This paper introduces Model Q-II, an enhanced underactuated robotic hand designed to improve dexterous manipulation through expanded grasping modes and manipulation primitives. The Model Q-II incorporates tripod and enhanced power grasping modes, achieving increased versatility without adding additional actuators. The design employs passive mechanisms, such as lateral contact walls and a finger-locking system, to facilitate seamless transitions between modes, enabling precise pinch-to-tripod and pinch-to-power gating. These enhancements allow the hand to perform complex in-hand manipulations, including multi-directional object positioning. Theoretical analysis, simulations, and experimental evaluations validate the hand's performance, demonstrating improved grasping force, range, and manipulation capabilities. The results highlight Model Q-II's ability to handle various tasks, offering a robust, cost-effective solution for applications requiring both precise and powerful grasping.

A kinematically redundant (6+3)-degree-of-freedom (DOF) hybrid parallel robot with an axisymmetric workspace is proposed. By arranging the first revolute joint of each leg such that they have the same rotation axis, this robot can achieve an axisymmetric workspace, resulting in a large reachable workspace. In addition, type II singularities, which critically limit the orientational workspace, can be fully avoided by utilizing kinematic redundancy. A gripper mechanism is developed to increase the orientational workspace by exploiting the redundant DOFs. Moreover, the orientational workspace can be further increased by controlling one of the redundant DOFs to keep a certain constant angle. As a result, the proposed hybrid parallel robot achieves a high workspace-to-footprint ratio comparable to that of serial robots. A CAD model of the robot and computer animations are provided to demonstrate the large workspaces and the gripper mechanism. A significant advantage of the proposed robot over serial architectures is that the robot is backdrivable since it uses direct-drive or quasi-direct-drive actuators.

A novel kinematically redundant 6+1-degree-of-freedom (dof) spatial hybrid parallel robot is proposed. Each of the two legs of the robot has a fully parallel structure to minimize the moving inertia by mounting actuators on the base. The kinematic model of each leg and overall robot architecture is developed based on the constraint conditions of the robot geometry. The singularity analysis of legs 1 and 2 reveals that their serial and parallel singularities can be avoided by properly dimensioning the robot and sacrificing the edge of the workspace. In addition, it is shown that the type II (parallel) singularities can be completely avoided, resulting in a large orientational workspace. The gripping mechanism is then introduced which is operated by the redundant degree of freedom of the robot. A CAD model of the robot and a computer animation are provided to demonstrate the positioning and orientation of the robot and the gripping function.

In this paper, we propose a new compact variable gravity compensation mechanism (CVGC). The CVGC can be used to generate gravity compensation torque by using the cam and lever mechanism and can also amplify the target gravity compensation torque by varying the pivot point of the lever. The feature of variable gravity compensation is very useful to the mobile platform, which needs to handle unstandardized tasks with a high variation of the workpiece weight. The proposed CVGC has many advantages. Most importantly, it is designed as a compact, independent one-piece structure and is lightweight, meaning it can easily be used as a mobile platform with a simple modification. The CVGC can also have a full range of compensation angle (360°), so it does not restrict any of the original workspaces of the target platform when it is installed. First, the mechanism concept and details are explained. Next, the mechanics of the prototype for force analysis are presented. Based on these mechanics and cam theory, the methodology of the cam profile design is presented. Finally, the performance of variable gravity compensation is verified through experiments that compare the designed and measured gravity compensation torque. The verification test shows adequate performance, as we had hoped, which shows potential for the development of the CVGC.