Electric Motor Air Gap Control for Vehicle Drive Efficiency
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Solution Overview
Problem
Existing electric vehicle wheel driving systems face inefficiencies due to individual variability and operating environment factors, leading to inappropriate gap length switching in electric motors, which affects torque and rotation speed, resulting in suboptimal performance and drive feeling.
Innovation Solution
A wheel driving apparatus that includes an electric motor with a gap changer, an accelerator information obtaining device, a voltage calculation device, and a gap controller to adjust the air gap length based on the voltage utilization rate, ensuring optimal output characteristic switching regardless of motor variability or environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gap length is adjusted based on motor rotation speed using a reference map, then the motor can operate efficiently across a wide driving range, but the target gap length becomes inappropriate when the actual motor output characteristic deviates from the expected characteristic due to individual variability or operating environment factors
Solution Approach 1:
The patent implements feedback control by detecting the actual motor rotation speed and using it to dynamically adjust the gap length. The control unit continuously monitors the motor's operating state and modifies the gap length in real-time based on the detected rotation speed, ensuring the gap remains optimal despite variations in motor characteristics or environmental conditions. This closed-loop feedback mechanism resolves the contradiction by adapting the gap length to actual performance rather than relying on predetermined reference values.
Solution Approach 2:
The patent employs dynamic gap length adjustment where the gap length is not fixed or predetermined but continuously varies based on the motor's actual rotation speed. The hydraulic mechanism enables real-time modification of the gap length in response to changing operating conditions, transforming the system from a static reference-map-based approach to a dynamic adaptive system that maintains optimality across varying conditions.
2Adaptability or versatility
If the gap length is changed to switch output characteristics, then the motor can achieve different torque and rotation speed ranges, but inappropriate switching timing reduces vehicle performance and drive feeling
Solution Approach 1:
The control unit uses feedback from the detected motor rotation speed to determine the optimal timing for gap length switching. By continuously monitoring the actual rotation speed and comparing it with target values, the system switches gap lengths at precisely the right moments to maintain optimal motor performance across different operating ranges, thereby enhancing vehicle performance and drive feeling.
Solution Approach 2:
The system performs preliminary action by proactively adjusting the gap length in anticipation of upcoming operating conditions. The control unit detects rotation speed trends and adjusts the gap length before the motor enters a suboptimal operating range, ensuring smooth transitions and maintaining peak performance throughout the driving cycle.
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 allows for efficient driving from low-speed to high-speed ranges, maximizing electric motor potential and improving drive feeling by appropriately timing output characteristic changes, thus enhancing vehicle performance.
Implementation Method 1
an electric motor arranged to drive the wheel
Implementation Method 2
a gap changer arranged to change a gap length which is a length of an air gap in the electric motor
Data Source
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AI summary
An electric bike includes a wheel driving apparatus. The wheel driving apparatus includes an electric wheel drive motor which drives a wheel, a gap changer which changes a gap length in the wheel drive motor, and a motor control unit which controls the wheel drive motor and the gap changer. The motor control unit calculates a target gap length for the gap changing motor in the gap changer based on an accelerator opening-degree signal, a rotation speed, a q-axis electric-current command value, a power source voltage, and a voltage utilization rate. Then, a feedback control is provided to the gap changer based on a difference value between the target gap length and the actual gap-length. A good vehicle characteristic is obtained without being affected by individual variability or operating environment of the electric motor through efficient drive of the electric motor from a low-speed range through a high-speed range.