Exploration of various applications is the frontier of research on inflatable robots. We proposed an articulated robots consisting of multiple pneumatic bladder links connected by rolling contact joints called Hillberry joints. The bladder link is made of a double-layered structure of tarpaulin sheet and polyurethane sheet, which is both airtight and flexible in shape. The integration of the Hilberry joint into an inflatable robot is also a new approach. The rolling contact joint allows wide range of motion of ±150°, the largest among the conventional inflatable joints. Using the proposed mechanism for inflatable robots, we demonstrated moving a 500 g payload with a 3-DoF arm and lifting 3.4 kg and 5 kg payloads with 2-DoF and 1-DoF arms, respectively. We also experimented with a single 3-DoF inflatable leg attached to a dolly to show that the proposed structure worked for legged locomotion.

We propose ThermoCaress, a haptic device to create a stroking sensation on the forearm using pressure force and present thermal feedback simultaneously. In our method, based on the phenomenon of thermal referral, by overlapping a stroke of pressure force, users feel as if the thermal stimulation moves although the position of temperature source is static. We designed the device to be compact and soft, using microblowers and inflatable pouches for presenting pressure force and water for presenting thermal feedback. Our user study showed that the device succeeded in generating thermal referrals and creating a moving thermal illusion. The results also suggested that cold temperature enhance the pleasantness of stroking. Our findings contribute to expanding the potential of thermal haptic devices.

The physical human–robot interaction (pHRI) research field is expected to contribute to competitive and cooperative human–robot tasks that involve force interactions. However, compared with human–human interactions, current pHRI approaches lack tactical considerations. Current approaches do not estimate intentions from human behavior and do not select policies that are appropriate for the opponent’s changing policy. For this reason, we propose a reinforcement learning model that estimates the opponent’s changing policy using time-series observations and expresses the agent’s policy in a common latent space, referring to descriptions of tactics in open-skill sports. We verify the performance of the reinforcement learning agent using two novel physical and competitive environments, push-hand game and air-hockey. From this, we confirm that the latent space works properly for policy information because each latent variable that represents the machine agent’s own policy and that of the opponent affects the behavior of the agent. Two latent variables can clearly express how the agent estimates the opponent’s policy and decides its own policy.

We present the first demonstration of a battery-free untethered wirelessly powered sub-gram jumping robot on an insect-scale. In order to operate the insect-sized robot autonomously, the limitation in battery use emphasizes the need for a wireless power transmission system as an onboard power solution. We designed a wireless power transmission system based on inductive coupling to power the Shape Memory Alloy (SMA), which serves as an elastic energy storage element and actuator for the jumping robot. The assembled mechanical structures, onboard power and electronics yield a 2 mm (high) × 24 mm (long) × 12 mm (wide) robot with ~a weight of 216 mg. The experiments show that our jumping robot wirelessly lift-off up to 5.75 times its body length and repeats the jump around 7 times per minute. To date, out of the several untethered sub-gram insect-scale jumping robots with onboard power, this is the first wirelessly powered robot with the highest jumping performance. The novelty in this work, which addresses the engineering challenges in insect-scale jumping robots, is an untethered wirelessly powered design that achieves dynamic jumping maneuvers, and has self-righting ability.

Despite the recent growth in popularity of personal mobility devices (e.g., e-scooters and e-skateboards), they still suffer from limited safety and narrow design form factors, due to their rigid structures. On the other hand, inflatable interfaces studied in human-computer interaction can achieve large volume change by simple inflation/deflation. Inflatable structure also offers soft and safe interaction owing to material compliance and diverse fabrication methods that lead to a wide range of forms and aesthetics. In this paper, we propose poimo, a new family of POrtable and Inflatable MObility devices, which consists of inflatable frames, inflatable wheels, and inflatable steering mechanisms made of a mass-manufacturable material called drop-stitch fabric. First, we defined the basic material properties of a drop-stitch inflatable structure that is sufficiently strong to carry a person while simultaneously allowing soft deformation and deflation for storage and portability. We then implemented an interactive design system that can scan the user's desired riding posture to generate a customized personal mobility device and can add the user's shape and color preferences. To demonstrate the custom-design capability and mobility, we designed several 3D models using our system and built physical samples for two basic templates: a motorcycle and a wheelchair. Finally, we conducted an online user study to examine the usability of the design system and share lessons learned for further improvements in the design and fabrication of poimo.

We introduce MorphIO, entirely soft sensing and actuation modules for programming by demonstration of soft robots and shape-changing interfaces.MorphIO's hardware consists of a soft pneumatic actuator containing a conductive sponge sensor.This allows both input and output of three-dimensional deformation of a soft material.Leveraging this capability, MorphIO enables a user to record and later playback physical motion of programmable shape-changing materials.In addition, the modular design of MorphIO's unit allows the user to construct various shapes and topologies through magnetic connection.We demonstrate several application scenarios, including tangible character animation, locomotion experiment of a soft robot, and prototyping tools for animated soft objects.Our user study with six participants confirms the benefits of MorphIO, as compared to the existing programming paradigm.

The dolphin kick is a swimming style characterized by undulation of the body. As a platform for swimming research, we have developed a musculoskeletal humanoid robot called Triton. Triton has a flexible spine with erector spinae muscles and a stiffness adjustment system for lumbar joints. The musculoskeletal body includes biarticular and polyarticular muscles, providing multi-joint coordination. The robot is actuated by pneumatic muscles, yielding lightweight and inherently waterproof properties. The compliance of the joints allows interactions between body and fluid similar to those of human swimming. This study presents the design concept of Triton and experimental results from a water tank test. We compare the results with simulation and human movements reported in literature. The results show that the musculoskeletal swimming robot has similar cycle trends in joint angle and thrust force.

Shape changing robot is an approach towards locomotion on uncertain terrain due to its omni-directional features. However, the current locomotion method for such robots rely on discontinuous rolling. We propose a free form locomotion: an omni directional continuous crawling for deformable robots. This method introduce continuous shifting of contact surface similar to amoeba movement. A Mochibot that has thirty two telescopic legs is developed to verify the proposed locomotion method. Through the experiments, we have confirmed that the robot can track smooth paths: straight, smooth, and hand written curves. We also evaluate errors between desired and measured trajectories of the robot.

The integrated fabrication of body structures, actuators, sensors, and electronic circuits into one robot system is an open problem in robotics. Simple and rapid construction of electric actuators in the body through existing approaches is difficult. We take advantage of the liquid-to-gas phase change, and propose an electric phase-change actuator comprising a printable fluidic actuator controlled by an inkjet printed electric heater. The actuator can easily be integrated with origami robots. We theoretically analyze the dynamics of electro-fluidic conversion in the actuator and compare it with actual measurement data. The proposed actuator is verified in real examples of a shape-shifting origami structure and a robot gripper with a printed touch sensor.

Here we report the new soft sensor "FoamSense" that can measure the deformation state of a volumetric soft object such as compressed, bent, twisted and sheared (Figure 1). This sensor is made by impregnating a porous soft object with conductive ink. The design process of FoamSense is explained. We then summarized the features and basic characteristics of some porous materials for designing these sensors appropriately. We also proposed the potential of using digital fabrication for controlling the carrier structure of FoamSense. Proposed porous structure showed an anisotropic sensor characteristic. We discussed the potential and limitation of this approach. Three possible applications are proposed by using FoamSense. FoamSense supports a richer interaction between the user and soft objects.

This study proposes BlowFab, a prototyping method used to create a 2.5-dimensional prototype in a short time by combining laser cutting and blow molding techniques. The user creates adhesive areas and inflatable areas by engraving and cutting multilayered plastic sheets using a laser cutter. These adhesive areas are fused automatically by overlapping two crafted sheets and softening them with a heater. The user can then create hard prototypes by injecting air into the sheets. Objects can be bent in any direction by cutting incisions or engraving a resistant resin. The user can create uneven textures by engraving a pattern with a heat-resistant film. These techniques can be used for prototyping various strong inflatable objects. The finished prototype is strong and can be collapsed readily for storage when not required. In this study, the design process is described using the proposed method. The study also evaluates possible bending mechanisms and texture expression methods along with various usage scenarios and discusses the resolution, strength, and reusability of the prototype developed.

Self-assembling robots can be transported and deployed inexpensively and autonomously in remote and dangerous environments. In this paper, we introduce a novel self-assembling method with a planar pneumatic system. Inflation of pouches translate into shape changes, turning a sheet of composite material into a complex robotic structure. This new method enables a flat origami-based robotic structure to self-fold to desired angles with pressure control. It allows a static joint to become dynamic, self-actuate to reconfigure itself after initial folding. Finally, the folded robot can unfold itself at the end of a robotic application. We believe this new pneumatic approach provides an important toolkit to build more powerful and capable self-assembling robots.

We propose soft planar actuators enhanced by free-form fabrication that are suitable for making everyday objects move. The actuator consists of one or more inflatable pouches with an adhesive back. We have developed a machine for the fabrication of free-from pouches; squares, circles and ribbons are all possible. The deformation of the pouches can provide linear, rotational, and more complicated motion corresponding to the pouch's geometry. We also provide a both manual and programmable control system. In a user study, we organized a hands-on workshop of actuated origami for children. The results show that the combination of the actuator and classic materials can enhance rapid prototyping of animated objects.

We propose a new family of fluidic soft actuators called Pouch Motors. The pouch motors are developed to create printable actuators for enhancing mass-fabrication of robots from sheet materials using easily accessible tools. The pouch motor consists of one or more gas-tight bladders (called pouches) fabricated by heat bonding. We developed two types of actuators from inflatable pouches: the linear pouch motor and the rotational pouch motor. Our theoretical analysis predicts the static force-length and moment-angle relationships of these actuators under pressure control. We compare the theoretical bounds with actual results achieved using several fabricated devices. We developed a fabrication process of pouch motors using a heat stamping technique that allows mass-manufacturing. We also demonstrate three robot bodies with embedded pouch motors: a parallel gripper, a robotic arm with antagonistic actuation, and legged walking robot with a self-contained miniature pneumatic system.

This paper presents a weight-changing device based on the transfer of mass. We chose liquid metal (Ga-In-Tin eutectic) and a bi-directional pump to control the mass that is injected into or removed from a target object. The liquid metal has a density of 6.44g/cm3, which is about six times heavier than water, and is thus suitable for effective mass transfer. We also combine the device with a dynamic volume-changing function to achieve programmable mass and volume at the same time. We explore three potential applications enabled by weight-changing devices: density simulation of different materials, miniature representation of planets with scaled size and mass, and motion control by changing gravity force. This technique opens up a new design space in human-computer interactions.

This works introduces layer jamming as an enabling technology for designing deformable, stiffness-tunable, thin sheet interfaces. Interfaces that exhibit tunable stiffness properties can yield dynamic haptic feedback and shape deformation capabilities. In comparison to the particle jamming, layer jamming allows for constructing thin and lightweight form factors of an interface. We propose five layer structure designs and an approach which composites multiple materials to control the deformability of the interfaces. We also present methods to embed different types of sensing and pneumatic actuation layers on the layer-jamming unit. Through three application prototypes we demonstrate the benefits of using layer jamming in interface design. Finally, we provide a survey of materials that have proven successful for layer jamming.

As domestic robots and smart appliances become increasingly common, they require a simple, universal interface to control their motion. Such an interface must support a simple selection of a connected device, highlight its capabilities and allow for an intuitive manipulation. We propose "exTouch", an embodied spatially-aware approach to touch and control devices through an augmented reality mediated mobile interface. The "exTouch" system extends the users touchscreen interactions into the real world by enabling spatial control over the actuated object. When users touch a device shown in live video on the screen, they can change its position and orientation through multi-touch gestures or by physically moving the screen in relation to the controlled object. We demonstrate that the system can be used for applications such as an omnidirectional vehicle, a drone, and moving furniture for reconfigurable room.

This paper presents PneUI, an enabling technology to build shape-changing interfaces through pneumatically-actuated soft composite materials. The composite materials integrate the capabilities of both input sensing and active shape output. This is enabled by the composites' multi-layer structures with different mechanical or electrical properties. The shape changing states are computationally controllable through pneumatics and pre-defined structure. We explore the design space of PneUI through four applications: height changing tangible phicons, a shape changing mobile, a transformable tablet case and a shape shifting lamp.

Pneumatic actuators have many attributes such as natural compliance and high peak power capabilities that make them attractive for research in dynamic legged locomotion. However, the effects of nonlinear flow through the pneumatic components limit the bandwidth of actuators, thus restricting their use in a high-performance control system. We believe that a model-based control design can overcome these bandwidth limitations. In this study, we demonstrate that black-box system identification of actuator dynamics can be effectively combined with nonlinear trajectory optimization and stabilization to accomplish dynamic tasks on underactuated robots. We present two case studies: an underactuated cart-pole system with the cart driven by a pneumatic actuator and a compass gait walking robot with pneumatic toes.

To gain a synthetic understanding of how the body and nervous system co-create animal locomotion, we propose an investigation into a quadruped musculoskeletal robot with biologically realistic morphology and a nervous system. The muscle configuration and sensory feedback of our robot are compatible with the mono- and bi-articular muscles of a quadruped animal and with its muscle spindles and Golgi tendon organs. The nervous system is designed with a biologically plausible model of the spinobulbar system with no pre-defined gait patterns such that mutual entrainment is dynamically created by exploiting the physics of the body. In computer simulations, we found that designing the body and the nervous system of the robot with the characteristics of biological systems increases information regularities in sensorimotor flows by generating complex and coordinated motor patterns. Furthermore, we found similar results in robot experiments with the generation of various coordinated locomotion patterns created in a self-organized manner. Our results demonstrate that the dynamical interaction between the physics of the body with the neural dynamics can shape behavioral patterns for adaptive locomotion in an autonomous fashion.

Jumping and landing movements are characterized by large instantaneous forces, short duration, and a high uncertainty concerning take off and landing points. Such characteristics make conventional types of control and robot design inadequate. Here we present an approach to realize motor control of jumping and landing which exploits the synergy between control and mechanical structure. Our experimental system is a pneumatically actuated bipedal robot called "Mowgli". Mowgli's artificial musculoskeletal system consists of six McKibben pneumatic muscle actuators including bi-articular muscle and two legs with hip, knee, and ankle joints. Mowgli can reach jump heights of more than 50% of its body height and can land softly. Our results show a proximo-distal sequence of joint extensions during jumping despite simultaneous motor activity. Extensions in the whole body motion are caused by the compliance and the natural dynamics of the legs. In addition to the experiments with the real robot, we also simulated two types of open loop controllers for vertical jumping with disturbance. We found that the model controlled by open loop motor command through a muscle-tendon mechanism could jump robustly. The simulation results demonstrate the contribution of the artificial musculoskeletal system as a physical feedback loop in explosive movements.