Systematic object-invariant in-hand manipulation via reconfigurable underactuation: Introducing the RUTH gripper

We introduce a reconfigurable underactuated robot hand able to perform systematic prehensile in-hand manipulations regardless of object size or shape. The hand utilizes a two-degree-of-freedom five-bar linkage as the palm of the gripper, with three three-phalanx underactuated fingers, jointly controlled by a single actuator, connected to the mobile revolute joints of the palm. Three actuators are used in the robot hand system in total, one for controlling the force exerted on objects by the fingers through an underactuated tendon system, and two for changing the configuration of the palm and, thus, the positioning of the fingers. This novel layout allows decoupling grasping and manipulation, facilitating the planning and execution of in-hand manipulation operations. The reconfigurable palm provides the hand with a large grasping versatility, and allows easy computation of a map between task space and joint space for manipulation based on distance-based linkage kinematics. The motion of objects of different sizes and shapes from one pose to another is then straightforward and systematic, provided the objects are kept grasped. This is guaranteed independently and passively by the underactuated fingers using a custom tendon routing method, which allows no tendon length variation when the relative finger base positions change with palm reconfigurations. We analyze the theoretical grasping workspace and grasping and manipulation capability of the hand, present algorithms for computing the manipulation map and in-hand manipulation planning, and evaluate all these experimentally. Numerical and empirical results of several manipulation trajectories with objects of different size and shape clearly demonstrate the viability of the proposed concept.

Optimal Grasping Pose Synthesis in a Constrained Environment

In the last few decades, several approaches have been presented to accomplish tasks with robots or autonomous systems in a glovebox; nevertheless, in nuclear facilities, risky operations are still executed by humans that guarantee a high manipulation capability and dexterity. Inside the gloveboxes, robotic devices have to operate in cluttered environments, or environments with limited space for movement; therefore, it is of significant interest to identify grasping poses that are feasible within such constrained environments. In this paper, we present and experimentally evaluate a strategy to synthesise optimal grasps considering geometric primitives for a manipulation systems in a constrained environment. The novel strategy has been experimentally evaluated in a cluttered environment (as a glovebox mock-up) with realistic objects, and the efficacy of the proposed grasping algorithm is proposed.

A Survey of Single and Multi-UAV Aerial Manipulation

Aerial manipulation has direct application prospects in environment, construction, forestry, agriculture, search, and rescue. It can be used to pick and place objects and hence can be used for transportation of goods. Aerial manipulation can be used to perform operations in environments inaccessible or unsafe for human workers. This paper is a survey of recent research in aerial manipulation. The aerial manipulation research has diverse aspects, which include the designing of aerial manipulation platforms, manipulators, grippers, the control of aerial platform and manipulators, the interaction of aerial manipulator with the environment, through forces and torque. In particular, the review paper presents the survey of the airborne platforms that can be used for aerial manipulation including the new aerial platforms with aerial manipulation capability. We also classified the aerial grippers and aerial manipulators based on their designs and characteristics. The recent contributions regarding the control of the aerial manipulator platform is also discussed. The environment interaction of aerial manipulators is also surveyed which includes, different strategies used for end-effectors interaction with the environment, application of force, application of torque and visual servoing. A recent and growing interest of researchers about the multi-UAV collaborative aerial manipulation was also noticed and hence different strategies for collaborative aerial manipulation are also surveyed, discussed and critically analyzed. Some key challenges regarding outdoor aerial manipulation and energy constraints in aerial manipulation are also discussed.

Motion Pattern Planning of a Quadruped Robot Based on Parallel Kinematics

In this paper, kinematic analysis and motion planning of a quadruped robot are presented by regarding the robot as an equivalent parallel platform-type mechanism with RRRS limb structure. Based on screw theory, the mobility of the quadruped robot with different touchdown legs is analyzed, and proves that the design for degree of freedom (DOF) is available. Base on the established kinematic model of a single leg in terms of POE formula of screw theory, several typical patterns of walking motion planning are implemented and verified by the ADAMS-based simulation. In order to show a good maneuverability and potential manipulation capability of the quadruped robot as a parallel manipulator, the gait planning reflecting two rotating motion patterns (including the rotating motion and walking motion) is modeled and simulated by kinematics of the equivalent parallel manipulators. Finally, a prototype of the quadruped robot has been built. Experimental test shows the practical walking and rotating ability as desired.

Optimal Base Placement and Motion Planning for Mobile Manipulators

A mobile manipulator typically consists of a mobile platform and a robotic manipulator mounted on the platform. The base placement of the platform has a great influence on whether the manipulator can perform a given task. In view of the issue, a new approach to optimize the base placement for a specified task is proposed in this paper. Firstly, the workspace of a redundant manipulator is investigated. The manipulation capability of the redundant manipulator is maximized based on the manipulability index through the joint self-motion of the redundant manipulator. Then the maximum manipulation capability in the specified work point is determined. Next, the relative manipulability index (RMI) is defined for analyzing manipulation capability of the manipulator in its workspace, and the global manipulability map (GMM) is presented based on the above measure. Moreover, the optimal base placement related to the given task is obtained, and the motion planning is implemented by an improved rapidly-exploring random tree (RRT) algorithm with the RMI, which can enhance the manipulation capability from the initial point to the target point. Finally, the feasibility of the proposed algorithm is illustrated with numerical simulations and experiments on the mobile manipulator.

Haptic Control for Minimally Invasive Robotic Surgery

Minimally invasive robotic surgery has been investigated in various surgical application due to high accuracy, fine manipulation capability, tele-operation. Haptic feedback plays a significant role in MIS. In this paper, a dynamics model of a haptic robot is established, and PID algorithm is proposed. To prove the proposed method, an experimental system has been developed. Simulations and experiments show proposed methods is an effective method to master-slave MIRS.

Analysis of the Nanoscale Manipulation Using Near-Field Optical Tweezers Combined with AFM Probe

In recent years, optical manipulators based on forces exerted by enhanced evanescent field close to near-field optical probes have provided the access to nonintrusive manipulation of nanometric particles. However, the manipulation capability is restricted to the intensity enhancement of the probe tip due to low emitting efficiency. Here a near-field optical trapping scheme using the combination of an optical fiber probe and an AFM metallic probe is developed theoretically. Calculations are made to analyze the field distributions including tip interaction and the trapping forces in the near-field region by applying a direct calculation of Maxwell stress tensor using three-dimensional FDTD. The results show that the scheme is able to trap particle at the nanoscale with lower laser intensity than that required by conventional near-field optical tweezers.

Analysis of Influence of Optical Electrode Geometry Effects on Manipulation Using Lateral-Field Optoelectronic Tweezers

The use of photoconductive film improves the flexibility of dielectrophoretic device and the optoelectronic tweezers provides dynamically reconfigurable optical electrode which provides effective technology in the bio-particles parallel manipulation. In this paper, a circle floating electrode and a castellated shape optical electrode are designed in the lateral-field optoelectronic tweezers. The gradient of the square of the electric field is analyzed as the main parameter. The simulation results show that the floating electrode changes the distribution of the electric field and improves the manipulation capability in the region between the strip electrodes. The castellated shape electrode extends the strip electrode and performs the capability of the traditional physical castellated shape electrode. On the same condition the peak value of x direction of the gradient of the square of the electric field is about 15% smaller than the traditional physical electrode mode because the potential decays in the photoconductive film. To obtain the reconfigurable capability, this shortcoming can be overcome by increasing the applied AC signal voltage.