Robotic metamorphosis by origami exoskeletons

Changing the inherent physical capabilities of robots by metamorphosis has been a long-standing goal of engineers. However, this task is challenging because of physical constraints in the robot body, each component of which has a defined functionality. To date, self-reconfiguring robots have limitations in their on-site extensibility because of the large scale of today’s unit modules and the complex administration of their coordination, which relies heavily on on-board electronic components. We present an approach to extending and changing the capabilities of a robot by enabling metamorphosis using self-folding origami “exoskeletons.” We show how a cubical magnet “robot” can be remotely moved using a controllable magnetic field and hierarchically develop different morphologies by interfacing with different origami exoskeletons. Activated by heat, each exoskeleton is self-folded from a rectangular sheet, extending the capabilities of the initial robot, such as enabling the manipulation of objects or locomotion on the ground, water, or air. Activated by water, the exoskeletons can be removed and are interchangeable. Thus, the system represents an end-to-end (re)cycle. We also present several robot and exoskeleton designs, devices, and experiments with robot metamorphosis using exoskeletons

Development and applicability of a soft and flexible robotic arm in digestive surgery

Introduction The oncologic adequacy of laparoscopy in digestive surgery is still controversial, especially in some technically demanding operations like Total Mesorectal Excision (TME). Even if standard robotic platforms, i.e. the da Vinci Surgical System, can improve dexterity and manouvrability of surgical instruments, there is no evidence supporting its use in digestive and rectal cancer surgery. The only multi-centre prospective RCT (ROLARR trial) suggests that robotic TME has no advantages compared to laparoscopic TME in terms of clinical and oncologic outcomes. A possible explanation of this lack of real advantages is that the articulation is possible only on the tip of the instrument. The opportunity to have a robotic platform with modular flexibility on the whole length of the arm could overcome technical limitations, improving results and allowing standardization and diffusion of the procedures. Methods The 7FP STIFF FLOP project was financed by the European Commission in order to develop a STIFFness controllable Flexible and Learn-able manipulator for surgical operations. Engineers were inspired by the tentacles of an octopus. A prototype was realized, consisting of multiple soft, pneumatically actuated threechamber segments. Additional chambers are integrated within the segments to allow their stiffening, employing an approach based on the concept of granular jamming. The STIFF-FLOP segments are actuated using pressure regulators and the stiffening chambers are interfaced via valves, applying a vacuum to the granules in the chambers. Sensors are embedded in the STIFF-FLOP modules to measure interaction forces (between the robot and its environment) and the robot’s configuration. A newly developed user interface, based on a Delta robot design, is used to move and position the tip of the STIFF-FLOP arm inside the abdomen. Signals obtained from sensors are fed back to the user interface console providing the operator with force feedback. The entire soft robot is equipped with a 4 mm in diameter centre-free lumen, which allows the passage of the electrical wires needed for the laparoscopic miniaturized optic system positioned at the tip of the robot. Phantom test The prototype was tested in order to assess learnability and satisfaction of the operators. The test was designed as a spatial motion task, consisting of movements between predefined target points clockwise and counter clockwise in a 3D phantom of the abdominal cavity. The participants were asked to conclude the task for the first time with the STIFF-FLOP prototype (SF1), then to repeat the task using conventional laparoscopic instrumentation (LAP) and finally to perform the task once more with the STIFF-FLOP arm (SF2). Surface EMG signals from the forearm muscles were recorded during the test. Results SF1 took a longer time than the other tasks, i.e. 36.4% more than LAP (p=0.0071). However, from SF1 to SF2 there was a 32.1% time reduction (p=0.0232). EMG amplitude analysis showed a higher overall average muscle activity during LAP. Moving from LAP to SF2 there was a 25.9% reduction in average muscle activity (p=0.0128). Cadaver test. The main objective of the test was to validate the compatibility of the system with human anatomy for laparoscopic TME and to determine whether the soft robot could represent a potential improvement compared to standard rigid laparoscopic instrumentation. The study was performed on two cadavers prepared according to the method described by Thiel. Results The use of the STIFF-FLOP camera allowed the surgeon to clearly visualize the inferior mesenteric vessels and the autonomic nerves that were subsequently spared from injury. The ability to smoothly follow the sacral curve due to the flexibility of the manipulator allowed the surgeons to perform a very precise dissection of the posterior part of the mesorectum. The same procedure was performed on both human cadavers, demonstrating the ease of use of the system. Completion times of the procedure were 165 and 145 min, respectively. No intraoperative complications were recorded. No technical failures were registered. Conclusion The STIFF FLOP flexible robotic arm is an intuitive technology that can be easily learned. The prolonged use of the STIFF FLOP manipulator is more comfortable than standard laparoscopic instrumentation and can be used for a long time without exhaustion. The system is compatible with human anatomy and allows to perform a standard surgical abdominal operation. The STIFF FLOP arm seems to improve visualization of the operatory field especially in narrow spaces like the pelvis

Bi-Directional Origami-Inspired SMA Folding Microactuator

We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of 20 µm thickness with memory shapes set to a 180° folding angle. Bi-directional self-folding is achieved by combining two counteracting SMA microactuators. We present a macromodel to describe the engineering stress–strain characteristics of the SMA foil and to perform FEM simulations on the characteristics of self-folding and the corresponding local evolution of phase transformation. Experiments on single-SMA microactuators demonstrate the uni-directional self-folding and tunability of bending angles up to 180°. The finite element simulations qualitatively describe the main features of the observed torque-folding angle characteristics and provide further insights into the angular dependence of the local profiles of the stress and martensite phase fraction. The first antagonistic SMA microactuators reveal bi-directional self-folding in the range of −44° to +40°, which remains well below the predicted limit of ±100°

Quasi-Articulation of a Continuous Robotic Manipulator Enabled by Stiffness-Switching Origami Joints

Soft robots possess a nearly infinite number of kinematic degrees of freedom due to the compliance of their underlying materials which enables them to accomplish incredible feats of movement and adaptation. However, their severely underactuated structures limit their controllability and the degree of precision that can be achieved. As demonstrated by the octopus when fetching prey, it is possible to achieve precise movement in an otherwise “soft” arm by stiffening select sections of the arm while keeping other sections flexible, in effect generating a quasi-articulated structure and reducing the degrees of freedom from practically infinite to a finite number of angles. In this study, we use the bistable generalized Kresling origami to emulate this strategy. Both experimental and computational modeling procedures are conducted to evaluate the bending mechanics of the structure at each of its two stable states (extended and contracted). As the model accurately predicts the major trends observed in experiments, it is used to perform a parametric study on the bending stiffness ratio, defined as the ratio of bending stiffness at the extended state to the bending stiffness at the contracted state. Using the results of the parametric study, we discover that the Kresling design which maximizes the bending stiffness ratio is that possessing the greatest angle ratio λ, the lowest contracted height Lc, and the largest number of sides of the base polygon n, enabling the transformation of the structure from rigid to flexible. To complete the study, we use the optimal Kresling design in the fabrication of a tendon-driven reconfigurable manipulator composed of three Kresling modules. We find that by reconfiguring the Kresling module states (rigid or flexible), the manipulator can effectively transform into 2m different configurations where m corresponds to the number of modules. Through this reconfiguration, the manipulator can generate a quasi-articulated structure which reduces its effective degrees of freedom and enables linkage-like motion. Unlike other methods of stiffness modulation, this solution reduces system complexity by using a bistable structure as both the body of the robot and as a mechanism of stiffness-switching. The structure’s primary reliance on geometry for its properties makes it a scalable solution, which is appealing for minimally invasive surgical applications where both precision and adaptability are vital. The manipulator may also be used as an inspection or exploration robot to access areas that may be inaccessible to humans or rigid robots

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