Generally, wheel mechanisms are inferior to a tracked or walking mechanism in terms of step climbability or traversability in rough terrain; however, they are superior in terms of energy efficiency, structural simplicity, and carrying capacity. This paper proposes a new wheel mechanism, the swing-grouser wheel, which can climb high steps (especially in low friction environments) and has high energy efficiency. In addition, the swing-grouser wheel can climb regardless of the body inclination. Its merits are compared to the results of prior studies. Furthermore, the performance of the swing-grouser wheel was confirmed using a real device experiment and a 2D physics simulation, and improved using a full search of the parameters of the swing-grouser wheel. As a result, one improved parameter resulted in climbing at over 68% of the wheel diameter in a low friction environment; additionally, the energy efficiency was better than that of the previous model.

Very long-reach snake-like robotic arms in the range of 14 meters are expected to be used in decommissioning work inside nuclear reactor containers. We developed a tendon-driven system which has the advantage of placing electronic devices protected in the arm's base part which stays out of the reactor container, and only few expensive highly radiation hardened sensors and tools are mounted in the arm tip. Generation of large joint torque is necessary to realize such a very long arm. We applied the concept of coupled tendon-driven mechanism formerly used to generate restricted two dimensional motions, and extended its concept by proposing a new joint arrangement which makes possible three dimensional motions in a large workspace. Mechanical design, compact storage method and derivation of the arm motion control are detailed. Moreover, we built a preliminary mechanical prototype called ”Mini 3D CT-Arm”, and the experimental results demonstrated the validity of the newly proposed concept.

In order to investigate under the sea, various types of underwater robots have been developed. However, most robots can only perform one type of moving such as screw, water gliding or walking, even though there are some creatures which use various types of locomotion in the wild life. Thus, we propose a new type of underwater robot, the “Glide Walker”, which can change its way of locomotion between gliding, walking and swimming depending on the situation. It can be performed by using its two wings with 3 DOFs each and its tail with 1 DOF. This article presents the basic concept, the moving strategy and the mechanical design of the robot in details. Moreover, it also presents the developed prototype, as well as the conducted experiments in which the robot was able to perform the three ways of locomotion successfully. Additionally, it also shows the high manipulation capability and the loop maneuver performance of the robot when in the swimming mode.

In this paper, two types of biologically inspired educational robots based on gliding locomotion are presented. Gliding locomotion utilizes the difference between two orthogonal reaction forces to propel. Since this locomotion principle is very interesting and difficult to intuitively understand, its way of locomotion effectively evokes intellectual curiosity of students. One actuated degree of freedom (DOF) fish-like educational robot and its lecture program are developed for primary, junior high and high school students. And a snake-like educational robot which can connect arbitrary number of units, and its lecture program are developed for university students. We carried out these programs through several lectures. The results are also discussed in this paper.

Power-to-weight ratio of actuators is extremely important for robots, particularly mobile robots. The combination of electric motor and speed reducer, which is the most common driving mechanism for robots, can utilize the motor in the area where its power output is high when the reduction ratio is appropriately designed relative to the load. However, in the case of applications in which the load significantly changes, the motor has to be operated in the area where its power output significantly drops. This problem has restricted the capability of mobile robots, especially biologically inspired robots. Therefore in this paper I focus on a continuously variable transmission (CVT). Crank-type CVTs, which have been used for robotic joints, have the major disadvantage of a limited range of motion due to the dead point of the crank. Thus, this paper proposes the Radial Crank-type CVT (RC-CVT), which overcomes this limit of range of motion by increasing the number of links driving the crank of the CVT. This RC-CVT holds promise as an efficient robotic joint as it can utilize ball screws. This paper shows the equations of kinematics and statics of the RC-CVT and also describes the design and test of the prototype. The application to a quadruped robot is also introduced.

There are many researches about mobile robot with a varied wheel. Mobile robots or mobilities with wheels such like a car or bike have non-holonomic constraint and then it is difficult to move toward wheel's axis direction. Namely, it is impossible to move toward omni-direction due to the constraints by wheel's mechanical structure. Omni-directional movement means the mobility can move toward any direction at anytime. This paper adapted link-driven spherical wheel as an omnidirectional wheel and solved singularity problem caused by mechanical structure of it. We developed omni-directional mobilities( SO(2) and SO(3)) installing link-driven spherical wheels and experimented omni-directional movement with designed controllers.

We propose a new weight compensation mechanism with a non-circular pulley and a spring. We show the basic principle and numerical design method to derive the shape of the non-circular pulley. After demonstration of the weight compensation for an inverted/ordinary pendulum system, we extend the same mechanism to a parallel five-bar linkage system, analyzing the required torques using transposed Jacobian matrices. Finally, we develop a three degree of freedom manipulator with relatively small output actuators and verified that the weight compensation mechanism significantly contributes to decrease static torques to keep the same posture within manipulator's work space.

In this paper, we discuss approximations to continuous curves of the Active Cord Mechanism (ACM) which is composed of arc-shaped joints or double joints. ACM is a machine which is made of a series of bending joints and forms a cord, and it has potential to work in challenging environment due to its large degree of freedom. In prior research most of ACM were composed of straight links and joints, and a lot of successful control methods for them have been proposed. However, the control of the ACM that is composed of arc-shaped joints or double joints has not been studied sufficiently so far. In this research we propose the method of approximations to continuous curves for such kind of ACM and use it for the control. The proposed idea is verified by numerical calculations and experiments by a robot.

This paper describes a development of a light duty arm with an active-fingertip gripper for handling discoid objects. The system is potentially capable of sharing the workspace with human workers, assuming the use in a cell manufacturing system. We propose a new 3-DOF gripper mechanism with two fingers which symmetrically move in parallel and each finger has a 2-DOF fingertip of a cylindrical shape. We also develop a lightweight arm with a weight compensation mechanism which is composed of a non-circular pulley and a spring to minimize required actuator torque. After verification of basic performance, the hand-arm system successfully performs a pick-and-place task for a discoid object from horizontal placement to vertical placement and vice versa. We demonstrate continuous 100 times pick-and-place operations without failure where its cycle time almost equals to a human worker.

This paper discusses the design of a new snake-like robot without wheels, named ACM-R7. It has 18 DOFs, is 1.6 m in length and weighs 11.7 kg. It features a water-tight structure, a large motion range pitch joint of ±90 degree and a high output-power actuator arrangement, based on the coupled drive concept. Furthermore the control method “Loop Gait” is discussed. For this gait the ACM-R7 forms a loop shape and rolls like a wheel on the rim. We introduce the “Serpenoid Oval” for the loop shape. It s formed by a smooth sinusoidal angular motion of the joints. Moreover we consider the modification of the “Serpenoid Oval” for steering and obstacle avoidance. The performance is then verified by several motion experiments.

A snake-like robot has an advantage in moving into a narrow space. Particularly “pedal wave”, which is one of its locomotion styles, is suitable for entering a thin path. However, pedal wave have been used only for going straight in most of the prior studies. In particular horizontal steering of pedal wave by a real robot has not been investigated sufficiently. Therefore in this paper we studied a kinematically appropriate steering method of pedal wave using a continuous snake-like robot model. We proposed steering by superposition of a steering curvatures and a pedal wave's curvature, and investigated the condition of suitable steering curvature using kinematic simulations. The proposed steering method was verified by experiments with a real snake-like robot.

Now that mobile robots are getting tested more and more in challenging areas, difficulties in control, particularly when the robot cannot be seen, have appeared. In this research a mobile snake robot with actuated wheels is given the ability to sense its surroundings through its wheels by 3DOF force sensors, so that semi-autonomous control can be realized. This will simplify necessary operator commands and improve situation awareness through information feedback. Even with the many limitations of practical robot design, such as unwanted flexibilities, and measuring while actuating the wheels, the sensor's errors are confirmed to vary between just 1% and 3%. Moreover, sensitivity is equal over the wheels, only a 3s calibration at startup is needed, and the sensor is shown to be resistant to aging and temperature change. The sensor is implemented directly into a new snake robot, one sensor in each segment. Its central control will adjust the snake body according to the surroundings while automatically avoiding obstacles and crossing gaps.

The Active Cord Mechanism (ACM) such as a snake-like robot is suitable for tasks in a narrow environment because of its slender body, but mechanical models developed in prior research were somewhat large for practical usage. In this paper, we propose a new 2-dof joint mechanism for the small ACM. A usual joint mechanism has the same number of rotational axes as that of the actuators, but the proposed mechanism has 4 rotation axes against 2 actuators. This joint mechanism has relatively large range of motion and it can improve the capability of ACM in a narrow environment. We verified the specification of the proposed mechanism and the result showed that it is suitable for the small ACM. In addition, we developed the ACM with the proposed joint mechanism, and it realized a sidewinding motion, which is a kind of snakes' locomotion style. We think this result shows that the proposed mechanism will contribute to the study of the small ACM.

In this paper, we discuss about stabilization of the head of a snake-like robot. In prior research snake-like robots usually shook the head during undulating motion. However, a snake-like robot is usually equipped with a camera on the head, so the swing of the head is problem. To solve this problem, we propose a control method to stabilize the head of an undulating snake-like robot. In the proposed method, the motion of the neck is controlled to cancel the undulation of the body in order to stabilize the head. In this study, first we derived the formulas for this method, and confirmed the effectiveness by simulation. Then we implemented that control on a real snake-like robot and showed the availability of the proposed method.

Snake-like robots and hyper-redundant manipulators have been called active cord mechanism (ACM), and they have been one of fields of robotics. However, general study on the spatial shape of ACM has not been conducted enough so far. In this paper, we propose a effective method for analysis of the 3D shape of ideal continuous ACM models. In addition, we show some important characteristics of ACM using this method. The results help us understand the characteristics and possibility of ACM