Human - machine - environment system engineering [1] is a new comprehensive edge technology subject, related research thinks, the theory will help to better solve the problem of the full rehabilitation practice [2]. Into the 90 s, their ideas began to permeate been engineering of literature [3-5]. We try to use of man - machine - environment system engineering theory to study the specific problems in rehabilitation engineering, intelligent fine swinging leg prosthesis control [6], the effect is good, this prompted us to further discuss this subject in the rehabilitation engineering generality and methodology.This paper will report the main result of this study.And to put forward to break the rehabilitation engineering "collage" image, looking for theory mainline (supporting theory), perfect its theoretical system.

　　1. The human - machine - environment system engineering, machine, environment of three elements of system is called the human - machine - environment system. By using the theory of system science and system engineering method to correctly handle the relationship between the three elements, which make the system to achieve the optimal combination. Since world war ii after the first appeared, ergonomics, human factors engineering psychology, ergonomics, human factors engineering and man-machine system and so on many subjects, so the accumulated person, machine and environment from different angles of the experimental data and experience. Human - machine - environment system engineering the above subjects into a unified framework of science, to avoid the chaos in the concepts and terminology, and from the overall height of the system were studied. It with general man - machine system one of the important difference is that the environmental factors as active positive factor is introduced into the system, rather than as a passive interference factors. Rough in terms of "human - machine - environment system engineering = human body engineering, system engineering and the environmental factors as a proactive positive factor is introduced into the system". More than 10 years to robust the discipline development, in the main application in the aerospace medical engineering, aviation industry, defense industry and military, etc., the current is gradually expanding its application field.

　　2. Rehabilitation engineering research object is a typical man - machine - environment system of rehabilitation engineering in engineering and technology to help the disabled to independent living return to society, the concept itself contains the people at the same time (disabled), machine (the main form of engineering technology), environment (namely life care, return to society, to adapt to the natural and social environment) three elements. The lack of the disabled and the environmental characteristics of the inspected deeply, can’t be designed to meet the requirements of the disabled rehabilitation engineering products. Only for the disabled, rehabilitation engineering products, natural and social environment makes a comprehensive analysis, the relationship between the may prescribe the best rehabilitation engineering products. So the research object of rehabilitation engineering is not only a rehabilitation engineering product itself, but the disabled, rehabilitation engineering products, environment of human - machine - environment system. Different types of disability, different degree of disability of the same kind of disability, the applicable rehabilitation engineering products are very different, indicating that human factor strongly in the rehabilitation engineering man - machine - environment system. The human body itself is a huge system, disability more big its complexity, it fundamentally determines the rehabilitation engineering man - machine - environment system complexity, typicality. Such as rehabilitation engineering is a basic problem of wheelchair prescription should be considered factors are: grasp the various performance parameters of the wheelchair, the disabled, organization of neuromuscular state, body deformation sensitivity, body function, selecting tendency, transport, security, seat matching, psychosocial factors, nursing staff, school, community, family, time, distance, career goals, funds, supply situation and the maintenance of local wheelchair [7]. The wheelchair prescription is for people with disabilities, wheelchair. The use of human - machine - environment system to analyze the overall decision-making process. In fact of prosthetic rehabilitation engineering control, design of crutches and feeling Can charge device research and so on various aspects of the object are typical of the human - machine - environment system [5].

　　3. The rehabilitation engineering man - machine - environment system engineering methodology since the research object of rehabilitation engineering is a typical human - machine - environment system, we can put the human - machine - environment system engineering theory, principles, methods and degree of application been project, so as to perfect the working method and theoretical system of rehabilitation engineering. Through the migration project called rehabilitation project constructed by the man - machine - environment system engineering methodology (referred to as "man machine ring methodology), its basic principle is as follows (8, 1).

　　3.1 rehabilitation engineering research methods Summarized as (1) three theory, control theory, model theory, optimization theory: cybernetics with general concept of system, information and feedback to break the line between life and non-life, make people can use unified point of view and scale to human, machine and environment the three distinct physical properties of objects, and make it become a secret inseparable organic whole; Model theory for human - machine - environment system engineering research to provide a complete set of mathematical analysis tool, mathematical model is introduced to characterize quantitatively the movement rule of the whole system, and to seek the optimal combination of the human - machine - environment system point of view and train of thought, is the essence of human - machine - environment system engineering; Optimization theory is the essence of mathematics.(2) three elements (man, machine, environment) : starting from the overall height of the system, should not only study the performance of the elements themselves, but also to study between the three elements of information transmission, processing and control, and so on. The disabled is the rehabilitation project of man - machine - environment system work background, characteristic analysis for the disabled is the base and key of rehabilitation engineering research, is also the difficulty. Features for the disabled is very complex, including the human body measurement, athletic ability, perception, working load, control, and decision-making model.(3) three stages (decision making, the development and production, actual use) : can be understood as a rehabilitation engineering problem is divided into class project decision-making, such as the stair climbing wheelchair establishment; The development and production such as the development of the intelligent prosthesis; Actual use such as wheelchair prescription.(4) three goals (the safe, efficient and economic) : for the purposes of quantitative analysis, the three goals must be fused into a single index, so the definition of comprehensive evaluation value of Q = W1 * economic security + W2 x efficiency + W3, W1, 2, 3 for the weighted coefficient of W1, W2 and W3 = 1. The system efficiency of system working effect and function of working load.

　　Rehabilitation engineering work According to the processes are shown in the appended drawings.

　　The appended drawings of rehabilitation project workflow 4 application of rehabilitation engineering, man-machine ring methodology new understanding of the problem Past the contents of the rehabilitation engineering research traditional transverse points such as the functions of motion compensation device, mobile compensatory auxiliary device and sensory function acting device such as [5];Now start from man-machine ring methodology for longitudinal classification is (disabled), machine (rehabilitation engineering products), environment (natural social environment for the disabled) characteristics of the study, people - authority department, the people - ring, ring machine - relations research, man - machine - environment system research of overall performance. The new classification will provide new perspectives and new research opportunity, make originally the wrong heald complex problem becomes clear and orderly.

　　Rehabilitation engineering research methods and workflow mode (or) making rehabilitation engineering work is no longer their own ways, but have a rhyme. The scientific method and the program will promote rehabilitation engineering works carried out effectively. The intelligent control of swing leg prosthesis fine research, is the working model of a typical application.

　　4.Rehabilitation engineering work guidance and several practical principle [1] (1) the reasonable points with people, machine, environment function: the function of rehabilitation engineering system need to be borne by the people, machine, environment, respectively, in the case of system function is the same, three elements bear the function of the share can have different combinations, Q value under some form of combination system optimal. The function of the reasonable distribution of man, machine, environment is according to the characteristics of three elements complement each other, phase to profit.(2) the interface between the reasonable designer, machine and environment: the interface is between human - machine - environment system elements of information (information) can be considered as a special form of matter and energy exchange place, a good interface design will make the system has a good correlation between the to element form and get a good overall performance. Rehabilitation project of human - machine interface, people - and machine - ring interface, its research is often at the interface, so that the rehabilitation engineering products also have the interface/interface equipment [9]. (3) the environmental factors as a positive factor is introduced into the system: rehabilitation engineering "positive environment" is a kind of effective means to solve the problem, such as for people with disabilities in public buildings, inside and outside the passage, the development function of complex mixed personal mobile auxiliary machinery is clumsy and not reality, but barrier-free facilities this positive environment has ingeniously solved the problem. The environmental control system of the study was to create a new, controllable and artificial environment actively, in order to fully support the daily lives of people with disabilities, it is an important research field of rehabilitation engineering [5].

　　5. C onclusions based on decades of rehabilitation engineering practice and theoretical achievements as the background, on the basis of the human - machine - environment system engineering, using logical analysis, inductive method are discussed. We think that the research object of rehabilitation engineering is a typical man - machine - environment system; Human - machine - environment system engineering is the supporting theory of rehabilitation engineering, it can be applied to build rehabilitation engineering theory of the main line, perfect the theory system, working for rehabilitation engineering provides a new means of valuable knowledge and guiding principles, research methods, the working process, believe that will bring new look to rehabilitation engineering theory and practice.

　　Author's unit: bright and sealing, Zhang Jichuan, Liu Yongbin, Jin Dewen Rehabilitation Engineering Institute of China Rehabilitation Research Center (Beijing 100077); Zhang Jichuan Tsinghua university