Hybrid Vehicle Uphill Torque Control via SOC Defense
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Solution Overview
Problem
During uphill driving, hybrid electric vehicles with dual-clutch transmission (DCT) experience battery state of charge (SOC) degradation and increased energy consumption due to excessive battery discharge, limiting driving ability and fuel efficiency.
Innovation Solution
A method involving a controller that performs high torque control on the engine, reduces motor torque, and implements engine and motor speed control to defend the SOC value, with additional strategies like forced engine charging and DCT clutch slippage to minimize battery discharge and maintain SOC during uphill driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the motor is operated to satisfy driver request torque during uphill driving, then driving ability is improved, but battery discharge increases and SOC degrades
Solution Approach 1:
The system dynamically changes operating parameters by switching between different control modes (first control mode using motor torque, second control mode using engine torque) based on battery SOC levels. When SOC is high, the motor provides torque; when SOC is low, the engine provides torque through the DCT, thereby adapting the power source mix to energy availability while maintaining required driving performance
2Speed
If the engine clutch is slip-controlled to provide acceleration torque, then acceleration performance is improved, but the engine clutch lacks sufficient slip capacity and cannot be used effectively
Solution Approach 1:
The DCT clutch acts as an intermediary device that provides the necessary slip capacity for acceleration. Instead of relying on the engine clutch for slip control, the system uses the DCT clutch to manage torque handover and slip operations, thereby preserving the engine clutch for its primary function while enabling effective acceleration through the transmission system's clutch mechanism
3Ease of operation
If manual gear shifting is used to control driving, then driver control freedom is improved, but SOC defense capability is reduced and battery discharge increases
Solution Approach 1:
The system incorporates feedback control by continuously monitoring battery SOC levels and automatically adjusting gear shifting decisions. When SOC is low, the controller overrides manual gear shifting selections to prevent shifts that would cause excessive battery discharge, thereby providing feedback-based energy management that works together with driver inputs to optimize both controllability and energy conservation
4Speed
If the vehicle uses motor power at speeds below engageable speed, then acceleration capability is improved, but battery discharge area increases and SOC degrades
Solution Approach 1:
The system dynamically adjusts the boundary between motor-only operation and engine-assisted operation based on real-time conditions. Instead of using a fixed engageable speed threshold, the controller continuously evaluates battery SOC levels and driving conditions to determine the optimal transition point, thereby adapting the powertrain operation mode to current energy availability and minimizing unnecessary battery discharge while maintaining acceleration capability
Data Source
AI summary
A method of controlling uphill driving of a hybrid vehicle provided with a dual clutch transmission (DCT) may include determining, by a controller, a driving state of a vehicle on the basis of information collected from the vehicle; when the vehicle is determined as being in a uphill driving state, performing, by the controller, high torque control on an engine of the vehicle by increasing an engine torque to control the engine at a predetermined high torque engine operating point and reducing a motor torque of a motor in the vehicle to satisfy a driver request torque; and during the performing of the high torque control on the engine, comparing, by the controller, a state of charge (SOC) value of a battery with a set first SOC threshold value, and when the SOC value of the battery is less than or equal to the first SOC threshold value, performing engine and motor speed control to defend the SOC value of the battery.