Hybrid Construction Machine Torque Control for State of Charge Stability
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Solution Overview
Problem
Existing hybrid construction machines face inefficiencies in power management, leading to excessive electric power consumption and potential engine stall when the state of charge of the electric storage device falls below a target level, due to the complexity of operation mode discrimination and torque output characteristics.
Innovation Solution
A hybrid construction machine with a control system that calculates a motor torque command value based on the torque margin between the maximum engine torque and actual engine torque, restricting the assist output of the motor generator to prevent excessive engine assist and maintain a stable state of charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor generator provides excessive assist when state of charge is low, then the engine output is improved, but the state of charge decreases rapidly causing engine stall
Solution Approach 1:
The control system dynamically adjusts the motor generator assist output based on real-time state of charge levels and engine torque requirements. When SOC is low, the system automatically reduces assist torque to prevent excessive discharge, while maintaining adequate engine output through coordinated control of engine torque and reduced motor assist.
Solution Approach 2:
The system changes the operating parameters of the motor generator based on state of charge conditions. When SOC falls below threshold levels, the control means modifies the motor torque command value to reduce assist output, thereby changing the power distribution parameters to maintain SOC stability while preserving sufficient engine output.
2Use of energy by moving object
If the operation mode discriminating means and torque output characteristics are implemented, then the power running assist is controlled, but the device complexity increases
Solution Approach 1:
The invention extracts and eliminates the complex operation mode discriminating means and detailed torque output characteristic maps from the control system. Instead, it implements a simplified control approach that directly monitors state of charge and engine torque parameters, using a more straightforward control logic to achieve effective power management without unnecessary complexity.
Solution Approach 2:
The control system uses readily available sensor data (engine torque, state of charge) to automatically adjust motor generator output without requiring complex external control algorithms or additional discrimination mechanisms. The system serves itself by making real-time adjustments based on direct feedback from existing sensors, eliminating the need for elaborate control structures.
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 enables efficient use of the state of charge, reducing electric power consumption and preventing engine stall by dynamically adjusting the assist output based on the torque margin and state of charge, thereby simplifying the control structure.
Implementation Method 1
a motor generator coaxially and mechanically connected to the engine to perform a generator operation and an electric motor operation
Implementation Method 2
an electric storage device which supplies power to the motor generator
Data Source
AI summary
In a hybrid construction machine, there is provided a drive control device which realizes in, as a simple a structure as possible, control means of a motor generator, which is capable of preventing rapid decreases in the state of charge. The control means, which calculates a motor torque command value to be output to the motor generator, is characterized by calculating the motor torque command value, based on a difference between an actual state-of-charge and a prescribed target state-of-charge and a torque margin obtained by a difference between a maximum torque of an engine determined based on an actual rotational speed of the engine and an actual torque of the engine.