Hybrid Vehicle Engine Startup Control via Motor Current Load Estimation
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Solution Overview
Problem
Existing hybrid vehicle systems lack a method to determine the optimal startup timing for the internal combustion engine to prevent driving force decrease without requiring separate special devices to measure road gradient and carrying weight.
Innovation Solution
A control device with an acceleration demand determination unit, travel control unit, load estimation unit, startup speed determination unit, and startup unit that uses the electric motor's current value to estimate load and determine the appropriate startup speed for the internal combustion engine, allowing it to start when the vehicle reaches a predetermined speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate special devices are disposed to obtain road gradient and carrying weight, then load measurement precision is improved, but device complexity increases
Solution Approach 1:
The electric motor serves multiple functions: it acts as both the driving motor and a load sensing device. By monitoring the current value supplied to the electric motor during vehicle travel, the system estimates the load (including road gradient and carrying weight) without requiring separate measurement devices. This multi-functional approach resolves the contradiction by eliminating additional sensors while maintaining load measurement capability.
Solution Approach 2:
The system uses the electric motor's own operational parameters (current value) to determine the load condition. The motor essentially measures the load through its own electrical characteristics during operation, eliminating the need for external measurement devices. This self-service principle allows the system to obtain load information inherently available during motor operation.
2Reliability
If engine startup timing is advanced to prevent driving force decrease, then driving force stability is improved, but energy consumption increases
Solution Approach 1:
The system determines the optimal engine startup timing in advance by estimating the load and calculating when the electric motor's driving force will become insufficient. The engine is started up at this predetermined timing before the driving force actually decreases, ensuring smooth transition while avoiding premature startup. This preliminary action based on load estimation resolves the contradiction by timing the engine startup optimally.
Solution Approach 2:
The system continuously monitors the current value supplied to the electric motor and uses this feedback to estimate the load condition. Based on this real-time feedback, the control device dynamically determines the appropriate engine startup timing. This feedback mechanism allows the system to adapt to changing load conditions and optimize engine startup timing, preventing unnecessary early startup that would waste energy while ensuring driving force stability is maintained.
Data Source
AI summary
When an engine (2) is in a stopped state and a vehicle is in a standstill state, a travel control unit (8a2) allows the vehicle to travel by a driving force of a rear motor (6) during a period after the brake is released until an acceleration demand determination unit (8a1) determines that acceleration is demanded for the vehicle. During the period, a startup speed determination unit (8a4) determines a startup travelling speed where the engine (2) is started up on the basis of a load which is estimated by a load estimation unit (8a3) on the basis of a current value supplied to the rear motor (6). When the travelling speed of the vehicle is equal to or greater than the startup travelling speed, a startup unit (8a5) starts up the engine (2).