Hybrid Torque Control via Accelerator Pedal Threshold Segmentation
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Solution Overview
Problem
In hybrid motor vehicles, the existing methods for controlling torque in Zero Emissions Vehicle (ZEV) mode often result in untimely starts of the internal combustion engine when the electric machine alone cannot provide sufficient torque, limiting driving performance and increasing fuel consumption and pollution.
Innovation Solution
A method that controls the powertrain torque by keeping the heat engine stationary until the accelerator pedal position exceeds a predetermined threshold, allowing the electric machine to supply maximum torque within its capacity, and automatically starting the heat engine only when the threshold is reached, introducing a 'dead' pedal travel zone to prevent unexpected engine starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat engine is started automatically as soon as the maximum torque of the electric machine is reached, then the vehicle has full power availability, but the driver experiences unexpected engine starts and electric driving availability is reduced
Solution Approach 1:
The accelerator pedal travel is segmented into three distinct zones: a first zone (0% to threshold) where the heat engine is stopped and electric machine provides torque, a second zone (threshold to maximum depression) where the heat engine is automatically started, and a third zone where the electric machine operates in overload. This segmentation allows the system to differentiate between normal acceleration requests and emergency power needs, preventing unexpected engine starts while maintaining power availability when necessary.
2Power
If the electric machine operates in overload for a predetermined period, then the vehicle maintains full acceleration capability, but the electric machine may overheat or suffer damage
Solution Approach 1:
The system performs preliminary action by automatically starting the heat engine when the accelerator pedal position enters the second zone (between threshold and maximum depression), before the electric machine reaches its maximum overload capacity. This preemptive engine start prevents the electric machine from operating in overload condition, thereby avoiding overheating and potential damage while maintaining acceleration capability through the combined power of both power sources.
3Ease of operation
If the heat engine remains stopped beyond the maximum electric torque, then electric driving availability is enhanced, but the vehicle cannot respond to emergency acceleration situations
Solution Approach 1:
The system dynamically adjusts the operating mode based on the accelerator pedal position. In the first zone (0% to threshold), the heat engine is stopped to maximize electric driving availability. In the second zone (threshold to maximum depression), the heat engine is automatically started to ensure emergency response capability. This dynamic adjustment allows the system to optimize between electric driving availability and emergency response capability based on real-time driver input.
Data Source
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Figure 3
AI summary
In a mode of driving of a hybrid automotive vehicle in which only the electric machine (MEL) is used to propel the vehicle: when the accelerator pedal is in a position corresponding to a demanded torque value that is higher than or equal to the maximum torque (CMELMAX) that the electric machine can supply and strictly below a set threshold (S), the combustion engine remains switched off and the electric machine supplies this maximum torque (CMELMAX); and when the accelerator pedal is in a position corresponding to a demanded torque value greater than or equal to the threshold (S), the combustion engine is started automatically and supplies a torque such that the value of the total torque supplied by the electric machine and the combustion engine is equal to the demanded torque value.