Accuracy issues of parallel kinematic machine tools

Abstract

Parallel kinematic machines (PKMs) have been attracting attention in research institutes as well as in the machine tool industry because of their structural rigidity due to their closed kinematic loops and their conceptual capabilities in high dimensional accuracy. During performance evaluation of the rst prototypes of parallel machine tools, it turned out that their accuracy has not yet reached industrial application level. Against this background, the accuracy behaviour of a hexapod milling machine, located at the Laboratory for Machine Tools and Production Engineering (WZL) at Aachen University of Technology, and accuracy-related design issues have been extensively studied. Based on these investigations, strategies for kinematic calibration and error compensation have been developed.

Precision motion control for the parallel mechanism of a virtual axis machine tool

“…The correspondent parameters are the current feedback gain i K , the power amplifier gain a K , the speed loop gain pre K , the velocity feedback coefficient v K , the winding resistance of the AC servo motor P R (Ω), the winding inductance p L (H), the torque constant tp K ( N m / A ⋅ ), and the total rotational inertia of the AC servo motor axis J ( 2 kg.m ). The transfer function of the controlled object for the virtual axis machine tool control system is 3 …”

“…Therefore, it is hard to achieve the precision motion control of a virtual axis machine tool, which is one of the biggest obstacles of commercialization of a virtual axis machine tool in high precision machining field. It is urgent to solve this problem [3].…”

A Structure Error Compensation Method for the Parallel Mechanisms

“…At present, the scholars mainly pay attention to the kinematical parameter error, as in [1][2][3][4][5][6][7][8]. Through compensating to the kinematical parameter error, we can delete a part of the structural error, but it can not satisfy people's expectation (i.e.…”

“…For example, we can apply total differential method, as in [1], to the forward kinematical results, taking the kinematical parameters as differential variables, then get the relations between kinematical parameter errors and orientation error of moving platform; and can use the construction method to calculate error Jacobian matrix. We can enhance the accuracy of the mechanism by calibrating the kinematical parameters, as in [3][4][5][6][7][8]. These studies mainly concentrate on the influence of the kinematical parameter errors to the orientation error of moving platform.…”

Sliding Model Control with Upper Bound Adaptive Learning for Virtual Axis Machine Tool

“…Currently, Virtual axis machine tool is widely used in the machining process of complicated curved surface [1,2],comparing with traditional machine tool, the virtual axis machine tool have the features with big stiffness , high precision, tight structure, small motion inertia, good cutting stability and so forth [3],but the performance of the virtual axis machine tool will be affected by the factors, such as manufacturing and assembly errors, clearances, errors caused by steady state cutting load and the gravity, thermal deformation error and so on [4].…”