Hybrid Drive Control for Torque Converter Slip in Working Machines
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Solution Overview
Problem
Existing hybrid drive systems in working machines face inefficiencies due to the interaction between the driveline and work hydraulics, particularly during bucket fill actions, leading to high torque converter slip and energy losses.
Innovation Solution
A control method and system that identifies repetitive loading cycles and bucket fill actions to discharge a majority of the energy stored in the energy storage system to the drive shaft for vehicle propulsion, reducing reliance on the combustion engine and minimizing torque converter slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the energy storage system is charged during braking to improve energy recovery, then energy efficiency is improved, but the energy storage system may not have sufficient energy available during high-demand operations like bucket fill actions
Solution Approach 1:
The control system dynamically adjusts the discharge strategy based on real-time operating conditions. During bucket fill actions, the system prioritizes discharging the energy storage system to provide maximum power assistance, while during normal operation or braking, it charges the system. This dynamic switching resolves the contradiction by adapting energy flow direction to operational needs.
Solution Approach 2:
The control system continuously monitors the state of charge of the energy storage system and the current operational demands. When a bucket fill action is detected, the feedback loop triggers a discharge command to ensure sufficient energy is available. This feedback mechanism ensures the system maintains optimal energy availability while maximizing recovery efficiency during appropriate phases.
2Power
If the combustion engine operates at high power to meet peak demand during bucket fill actions, then power availability is improved, but fuel consumption and energy losses increase
Solution Approach 1:
The system merges the power output of the combustion engine with the energy storage system to create a hybrid power source. During bucket fill actions, both the engine and the discharged energy storage system contribute to meeting peak power demands. This combination allows the engine to operate at lower, more efficient power levels while still achieving the required total power output, thereby reducing fuel consumption.
Solution Approach 2:
The energy storage system is charged during braking and lower-demand phases in advance of peak power requirements. This preliminary charging ensures that when bucket fill actions occur, the energy storage system is ready to discharge and assist the engine, reducing the need for the engine to operate at high power levels and thus lowering fuel consumption.
3Force
If the torque converter operates with high slip to provide high torque multiplication during bucket fill actions, then torque availability is improved, but energy losses in the torque converter increase
Solution Approach 1:
The energy storage system acts as an intermediary between the engine and the drivetrain during bucket fill actions. By providing additional power through the gearbox and drive shaft, it reduces the reliance on torque converter slip for torque multiplication. This intermediary power source allows the torque converter to operate with reduced slip, thereby lowering energy losses while maintaining sufficient torque availability.
4Use of energy by moving object
If the control system discharges the energy storage system during bucket fill actions to improve fuel efficiency, then energy efficiency is improved, but the state of charge of the energy storage system decreases
Solution Approach 1:
The control system implements periodic charging and discharging cycles of the energy storage system. During bucket fill actions, the system discharges to improve fuel efficiency. During braking events or lower-demand phases, the system charges to restore the state of charge. This periodic action ensures that the energy storage system maintains a sustainable cycle of use, improving overall fuel efficiency while preventing complete depletion.
Data Source
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AI summary
A method for controlling a hybrid drive system in a working machine, the system comprising: an internal combustion engine; a torque converter having an input shaft operatively coupled to the engine and an output shaft operatively coupled to a gearbox; an energy storage system operatively coupled to the gearbox for providing power to and receiving power from a drive shaft via the gearbox, said drive shaft being operatively coupled to propulsion means of the working machine; and work hydraulics operatively connected to the engine; the method comprising: determining a torque converter slip; and if the torque converter slip is above a predetermined threshold level, discharging the energy storage system to provide energy stored in the energy storage system to the drive shaft for vehicle propulsion.