| In past decades, a parallel-bus based point-to-point architecture between a controller and actuators or sensors was dominant and capable of achieving satisfactory performance. However, as the complexity of control systems increases, an enhanced communication method, between the massive number of sensors and actuators, is required to maintain and improve the performance of control systems. Recently, a networked control system (NCS) has been introduced as a substitute for conventional control systems in widespread applications. In general, a NCS provides many advantages such as reconfigurability, expandability, modulability, decreased wiring and cost-effectiveness. Many distributed network systems of various topologies and network types have been developed, but they tend to suffer from issues such as non-determinism, long network delay and unfairness. These may cause instability and difficulty in control, because most of them adopted conventional network standards that may include redundant and inefficient processes in their protocols and mechanisms.; This dissertation presents two networked control systems, which are optimized for control systems that contain an enormous number of sensors and actuators. NCSs are designed and implemented to minimize unnecessary network-induced delays, considering all hardware processes. The systems achieve best performance in hardware-level network devices for control applications that require high closed-loop sampling rate above 1kHz, so that the performance of the NCS is almost equivalent to that of a digital control system without a network. They are ring-based network systems using high-speed communicating transceivers called CY7C924ADX and CY15G family from Cypress semiconductor. Efficient network protocols and strategies are developed to achieve fast transfer of information and allowable network latency. As an overview of the network characteristics, the networks has ring-based master/slaves architecture, optimized message format, one-shot distribution and collection of data, multi-node transmission and reception, echoing of messages, no arbitration mechanism and a debugging network channel. The network guarantees determinism, collision-free transmission, relatively small overhead, fairness between nodes and flexibility in configuration.; The two presented NCSs provide a network solution for hard real-time control applications, offering much less network latency than any existing NCS. Specifically these NCSs minimize the latency caused by serial-link media between a central controller and sensors/actuators in any configuration of network devices. NCSs with reduced latency will provide a huge benefit for controller design and for system stability and will promise the best performance using network systems. |
