CYBERNETIC MODEL OF WUXING AND THE PRINCIPLES OF DISTURBANCE REJECTION

Holistic, self-contained, and independent developed over millenniums, traditional Chinese medicine (TCM) is the embodiment of a cosmic view, rooted in Yin-Yang and Wuxing, in the inner working of human bodies. The TCM traces its origin to the Yellow Emperor’s Canon of Medicine, which systematically builds the basic tenants of Chinese medicine in the language of Yin-Yang and Wuxing. Westerners may be familiar with the term Yin-Yang but not with the term Wuxing, whose standard translation is “five elements,” which is, unfortunately, a bit misleading. In Wuxing the Chinese try to describe the characteristics of changes in matters, rather than the matters themselves, using the oldest tool of the Chinese thinkers: analogy. In philosophy and in medicine, the Chinese are more interested in how things change, rather than the things in themselves. The Yin and Yang are two opposing forces behind all changes in nature and in human body. Likewise, in Wuxing, water, fire, wood, metal, and earth are used as analogies to symbolize the mutual relationships of promotion and restriction. Take, for example, water, in nature it nourishes the wood and restricts fire; in human body it mirrors kidney, promotes liver (wood), and restricts heart (fire). It is through such analogies Wuxing is systematically used to explain human physiology and pathology [1, 2]. Starting with the Yellow Emperor’s Canon of Medicine, Wuxing has become the cornerstone of the TCM that has evolved over the millenniums and is still the basis of the TCM, that is, widely practiced today in China and beyond.

There is little doubt in the effectiveness of some of the TCM practices even in the West, as the wide acceptance of acupuncture, for example, attests. It is also widely recognized, however, that due to the historical and cultural differences, the tenants of TCM are often considered rather abstract and vague and are prone to misinterpretations, in the context of Western science. The values of TCM and the desire to understand it in the language of Western science have occupied the minds of scholars of many generations, East and West.

Much work has been done to quantify the TCM using the methodologies of modern science, including those from anatomy, physiology, pathology, pharmacology, biochemistry, cell biology, and molecular biology. Much progress has been made that gives us new insight into the workings of human body, disease, and treatments, all based on the TCM. The limitations of such line of investigation, however, are also evident in dissecting the holistic TCM using the reductive approach of the modern science. Physiologically and pathologically, a living body is not just a collection of molecules, cells, tissues, and organs, governed, but it is a complex whole governed by the laws of interrelationships among them and between them and their environments Precisely such interrelationships are front and central in the conceptions of the TCM and have been largely beyond the grasp of quantitative studies of the Western science. The missing link, it seems, is the science of interrelationships, to which we now turn.

It is well known in cell biology that a cell, the basic building block of life, constantly communicates with its environment and other cells in what is called cell signaling, which describes the generation, transmission, and reception of biological signals as well as the sequence of actions they trigger. Such “signaling” is commonly seen in engineering systems and is the subject of study in separate engineering disciplines such as signal processing, control, and communication. Such commonalities behind the biological and engineering mechanisms did not escape the mind of the American mathematician Wiener, who in 1948 wrote the landmark book titled “Cybernetics: or Control and Communication in the Animal and the Machine” [3], followed by Tsien’s book of “Engineering Cybernetics” in 1954 based on which a whole new engineering science of mutual relationships was born [4].

Unlike other natural sciences of matter, energy, heat, and so forth, cybernetics, according to Tsien, is a general science of “the qualitative aspects of the interrelations among various components of a system and the synthetic behavior of the complete mechanism.” Sounds like Wuxing? For example, in Wuxing one is concerned with the balance of the whole system, natural or human; likewise, in cybernetics one is mesmerized by the quality called stability, which is found not in individual components of a system but in how they are connected, or related, to each other. This shared concern by Wuxing and cybernetics on the holistic behavior rather than the material parts of system gives rise to the hope that, perhaps, the ideas of the TCM can be exposited through the language of cybernetics, a basic tenant of this paper. Instead of the five elements, we use the phase the cybernetic model of Wuxing in this paper to emphasize the connection and commonality in Wuxing and cybernetics.

Engineering cybernetics (EC), like the TCM, is guided by the general principles but is also very pragmatic. It aims at, according to Tsien, “those parts of the broad science of cybernetics which have direct engineering applications in designing controlled or guided systems” [4]. After sixty years of furious developments, engineering cybernetics has become a well-established field of scientific study with rigorous mathematical foundation and a set of extremely effective tools to guide the engineering practice.

Similar to the concept of Wuxing and its embodiments in the practice of TCM, EC has as primary goal the establishment and retention of balance in a dynamic system in the presence of internal and external disturbances. A particular example is the principle of active disturbance rejection control (ADRC) and its various embodiments in different domains of engineering [5–7]. The concepts and tools like ADRC give researchers a much needed vocabulary and methodology to study the TCM, where the diseases are caused by internal and external disturbances and the treatments can be generally seen as various means of disturbance rejection.

The human body is both a wonder and a mystery. This paper takes a small step to clarify the complexity by explaining the principle of Wuxing, which is central to the TCM, in the language of EC and ADRC. Interestingly perhaps to the Western scholars, Wuxing gives a holistic view of the complex system of human body, particularly in how the vital systems interact with each other. By understanding such interrelationship, described in the language of EC, the ADRC framework is then borrowed to explain how the disturbance rejection is accomplished in the TCM. The congenial connection between the system concepts and tools of cybernetics and the Ying-Yang and Wuxing in the TCM gives us hope to quantify and standardize the teachings of the TCM on a rigorous scientific foundation. To this end, the paper is organized as follows: the disturbance rejection paradigm in engineering and its connection to the TCM are explored in Section 2; the cybernetic model of Wuxing and disturbance rejection in the context of TCM are discussed in Section 3, followed by a case study in Section 4, using the liver cancer treatment as an example.

This paper attempts to establish a framework for the study of the TCM where a new language of engineering cybernetics is introduced to delineate, with clarity, the principles and practice of the TCM. In engineering cybernetic we find a holistic view, a science of interrelations, with strong resemblance to what the Wuxing attempts to do: describing the inner workings of nature and human body alike as mutually connected components, that is, closed-loop dynamic systems. EC and the TCM also share a commitment and goal to attain and maintain a quality, that is, described as balance, equilibrium, or homeostasis; correspondingly there is a great similarity in how such quality is maintained, by what is called “disturbance rejection” in EC. The engineering invention of active disturbance rejection shares the common goal with the TCM in anticipating and rejecting the disturbances before the balance is disrupted. Combining the vocabulary of EC and the TCM we found the cybernetic model of Wuxing as the common language and a promising new path towards the quantitative study of the TCM. As an initial study and illustration, the pathogenesis and treatment of the liver cancer based on the TCM are explained using the language of the cybernetic model of Wuxing and the principles of disturbance rejection. The results from a six-year study seem to support this line of investigation and to provide a clear exposition of both the principles of the TCM and how they are practical with herbal medicine.

Human body is a complex, large, and open system that defies our complete grasp. It has always been a great challenge to organically combine the best offerings from the Western medicine and the Eastern medicine, largely due to the lack of common language. In EC we find the language of a holistic science for the West, that is, inherently congenial to the Eastern thinking in Yin-Yang and Wuxing. It is our hope that what started here could help future researchers to build the bridge from the general system qualities and behaviors to the properties of the system components from the qualitative to the quantitative and from the abstract concepts to the concrete practice.

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