Theoretical And Experimental Study On Hybrid Machine Considering Frictional Force Of Joint

Hybrid machine has both a certain extent flexibility and higher rigidity, and can successfully solve the contradiction between flexibility and carrying capacity in theoretical way. Accurate realizing the given motion is the main function of hybrid machine. But the dynamic performance and running precision is affected by frictional force in system. Considering the frictional force in design and analysis of mechanical system is beneficial to improve running efficiency and dynamic performance, which is significant in theory and practice. The purpose of this dissertation is to study thoroughly the dynamic, control and detection characteristics of planar 2-DOF hybrid machine considering frictional force.A new planning method is put forward to realize continuous trajectory of hybrid machine. First, using implicit function theorem, the workspace of five-bar mechanism is determined, and the positional relationship between workspace and realizable trajectory by hybrid machine is analyzed. Then a describe method for closed continuous trajectory by subsection third spline function is presented, and trajectory with second order derivation continuity is set up. Considering peculiarity of the hybrid machine, the corresponding of input movement and time is gained by inverse-kinematic analysis. And the input motion rule of cranks are obtained by RBF(Radial Base Function) neural network which is trained using the data of time and input parameters as learning sample. The result of simulation shows this planing method has good accuracy.A novel method for detecting the output trajectory of hybrid machine based on computer vision is put forward. First, the visual system is designed and formed, in which the operation of image gathering, image storage and processing can be performed. An amended Tasi camera calibration approach when the camera plane is parallel to the plane of calibration board which is used to provide calibration data is brought up. Three kinds of image processing algorithms under the condition of lower contrast is introduced. The algorithms of object detection, object segmentation and precise location on the basis of image sequence have researched. Using the formed visual system, the experiment on detecting movement trajectory of hybrid machine has carried out. The experimental results indicate that the visual system has good accuracy on position and velocity detecting.A dynamic modelling method of hybrid machine in considering joints'friction is put forward. The mathematics model of joint friction in mechanical system is presented, in which the action forces in joint are converted into ideal constraint force and friction moment. Friction is dealt with special non-inertia force, and amended Kane equation includeing the frictional force of system is put forward. The dynamics model of five-bar hybrid machine is proposed using Kane's method, in which the joint friction is considered. An arithmetic is presented to solve these equations. The outcomes of simulation indicate that joint friction has obvious influence on motion parameters of the mechanism.A fresh control measure of hybrid machine for trajectory tracking is presented, in which the uncertainty of system and the velocity fluctuation of constant velocity motor are considered. The motion of constant velocity motor is detectable but uncontrollable in hybrid system. The dynamic model of hybrid machine is reduced on detecting angular displacement of constant velocity motor. The control strategy for controllable motor ground on tracking the motion of constant velocity motor is proposed. An adaptive fuzzy sliding mode controller considering the uncertainties and external disturbance of the system is designed for trajectory tracking of hybrid machine. Frictional force, external disturbance and other nonlinear errors are integrated into an uncertain factor. The gain of control is acquired by approximating the sum of uncertainties of the system on the basis of adaptive fuzzy control, and the chattering in sliding mode control is eliminated in the controller. The results of simulation indicate the effectiveness of the strategy and controller.A new type of frictional sensor is designed on the basis of flexure hinge. An universal calculation method for compliance of flexure hinges has deduced on the basis of mechanics theory. The method is handy for all types flexure hinges. The compliance equations for right circular flexure hinges under the condition of planar forces are presented, and the relationships between compliance and dimensions of right circular flexure hinges are analyzed. A new type of frictional transducer is designed by assembling two flexure hinges and two uniform cantilever beams. The influence of friction and reversal clearance which exist in the parts of traditional sensors are avoided, and the continuous measure of friction factor is realized. The expression of interaction between normal force and friction is deduced using theory of structural mechanics. The dimension of transducer is optimized under the condition that part sizes of the sensor are given. Therefore the couple of normal force and friction is eliminated. The results of experiments proved the availability of the sensor.The experimental platform for trajectory generating and detectig of planar hybrid machine is set up. It is composed of the 5R mechanism, control system and visual detecting system. A novel test device which can realize the dynamic synchronization of cranks at initial angular displacement, and the synchronous control of ordinary motor and servo-motor is achieved. Experiment of given trajectories generating and detecting have been carried out. And the expe-rimental results indicate that the proposed methods can realize the given trajectory.