Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-018-3334-8 RESEARCH ARTICLE - MECHANICAL ENGINEERING Model-Based Performance Analysis of a Hybrid Summation Drive Used in Off-Highway Vehicles Prabhakar Kushwaha 1 · Sanjoy K. Ghoshal 2 · Kabir Dasgupta 1 Received: 6 September 2017 / Accepted: 22 May 2018 © King Fahd University of Petroleum & Minerals 2018 Abstract High power density, wide speed range and overall good efficiency are the primary demands of a modern hydrostatic trans- mission used in heavy earth moving machineries (HEMM). Conventional hydrostatic drive consisting of a displacement controlled pump and motor is sometimes inadequate to meet such requirements. Therefore, there is a need for examining alternative concepts of drives for HEMM. This article studies one of such alternatives where the motors are connected in parallel. In another solution, one motor is permanently connected to the load and the other one is connected to the load through gear unit. The latter is used during high-torque, low-speed demand of the vehicle. The challenge with the concept is the reconnection procedure, where the disconnected motor is accelerated, synchronized to the main motor output speed and finally locked to the output shaft, all in fraction of a second. Two different principles for the reconnection are proposed: to control the connection using a disc-type clutch, or to control it from the fluid power system. The performances of the two systems are compared through bond graph model simulation with respect to pressure, speed and efficiency for the varying load demand usually catered by a HEMM. Keywords Hydrostatic system · Summation drive · Single-motor mode · Two-motor mode · Bond graph · Performance analysis List of symbols a dcv Port opening area of direction control valve C Single-port energy storage capacitor element in bond graph model c d The flow coefficient d area The projected valve port opening distance D p Main pump displacement D m Motor displacement F spl Solenoid force acting on the valve spindle B Sanjoy K. Ghoshal sanjoy.ghoshal@gmail.com Prabhakar Kushwaha prabhakar.kushwaha4@gmail.com Kabir Dasgupta dasgupta_k2001@yahoo.co.in 1 Department of Mining Machinery Engineering, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, India 2 Department of Mechanical Engineering, Indian Institute of Technology (Indian School of Mines), Dhanbad 826004, India I Single-port energy storage inertial element in bond graph model J ld Load inertia K cl Bulk stiffness of the fluid at the clutch cylinder K m Bulk stiffness of the fluid at the motor plenum K p Bulk stiffness of the fluid at the pump plenum K spl Spring stiffness of the solenoid valve spindle K splh A high value of the spring stiffness of the solenoid spindle M spl Mass of the solenoid valve spindle P acml The constant pressure from the accumulator P p The pump pressure P ps The pump pressure corresponding to single- motor drive mode P md Pump pressure of two-motor drive system P ms Motor pressure of single-motor drive system P md Motor pressure of two-motor drive system P mp Motor pressure working as pump P smp Sump pressure p l Load momentum R Single-port resistive element R cv Clutch valve port resistance 123