Editorial

摘要:

Prof. Jingqing Han left us ten years ago but his ideas not only lived on but also grew evermore powerful, as evident in this special issue at Control Theory and Technology, in English, and in the special issue at Control Theory and Applications, in Chinese. A man of few words, Han was not a person easily understood, even for those close to him. It sometimes took us years to unpack a single idea of his and unearth a brilliant insight. For the benefits of a broader audience, however, let’s start with the two basic questions that drove his research: 1) Is the problem of control a problem of stability and optimization, as commonly framed in applied mathematics? 2) If control design cannot be premised on detailed and accurate mathematical model, as declared by H. S. Tsien (Qian Xuesen) in the groundbreaking book, Engineering Cybernetics, in 1954, then what should or could it be premised on? Han’s answer to the first question was a resounding No and its consequence is profound, for it goes against the reigning paradigm and it implies that the right kind of control theory has yet to come. In conceiving ADRC (active disturbance rejection control), his sole purpose was to show us an alternative to the reigning paradigm. In essence, Han solved a problem of control, the existence of which escaped the attention of most scholars in his time. “He was ahead of his time”, said Prof. Lei Guo, a colleague of his for many years. The second question is no less disrupting and mystifying: disrupting because its answer has changed the way control is practiced, as evident in the “application” papers in this issue; mystifying because of the absence of fully articulated principles and the theoretical foundation. In fact, these two questions arose from the same puzzle left by Han: if there is an alternative to modern control theory, what does it entail?...

Abstract:

Prof. Jingqing Han left us ten years ago but his ideas not only lived on but also grew evermore powerful, as evident in this special issue at Control Theory and Technology, in English, and in the special issue at Control Theory and Applications, in Chinese. A man of few words, Han was not a person easily understood, even for those close to him. It sometimes took us years to unpack a single idea of his and unearth a brilliant insight. For the benefits of a broader audience, however, let’s start with the two basic questions that drove his research: 1) Is the problem of control a problem of stability and optimization, as commonly framed in applied mathematics? 2) If control design cannot be premised on detailed and accurate mathematical model, as declared by H. S. Tsien (Qian Xuesen) in the groundbreaking book, Engineering Cybernetics, in 1954, then what should or could it be premised on? Han’s answer to the first question was a resounding No and its consequence is profound, for it goes against the reigning paradigm and it implies that the right kind of control theory has yet to come. In conceiving ADRC (active disturbance rejection control), his sole purpose was to show us an alternative to the reigning paradigm. In essence, Han solved a problem of control, the existence of which escaped the attention of most scholars in his time. “He was ahead of his time”, said Prof. Lei Guo, a colleague of his for many years. The second question is no less disrupting and mystifying: disrupting because its answer has changed the way control is practiced, as evident in the “application” papers in this issue; mystifying because of the absence of fully articulated principles and the theoretical foundation. In fact, these two questions arose from the same puzzle left by Han: if there is an alternative to modern control theory, what does it entail?...