In-Cylinder Pressure Sensor Signal Processing Circuit Drift Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electronic control systems for internal combustion engines face challenges in correcting the drift of offset voltage in in-cylinder pressure sensors due to temperature changes, requiring a separate signal wire for microcomputer communication, which increases costs.
Innovation Solution
An electronic control system incorporating a signal processing circuit with a hold circuit and differential amplification circuit, where the hold circuit continues to output a hold signal based on a microcomputer instruction, allowing for drift correction without a separate signal wire, by setting and resetting the hold circuit based on crank angle signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate signal wire is used for the microcomputer to transmit reset instructions to the pressure sensor, then the offset voltage drift can be corrected, but the system cost increases
Solution Approach 1:
The patent combines the reset instruction transmission function with the existing power supply wire by superimposing digital signals on the analog power supply line. The microcomputer outputs reset instructions through a general-purpose I/O port that shares the power supply wire with the pressure sensor, eliminating the need for a separate signal wire while maintaining the ability to correct offset voltage drift
Solution Approach 2:
The power supply wire is made multi-functional by enabling it to carry both its primary function (supplying power to the pressure sensor) and an additional function (transmitting reset instructions from the microcomputer). This is achieved through signal superposition techniques that allow digital control signals to be transmitted over the analog power line without interfering with power delivery
2Measurement precision
If the output signal of the pressure sensor is amplified before A/D conversion, then the resolution of pressure detection is improved, but the dynamic range of the A/D conversion decreases
Solution Approach 1:
The patent employs dynamic gain control where the amplification factor of the operational amplifier is adjusted based on the detected pressure range. When pressure values are small, higher amplification is applied to improve resolution; when pressure values are large, lower amplification is used to maintain dynamic range. This dynamic adjustment allows the system to optimize both resolution and dynamic range adaptively
Solution Approach 2:
The system changes the amplification parameter of the signal processing circuit based on the measured pressure magnitude. By dynamically modifying the gain parameter, the system can accommodate different pressure ranges while maintaining optimal resolution, effectively resolving the trade-off between resolution and dynamic range
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 solution effectively corrects the drift in in-cylinder pressure sensor output voltage, enhancing the accuracy of pressure detection and reducing costs by eliminating the need for additional signal wires, while improving the resolution and dynamic range of the A/D conversion.
Implementation Method 1
an in-cylinder pressure sensor body fitted in an insertion hole formed in a cylinder head so that the pressure in the combustion chamber is applied to a piezoelectric transducer through a diaphragm of the pressure sensor. The pressure sensor thus outputs, as the output signal, a voltage corresponding to the applied pressure.
Implementation Method 2
The differential amplification circuit is configured to amplify a difference between the pressure signal of the pressure sensor and an output signal of the hold circuit and outputs an amplified difference to the microcomputer.
Data Source
AI summary
An electronic control system includes a microcomputer and a signal processing circuit, and receives output signals of an in-cylinder pressure sensor and a crank angle sensor. The output signal of the pressure sensor indicates an output voltage of a piezoelectric transducer and a reference voltage. The signal processing circuit includes a hold circuit and a differential amplifier circuit. The differential amplifier circuit amplifies a difference between the output signal of the pressure sensor and the output signal of the hold circuit and outputs the result to the microcomputer. The hold circuit switches over the output signals in response to a switchover instruction of the microcomputer. When the switchover instruction is a set instruction, the hold circuit holds as its output signal the output signal of the pressure sensor outputted at the time of receiving the set instruction. The microcomputer outputs the set instruction to the hold circuit in response to the output signal of the crank angle sensor.