Hybrid Battery Discharge Control for Reverse Drivability
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Solution Overview
Problem
In hybrid vehicles without a separate reverse gear, the battery discharge limit control system restricts electric motor output based on the state of charge, making reverse operation impossible when the battery is low, as it prioritizes forward travel by limiting battery discharge.
Innovation Solution
A battery discharge limit control system that includes a controller adjusting the motor output by applying different state of charge defensive maps for forward and reverse shift stages, increasing the output limit for reverse operation to ensure sufficient energy for reverse drivability, and utilizing a hybrid starter generator to synchronize engine and motor speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery discharge limit control restricts electric motor output based on state of charge to prevent complete discharge, then the battery reliability is improved, but the reverse operation capability is lost when battery charge is low
Solution Approach 1:
The patent applies dynamics by making the battery output limit adjustable based on operating conditions. Specifically, the control unit increases the battery output limit when reverse operation is detected, allowing the system to adapt its discharge characteristics dynamically rather than using a fixed limit. This resolves the contradiction by enabling reverse capability at low SOC while maintaining forward travel reliability through conditional adjustment of the discharge limit.
Solution Approach 2:
The patent changes the parameter of battery output limit based on the shift stage (forward vs. reverse). When reverse shift stage is detected, the system increases the battery output limit value, allowing greater discharge current to be permitted. This parameter change enables the system to maintain reverse operability even when battery charge is low, while still applying stricter limits during forward operation to prevent complete discharge.
2Ease of operation
If the battery output limit is increased for reverse operation, then the reverse drivability is improved, but the risk of complete battery discharge increases
Solution Approach 1:
The system dynamically adjusts the battery output limit based on the detected shift stage. When reverse operation is detected, the limit is increased temporarily to enable drivability. When forward operation is detected, the limit returns to the conservative level to prevent complete discharge. This dynamic adjustment resolves the contradiction by providing high output only when needed for reverse operation while maintaining safety margins during forward operation.
Solution Approach 2:
The patent segments the battery discharge control into different modes based on shift stage: forward shift mode with conservative output limits, and reverse shift mode with increased output limits. This segmentation allows the system to optimize for reverse drivability when needed while maintaining battery safety during forward operation, effectively resolving the contradiction through conditional control strategies.
Data Source
AI summary
A battery discharge limit control system is provided. The system includes a motor driven by receiving the power stored in a battery and a clutch connected to the rotary shaft of the motor. Additionally, an engine includes the rotary shaft connected to the rotary shaft of the motor through the clutch and a transmission changes the rotational speed of the rotary shaft of the motor or the engine based on the input of the shift stage instruction to output the rotational speed to a driving wheel of a vehicle. A controller opens the clutch and drives the motor in the reverse rotation, when the input of the shift stage instruction is a reverse shift stage.