A New Measurement Device for Kinematic Calibration of Parallel Manipulators

2004 ◽  
Author(s):  
Abdul Rauf ◽  
Sung-Gaun Kim ◽  
Jeha Ryu
Keyword(s):  
Parallel Manipulators ◽  
Measurement Procedure ◽  
Initial Guess ◽  
Measurement Noise ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
End Effector ◽  
Experimental Procedure ◽  
New Device ◽  
Rotation Component

Kinematic calibration is a process that estimates the actual values of geometric parameters to minimize the error in absolute positioning. Measuring all the components of Cartesian posture assure identification of all parameters. However, measuring all components, particularly the orientation, can be difficult and expensive. On the other hand, with partial pose measurements, experimental procedure is simpler. However, all parameters may not be identifiable. This paper proposes a new device that can be used to identify all kinematic parameters with partial pose measurements. Study is performed for a 6 DOF (degree-of-freedom) fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector’s motion to 5 DOF and measures two position components and one rotation component of the end-effector. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise. Intrinsic inaccuracies of the device can significantly deteriorate the calibration results. A measurement procedure is proposed and cost functions are discussed to prevent propagation of the inaccuracies to the calibration results.

Complete parameter identification of parallel manipulators with partial pose information using a new measurement device

Robotica ◽  
2004 ◽  
Vol 22 (6) ◽  
pp. 689-695 ◽  
Author(s):  
Abdul Rauf ◽  
Sung-Gaun Kim ◽  
Jeha Ryu
Keyword(s):  
Parallel Manipulators ◽  
Error Reduction ◽  
Initial Guess ◽  
Significant Error ◽  
Degree Of Freedom ◽  
Kinematic Parameters ◽  
Measurement Device ◽  
End Effector ◽  
Six Degree Of Freedom ◽  
Noisy Measurements

A new measurement device is proposed for the calibration of parallel manipulators that can be used to indentify all kinematic parameters with partial pose measurements. The device while restricting the motion of the end-effector to five degree-of-freedom measures three components of posture. A study is performed for a six degree-of-freedom fully parallel Hexa Slide Manipulator. Intrinsic inaccuracies of the measurement device are modeled with two additional identification parameters. Computer simulations show that all parameters, including the additional parameters, can be identified. Results show a significant error reduction, even with noisy measurements, and reveal that the identification is robust against errors in initial guess.

A Simple Two-step Geometric Approach for the Kinematic Calibration of the 3-PRS Parallel Manipulator

Robotica ◽  
2019 ◽  
Vol 37 (5) ◽  
pp. 837-850
Author(s):  
Genliang Chen ◽  
Lingyu Kong ◽  
Qinchuan Li ◽  
Hao Wang
Keyword(s):  
Parameter Identification ◽  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Calibration Method ◽  
Kinematic Parameter ◽  
Geometric Constraints ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
Positioning Accuracy ◽  
Kinematic Parameter Identification

SummaryKinematic calibration plays an important role in the improvement of positioning accuracy for parallel manipulators. Based on the specific geometric constraints of limbs, this paper presents a new kinematic parameter identification method for the widely studied 3-PRS parallel manipulator. In the proposed calibration method, the planes where the PRS limbs exactly located are identified firstly as the geometric characteristics of the studied parallel manipulator. Then, the limbs can be considered as planar PR mechanisms whose kinematic parameters can be determined conveniently according to the limb planes identified in the first step. The main merit of the proposed calibration method is that the system error model which relates the manipulator’s kinematic errors to the output ones is not required for kinematic parameter identification. Instead, only two simple geometric problems need to be established for identification, which can be solved readily using gradient-based searching algorithms. Hence, another advantage of the proposed method is that parameter identification of the manipulator’s limbs can be accomplished individually without interactive impact on each other. In order to validate the effectiveness and efficiency of the proposed method, calibration experiments are conducted on an apparatus of the studied 3-PRS parallel manipulator. The results show that using the proposed two-step calibration method, the kinematic parameters can be identified quickly by means of gradient searching algorithm (converge within five iterations for both steps). The positioning accuracy of the studied 3-PRS parallel manipulator has been significantly improved by compensation according to the identified parameters. The mean position and orientation errors at the validation configurations have been reduced to 1.56 × 10−4 m and 1.13 × 10−3 rad, respectively. Further, the proposed two-step kinematic calibration method can be extended to other limited-degree-of-freedom parallel manipulators, if proper geometric constraints can be characterized for their kinematic limbs.

Effect of Link Tolerance and Joint Clearance on End-Effector Positioning of the 3-PSP Manipulator Using Taguchi Method

2015 ◽  
Vol 798 ◽  
pp. 20-24 ◽  
Author(s):  
Fattah Hanafi Sheikhha ◽  
Alireza Akbarzadeh
Keyword(s):  
Taguchi Method ◽  
Parallel Manipulators ◽  
Open Loop ◽  
Joint Clearance ◽  
Kinematic Parameters ◽  
Positioning Accuracy ◽  
End Effector ◽  
Dimensional Tolerance ◽  
Random Nature ◽  
Kinematics Parameters

The use of parallel manipulators in industrial is growing. Among key advantages of parallel manipulators versus their serial counterparts, is their improved end-effector positioning accuracy than open-loop mechanism. However, undesirable dimensional tolerance and joint clearance can decrease the positioning accuracy of the end-effector. In this article, Taguchi method is applied to a 3-PSP parallel manipulator to determine how dimensional tolerance and joint clearance affects the accuracy of its end effector. Because of random nature of dimensional tolerance, it is assumed that actual value of all kinematic parameters are normally distributed. Taguchi method is then used and effect of tolerance on accuracy for each of the manipulator kinematics parameters is obtained. Finally, a tolerance set resulting in best accuracy is predicted by the Taguchi method. This tolerance is verified with a new set of experiment.

FIXTURELESS CALIBRATION OF PARALLEL MANIPULATORS

1997 ◽  
Vol 21 (3) ◽  
pp. 273-294 ◽  
Author(s):  
L. Notash ◽  
R.P. Podhorodeski
Keyword(s):  
Parallel Manipulators ◽  
Calibration Model ◽  
Kinematic Calibration ◽  
Objective Functions ◽  
End Effector ◽  
Displacement Sensors ◽  
Calibration Models ◽  
End Distance ◽  
Order Of Magnitude ◽  
Joint Displacement

Identification objective functions considering end effector pose errors and branch end distance errors for the calibration of parallel manipulators are discussed. Based on the elimination of the need for fixturing devices, branch end distance error based objectives are demonstrated preferred. Kinematic calibration models that include device geometric parameters, for the RSI 6 degree of freedom hand controller, are introduced. Calibrations considering more complete models are demonstrated to yield improved calibrations in comparison to models considering only original non-zero length and angle parameters and potentiometer parameters. The complete calibration model is found to return error values within a range of the same order of magnitude as branch end distance fluctuation due to joint displacement sensors’ noise. To achieve higher precision, it is concluded that noise-free joint displacement sensing and accurate passive spherical branch end joints are required.

scholarly journals Kinematic Calibration of Industrial Robots Based on Distance Information Using a Hybrid Identification Method

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Guanbin Gao ◽  
Yuan Li ◽  
Fei Liu ◽  
Shichang Han
Keyword(s):  
Industrial Robot ◽  
Kinematic Model ◽  
Error Model ◽  
Industrial Robots ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
Distance Information ◽  
End Effector ◽  
Hybrid Identification ◽  
Identification Method

To improve the positioning accuracy of industrial robots and avoid using the coordinates of the end effector, a novel kinematic calibration method based on the distance information is proposed. The kinematic model of an industrial robot is established. The relationship between the moving distance of the end effector and the kinematic parameters is analyzed. Based on the results of the analysis and the kinematic model of the robot, the error model with displacements as the reference is built, which is linearized for the convenience of the following identification. The singular value decomposition (SVD) is used to eliminate the redundant parameters of the error model. To solve the problem that traditional optimization algorithms are easily affected by data noise in high dimension identification, a novel extended Kalman filter (EKF) and regularized particle filter (RPF) hybrid identification method is presented. EKF is used in the preidentification of the linearized error model. With the preidentification results as the initial parameters, RPF is used to identify the kinematic parameters of the linearized error model. Simulations are carried out to validate the effectiveness of the proposed method, which shows that the method can identify the error of the parameters and after compensation the accuracy of the robot is improved.

A Statically Balanced Gough/Stewart-Type Platform: Conception, Design, and Simulation

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Marco Carricato ◽  
Clément Gosselin
Keyword(s):  
Sufficient Conditions ◽  
Parallel Manipulators ◽  
Point Of View ◽  
Theoretical Point ◽  
Constant Force ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Neutral Equilibrium ◽  
The Difference ◽  
Elastic Elements

Gravity compensation of spatial parallel manipulators is a relatively recent topic of investigation. Perfect balancing has been accomplished, so far, only for parallel mechanisms in which the weight of the moving platform is sustained by legs comprising purely rotational joints. Indeed, balancing of parallel mechanisms with translational actuators, which are among the most common ones, has been traditionally thought possible only by resorting to additional legs containing no prismatic joints between the base and the end-effector. This paper presents the conceptual and mechanical designs of a balanced Gough/Stewart-type manipulator, in which the weight of the platform is entirely sustained by the legs comprising the extensible jacks. By the integrated action of both elastic elements and counterweights, each leg is statically balanced and it generates, at its tip, a constant force contributing to maintaining the end-effector in equilibrium in any admissible configuration. If no elastic elements are used, the resulting manipulator is balanced with respect to the shaking force too. The performance of a study prototype is simulated via a model in both static and dynamic conditions, in order to prove the feasibility of the proposed design. The effects of imperfect balancing, due to the difference between the payload inertial characteristics and the theoretical/nominal ones, are investigated. Under a theoretical point of view, formal and novel derivations are provided of the necessary and sufficient conditions allowing (i) a body arbitrarily rotating in space to rest in neutral equilibrium under the action of general constant-force generators, (ii) a body pivoting about a universal joint and acted upon by a number of zero-free-length springs to exhibit constant potential energy, and (iii) a leg of a Gough/Stewart-type manipulator to operate as a constant-force generator.

Dynamic Calibration for Serial Robotic Manipulators Based on the Zero Position Analysis Method

1989 ◽  
Author(s):  
G. Z. Qian ◽  
K. Kazerounian
Keyword(s):  
Robotic Manipulators ◽  
Calibration Method ◽  
Dynamic Calibration ◽  
Calibration Model ◽  
Kinematic Calibration ◽  
Dynamic Parameters ◽  
Analysis Method ◽  
Kinematic Parameters ◽  
Position Analysis ◽  
Zero Position

Abstract In the continuation of a kinematic calibration method developed in a previous report, a new dynamic calibration model for serial robotic manipulators is presented in this paper. This model is based on the Zero Position Analysis Method. It entails the process of estimating the errors in the robot’s dynamic parameters by assuming that the kinematic parameters are free of errors. The convergence and effectiveness of the model are demonstrated through numerical simulations.

Dynamic Modeling of a Parallel Manipulator With Three Translational Degrees of Freedom

1998 ◽  
Author(s):  
Richard Stamper ◽  
Lung-Wen Tsai
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Close Agreement ◽  
Jacobian Matrix ◽  
Parallel Manipulators ◽  
Kinematic Structure ◽  
End Effector ◽  
Moving Platform ◽  
Euler Approach ◽  
Computationally Intensive

Abstract The dynamics of a parallel manipulator with three translational degrees of freedom are considered. Two models are developed to characterize the dynamics of the manipulator. The first is a traditional Lagrangian based model, and is presented to provide a basis of comparison for the second approach. The second model is based on a simplified Newton-Euler formulation. This method takes advantage of the kinematic structure of this type of parallel manipulator that allows the actuators to be mounted directly on the base. Accordingly, the dynamics of the manipulator is dominated by the mass of the moving platform, end-effector, and payload rather than the mass of the actuators. This paper suggests a new method to approach the dynamics of parallel manipulators that takes advantage of this characteristic. Using this method the forces that define the motion of moving platform are mapped to the actuators using the Jacobian matrix, allowing a simplified Newton-Euler approach to be applied. This second method offers the advantage of characterizing the dynamics of the manipulator nearly as well as the Lagrangian approach while being less computationally intensive. A numerical example is presented to illustrate the close agreement between the two models.

Sign in / Sign up

Export Citation Format

Share Document