This paper presents the development of a remotely operated brachytherapy system for oral cancer. The purpose of the system is to reduce exposure dose to the operator by keeping him or her at a distance of 1m from radioactive198Au sources. The system is designed to enable the operator to perform the same procedure as for conventional brachytherapy treatment without exposure dose. It consists of an applicator manipulator to implant198Au seeds, a finger device to firmly grasp organs in the mouth, operational parts for both of them, and a base arm. The applicator manipulator and finger device are fixed on the base arm which is fixed on a radiation shield. The applicator manipulator is a serial manipulator with five degrees of freedom (DOF). The finger device is necessary because organs in the mouth are soft and flexible. Its finger and operational parts are identical three DOF parallel manipulators. This paper details preliminary experiments of grasping and insertion with the system. These experiments verify that an operator can grasp a tongue model with the finger device and can insert the applicator into it with the applicator manipulator. In our developed system, we also confirm that rotation of the applicator needle can reduce insertion force.

In laparoscopic surgery large instruments cannot be used because they cannot pass through trocars which are typically smaller than 12mm in diameter. For example, retracting an internal organ with a slender instrument is often a difficult task. To remove this limitation, we have proposed “assemblable instruments”, that is, parts are inserted through trocars and assembled inside the abdominal cavity to become a large instrument and we have developed assemblable hands. However they use two trocars for assembling, which require positioning and alignment of two assembled parts. This paper presents a simple three fingered hand whose function is limited to retracting. We propose a much simpler assembling method “single trocar assembling” for the hand. Experimental results verify that the hand can be assembled easily and that it can withstand a force of 25N enough to rectract a pancreas.

This paper presents a lightweight 328 g anthropomorphic robot hand that can exert a large grasp force. We propose a combination mechanism of a flexion-drive and a force-magnification-drive for a cable driven multifingered robot hand. The flexion-drive consisting of a feed screw enables quick motion of its fingers and the force-magnification-drive consisting of an eccentric cam, a bearing and a pulley enables a firm grasp. This paper also proposes a three-dimensional linkage for the thumb. This linkage consists of four links and is driven by a feed screw. It can oppose to a large force exerted by the other fingers with the force-magnification-drive. These mechanisms are compact enough to be installed in the developed lightweight hand. We experimentally verify that the maximum fingertip force of the hand exceeds 20 N and that the thumb can hold a large force of 100 N. The time to fully close the hand by using the flexion-drives is 0.47 s. After the fingers make contact with an object, the time to achieve a firm grasp by using the grasp-magnification-drive is approximately 1 s.

This paper presents Tokyo-TECH 100 N Hand, a three-fingered eight-degree of freedom hand that can generate a large grasp force of 100N. All fingers are 90 mm in length and the weight of the hand is 941 g. The hand can generate a large grasp force with a force-magnification mechanism whereas all joints can perform a high speed motion of over 200 deg/s with a high-speed driving mechanism. The high-speed driving mechanism consists of a feed screw and nut with a low reduction ratio. We propose a simple and small three-dimensional toggle mechanism for the force-magnification mechanism. The toggle mechanism thrusts the feed screw and nut of the high-speed driving mechanism when the finger is in contact with an object. It can maintain a large grasp force without energy consumption. We experimentally verify the force and speed performances.

This paper proposes an assemblable hand that can be inserted through trocars for robotic hand assisted laparoscopic surgery (HALS). When it is difficult to perform surgery using only slender laparoscopic surgery instruments, surgeons often apply HALS, which makes an incision about 7-8 cm through which their hand is inserted. This is invasive compared with complete laparoscopic surgery. We proposed robotic HALS to replace a human hand with a robotic hand. We previously developed a three-fingered five-degree of freedom assemblable hand. It is challenging to an assemblable hand with more degrees of freedom (DOF) that can be assembled with a simple assembly procedure. This paper presents an assemblable hand with three fingers and nine degrees of freedom-the 3f9d-hand. Its power transmission mechanisms and assembly procedure are completely different from those of our previous 3f5d-hand. The new hand consists of center, right, and left finger units. The center finger unit connects the operational part at its end and the right and left finger units connect to the operational part outside the abdominal cavity. This facilitates assembly and improves safety, which is a significant improvement compared with the previous hand. Although the hand has no wrist joint, its three finger joints play the role of a wrist joint. A preliminary experiment with a plastic model verified that the proposed assembly procedure was feasible and the hand was easily assembled and disassembled.

In laparoscopic surgery, surgeons perform surgery in the abdominal cavity by using only slender instruments that can be inserted through small diameter trocars. When it is difficult to perform surgery by using only instruments for laparoscopic surgery, they often make a 7–8 cm incision through which their hand can be inserted. Clearly this is invasive compared with complete laparoscopic surgery. This paper proposes an assemblable mechanical hand like a human hand that can be inserted through trocars. We already developed a three-fingered three-degree of freedom assemblable hand. The purpose of this paper is to develop an assemblable hand with more degrees of freedom that can grasp/push aside large internal organs and open membranes. The developed hand has three fingers with a total of five degrees of freedom. Its power transmission mechanisms and assembling method are completely different from those of the previous hand. The hand is assembled from body and finger units with an installation tool. The finger unit is fixed to the body unit with only one screw by using the installation tool. To drive the fingers, power is transmitted with cables, gears and shafts. Experimental results verify that the hand can be assembled in a closed space and that it can grasp and push aside various objects.

We have proposed a novel concept of assemblable instruments for laparoscopic surgery, that is, their parts can be disassembled to pass through trocars and can be reassembled inside the abdominal cavity to become large instruments. By applying this concept, this paper proposes an assemblable pursestring suture instrument (PSI). In gastrectomy, a purse string suture on the esophagus is made preparatory to the anastomosis of the esophagus and the small intestine with a circular stapler. A traditional PSI cannot pass through a trocar because of its T-shaped jaws and a PSI that can be used in laparoscopic surgery is highly desired, which motivates us to develop the assemblable PSI. We have developed two prototypes of the assemblable PSI. The experiment with the first prototype verifies that it can be assembled in the abdominal cavity. However it cannot generate a grip force enough to hold the esophagus. We propose a two-DOF unfolding linkage mechanism for the gripper of the second prototype. The in vivo experiment with the second prototype verifies that it can make a satisfactory purse string suture.

This paper proposes a force magnifying mechanism for a parallel jaw gripper that can exert a large grasp force. A parallel jaw gripper requires speed when opening and closing its jaws, and force when grasping an object. The proposed force magnifying mechanism consists of a slider, feed screws, gears, a lever, etc. It runs sequentially with only one DC-motor. Basically the motor rotates a feed screw to move its output jaw quickly to an object with a gear. When the output jaw makes contact with an object, the gear is loosened from a stopper and starts to move axially along the feed screw. Then it pushes a lever, which generates a large fingertip force. We have developed an 86g gripper with this mechanism and experimentally verified that it can grasp objects of various sizes with a large grasp force over 200N. It is also experimentally verified that the gripper can grasp and ungrasp an object reliably over 4500 times if machine lubricant is properly supplied.

In laparoscopic surgery, surgeons can use only rod-shaped instruments that can be inserted through a trocar and therefore high technique is required. To overcome this problem, much work has been done to develop multi-degree-of-freedom forceps. However they are still inadequate to grasp, manipulate or push aside large internal organs, like a spleen, pancreas, and liver. This paper proposes mechanical hands with detachable fingers that can be assembled in the abdominal cavity, each of whose parts can be inserted through a trocar. Two types of such three-fingered hands are developed. The three fingers of one are dependently driven and those of the other are independently driven. For each hand, we show fixing and power transmission mechanisms. Power of each hand is transmitted from operator's hand to its fingers by connecting wires with a ball and socket. Experimental results verify that both hands can grasp large and oily objects like internal organs. One goal of this study is to develop simple hands that can be used as a retractor. The other goal is to develop skillful hands that can replace surgeons' hands in hand assisted laparoscopic surgery which is still invasive by making a 7-8cm incision to insert a human hand into the abdominal cavity.

This paper presents a 99 g finger joint that can exert a very strong fingertip force of more than 100 N. We have shown that a simple five-bar linkage can be used as a load-sensitive continuously variable transmission (CVT) for a finger joint. The maximum fingertip force of our previous finger was limited by the mechanical strength of its links and bearings, not by the power of its DC motor. If the machine strength can be improved, a much greater fingertip force can be expected. To design a lightweight CVT with sufficient mechanical strength, we analyze the internal force of the CVT and select light plain bearings. We also analyze the stress by using the finite element method and select the materials of its links. Experimental results verify that the maximum fingertip force is more than 100 N near the singular configuration of the CVT and the maximum angular velocity is more than 550 deg/s. These motions are impossible without the CVT. We also developed a very light shape memory alloy brake of 0.56 g. The CVT with the brake can hold a fingertip force of more than 100 N not only near the singular configuration. The electric energy consumed by the brake is much less than that by the DC motor

This paper considers multiple-contact arrangements where several bodies grasp, fixture, or support an object via frictional point contacts. Within a strictly rigid-body modeling paradigm, when an external wrench (i.e., force and torque) acts on the object, the reaction forces at the contacts are typically indeterminate and span an unbounded linear space. This paper analyzes the contact reaction forces within a generalized quasi-rigid-body framework that keeps the desirable geometric properties of rigid-body modeling, while also including more realistic physical effects. We describe two basic principles that govern the contact mechanics of quasi-rigid bodies. The main result is that for any given external wrench acting on a quasi-rigid object, the statically feasible contact reaction forces lie in a bounded Polyhedral set that depends on the external wrench, the grasp's geometry, and the preload forces. Moreover, the bound does not depend upon any detailed knowledge of the contact mechanics parameters. When some knowledge of the parameters is available, the bound can be sharpened. The polyhedral bound is useful for "robust" grasp and fixture synthesis. Given a set of external wrenches that may act upon an object, the grasp's geometry and preload forces can be chosen such that all of these external wrenches would be automatically supported by the contacts

This paper presents a load-sensitive continuously variable transmission (CVT) for finger joints. The fingers of a robot hand require power when grasping an object and speed when opening and closing. Therefore a CVT is ideal to improve the power transmission of a finger joint. Existing friction CVTs are too big and heavy to be installed in a finger joint. By focusing on the fact that finger joints do not necessarily rotate 360 degrees, a remarkably simple and small load-sensitive CVT can be developed based on a crank CVT. The mechanism consists of a five-bar linkage and a torsion coiled spring. We have developed one joint with the CVT and have experimentally verified that the CVT can increase its reduction ratio from 0.5 to 3.3 in response to a load.

We have proposed a self-reconfigurable parallel robot, which can be configured to 4R and 5R closed kinematic chains. This paper proposes a parallel mechanism mobile robot by mounting it on a crawler mechanism. The combined mobile robot gains some useful functionalities other than just locomotion as an advantage of its parallel mechanism, such as getting over a bump by controlling its center of gravity and carrying an object by making use of its shape. Furthermore, the robot can form three-dimensional structures with other such robots and reach a certain height which the single one cannot. We have developed two such robots that are self-contained. This paper analyzes the motions of the functionalities and verifies them experimentally using the robots.

This paper proposes a novel self-reconfigurable parallel robot which is capable of self-reconfiguring to other various types of planar parallel robots on a horizontal plane. The limbs (legs) of the proposed parallel robot are 2R (two-revolute-joint) open kinematic chains whose second joints are unactuated. Reconfiguration is done by the coupling and decoupling of the platform(s) and limbs, which enables the proposed parallel robot to change workspaces and exchange tools. Uncertainty singularities enable such a robot to self-reconfigure without additional actuators at its coupling mechanism. This paper proposes appropriate uncertainty singular configurations for coupling and decoupling. In addition, it is shown that there exist a geometrically stable uncertainty singular configurations, which are useful especially for decoupling. Experiments are carried out to verify the self-reconfiguration.

This paper considers 2D contact arrangements where several bodies grasp, fixture, or support an object via frictional point contacts. Within a strictly rigid body modelling paradigm, when an external wrench (i.e. force and torque) acts on the object, the reaction forces at the contacts are indeterminate and span an unbounded linear space. This paper analyzes the contact forces within a quasi-rigid body framework that keeps the desirable geometric properties of rigid body modelling, while also includes more realistic physical effects. Using two principles governing the mechanics of quasi-rigid contacts, we show that for any given external wrench acting on the object, the contact forces lie in a bounded polyhedral set. The polyhedral bound depends on the external wrench, the grasp's geometry, and the preload forces. But it does not depend on any detailed knowledge of the contact mechanics parameters. The bound is useful for "robust" grasp and fixture synthesis. Given a collection of external wrenches that may act on an object, the grasp's geometry and preload forces can be chosen such that all of these external wrenches would be automatically supported by the contacts.

We have developed a self-reconfigurable robot which can form a 5R closed kinematic chain, only two of whose joints are actuated. This paper discusses its dynamic rolling. When it rolls, it has one DOF of its absolute orientation besides two DOFs of its shape. We show that the absolute orientation is subject to an acceleration constraint, not a velocity constraint. Therefore, the dynamics of the rolling motion needs to be formulated to control it. This paper proposes a controller which can reduce its negative acceleration caused by gravity. The shape and orientation of the robot cannot be controlled simultaneously. This paper proposes a control strategy switching shape and orientation controllers. We verify the effectiveness of the control strategy by simulations and experiments.

This paper proposes a reconfigurable planar parallel robot by coupling two 2R open kinematic chains (or 2-link robots), the first joints of which are passive. We show that they can reconfigure to a 5R closed kinematic chain which has the same number of actuators as its degrees of freedom. They can also reconfigure to a 4R closed kinematic chain plus one actuated link. The parallel robot has only two actuators but can have multiple functions by reconfigurations. Due to the passive joints, whether or not the 2R open kinematic chains can couple with each other is a non-trivial problem. We propose coupling sequences for forming the 4R and 5R closed kinematic chains and verify those experimentally.

This paper proposes whole quadruped manipulation, a novel manipulation with a quadruped robot using its whole body. The quadruped robot we have developed can stand on its knees and its two legs can serve as arms. The robot can hold a relatively big and heavy object in its two arms, and can manipulate it by moving its body. The desired configurations of the robot during the manipulation are at an increased mobility singularity if the whole distal links of its two legs are in contact with the floor or ground. The problem with the singularity is that the mobility of the robot changes significantly around it. This paper shows a contact type for the two legs to avoid such a singularity. We verify that our quadruped robot can perform the proposed manipulation experimentally.

The equilibrium equation of a power grasp cannot determine the grasp force uniquely in general. This paper proves that the indeterminate grasp force is, within a bounded hyper-polyhedron, not necessarily convex by considering the compatibility with rigid body motion. The maximum fraction angle is found at its vertex. Thus, if all forces at the vertices are within the friction cone, then all forces in the hyper-polyhedron are within the friction cone. Based on this analysis, we present an algorithm for computing the joint torques that can balance a given set of external disturbances.

This paper presents an approach to fast object manipulation by dextrous re-grasping of multi-fingered hands. The approach is based on a real-time grasping force optimization (GFO) algorithm and a fingertip impedance control scheme. Both the controller and the GFO make use of 6D contact force sensor data at run-time. The latter keeps the contact forces as small as possible while considering friction limits at the contact points during (re)grasping. The impedance controller is used to impose the optimized contact forces onto the grasped object while simultaneously enabling active control of the fingertip positions. Experiments demonstrate the robustness of the approach and the increase in task speed during multi-fingered manipulation.

This paper analyzes the indeterminate grasp force in power grasps with a rigid body model. A power grasp overconstrains an object with multiple contact points using the surfaces of finger links and palm. It is known that the overconstrained grasp results in the static indeterminacy of the grasp force. This paper shows that it also results in an infeasible combination of the sliding directions at the contact points. A static friction force acts only in the opposite direction of the trend of sliding. This characteristic of friction restricts the grasp force in power grasps although it is indeterminate. We first show an example to illustrate the restriction on the grasp force, and then formulate it formally. This analysis leads to a special case where the grasp force is unique.

We demonstrate the robust execution of two regrasping primitives, rotation and pivoting on a four-fingered hand, based on the real-time sensors data based control. We indicate frequently occurring grasp errors and faults during execution of the two regrasping primitives. The sensors data is obtained from two sources. One is force-torque sensors mounted on the finger tips of the four fingers. The other is a laser range sensor mounted on the palm of the hand. The grasp information acquired through these two sources is useful for both sensing the errors and controlling the fingers. The paper proposes strategies to recover or prevent faulty grasps during manipulation, which may lead to unwanted object movements or grasp failures. The object to be manipulated is a polygonal prism, the model of which is known a priori.

We developed a quadruped robot which can take various postures, e.g. lying on the floor and kneeling. When the limbs are free from supporting the body of the robot, they can serve as arms. Up to two limbs can be freed from supporting the body when the robot kneels. The motion of the robot is constrained if it maintains current contact with the floor. The paper analyzes possible motions of the robot to maintain current contact. We show that even if the same parts of the robot are in contact with the floor, there exist singular postures at which the body of the robot has an additional degree of freedom.

This paper proposes a learning method which learns a motion by employing an assistance in order to simplify it. This learning is done from easy to difficult level. Using genetic algorithm, it searches for the parameters of a controller appropriate for controlling the motion to be learnt by gradually increasing difficulty, i.e., by gradually decreasing the degree of assistance. We show that this gradual search enables genetic algorithm to evolve a population of controllers efficiently by giving two examples: stable riding of a bicycle and stable controlling of a double inverted pendulum. A bicycle is much easier to control when it is running at a certain velocity. An initial velocity is given as assistance and it is decreased gradually. Similarly a double inverted pendulum is much easier to control when an upward force supports the distal end of the pendulum. The reduction rate of assistance is adjustable in accordance with the adaptability of a population to the reduction.

This paper focuses on a specific way of performing reorientation which is often observed when a human hand revolves a cylindrical object by using the whole hand. We put more emphasis on the manipulative task than the firm grip made by enveloping grasp. This paper interprets such reorientation as the sequence of two two-point grasps, one a fingertip grasp, the other an enveloping grasp. We concern ourselves mainly with the two-point grasps and the transition from enveloping to fingertip grasp in the reorientation. This interpretation leads to geometrical conditions that determine whether sliding is necessary for the transition from enveloping to fingertip grasp or not. We present techniques of active sensing to detect or search for the two-point grasps using force sensors attached to the distal links of the fingers.

This paper concerns the reorientative manipulation planning for a multifingered hand to bring the grasped object into a specific desired orientation without being released or intermediate placing and repicking. A planner is presented based on primitives. It basically generates a sequence of two primitives: rotation and pivoting. Use of primitives simplifies the complex three-dimensional reorientation tasks by disintegrating it into a sequence of simple and usually two dimensional motions. In the first off-line phase, executed once only for the given object, the planner constructs a structured states network composed of all those orientation states of the object at which at least one of the rotation or pivoting primitives is feasible. The second online phase of the planner can be repeatedly provoked to find a sequenced route on the states network between the initial and goal orientation. A simulation program has been developed for the proposed planner.

This paper studies regrasping by a multifingered hand to achieve a desired reorientation of an object by using regrasp primitives. Among them is pivoting in which two fingers grasp an object with their fingertips forming an axis of rotation and the third finger rotates the object about this axis. This paper presents an algorithm for calculating the region for the axis for which the third finger can rotate the object at given angles. Pivoting is also efficient to achieve three dimensional reorientation of an object when it is used together with other primitives. This paper also discusses how sequential executions of primitives achieve three dimensional reorientation.

The grasp force in power grasps is not necessarily determined uniquely by joint torques when Coulomb friction is assumed in the contact points between a grasped object and finger links. This paper analyzes the indeterminate grasp force with their rigid body models. This paper shows that contact sliding directions are constrained in power grasps. The frictional force acts only in the opposite direction of sliding. This characteristic of friction restricts the grasp force in power grasps although it is indeterminate in general. First the authors show an example to illustrate this restriction imposed on a grasp force. A special case where it is unique is shown.

A multifingered hand with touch sensors has grasping and manipulating functions, and has the function of a sensor probe. We have been studying the merging of these two functions, the acquisition of an object model by manipulation with a multifingered hand, and determining the next finger action based on the acquired information. By manipulating objects while acquiring the object models, we expect to be able to manipulate many types of objects and unknown objects. This paper discusses a multifingered hand system for acquiring an object model while manipulating the object, by using the contact point information between the fingertips and object.

A multifingered hand can reorient an object by regrasping it in a hand. This paper presents a planner which plans a sequence of repositioning of fingers for horizontal rotation of an object for a desired angle. The authors previously developed an algorithm for computing contact positions of fingers where they can maintain equilibrium. The algorithm is used to compute a new contact position of a removed finger where there is a finger which can be removed next. Based on these computations, the authors develop an algorithm for searching for a sequence of repositioning of fingers. Examples show that the algorithm can efficiently find sequences which require the number of repositioning steps.>

A multi-fingered robot is an artificial organ with many sensors and actuators which require both real-time control and higherlevel motion coordination. A two-layered task architecture for the control of a multi-fingered robot is presented. A control unit, called an agent, is split into two tasks, lower and upper. While a lower task is performing real-time computation, the upper task takes care of communication with other agents. The system is implemented with VxWorks on multi processors and an agent network for the description of a pick-up grasping task is shown.

This paper proposes an algorithm for computing the fingertip positions of an equilibrium grasp for a polyhedral object. The authors has already developed such an algorithm for a planar grasp where the problem can be reduced to a linear programming problem using the static equivalence: the effect of changing a fingertip position along an edge is equivalent to the effect of changing the fingertip forces of two virtual fingers, one fixed at each edge endpoint. This equivalance makes the moment equilibrium equation in the planar grasp linear. In a spatial grasp, introducing such virtual fingers to the faces of the object decomposes the moment equilibrium equation into linear and nonlinear constraints. The nonlinear constraints still remain, but exhibit the same properties as the integer requirement in an integer programming problem. This paper proposes an algorithm based on the branch-and-bound method that decomposes each finger region until the nonlinear constraint associated with the finger is satisfied. Numerical examples show that the algorithm effectively solves problems of practical size.>

A qualitative reasoning planner for behavior improvement by selecting and determining robot control parameters to drive manipulation actions has been developed, integrated into a telerobot system, and demonstrated for a match striking task. The planner consists of a qualitative reasoner and a numerical execution history which interact to jointly direct and narrow the search for reliable numerical control parameter values. The planner algorithm, implementation, and an execution example are described.>