Modeling and Analysis of Hydraulic Load Sensing Strategies in Off Highway Equipment

This thesis titled “Modeling and Analysis of Hydraulic Load Sensing Strategies in Off Highway Equipment” consists of two parts. The first part is called “Modeling and Analysis of an Excavator System’ and the title of the second part is “Modeling and Analysis of Tractor Rear Hitch Controls.” The topics discussed in this thesis include modeling of an excavator sytem and the modeling of an agricultural tractor’s rear hitch controls. The objectives of this thesis have been to develop a fast simulation model to replicate the functioning of an excavators system and the analysis of a tractor rear hitch controls. Both topics are of substantial importance in today’s industrial research scenario. With a large demand being placed on more intelligent development of construction and agricultural equipment to meet the changing needs of the worlds economy, this thesis offers its contribution in the meeting of these requirements. These two parts of this thesis are based on the following papers published at various conferences and journals. • Casoli P., Vacca A., Anthony A., Berta G.L. (2010) Numerical and Experimental Analysis of the Hydraulic Circuit for the Rear Hitch Control in Agricultural Tractors. 7th International Fluid Power Conference, (pp. 51-63, vol. 1) Aachen, 22-24/03 2010, ISBN 978-3-940565-90-7 • Alvin Anthony, Paolo Casoli, Andrea Vacca. (2010) .Analysis of a tractor rear hitch control system. Proc. Of 6th FPNI-PhD Symposium West Lafayette, 15-19 June 2010, pp. 589-602. FPNI Fluid Power Net Publications, 2010 • Casoli P., Vacca A., Anthony A., Berta G.L. (2011) Modellazione e verifica sperimentale del circuito oleodinamico di controllo del sollevatore posteriore di trattori agricoli. Proc of UNACOMA, 13 April 2011, Bologna, Italy. • Paolo Casoli, Alvin Anthony, Modeling of an Excavator – Pump Nonlinear Model and Structural Linkage/Mechanical Model, Proc. Of 12th Scandinavian International Conference on Fluid Power, May 18-20, 2011, Tampere, Finland • Paolo Casoli, Alvin Anthony, Manuel Rigossi (2011), Modeling of an Excavator System - Semi Empirical Hydraulic Pump Model, SAE Commercial Vehicle Congress 2011, September 2011, Rosemont, IL, USA • Paolo Casoli, Alvin Anthony, Manuel Rigossi (2011), Modeling of an Excavator System - Semi Empirical Hydraulic Pump Model, SAE Commercial Vehicle Journal, October 2011, Rosemont, IL, USA • Paolo Casoli, Alvin Anthony, Gray Box Modeling of an Excavator’s Variable Displacement Hydraulic Axial Piston Pump for Fast Simulation of Excavation Cycles, Journal of Control Engineering Practice – Elsevier Publciations (under review) • Paolo Casoli, Andrea Vacca, A. Anthony, Gian Luigi Berta, Modellazione della valvola di controlloo di un sollevatore agricolo, O&P - Oleodinamica Pneumatica - Gennaio 2012 • Alvin Anthony, Alessandro Ottala, Paolo Casoli, Cesare Dolcin, Antonio Lettini, Modeling and Verification of an Excavator System – Axial Piston Pump, Kinematics and Prime Mover Models, Proc. Of 7h FPNI-PhD Symposium Modena. FPNI Fluid Power Net Publications, 2012 PART 1 This part describes the results of a study focused on the mathematical modeling of an excavator hydraulic system. From the viewpoint of designing and tuning an efficient control system, an excavator is a very complex nonlinear plant. To design and tune such a complex control system an extremely good nonlinear model of the plant is necessary. The problem of modeling an excavator is considered in this document; a nonlinear mathematical model of an excavator has been developed using the AMESim® modeling environment to replicate actual operating conditions. The excavator model is described by detailed models of the main pump, mobile valve block, actuators and a completely developed kinematic model. The objective of this research is to develop a complete simulation model of an excavator with the capability of reproducing the actual characteristics of the system. This part presents the developed model of a complete excavator system with detailed verification of individual components and preliminary results of a complete excavator system. PART 2 This part of the thesis describes the work carried out towards mathematical modeling and analysis of a tractor rear hitch control valve (HCV). The HCV operates in two modes namely lifting and lowering. The lifting circuit incorporates a pressure compensated flow control valve, while the lowering circuit is gravity assisted. The HCV is a load-sensing system; load-sensing systems and pressure compensated valves are classified as feedback systems. Systems with feedback offer scope for tuning and towards this objective the pressure compensator has been linearised and its characteristics analyzed. The objective of this study is to develop a complete mathematical model of the HCV. This would help to better understand its functionality and to quantify the energy losses across its components