Dongjun Zhang

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Due to the joint clearance, parallel manipulators always exhibit some position and orientation errors at the mobile platform. This paper aims to provide a systematic framework for the error analysis problem of general parallel mechanisms influenced by the joint clearance. A novel and efficient method is proposed to evaluate the maximal pose errors of(More)
This paper proposes to optimally design a parallel machine based on multiple criteria. Many criteria, workspace, condition number, accuracy, stiffness, maximum velocity, and maximum force, are considered. The optimal design problem is proposed as to find a set of design parameters such that (a) the Cartesian workspace generated by the resulting manipulator(More)
Recent work recognizes that cross-coupled control (CCC) can improve the accuracy of contour tracking in biaxial systems evidently. In this paper, a structure, ejecting the cross compensated control effort into the position input directly, is proposed. In order to obtain the cross-coupling gains, an approach for contour error approximation to arbitrary(More)
In this paper we concentrate on contouring control for surface machining. The object of the motion control system is tracking the spatial curve lying on the surface. Observing that the contour error can be approximated by the tracking error (projected to the normal subspace of the surface), we propose a new design procedure based on the geometrical(More)
In the path following motion control system, the reference tool path of the machine tool is geometric curves predetermined by applications. The reference motion command for servo control system is generated based on the geometric tool path and the feedrate. The command generation module is called path interpolation. It is a classical problem in the motion(More)
In the contouring control, the trajectory and the tolerance information are specified in the task space. Based on this observation we propose to design the controller in the task space directly. First, by defining the projection map on the cotangent space of the mechanical system the equation of motion is derived in the task space. Then a novel contouring(More)
For high speed high accuracy 3D machining, the controller design is very important. The object of the control system is to minimize the contour error which is related to the tracking error of each individual servo axis. From the analysis of the tracking error, both the phase delay and the gain difference generate tracking error. In this paper we propose a(More)
Accurate modeling and identification to the dynamics of the feed drive system is significant in designing a high performance milling machine. In this paper, mathematical model of the feed drive system, including electromagnetic and mechanical aspects, is concluded. To be consistent with the controller design techniques, two different grey-box identification(More)
Scutellaria altissima L. is a common traditional Chinese medicine used to treat inflammation in some countries. Scutellarin, an active major flavone glycoside isolated from the traditional Chinese medicine Scutellaria altissima L., has been shown to offer various beneficial biochemical effects on cerebrovascular diseases and inflammation. However, the(More)
To avoid deteriorating the mechanism's performance, joint clearance can be eliminated by preloading the pairing elements of the joint. However, this paper proves rigorously that in the real world, the unavoidable assembly and manufacturing errors will cause overconstrained parallel manipulators to lose degree of freedoms, or even unable to be assembled if(More)
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