Comparison of Hip Torque and Radial Forcing Effects on Locomotion Stability and Energetics

Hip torque and radial forcing along the leg are two common actuation methods for legged robots. However, hip torque and radial forcing have not been compared as potential alternative strategies of actuation. The respective advantages and disadvantages of hip torque and radial forcing are not well known. In this paper, we compare hip torque and radial forcing actuation through the simulation of two models: a Rotary-forced Spring-Loaded Inverted Pendulum and a Radially Forced Spring-Loaded Inverted Pendulum. Both actuation methods can produce fully asymptotically stable locomotion. Interestingly, it is found that they improve locomotion stability in different ways: hip torque first destabilizes locomotion when initially introduced but greatly stabilizes locomotion when it keeps increasing; radial forcing always stabilizes locomotion, but in a moderate way.

Control Strategy and Trajectory Planning for Reconfiguration of a vA Based Metamorphic Parallel Manipulator

Mechanisms with reconfigurability have become a trend in development of multi-functional robots which can adapt to unexpected environments and perform complicated tasks. This paper presents a novel metamorphic parallel manipulator with the ability to change its mobility through the phase change of a variable-axis (vA) joint integrated in each limb. The platform has 6 DOFs in the source phase and can reconfigure its mobility to 5, 4 and 3 resorting to redundant actuation. This leads to reconfigurability and multi-functionality of the parallel manipulator characterized by the mobility configuration variation. A control strategy and a trajectory planning algorithm for reconfiguring the mobility configuration of the manipulator are proposed and simulations are carried out to identify a proper way of reconfiguration.

The Gear Bearing Drive: A Novel Compact Actuator for Robotic Joints

Advanced robotics requires a new generation of actuators able to exhibit a number of desirable characteristics ranging from high power density and high efficiency, high positioning resolution, high torque capacity and torsional stiffness, lightweight designs and low-cost packages. In this paper, we present the development and the experimental evaluation of a new actuator, aimed at improving the torque density and mechanical efficiency of actuated robotic joints, and enhancing the portability and effectiveness of robotic systems engaged in biomechanical applications such as rehabilitation robots and wearable exoskeletons. The new actuator, called the Gear Bearing Drive (GBD), consists of a two-stage planetary gear arrangement coupled through the planets and driven by an external rotor brushless motor that is inscribed within the input stage sun gear. This planetary configuration enables for incredible high-speed reductions and allows for embedding the motor directly within the gearbox saving significant space on the actuator length. Our initial experimental prototypes have demonstrated impressive performance with the potential to deliver more than 30Nm of continuous torque with 85% mechanical efficiency and 0.0005 degree of backlash, and up to 200 rpm maximum output speed in a highly compact and robust package.

Reconstructing David Huffman’s Origami Tessellations

David A. Huffman (1925–1999) is best known in computer science for his work in information theory, particularly Huffman codes, and best known in origami as a pioneer of curved-crease folding. But during his early paper folding in the 1970s, he designed and folded over a hundred different straight-crease origami tessellations. Unlike most origami tessellations designed in the past twenty years, Huffman’s straight-crease tessellations are mostly three-dimensional, rigidly foldable, and have no locking mechanism. In collaboration with Huffman’s family, our goal is to document all of his designs by reverse-engineering his models into the corresponding crease patterns, or in some cases, matching his models with his sketches of crease patterns. Here we describe several of Huffman’s origami tessellations that are most interesting historically, mathematically, and artistically.

Accommodating Thickness in Origami-Based Deployable Arrays

The purpose of this work is to create deployment systems with a large ratio of stowed-to-deployed diameter. Deployment from a compact form to a final flat state can be achieved through origami-inspired folding of panels. There are many models capable of this motion when folded in a material with negligible thickness; however, when the application requires the folding of thick, rigid panels, attention must be paid to the effect of material thickness not only on the final folded state, but also during the folding motion (i.e., the panels must not be required to flex to attain the final folded form). The objective is to develop new methods for deployment from a compact folded form to a large circular array (or other final form). This paper describes a mathematical model for modifying the pattern to accommodate material thickness in the context of the design, modeling, and testing of a deployable system inspired by an origami six-sided flasher model. The model is demonstrated in hardware as a 1/20th scale prototype of a deployable solar array for space applications. The resulting prototype has a ratio of stowed-to-deployed diameter of 9.2 (or 1.25 m deployed outer diameter to 0.136 m stowed outer diameter).

Structure Design, Kinematics and Grasp Constraint of a Metamorphic Robotic Hand for Meat Deboning Operation

A four-fingered metamorphic robotic hand with a reconfigurable palm is presented in this paper with the application in deboning operation of meat industry. This robotic hand has a reconfigurable palm that generates changeable topology and augments dexterity and versatility for the hand. Mechanical structure and design of the robotic hand are presented and based on mechanism decomposition, kinematics of the metamorphic hand is investigated with closed-form solutions leading to the workspace characterization of the robotic hand. Based on the kinematics of the four-fingered metamorphic hand, utilizing product-of-exponentials formula, grasp map and grasp constraint of the hand are then formulated revealing the grasp robustness and manipulability performed by the metamorphic hand. A prototype of the four-fingered metamorphic hand is consequently fabricated and integrated with low level control and sensor systems leading to a scenario of applying the hand in the field of meat industry for deboning operation.

Development and Analysis of a New Specialized Gripper Mechanism for Garment Handling

This paper reports ongoing work on the design of a new gripper for garments handling. The development of this device is part of the CloPeMa European Project creating a robot system for automated manipulation of clothing and other textile items. First, we analyze the specificity of the application determining the requirements for the design and functioning of the grasping system. Textiles do not have a stable shape and cannot be manipulated on the basis of a priori geometric knowledge. The necessary exploration of the material and the environment is performed with the help of tactile sensors embedded in the fingertips of the gripper, complementing the vision system of the robotic work cell. The chosen design solution is a simple mechanism able to perform adequately the grasping task and to permit exploratory finger motions. The kinematics and statics of the mechanism are outlined briefly and, in accord with initial experiments, used to validate the design.

Force-Position Hybrid Control of a New Parallel Hexapod Robot for Drilling Holes on Fuselage Surface

In this paper, a new kind of 6-legged robot for drilling holes on the aircraft surface is presented. Each leg of the robot is a parallel mechanism with 3 degree of freedoms thus the robot includes totally 18 motors. Due to different work status, the control modes of these motors are also different and thus the force-position hybrid control method is applied. The kinematic and dynamic model is briefly introduced. Then the robot gait is discussed. After that hybrid control method is introduced: first the control mode of each motor should be determined, then the position or force control curves should be calculated. In the end of this paper, both virtual and real prototype of this robot is showed and the experiment result showed that the hybrid control method can significantly improve the robot performance.

Multi-Field Responsive Origami Structures: Preliminary Modeling and Experiments

The use of origami principles to create 3-dimensional shapes has the potential to revolutionize active material structures and compliant mechanisms. Active origami structures can be applied to a broad range of areas such as reconfigurable aircraft and deployable space structures as well as instruments for minimally invasive surgery. Our current research is focused on dielectric elastomer (DE) and magneto active elastomer (MAE) materials to create multi-field responsive structures. Such multi-field responsive structures will integrate the DE and MAE materials to enable active structures that fold/unfold in different ways in response to electric and/or magnetic field. They can also unfold either as a result of eliminating the applied field or in response to the application of an opposite field. This concept is demonstrated in a folding cube shape and induced locomotion in the MAE material. Two finite element models are developed for both the DE and MAE materials and validated through physical testing of these materials. The models are then integrated to demonstrate multi-field responses of a bi-fold multi-field responsive structure. The bifold model is designed to fold about one axis in an electric field and a perpendicular axis in a magnetic field. Future modeling efforts and research directions are also discussed based on these preliminary results.