Virtual Gear Control for CVT Operator Familiarity
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Solution Overview
Problem
Operators of machines equipped with continuously variable transmissions (CVTs) experience discomfort due to the lack of selectable and predictable gear ratios, which are familiar in conventional transmissions, leading to unfamiliarity and reduced reliability in operating these machines.
Innovation Solution
A method and system that utilize a plurality of virtual gear ratios, allowing operators to select and adjust ground speed and power source speed independently through an operator input device, with a controller converting these inputs into CVT and power source commands to mimic the behavior of traditional transmissions, thereby providing a more familiar and reliable operating experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a CVT is used to provide continuous torque-to-speed output ratios, then the adaptability and versatility of the transmission is improved, but the ease of operation deteriorates due to operator discomfort and unfamiliarity
Solution Approach 1:
The patent divides the continuous CVT operation into discrete virtual gear ratios, creating segmented speed ranges (e.g., first through eighth gears) that correspond to traditional transmission behavior. This segmentation allows operators to select from predefined ranges while the CVT continuously adjusts within each range, bridging the gap between continuous adaptability and discrete operator familiarity.
Solution Approach 2:
The controller acts as an intermediary between the operator's discrete gear selection and the CVT's continuous adjustment mechanism. When an operator selects a virtual gear ratio, the controller mediates by automatically adjusting the CVT ratio within that gear's speed range, eliminating the need for manual continuous adjustment while maintaining operator control over the transmission's overall behavior.
2Ease of operation
If virtual gear ratios are implemented to provide discrete speed ranges, then the ease of operation is improved, but the device complexity increases due to the need for controller coordination
Solution Approach 1:
The controller serves multiple functions simultaneously: it manages the virtual gear ratio selections, coordinates CVT ratio adjustments, monitors operator inputs, and ensures smooth transitions between gears. By consolidating these diverse control functions into a single multi-functional controller, the patent reduces overall system complexity compared to having separate control mechanisms for each function.
Solution Approach 2:
The system provides self-service through automatic CVT ratio adjustment within each virtual gear range. Once an operator selects a gear, the controller automatically manages the continuous ratio changes needed to maintain optimal performance within that gear's speed range, eliminating the need for additional manual controls or complex mechanical adjustment mechanisms.
3Adaptability or versatility
If the power source speed is adjusted independently of the CVT speed, then the adaptability of the powertrain system is improved, but the device complexity increases
Solution Approach 1:
The patent segments the speed control into two independent but coordinated channels: power source speed control and CVT ratio control. This segmentation allows each component to be optimized independently for its specific function while maintaining overall system adaptability, with the controller coordinating between the two segmented control channels.
Solution Approach 2:
The patent merges the power source control and CVT control into a unified system managed by a single controller. By combining these two control functions under one coordinating system rather than using separate independent control systems, the patent reduces overall complexity while maintaining the adaptability benefits of independent adjustment capabilities.
Data Source
AI summary
A system and method of controlling the speed of a machine having a continuously variable transmission (CVT) operatively coupled to a power source. A plurality of selectable virtual gear ratios can be associated with the CVT. The machine may include an operator input device that may generate a operator input signal indicative of a desired adjustment in the ground speed. The operator input signal may be converted to a CVT speed command and to a power source speed command that are communicated to the CVT and the power source, respectively. The CVT adjusts the machine speed in accordance with the CVT speed command, while the power source adjusts its speed in accordance with the power source speed command, so that operation of the power source is substantially independent of operator of the CVT.