CVT Control Using Engine Speed Feedback for Unreliable Output Sensors
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Solution Overview
Problem
Existing transmission control systems for vehicles and machines with continuously variable transmissions (CVTs) face instability when transmission output feedback signals are unreliable, such as during brake application or sensor failures, leading to incorrect torque measurements and fluctuating engine speeds.
Innovation Solution
An electronic control module (ECM) is programmed to execute a target engine speed control strategy, using engine output command signals and operational data to determine a target engine speed and corresponding transmission ratio, ensuring the engine operates at a constant speed by adjusting the CVT, even when transmission output feedback is unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission output feedback control is used, then machine output control precision is improved, but system reliability deteriorates when sensors fail or brakes are applied
Solution Approach 1:
The patent introduces an intermediary control strategy that switches between transmission output feedback control and engine speed feedback control based on operating conditions. When transmission output sensors fail or brakes are applied, the system uses engine speed as an intermediary parameter to maintain control, thereby preserving reliability while avoiding the direct use of unreliable transmission output feedback signals.
Solution Approach 2:
The control system dynamically switches between different control modes based on the reliability of transmission output feedback. The ECM continuously monitors brake status and sensor functionality, adapting the control strategy in real-time: using transmission output feedback when reliable, and switching to engine speed feedback when unreliable conditions are detected, thus maintaining both precision and reliability.
2Productivity
If transmission output feedback control is used during brake application, then machine output control is improved, but engine speed stability deteriorates due to incorrect torque measurements
Solution Approach 1:
The system performs preliminary detection of brake application status before executing transmission output feedback control. When brake application is detected, the control strategy proactively switches to engine speed feedback control, preventing the harmful effect of incorrect torque measurements on engine speed stability before they can occur.
Solution Approach 2:
The patent implements a dual feedback mechanism: primary feedback from transmission output sensors under normal conditions, and alternative feedback from engine speed sensors when brakes are applied or sensors fail. This feedback switching ensures that control decisions are always based on reliable measurements, maintaining engine speed stability during brake application.
3Measurement precision
If transmission output sensors are monitored for reliability, then control accuracy is improved, but device complexity increases
Solution Approach 1:
The ECM performs multiple functions: it controls transmission output based on transmission sensors, monitors sensor reliability, detects brake application status, and switches control strategies. This multi-functionality allows the system to maintain high control accuracy through reliability monitoring without adding separate dedicated monitoring devices, thus limiting the increase in device complexity.
Solution Approach 2:
The patent merges the reliability monitoring function with the existing ECM and its sensor interfaces. Instead of adding separate monitoring hardware, the system combines sensor data processing, reliability assessment, and control strategy selection within the existing control module, thereby improving control accuracy while minimizing additional device complexity.
Data Source
AI summary
A machine may include an engine, a traction device, a continuously variable transmission (CVT) connecting the engine to the traction device, an operator input device outputting engine output command signals input by an operator, an engine speed sensor monitoring an engine output speed, and an electronic control module (ECM). The ECM controls a machine output of the machine by executing a transmission output control routine using transmission output parameters as feedback when transmission output parameter sensor signals are reliable. The ECM controls the machine output by executing a target engine speed control routine using an engine output speed sensor signals as feedback when the transmission output parameter sensor signals are nor reliable. In the target engine speed control routine, the ECM determines a CVT transmission ratio that will cause the CVT to apply a load to the engine that will cause the engine to run at the target engine speed.