Multi-function controllers for a hydraulic pump

  • Peter Tovey

Student thesis: Doctoral ThesisDoctor of Philosophy


This project has been undertaken for Hamworthy Hydraulics Limited. Its objective was to design and develop a controller package for a variable
displacement, hydraulic pump for use mainly on mobile earth moving
machinery. A survey was undertaken of control options used in practice and
from this a design specification was formulated, the successful implementation
of which would give Hamworthy an advantage over its competitors.
Two different modes for the controller were envisaged. One consisted
of using conventional hydro-mechanics and the other was based upon a microprocessor.
To meet short term customer prototype requirements the first section
of work was the realisation of the hydro-mechanical system. Mathematical
models were made to evaluate controller stability and hence aid their design.
The final package met the requirements of the specification and a single version
could operate all sizes of variable displacement pumps in the Hamworthy range.
The choice of controller options and combinations totalled twenty-four.
The hydro-mechanical controller was complex and it was realised that a
micro-processor system would allow all options to be implemented with just one
design of hardware, thus greatly simplifying production. The final section of this project was to determine whether such a design was feasible. This entailed finding cheap, reliable transducers, using mathematical models to predict electro-hydraulic interface stability, testing such interfaces and finally incorporating a micro-processor in an interactive control loop.
The study revealed that such a system was technically possible but it would cost 60% more than its hydro-mechanical counterpart. It was therefore concluded that, in the short term, for the markets considered, the hydro-mechanical
design was the better solution.
Regarding the micro-processor system the final conclusion was that, because the relative costs of the two systems are decreasing, the electro-hydraulic controller will gradually become more attractive and therefore Hamworthy should continue with its development.
Date of AwardSept 1980
Original languageEnglish
SupervisorK. Foster (Supervisor), B.M. Bell (Supervisor), B. Wynn (Supervisor), D.C. Hickson (Supervisor) & F.G. Willets (Supervisor)


  • controllers
  • control
  • pumps
  • servo-mechanisms

Cite this