Ganged EC Pump Flow Allocation for Pressure Ripple Control
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Solution Overview
Problem
Hydraulically commutated pumps (EC pumps) experience undesirable pressure ripple and phasing effects when ganged together due to digital flow control, leading to low beat frequencies and simultaneous pulses, which are not effectively addressed by existing control systems.
Innovation Solution
A system-level controller with pressure control logic and flow allocation logic coordinates the flow commands among EC pumps, using quantized and unquantized displacement to minimize pressure ripple and phasing effects by distributing flow demands across multiple EC pumps, incorporating a pressure controller and flow divider to manage pressure and flow allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple EC pumps are ganged together to provide high-pressure fluid, then the system can meet high fluid power demands, but pressure ripple and phasing effects increase due to digital flow control
Solution Approach 1:
The system divides the total flow demand into separate quantized flow commands for each EC pump. The flow divider segments the overall flow requirement and distributes it across multiple pumps, each operating with quantized displacement values. This segmentation allows individual pump contributions to be controlled independently, reducing the phasing effects and pressure ripple that would occur if all pumps operated synchronously with full digital flow control.
2Measurement precision
If digital flow control is used in EC pumps, then precise flow regulation is achieved, but low beat frequencies and simultaneous pulses occur when pumps are ganged
Solution Approach 1:
The system applies different control qualities to different pumps based on system needs. Some EC pumps operate with quantized displacement (local quantization) while others may operate with continuous displacement. This local differentiation in control quality allows the system to maintain precise flow regulation where needed while introducing damping effects in other pumps to reduce beat frequencies and improve overall pressure stability.
3Adaptability or versatility
If EC pumps operate with full displacement range, then flow flexibility is maximized, but pressure control stability deteriorates due to ripple effects
Solution Approach 1:
The system dynamically adjusts the displacement mode of individual EC pumps based on operating conditions. The flow divider and controller can switch between quantized and continuous displacement modes for different pumps depending on the current flow demand and pressure stability requirements. This dynamic adaptation allows the system to maintain flow flexibility when stability is less critical while ensuring pressure control stability when ripple effects become problematic.
Data Source
AI summary
A hydraulic circuit arrangement includes a plurality of electronically-commutated pumps providing flow to a common hydraulic line, the plurality of electronically-commutated pumps including one or more quantized electronically-commutated pumps and one or more unquantized electronically-commutated pumps. A controller includes a pressure controller and a flow divider. The pressure controller is configured to receive a pressure signal corresponding to the pressure within the common hydraulic line, to compare the pressure signal to a demanded pressure, and to determine a target flow value required to produce the demanded pressure. The flow divider is configured to receive the target flow value and allocate the target flow value into a quantized target flow value for allocation among the one or more quantized electronically-commutated pumps and an unquantized target flow value for allocation among the one or more unquantized electronically-commutated pumps.