Electro-pneumatic position tracking control system based on an intelligent phase-change PWM strategy

Abstract

This paper presents an intelligent phase-change PWM strategy for a position tracking system which includes four solenoid on-off valves and a double-acting double-rod-end cylinder. The proposed technique is designed to minimize the tracking errors and improve the position tracking performance. For an electro-pneumatic system with four valves, only seven switching modes are considered valid. We initially set two switching modes in a pulse width modulation (PWM) period, and this method can also be regarded as a PWM method with changeable phases. In the complete strategy, the operating mode of the system will be selected according to the pressure state and the sliding function. All the switching modes are applied properly in the strategy. A sliding mode controller is designed to utilize the phase-change PWM strategy, and stability of the system is proved. The performance of the proposed strategy is experimentally verified on a field programmable gate array platform. All simulations and experiments verify the effectiveness of the proposed scheme.

A new compressible flow model for pneumatic directional control valves

“…Therefore, ½k(P s ) f and ½k(P s ) e empirical coefficients have been developed to compensate the effect of the supply pressure (P s ) to produced theoretical mass flow rate ( _ m m ). The coefficients are shown in equations (10) and (11). As it is clear, ½k(P s ) f and ½k(P s ) e are the third-and fourth-order polynomial functions, respectively, which have R 2 = 1 fit quality…”

“…The CPR (a) value calculated from the 2D lookup table, and the model parameters (a 1 , a 2 , and e) determined separately from the 1D lookup table are fed to the ''New flow model'' block. In addition to these parameters, the k(P s ) is fed into the ''New flow model'' block using either equation (10) or equation (11) based on the experiment mode. The upstream and downstream pressure values (P u , P d ) assigned according to the experimental mode are also fed to the ''New flow model'' block instantly, and as a result, the theoretical mass flow rate ( _ m p ) is calculated using equations ( 7) and (8).…”

“…Solenoid valves are inexpensive, and their control flexibility is limited, but their performance has been attempted to be enhanced by the use of 1 various approaches such as pulse width modulation (PWM) and sliding mode control (SMC). [10][11][12] The aforementioned drawbacks make the solenoid valves unsuitable for high precision control applications. On the contrary, in proportional DCVs, the orifice opening can be adjusted precisely at the desired levels by adjusting spool position of the valve according to the manipulated control signal.…”

A Real-Time Realization Method for the Pneumatic Positioning System of the Industrial Automated Production Line Using Low-Cost On–Off Valves

“…The third aspect is the real-time implementation in both software design and hardware setup. In past articles, there are many ways to realize real-time control in the programmable logic controller (PLC) [20] or the field programmable gate array (FPGA) [21,22] controller. The shortcomings of these articles are that there is no description of the overall program design method and other details, including the cycle time, so it is difficult to promote and apply in the industrial field.…”

An Electro-Pneumatic Force Tracking System using Fuzzy Logic Based Volume Flow Control

“…However, for the PWM method and the high-speed on-off valve, the dead zone problem has always existed, which severely restricts the development of the high-speed on-off valve [11,12]. Many improved methods such as modified differential PWM (MD-PWM) [13], the five and seven modes switching method [14], and phase-change PWM [15] are proposed to deal with the dead zone problem. These methods do have a particular effect on the dead zone compensation, but they are not perfect.…”