Constrained Motion Control of an Independent Metering System with Uncertain Loads

Independent metering systems (IMSs) have been applied and researched in mobile machinery due to their advantages of reduced throttling energy losses and remarkable advances under negative load through decoupling actuator throttling control. Although IMSs have the control flexibility to deal with negative workloads, the control performance of the IMSs is challenged by uncertain loads in mobile operations, limiting the control accuracy. In addition, if the motion reference is improperly specified and exceeds the constraints, the pressure of the actuator may oscillate significantly and potentially result in control instability. In this study, a constrained adaptive robust control strategy is proposed for an IMS. An adaptive robust control strategy is designed for the meter-in and meter-out throttling to achieve precision motion control despite the nonlinearities and uncertainties of the electro-hydraulic IMS. The value of the uncertain workload is estimated in real-time and utilized in the model-based controller to improve control accuracy. In addition, a constrained trajectory planning approach is presented to handle out-of-constraint references and ensure motion tracking performance. This effectively prevents pressure fluctuations caused by the inappropriate reference

Efficiency Improved Load Sensing System - Reduction of System Inherent Pressure Losses

Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different pressure levels. This paper introduces a novel hydraulic LS system architecture with reduced SIPL. In the new circuit, each actuator section is automatically connected either to the tank or to a hydraulic accumulator in dependence of its individual and the systems load situation via an additional valve. When connected to the accumulator, the additional pressure potential in the return line increases the load on the actuator and thus reduces the pressure difference to be throttled at the pressure compensator. The new circuit was developed and analyzed in simulation. For this, the hydraulic simulation model of a hydraulic excavator was used. To validate the sub-models of both machine and new circuit, two separate test rigs were developed and used. Both valid sub-models then were combined to the model of the optimized system. The final simulation results showed, that under the applied conditions, the novel hydraulic circuit was able to decrease SIPL of the examined system by approximately 44% and thus increasing the machines’ total energy efficiency. With the successful completion of the project, the gathered knowledge will be used to further develop the proposed circuit and its components

An Approach to Combine an Independent Metering System with an Electro-Hydraulic Flow-on-Demand Hybrid-System

By combining an electro-hydraulic flow-on-demand system with an independent metering of the actuators in- and outlet, a higher efficiency and a better controllability compared to conventional hydraulic-mechanic load sensing systems can be reached. It also enables the integration of a hydraulic accumulator to recuperate energy due to active loads. This paper presents an alternative control strategy for this kind of hydraulic propulsion systems. Connected with the pump and during passive loads the meter-in flow controls the velocity of the actuator. Otherwise the velocity control is achieved by the meter-out flow while the oil flows into the accumulator or tank. Exemplary this system is simulated for a mobile forestry crane. Further steps are building up a test bench for optimization and validation as well as an implementation into a real machine for testing the suitability in use

Moderne Steueralgorithmen für Forstkräne mittels künstlichen neuronalen Netzen imitieren und optimieren = Imitate and optimize modern control algorithms for forestry cranes by means of artificial neural networks

Moderne hydrostatische Arbeitsantriebe für Land- und Forstmaschinen erfordern komplexe Steueralgorithmen. Im Gegenzug bieten diese gegenüber dem Stand der Technik signifikante energetische und steuerungstechnische Vorteile, wie eine reduzierte Schwingungsneigung oder die Implementierung einer variablen Leistungsbegrenzung. Neue Algorithmen sind daher essenziell zur nachhaltigen Optimierung zukünftiger Maschinen. Am Beispiel der elektrohydraulischen Bedarfsstromsteuerung eines Forstkrans wird dargestellt, wie ein bestehender Steueralgorithmus automatisiert in ein künstliches neuronales Netz (KNN) überführt und anschließend durch den Patternsearch-Algorithmus optimiert werden kann. Die KNN-Steuerung weist bereits nach 41 Generationen optimierter Parametersätze ein der Referenzsteuerung vergleichbares Verhalten auf. Mit diesem Ansatz ist es möglich, deterministische Algorithmen in stochastische Algorithmen mit vergleichbaren Übertragungsfunktionen zu überführen, die anschließend mit Methoden des maschinellen Lernens optimiert werden können

Simulative Untersuchung zum Energiebedarf einer schreitenden Forstmaschine

Dieser Beitrag zeigt eine Möglichkeit auf, den Energiebedarf für das Voranschreiten eines Portalschreitwerks in einem frühen Stadium der Entwicklung abzuschätzen. Hierfür wird eine gekoppelte Simulation, bestehend aus Mehrkörper- und Hydraulikmodell aufgebaut. Zunächst wird die Bewegungs- und Steuerungsabfolge in der Ebene beschrieben. Die Abfolge wird für die Simulation in drei Teilbewegungen unterteilt. Diese werden jeweils mit vereinfachten Randbedingungen durchgeführt. Die Simulationen zeigen, dass für einen Bewegungszyklus eine Energie von 174 Wh benötigt wird, woraus sich ein Dieselverbrauch von 0,77 ... 0,87 l/100 m ableiten lässt

Entwicklung einer Kransteuerung auf Basis der MOBiL-Methode

In diesem Beitrag wird MOBiL auf die Entwicklung einer elektro-hydraulischen Kransteuerung angewandt. Das als Bedarfsstromsteuerung (Flow Matching, eBSS) ausgeführte System nutzt das Potential durch die Integration getrennter Steuerkanten und eines Hydraulikspeichers zur Rekuperation von Energie. In den einzelnen Entwicklungsschritten wird der Einfluss durch MOBiL berücksichtigt und Rückwirkungen von der Simulation bis hin zum finalen Einsatz in einer Forstmaschine benannt. Abschließend wird der durchgeführte Entwicklungsprozess in Bezug auf die Anforderungen der MOBiL Methode bewertet und Herausforderungen bei der Umsetzung werden aufgezeigt

Combined treatment with Sigma1R and A2AR agonists fails to inhibit cocaine self-administration despite causing strong antagonistic accumbal A2AR-D2R complex interactions: the potential role of astrocytes

Previous studies have indicated that acute treatment with the monoamine stabilizer OSU-6162 (5 mg/kg), which has a high affinity for Sigma1R, significantly increased the density of accumbal shell D2R-Sigma1R and A2AR-D2R heteroreceptor complexes following cocaine self-administration. Ex vivo studies using the A2AR agonist CGS21680 also suggested the existence of enhanced antagonistic accumbal A2AR-D2R allosteric interactions after treatment with OSU-6162 during cocaine self-administration. However, a 3-day treatment with OSU-6162 (5 mg/kg) failed to alter the behavioral effects of cocaine self-administration. To test these results and the relevance of OSU-6162 (2.5 mg/kg) and/or A2AR (0.05 mg/kg) agonist interactions, we administered low doses of receptor agonists during cocaine self-administration and assessed their neurochemical and behavioral effects. No effects were observed on cocaine self-administration; however, marked and highly significant increases using the proximity ligation assay (PLA) were induced by the co-treatment on the density of the A2AR-D2R heterocomplexes in the nucleus accumbens shell. Significant decreases in the affinity of the D2R high- and low-affinity agonist binding sites were also observed. Thus, in low doses, the highly significant neurochemical effects observed upon cotreatment with an A2AR agonist and a Sigma1R ligand on the A2AR-D2R heterocomplexes and their enhancement of allosteric inhibition of D2R high-affinity binding are not linked to the modulation of cocaine self-administration. The explanation may be related to an increased release of ATP and adenosine from astrocytes in the nucleus accumbens shell in cocaine self-administration. This can lead to increased activation of the A1R protomer in a putative A1R-A2AR-D2R complex that modulates glutamate release in the presynaptic glutamate synapse. We hypothesized that the integration of changes in presynaptic glutamate release and postjunctional heteroreceptor complex signaling, where D2R plays a key role, result in no changes in the firing of the GABA anti-reward neurons, resulting in no reduction in cocaine self-administration in the present experiments