Hydraulic Noise : Modelling Pump/Motor Torque Ripple

[OwenDavid]

The torque output of a radial piston motor can be derived in several ways.

• as a function of motor geometry and oil pressure
• as a summation of the contribution from each piston during one shaft revolution.

The difference can be readily seen in the image from Italian manufacturer SAI.

I would like to model the flow/ripple from axial and radial piston machines and wonder if anyone has further information?

Currently I have a python algorithm that approximates motor torque ripple as a summation of sine waves, being one for each piston. However, from the datasheet there appears to be a dip in the torque five times per rotation. I would like to approximate this if anyone has any relevant information on what it represents.