Digital NOx Sensor Control System for Rapid Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current NOx sensors rely on analog circuitry, which takes 20-60 seconds to heat up and can cause EMI/EMC issues and feedback loop instability, necessitating a faster and more reliable digital solution for excitation and current control.
Innovation Solution
A fully digital NOx sensor control system that includes an analog front-end for signal conversion, a processing system to control the heater element current, and a temperature sensor for rapid temperature monitoring, allowing for quick temperature attainment without EMI/EMC issues, using a microcontroller and digital potentiometer for precise current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If analog circuitry is used to process sensor signals and control heater current, then the system is simpler in design, but the heating time increases to 20-60 seconds and EMI/EMC issues occur
Solution Approach 1:
The patent replaces analog circuitry with a digital control system consisting of a microcontroller, digital-to-analog converter, and pulse width modulation circuitry. This substitution enables precise digital control of heater current while reducing heating time from 20-60 seconds to 5-10 seconds, and eliminates EMI/EMC issues associated with traditional analog pulsed current control.
2Speed
If pulsed current is used to heat the NOx sensor, then heating speed increases, but EMI/EMC issues are caused
Solution Approach 1:
The patent employs pulse width modulation (PWM) technique to deliver periodic current pulses to the heater element. The microcontroller adjusts the duty cycle of these pulses to control heating rate while maintaining average current levels. This periodic action achieves fast heating (5-10 seconds) while the controlled pulse timing prevents the EMI/EMC interference problems associated with uncontrolled pulsed current.
3Measurement precision
If complex hardware is used for sensor signal processing, then measurement precision may improve, but feedback loop instability occurs
Solution Approach 1:
The patent implements a digital feedback control loop where the microcontroller continuously reads the sensor signal, processes it through digital filtering and calibration algorithms, compares the reading against target values, and adjusts the heater control accordingly. This digital feedback approach maintains measurement precision while improving feedback loop stability by eliminating the analog circuit instabilities and noise interference present in traditional systems.
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 system achieves rapid temperature increase (1-5 seconds) of NOx sensors, reducing time to closed-loop fuel control and minimizing electromagnetic interference, while ensuring stability and cost-effectiveness.
Implementation Method 1
a heater element that is supplied with current from a heater control circuit to preemptively heat the NOx sensor to the correct temperature
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A nitrogen-oxide (NOx) sensor control system includes a NOx sensor analog front-end, a temperature sensor analog front-end, and a processing system. The NOx sensor analog front-end is adapted to receive analog NOx sensor signals from a NOx sensor and is configured to convert the analog NOx sensor signals to digital NOx sensor signals. The temperature sensor analog front-end is adapted to receive analog temperature sensor signals from a temperature sensor and is configured to convert the analog temperature sensor signals to digital temperature sensor signals. The processing system is coupled to receive the digital NOx sensor signals and the digital temperature sensor signals and is configured, in response thereto, to: supply the digital NOx sensor signals to an external system, and control a flow of current to a heater element in the NOx sensor.