Experimental Study on Positioning Accuracy of an Automated Long-Stroke Rodless Pneumatic Actuator

Introduction. In modern industrial processes, pneumatic actuators with long-stroke movements play an important role. However, their use is limited by low accuracy resulting from the difficulties of controlling air flows. These limitations are caused by the compressibility of air and thermodynamic processes, which makes it urgent to improve the accuracy of such systems. The conducted analysis of scientific literature shows that modern research is mainly focused on the use of systems with standard cylinders with a working stroke limited to three meters. At the same time, the issues of development and research of long-stroke systems of rodless pneumatic drives, capable of having a stroke length of up to six meters, remain insufficiently studied. The introduction of advanced control systems in this type of drives involves significant investments in a high-tech electronic base and additional structural elements. In this regard, the development of fundamentally new technical solutions that allow for the efficient operation of mechanisms with a working stroke of more than three meters while maintaining the required technical parameters and economic efficiency, is of particular relevance. In the framework of previous studies, the author proposed a design of a pneumatic drive for long-stroke movements, equipped with a unique control system based on a jet sensor and an external brake mechanism. Its mathematical modeling and theoretical analysis were also performed, which made it possible to identify key factors affecting the accuracy of positioning. To validate the mathematical model and the hypotheses put forward, the objective of this research is to experimentally verify the results of mathematical modeling of a positioning long-stroke rodless pneumatic actuator, as well as to confirm the degree of influence of key factors on positioning accuracy. Materials and Methods. The work involved a stand that was a technical model of a pneumatic drive with an original control system, including a jet sensor and an external brake device. To verify the operability and accuracy of the jet sensor readings, the spillage method was applied using the Camozzi MF4008-10-R-BV-A flow sensor after the element under study, and Camozzi SWCN-P10-P3-2 pressure sensors placed before and after the considered element. The tests conducted on the developed jet sensor showed high reliability and stability of operation in various operating modes. The experimental study of a long-stroke rodless pneumatic actuator included evaluation of the actuator's technical capabilities, analysis of positional cycles, study on the effect of external factors, and comparison of the results of computational and full-scale experiments. The results of computational and full-scale experiments were processed using the Mathcad and MATLAB software packages. The dependences of positioning accuracy on mass and stroke length were constructed. Results. The reliability of the model was established at the level of the maximum discrepancy between the experimental data and the results of mathematical modeling, which amounted to 18%. That confirmed the adequacy of the developed model for engineering calculations. The effect of the load mass on the accuracy of positioning was experimentally established. With an increase in mass from 10 to 30 kg, the accuracy decreased by 1.47 times, and with a mass of 60 kg, the accuracy deteriorated by another 1.37 times relative to the base mass of 10 kg. In addition, the effect of stop coordinates was studied: the dependence of positioning accuracy on the position of the actuator was established. When moving from 0.1 m to 0.22 m, the accuracy deteriorated by 3.2 times, but with further movement to 0.35 m, it improved by 2.2 times. Discussion. The conducted experimental studies allowed achieving good results in the development of long-stroke pneumatic drives. Successful verification of the mathematical model confirmed the correctness of both the model itself and the theoretical studies conducted in the author's previous works. The positioning accuracy of the drive of 77 microns at a distance of over three meters was reached. This indicator significantly exceeds the results presented in the studies of other authors, which shows the high potential of the developed design. The economic efficiency of the proposed solution is due to the absence of an electronic component base in the control system. This not only reduces initial production costs, but also significantly simplifies maintenance of the drive under operation. The comparative analysis with existing developments confirms the superiority of the proposed system in terms of cost criteria.