Atsushi Kakogawa

Mobility of an in-pipe robot with screw drive mechanism inside curved pipes

This paper presents motion analyses and experiments of an in-pipe robot with screw drive mechanism while it moves inside curved pipes. This robot is driven by only one motor and composed of two units. One unit works as a rotator and the another one works as a stator. Screw drive mechanism is a better way to travel inside pipelines of small diameter for inspection, because the area for moving of the robot is narrow and the number of actuators can be reduced (minimum is just one). Therefore, the robot can be smaller and lighter. Furthermore, the control becomes easier. Although many kinds of in-pipe robots with screw drive mechanism have been reported to date, the most important problem of such drive mechanism is the difficulty of traveling in pipes other than straight ones. Examples of such pipes are curved pipes like elbow and bent, branch pipes like a T-shape and the pipe where diameter changes. A concrete analysis has not been done yet. In this paper, we concentrate on a helical driving motion of the robot inside the curved pipe and finally perform experiments to determine the characteristics of it.

Stiffness Design of Springs for a Screw Drive In-Pipe Robot to Pass through Curved Pipes and Vertical Straight Pipes

Various in-pipe robots used for inspection have been developed as a preventive measure against leakage. To expand the use of these robots in small pipelines, high environmental adaptability via a simple structure must be achieved. One solution, using the screw drive mechanism, has been focused on because it requires only one motor. However, the screw drive mechanism cannot achieve complex motion because of its 1-d.o.f. Therefore, existing screw drive in-pipe robots cannot pass through curved pipes with a small curvature radius. To overcome this problem, the kinematic analysis of the screw drive mechanism has been conducted on the basis of the basic principle of helical motion in curved pipes. From the analysis, the relationship among the spring stiffness, motor torque, robot length and static friction on the inner pipe wall is established for the design of stiffness of the supporting springs. The optimal spring stiffness is, thus, derived for the robot to pass through the curved pipe and to climb up in the vertical pipe. The experimental test has been used to verify the validity of the design.

Pathway selection mechanism of a screw drive in-pipe robot in T-branches

Pipelines are important infrastructures in todays society. To avoid leakages in these pipelines, efficient robotic pipe inspections are required, and to this date, various types of in-pipe robots have been developed. Some of them can select their path at a T-branch at the expense of additional actuators. However, fewer actuators are better in terms of size reduction, energy conservation, production cost, and maintenance. To reduce the number of actuators, a screw drive mechanism with only one actuator has been developed for propelling an in-pipe robot through straight pipes and elbow pipes. Based on this screw drive mechanism, in this paper, we develop a novel robot that uses only two motors and can select pathways. The robot has three locomotion modes: screw driving, steering, and rolling modes. These modes enable the robot to navigate not only through straight pipes but also elbow pipes and T-branches. We performed experiments to verify the validity of the proposed mechanism.

Development of a screw drive in-pipe robot for passing through bent and branch pipes

This paper presents a screw drive in-pipe robot for passing through bent and branch pipes. The robot is composed of a front unit (rotator), a rear unit (stator), and a middle unit (pathway selection mechanism). Each unit has elastic arms with a pair of passive wheels. It enables the robot to travel and steer not only in straight pipes but also in bent and branch pipes. In this paper, to clarify the mobility of the screw drive in-pipe robot, experimental verifications in a bent pipe and a T-branch are conducted.

Designing arm length of a screw drive in-pipe robot for climbing vertically positioned bent pipes

This paper presents a method for designing the arm lengths of a screw drive in-pipe robot with a pathway selection mechanism to pass through bent pipes. The robot comprises a front-rotating unit (rotator), middle-steering unit, and rear-supporting unit (stator). Each unit has elastic arms, which can be elongated by springs and can be pushed against the inner wall of the pipe. The robot can travel and steer not only in straight pipes but also in bent pipes and T-branches. When the robot passes through such pipes, its mobility depends on whether the arms can touch the inner wall because the robot will lose the driving force if one of the arms cannot reach the inner wall. This is especially important in vertically positioned pipes, where the robot will fall down if it is unable to reach. In this paper, we focus on the cross-section of the bent pipes, arm length, spring stiffness, and mass of the robot to clarify the mobility of the robot in these types of pipes. A method for determining the initial arm length on the basis of simple quasi-statics is proposed and experimental verification is conducted.

An in-pipe robot with underactuated parallelogram crawler modules.

In this paper, we present a new in-pipe robot with independent underactuated parallelogram crawler modules, which can automatically overcome inner obstacles in the pipes. The parallelogram crawler modules are adopted to maintain the anterior-posterior symmetry of forward and backward movements, and a simple differential mechanism based on a pair of spur gears is installed to provide underactuated mechanisms. A central base unit connects each crawler module through foldable pantograph mechanisms. To verify the basic behavior of this robot, primary experiments in pipes with different diameters and at partial steps were conducted.

Design of a multilink-articulated wheeled inspection robot for winding pipelines: AIRo-II

This paper presents a multilink-articulated robot with omni and hemispherical wheels (AIRo-II) for inspecting and exploring winding pipes. To quickly adapt to winding pipes, holonomic rolling movement without moving forward and backward is more useful. However, this requires the replacement of driving actuators with rolling actuators at the expense of the driving force. In this paper, we investigate the possibility of high maneuverability of multilink-articulated robots in winding pipes by using less actuators and by designing spring joints. We further validate this by experimental verification.

Study on air inflow of a passive suction cup

It is necessary to know the air inflow of suction cup for the designing of a new passive suction cup, which not only could easily attach and detach, but also could keep long adsorption time. This paper proposes a method to calculate the air inflow and its speed, which is easy to implement since it only requires a pressure sensor. Before calculating the air inflow, the factors affecting it should be known. In order to find this factors, experiments are conducted to find the effect of diameter, material, pulled height of displacement of a suction cup and wall condition.

Development of a suction cup with a disc spring

This paper presents a new suction cup with a disc spring for exiting adsorption mechanisms (for example, wall-climbing robots). The center of the suction cup can be pulled up manually through the use of buckling of the disc spring. When deformation of the disc spring reaches a certain balance point, it can sufficiently generate adsorption force. However, with time, the adsorption force will gradually decrease because of air inflow into the suction cup. Then, the spring can be automatically pulled up again to next balance point according to the air inflow. Repeating this process enables the adsorption for a long duration. By pushing back the disc spring to the original position manually, the suction cup is easily detached from the wall. This proposed suction cup can achieve long adsorption, easy attachment and detachment, and energy saving. In this paper, analysis of the adsorption force, design of the suction cup, and experiment of the prototype are conducted.

Design of an underactuated parallelogram crawler module for an in-pipe robot

This paper presents a design method to determine the output ratio of a differential mechanism, which is installed in an in-pipe robot with three underactuated parallelogram crawler modules. The crawler module can automatically shift its shape to a parallelogram when encountering with obstacles. To clarify the requirements for the mechanism, two outputs of each crawler mechanism (torque of the arms and front pulley) are quasi-statically analyzed, and how the environmental and design parameters affect the system are verified.