Wireless Networked Control Systems Based On Modified Internal Model Control

Wireless network control system (WiNCS) is a closed-loop feedback control system which adds a wireless network as a medium of transmission signals. WiNCS would generate induced delay which affects control effect even cause system instability due to the introduction of wireless networks. Internal model control scheme requires low model accuracy and indicates good results in model mismatch circumstances, and robust design make it easy to adjust parameters on-line.Conventional internal model control only applies to open-loop stable plant, but not open-loop unstable plant, non-minimum phase system which contains zeros in right half plane will output negative tone, thus affects the control performance. Based on TRUETIME1.5simulation platform, this paper studies the modified internal model control strategy for unstable delaying plant, so that the output can remain stable in the case of large delay, and can achieve fast track when disturbed, as a result, enhanced robustness of the system.Firstly, this paper makes a design and simulation to internal models respectively with one-degree-of-freedom IMC and two-degree-of-freedom IMC in WiNCS for open-loop stable plants.Results demonstrate the advantages of internal model control is that not require to estimate and forecast network delay and does not need to consider the clock, signal synchronization between nodes. One-degree-of-freedom EMC and two-degree of freedom IMC both have better dynamic output performance, however, the two-degree of freedom IMC can control the tracking performance and robust performance separately, as a result, further enhanced the anti-jamming capability.Secondly, this paper proposed an modified internal model for WiNCS with open-loop Unstable plants. Firstly, we add a stabilizer in the plant, and tuning the instable plant, and then follow the generalized stabile plant to make a design of internal model control. When the model are matched,we make simulations separately for three typical cases such as the presence of pole in right half plane, pole in origin, and second-order unstable plants. Simulation results show that the improved internal model control method is effective in the use of control for unstable delaying plants, thus, ensured the stability of the system. Further, we make a simulation and study with the model mismatch and change in network environment comparative study shows that in a large delay, packet loss and other harsh conditions, modified internal model control strategy can meet system stability and robustness requirements. Finally, this paper proposed an improved internal model for WiNCS with non-minimum phase system has zeros in right half plane. An modified internal model WiNCS, which adds a mirror pole in the left half-plane, reducing the system’s initial negative tone, and gives a detailed controller design method. Then the improvement program was simulated, the simulation shows, modified internal model control strategy can effectively suppress the negative tone system. Finally, the truth that the system performance relates to the output filter parameter selection was validated. By adjusting the filter time constant can get the desired output characteristics of the system.