The sliding mode control (SMC) technique with a first-order low-pass filter (LPF) is incorporated with a new adaptive PID controller. It is proposed for tracking control of an uncertain nonlinear system. In the proposed control scheme, the adaptation law is able to update the PID controller online during the control process within a short period. The chattering phenomenon of the SMC can be alleviated by incorporation of a first-order LPF, while the robustness of the control system is similar to that of the sliding mode. In the closed-loop control analysis, the convergence condition in the reaching phase and the existence condition of the sliding mode were analyzed. The stability of the closed-loop control is guaranteed in the sense of Lyapunov’s direct method. The simulations and experimental applications of a speed tracking control of a spark ignition (SI) engine via electronic throttle valve control architecture are provided to verify the effectiveness and the feasibility of the proposed control scheme.
Problem statement:In this study, a combination of a classical Sliding Mode Control (SMC) and a PID tuning technique with low-pass filter is developed for a position tracking control of a DC servo motor. Approach: The DC servo motor will be used to adjust the throttle angle of the gasoline engine in our laboratory. To control the engine speed to be accurate, the servo motor position has to be controlled precisely. Results: Uncertainty and nonlinearity of the servo motor system can be surmounted by the sliding mode control while the system response can be fine adjusted via the PID gain tuning. A low-pass filter has been incorporated also in order to eliminate and limit amplification of noise due to differentiation in the PID algorithm. The stability of the control system is guaranteed by the Lyapunov stability theorem. The experimental results shown that, the proposed technique has good tracking performance compares to a PIDSMC and a conventional PID technique even without actuator model. Conclusion/Recommendations: However, the performance strongly depends on the specified control gain in PID portion and sliding function. Therefore, any self tuning control gain techniques should be developed further.
Food processing, including drying and cooking, generally influences the physical and chemical qualities of food products. The present study assessed the changes in oxalate contents of two rice paddy herbs (phak-kha-yaeng in Thai), Limnophila aromatica (phak-kha-yaeng khao) and Limnophila geoffrayi (phak-kha-yaeng daeng), as affected by different drying methods, namely hot-air, freeze and vacuum drying. The entire, soluble and insoluble oxalate contents of the cooked samples were also evaluated. Dried samples showed a significant increase in soluble oxalate content compared to fresh samples except for hot-air dried phak-kha-yaeng daeng, while entire and insoluble oxalate contents in dried samples were significantly decreased. Levels of soluble oxalates which were 30% in fresh phak-kha-yaeng khao and 46% in fresh phak-kha-yaeng daeng can be significantly reduced after cooking by boiling. In addition, the cooking of both the hot-air dried phak-kha-yaeng samples also showed greater losses in oxalates than those of other samples studied. Hot-air drying should be considered as a suitable drying method for phak-kha-yaeng with respect to reducing its oxalates. The present study has provided useful information for the drying of vegetables or plant foods to reduce the risk of consuming plant foods which contain high levels of oxalates.
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