The climbing performance analysis of a robot for power line inspection with retractable double serial manipulators

A power line inspection robot has to overcome many kinds of obstacles in inspection processes. The strain clamp is the obstacles difficult for inspection robots to overcome. The inspection robot needs to have a particular climbing ability to overcome the strain clamp. Therefore, the ability to climb power lines is the key point of the inspection robot’s design. An inspection robot with retractable double serial manipulators is proposed to improve the climbing and obstacle-crossing ability. Besides, this paper shows that the inspection robot is more suitable for climbing from static analysis and dynamic evaluation index. Firstly, the obstacle-crossing processes and structures of the inspection robot are introduced. Next, the static analysis is carried out when inspection robot climbs the power lines. The static analysis shows that the new inspection robot has a smaller driving torque. What’s more, the dynamic model of the inspection robot is established by Lagrange’s dynamical equations. By constructing the dynamic evaluation indexes, the inspection robot with retractable arms performs better dynamic characteristics. Finally, a prototype robot is carried out to cross obstacles and climb up power lines. The results show that the inspection robot can overcome different obstacles and has a good climbing performance.

Planar Compliance Realization with Two 3-Joint Serial Manipulators Connected in Parallel

In this paper, the realization of any specified planar compliance with two 3R serial elastic mechanisms is addressed. Using the concepts of dual elastic mechanisms, it is shown that the realization of a compliant behavior with 2 serial mechanisms connected in parallel is equivalent to its realization with a 6-spring fully parallel mechanism. Since the spring axes of a 6-spring parallel mechanism indicate the geometry of a dual 3R serial mechanism, a new synthesis procedure for the realization of a stiffness matrix with a 6-spring parallel mechanism is first developed. Then, this result is extended to a geometric construction-based synthesis procedure for two 3-joint serial mechanisms.

Unified Parameterization and Calibration of Serial, Parallel, and Hybrid Manipulators

In this work, we present methods allowing parallel, hybrid, and serial manipulators to be analyzed, calibrated, and controlled with the same analytical tools. We introduce a general approach to describe any robotic manipulator using established serial-link representations. We use this framework to generate analytical kinematic and calibration Jacobians for general manipulator constructions using null space constraints and extend the methods to hybrid manipulator types with complex geometry. We leverage the analytical Jacobians to develop detailed expressions for post-calibration pose uncertainties that are applied to describe the relationship between data set size and post-calibration uncertainty. We demonstrate the calibration of a hybrid manipulator assembled from high precision calibrated industrial components resulting in 91.1 μm RMS position error and 71.2 μrad RMS rotation error, representing a 46.7% reduction compared to the baseline calibration of assembly offsets.

Manipulator Kinematics and Dynamics On Differentiable Manifolds: Part I Kinematics

Using basic tools of Euclidean space topology and differential geometry, a regular manipulator configuration space comprised of input and output coordinates and conditions that assure existence of both forward and inverse kinematic mappings is shown to be a differentiable manifold, with valuable analytical and computational properties. For effective use of the manifold structure in support of manipulator analysis and control, four categories of manipulator are treated; (1) serial manipulators in which inputs explicitly determine outputs, (2) explicit parallel manipulators in which outputs explicitly determine inputs, (3) implicit manipulators in which explicit input-output relations are not possible, and (4) compound manipulators that require use of mechanism generalized coordinates to characterize input-output relations. Basic results of differential geometry show that differentiable manifolds in each category are naturally partitioned into maximal, disjoint, path connected submanifolds in which the manipulator is singularity free, hence programmable and controllable. Model manipulators in each of the four categories are analyzed to illustrate use of the manifold structure, employing only multivariable calculus and linear algebra. Computational methods for forward and inverse kinematics and construction of ordinary differential equations of manipulator dynamics on differentiable manifolds are presented in part II of the paper, in support of manipulator control.

Analysis of Singular Configuration of Robotic Manipulators

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.

Design and Kinematic Analysis of a Novel 2-DoF Closed-Loop Mechanism for the Actuation of Machining Robots

The essential characteristics of machining robots are their stiffness and their accuracy. For machining tasks, serial robots have many advantages such as large workspace to footprint ratio, but they often lack the stiffness required for accurately milling hard materials. One way to increase the stiffness of serial manipulators is to make their joints using closed-loop or parallel mechanisms instead of using classical prismatic and revolute joints. This increases the accuracy of a manipulator without reducing its workspace. This paper introduces an innovative two degrees of freedom closed-loop mechanism and shows how it can be used to build serial robots featuring both high stiffness and large workspace. The design of this mechanism is described through its geometric and kinematic models. Then, the kinematic performance of the mechanism is analyzed, and a serial arrangement of several such mechanisms is proposed to obtain a potential design of a machining robot.

Kinematic Synthesis and Analysis of the RoboMech Class Parallel Manipulator with Two Grippers

In this paper, methods of kinematic synthesis and analysis of the RoboMech class parallel manipulator (PM) with two grippers (end effectors) are presented. This PM is formed by connecting two output objects (grippers) with a base using two passive and one negative closing kinematic chains (CKCs). A PM with two end effectors can be used for reloading operations of stamped products between two adjacent main technologies in a cold stamping line. Passive CKCs represent two serial manipulators with two degrees of freedom, and negative CKC is a three-joined link with three negative degrees of freedom. A negative CKC imposes three geometric constraints on the movements of the two output objects. Geometric parameters of the negative CKC are determined on the basis of the problems of the Chebyshev and least-square approximations. Problems of positions and analogues of velocities and accelerations of the PM with two end effectors have been solved.

Novel use of the Monte-Carlo methods to visualize singularity configurations in serial manipulators

This paper analyses the problem of the kinematic singularity of 6 DOF serial robots by extending the use of Monte-Carlo numerical methods to visualize singularity configurations. To achieve this goal, first, forward kinematics and D-H parameters have been derived for the manipulator. Second, the derived equations are used to generate and visualize a workspace that gives a good intuition of the motion shape of the manipulator. Third, the Jacobian matrix is computed using graphical methods, aiming to locate positions that cause singularity. Finally, the data obtained are processed in order to visualize the singularity and to design a trajectory free of singularity. MATLAB robotics toolbox, Symbolic toolbox, and curve fitting toolbox are the MATLAB toolboxes used in the calculations. The results of the surface and contour plots of the determinate of the Jacobian matrix behavior lead to design a manipulator’s trajectory free of singularity and show the parameters that affect the manipulator’s singularity and its behavior in the workspace.