Electric Vehicle Control Device for Low Battery Torque Management
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Solution Overview
Problem
Existing control devices for electric vehicles stop both the drive motor and accessories when the high-voltage battery's energy capacity is low, leading to reduced operational performance and driver anxiety, especially when driving uphill or downhill.
Innovation Solution
A control device with a remaining energy capacity detecting unit, threshold storing unit, and drive state switching unit that reduces torque output of the drive motor and stops power supply to it while allowing accessories to operate when the energy capacity falls below specific thresholds, preventing deep discharge and ensuring continuous accessory operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control device stops both drive motor and accessories when remaining energy capacity is low, then the high-voltage battery is protected from deep discharge, but the operational performance and driver assistance become insufficient
Solution Approach 1:
The control device segments the load management into two independent parts: the drive motor and the accessories. When remaining energy capacity falls below the first threshold, the control device selectively stops the drive motor while maintaining accessory operation. This segmentation allows the system to protect the battery from deep discharge while preserving essential driver assistance functions, thereby resolving the contradiction between battery protection and operational performance.
2Loss of energy
If the control device reduces torque output of drive motor when energy capacity is low, then the battery discharge rate is reduced, but the driving performance deteriorates
Solution Approach 1:
The control device implements dynamic load management by adjusting the operating state of the drive motor based on real-time remaining energy capacity levels. When capacity drops below the first threshold, the system dynamically transitions the drive motor from normal operation to stopped state, while keeping accessories running. This dynamic adjustment optimizes energy conservation while maintaining essential vehicle functions, balancing energy loss reduction with acceptable driving performance.
3Device complexity
If the control device uses a single threshold for stopping drive motor and accessories, then the control logic is simple, but the operational flexibility is reduced
Solution Approach 1:
The control device changes the parameter of threshold values from a single value to multiple hierarchical values (first threshold and second threshold). The first threshold triggers selective stopping of the drive motor while maintaining accessory operation, and the second threshold triggers complete system shutdown. This parameter change enables differentiated control strategies at different energy levels, providing operational flexibility while managing system complexity through clear hierarchical logic.
Data Source
AI summary
A control device for an electric vehicle where a threshold storing unit is provided which stores two large and small thresholds and (first threshold>second threshold), and a drive state switching unit is provided which reduces torque output of a drive motor, while allowing accessories to operate, when a remaining energy capacity SOC from a remaining energy capacity detecting unit fails below the first threshold, and stops power supply to the drive motor, while allowing the accessories to operate, when the remaining energy capacity SOC from a remaining energy capacity detecting unit falls below the second threshold.