Original article A novel method to design pressure compensator for variable displacement axial piston pump Nitesh Mondal, Rana Saha, Saikat Mookherjee and Dipankar Sanyal Abstract An innovative design procedure has been formulated by developing a mathematical model for the pressure compensator of an axial piston pump. The compensator provides energy saving by making the pump variable displacement type depending on the system load, thereby providing energy saving by better resource management. The procedure involves simple static design steps to ensure a balanced swiveling torque on the swash plate for specified cut-in and cut-off pressure limits. Adopting the basic pump model from the earlier works, the dynamic model of the pump has been updated by including the compensator dynamics. A design sensitivity analysis through dynamic simulation has been performed that corroborates the need of the design through torque balancing. Also, through dynamic simulation, tolerances of some critical dimensions have been identified. The pressure compensator model has been validated against experimental result obtained from a reference pump. Keywords Mechanistic principles, mathematical modeling, component design, sensitivity analysis, experimental verification Date received: 6 July 2017; accepted: 20 May 2018 Introduction A pressure-compensated variable-displacement axial- piston pump makes hydraulic system energy effi- cient. 1,2 Agricultural, forestry, construction, mining, automotive, aerospace, and transport equipment involve typical applications of these pumps. 2–5 A pump-controlled system 2 has greater energy- saving potential than a valve controlled system and uses either a variable displacement pump driven by constant speed motor or a fixed displacement pump driven by variable speed motor. Contrasting the nearly constant delivery flow rate irrespective of the pressure rise across a fixed displacement pump, the delivery flow is adjusted in a variable displacement pump. In response to pressure rise beyond a certain limit, a valve-controlled mechanical device within the pump reduces the displacement or stroking volume in each revolution of the pump shaft. The flow rate can alternatively be adjusted by controlling the rotational speed of the prime mover driving a variable speed fixed displacement pump. Such a pump is expected to have higher efficiency, 6 but at the cost of slower control response. Since fast control response is the prerequisite in most applications, the use of the vari- able displacement pump remains more prevalent. The flow control arrangement in a variable dis- placement pump is called the pressure compensator, in which a small fraction of the main flow is passed through a passive valve for adjusting the orientation of a component controlling the stroking volume of the pump. A swash plate is a component that is used to adjust the stroking volume in a rotating group setting involving a number of axial pistons housed in the bores of a barrel that in turn is splined to the pump shaft. Using the delivery pressure through a spool valve to a stroking or control cylinder and directly to a rate or bias cylinder, a control torque is produced to achieve a swiveling motion of the swash plate. Only beyond a set delivery pressure, the pre-compression setting of a spring in the spool valve allows the swiveling torque to develop. This is called the cut-in pressure. As the available torque becomes higher for higher delivery pressure above the cut-in limit, Proc IMechE Part E: J Process Mechanical Engineering 0(0) 1–21 ! IMechE 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0954408918783409 journals.sagepub.com/home/pie Department of Mechanical Engineering, Jadavpur University, Kolkata, India Corresponding author: Rana Saha, Department of Mechanical Engineering, Jadavpur University, Raja S.C. Mullick Road, Kolkata 700 032, West Bengal, India. Email: rana.saha@jadavpuruniversity.in