Hybrid Drive Torque Control for Battery Voltage Stability
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Solution Overview
Problem
Hybrid drive systems face challenges in maintaining battery voltage stability and preventing unexpected vehicle driving force fluctuations, especially when the battery's performance is compromised, such as in low temperatures, leading to reduced output and shorter battery life.
Innovation Solution
A hybrid drive system incorporating a differential gearing mechanism with a controller that limits the output torque of both the first and second rotating electric machines to restore battery voltage and offset torque fluctuations, ensuring stable vehicle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotating electric machine outputs large torque to start the engine or accelerate the vehicle, then the vehicle power performance is improved, but the battery voltage drops suddenly and the battery service life is reduced
Solution Approach 1:
The control device monitors battery voltage in real-time and adjusts the rotating electric machine's torque output based on voltage feedback. When voltage drops below a threshold, the control device limits the torque to prevent further voltage decline and protect battery life, while still allowing sufficient torque for normal operation.
Solution Approach 2:
The system dynamically adjusts the torque output characteristics of the rotating electric machine based on operating conditions. During engine starting, the torque is limited to a predetermined value to prevent excessive battery current draw. During vehicle acceleration, the torque is modulated based on battery state to balance power delivery and battery protection.
2Reliability
If the output torque of the first rotating electric machine is limited to restore battery voltage, then the battery voltage is restored, but the engine starting performance is degraded
Solution Approach 1:
The control device detects battery voltage trends in advance and proactively limits the torque output of the first rotating electric machine when voltage drops are anticipated. This preliminary action prevents severe voltage collapse while maintaining sufficient torque for engine starting by adjusting the torque to a predetermined level rather than completely limiting it.
Solution Approach 2:
The system changes the torque parameter of the first rotating electric machine based on battery voltage conditions. When voltage is normal, full torque is permitted for optimal engine starting. When voltage drops, the torque parameter is adjusted to a predetermined limited value, balancing voltage restoration with starting performance.
3Reliability
If the output torque of the second rotating electric machine is limited to restore battery voltage, then the battery voltage is restored, but the vehicle acceleration performance is degraded
Solution Approach 1:
The control device dynamically modulates the torque output of the second rotating electric machine based on real-time battery voltage conditions. During vehicle acceleration, the torque is adjusted to provide sufficient power while preventing excessive battery current draw that would cause voltage collapse. The torque limitation is applied progressively rather than abruptly to maintain acceptable acceleration performance.
Solution Approach 2:
The torque parameter of the second rotating electric machine is changed based on battery voltage thresholds. When voltage is within normal range, the torque can reach maximum values for strong acceleration. When voltage drops below thresholds, the torque parameter is limited to predetermined values that restore voltage while maintaining acceptable acceleration capability.
4Stability of the object's composition
If the torque output is increased to offset driving force fluctuations during engine starting, then the vehicle driving force stability is improved, but the battery voltage drops further
Solution Approach 1:
The control device uses the second rotating electric machine to generate counter-torque that offsets the reaction force from the first rotating electric machine during engine starting. This counterweight approach stabilizes the output shaft rotation and prevents driving force fluctuations while carefully controlling the torque magnitude to avoid excessive battery current draw.
Solution Approach 2:
The system monitors both the torque output of the first rotating electric machine and the battery voltage in real-time. When torque is increased to offset driving force fluctuations, the feedback mechanism ensures that the torque magnitude does not exceed levels that would cause severe voltage drops, balancing stability with voltage protection.
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 effectively restores battery voltage and inhibits unexpected driving force fluctuations, enhancing vehicle performance and extending battery life by controlling torque output during engine starting and operation.
Implementation Method 1
a first rotating electric machine (MG1) connected to a first rotating element... the first rotating electric machine is used to rotatably drive the engine to thereby start the engine
Implementation Method 2
a second rotating electric machine (MG2)... the second rotating electric machine is connected to the third rotating element... the second rotating electric machine functions mainly as a motor
Implementation Method 3
the first rotating electric machine is used to rotatably drive the engine... the driving force of the engine is thereafter used to charge the battery with the electric power generated by the first rotating electric machine
Data Source
AI summary
A hybrid drive system includes an input member connected to an engine; an output member connected to a wheel; a first rotating electric machine; a second rotating electric machine; a differential gearing; a controller that controls the first rotating electric machine and the second rotating electric machine; and an electric power supplier that supplies the first rotating electric machine and the second rotating electric machine with electric power.