“There are not many concepts that are as basic as the concept of uncertainty… There are many approaches to uncertainty but what is not well understood is how are [they] related. An important approach to uncertainty is the theory of grey systems – a theory developed in China…” – Lotfi A. Zadeh, founder of Fuzzy Set Theory.
“…it can be expected that more scientific workers from different parts of the world will soon join hands and together make grey system and information a powerful theory capable of bringing forward practically beneficial impacts to the advancement of the human society… [Grey methods and techniques] show how from our knowledge based on partially and poorly known information can be obtained accurate descriptions and effective controls of the systems of interest.” – Hermann Haken (2007), founder of Synergetics and one of the fathers of the quantum-mechanical laser theory.
“The question that naturally arises is why grey systems are of such great import[ance] at this point in history. The answer is quite straightforward: many challenging problems facing society consist of interconnected complex systems of systems exhibiting high uncertainty and having few measurements.” – Keith W. Hipel (2010), President, Academy of Science, Royal Society of Canada.
“Grey system theory, is used to treat vagueness and ambiguity in the human decision-making process. Interval grey numbers can effectively model decision-maker judgments for social sustainability supplier evaluation and selection decision-making.” – Joseph Sarkis (2019), Professor of management, Worcester Polytechnic Institute.
“There is a great variety of approaches to grey data. [One of] the four most interesting and important approaches [is] Grey system theory, … a methodology which focused on the study of problems involving small samples and poor information, which is very often a common situation in decision- making, irrelevant of the field (e.g. economy, finance, politics and others).” – Dobrica Savić (2018), International Atomic Energy Agency, United Nations.
“The grey relational analysis makes up for the shortcomings of mathematical statistics… The research on the grey relational model has made great progress in recent decades.” – Arnold Tukker, professor of industrial ecology, Leiden University.
“[Gray system theory was proposed] to fill the gap between social and natural sciences. Gray system theory and blown-up theory led to a new way of understanding complex and non-linear systems and their evolutionary development.” – Benjamin Hadorn (2016), Swiss entrepreneur and businessman.
Testimonies by industries:
Application in C919 (Chinese airline industry)
“The grey system model was successfully used to help select a research and development team to work on the C919, China’s first domestically produced commercial airliner. The C919 made its maiden flight in May [2017]. The grey system approach was chosen because China had no previous experience in building such an aircraft and therefore had limited reference data.” – Emerging Studies and Applications of Grey Systems (2023), Springer.
Application in Long March B rocket carrier (Chinese aerospace industry)
“The Grey System Theory solved the problems of small data and poor information quality control and reliability experimental analysis of Beijing Institute of Telemetry Technology (北京遥测技术研究所), and ensured the development progress, quality and reliability of supporting products for Long March B carrier rockets.” – Quote from a speech by Naiming Xie (2022)
Application in renewable energy
“A Chinese renewable energy company has also used an advanced grey model in the project that is able to predict when a wind turbine’s gearbox will fail, extending the life of its turbine by 36%, resulting in fewer shutdowns and tens of millions of euros in savings.” – Emerging Studies and Applications of Grey Systems (2023), Springer.
Application in construction/engineering industry
In 2023, a team from a Chinese public civil engineering corporation (机械工业第六设计研究院有限公司) and a university in Taiwan developed a Construction Worker Safety Prediction and Early Warning Tool based on the Grey Absolute Decision Analysis (GADA) method.
Application in Human-centered System Designs
The theory of grey systems, among others, has seen its influence on the generic system model URANOS.
Application in ecology
In 1994, a grey prediction model was used to extrapolate monthly averages for temperature and precipitation at a site in Northern Canada. The model provided good representation of both temperature and precipitation.