Hydraulic Pump Motor Acceleration Control Under Power Limits
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Solution Overview
Problem
Existing hydraulic drive systems for electrically driven hydraulic work machines, such as excavators, face inefficiencies in pump performance and excessive power consumption due to constant rotation speed control, leading to reduced responsiveness and battery life, especially when handling varying load pressures.
Innovation Solution
A hydraulic drive system that adjusts the angular acceleration of the electric motor based on hydraulic power consumption, limiting it within a preset maximum allowable power to optimize rotation speed control, ensuring efficient power use and maintaining responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric motor maintains constant rotation speed to ensure responsiveness, then the system responsiveness is improved, but the power consumption increases and battery life is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from constant rotation speed control to variable rotation speed control. The electric motor's rotation speed is dynamically adjusted based on actual hydraulic load conditions, allowing the system to maintain responsiveness when needed while reducing power consumption during low-load operations. This is achieved through a control device that calculates required rotation speed based on hydraulic pressure, flow rate, and load characteristics.
Solution Approach 2:
The patent changes the operational parameters of the electric motor by adjusting rotation speed according to hydraulic load conditions. Instead of maintaining a fixed parameter (constant speed), the system varies the rotation speed parameter based on real-time hydraulic pressure and flow rate measurements, optimizing the balance between responsiveness and power consumption.
2Use of energy by moving object
If the electric motor rotation speed is reduced to increase hydraulic pump efficiency, then energy consumption is reduced, but the system responsiveness deteriorates
Solution Approach 1:
The system dynamically adjusts the electric motor's rotation speed based on actual hydraulic load requirements rather than maintaining a fixed low speed. When hydraulic actuators require rapid movement, the control device increases rotation speed to maintain responsiveness. During low-demand periods, the speed is reduced to optimize pump efficiency and minimize energy consumption.
Solution Approach 2:
The patent implements feedback control by continuously monitoring hydraulic pressure and flow rate conditions, then using this information to adjust the electric motor's rotation speed. The control device receives feedback from hydraulic system conditions and dynamically modifies motor speed to maintain optimal performance, ensuring responsiveness is preserved when hydraulic demand increases.
3Speed
If the electric motor rotation speed is rapidly increased to meet sudden hydraulic demand, then the system responsiveness is improved, but excessive current is generated reducing battery life
Solution Approach 1:
The control device performs preliminary calculations to determine the required rotation speed before the motor actually accelerates. By pre-calculating the optimal speed based on hydraulic load conditions, the system can smoothly transition to the required speed rather than abruptly accelerating, preventing excessive current spikes that would harm battery life while still meeting hydraulic demand promptly.
Solution Approach 2:
The system dynamically controls the acceleration profile of the electric motor based on hydraulic load characteristics. Instead of fixed rapid acceleration, the control device adjusts the rate of speed increase to match the actual hydraulic demand, preventing excessive current generation during transient conditions while maintaining system responsiveness.
Data Source
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AI summary
In a hydraulic drive system for an electrically driven hydraulic work machine that executes flow rate control of an hydraulic pump by controlling a rotation speed of an electric motor to drive a hydraulic pump to supply a hydraulic fluid to a plurality of actuators, and power consumed by the electric motor reliably limited within a range of preset maximum allowable power without unnecessary degradation of responsiveness of the electric motor. To this end, a controller 50 includes a maximum angular acceleration limitation section (allowable rate computation section 50n and rate limitation section 50j), computes hydraulic power consumed by a main pump 2, computes a maximum angular acceleration allowed for an electric motor 1 on the basis of a magnitude of the hydraulic power and a preset maximum allowable power consumable by the electric motor 1, and limits an angular acceleration of the electric motor 1 not to exceed the maximum angular acceleration.