Owing to their tremendous adaptability to free-form objects, soft grippers with fin-ray structure have a wide range of applications. However, kinetostatics analysis and contact sensing for such soft grippers are quite a challenge due to large structural deformations. In this article, a model-based method for intrinsic contact sensing, object perception, and interactive manipulation, is proposed for this kind of adaptive grippers. The contributions arise from the integration of compact strain-gauge sensors, that are particularly fabricated for slender flexible beams undergoing large deformations. Using a discretization-based approach, the contact condition can be identified efficiently in light of the local deformations gathered via the deflection sensors. Prototypes are developed using simple materials and manufacturing methods, on which various validation experiments are conducted. Owing to the contact sensing capability, the developed adaptive fin-ray gripper is able to perceive the boundary geometry and structural compliance of unstructured objects. Moreover, sensor-based feed-back control can be accomplished to perform interactive manipulation, in which the contact force between the finger and object can be regulated precisely (around$5\,\%$RMS error) in real-time.

This paper presents an alternative decomposition of spatial stiffness matrices based on the concept of compliant axes. According to the congruence transformation of spatial stiffness, the coordinate-invariant aspects, which are referred to as the central principal components of the 6 × 6 symmetric positive semidefinite matrices, can be derived uniquely. The proposed decomposition is free from the eigenvalue problems of the 6 × 6 stiffness matrices so that both Plücker's ray and axis coordinates can be utilized to characterize the elastic system's force-deflection behavior. Hence, an arbitrary spatial stiffness matrix can be uniquely decomposed into two sets of orthogonal spring wrenches with finite and infinite pitches, respectively. The decomposed wrenches with finite pitches correspond to the stiffness' wrench-compliant axes, along which linear deformations produce only wrenches parallel to them. As a result, three torsional and three screw springs are required, at the most, to realize a given spatial stiffness. Using the principal axes decomposition, some physical appreciations, such as the center of stiffness, the wrench-compliant axes, and the correspondence of compliance and stiffness, can be derived to reveal the inherent structure of spatial stiffness in an intuitive manner. In order to verify the effectiveness of the proposed method, two numerical examples are intensively studied with comparison to the eigenscrew decomposition. In addition, a potential application of the proposed stiffness decomposition method is also provided for the structural compliance modeling of flexible links in robot manipulators.

This paper presents an analytical approach to determine and eliminate the redundant model parameters in serial-robot kinematic calibration based on the product of exponentials formula. According to the transformation principle of the Lie algebra se(3) between different frames, the connection between the joints' twist errors and the links' geometric ones is established. Identifiability analysis shows that the redundant errors are simply equivalent to the commutative elements of the robot's joint twists. Using the Lie bracket operation of se(3), a linear partitioning operator can be constructed to analytically separate the identifiable parameters from the system error vector. Then, error models satisfying the completeness, minimality, and model continuity requirements can be obtained for any serial robot with all combinations and configurations of revolute and prismatic joints. The conventional conclusion that the maximum number of independent parameters is 4r + 2p + 6 in a generic serial robot with r revolute and p prismatic joints is verified. Using the quotient manifold of the Lie group SE(3), the links' geometric errors and the joints' offset errors can be integrated as a whole, such that all these errors can be identified simultaneously. To verify the effectiveness of the proposed method, calibration simulations and experiments are conducted on an industrial six-degree-of-freedom (DoF) serial robot.

This paper investigates new wavelet-based multiresolution modeling techniques in CAD. MRA techniques are extended to detail feature transplanting and detail feature copying from previous MRA editing including sweep editing, fractional editing, synthesis editing and detail blending. Two new editing methods called detail feature transplanting and detail feature copying are added to previous sweep editing, fractional editing, synthesis editing and detail blending. Detail feature transplanting editing is a way to transplant detail features of a curve/surface to another curve/surface. Detail feature copying editing is a way to copy or move detail features on the same curve/surface.