With the exception of the function calls, matrix reformatting, and global variable storage, the code used in the control of the Simulink model was the same as that used for controlling the actual water hydraulic test rig.
The fuzzy rule set generated by the modelling process was used for the control of the actual water hydraulic system and Figure 10 and 11 show the response following a 20｡?o 200｡?tep position demand and the resulting squared error.
It is evident that up to 35 seconds the FLC is successful at controlling the water hydraulic system. The control systems response to the stepped demand is more sluggish than that of the simulated plant due to a lower operating pressure being used for the physical system. The response of the FLC achieves a near first order tracking response. This test also shows the effect of one of the poppet valves failing due to overheating. At 35 seconds the negative stroke (exhaust) poppet valve became redundant due to overheating of the solenoid coil. The response of the FLC was similar to the simulated response of the system with a high degree of leakage, and produced an initial loss in tracking followed by a rapid recovery as the controller attempts to minimise the position error.
8. CONCLUSIONS
The main criterion for the design of the water hydraulic actuation system was simplicity in form and operation. A flexible system was developed, using relatively simple hydraulic components, in conjunction with an intelligent control system.
A non-linear model of the hydraulic system was constructed and used to simulate the dynamic response of the physical system. The model was successfully used to train the SOFLC and to carry out simulation studies to examine the effects of system degradation through leakage and fouling.
The developed control strategy successfully co-ordinated the operation of the four poppet valves used to supply hydraulic fluid to the actuator system. The self-learning algorithms successfully modified the reduced fuzzy rule set to cope with the introduction of leakage across the actuator and control valves within the hydraulic circuit.
Communication protocol problems between the MATLAB and LabVIEW processing environments prevented the self-organizing aspects of the control software from being tested with the physical system.
The FLC system was implemented on the water hydraulic actuation system test rig and provided valuable validation data for the simulation model. It also demonstrated good performance of the FLC and the possibility to enhance this by the future implementation of the SOFLC system.
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