Study and resolution of singularities for a 6-DOF PUMA manipulator

Abstract

Upon solving the inverse kinematics problem of robot manipulators, the inherent singularity problem should always be considered. When a manipulator is approaching a singular configuration, a certain degree of freedom will be lost such that there are no feasible solutions of the manipulator to move into this singular direction. In this paper, the singularities of a 6-DOF PUMA manipulator are analyzed in detail and all the corresponding singular directions in task space are clearly identified. In order to resolve this singularity problem, an approach denoted Singularity Isolation Plus Compact QP (SICQP) method is proposed. The SICQP method decomposes the work space into achievable and unachievable (i.e., singular) directions. Then, the exactness in the singular directions are released such that extra redundancy is provided to the achievable directions. Finally, the Compact QP method is applied to maintain the exactness in the achievable directions, and to minimize the tracking errors in the singular directions under the condition that feasible joint solutions must be obtained. In the end, some simulation results for PUMA manipulator are given to demonstrate the effectiveness of the SICQP method.

Detection method for the cucumber robotic grasping pose in clutter scenarios via instance segmentation

“…Before 0.85, the Mask AP of Mask RCNN is better than Yolact++ in both datasets, but the Mask AP of Yolact++ is higher than Mask RCNN in high-quality mask area. Taking References [21] and [22] as references, the higher the IoU, the higher the quality of the prediction mask. Thus, the Yolact++ has better performance in predicting masks with higher IoU.…”

Singularity Avoidance for a Redundant Robot Using Fuzzy Motion Planning

“…In the inverse kinematics, the problem is how to find the joint angle when the location of end effector in the task space is given. Some researchers present solving the inverse kinematics problem, such as the null-space methods [1][2], singular value decomposition SVD method [3], singularity-isolation plus compact quadratic SICQP method [4], the new singularity avoidance NSA [5], and the fuzzy inverse kinematic mapping FIKM method [6] to solve the problem. Since the singularities can be decomposed into position singularities and orientation singularities, the NSA method can deal with the position singularities and orientation singularity separately.…”

Solving robotic kinematic problems : singularities and inverse kinematics

“…One of the main drawbacks of this method is the high computational cost associated with the use of the pseudoinverse. In (Cheng et al, 1997), a similar strategy is followed. Once the singular directions have been removed, a combination of a generalized inverse together with an optimization method (the singularity isolation plus QP compact method) is used to generate the motion in the eliminated directions.…”

“…Xu et al (2016) develop an strategy for the identification of the singularities of arbitrary serial robots of 6 DOF. On the other hand, in (Bruyninckx, 2010;Angeles, 2007;Murray et al, 1994;Oetomo, 2004;Cheng et al, 1997Cheng et al, , 1998Oetomo and Lim, 2001;Vaezi et al, 2011;Oetomo and Ang Jr, 2009) a simplification for manipulators with spherical wrist is proposed. Since the origin of the end-effector frame is placed at the wrist center point, a zero block appears in J G :…”

“…In this situation, for a non-null joint velocity vector q, a component of the end-effector velocity vector ẋ is zero and, thus, the corresponding component of the linear or angular velocity vector is zero. Hence, the end-effector of R cannot be translated or rotated around the corresponding axis of the frame in which J G is now represented (Cheng et al, 1998(Cheng et al, , 1997Oetomo and Lim, 2001;Oetomo, 2004;Oetomo and Ang Jr, 2009;Vaezi et al, 2011). There are two main methods for finding out these frames:…”