Error estimation and sensitivity analysis of the 3-UPU translational parallel robot due to design parameter uncertainties (original) (raw)
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Prediction of the pose errors produced by joints clearance for a 3-UPU parallel robot
Mechanism and Machine Theory, 2009
This paper deals with the singularity analysis and modeling of the effects of the clearance in the joints on the parallel robot accuracy. This model is presented in an analytical form, which allowed us to predict easily the pose error for a given external load, a nominal pose and the structural parameters of the 3-UPU parallel manipulator. Based on this model, we also developed an algorithm to map the pose error within the workspace of the robot.
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This paper presents the modelling and experimental evaluation of the gravity compensation of a horizontal 3-UPU parallel mechanism. The conventional Newton-Euler method for static analysis and balancing of mechanisms works for serial robots; however, it can become computationally expensive when applied to the analysis of parallel manipulators. To overcome this difficulty, in this paper we propose an approach, based on a Lagrangian method, that is more efficient in terms of computation time. The derivation of the gravity compensation model is based on the analytical computation of the total potential energy of the system at each position of the end-effector. In order to satisfy the gravity compensation condition, the total potential energy of the system should remain constant for all of the manipulator's configurations. Analytical and mechanical gravity compensation is taken into account, and the set of conditions and the system of springs are defined. Finally, employing a virtual reality environment, some experiments are carried out and the reliability and feasibility of the proposed model are evaluated in the presence and absence of the elastic components.
2014 IEEE International Conference on Robotics and Automation (ICRA), 2014
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Science in China Series E Technological Sciences, 2002
This paper presents an error modeling methodology that enables the tolerance design, assembly and kinematic calibration of a class of 3-DOF parallel kinematic machines with parallelogram struts to be integrated into a unified framework. The error mapping function is formulated to identify the source errors affecting the uncompensable pose error. The sensitivity analysis in the sense of statistics is also carried out to investigate the influences of source errors on the pose accuracy. An assembly process that can effectively minimize the uncompensable pose error is proposed as one of the results of this investigation.
Journal of Advanced Mechanical Design Systems and Manufacturing, 2008
We present an optimum design of lower-dof parallel mechanism, a 3-URU pure rotational parallel mechanism that reflects issues of workspace and the position error of the center of rotation of the platform. The uncompensatable error determined by position error of center of rotation was used as an evaluation index for the design. The uncompensatable error index, an index used in the optimum design, was proposed taking into account four sources of errors, representing errors between adjacent joints. Based on the application of the mechanism and the error index, the effect of the redundant platform orientation parameter was numerically investigated and the design flow of the mechanism was proposed. We made a kinematic design of a mechanism with a large workspace subject to minimization of platform's position error of the center of rotation. A prototype of mechanism with a large inclination angle of the platform up to 1.3 rad was shown, and its characteristics are also discussed.
CIRP Annals - Manufacturing Technology, 2002
This paper presents a unified geometric error model that enables the tolerance design, assembly and calibration of a class of 3-DOF parallel kinematic machines with parallelogram struts to be integrated into a comprehensive framework. The error mapping function is formulated with a goal that enables the source errors affecting the uncompensatable pose error to be found. This is followed by the investigation into the influences of source errors on the pose accuracy with the aid of sensitivity analysis. The assembly process that enables to effectively reduce the uncompensatable pose error is also proposed.
J. Mechanisms Robotics, 2012
This paper deals with the error modelling and analysis of a 3-PPR planar parallel manipulator with joint clearances. The kinematics and the Cartesian workspace of the manipulator are analyzed. An error model is established with considerations of both configuration errors and joint clearances. Using this model, the upper bounds and distributions of the pose errors for this manipulator are established. The results are compared with experimental measurements and show the effectiveness of the error prediction model.
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Hexarot is a robotic manipulator that belongs to the family of axis symmetric parallel mechanisms. The robot is able to move the robot platform or tool center point in six degrees of freedom (DOF). This paper presents the kinematics model of the robot including the inverse and forward kinematics, and its time derivatives. Then using the kinematics formulations, investigation of the nonlinear motion of the Hexarot robot for a desired linear motion path is performed. For this purpose, the concept of curvature of the robot path is used for measuring the nonlinearity of the actual motion of the robot. The nonlinear motion error of the robot is analyzed for the scenario where the platform moves on a linear path between two arbitrary points of the robot workspace. The effects of different parameters on the nonlinear motion error of the mechanism are demonstrated and strategies for motions with low error values are proposed.