Hydraulic Pump Controller for Hybrid Work Machine Power Management
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Solution Overview
Problem
Hybrid work machines face excessive limiting on pump absorption power due to limited electric storage, leading to potential engine stalling and reduced performance during abrupt load increases, as existing solutions restrict power output to prevent stalling but limit machine performance.
Innovation Solution
A hybrid work machine with an engine, electric motor, electric storage device, monitoring device, and pump regulator, featuring an increasing rate computing section to determine allowable pump absorption power, a limited power computing section to set limited pump power, and a pump control section to manage hydraulic pump flow rate, ensuring controlled power delivery even with limited electric supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the generator motor outputs power to make up the shortfall in engine output power during abrupt load increase and the remaining electric storage amount is insufficient, then the pump absorption power is set low at the time of starting for prevention of engine stalling, but it is impossible to exhibit the performance inherent in the machine in later work
Solution Approach 1:
The pump absorption power limit is made dynamic rather than static. The control section computes the power limit based on real-time electric storage device information, allowing the system to adapt the power limit to current battery state. This resolves the contradiction by enabling high power output when battery charge is sufficient while preventing stalling when charge is low, thus maintaining both reliability and productivity across different operating conditions.
Solution Approach 2:
The system changes the parameter of pump absorption power limit based on the state of the electric storage device. By monitoring battery charge levels and adjusting the power limit accordingly, the system optimizes the balance between preventing engine stalling and maintaining machine performance. This parameter adaptation allows the machine to exhibit full performance capability when energy resources permit while ensuring operational reliability when they do not.
2Reliability
If the maximum value of pump absorption power is limited in response to the remaining electric storage amount, then the lug-down and engine stalling are suppressed, but the machine cannot exhibit its inherent performance
Solution Approach 1:
The power limit is transformed from a fixed constraint to a dynamic value that adjusts based on electric storage device information. The control section continuously monitors battery state and computes appropriate power limits, enabling the system to maximize pump absorption power when battery charge is sufficient while preventing lug-down and engine stalling when charge is insufficient. This dynamic adjustment resolves the contradiction between reliability and power output.
Solution Approach 2:
The system implements feedback control by monitoring the electric storage device information and using it to adjust the pump absorption power limit. The control section receives real-time information about battery charge levels and adjusts the power limit accordingly, creating a closed-loop control system that maintains reliability while maximizing power output under varying energy conditions.
Data Source
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AI summary
A hybrid work machine that can suppress excessive limiting on pump absorption power even in a situation in which supply of electric power to an electric motor is limited is provided. The hybrid work machine includes: an engine 22; an assist generator motor 23 connected to the engine 22 in such a manner that a torque can be transmitted to the engine 22; an electric storage device 24 that supplies electric power to the assist generator motor 23; a monitoring device 28 that monitors the electric storage device 24 and that acquires electric storage device information; a hydraulic pump 41 driven by the engine 22 and the assist generator motor 23; and a pump regulator 43 that regulates a delivery flow rate of the hydraulic pump 41. The hybrid work machine includes: an increasing rate computing section 81 that computes an allowable increasing rate r in response to the electric storage device information for pump absorption power; a limited power computing section 82 that computes a limited value WPlim of the pump absorption power on the basis of the allowable increasing rate r; and a pump control section 86 that controls the delivery flow rate of the hydraulic pump 41 in response to the limited pump power WPlim.