Wheel Drive Assembly Pressure Control for Variable Traction Power
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Solution Overview
Problem
Existing hydrostatic traction drives for mobile working machines lack the ability to regulate power effectively, leading to suboptimal loading of internal combustion engines and inefficient power distribution between traction drives and operating hydraulics, as current systems do not allow for variable power settings or different travel modes.
Innovation Solution
A wheel drive assembly comprising a hydraulic motor with an electrical adjusting unit and an electronic control unit that includes a pressure regulator and a feedforward controller, allowing for regulation of motor displacement based on actual and setpoint pressures, enabling variable power settings and different travel modes by maintaining a proportional relationship between motor drive current and displacement, and incorporating a rotational speed limit for safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rotational speed control is used to adjust hydraulic motor displacement, then travel speed can be adjusted, but no physical power setting is possible and optimal loading of the internal combustion engine cannot be achieved
Solution Approach 1:
The patent changes the control parameter from rotational speed to working pressure. The pressure regulator uses actual pressure and setpoint pressure as input variables to directly control motor displacement, enabling physical power setting capability while maintaining travel speed adjustment functionality.
Solution Approach 2:
The patent skips the intermediate rotational speed control step and directly regulates motor displacement through pressure control. The feedforward controller calculates the required displacement based on pressure demands, bypassing the limitations of speed-based control systems.
2Power
If hydraulically pressure-regulated hydraulic motors are used, then power regulation is possible, but the system becomes relatively cost-intensive and does not allow variable power setting
Solution Approach 1:
The patent segments the control system into distinct functional modules: a pressure regulator for pressure-based displacement control and a feedforward controller for calculating required displacement based on pressure demands. This modular approach enables power regulation while maintaining system manageability and reducing overall complexity.
Solution Approach 2:
The patent introduces an electronic control unit as an intermediary between the pressure sensor and the hydraulic motor displacement control. This intermediary processes pressure signals and translates them into appropriate displacement adjustments, enabling power regulation without requiring complex direct mechanical pressure regulation mechanisms.
3Speed
If the hydraulic pump delivery volume is increased for faster travel, then travel speed increases, but the internal combustion engine may be overloaded without optimal power distribution
Solution Approach 1:
The patent implements a feedback mechanism where the pressure regulator continuously monitors actual working pressure and compares it with the setpoint pressure. Based on this feedback, the system adjusts motor displacement to meet power demands efficiently, enabling the engine to operate at optimal load while achieving required travel speeds.
Solution Approach 2:
The patent makes the hydraulic motor displacement dynamic and adjustable based on real-time pressure conditions. The feedforward controller calculates the optimal displacement dynamically, allowing the system to adapt power distribution to match actual travel speed requirements and engine capabilities.
Data Source
AI summary
In a hydraulic motor and a hydrostatic traction drive with such a hydraulic motor, the regulating of the displacement of the hydraulic motor is done via a pilot-operated pressure regulator. The feedforward controller calculates an estimated motor displacement and relays this to the pressure regulator.