CVT Speed Lag Compensation via True Engine Torque Detection
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Solution Overview
Problem
Conventional CVT systems experience vehicle speed lag due to changing load conditions, as they rely on engine speed as both the measured and control variable, leading to unstable speed governing conditions.
Innovation Solution
A control method that detects true engine torque from load changes, calculates engine speed droop, and generates a compensation command to adjust the target engine speed, providing a compensated engine speed signal to stabilize vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If engine speed is used as both the measured and control variable for speed lag compensation, then the control system is simple, but the speed governing becomes unstable due to load-induced speed fluctuations
Solution Approach 1:
The patent introduces an intermediary variable (engine torque or load indicator) to mediate between the control variable (engine speed) and the measured variable (vehicle speed). Instead of directly using engine speed as both control and measurement basis, the system uses engine torque to predict expected speed changes and compensates accordingly, breaking the direct feedback loop that causes instability
Solution Approach 2:
The system performs preliminary calculation of expected engine speed changes based on detected engine torque before the actual speed lag occurs. By anticipating the speed droop based on load changes (torque detection), the control system can pre-adjust or compensate for the expected deviation, preventing instability rather than reacting to it
2Measurement precision
If the control system compensates for load-induced speed changes by adjusting engine speed, then vehicle speed accuracy improves, but the system becomes sensitive to environmental changes and load variations causing fluctuating speed governing
Solution Approach 1:
The patent uses engine torque as an intermediary parameter that is less sensitive to environmental changes than direct engine speed measurements. By basing compensation on torque (which changes more predictably with load) rather than directly on speed fluctuations (which are affected by environment), the system achieves better accuracy without sacrificing reliability
Solution Approach 2:
The control system performs preliminary assessment of load conditions through torque detection and calculates expected speed droop before implementing compensation. This anticipatory approach allows the system to prepare appropriate compensation commands based on predictable load-induced changes, improving both accuracy and reliability by avoiding reactive adjustments to unstable speed signals
Data Source
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AI summary
A method and associated system for compensation of vehicle speed lag resulting from changing load conditions in a continuously variable transmission (CVT) vehicle includes detecting and measuring true engine torque resulting from load changes placed on the vehicle engine. A true engine speed droop is calculated from the true engine torque. A compensated engine speed signal is generated based on the calculated true engine speed droop and is applied to the engine to produce a true engine speed that corresponds to a target engine speed at the load condition corrected for true engine speed droop.