Abstract
In this paper, a fuzzy logic based volume flow control method is proposed to precisely control the force of a pneumatic actuator in an electro-pneumatic system including four on-off valves. The volume flow feature, which is the relationship between the duty cycle of the pulse width modulation (PWM) period, pressure difference, and volume flow of an on-off valve, is based on the experimental data measured by a high-precision volume flow meter. Through experimental data analysis, the maximum and minimum duty cycles are acquired. A new volume flow control method is introduced for the pneumatic system. In this method, the raw measured data are innovatively processed by a segmented, polynomial fitting method, and a newly designed procedure for calculating the duty cycle is adopted. This procedure makes it possible to combine the original data with fuzzy logic control (FLC). Additionally, the method allows us to accurately control the minimum and maximum opening pulse width of the valve. Several experiments are performed based on the experimental data, instead of the traditional theoretical models. Only 0.141 N (1.41%) overshoot and 0.03 N (0.03%) steady-state error are observed in the step response experiment, and 0.123 N average error is found while tracking the sine wave reference.
Highlights
In modern society, especially in industry, pneumatic control systems which use compressed gas to transfer and control energy have been widely used to drive automated machinery such as the metro door switch, production line operations, robotic arms, and in the aerospace industry
Testing Results with a reconfigurable field programmable gate array (FPGA) module is connected to an Intel Core i5 laptop by Ethernet communication
We convert the unit of these results to percentage for a better analysis and use in the following control algorithms
Summary
Especially in industry, pneumatic control systems which use compressed gas to transfer and control energy have been widely used to drive automated machinery such as the metro door switch, production line operations, robotic arms, and in the aerospace industry. Compared to hydraulic control systems, it has a number of irreplaceable advantages: high efficiency, durability and reliability, simple structure, clean energy, easy maintenance, and low price. Pneumatic control valves have developed rapidly over the past twenty years. Proportional or servo valves are mentioned mostly for their continuous and linear output characteristics [1,2]. The defects of this kind of valve are distinct: a slow response speed, high expense, and difficult maintenance. An alternative is solenoid on-off valves, due to their low price and easy maintenance
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