Structure Design And Control Study Of 2-DOF Angle Test Platform

By the requirements in engineering practice, this thesis researches a platform which is in order to know the case of transmission's temperature balance point and oil leakage under simulated road conditions. In the study of development and research status at home and abroad, found that in the development process of less DOF parallel mechanism platform, with the improvement of accuracy?control? stiffness? stability and load capacity requirements, the research on parallel mechanism deepening.By introducing the concept of screw into Spatial Mechanism, which solves the problems of analysis of parallel robot mechanism and synthesis problems.1.On the basis of improvement on 3-UPU parallel platform,a fixed steady added on the center of top platform. There is a Hooke joint between the platform and steady, to ensure that the platform has 2 rotational degrees of freedom. This structure makes the steady under the center of top platform undertakes top platform's weight, the driving force of the motor cylinder related with gravity torque which released by top platform's center of gravity to top platform's rotational center. In the center of platform establish a fixed coordinate system and a moving coordinate, the upper and lower hinge points of platform are written in form of coordinate in the moving coordinate system and the fixed coordinate system, calculate the model's DOF and kinematic analysis by the method of mathematical model. Kinematic analysis includes positional direct problem and inverse problem. The direct problem of platform's kinematic analysis is that known the length of the three actuators to solve the swing angle of the moving platform in the spatial coordinate system; inverse problem is that known the position of platform solve the length of three actuators,the quantitative expression between platform position and the length of three actuators were studied. Through MATLAB simulation, we get the length range of three actuators, and provide reference for choose electric cylinder.2. According to the system performance requirements for two degrees of freedom platform, we designing and realizing the total scheme and frame of system. station construction program overall design, after built three-dimensional solid modeling in Pro / E, we can get quality of components, centroid, moment of inertia and other parameters, in the desired operating range, check rationality of movement and interferometric inspection body movement among components,if there is a problem, optimization design of mechanism; by using virtual prototyping technology, establish model in ADAMS, defined constraint type? connection? drive type and then simulation, analysis electric cylinders' variation of displacement?speed and the driving force in the post-processing module(Adams/Post Processor). Simulation result about electric cylinders' displacement is consistent with the kinematics analysis, the max displacement of electric actuator is at the position when platform running composite motion. Because there are motor and transmission on platform, the quality of motor and installation location affect the driving force of electric cylinder. In order to reduce the driving force, change the installation position of motor in the platform and reduce the height of motor installation center. Finally, the simulate result showed that maximum driving force is generated in compound conditions.3. In the design of the control scheme, in order to improve the rigidity and stability of the structure, this thesis select redundant drive method, increases the difficulty of control. Since the electric cylinder displacement and velocity changes work is not a linear symmetrical laws, the displacement and speed changes of three electric actuator are different when platform at roll? pitch and both swing conditions. The control program can be selected PLC(Programmable logic controller,), via an external pulse position control mode(PTI mode) and torque control mode(T mode), respectively controlling the electric cylinder, after the definition of the electronic gear ratio of the motor, there is a relationship between pulse and electric cylinder stroke, through the angle sensor readings, check the angle of the movable platform is in place, corrected the error by the program until the platform to correct position.This paper studies the parallel platform position and orientation relationship with the electric driver's stroke, ADAMS simulation analysis by combining kinematics of the motion platform is analyzed to verify the correctness of theoretical analysis, and provide the basis for the control policy.