Adaptive Powershift Shift Points for Stable Tractive Force
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Solution Overview
Problem
In battery-electric driven working machines, gear shifting requires additional power to compensate for rotor inertia, leading to potential drops in tractive force, which can cause unsteady driving behavior and insufficient power supply for work equipment.
Innovation Solution
An adaptive method for setting shift points in a multi-speed powershift transmission, using a control device to determine a driving speed where the specified tractive force is maintained during shifting operations by connecting sensors to the electric drive system and powershift transmission, allowing gear changes to occur at optimal speeds based on battery state and tractive force requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gear shifting is performed in a multi-speed powershift transmission, then the working machine can adapt to different driving requirements and maintain optimal performance ranges, but additional power is required to compensate for rotor inertia causing drops in tractive force
Solution Approach 1:
The control device determines a shift point based on the state variable and specified tractive force before the shifting operation occurs. This preliminary determination allows the system to plan the shift in advance, selecting an optimal speed where the tractive force remains essentially maintained during the transition, thereby preventing harmful drops in tractive force while enabling gear adaptation.
Solution Approach 2:
The method uses feedback from state variables of the electric drive system (such as battery charge state, motor speed, torque) to dynamically determine the shift point. The control device continuously monitors system state and adjusts the shift point accordingly, ensuring that shifting occurs at the optimal moment when tractive force can be maintained, thus resolving the contradiction between adaptability and force stability.
2Force
If additional power is provided to compensate for rotor inertia during downshifting, then the tractive force can be maintained, but the power consumption from the battery increases
Solution Approach 1:
The method dynamically changes the shift point parameter based on the state variable of the electric drive system. By adjusting the shift point according to battery charge state, motor operating conditions, and tractive force requirements, the system identifies optimal shifting speeds that minimize the additional power needed for compensation, thereby maintaining tractive force while reducing energy consumption.
Solution Approach 2:
The shift point is not fixed but dynamically determined based on real-time system state. This dynamic approach allows the control device to adapt the shifting strategy to current operating conditions, selecting shift points that optimize the balance between maintaining tractive force and minimizing additional power requirements from the battery.
3Device complexity
If fixed shift points are used in the transmission, then the control system is simpler, but the tractive force cannot be maintained during shifting operations under varying operating conditions
Solution Approach 1:
The control device uses feedback from state variables (battery charge state, motor speed, torque, temperature) to dynamically determine the shift point. This feedback mechanism allows the system to adapt to varying operating conditions and maintain tractive force during shifting, while keeping the control logic relatively simple by using pre-defined evaluation criteria based on the state variables.
Solution Approach 2:
The method changes the shift point parameter dynamically based on operating conditions rather than using fixed values. The control device calculates the shift point as a function of state variables, allowing the system to maintain tractive force under varying conditions without requiring complex control algorithms, thus balancing simplicity and performance.
Data Source
AI summary
A method for adaptively setting a shift point of a multi-speed powershift transmission of a working machine that includes an electric drive system and a control device. The electric drive system has a battery and an electric motor. The multi-speed powershift transmission is connected to the electric drive system. The control device is connected to the electric drive system and the multi-speed powershift transmission in a signal-effective manner. The method includes specifying a tractive force which must be present during shifting operations of the multi-speed powershift transmission, determining a state variable of the electric drive system, and determining based on the state variable and the specified tractive force, a driving speed at which the specified tractive force is essentially maintained during the shifting operation. The method includes setting the shift point at the determined driving speed and carrying out the shifting operation at the shift point.