Variable-Speed Pump Torque Control via Displacement Adjustment
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Solution Overview
Problem
Hydrostatic pumps with variable displacement volume driven by speed-variable drives face challenges in managing load pressures and drive torque, leading to potential overload and thermal damage, especially during dynamic operating states.
Innovation Solution
The implementation of a control system that adjusts displacement volume based on load torque and drive moment, using filter functions to decouple drive torque from load pressure, ensuring optimal engine load and preventing overload by specifying setpoints for displacement volume that limit drive torque within safe limits, particularly by using a PDT1 filter function for dynamic states and a PDDT1 function for static states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If displacement volume is increased to meet high load pressure demands, then pumping capacity is improved, but drive torque increases causing overload and thermal damage
Solution Approach 1:
The patent applies dynamics by making the displacement volume adjustable and controllable in real-time based on operating conditions. The control system dynamically adapts the displacement volume to match actual load requirements, preventing both overload and underutilization of the drive system
Solution Approach 2:
The patent changes the parameter of displacement volume based on detected operating states (dynamic vs. static). By switching between different displacement volume setpoints according to the operating state, the system optimizes the balance between pumping capacity and drive torque
2Speed
If displacement volume is rapidly adjusted to respond to dynamic load changes, then responsiveness is improved, but system stability deteriorates
Solution Approach 1:
The control system performs preliminary classification of the operating state (dynamic or static) before adjusting displacement volume. This preliminary assessment allows the system to select appropriate control strategies in advance, preventing unstable rapid adjustments
Solution Approach 2:
The patent implements dynamic control by adapting the displacement volume adjustment strategy based on the detected operating state. In dynamic states, the system allows faster response while in static states, it maintains stability through more conservative adjustment
Data Source
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AI summary
The invention relates to a method for operating a variable speed pump (120) in which a conveying unit (122) adjustable in a displacement volume per working cycle is driven by means of a variable speed drive (121), comprising determining a load torque on the variable speed pump (120) as a function of an operating condition, and specifying a setpoint (VPu,Set) for a characteristic parameter determining the displacement volume per working cycle such that a drive torque of the variable speed drive (121) corresponds at most to a peak drive torque (Man,max) of the drive (121) or a continuous drive torque (Man,0) of the drive (121).