Background and Objective: New proposals to improve the regulation of hypnosis in anaesthesia based on the development of advanced control structures emerge continuously. However, a fair study to analyse the real benefits of these structures compared to simpler clinically validated PID-based solutions has not been presented so far. The main objective of this work is to analyse the performance limitations associated with using a filtered PID controller, as compared to a high-order controller, represented through a Youla parameter.

Methods: The comparison consists of a two-steps methodology. First, two robust optimal filtered PID controllers, considering the effect of the inter-patient variability, are synthesised. A set of 47 validated paediatric pharmacological models, identified from clinical data, is used to this end. This model set provides representative inter-patient variability Second, individualised filtered PID and Youla controllers are synthesised for each model in the set. For fairness of comparison, the same performance objective is optimised for all designs, and the same robustness constraints are considered. Controller synthesis is performed utilising convex optimisation and gradient-based methods relying on algebraic differentiation. The worst-case performance over the patient model set is used for the comparison.

Results: Two robust filtered PID controllers for the entire model set, as well as individual-specific PID and Youla controllers, were optimised. All considered designs resulted in similar frequency response characteristics. The performance improvement associated with the Youla controllers was not significant compared to the individually tuned filtered PID controllers. The difference in performance between controllers synthesized for the model set and for individual models was significantly larger than the performance difference between the individual-specific PID and Youla controllers. The different controllers were evaluated in simulation. Although all of them showed clinically acceptable results, the robust solutions provided slower responses.

Conclusion: Taking the same clinical and technical considerations into account for the optimisation of the different controllers, the design of individual-specific solutions resulted in only marginal differences in performance when comparing an optimal Youla parameter and its optimal filtered PID counterpart. The inter-patient variability is much more detrimental to performance than the limitations imposed by the simple structure of the filtered PID controller.

背景与目的：基于先进控制结构的发展，不断提出改进麻醉中催眠调节的新方案。但是，到目前为止，还没有进行过公平的研究来分析这些结构与较简单的经过临床验证的基于PID的解决方案相比的真正好处。这项工作的主要目的是分析与通过Youla参数表示的高阶控制器相比，使用过滤后的PID控制器的性能限制。

方法：比较包括两步法。首先，考虑患者之间差异的影响，综合了两个鲁棒的最优滤波PID控制器。为此，从临床数据中鉴定出了一组47种经过验证的儿科药理模型。该模型集提供了代表性的患者间差异性。第二，针对该集合中的每个模型合成了单独的经过过滤的PID和Youla控制器。为了比较的公平性，针对所有设计优化了相同的性能目标，并考虑了相同的鲁棒性约束。控制器综合是利用凸优化和依赖于代数微分的基于梯度的方法来执行的。比较患者模型集的最坏情况性能。

结果：优化了两个用于整个模型集的鲁棒滤波PID控制器，以及针对特定个体的PID和Youla控制器。所有经过考虑的设计均产生相似的频率响应特性。与单独调整的滤波PID控制器相比，与Youla控制器相关的性能提升并不明显。为模型集和单个模型合成的控制器之间的性能差异明显大于单个特定PID和Youla控制器之间的性能差异。在仿真中评估了不同的控制器。尽管所有这些均显示出临床可接受的结果，但可靠的解决方案提供了较慢的响应。

结论：考虑到相同的临床和技术考虑因素，以优化不同的控制器，当比较最佳的Youla参数和最佳的已过滤PID对应项时，针对特定个体的解决方案的设计仅导致性能的边际差异。与过滤后的PID控制器的简单结构所施加的限制相比，患者之间的可变性对性能的危害更大。