Hydrostatic Motor Characteristic Curve Calibration for Traction Drives
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Solution Overview
Problem
Current methods for adjusting the characteristic curve of hydrostatic motors in traction drives of work machines are costly, inaccurate, and do not account for vehicle-specific tolerances, often requiring complex procedures, additional costs, or leading to excessive maximum velocity control.
Innovation Solution
A method that sets the pivot angle of the hydrostatic motor based on desired velocity, checks predefined conditions, and corrects the control function to match the desired velocity, using a volumetric flow balance and adjusting the motor's current until the velocity difference is within predefined limits, ensuring accurate and efficient control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the work machine is lifted to adjust the motor pivot angle for maximum velocity, then the characteristic curve can be calibrated, but additional costs and complexity are incurred
Solution Approach 1:
The control unit automatically performs the characteristic curve calibration by itself during normal operation. The system uses its own sensors and actuators to measure the actual velocity, compare it with the desired velocity, and adjust the motor pivot angle without requiring external lifting equipment or manual intervention. This self-service approach eliminates the need for complex external adjustment procedures while maintaining calibration accuracy.
2Ease of manufacture
If project-specific settings are performed at the motor production line, then the hardware electroproportional controller can be configured, but high costs and limited accuracy are incurred
Solution Approach 1:
The system performs preliminary configuration of the control function during normal operation before actual use. The control unit stores a preliminary control function that is then automatically adjusted and optimized during the calibration process based on actual vehicle-specific tolerances and performance requirements. This preliminary action allows for easy initial setup while enabling subsequent precision optimization.
Solution Approach 2:
The control function parameters are dynamically adjusted based on measured performance data. The system modifies the control parameters to account for vehicle-specific tolerances in the hydrostatic transmission components, transforming the fixed project-specific settings into adaptive, precision-tuned parameters that match the actual vehicle characteristics.
3Measurement precision
If the characteristic curve is determined at the component line, then calibration data can be generated, but complexity and costs for data transfer are incurred
Solution Approach 1:
The calibration process merges the determination of characteristic curve data with the normal operation of the vehicle. Instead of separating the data generation and transfer processes, the system performs calibration during regular operation, combining measurement, computation, and adjustment into a single integrated process that eliminates the need for separate data transfer infrastructure.
4Reliability
If a terminal velocity controller is used to control erroneous motor adjustments, then the controller behavior can be managed, but the maximum velocity is initially exceeded
Solution Approach 1:
The system uses feedback from the actual velocity measurement to continuously adjust the motor pivot angle. The control unit compares the measured actual velocity with the desired velocity and automatically adjusts the control function to eliminate the difference. This feedback mechanism ensures that maximum velocity is accurately controlled without initial overshoot, as the system learns and adapts to the actual vehicle characteristics during calibration.
Data Source
AI summary
A method teaches a control function, preferably a characteristic curve, of a hydrostatic motor of a traction drive of a work machine when in drive mode. The traction drive is provided with the hydrostatic motor and a hydrostatic pump, which is hydraulically connected to the hydrostatic motor. The method includes setting a pivot angle of the hydrostatic motor while taking into account a desired velocity of the work machine when in the drive mode, and checking whether predefined conditions are met. If the predefined conditions are met and a current velocity differs from the desired velocity, the method includes correcting the control function of the hydrostatic motor by taking into account a difference between the desired velocity and the current velocity. At least one value of the corrected control function of the hydrostatic motor is taught during the correcting.