Vehicle AC Generator Control Device Voltage Undershoot Suppression
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Solution Overview
Problem
The vehicle AC generator experiences undershoot in output voltage when a target voltage change command reduces the target voltage from a high to a low value, leading to discomfort due to noticeable variance in illumination, as the battery voltage does not drop immediately, causing the load response control to start only when the generator must produce power, resulting in a drop below the target voltage.
Innovation Solution
A control device with a voltage control unit that adjusts the target voltage value and includes a gradual excitation control circuit with varying excitation duty characteristics, allowing the excitation duty to increase at a different rate in specific regions, thereby suppressing undershoot by adjusting the target voltage value in response to changes in vehicle load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the target voltage value is changed from high to low, then the battery voltage is maintained at a high level, but the excitation duty drops to 0% and load response control is delayed, causing output voltage undershoot
Solution Approach 1:
The patent applies preliminary action by detecting when the target voltage value changes from high to low and proactively setting the excitation duty to a predetermined value before the battery voltage actually drops. This anticipatory measure ensures that the generator is ready to supply power immediately when load increases, preventing the excitation duty from dropping to 0% and avoiding output voltage undershoot.
Solution Approach 2:
The patent implements preliminary anti-action by counteracting the potential harmful effect (excitation duty dropping to 0%) before it occurs. When the target voltage is reduced, the system preemptively maintains the excitation duty at a sufficient level, thereby preventing the condition that would lead to load response delay and output voltage instability.
2Stability of the object's composition
If the excitation duty is controlled to increase gradually, then the drive torque increases smoothly, but the load response is delayed when the target voltage changes from high to low
Solution Approach 1:
The patent applies dynamics by making the excitation duty control characteristic adaptable based on operating conditions. The system switches between different control modes: when the target voltage changes from high to low, the excitation duty is set to a predetermined value for immediate response; otherwise, gradual increase is maintained for smooth torque transition. This dynamic adjustment optimizes both response speed and smoothness according to situational needs.
Solution Approach 2:
The patent implements parameter changes by modifying the excitation duty control characteristic based on the target voltage change condition. The control parameter (excitation duty) is adjusted differently depending on whether the target voltage is decreasing from high to low or under normal conditions, allowing the system to optimize between rapid response and smooth torque increase as needed.
Data Source
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AI summary
A control device for a vehicle AC generator is improved to make an undershoot value of a battery voltage value smaller in a case where a target voltage value is changed from a high target voltage value to a low target voltage value by an external control unit. A voltage control unit in the control device includes target voltage adjusting means for adjusting the target voltage value in response to a target change command from the external control unit and a gradual excitation control circuit that controls the excitation duty to increase according to an excitation duty control characteristic when a vehicle load increases and when the target voltage adjusting means varies the target voltage value to a lower value. The gradual excitation control circuit includes duty characteristic varying means for varying the excitation duty control characteristic. The duty characteristic varying means varies a rate of increase of the excitation duty in a predetermined region of the excitation duty control characteristic in comparison with other region.