CVT Clamping Pressure Control via Adaptive Feedback
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) face challenges in maintaining optimal clamping pressure to prevent chain slip while minimizing fuel consumption, as they require larger initial clamping forces due to pressure error variations and temperature changes, affecting control accuracy and responsiveness.
Innovation Solution
A control method is implemented to determine a target clamping pressure and calculate proportional, integral, and adaptive correction terms based on actual and target pressures, and temperature, to generate a commanded pressure for actuating the pulley sheaves, ensuring precise pressure control and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If larger initial clamping forces are used to prevent chain slip, then reliability is improved, but fuel consumption increases
Solution Approach 1:
The system dynamically adjusts clamping pressure parameters based on operating conditions (torque requests, temperature, pulley speeds) rather than maintaining a fixed high pressure. The control module modifies pressure magnitude and timing to achieve adequate chain grip while minimizing energy waste from excessive clamping forces.
Solution Approach 2:
The clamping pressure is made dynamic rather than static, with the control module continuously adjusting pressure levels in response to changing operational demands. This allows the system to apply only the necessary clamping force at any given moment, preventing chain slip when needed while reducing pressure during low-demand periods to save fuel.
2Measurement precision
If larger initial clamping forces are used to account for pressure error variations, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The system employs feedback mechanisms where the control module monitors actual clamping pressure, pulley speeds, and torque requests, then adjusts pressure commands accordingly. This closed-loop control compensates for pressure errors and variations without requiring continuously excessive clamping forces, thereby improving precision while managing energy consumption.
Solution Approach 2:
The control module applies preliminary clamping pressure adjustments in anticipation of torque requests and operational changes. By proactively setting appropriate pressure levels before high-load conditions occur, the system prevents chain slip without maintaining unnecessarily high pressure throughout operation, thus improving control accuracy while reducing overall energy use.
3Reliability
If higher clamping pressure is maintained to improve control accuracy, then reliability is improved, but fuel consumption increases
Solution Approach 1:
The clamping pressure system transitions from a static high-pressure maintenance approach to a dynamic adjustment strategy. The control module continuously adapts pressure levels based on real-time operational parameters, ensuring adequate control accuracy and reliability only when and where needed, rather than maintaining high pressure continuously, thus reducing fuel consumption.
Solution Approach 2:
The system modifies clamping pressure parameters dynamically based on operating conditions including torque requests, temperature, and pulley speeds. This parameter adaptation allows the system to maintain control accuracy and reliability under varying conditions without the penalty of sustained high-pressure application, thereby reducing energy consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach stabilizes pressure control, reduces the need for excessive clamping forces, improves CVT responsiveness, and minimizes fuel consumption by accurately adjusting clamping pressure in response to varying conditions.
Implementation Method 1
Frictional engagement between the sheaves of each pulley and the chain couples the chain to each of the pulleys to transfer torque from one pulley to the other
Implementation Method 2
determining a proportional correction term and an integral correction term based upon the target clamping pressure and the actual clamping pressure
Implementation Method 3
An adapt correction term is determined based upon the target clamping pressure and a temperature of the CVT
Data Source
AI summary
A method and apparatus for controlling a continuously variable transmission (CVT) of a powertrain system includes determining a target clamping pressure and an actual clamping pressure, and determining a proportional correction term and an integral correction term based upon the target clamping pressure and the actual clamping pressure. An adapt correction term is determined based upon the target clamping pressure and a temperature of the CVT. A commanded clamping pressure for controlling the CVT is determined based upon the proportional correction term, the integral correction term and the adapt correction term. A pressure command is employed to drive an actuator of a moveable sheave of a pulley of a variator of the CVT based upon the commanded clamping pressure.