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The article presents three experimental systems made for the purpose of conducting research in the field of proportional and servo hydraulics, as well as the purpose of training students. The first system is a module for controlling linear motion of hydraulic actuator. The control system consists of a main cylinder which is controlled by using a proportional directional control valve that can supply the cylinder with hydraulic fluid. Disturbance is generated by using a pressure control valve and a load cylinder, which produces a reaction force. Two cylinder rods are coupled by a steel joint. The second system is a module for the control of force, i.e. a hydraulic press where it is possible to regulate the force of compressing. To hold pressure in the cylinder’ s chamber and thereby the cylinder’ s force to the desired value, a pressure type servo valve is used. The third system is a module for controlling rotational motion of hydraulic actuator. In this system a hydraulic motor as a control object is used, where the disturbance is generated by using a hydraulic pump whose output pressure is adjusted using the proportional pressure valve. Motor and pump rods are tightly connected. The hydraulic motor speed can be controlled both by using a servo valve (throttling principle) and by controlling the speed of the induction motor and supply pump by means of the frequency converter and control computer with digital electronic card (volumetric control principle). All three systems also include measurement and control equipment for the realization of control algorithm. The experimental verifications are made using these three experimental systems – the module for linear motion control, the module for control of force and the module for rotational motion control that have been made at our Laboratory. The experimental results for controlling the position of hydraulic cylinder, for controlling the force of hydraulic press, as well as for controlling the speed rotation of hydraulic motor are displayed. The control algorithms and monitoring process are implemented on a real-time hardware board that is programmed in Matlab/Simulink environment using Real-Time Workshop program. |
