Networked Control Systems with Intermittent Acknowledgement

网络化控制系统（NCS）利用通信信道或网络在不同组件之间传输信号。网络控制系统中的一个关键问题是数据传输不再是无损的，数据包可能会由于各种原因而丢失。两个众所周知的传输协议，传输控制协议（TCP）和用户数据报协议（UDP），通常用于处理这个问题。部署了TCP和UDP的NCS分别称为TCP类和UDP类NCS。类TCP网络控制系统通过从目的地向源发送接收确认（ACK）来实现可靠的数据传输，但需要额外的资源来建立和维护源和目的地之间的连接。此外，握手、重传和其他机制可能导致反馈环路中的显著延迟。相比之下，UDP类NCS以较低的数据传输可靠性为代价，减少了资源消耗并导致较低的延迟。然而，由于数据丢失而导致的性能恶化对于某些控制任务来说可能是不可接受的。 尽管类TCP和类UDP的NCS取得了显著进展，但新兴的控制相关应用，如无线过程自动化、自动驾驶和网络化工厂，也带来了新的挑战。一方面，高数据可靠性和控制性能是期望的，因为许多分组与安全关键消息相关，其丢失和所导致的性能劣化可能对人或设备有害。另一方面，低延迟对于满足控制任务的严格及时性和敏捷性要求至关重要。此外，由于许多设备由电池供电并且具有用于计算、控制和通信的有限资源，因此期望减少资源消耗。无论是类似于TCP的国家统计系统，还是类似于UDP的国家统计系统，都无法解决所有这些问题，这就需要新的办法和工具。为此，一种新型的网络控制系统与间歇性ACK（iACK-NCSs），以及相关的控制分析和设计框架，包括建模，估计，控制，和分布式部署是在这个研究计划。 iACK-NCS的新奇在于，一对源和目的地根据控制目标、工厂动态和网络条件自适应地生成ACK信号。通过主动和自适应ACK的故意集成，它具有以最少的资源使用实现快速响应、低延迟和高性能估计/控制的潜力。该研究项目的成功完成不仅将加深对网络和分布式系统背景下的控制和通信理论的理解，而且还将提供可应用于实际网络控制问题的新算法和协议。此外，它将导致研究生在一个重要和快速增长的领域的培训，使他们能够开发新的方法和技能，这很可能影响学术和工业部门。

Networked control systems (NCSs) utilize communication channels or networks to transmit signals among different components. A crucial issue in NCSs is that data transmission is no longer lossless, and data packets may be dropped due to various reasons. Two well-known transport protocols, Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), are usually used to treat this issue. NCSs with TCP and UDP deployed are called TCP-like and UDP-like NCSs, respectively. TCP-like NCSs feature the reliable data transmission by sending an acknowledgement (ACK) of receipt from destination to source but require extra resources to establish and maintain a connection between source and destination. Also, handshake, retransmission, and other mechanisms may cause a significant delay in the feedback loop. By contrast, UDP-like NCSs, at the cost of lower data delivery reliability, reduce resource consumption and cause lower latency. However, the performance deterioration resulting from data loss may be unacceptable for some control tasks. Despite the remarkable progress in TCP-like and UDP-like NCSs, emerging control-related applications such as wireless process automation, autonomous driving, and networked factory have posed new challenges. On the one hand, high data reliability and control performance are desired as many packets are related to the safety-critical message, whose loss and resulting performance deterioration can be harmful to people or equipment. On the other hand, low latency is essential to fulfiling stringent timeliness and agility requirements of control tasks. Besides, reduced resource consumption is desired as many devices are powered by batteries and have limited resources for computation, control, and communication. Neither TCP-like NCSs nor UDP-like NCSs is able to address all these issues, and this calls for new approaches and tools. To this end, a new type of NCSs with intermittent ACK (iACK-NCSs), and related control analysis and design framework covering modelling, estimation, control, and distributed deployment are to be developed in this research program. The novelty of iACK-NCSs is that a pair of source and destination generates ACK signals adaptively according to control targets, plant dynamics, and network conditions. Through deliberate integration of active and adaptive ACK, it has the potential to achieve fast responses, low latency, and high-performance estimation/control with minimum use of resources. The successful completion of the research program will not only deepen understanding of theory on control and communication in the context of networked and distributed systems but also provide novel algorithms and protocols which can be applied to practical networked control problems. Also, it will lead to the training of research students in a significant and rapidly growing area, enabling them to develop new approaches and skills which are very likely to impact both academic and industrial sectors.