Dynamic Coupling Characteristics And Control Method For 2F2R Macro-Micro Manipulator

With the development of national economy and the progress of science and technology,higher requirements have been put forward in many areas such as special petroleum equipments, modern manufacturing and MEMS. There are some examples such as reducing energy consumption with light weight, improving efficiency with high speed, being applicable to special operations with high positioning accuracy and particular work environment with broad movement space. Lightweight of the manipulator will increase the flexibility of components and decrease the structural natural frequencies; high speed movement of the manipulator will increase the inertia force and the excitation frequency for which the elastic vibration and motion error will be enhanced. Therefore, traditional analysis and design methods in which the manipulator is assumed to be a rigid body have limitations,the adverse effect caused by elastic deformation of the manipulator must be considered in order to acquire higher motion control performance.Under this background, the flexible-macro and rigid-micro manipulator is proposed as a structure scheme, whose objective is to achieve both broad space motion and high accuracy endpoint control. The current point of view, most researches on this kind manipulator are based on the hypothesis that the coupling problem between the micro manipulator and the macro manipulator can be ignored due to the former is very small relative to the latter. This treatment method can simplify the analysis of related problems. However, it can also bring difficulties to the design and control of the macro-micro manipulator. In fact, the coupling problem between the two can not be avoided in many applications because there is no clear boundary between the large one and the small one. For now, there are few researches in this area and most of them are not systematic. This paper use this 2-Flexible-Macro and2-Rigid-Micro manipulator as research object(which is abbreviated as 2F2 R macro-micro manipulator in the paper), which will be studied and analyzed systematically in several aspects such as elastic vibration mechanism, kinematics model, dynamic model, coupling dynamic characteristics, elastic vibration reduction and error compensation.As the dynamic equation of the flexible-macro and rigid-micro manipulator is highly coupled and nonlinear, it is very difficult to use the dynamic equation to study the coupling vibration mechanism of this kind system directly. Base on the analogy method, this paper establishes a simplified model with mass element, spring element and damp element.Furthermore, this paper analyzes and discusses the elastic vibration mechanism in three aspects of frequency characteristics, energy transfer and control stability at full length.In the aspect of kinematics modeling, a method of workspace decomposition is presented in this paper, by which the inverse kinematics problem of the macro-micro manipulator can be decoupled and the analysis of problems can be simplified significantly.After that, the close connections between elastic deformation and system motion state can be demonstrated clearly and the transform relation between joint space and operation space is extremely complicated.In the aspect of dynamic modeling, the elastic deformation of the macro manipulator is described with Bernoulli-Euler beam element based on Finite Element Method. On this basis,the dynamic model of 2F2 R Flexible-Macro and Rigid-Micro manipulator can be derived through the second Lagrange equation. Since the rigid-flexible coupling of this system is considered fully, the model has advantages of generality and extensibility and has the characteristics of strong coupling and nonlinearity.In the aspect of system coupling dynamic characteristics analysis, three important characteristics of the 2F2 R Flexible-Macro and Rigid-Micro manipulator are researched in the paper such as frequency characteristics, motion error characteristics and scale effect characteristics. Many system factors such as structure parameters, section parameters,material, distribution of lumped mass and motion parameters are analyzed and discussed to ascertain their effects and change laws on the coupling dynamic characteristics, and then much valuable information are acquired.In the aspect of elastic vibration reduction and error compensation, three kinds of motion control problems are studied in the paper. First, motion laws of the manipulator's joint angle are analyzed and compared by means of Cam Curve Theory, in order to study how to ensure the elastic vibration in the process of point-to-point movement as small as possible. Second,how to utilize the quick adjustment effect of the micro manipulator to suppress residual vibration is studied in the paper. Third, as for the continuous trajectory tracking, how to utilize fast motion of the micro manipulator to compensate for the motion error caused by the elastic deformation of the flexible-macro manipulator is studied in the paper.In the end, the experiment platform of the 2F2 R Flexible-Macro and Rigid-Micro manipulator is established. Theories and methods proposed in this paper are verified through the comparative analysis between experimental results and simulation results.