This article investigates the steady-state performance of a closed-circuit hydrostatic summation drive used in heavy earth moving machine through modelling and experiment. The proposed drive basically consists of variable displacement pump and bent-axis motor. The performance studies of the drive have been made for its two different modes of operation: using single motor and two motors. Bondgraph simulation technique is used to model the drive, where various losses are lumped into suitable resistive elements. The relationships of the losses with the state variables obtained from the model are identified through experiments. The dependencies of the loss characteristics on the load torque and the pump displacement ratio are studied. The model has been verified experimentally. The performances of the hydrostatic drives are studied at different torque levels with respect to its slip, torque-loss and overall efficiency, using the expressions describing the characteristics of the loss-coefficients. The investigation also identifies the operating range of the proposed hydrostatic drives with reasonable efficiency.

This article investigates the dynamic performance of a closed-circuit hydrostatic summation drive that has been carried out through system modeling and simulation. The proposed drive consists of a variable displacement piston pump and bent axis motors. The performances of the hydrostatic drive have been studied for its two different modes of operations, using single motor and two motors. The changing over of the drive mode is accomplished by on-/off-controlled direction control valve. Bondgraph simulation technique is used to model the hydrostatic drives. The characteristics of the loss coefficients of the drive are obtained from the steady-state model and they are identified through experimental investigation. Using them, the overall dynamic model of the hydrostatic drive has been validated experimentally. With respect to some critical parameters, the performances of the hydrostatic drive have also been studied.

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Hydrostatic drive • Bondgraph modeling • High speed low torque (HSLT) • Low speed high torque (LSHT) • Hydro-motor • Loss coefficients • Slip • Torque loss • Efficiency • Rock strength List of symbols D p Volume displacement rate of the pump (m 3 /rad) D pmax Maximum volume displacement rate of the pump (m 3 /rad) D mh,ml Volume displacement rate of the HSLT or LSHT hydro-motor (m 3 /rad) J ld Generalized load inertia of the driving shaft (Kg m 2) J ldh,ldl Load inertia of the HSLT or LSHT driving shaft (kg m 2) K cp Bulk stiffness of the fluid at pump plenum (N/m 5) K cmh,cml Bulk stiffness of the fluid at HSLT or LSHT hydro-motor plenum (N/m 5) M ih,il Angular momentum due to load inertia of the HSLT or LSHT drive (kg m 2 /s 2) M ih,il Torque due to load inertia of the HSLT or LSHT driving shaft (Nm) N mah,mal Actual rotational speed of the HSLT or LSHT hydrostatic drive (rad/s) N mi Ideal rotational speed of the hydrostatic drive (rad/s) N mih,mil Ideal rotational speed of the HSLT or LSHT hydrostatic drive (rad/s) N mp Predicted rotational speed of the hydrostatic drive (rad/s) N p Speed of the pump (rad/s) P lmh,lml Load pressure of the HSLT or LSHT hydromotor (N/m 2

This article presents a brief note on the evolution of steering mechanisms and more emphasized on articulated steering system of the load haul dump machine. In this respect, pictorial representation of the evolution of steering mechanisms for on-road and articulated steering mechanisms of the load haul dump machine is made from the available literature. Critical review on basic elements required for the complete automation of the load haul dump vehicle steering system is presented. Different types of controllers for path tracking error minimization of the scale-modeled or simulated model of the load haul dump steering system are tabulated. Few case studies stimulating the complete automation of the load haul dump steering system employed on the field are also discussed. Challenges and some research gaps in making fully automated steering system of the load haul dump machine are identified in this review article. At the end, based on the critical review, some novel methods for making the fully automated steering system of the load haul dump machine is provided, which is the potential future work for the design and development of feasible automatic steering system.