Abstract
This paper deals with non-linear modelling and control of a differential hydraulic actuator. The nonlinear state space equations are derived from basic physical laws. They are more powerful than the transfer function in the case of linear models, and they allow the application of an object oriented approach in simulation programs. The effects of all friction forces (static, Coulomb and viscous) have been modelled, and many phenomena that are usually neglected are taken into account, e.g., the static term of friction, the leakage between the two chambers and external space. Proportional Differential (PD) and Fuzzy Logic Controllers (FLC) have been applied in order to make a comparison by means of simulation. Simulation is performed using Matlab/Simulink, and some of the results are compared graphically. FLC is tuned in a such way that it produces a constant control signal close to its maximum (or minimum), where possible. In the case of PD control the occurrence of peaks cannot be avoided. These peaks produce a very high velocity that oversteps the allowed values.
Highlights
Hydraulic actuators are used for delivering high actuation forces and high power density
From the control engineering point of view, synchronizing or symmetric actuators are preferred because there is no piston area difference and this fact reduces non-linearities, but on the other hand, the construction of these types of actuators is difficult and expensive
Fuzzy controllers have the disadvantage that it is difficult to tune the large number of parameters, in contrast to the proportional derivative (PD) controller, which can be expressed by the equation: uPD = KP e + KD e&
Summary
Hydraulic actuators are used for delivering high actuation forces and high power density. The schematic diagram of a differential actuator, as shown, consists of a constant pressure supply pump, a magnetically controlled spool valve and a differential hydraulic cylinder. Spool valve dynamics can be derived in a similar way as for a cylinder, but the following linear second order differential equation is a widely used and sufficient approximation: d2 xs(t) w2n u( t)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call