Work Machine Hydraulic Pump Control for Travel Deflection
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Solution Overview
Problem
Work machines with variable displacement hydraulic pumps experience deflection in travel due to hysteresis characteristics, leading to unequal hydraulic oil delivery between left and right sides, despite equal operation of travel control levers.
Innovation Solution
Incorporating first and second hydraulic motors, swash plate angle sensors, a delivery amount setting unit, and a command value control unit to adjust the swash plate angle and correct command values, ensuring equal hydraulic oil delivery between sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable displacement hydraulic pump is used to supply hydraulic oil, then the amount of delivery can be varied with swash plate position, but hysteresis characteristics cause unequal delivery between left and right sides despite equal operation of travel control levers
Solution Approach 1:
The patent employs feedback control by detecting the actual swash plate angles with sensors, comparing them to target angles, and generating correction commands to eliminate deviations. This closed-loop feedback mechanism compensates for hysteresis effects and ensures equal delivery amounts between left and right hydraulic pumps when travel control levers are operated equally.
Solution Approach 2:
The patent changes the control parameter from direct swash plate angle control to corrected angle control. By calculating correction amounts based on detected angle deviations and applying these corrections to the command values, the system adjusts the swash plate angles to achieve equal delivery amounts despite hysteresis characteristics.
2Device complexity
If swash plate angle is controlled by sensing command current to proportional solenoid valve, then control is simplified, but hysteresis characteristics cause deflection in travel
Solution Approach 1:
The patent introduces feedback control by detecting actual swash plate angles with sensors and comparing them to target angles. The detected angle information is fed back to the control system, which generates correction commands to eliminate angle deviations. This feedback mechanism maintains travel linearity while preserving the simplicity of electrical control.
Solution Approach 2:
The patent replaces direct mechanical linkage control with electrical control based on sensor feedback. Instead of relying solely on mechanical position sensing, the system uses electrical sensors to detect swash plate angles and processes this information electronically to generate correction commands, improving control precision while maintaining simplicity.
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
This solution effectively suppresses deflection in travel by ensuring equal hydraulic oil delivery to both sides, achieving linear travel and reducing energy loss by minimizing the number of components.
Implementation Method 1
An amount of delivery by the hydraulic pump in response to a command current, however, has hysteresis characteristics
Data Source
AI summary
A work machine includes first and second hydraulic motors, first and second hydraulic pumps provided to supply hydraulic oil in correspondence with the first and second hydraulic motors, respectively, first and second swash plate angle sensors provided in correspondence with swash plates which regulate amounts of delivery by the first and second hydraulic pumps, respectively, the first and second swash plate angle sensors each detecting an angle of the swash plate, a delivery amount setting unit which sets an ideal amount of delivery by the first and second hydraulic pumps, and a command value control unit which corrects a command value for adjusting an angle of the swash plate such that the amount of delivery in accordance with a result of detection by the first and second swash plate angle sensors is set to the ideal amount of delivery.