Power-Split Planetary Drive Control for Lower Startup Losses
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Solution Overview
Problem
Existing power-to-power drive gear units with planetary gear systems experience high loss performance and inefficiency due to the distribution of drive power between the sun wheel and hollow wheel, leading to unfavorable operating states during startup.
Innovation Solution
A control procedure that optimizes the drive power distribution between two electric motors connected to the planetary gear, ensuring that the drive line from the first electric motor is greater than or equal to the drive power from the second electric motor, thereby reducing energy loss and preventing unfavorable operating states during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If approximately 70% of total drive power is fed into the gear unit via the sun gear and approximately 30% via the rotating ring gear, then the planetary gears speed increases, but this results in higher power losses and lower efficiency
Solution Approach 1:
The patent applies parameter changes by optimizing the drive power distribution ratio between sun gear and ring gear. Instead of the conventional 70:30 split, the invention adjusts the power distribution parameters to achieve a more balanced ratio, thereby reducing planetary gear speeds and power losses while maintaining effective drive transmission.
2Reliability
If a specific starting sequence of electric motors is observed during startup, then planetary gears reversing direction is prevented, but this leads to unfavorable operating conditions for bearings and potential total failure
Solution Approach 1:
The patent applies preliminary action by implementing a controlled startup sequence where the first electric motor is locked during initial acceleration of the second motor. This preliminary locking action prevents planetary gear reversal before it can occur, and the controlled release timing ensures bearings remain in favorable operating conditions throughout the startup process.
3Reliability
If the first electric motor is locked during startup and the second electric motor is accelerated to target speed, then planetary gear reversal is prevented, but this requires complex control sequencing
Solution Approach 1:
The patent applies self-service through a control system that automatically manages the locking and release sequencing of the first electric motor based on the operational state of the second motor. The control unit monitors speed thresholds and automatically executes the locking/release sequence without requiring manual intervention, thereby achieving reliable prevention of unfavorable operating states while keeping the control interface simple.
Data Source
Figure 1
Figure 2~3
AI summary
A method for controlling a power-split drive-gearbox unit 10, wherein the drive-gearbox unit 10 comprises a planetary gear 12, a first electric motor 14, and a second electric motor 16, and wherein the first electric motor 14 is connected to a ring gear 20 of the planetary gear 12, and the second electric motor 16 is connected to the sun gear 22 of the planetary gear 12. Each of the electric motors 14, 16 provides a respective drive power, and both drive powers combine at the output of the planetary gear 12 to form a sum representing 100% of the total drive power. The electric motors 14, 16 are each controlled such that the first electric motor 14 contributes a first drive power L1 and the second electric motor 16 contributes a second drive power L2 to the sum total drive power Lsum, wherein the drive power L1 is greater than or equal to the drive power L2.