CVT Power Source Speed Control via Virtual Gears
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Solution Overview
Problem
Conventional continuously variable transmission (CVT) systems in mobile machines lack operator familiarity and efficiency, as they require holding the accelerator pedal at an intermediate position to maintain desired speeds, leading to operator fatigue, especially in rough terrain.
Innovation Solution
A method and system that allow operators to select target travel speeds using virtual gears, with a controller adjusting the power source output to maintain desired speeds while optimizing power usage, by calculating differences between target and actual speeds and scaling the accelerator pedal command to reduce power source output when approaching target speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a CVT system provides infinite torque-to-speed output ratios, then engine efficiency is improved, but operator familiarity and ease of operation deteriorate because the operator must hold the accelerator pedal at an intermediate position to maintain desired speeds
Solution Approach 1:
The patent divides the continuous CVT operation into discrete virtual gear segments (first virtual gear, second virtual gear, etc.), each corresponding to a specific travel speed range. This segmentation allows the operator to select from predefined gear-like options rather than continuously adjusting the accelerator pedal, thereby maintaining ease of operation while utilizing CVT technology.
Solution Approach 2:
The controller dynamically adjusts the output speed of the power source based on the selected virtual gear and actual travel speed. By changing the operational parameters of the power source in response to virtual gear selection and speed feedback, the system maintains both engine efficiency and operator familiarity.
2Ease of operation
If the controller controls the power source and CVT to maintain travel speed within a virtual gear range, then operator confidence and comfort are improved, but power source operation may not be economical in certain situations
Solution Approach 1:
The controller continuously monitors the actual travel speed of the mobile machine and compares it to the target speed range for the selected virtual gear. Based on this feedback, the controller adjusts the power source output speed to maintain optimal operation. This feedback mechanism enables the system to operate the power source economically while maintaining the travel speed characteristics that provide operator confidence.
Data Source
AI summary
Methods and systems for controlling a power source of a mobile machine having a continuously variable transmission (CVT) are disclosed. In one embodiment, the method includes receiving, from an operator of the mobile machine, input selecting of one of a plurality of target travel speeds of the mobile machine and input indicative of a requested output speed of the power source. The method further includes calculating a difference between the selected target travel speed and an actual travel speed of the mobile machine. Finally, the method includes adjusting the requested output speed of the power source based on the calculated travel speed difference, and commanding the power source based on the adjusted requested output speed of the power source.