Rigid Origami Vertices: Conditions and Forcing Sets

We develop an intrinsic necessary and sufficient condition for single-vertex origami crease patterns to be able to fold rigidly. We classify such patterns in the case where the creases are pre-assigned to be mountains and valleys as well as in the unassigned case. We also illustrate the utility of this result by applying it to the new concept of minimal forcing sets for rigid origami models, which are the smallest collection of creases that, when folded, will force all the other creases to fold in a prescribed way

Towards printable robotics: Origami-inspired planar fabrication of three-dimensional mechanisms

This work presents a technique which allows the application of 2-D fabrication methods to build 3-D robotic systems. The ability to print robots introduces a fast and low-cost fabrication method to modern, real-world robotic applications. To this end, we employ laser-engraved origami patterns to build a new class of robotic systems for mobility and manipulation. Origami is suitable for printable robotics as it uses only a flat sheet as the base structure for building complicated functional shapes, which can be utilized as robot bodies. An arbitrarily complex folding pattern can be used to yield an array of functionalities, in the form of actuated hinges or active spring elements. For actuation, we use compact NiTi coil actuators placed on the body to move parts of the structure on-demand. We demonstrate, as a proof-of-concept case study, the end-to-end fabrication and assembly of a simple mobile robot that can undergo worm-like peristaltic locomotion.United States. Defense Advanced Research Projects Agency (Grant W911NF-08-C-0060)United States. Defense Advanced Research Projects Agency (Grant W911NF-08-1-0228

Developing Design and Analysis Framework for Hybrid Mechanical-Digital Control of Soft Robots: from Mechanics-Based Motion Sequencing to Physical Reservoir Computing

The recent advances in the field of soft robotics have made autonomous soft robots working in unstructured dynamic environments a close reality. These soft robots can potentially collaborate with humans without causing any harm, they can handle fragile objects safely, perform delicate surgeries inside body, etc. In our research we focus on origami based compliant mechanisms, that can be used as soft robotic skeleton. Origami mechanisms are inherently compliant, lightweight, compact, and possess unique mechanical properties such as– multi-stability, nonlinear dynamics, etc. Researchers have shown that multi-stable mechanisms have applications in motion-sequencing applications. Additionally, the nonlinear dynamic properties of origami and other soft, compliant mechanisms are shown to be useful for ‘morphological computation’ in which the body of the robot itself takes part in performing complex computations required for its control. In our research we demonstrate the motion-sequencing capability of multi-stable mechanisms through the example of bistable Kresling origami robot that is capable of peristaltic locomotion. Through careful theoretical analysis and thorough experiments, we show that we can harness multistability embedded in the origami robotic skeleton for generating actuation cycle of a peristaltic-like locomotion gait. The salient feature of this compliant robot is that we need only a single linear actuator to control the total length of the robot, and the snap-through actions generated during this motion autonomously change the individual segment lengths that lead to earthworm-like peristaltic locomotion gait. In effect, the motion-sequencing is hard-coded or embedded in the origami robot skeleton. This approach is expected to reduce the control requirement drastically as the robotic skeleton itself takes part in performing low-level control tasks. The soft robots that work in dynamic environments should be able to sense their surrounding and adapt their behavior autonomously to perform given tasks successfully. Thus, hard-coding a certain behavior as in motion-sequencing is not a viable option anymore. This led us to explore Physical Reservoir Computing (PRC), a computational framework that uses a physical body with nonlinear properties as a ‘dynamic reservoir’ for performing complex computations. The compliant robot ‘trained’ using this framework should be able to sense its surroundings and respond to them autonomously via an extensive network of sensor-actuator network embedded in robotic skeleton. We show for the first time through extensive numerical analysis that origami mechanisms can work as physical reservoirs. We also successfully demonstrate the emulation task using a Miura-ori based reservoir. The results of this work will pave the way for intelligently designed origami-based robots with embodied intelligence. These next generation of soft robots will be able to coordinate and modulate their activities autonomously such as switching locomotion gait and resisting external disturbances while navigating through unstructured environments

Adaptive locomotion of artificial microswimmers

Bacteria can exploit mechanics to display remarkable plasticity in response to locally changing physical and chemical conditions. Compliant structures play a striking role in their taxis behavior, specifically for navigation inside complex and structured environments. Bioinspired mechanisms with rationally designed architectures capable of large, nonlinear deformation present opportunities for introducing autonomy into engineered small-scale devices. This work analyzes the effect of hydrodynamic forces and rheology of local surroundings on swimming at low Reynolds number, identifies the challenges and benefits of utilizing elastohydrodynamic coupling in locomotion, and further develops a suite of machinery for building untethered microrobots with self-regulated mobility. We demonstrate that coupling the structural and magnetic properties of artificial microswimmers with the dynamic properties of the fluid leads to adaptive locomotion in the absence of on-board sensors

The Next-Generation Surgical Robots

The chronicle of surgical robots is short but remarkable. Within 20 years since the regulatory approval of the first surgical robot, more than 3,000 units were installed worldwide, and more than half a million robotic surgical procedures were carried out in the past year alone. The exceptionally high speeds of market penetration and expansion to new surgical areas had raised technical, clinical, and ethical concerns. However, from a technological perspective, surgical robots today are far from perfect, with a list of improvements expected for the next-generation systems. On the other hand, robotic technologies are flourishing at ever-faster paces. Without the inherent conservation and safety requirements in medicine, general robotic research could be substantially more agile and explorative. As a result, various technical innovations in robotics developed in recent years could potentially be grafted into surgical applications and ignite the next major advancement in robotic surgery. In this article, the current generation of surgical robots is reviewed from a technological point of view, including three of possibly the most debated technical topics in surgical robotics: vision, haptics, and accessibility. Further to that, several emerging robotic technologies are highlighted for their potential applications in next-generation robotic surgery

Origami-inspired kinematic morphing surfaces

In the past decades, an emerging technology has tried to build robots from soft materials to mimic living organisms in nature. Despite the flexibility and adaptability offered by such robots, the soft materials introduce very high or even infinite degrees of freedom (DoFs). It is thus challenging to achieve controllable shape changes on soft materials, which are essential for robots to carry out their functions. Many material-based approaches have been attempted to constrain the excessive DoFs of soft materials, so that they can bend, stretch, or twist as desired. In most applications, considering that only limited mobility is required to perform certain tasks, it would also be feasible to employ mechanical coupling to remove unwanted motions. To achieve this, engineers resort to origami techniques to design predictable and controllable robotic structures. However, most origami-inspired robots are built from existing patterns, where the material thickness is always neglected. Using zero-thickness sheets restricts the modelling accuracy, fabrication flexibility, and motion possibility. A recent study reveals that considering material thickness can further reduce the overall DoFs of origami, since its mechanical model is often overconstrained and differs significantly from that of the zero-thickness one. The novel structures with thickness, known as thick-panel origami, were originally developed for space use and are not accessible to roboticists. Hence, a thorough investigation is needed to develop thick-panel origami targeting robotic applications. This thesis is thus centred on two aspects. The first is to systematically design thick-panel origami for shape-changing, namely morphing surfaces. The second part extends selected surfaces into the design of intelligent robots, with the aim of simplified design, actuation, and control. The main achievements of this research are as follows. Firstly, a systematic design methodology is proposed to map thick-panel origami with 6R spatial overconstrained linkages. A library of morphing units whose thicknesses are uniform and not negligible is thus uncovered. Morphing surfaces, which are the tessellations or assemblies of morphing units, are then demonstrated to achieve common soft material behaviours, including bending, expanding, and twisting. Complex motions such as wrapping and curling are also presented. The mobility of these surfaces is restricted to one, while bifurcations may exist for extra motion possibilities. Secondly, a robotic gripper is designed from the wrapping surface. By exploiting the bifurcation and compliance of the surface, the proposed gripper has achieved a balance between motion dexterity and control complexity, aiming to solve the control challenges of grasping and manipulation. More specifically, the gripper can grasp objects of various shapes with one motor and conduct manipulations with only two control inputs, as opposed to many current end effectors that can only grasp or need around 20 actuators for manipulation tasks. On top of this, the gripper can be 3D-printed with ease, largely streamlining the mechanical design and fabrication process. Lastly, a reconfigurable robot is demonstrated on the curling surface to mimic a millipede's morphology. The robot can not only morph into a coil but also reconfigure into wave-like and triangular shapes. The reconfigurability is achieved by utilising the kinematic bifurcations of the surface without increasing the system's overall DoF. The design is also free from module disconnection and reconnection for new configurations, making the system more robust. The proof-of-concept robotic study has showcased the potential of maintaining reconfigurability with a relatively straightforward control strategy