Electric Vehicle Over-Shifting Prevention Control
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Solution Overview
Problem
Electric vehicles with multi-gear transmissions face issues of over-shifting, leading to excessive regenerative voltages and potential damage due to the motor spinning beyond its maximum rated RPM when downshifting, especially when selecting a too low gear at high speeds.
Innovation Solution
Implementing a method and apparatus to predict and prevent over-shifting by determining if a new gear selection will result in overvoltage or overspin conditions, using a vehicle control unit to calculate the motor speed and gear ratios, and actuating a downshifting prevention mechanism, either externally or internally within the gearbox, to prevent the shift from completing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a too low gear is quickly selected at high speeds, then the vehicle can achieve higher acceleration or lower speed control, but the motor spins above maximum rated RPM causing excessively large regenerative voltages that exceed system design parameters
Solution Approach 1:
The control system performs predictive calculations before the actual gear shift occurs. By computing the predicted motor speed and regenerative voltage based on current vehicle speed, current motor speed, and the candidate lower gear ratio, the system determines in advance whether the downshift would cause overvoltage or overspin conditions. This preliminary assessment allows the system to prevent harmful shifts before they occur, maintaining both operational flexibility and system safety.
Solution Approach 2:
The system continuously monitors current vehicle speed and motor speed, and uses this feedback to dynamically calculate whether a proposed gear shift would be safe. The control unit compares the predicted motor speed against the maximum rated RPM and calculates the resulting regenerative voltage to determine if it exceeds design parameters. This closed-loop feedback mechanism enables real-time gear shift management that adapts to current operating conditions.
2Use of energy by moving object
If regenerative braking is used to recharge the battery, then energy efficiency is improved, but the motor can spin beyond maximum rated RPM producing overvoltage that causes damage
Solution Approach 1:
The control system continuously monitors motor speed and vehicle speed during regenerative braking operations. By calculating the predicted motor speed that would result from a gear change and comparing it against maximum rated RPM, the system determines whether the regenerative braking would produce overvoltage conditions. This feedback mechanism allows the system to safely utilize regenerative energy while preventing damage from excessive voltages.
Solution Approach 2:
Before allowing regenerative braking to proceed or before permitting a gear shift during regen, the system performs predictive calculations to determine if the motor speed will exceed maximum rated RPM. This preliminary assessment prevents overvoltage conditions from developing, ensuring that energy recovery operations remain within safe electrical parameters and do not cause damage to the battery or motor.
3Adaptability or versatility
If multiple gears are provided in the transmission system, then the vehicle can operate across a wider speed range, but the complexity of gear shift control increases
Solution Approach 1:
The control system automatically performs the complex calculations and decision-making required for safe gear shifts without requiring manual intervention or complex mechanical control mechanisms. The microcontroller unit autonomously monitors vehicle and motor speeds, predicts the outcomes of potential gear changes, and executes appropriate shift commands or prevention actions. This self-service approach simplifies the overall control architecture while enabling sophisticated multi-gear management.
Solution Approach 2:
The patent replaces complex mechanical gear shift control mechanisms with an electronic control system that uses computational algorithms to manage gear changes. Instead of relying on mechanical interlocks or complex hydraulic systems, the microcontroller unit uses software-based predictive calculations to determine safe gear shifts. This substitution of mechanical complexity with electronic intelligence simplifies the physical control system while maintaining adaptability across the full speed 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
Prevents damage by ensuring gear shifts are within safe parameters, maintaining the motor within its design RPM range and preventing overvoltage conditions, thereby extending the lifespan of the electric vehicle's components.
Implementation Method 1
When no energy is supplied to the motor, but the traction wheel(s) supply mechanical motion to the motor, the motor itself will become a generator supplying energy that can be used to assist in recharging the vehicle battery system.
Data Source
AI summary
Methods and apparatus are provided for preventing over-shifting in electric vehicles having a multi-gear transmission and an electric motor operable in a drive mode and a regenerative braking mode. The method includes: (a) predicting the speed of the electric motor resulting from downshifting from a current gear being used to a next lower gear based on a current speed of the electric vehicle, a current speed of the electric motor, and a gear ratio of the next lower gear; (b) determining if the speed of the electric motor predicted in (a) will cause an overvoltage condition from regenerative braking or an overspin condition in the electric motor; (c) preventing downshifting to the next lower gear when it is determined that the downshifting will cause an overvoltage condition or an overspin condition in the electric motor; and (d) repeating steps (a), (b), and (c) a plurality of times.