Infinitely Variable Transmission Coasting Control
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Solution Overview
Problem
Hydrostatic drive transmissions in mobile machines provide an unintuitive coasting experience for operators, as they decelerate similarly regardless of terrain, differing from traditional mechanical transmissions where machines coast more downhill than uphill or on flat ground.
Innovation Solution
A system with a user input device, sensors to determine machine inclination, and a controller that adjusts the hydrostatic transmission ratio based on inclination and engine speed differences to mimic mechanical transmission coasting behavior, allowing longer coasting downhill and shorter coasting uphill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a hydrostatic drive transmission is used to provide continuously variable torque and speed, then fuel economy is improved, but the coasting behavior becomes unintuitive to operators
Solution Approach 1:
The system dynamically adjusts the transmission ratio based on real-time operating conditions (throttle position, machine speed, slope) rather than maintaining a fixed relationship. This allows the coasting behavior to adapt to terrain and operator intent, making hydrostatic transmissions feel more intuitive while preserving fuel efficiency benefits
Solution Approach 2:
The control system continuously monitors throttle position, machine speed, and slope sensors to determine operator deceleration demand. This feedback loop enables the transmission to respond appropriately to operator actions, providing intuitive coasting behavior that matches operator expectations while maintaining the fuel economy advantages of hydrostatic drives
2Device complexity
If the transmission is configured to decelerate in the same manner regardless of load or engine speed, then control simplicity is maintained, but the coasting distance becomes inconsistent with operator expectations
Solution Approach 1:
The system changes the transmission ratio parameter dynamically based on operating conditions such as throttle position, machine speed, and slope. By adjusting this key parameter in response to sensor inputs, the system achieves intuitive coasting behavior without requiring complex mechanical structures, resolving the contradiction between control simplicity and coasting predictability
3Ease of operation
If a sensor to determine machine inclination is added to adjust coasting behavior, then coasting intuitiveness is improved, but device complexity increases
Solution Approach 1:
The control system is designed to perform multiple functions: it manages normal operation, monitors throttle position, reads machine speed, determines slope from sensor input, and adjusts transmission ratio for both propulsion and coasting control. By making the control system multi-functional, the patent avoids adding separate dedicated systems for each function, thereby improving coasting intuitiveness while minimizing the increase in overall device complexity
Data Source
AI summary
A system for driving a machine is provided. A user input device inputs a desired throttle setting for the machine. The system includes an infinitely variable transmission having a transmission ratio that is adjustable. At least one sensor determines an inclination of the machine relative to a reference plane. A controller is configured to determine and apply a variable rate limit upon change in the transmission ratio based on the inclination of the machine when the desired throttle setting is reduced more than a predetermined amount and to adjust the rate limit based on the difference between an actual engine speed and a desired engine speed.