Singularity analysis and treatment for a 7R 6-DOF painting robot with non-spherical wrist

Wang, Xuhao; Zhang, Dawei; Zhao, Chen; Zhang, Huiyue; Yan, Hongle

doi:10.1016/j.mechmachtheory.2018.03.018

Cited by 29 publications

(12 citation statements)

References 20 publications

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“…Huang et al [11] classify methods for mitigating the adverse effects of singularities into (1) damped least-squares regularization of the robot Jacobian [12,13,14], which encompasses tracking eigenvalues to set the regularization coefficient [15,16], (2) null-space control of redundant manipulators [17,18,19,20], and (3) interpolation of joint angles between inverse-kinematic solutions on each side of the singularity. Chembuly and Vorganti (2017) [21] control a redundant planar robot without the eigenvalue decomposition in the null-space methods.…”

Section: Prior Methodsmentioning

confidence: 99%

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Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Milenkovic

2021

Robotica

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An unexpected path reversal is discovered for a serial robot with an offset-axis wrist over a finite range of proximity to the wrist singularity. This is replicated by a kinematic model. A prior spherical-wrist method transits the singularity with limited joint rate and acceleration under a constant rate of tool traversal. Accurate position is maintained by controlling a small deviation in orientation. Extensions to the method for an offset wrist (1) find the least-maximum deviation, (2) identify and locate where a path reversal occurs, and (3) use this point to control step size in a high-order predictor-correction path following procedure.

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Section: Prior Methodsmentioning

confidence: 99%

“…Meeting these objectives for an offset wrist motivates the current study. Furthermore, the singularities of the robot arm are readily avoided by staying within reach of the arm and away from the overhead position [17]. This justifies concentrating on wrist effects.…”

Section: Prior Methodsmentioning

confidence: 99%

Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Milenkovic

2021

Robotica

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“…It means that there is a zero platform twist for non zero actuated joint velocities [25]. In other words, for a given non-null velocity, the platform remains immobile, i.e.,q represents the non empty null space of the singular matrix J q [26]. For the present study case the parallel robot is inverse singularity free due to the fact that J q matrix is an identity matrix, see Equation (10).…”

Section: Inverse Singularitymentioning

confidence: 99%

Maximal Singularity-Free Orientation Subregions Associated with Initial Parallel Manipulator Configuration

Garcia¹,

Campos²

2018

Robotics

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Reduced workspace is the main parallel robot disadvantage. It is generally due to the robot configuration, mainly the platform orientation constraint, the present work intends to find the maximum sphere within the orientation workspace, i.e., the singularity-free orientation regions. These regions are related to the platform orientation through Roll-Pitch-Yaw angles. Therefore, an optimization genetic algorithm is used to determine the initial platform orientation corresponding to the largest sphere volume. In this algorithm, the geometrical parameters and the direct and inverse singularities are the optimization constraints. The geometrical constraints may be studied using vectorial analysis. The reciprocity property from screw theory is implemented to analyze the direct and inverse kinematic. In this work it is used a methodology to verify the singularity closeness measure associated with direct kinematic. This measure is related to the rate of work done by each leg upon the platform twist. To determine how close is the parallel robot to a direct singularity a index value is proposed. It is considered that the passive joints reachable regions may be limited by a cone, whereby the cone symmetric axis is the same than the passive joint axis. In the optimization problem, the sphere volume, i.e., the maximal angular displacement of the moving platform around any axis is the objective function. Thus, the genetic algorithm individuals explore all feasible regions looking for an optimal solution.

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“…However, the method identified singular regions rather than specific singular configurations. In [23], the singularity of a 6-DOF painting robot with a non-spherical wrist was decomposed into position singularity and attitude singularity by introducing a virtual wrist center. Due to the virtual wrist center, the D-H parameters d i of the 7R 6-DOF manipulator changed, so an error was introduced to the position of the EE.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Singular Configuration of Robotic Manipulators

et al. 2021

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Robotic manipulators inevitably encounter singular configurations in the process of movement, which seriously affects their performance. Therefore, the identification of singular configurations is extremely important. However, serial manipulators that do not meet the Pieper criterion cannot obtain singular configurations through analytical methods. A joint angle parameterization method, used to obtain singular configurations, is here creatively proposed. First, an analytical method based on the Jacobian determinant and the proposed method were utilized to obtain their respective singular configurations of the Stanford manipulator. The singular configurations obtained through the two methods were consistent, which suggests that the proposed method can obtain singular configurations correctly. Then, the proposed method was applied to a seven-degree-of-freedom (7-DOF) serial manipulator and a planar 5R parallel manipulator. Finally, the correctness of the singular configurations of the 7-DOF serial manipulator was verified through the shape of the end-effector velocity ellipsoid, the value of the determinant, the value of the condition number, and the value of the manipulability measure. The correctness of singular configurations of the planar 5R parallel manipulator was verified through the value of the determinant, the value of the condition number, and the value of the manipulability measure.

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Singularity analysis and treatment for a 7R 6-DOF painting robot with non-spherical wrist

Cited by 29 publications

References 20 publications

Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Maximal Singularity-Free Orientation Subregions Associated with Initial Parallel Manipulator Configuration

Analysis of Singular Configuration of Robotic Manipulators

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