Hybrid Vehicle Torque Fluctuation Control via Adaptive Countertorque
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Solution Overview
Problem
Conventional driving force control methods for hybrid vehicles suffer from energy efficiency deterioration due to high-frequency motor control required to suppress engine torque pulsation, leading to significant electric power loss and reduced fuel economy.
Innovation Solution
A driving force control method that adjusts the countertorque based on the average torque output and engine speed of the internal combustion engine, optimizing the control gain to minimize electric power consumption while effectively absorbing torque fluctuations, thereby reducing vibration and noise in the passenger compartment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-frequency motor control is applied to suppress engine torque pulsation, then torque fluctuation absorption is improved, but energy efficiency deteriorates due to significant electric power loss
Solution Approach 1:
The control method dynamically adjusts the motor's countertorque output based on real-time engine operating conditions (engine speed and torque fluctuations). Instead of applying constant high-frequency control, the system adaptively modulates the torque suppression intensity, reducing motor control activity when torque fluctuations are minimal or when operating conditions make suppression less effective. This dynamic adjustment optimizes the balance between torque fluctuation absorption and energy consumption.
Solution Approach 2:
The invention changes the control parameters by introducing a frequency-dependent control strategy where the motor's torque output is adjusted based on the frequency characteristics of engine torque pulsations. The system identifies dominant pulsation frequencies and applies targeted countertorque at these frequencies rather than continuous high-frequency control. Additionally, the control gain is varied as a parameter function of engine speed and load conditions, reducing overall energy consumption while maintaining effective torque fluctuation suppression.
2Loss of energy
If cylinder deactivation is implemented to improve fuel economy, then fuel consumption is reduced, but torque fluctuation increases requiring enhanced absorption capability
Solution Approach 1:
The control system continuously monitors engine torque output and detects fluctuations caused by cylinder deactivation operations. When torque pulsations are detected exceeding threshold levels, the system automatically increases motor countertorque to compensate. This feedback mechanism ensures that fuel economy benefits from cylinder deactivation are maintained while torque fluctuation absorption is enhanced only when and where needed, preventing unnecessary energy consumption.
Solution Approach 2:
The system proactively prepares for torque fluctuations by predicting when cylinder deactivation will occur based on engine operating conditions and transmission shift patterns. Before cylinder deactivation is executed, the control system pre-adjusts motor torque output to counteract anticipated torque pulsations. This preliminary anti-action reduces the severity of torque fluctuations transmitted to the transmission system, protecting against potential damage while maintaining fuel economy benefits.
3Speed
If engine inertia is reduced to shorten shifting time, then transmission shifting speed is improved, but torque fluctuation absorption capability is reduced
Solution Approach 1:
The electric motor serves as an intermediary between the engine and transmission system, decoupling the relationship between engine inertia and torque fluctuation transmission. By introducing the motor as a buffer, the system can use the motor's electromagnetic torque to absorb engine torque pulsations independently of engine inertia. This allows the transmission to achieve fast shifting speeds with reduced engine inertia while the motor compensates for the reduced natural torque absorption capability of the lighter engine.
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(d)
AI summary
Provided are a driving force control method and device for a hybrid vehicle, each capable of effectively absorbing torque fluctuation of an engine while suppressing deterioration in energy efficiency. The driving force control device for a hybrid vehicle comprises a PCM (14) configured to: estimate an average torque output by an engine (2); estimate a torque fluctuation component of the torque output by the engine; set a countertorque for suppressing the estimated torque fluctuation component; and control an electric motor to output the set countertorque, wherein the PCM is operable, under a condition that an engine speed is constant, to set the countertorque such that, as the average torque output by an engine becomes larger, the absolute value of the countertorque becomes smaller.