Robotic manipulators capable of regulating both compliance and stiffness offer enhanced operational safety and versatility. Here, we introduce Worm Gear-based Adaptive Variable Elasticity (WAVE), a variable stiffness actuator (VSA) that integrates a non-backdrivable worm gear. By decoupling the driving motor from external forces using this gear, WAVE enables precise force transmission to the joint, while absorbing positional discrepancies through compliance. WAVE is protected from excessive loads by converting impact forces into elastic energy stored in a spring. In addition, the actuator achieves continuous joint stiffness modulation by changing the spring’s precompression length. We demonstrate these capabilities, experimentally validate the proposed stiffness model, show that motor loads approach zero at rest–even under external loading–and present applications using a manipulator with WAVE. This outcome showcases the successful decoupling of external forces. The protective attributes of this actuator allow for extended operation in contact-intensive tasks, and for robust robotic applications in challenging environments.

A support structure for flexible displays such as OLED or flexible LEDs was developed using the flexible omnidirectional driving gear mechanism. It is a gear mechanism having two degrees of freedom on one surface. This flexible display mechanism is expected to be placed inside a car dashboard as a human interface and for workspace optimization. In this study, we propose a novel flexible omnidirectional driving gear for supporting flexible displays discussing its design, motion range, repeatability, positional accuracy, and adaptability to any guide surface through magnetic coupling. The experiments showed satisfactory results for positional accuracy and repeatability with adaptability over a wide range of curvatures.

A gripper mechanism using flexible double-rack finger actuated using differential worm gear mechanism that can change its finger length according to the object being grasped was developed. Thermoplastic polyurethane (TPU) based fingers were soft, impact resistant, highly compliant, and were able to conform to the contour of the objects when grasping. The fingers can extend, contract and bend in 2D space when driven by the differential worm gear mechanism. A normal worm and an inner worm gear was used to actuate the flexible double-rack fingers. The relative motions between the two worm gears resulted in different motions of the finger. Multiple fingered configuration of the gripper can be driven from the same mechanism actuated using two actuators. A mathematical model was developed to describe the kinematics of the finger for positioning experiments. Experiments were also conducted to measure the fingertip force for different lengths of the finger. Grasping experiments of two and three-finger gripper were performed to test the grasping performance of the gripper for objects of different size, shape and weight. The gripper successfully grasped objects of different sizes by adjusting the finger length and conforming to the shape of the objects.

This paper introduces an innovation of the Spherical Omnidirectional Wheel, designed to achieve omnidirectional driving motion. In previous models, the supporting shaft was placed at the center of the mechanism. However, achieving both smoothness and high load-capacity in such designs proved challenging. The mechanism proposed in this study features an offset design, enabling outer support for the wheel. A prototype was developed and its basic motion was experimentally validated.

This article presents an active ball joint mechanism (ABENICS) enhanced by interactions of spherical gears. The gear-based joint drives three rotational degrees of freedom (RDoF) without slippage. The capabilities were inspired by the unique interactions between two different innovative gears [the cross spherical gear (CS-gear) and monopole gear (MP-gear)] and the superimposition of those interactions by the CS-gear's quadrature spherical tooth structure. One MP-gear constrains two of the three RDoF of the CS-gear. The driving module which drives the MP-gear converts this “constraint” into a “drive” and drives the CS-gear with two RDoF. The CS-gear orthogonally superimposes the interactions caused by two MP-gears to achieve three RDoF driving forces. The principle was revealed by analyzing an equivalent linkage modeled on the mechanism of ABENICS. The linkage also led to the kinematics and torque equations. The theory and physical characteristics of ABENICS were verified in comprehensive and continuous positioning experiments on manufactured prototypes. The flexibility of the actuator placement was also verified in different configurations of the driving modules. The active ball joint, ABENICS can transmit high torque and reliable positioning in three RDoF without an orientation sensor, which applies to robot joints and orientation control mechanisms.

In this research, omnidirectional crawler unit with the torus configuration is proposed. It is composed of two curved crawler belts whose inner and outer trajectories have the same length. The prototype is designed and developed. The basic motion of the prototype is confirmed experimentally.

We have been studying an omnidirectional driving gear mechanism that can generate thrusting force in an arbitrary direction on one surface, which may be flat or curved. This omnidirectional gear is driven by spur gears that are perpendicular. When one spur gear rotates to drive the omnidirectional gear, the other slides between the teeth of the omnidirectional gear and vice versa. In this paper, we introduce gears with passive rollers to reduce the frictional resistance with a mechanism including smooth rolling motion of conical or flat passive rollers, which can boost the power transmission efficiency of the omnidirectional driving gear system. We also confirmed another useful function of this gear with passive rollers as a worm wheel to transmit power from a worm gear with higher energy efficiency than an ordinary worm wheel.

This video shows multiple omnidirectional driving gears to realize smaller size and weight than the ordinary X-Y stages. The examinations of different materials and sizes of the gear teeth to improve the performances of the omnidirectional driving gears are the main progress of this paper from our previous reports [1].

The finger mechanism equiped with omnidirectional driving roller is shown. The omnidirectional driving roller has two active rotational axes at the touching point. The finger mechanism with this roller can manipulate the grasped object with any arbitrary directional axes. Prototype model has been developed and basic motion of the finger has been confirmed though the experiments.

In this paper, the principles and the actual configurations of the omnidirectional driving gear mechanism that was implemented by the authors were described. The validity of the proposed structure was also confirmed and its basic characteristics understood through experiments using the actual prototypes.

As ordinary dual-axis driving mechanisms in X-Y directions, for example, commercially available X-Y stages with ball screws are familiar. However, such driving mechanisms have two stages, namely both upper and lower linear actuators, the latter of which must generate sufficient thrust to carry large weights, including that of the upper actuator mechanism, which has hampered efforts to achieve suitably fast and smooth driving motion due to the inertial force effect. It is also difficult to achieve a small and slimline driving mechanism with such overlapping two-stage structure. In these ordinary two-stage driving mechanisms, the motion of the X-Y stage can be disturbed by the wires of the upper actuator. In this research, we have considered the abovementioned problems, and propose a new omnidirectional driving gear mechanism that enhances its driving area from the normal X-Y plane to convex and concave curved surfaces respectively, and even various combinations of both. The smoothness of basic omnidirectional motion and effectiveness of the driving method of this proposed omnidirectional driving gear mechanism have been confirmed with several experiments involving our setups.

In this paper, additional manipulating function for limited narrow space with omnidirectional driving gear was described. The validity and advantage of the proposed function was also confirmed through experiments using the actual prototype of the planar omnidirectional driving gear units for the parallel gripper.

It is well known that parallel mechanisms have several advantages, namely high power, rapidity and high stiffness. However, their workspace is limited due to interference of each chain. In our previous work, to expand the workspace of Delta mechanisms, ball bearings were employed instead of ball joints. Although this allowed a relatively wide workspace to be achieved, the clearance gap of the ball bearings introduced undesirable flexibility, while mechanical limitations persisted. In this paper, to tackle these problems, a novel parallel mechanism with wire-pulleys is proposed. The basic structure of the new mechanism is the same as that of the conventional Delta mechanism, but wire-pulleys are employed instead of a parallel four-bar mechanism. The key feature of the wire-pulleys is its lack of mechanical limitations. A prototype has been designed and developed, which achieves a wider workspace and reduced backlash. In addition, the total parts quantity has declined by more than 25%. Fundamental experiments show its potential.

This paper describes a combination mechanism of a wheeground a paddle to realize an effective movement on the border of ground and water. For the conventional mobile mechanisms on water or on ground the combination of the mechanism to the body of the robot separately, and each one can be the interruption to the other in each field. In this research, we propose a hybrid mechanism of a wheeground a paddle as drive mechanism itself to realize an effective movement on the border such as a coast with debris after a disaster like a seismic sea wave or a tanker grounding accident. A prototype robot has been built and basic experiments on its motion have been conducted.

This paper describes linear load-sensitive continuously variable transmission with the spherical driving unit. This CVT mechanism consists of spherical drive, drive axis, motor housing, fixed bracket and linear sliding plate. It changes the reduction ratio continuously by inclination angle of active rotational axis. Additionally, this linear mechanism has a load-sensitive function by changing inclination of active rotational axis in response to the load. We have developed a linear load-sensitive continuously variable transmission and confirmed the effectiveness of the proposed mechanism.

This paper describes various configurations of two connected unit crawlers. By changing the relative position of the two connected vehicle units, the overall robot comprising such a mechanism can automatically adapt to surface obstacles on the field, including complicated structures such as disaster-generated debris. In addition, we analyzed the effect of axis arrangements in order to simplify the realization of the switching function so as to achieve the four basic configurations.

In this paper, a new category of the wheel-leg hybrid robot is presented. The proposed mechanism can compose large wheel diameter compared with the previous hybrid robot to realize a greater ability to climb obstacles. A prototype model of one Wheel-Leg module of the proposed robot mechanism has been developed to illustrate the concept. Actual design and mode changing experiment with a test mechanical module is also presented. Basic movement tests and a test of the basic properties of the rotational fingertip are also shown. The Basic configurations of wheel-leg retractable is considered well. The integrated mode is also described.

A spherical mobile robot has been developed with a 1-DOF mechanism that can generate two motions, translational and rotational, using only one motor. The basic concept is to attach vinyl strips to the sphere at regular intervals and to change the driving modes of the motor to produce the desired motion. For example, placing the motor in vibration mode causes the trajectory of the contact point between the sphere and ground to follow a specified closed path, such as an elliptical path, which makes the sphere rotate against the ground. Testing of this concept using a self-developed simulator confirmed that rotational motion is generated by the interactions between the surface attachments and the ground. On the basis of these results, a prototype spherical mobile robot was developed, and testing confirmed that switching the motor driving mode generated two different motions.

In this video, a novel tracked mechanism for sideways motion is presented. The tracked mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional tracked mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink. Motion experiments, with a test vehicle are also presented.

In this paper, a tetrahedral mobile robot with central axis for transformation to the flat vehicle is presented. The throwable robot with the function of going into narrow spaces when its in the flat-vehicle mode is explained in detail. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: mode changing function and omnidirectional motion. Basic Motion experiments, with a test vehicle are also presented.

In this paper, the basic running performance of the cylindrical tracked vehicle with sideways mobility is presented. The crawler mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional crawler mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype. Basic motion experiments with confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink.

In this research, we developed a sphere-shaped mobile robot that can generate multiple behaviors by using only one motor. The robot can generate the translational motion and the rotational motion by controlling the motion of the motor. The motor itself acts as an eccentric weight during motions. To generate emergent behaviors, many protrusions are mounted on the surface of the spherical body. The emergent behaviors occur by an interaction between the external world and these protrusions when the sphere is vibrating, and the robot can move in a random walk manner.

In this paper, a novel crawler mechanism for sideways motion is presented. The crawler mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional crawler mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink. Motion experiments, with a test vehicle are also presented.

In this paper, mechanical design of a novel spherical wheel shape for a omni-directional mobile robot is presented. The wheel is used in a omnidirectional mobile robot realizing high step-climbing capability with its hemispherical wheel. Conventional Omniwheels can realize omnidirectional motion, however they have a poor step overcoming ability due to the sub-wheel small size. The proposed desing solves this drawback by means of a 4 wheeled design. “Omni-Ball” is formed by two passive rotational hemispherical wheels and one active rotational axis. An actual prototype model has been developed to illustrate the concept and to perform preliminary motion experiments, through which the basic performance of the Omnidirectional vechicle with this proposed Omni-Ball mechanism was confirmed. An prototype has been developed to illustrate the concept. Motion experiments, with a test vehicle are also presented.

The paper focuses on design and joint impedance control of a new teleoperated robot arm enabling torque measurement in each joint by means of incorporation of devised optical torque sensors. When the contact of arm with an object occurs, joint impedance algorithm provides active compliance of corresponding robot arm joint. Thus, the whole structure of the manipulator can safely interact with unstructured environment. In the paper, we describe detailed design procedure of the 4-DOF robot arm and optical torque sensors. To extract force signal from measured data, the gravity compensation algorithm was elaborated and verified. The experimental results of joint impedance control show that proposed strategy provides safe interaction of entire structure of robot arm with human beings and ensures the collision avoidance.

This paper introduces a pervasive sensor system for nursing homes, where daily activities of elderly persons are monitored by pervasive sensors all the time. Deterioration in the quality of nursing care for the elderly has become one of the biggest problems in the aging society and the authors have been challenging the problem by sensors embedded in a nursing room. The sensors accumulate position information of a subject person and his wheelchair, then it is utilized for prompt assists for the subject and also used for obtaining his life log. In our experiments, we obtained position data of an elderly person for a month and a half and analyzed his sleeping hours and the number of times of going to a restroom. This paper presents the concept of the system, overview of the current system and experimental results obtained

"VmaxCarrier2" is an omni-directional mobile robot with step-climbing capability, which can be used as a compact, quiet, and durable transportation vehicle in cluttered and cramped environments. In this study ,we discuss the step-climbing sequence of this omni-directional mobile robot with step-climbing capability. In addition that, we show some motions on steps and slope of this vehicle.

We developed a robotic arm for a master-slave system to support "mutual telexistence," which realizes remote dexterous manipulation tasks and close physical communication with other people using gestures. In this paper, we describe the specifications of the experimental setup of the master-slave arm to demonstrate the feasibility of the mutual telexistence concept. We developed the master arm of a telexistence robot for interpersonal communication. The last degree of the 7-degree-of-freedom slave arm is resolved by placing a small orientation sensor on the operators arm. This master arm is made light and impedance control is applied in order to grant the operator as much freedom of movement as possible. For this development stage, we compared three control methods and confirmed that the impedance control method is the most appropriate to this system.

"VmaxCarrier2" is an omni-directional mobile robot with step-climbing capability, which can be used as a compact, quiet, and durable transportation vehicle in cluttered and cramped environments. We have already developed several kinds of omni-directional mobile robots for situations where it is desirable to be able to move in all directions, such as "VUTON" and "VmaxCarrier". To construct an omni-directional mobile robot with a greatly improved capability to climb steps, we developed the Omni-Disc2, a bent pneumatic actuator, and a pneumatic system. These novel components were constructed into a prototype, and through evaluation experiments we have confirmed the improved step climbing capability of VmaxCarrier2.