approach 1:
The patent implements feedback by continuously detecting the actual steering assist current flowing through the steering motor and using this detected value to control the inverter output. The current detection circuit measures the actual current in real-time, and the controller adjusts the inverter's PWM duty cycle based on this feedback to maintain the desired current. This closed-loop feedback mechanism ensures high reliability of steering control by constantly comparing and adjusting based on actual motor current conditions.
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
Accurate determination of steering assist current values enables precise control of the steering motor, minimizing unintended torque and vibrations, thereby enhancing system performance.
Implementation Method 1
a shunt resistor Rs connected between the inverter and a ground to form a steering assist voltage V corresponding to the steering assist current I
Implementation Method 2
a current detection circuit including an operational amplifier for amplifying and outputting the steering assist voltage V
Data Source
AI summary
According to present embodiments, it is possible to accurately control an inverter by determining a steering assist current value from a steering assist voltage value based on an input/output relational expression of an operational amplifier and a resistance values of the shunt resistor and a parasitic resistor.