Hybrid Powertrain Torque Gradient Control for Stable Operating Points
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Solution Overview
Problem
Hybrid powertrains experience fluctuations and instability in optimal operating points due to phase differences between thermal and electrical consumption models, leading to torque fluctuations that destabilize the system.
Innovation Solution
A control method that includes determining an energy control law to set a raw torque point, using an equivalence factor and gradient, and applying first-order filtering to stabilize crankshaft torque gradients, with parameterizable tables to manage torque dynamics within defined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the optimal operating point is determined by energy management law, then overall consumption of the powertrain is optimized, but torque fluctuations and instability occur due to phase differences between thermal and electrical consumption models
Solution Approach 1:
A torque gradient limitation mechanism is introduced as an intermediary between the energy management law and the combustion engine torque control. This intermediary computes minimum and maximum torque gradients based on equivalence factor gradients, then limits the raw torque setpoint to ensure the actual torque gradient remains within acceptable bounds, thereby stabilizing the operating point while preserving energy optimization.
Solution Approach 2:
The control method implements feedback by continuously monitoring the equivalence factor gradient and using it to dynamically adjust the torque gradient limits. The actual combustion engine torque is computed based on the limited raw torque setpoint, and this feedback loop ensures that torque fluctuations are corrected in real-time, maintaining stability while responding to changing energy management requirements.
2Productivity
If the combustion engine torque is rapidly adjusted to follow optimal operating points, then energy optimization is improved, but torque fluctuations increase causing system instability
Solution Approach 1:
The control method dynamically adjusts the torque gradient limits based on the equivalence factor gradient. When the equivalence factor gradient is high, indicating rapid changes in energy management requirements, the torque gradient limits are adjusted to prevent excessive torque fluctuations. This dynamic adaptation allows the system to respond to energy optimization opportunities while maintaining torque stability.
Solution Approach 2:
The method changes the parameter of torque gradient limits based on the equivalence factor gradient. By computing minimum and maximum torque gradients as functions of the equivalence factor gradient, the system adapts its torque control parameters in real-time, allowing rapid response to energy optimization opportunities while preventing torque fluctuations that would cause instability.
3Use of energy by moving object
If torque setpoints are freely determined by consumption models, then energy efficiency is maximized, but phase differences cause fluctuating optimal points that destabilize the powertrain
Solution Approach 1:
The torque gradient limitation mechanism serves as an intermediary that reconciles the conflicting requirements of energy efficiency and stability. It computes acceptable torque gradient bounds based on equivalence factor gradients, then limits the raw torque setpoint to ensure stability while preserving the energy-efficient torque distribution determined by the consumption models.
Solution Approach 2:
The system uses feedback from the equivalence factor gradient to continuously adjust torque gradient limits. This feedback mechanism ensures that the combustion engine torque follows the optimal operating points determined by energy efficiency considerations while preventing the phase difference-induced fluctuations that would destabilize the powertrain.
Data Source
AI summary
A system for controlling a motor vehicle hybrid powertrain includes a set of calculators and a switch that determine the operating point and the overall consumptions of the powertrain and a combustion engine raw torque setpoint, determine a gradient of an equivalence factor as a function of the consumptions of the powertrain, determine a crankshaft torque gradient as a function of the target torque required at the wheel and of the step-down gear ratio, determine combustion engine torque gradient minimum and maximum values as a function of the gradient of the equivalence factor, of the crankshaft torque gradient, and of look-up tables, and determine an optimal torque setpoint as a function of the raw torque setpoint and of the combustion engine torque gradient minimum and maximum values.