Hydraulic Pump Motor Generator Speed Torque Control Switching
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Solution Overview
Problem
Conventional hybrid construction machines experience fluctuations in engine rotational speed and torque due to the lack of synchronization between engine combustion cycles and motor generator control, leading to unstable operation and potential hunting issues, as well as over-charging of electrical storage devices.
Innovation Solution
Implementing a control switching mechanism in the motor generator control unit that switches between torque control and rotational speed control based on power demand and engine speed, maintaining maximum torque and stabilizing rotational speed, while also adjusting target torques to prevent over-speed and over-charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If rotational speed control is applied to synchronize motor generator with engine combustion cycles, then fuel economy and emission performance improve, but engine rotational speed and torque fluctuations increase due to combustion cycle variations
Solution Approach 1:
The control method dynamically adjusts the target rotational speed of the motor generator based on the detected rotational speed fluctuations of the engine. By making the control target adaptive rather than fixed, the system accommodates natural combustion cycle variations while maintaining synchronization for fuel efficiency.
Solution Approach 2:
The system continuously detects the actual rotational speed of the engine and uses this feedback to adjust the target rotational speed of the motor generator. This closed-loop control compensates for fluctuations caused by combustion cycles, preventing hunting while maintaining energy efficiency.
2Power
If motor generator torque is increased to assist engine during high load, then power output improves, but electrical storage device may become over-charged
Solution Approach 1:
The control method monitors the state of charge of the electrical storage device and adjusts the motor generator's regenerative braking torque accordingly. When the storage device is nearly full, the system reduces or disables regenerative charging to prevent over-charging, while still maintaining power assist capabilities.
Solution Approach 2:
The control system dynamically adjusts the power distribution between engine and motor generator based on real-time conditions including load demand and electrical storage state. This allows optimal power output while adapting the charging rate to prevent over-charging.
3Device complexity
If engine rotational speed is maintained at constant target value, then control simplicity is maintained, but hunting occurs due to synchronization mismatch with combustion cycles
Solution Approach 1:
Instead of maintaining a fixed constant target rotational speed, the system dynamically adjusts the target speed to track the engine's actual rotational speed variations. This adaptive approach maintains synchronization with combustion cycles while avoiding the complexity of predictive combustion timing control.
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 approach stabilizes engine rotational speed and torque, reduces load on the engine, and improves fuel economy and emission performance by minimizing fluctuations and preventing hunting and over-speed conditions.
Implementation Method 1
a motor generator (M/G) 31 connected to a drive shaft of the engine 15 and a rotary shaft of the hydraulic pump 21, and having a function of performing a power assist to the engine 15 and an electricity generation
Implementation Method 2
a motor generator (M/G) 31 connected to a drive shaft of the engine 15 and a rotary shaft of the hydraulic pump 21, and having a function of performing a power assist to the engine 15 and an electricity generation
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A construction machine (1) includes an engine (15), a loadestimationunit (45) that estimates a pump power absorption, aregeneration/poweringpower demand calculationunit (46) that calculates a regeneration/powering power demand according to a state of charge in an electrical storage device (34), an engine power demand calculation unit (47) that calculates an engine power demand based on the power absorption and regeneration/powering power demand, and a motor generator control unit (48) that performs rotational speed control or torque control. The control unit (48) includes a control switching unit (48A) that switches the rotational speed and the torque control according to the engine power demand and the rotational speed of the engine (15). The control switching unit (48A) switches from the torque control to the rotational speed control when during performance of the torque control, the engine power demand increases and the rotational speed of the engine (15) becomes lower than a predetermined rotational speed.