Hydraulic variable-speed transmissions as servomotors

The hydraulic transmission is an important form of servomotor about which little has been written from the viewpoint of the servomechanisms specialist. This paper presents an analysis of the hydraulic transmission; and, for three transmissions, a comparison between the predicted behavior based on the analysis and the measured behavior observed by frequency response tests. Discrepancies between predicted and measured performance are discussed and conclusions drawn. Suggestions are made for improvement of transmission performance. Data necessary for calculations on the transmissions tested are given in the appendix.