Hydrostatic Transmission Load Control for Engine Stalling
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Solution Overview
Problem
Machines with dual path electronically controlled hydrostatic transmissions, such as bulldozers, often experience engine stalling during high load conditions like heavy-duty operations or uphill climbing due to inadequate load management systems.
Innovation Solution
A control system that manages engine load by controlling pump and motor displacements using a digital microprocessor-based controller, which adjusts displacement values through lookup tables and solenoids to prevent engine stalling, and includes features like load management algorithms and rate limiters to stabilize the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pump and motor displacements are increased to handle high load conditions, then load carrying capacity is improved, but engine load increases causing engine stalling
Solution Approach 1:
The control system continuously monitors engine RPM and compares it to a desired RPM setpoint. When engine RPM deviates from the setpoint (indicating high load conditions), the controller automatically adjusts pump and motor displacement commands to reduce hydraulic demand, thereby preventing engine stalling while maintaining load carrying capacity
Solution Approach 2:
The system dynamically changes the displacement parameters of the hydraulic pump and motor based on real-time engine load conditions. By adjusting these displacement parameters in response to engine RPM feedback, the system optimizes the balance between load carrying capacity and engine reliability
2Reliability
If pump and motor displacements are controlled to prevent engine stalling, then engine reliability is improved, but operator feel and machine responsiveness may deteriorate
Solution Approach 1:
The control system implements dynamic adjustment of pump and motor displacements rather than static control. The system adapts displacement commands in real-time based on engine RPM feedback, allowing the machine to respond naturally to operator inputs while preventing engine stalling. This dynamic approach maintains operator feel by preserving the direct relationship between operator control inputs and machine response
Solution Approach 2:
The load management system operates autonomously by continuously monitoring engine RPM and automatically adjusting hydraulic displacement commands without requiring operator intervention. The system serves itself by detecting engine load conditions and self-correcting displacement commands to prevent stalling, thereby maintaining both engine reliability and natural operator feel
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
The system increases load carrying capacity and maintains operator 'feel' during heavy-duty operations, preventing engine lug-down and ensuring stable performance across various machine speeds and loads.
Implementation Method 1
A control system manages engine load by controlling pump and motor displacements using a digital microprocessor-based controller, which adjusts displacement values through lookup tables and solenoids
Data Source
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AI summary
A method of managing engine load by adjusting the pump and motor displacements of a dual path electronically controlled hydrostatic transmission utilizes the difference between the reference and actual engine speeds, the temperature of the working fluid for the dual path electronically controlled hydrostatic transmission, the engine governor droop value, the vehicle speed and lookup tables to determine pump and motor command adjustment factors associated with specific engine loading conditions.