Takafumi Haji

Prototype “RT04” that uses flexible mono-tread mobile track

It is expected that robotics is introduced into search and rescue activity, planetary explorer and investigation in extreme environment etc. The robots in such environment need high mobility against extremely rough terrain. Pressure exerted on the terrain is distributing wider, thus tracked vehicles are advantageous, accordingly. Since it is difficult for usual tracked vehicle composed of a pair of tracks to change length/width ratio a lot from 1/1 because of its turning property, serially connected tracked vehicles and paddled tracked vehicles have been introduced in order to improve the mobility. We have proposed a tracked vehicle called flexible mono-tread mobile track (FMT). The body of FMT except both side wall is completely wrapped around only by a track belt, which is possible to prevents sharp or thin edges of obstacle and cloth from penetrating. However the prototypes have rail colliding and derailing problems of the track belt caused by flexion and surface profile of the ground. The objective of the paper is, therefore, to develop a new prototype of FMT called RT04. RT04 adopts one degree of freedom rotational joint in stead of the flexible components and accurately designed guide rail system in order to prevent the belt from colliding or derailing. Rubber sponge grouser is also introduced against obstacle penetration and impact from the ground. Finally, some experimental tests validate the prototype.

Mobility and Operability of Flexible Mono-Tread Mobile Track (FMT)

In the paper, we show mobility and operability of flexible mono-tread mobile track (FMT) through experiments. For mobility, FMT can climb over a thin plate, recover from lying position on its side, and side wind. As a result, it is partly proven that FMT has enough ability for the complex environment. For operability, FMT is better than a differential type track vehicle in the case that vehicle traces to gentle curves. Since the both mechanism have advantages and disadvantages such that the differential type track can turn in smaller radius, it is useful that we choose better one to adapt various situations.

A proposal of flexible mono-tread mobile track — a new mobile mechanism using one track and spine-like structure —

In the past decade, search robots in rescue operations have been focused on and developed for the purpose of finding survivors trapped in the rubble of collapsed buildings. Most of them adopt serpentine mechanisms: they comprise of track-equipped segments that are connected by joints to obtain greater mobility in extremely complex environments. However, they might gather to catch debris between tracks or become stuck due to the mechanisms, in addition, increasing the number of segments would result in gaining weight and complicated mechanism and control system. In this paper, a new mobile mechanism: flexible mono-tread mobile track is proposed and a prototype ldquoRescue mobile track No.2 (RT-02) WORMYrdquo is developed. The vehicle is composed of a ldquoflexible chainrdquo and a spine-like structure. It is examined on mobility performance in irregular environments.

Experiment of maneuverability of flexible mono‐tread mobile track and differential‐type tracked vehicle

Purpose – The purpose of this paper is to compare the maneuverability of flexible mono‐tread mobile track (FMT) and usual differential‐type tracked vehicle (DTV) through some experiments. A new mobile mechanism: FMT has been proposed which is employing “flexible chain” and vertebral structure, thereby the body flexes in 3D. As a result of the specific turning mechanism, steering performance of FMT is different from that of DTV. Hence, maneuverability of FMT and DTV would be different.Design/methodology/approach – The vehicles are maneuvered to trace two types of lines: a semi‐circle and right‐angled line segments by four operators. The distance and the displacement of direction of the vehicles from the target line are measured. The maneuverability was discussed based on the experimental results for FMT and DTV.Findings – Some of the characteristic features on maneuverability of FMT and DTV have been made clear.Originality/value – FMT is a new mobile mechanism for tracked‐vehicle and the maneuverability of...

Flexible Mono-tread Mobile Track (FMT) - A New Mobile Mechanism Using One Track and Vertebral Structure -

In the past decade, search type rescue robots have been focused on. Most robots took “linked mobile track” type such as snakes, so as to obtain high quality against unknown irregular surfaces. However the linked mobile track has some joints and sometimes they shut in some debris and stuck on it. In addition, many links increase total weight of robots and control complexity. In the paper, we propose a new type mobile mechanism, Flexible Mono-Tread Mobile Track (FMT) and develop a prototype called “Rescue mobile Track No.2 (RT02) WORMY”. The prototype consists of a flexible chain and a vertebrae like structure. Moreover, we investigate its performance against the irregular surfaces.

Measurement System for Flexed Shape of Flexibly Articulated Mobile Track

This paper proposes and validates a system for measuring the flexed posture of the flexible mono-tread mobile track (FMT) using a flexible displacement sensor (FDS). The FMT proposed previously has a single track and vertebral structure. The flexed posture of the FMT determines its turning radius and direction; thus, knowing its posture is important. However, it is impossible to measure the shape of flexible mobile systems using sensors located internally, such as a rotary potentiometer, or located externally, such as a laser scanner. To solve the problem, we introduce the FDS to measure the flexed FMT shape. The sensor consists of two fixed electrodes, a sliding electrode, and a nylon string coated with carbon (NSCC). It works as a flexible potentiometer by moving the sliding electrode along the NSCC while maintaining electrical contact. The measurement system is implemented in a prototype of the FMT called RT02-WORMY and is validated in a series of experiments.

Development of Flexible Mono-Tread Mobile Track Using Rotational Joints

Robot technology is expected to become applicable to missions on rough terrain, such as search and rescue activities, planetary exploration, and environmental investigations. The robots in such environments need high mobility against extremely rough terrain. Tracked vehicles are effective against rough terrain because the contact pressure of the vehicle can be distributed more widely. However, it is difficult for a typical tracked vehicle composed of a pair of tracks to significantly change its length/width ratio from 1:1 because of its turning property. To improve mobility, serpentine tracked robots are designed to move on rough terrain. We proposed a flexible mono-tread mobile track (FMT). An FMT is a mono-track system, and its body has a vertebral structure composed of rigid segments (called vertebrae) connected by flexible segments (called intervertebral disks). An FMT can flex more widely in three dimensions, thereby turning and climbing over obstacles. This feature is an advantage over previous mono-track systems. Prototypes of FMTs called RT02-WORMY and RT03-LIPAN have been developed and validated the system’s mobility. The body of an FMT, except for both sidewalls, is completely surrounded by only a track belt. However, the prototypes have a problem with interference and derailing in the track belt that is caused by flexion and the surface profile of the ground. The objective of this study, therefore, is to develop a new prototype of an FMT called RT04-NAGA. NAGA adopts a combination of one-degree-of-freedom (DoF) rotational joints instead of flexible components and an accurately designed guide rail system to prevent the belt from interfering with operation or derailing. To validate the performance of the prototype, we conducted the fundamental tests of the prototype, such as energy consumption; mobility with a ditch, a vertical wall, a stairway and a spiral stairway; and the standard tests following the regulations of the National Institute of Standards and Technology (NIST).

Steerability of articulated multi-tracked vehicles by flexed posture moving on slippery surface

Serpentine tracked robots -i. e., articulated multi-tracked vehicles -are designed to move on rough terrains and used for a variety of purposes, including search and rescue operations, planetary exploration and environmental investigations. The steerability of such vehicles depends on its posture and interaction between the vehicle and the ground. In previous research, kinematic models with slip information were derived for articulated multi-tracked vehicles. Such kinematic models, however, do not allow for the slippage of the vehicle that occurs when moving at a high speed or on a slippery surface. In this paper, we derive a dynamic model on which the frictional force is acting between the track shoes of each track of the vehicle and the ground for the slippery conditions. The frictional model neglecting static friction is given by a formula for the friction coefficient function proposed in the field of Teramechanics in order to mainly analyze slip behavior. The model is also used to analyze the steering properties, or steerability of the vehicles.

LAYERED BODY FOR FLEXIBLE MONO-TREAD MOBILE TRACK

Robot technology is expected to become applicable to missions on rough terrain, such as rescue activities, environmental investigations, and planetary exploration. Tracked vehicles are effective against such environments because the contact pressure of the vehicle can be distributed more widely. In order to improve mobility, new mechanisms such as a serpentine-type tracked vehicle have been proposed. We previously proposed the flexible mono-tread mobile track (FMT). The first prototype called WORMY has a mechanical problem, i.e., track belt interference and derailing, when it moves flexing. This paper proposes and validates a new design strategy of the FMT adopting layered structure of its body. The layered structure reduces space between vertebrae, which can solve the derailing problem. A new prototype adopted the layered structure is developed in order to validate its mobility. We also evaluate effectiveness of passive retro-flexion against obstacles.

Measurement of flexed posture for Flexible Mono-tread mobile Track using new flexible displacement sensor

We have proposed Flexible Mono-tread mobile Track (FMT) as a mobile mechanism for hazardous environment such as disaster area. FMT has only one track which can flex in three dimension. Generally speaking, one has to teleoperate robots under invisible condition. In order to operate the robots skillfully, it is necessary to detect not only condition around the robots and its position but also posture of the robots at any time. Flexed posture of FMT decides turning radius and direction, it is very important to know its posture, accordingly. FMT has a vertebral structure composed of vertebrae as rigid body and intervertebral disks made by flexible devices such as rubber cylinder and spring. Since the intervertebral disks flex in three dimension, it is not easy for traditional sensors such as potentiometers, rotary encoders and range finders to measure its deformation. The purpose of the paper, therefore, is to measure flexed posture of FMT using a new flexible displacement sensor. We prove that the flexed posture of FMT with five intervertebral disks can be detected through experiment.