Variable Hydraulic Motor Displacement Under Power-Limited Traction
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Solution Overview
Problem
Hydraulic drive systems in power machines often face challenges where power demand exceeds the capacity of the power source, leading to stalling and adverse effects on operation, particularly due to deficiencies or excesses in immediate power capacity.
Innovation Solution
Implementing a control device that adjusts the displacement of an infinitely variable displacement hydraulic drive motor based on commanded travel speed and output torque, allowing for continuous control of motor displacement to balance torque and speed requirements, thereby optimizing power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power source capacity is increased to meet peak power demand, then the power capacity is improved, but the system complexity and cost increase
Solution Approach 1:
The patent applies dynamics by making the motor displacement variable rather than fixed. The control system continuously adjusts the hydraulic motor's displacement based on real-time operating conditions (speed commands, torque demands, power availability), allowing the system to adapt its power delivery characteristics dynamically. This resolves the contradiction by enabling a fixed-capacity power source to deliver variable power output matching actual needs, avoiding the complexity of oversized power sources.
Solution Approach 2:
The patent changes the displacement parameter of the hydraulic motor from a constant value to a variable parameter controlled by the control system. By adjusting displacement based on power demand signals, the system optimizes power transfer efficiency and prevents power source stalling without requiring increased power source capacity, thereby avoiding additional system complexity.
2Force
If the motor displacement is increased to provide higher torque, then the torque output is improved, but the travel speed decreases
Solution Approach 1:
The patent makes motor displacement dynamic rather than fixed, allowing continuous adjustment between torque-optimized and speed-optimized settings. The control system monitors both torque demands and speed commands, adjusting displacement in real-time to achieve the optimal balance for current operating conditions, thereby resolving the fixed trade-off between torque and speed.
Solution Approach 2:
The displacement parameter is changed from a static setting to a dynamically adjusted parameter. The control system varies displacement based on the ratio of torque demand to power availability, enabling the motor to operate at different displacement points along its performance curve to simultaneously optimize both torque output and travel speed according to actual needs.
3Speed
If the motor displacement is decreased to increase travel speed, then the speed is improved, but the torque output decreases
Solution Approach 1:
The patent implements dynamic displacement control that adjusts motor displacement based on real-time torque demands. When high speed is commanded but torque demand is low, the system reduces displacement to achieve speed. When torque demand increases during high-speed operation, the system increases displacement to maintain both speed and torque, resolving the contradiction through continuous adaptation.
Solution Approach 2:
The displacement parameter is dynamically adjusted based on the relationship between speed commands and torque demands. The control system modifies displacement to optimize the speed-torque trade-off, allowing the motor to deliver high speed with adequate torque by adjusting displacement to match actual load requirements rather than operating at fixed settings.
4Power
If the power source operates at maximum capacity continuously, then the power availability is improved, but the system reliability decreases due to stalling
Solution Approach 1:
The patent implements feedback control where the control system continuously monitors power availability, torque demands, and speed commands. Based on this feedback, the system adjusts motor displacement to optimize power utilization and prevent conditions that would cause power source stalling. This feedback mechanism ensures the power source operates within safe limits while maintaining adequate power availability, thereby improving reliability.
Solution Approach 2:
The system dynamically adjusts motor displacement based on real-time power availability conditions. When power availability decreases or torque demand increases, the system reduces displacement to maintain operational stability and prevent stalling. This dynamic adaptation allows the system to maintain high power availability during normal operation while automatically reducing power demand when conditions deteriorate, preserving reliability.
Data Source
AI summary
A power machine can include a hydraulic drive system that includes an infinitely variable hydraulic drive motor. A run-time displacement of the hydraulic motor can be adjusted based on commanded travel speed or based on a output torque. In some case, the run-time displacement can be selected from one of a plurality of displacement ranges, such as a high range and a low range.