Modelling and Control of a Regenerative Hydraulic System for Liftras LT-1500 Crane
Authors
Ludvigsen, Allan Thusholt ; Smed, Magnus Grundtdal
Term
4. term
Education
Publication year
2024
Submitted on
2024-05-31
Pages
117
Abstract
This thesis investigates replacing the LT‑1500 crane’s conventional hydraulic architecture with a regenerative design to cut energy use while maintaining load-holding safety. The proposed system substitutes the load control valve with a safety valve comprising an inverse shuttle valve and two pilot‑operated valves that preserve load holding but require a minimum opening pressure, and adds a pump between the cylinder chambers to enable four‑quadrant operation and energy regeneration. Simulation models of both the reference and proposed systems were developed and validated, covering boom kinematics with payload, hydraulics, motor dynamics, inverter efficiency, and a battery model with State of Charge. A virtual‑state control approach based on input/output transformation decouples pressure and velocity dynamics and is implemented in two loops: a simple proportional load‑holding pressure controller and a motion controller combining active damping, flow feedforward, and proportional position control while enforcing a minimum pressure above the valve’s opening threshold. In simulations of representative operations, the control delivers satisfactory position and pressure tracking and substantial energy savings: energy drops by 30% in upward flips (6.27 vs 4.36 kWh), downward flips regenerate 1.43 kWh (reference consumes 3.2 kWh), and total energy for a full wind‑turbine installation is reduced by 59% (68.1 vs 27.9 kWh). The end‑of‑task battery SoC improves from 48.6% to 78.6% with the proposed system. The results indicate the regenerative hydraulic concept can significantly lower the LT‑1500’s energy consumption while preserving load‑holding performance and accurate tracking.
Denne afhandling undersøger, hvordan Liftras LT‑1500-krans konventionelle hydraulik kan erstattes af et regenerativt design for at reducere energiforbrug uden at kompromittere lasthold. Det foreslåede system udskifter den traditionelle load control valve med en sikkerhedsventil bestående af en inverse shuttle-ventil og to pilotstyrede ventiler, som bevarer lasthold men kræver et minimumstryk for at åbne, og tilføjer en pumpe mellem cylinderkamrene for firekvadrant-drift og energi-genvinding. Der er udviklet og valideret simuleringsmodeller af både reference- og forslagssystemet, herunder kranens boom-kinematik med last, hydraulik, motordynamik, invertereffektivitet og batterimodel med State of Charge. En styringsmetode baseret på virtuelle tilstande og input/output-transformation afkobler tryk- og hastighedsdynamik og anvendes i to kredsløb: en simpel proportional lastholds-trykkontrol og en bevægelsesstyring med aktiv dæmpning, flow-feedforward og proportional positionsregulering, der samtidig sikrer minimumstrykket over ventilens åbningstryk. I simulationer af repræsentative operationer leverer styringen tilfredsstillende positions- og tryksporing og markante energibesparelser: ved opadgående flip reduceres energien med 30% (6,27 mod 4,36 kWh), ved nedadgående flip regenereres 1,43 kWh (reference 3,2 kWh), og over en fuld vindmølleinstallation falder det samlede energiforbrug med 59% (68,1 mod 27,9 kWh). Batteriets SoC ved afslutning øges fra 48,6% til 78,6% med det foreslåede system. Resultaterne indikerer, at den regenerative hydrauliske løsning kan sænke LT‑1500-kranens energiomsætning betydeligt, samtidig med at lasthold og god sporingsydelse bevares.
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