Materials Science Forum Vols. 626-627

Abstract: Stewart platform manipulator robot is a six degree of freedom, parallel manipulator, which consists of a base platform, a mobile platform and six limbs connected at six distinct points on the base platform and the mobile platform respectively. The direct position analysis problem of Stewart platform relates to the determination of the mobile platform pose for a given set of the lengths of the limbs. In this paper, we present a concise algebraic method for solving the direct position analysis problem for the fully parallel manipulator with general geometry, often referred to as General Stewart platform manipulator. Based on the presented algebraic method, we derive a 40th degree univariate polynomial from a determinant of 20×20 Sylvester’s matrix, which is relatively small in size. We also obtain a complete set of 40 solutions to the most general Stewart platform. The proposed method is comparatively concise and reduces the computational burden. Finally the method is demonstrated by a numerical example.

Abstract: A simplified one-dimensional model, accounting for thermal errors related to high speed spindle of 5-axis CNC machine tools, is developed, and the relationship between heat sources of rotating spindle and thermal deformation in axial direction is found with the help of Fourier’s law for heat transfer under two different boundary conditions. Based on the theory of homogeneous coordinate transformation in robotic, the transformation matrixes between the coordinate system of kinematic pairs and the relationship between errors and compensations are obtained, through which the compensation of thermal errors in high speed motorized spindle is obtainable.

Abstract: A new parallel kinematic machine UPS-2RPS with serial input limb is presented, the topological structure characteristics are described. The mathematic model of inverse position solution is derived. The workspace of the mechanism is analyzed and researched by results of MATLAB and Pro/E simulation, The research will be of great significance to promote its novation, application and spread .

Abstract: Based on the achievements of early works, a volumetric error modeling flow which is based on multi-body system theory is put forward. The flow includes 4 key steps mainly: describing structure, setting up coordinate system, creating characteristic matrix and generating volumetric error model are respectively. The operating method of every step is discussed in detail and the solving formula is given. At last, taking the VMC650 machining center of milling and boring which is developed by a machine tool factory as example, the validity of modeling flow is verified. This study can be used as a reference for opening automatic modeling system.

Abstract: The stiffness model of the parallel machine tool is established by static analysis, the static stiffness analysis is carried out through numerical Simulation and the stiffness distribution is given. On the basis of this, the optimal objective is given which is the average of 729 values of -axis stiffness and -axis stiffness corresponding to 729 positions in the workspace. With MATLAB software, the effects are simulated which the structural parameters of the parallel machine tool have on their stiffness, their change rules are gained, and this provides a basis for the structural design of this type of machine tools.

Abstract: At present, almost all the cocking work is completed in smoke-filled kitchen, which is a time-consuming and laborious work. However, with the development of automatic and robotics technology, how to apply the relevant technology to the field of cooking has become increasingly urgent. The purpose of this paper is to apply quick-return mechanisms to automatic cooking robot, so as to obtain the realization of the movement of reversing pot. And the main three parts of the study are: the analysis of several typical quick-return mechanisms and the description of their possibility in realizing the movement of reversing pot; dynamic simulation analysis of some kinds of mechanisms, which can cover the basic requirements of the movement of reversing pot, is done so as to determine their functions in realizing the movement of reversing pot and their different characteristics; through taking the typical Sharper(quick-return swing guide) agency as an example and using Pro/E and Adams to realize the dynamic simulation and analysis, the key parameters of such bodies is selected and can provide the basis for the further study of automatic cooking robot.

Abstract: In order to investigate that shields have the effect on the thermal equilibrium of CNC machine tool, this paper applies the theory of heat transfer and finite element analysis to analyze the thermal characteristics of CNC lathe CK40A/1000. By ANSYS software, the temperature distributions of spindle engine, headstock and bearing at thermal equilibrium with/without shields are obtained. By analyzing thermal equilibrium patterns and experiments, the temperature of spindle bearings with shields are 3-4 higher than without shields at thermal equilibrium. And shields have less influence on the temperature gradient of tool inner thermal sources.

Abstract: One of the important factors resulting in the performances of the machinery is its dynamic characteristics. The spindle assembly is one of the usual parts of NC machine tool, so its dynamic-static characteristics will affect the performances of machine tool. The study is based on a NC machine tool produced by a certain plant of machine tools. The finite element dynamic analysis model of spindle assembly was developed by introducing two or three groups of circumferential spring damper elements which are arrange at different angle around the spindle, and the effect of different supporting conditions and different arrange angle on the modal analysis of the spindle assembly were discussed. The finite element analysis on spindle and spindle assembly has been made to confirm its dynamic characteristics. Then the finite element analysis models are validated by some experiments.

Abstract: A solution to the problem of the elimination of the chattering effect and the improving of the convergence speed for sliding mode control is presented in this paper.A new dynamical sliding mode controller is developed which takes the first derivative of the control signal instead of the actual control as control and results in smoothed control inputs to the given system.A new nonlinear sliding mode surface is devised which can improve the convergence speed in the sliding phase.Exponential reaching law is taken to determine the control law which can improve the convergence speed in the reaching phase.A mobile manipulator with two arms is taken as an example to track a given trajectory with the proposed controller. It is found that the new developed method has a high convergence speed and the chattering is also reduced greatly.

Abstract: An improved interpolation method is presented based on B-spline curve back calculation which regards data points as control points. First, a B-spline surface reconstruction is done, and a favorable condition for real-time interpolation can be provided for NC machining. Then, by prejudging the trajectory feedrate, the tangent vectors of spline curve junction can be calculated, which can be used to establish the spline curve equations based on time. At last, with the equations mentioned above, the trajectory and feedrate profile can be generated simultaneously by the improved interpolation algorithm. An error analysis is also discussed and the feasibility of the improved algorithm is verified by the simulation results.