In this paper, we propose an omnidirectional jumper with expanded locomotion capabilities. The mechanisms for four functions-jumping, steering, self-righting and take-off angle adjustment-are designed using only two motors to maximize the jumping performance. Jumping uses the modified active triggering mechanism with one motor. Steering shares this motor and uses the wheel touching the ground. The take-off angle is adjusted by changing the angle between the body and the foot using another motor. Self-righting is possible by utilizing combinations of the movements that occur in the energy storing and angle adjustment processes. With these four functions, the robot is capable of jumping in all directions and can jump anywhere in between the maximum height and maximum distance. It can also jump multiple times by self-righting. The robot, with a mass of 64.4 g, jumps up to 113 cm in vertical height, and 170 cm in horizontal distance. This robot can be deployed to explore various environments. Moreover, the design method to implement more functions than the number of motors can be applied to design other small-scale robots.

In this paper, we propose a trajectory-adjustable integrated milli-scale jumping-crawling robot with improved ability to overcome obstacles compared to a robot that can only crawl. The robot employs a novel jumping module with enhanced energy storing-capacity and a height-adjustable active trigger. To increase the energy-storing capacity, latex rubber and knee-like joints are employed to utilize large displacement of the elastic material. The active trigger is based on a single DC motor and can release stored energy at any state, enabling the robot to control the take-off speed of jumping. The jumping module is integrated with the lightweight Dash crawler. The integrated jumping-crawling robot weighs 59.4 g and controls its moving trajectory by adjusting both its crawling speed and its jumping take-off speed.

Jumping locomotion has been widely employed in milliscale mobile robots to help overcome their size limitations by extending their range and enabling them to overcome obstacles. During jumping, the robot's legs experience acceleration that is up to an order of magnitude greater than the gravitational acceleration. This large force results in bending of the jumping legs. In this paper, we study how the bending of the leg affects the jumping performance of a flea-inspired jumping robot. To judge the effect of the leg compliance, the amount of energy lost during jumping is determined by examining the ratio of kinetic energy to input energy, which we define as the mechanical efficiency. The bending leg is dynamically modeled using a pseudo-rigid-body model in order to precisely analyze the energy transfer. Jumping experiments are performed for five different legs, each with a different stiffness. Shape memory polymer rivets, which are lightweight and compact, were used to easily switch out the legs. The mechanical efficiency of the robot with appropriately chosen leg compliance was 41.27% compared with 36.93% for the rigid case and 21.51% for the much more compliant case. The results show that optimizing the compliance of a jumping leg can improve the performance of a jumping robot.

We report on the design, optimization, and performance evaluation of a new wheel-leg hybrid robot. This robot utilizes a novel transformable wheel that combines the advantages of both circular and legged wheels. To minimize the complexity of the design, the transformation process of the wheel is passive, which eliminates the need for additional actuators. A new triggering mechanism is also employed to increase the transformation success rate. To maximize the climbing ability in legged-wheel mode, the design parameters for the transformable wheel and robot are tuned based on behavioral analyses. The performance of our new development is evaluated in terms of stability, energy efficiency, and the maximum height of an obstacle that the robot can climb over. With the new transformable wheel, the robot can climb over an obstacle 3.25 times as tall as its wheel radius, without compromising its driving ability at a speed of 2.4 body lengths/s with a specific resistance of 0.7 on a flat surface.

A small mobile robot that uses round wheels has a stable ride ability on flat surfaces, but the robot cannot climb an obstacle whose height is greater than the length of its wheel radius. As an alternative, legged-wheel robots have been proposed for their better climbing performance. However, such legged-wheel robots have a poor driving performance on flat surfaces since their center of mass is vertically changed. Transformable wheels are used to make the robot drive with round wheels on flat surfaces and climb an obstacle with legged-wheels. However, the design of previously developed transformable wheels is complicated because it needs actuators for the transformation. Thus, it is not suitable for small robots. In this paper, a simple robot platform called Wheel Transformer that uses a new kind of transformable wheel is described. The transformation process is passively operated by an external frictional force, so it does not need any actuators. We fabricate the transformable wheel as well as the robot platform based on analysis of transformation mechanism. The robot can climb an obstacle whose height is 2.6 times greater than its wheel radius.

Origami is the traditional Japanese art of paper folding. Due to its fascinating properties, several attempts are being actively made to expand applications of origami-inspired designs in engineering. This paper presents the design of a deformable wheel based on an origami structure that was integrated with a small-scale mobile robot. The wheel of the robot employs an origami structure proposed by Guest et al. All segments of the structure are connected by links-i.e., folding lines-and this linked structure provides advantages in terms of maintaining geometry and force transmissibility. These two advantages enable control of the shape or size of the wheel by activating a certain portion of the structure. With this property, the wheel diameter of the robot is reduced from 11 cm to 4 cm by four SMA coil spring actuators. Two plate springs are embedded in the wheel to maintain stiffness and allow the wheel to recover from contraction. With the deformable wheel, the robot can pass through a 5 cm gap despite having an 11 cm wheel in its normal state. This deformable wheel concept can be used to build mobile robots that can move quickly with large wheels and move through small gaps when required.

In this paper, we verify the scalability of an underactuated mechanism based on flexural buckling by applying the mechanism to multi-scale adaptive grippers. For verification, we design and fabricate two grippers having different sizes and install the grippers to a manipulator. As a result, the scalability of the mechanism will be shown by grasping from small electronic parts to large wine drinking glasses.

This paper describes a novel rivet fastener made with shape memory polymer (SMP). Shape recovery and modulus change are main two properties of SMPs that enable themselves to be promising base materials for fasteners. The new type of fastener was used to join two composite parts of a meso-scale robot. The fabrication procedure includes macro molding and subsequent laser machining in order to enhance manufacturability, and change size and design on demand. By pull-off experiment it was demonstrated that one single rivet can endure 8N of disengagement force. We applied this fastener to meso-scale flea robot and verified its feasibility.

In gripping devices, adapting to highly unstructured environments such as irregularly shaped objects and surfaces continues to be challenging. To achieve safe and reliable gripping, many researchers have employed various underactuated mechanisms such as differential and compliant mechanisms. All these mechanisms have demonstrated successful gripping performances. They, however, have hardly considered scalability issues of underactuated mechanisms originating from additional force transmissions and onerous mechanism assembly. In this paper, we propose a structurally simple and scalable underactuated mechanism. The mechanism is demonstrated on a gripping device called the “Buckling gripper.” The Buckling gripper achieves adaptive gripping on rugged, uneven, and undulating surfaces typically found in the natural world. The key design principle of the Buckling gripper is inspired by a caterpillar's proleg that highly deforms depending on the shape of the contact surface. This key principle is applied to the gripper via flexural buckling. Normally, buckling is avoided in mechanical designs, but the buckling behavior of a flexure with an adequately selected length provides wide gripping range with a narrow range of force variation, which provides a sufficient number of contacts with even contact forces. As a result, the Buckling gripper achieves adaptive gripping on various surfaces, similar to a caterpillar.

We propose a biomimetic gripper, inspired by a caterpillar's proleg, that can reliably grip dusty and rough terrain. A caterpillar's proleg makes this possible by using a retractor muscle that opens and closes the proleg, and a planta that gives compliance to the proleg. We implement these components with shape memory alloy (SMA) coil actuators and flexure joints. The gripper is fabricated using composite links and flexure joints. This method replaces metal-based joints and links with flexure joints and composite-based rigid links. The composite-based design provides a simple, light weight, and compact structure that enables the gripper to be applied to small-scale robots. Modeling and experiments are used to analyze the gripping force. The results show how the gripping force changes depending on the length of the flexure joint. A prototype was built to demonstrate reliable gripping on a rough-surfaced block using an adaptive mechanism.