The Benefits of Soft Sensor and Multi-Rate Control for the Implementation of Wireless Networked Control Systems

Abstract

Recent advances in wireless networking technology and the proliferation of industrial wireless sensors have led to an increasing interest in using wireless networks for closed loop control. The main advantages of Wireless Networked Control Systems (WNCSs) are the reconfigurability, easy commissioning and the possibility of installation in places where cabling is impossible. Despite these advantages, there are two main problems which must be considered for practical implementations of WNCSs. One problem is the sampling period constraint of industrial wireless sensors. This problem is related to the energy cost of the wireless transmission, since the power supply is limited, which precludes the use of these sensors in several closed-loop controls. The other technological concern in WNCS is the energy efficiency of the devices. As the sensors are powered by batteries, the lowest possible consumption is required to extend battery lifetime. As a result, there is a compromise between the sensor sampling period, the sensor battery lifetime and the required control performance for the WNCS. This paper develops a model-based soft sensor to overcome these problems and enable practical implementations of WNCSs. The goal of the soft sensor is generating virtual data allowing an actuation on the process faster than the maximum sampling period available for the wireless sensor. Experimental results have shown the soft sensor is a solution to the sampling period constraint problem of wireless sensors in control applications, enabling the application of industrial wireless sensors in WNCSs. Additionally, our results demonstrated the soft sensor potential for implementing energy efficient WNCS through the battery saving of industrial wireless sensors.

Implementation and Evaluation of Wireless Networked Control Systems using Modbus

“…Nos experimentos anteriores, o controlador do WNCS estava operando com um período de amostragem do sensor sem fio (intervalo entre transmissões de mensagem da variável controlada) de 2 s. Em WNCS, o período de amostragem do sensor pode influenciar o desempenho de controle do sistema, além de ser um parâmetro diretamente relacionado ao consumo energético do sensor sem fio [14]. Do ponto de vista energético, quanto maior o período de amostragem do sensor, sem prejuízo do desempenho de controle, melhor para o WNCS.…”

Decoupling Control and Soft Sensor Design for an Experimental Platform

“…The backup of measuring instrumentation is a typical application of soft sensors. Thus, soft sensor is a mechanism used to replace the temporary or permanent unavailability of a physical sensor in a plant, which can happen due to the real sensor failure or removal for maintenance [26,27].…”

Identification of Functional Bioprocess Model for Recombinant E. Coli Cultivation Process

“…A system like this would require compatible equipment that might restrict access due to financial concerns, because it is not compatible with the chosen system or may lack functionality. However, it is worth replacing sophisticated equipment with soft sensors that estimate the desired non-observable parameters from the measured data collected [1,2].…”