Hybrid Vehicle Torque Setpoint Control via Reference Frame Switching
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Solution Overview
Problem
Hybrid vehicles face challenges in translating the driver's accelerator pedal depression into a torque setpoint, especially when the kinematic chain is not closed, making it difficult to control vehicle movement independently of the actuator speed or gear ratio, particularly at low speeds.
Innovation Solution
The method alternates between two reference frames - Torque/RPM (Ref-A) and Force/Velocity (Ref-B) to interpret the accelerator pedal depression, using Ref-A for low speeds and Ref-B for higher speeds, ensuring a pleasant and repeatable management of take-off, neutral, and parking phases by conserving mechanical power and managing the transition between the two frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the driver's accelerator pedal depression is interpreted in iso-power (Torque/RPM reference frame), then the vehicle behavior becomes independent of actuator speed and gear ratio, but the translation becomes impossible when the kinematic chain is not closed (clutch open or slipping), especially at low speeds
Solution Approach 1:
The system dynamically switches between two reference frames (iso-power Torque/RPM and iso-force Force/Velocity) based on operating conditions such as vehicle speed and clutch state. This allows the system to adapt its interpretation method to match the current operational context, resolving the contradiction between maintaining speed independence and ensuring translation capability across all operating modes.
Solution Approach 2:
The system changes the fundamental parameters used for interpreting accelerator pedal depression based on operating conditions. At low speeds or when the clutch is open, it switches from power-based parameters (Torque/RPM) to force-based parameters (Force/Velocity), enabling continuous and meaningful torque setpoint translation across the entire operating range.
2Device complexity
If the torque setpoint is determined using a single reference frame, then the control system is simpler, but the vehicle cannot maintain smooth power delivery across transitions between different operating modes (low speed/high speed, clutch open/closed)
Solution Approach 1:
The control system is segmented into two distinct reference frame interpretations (iso-power and iso-force), each optimized for specific operating conditions. This segmentation allows each mode to be independently tuned and optimized, while a transition management mechanism ensures smooth switching between modes, maintaining power delivery continuity without requiring a single overly complex reference frame.
3Reliability
If the system switches between two reference frames, then smooth power delivery is maintained across all operating conditions, but the control logic and transition management become more complex
Solution Approach 1:
The system uses feedback from operating conditions (vehicle speed, clutch state) to automatically determine which reference frame to apply. This feedback mechanism simplifies the transition management logic by using objective, measurable parameters to trigger mode switching, reducing the complexity of control logic while ensuring reliable and smooth transitions between operating modes.
Data Source
AI summary
Method for formulating the setpoint torque for the actuators of a hybrid vehicle powerplant (GMP) from the extent to which the accelerator pedal is depressed, comprising on the one hand, a traction combustion engine (1) connected to the vehicle drivetrain (2) by a cut-off clutch (3) with slipping operation between an open position in which it transmits no thermal power, and a closed position in which it transmits all of the power of the combustion engine to the drivetrain and, on the other hand, a traction electric machine (4) directly transmitting all of its power to the drivetrain (2), characterized in that the depression of the accelerator pedal is interpreted as a demand for power dictating a torque setpoint dependent on the speed of an actuator in an engine frame of reference (Ref–A), or as a demand for force dependent on the speed of travel of the vehicle in a vehicle frame of reference (Ref–B).