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.

Energy Dissipation during Surface Interaction of an Underactuated Robot for Planetary Exploration

The article summarizes research on essential contributors to energy dissipation in an actuator for an exemplary planetary exploration hopping robot. It was demonstrated that contact dynamics could vary significantly depending on the surface type. As a result, regolith is a significant uncertainty factor to the control loop and plays a significant contribution in the control system development of future planetary exploration robots. The actual prototype of the actuating mechanism was tested on a reference surface and then compared with various surfaces (i.e., Syar, quartz sand, expanded clay, and quartz aggregate) to estimate the dissipation of the energy in the initial phase of hopping. Test outcomes are compared with multibody analysis. The research enhances trajectory planning and adaptive control of future hopping robots by determining three significant types of energy losses in the system and, most importantly, determining energy dissipation coefficients in contact with the various surfaces (i.e., from 4% to 53% depending on the surface type). The actual step-by-step methodology is proposed to analyze energy dissipation aspects for a limited number of runs, as it is a case for space systems.

Kinematics Model Approach to Energy Efficiency in Sustainable Manufacturing

As the energy efficiency is a worldwide topic for sustainability in sustainable manufacturing, the industry ought to undertake the responsibility in a low-energy manner. For energy efficiency, this paper proposed a novel lightweight Non-holonomic Spherical Underactuated Robot (NSUR) with lower energy consumption and fewer actuators than traditional robotics. The kinematics of a robot refers the motion analysis, such as coordinates, velocity, and acceleration. However, current researches always focus on the holonomic full-actuated robot. This paper is devoted to a kind of novel NSUR and its theoretical kinematics analysis model. After NSUR was introduced, the kinematic representation of NSUR was discussed. A pair inverse and forward kinematics analysis of NSUR was put forward in detail. The kinematic analysis of joint of underactuated robot, as the application of NSUR, is applied to explain and verify this methodology. The measurements and comparisons of energy efficiency between NSUR and traditional robotics are also derived in detail.

Nonlinear Control System Design of an Underactuated Robot Based on Operator Theory and Isomorphism Scheme

The number of actuators of an underactuated robot is less than its degree of freedom. In other words, underactuated robots can be designed with fewer actuators than fully actuated ones. Although an underactuated robot is more complex than a fully actuated robot, it has many advantages, such as energy, material, and space saving. Therefore, it has high research value in both control theory and practical applications. Swing-up is a mechanism with two links, which mimics a gymnast performing a horizontal bar movement. Over the past few decades, many sufficiently robust control techniques have been developed for a fully actuated robot but almost none of them can be directly applicable to an underactuated robot system. The reason is that such control techniques require certain assumptions that are valid only for fully actuated robot systems but not for underactuated ones. In this paper, a control system design method for underactuated robots based on operator theory and an isomorphism scheme is first proposed. Bezout identity is designed using isomorphism. The effectiveness of the design method is confirmed by simulation. The simulation results show that the performances, such as robust stability and response time, of an underactuated robot control system are improved.