Hiromi Mochiyama

Kinematics and dynamics of a cable-like hyper-flexible manipulator

A Hyper-Flexible Manipulator (HFM, for short) is a kind of continuum robots with a simple mechanical structure like a cable, rope and string, which are useful tools utilized everywhere in various forms. In this paper, in order to achieve dexterous and useful manipulation by this type of robot, we discuss kinematics and dynamics of an HFM. We rigorously derive a spatial, nonlinear and continuum dynamics model with an underactuated mechanism using special kinematics based on curve geometry and theory of robot manipulation.

Dynamical modelling of a hyper-flexible manipulator

In this paper, a three-dimensional dynamics model of a hyper-flexible manipulator like a string is derived based on a slice of the arm, which is regarded as a rigid link with an infinitesimal width of a serial rigid chain manipulator. We show the model in three forms familiar in the theory of robot control: Newton-Euler, Lagrange and regressor representations.

A compact jumping robot utilizing snap-through buckling with bend and twist

In this paper, we propose a robotic catapult based on closed elastica utilizing bending and twisting deformation of an elastic strip. By using snap-through buckling generated from not only bend but also twist of thin rectangle elastic strip, impulsive forces can be generated repeatedly by the frequency of 3[Hz] without changing added torque directions. The compact jumping robot based on the proposed robotic catapult can leap over 950[mm] away. In addition, by setting the parameters appropriately to make the best use of generating impulsive forces with high frequency, it can perform repeated low-altitude jumping motions with about 1.06[m/s] velocity including quick step of about 0.152[s].

A compact kick-and-bounce mobile robot powered by unidirectional impulse force generators

In this paper, we propose a compact kick-and-bounce mobile robot powered by unidirectional impulse force generators. The unidirectional impulse force generator is a simple mechanical device for generating high-frequency impulse forces toward a certain direction unilaterally utilizing snap-through bucklings. The proposed kick-and-bounce robot has a pair of the unidirectional impulse force generators as the muscles of its biped legs. The robot moves forward rapidly by the repetition of the kicks and bounces to the ground. We show that the developed palm-top mobile robot whose weight is of only 67[g] achieves the velocity of 0.8[m/s] instantaneously.

An asymmetric robotic catapult based on the closed elastica for jumping robot

In this paper, we propose a new asymmetric robotic catapult based on the closed elastica. The conventional robotic catapults based on the closed elastica which the authors developed are the robotic elements for generating impulsive motions by utilizing a snap-through buckling. In a typical closed elastica, the two ends of an elastic strip are fixed to a passive rotational joint and an active rotational joint, respectively. Here we found that by adding only a range limitation to the passive rotational joint, compared to the conventional type, the deforming shape of the elastic strip becomes more complicated and 40% more elastic energy can be stored. Using this modification, we can develop a compact jumping robot which is able to leap over 700[mm] away and 200[mm] high.

Whole-arm impedance of a serial-chain manipulator

In this paper, we propose a mechanical impedance for the whole arm of a serial-chain manipulator. The proposed impedance has a geometrically natural property owing to use of a spatial curve which describes a virtual reference of the impedance. The proposed impedance is useful for geometric task planning in whole-arm manipulation. Illustrative examples are shown for understanding of the impedance.

A robotic catapult based on the closed elastica with a high stiffness endpoint and its application to swimming tasks

In this paper, we propose a new robotic catapult with a high stiffness endpoint. The conventional robotic catapults based on the closed elastica are robotic elements for generating impulsive motions by utilizing the snap-through buckling. In a typical robotic catapult, the two ends of an elastic strip are fixed to a free joint and an active joint, respectively. Here we found that by adding only the high stiffness at the free joint, compared to the conventional type, more elastic energy can be stored and release surely without loss of a characteristic of generating impulsive motion repeatedly. By utilizing the high stiffness endpoint, we develop a faster impulsive swimming robot than the conventional one.

Kinematics for the whole arm of a serial-chain manipulator

This paper provides a viewpoint for kinematics for the whole arm of a serial-chain manipulator with 2-d.o.f. rotational joints. An in-depth understanding of the duality between a rigid link and a 2-d.o.f. joint allows us to derive simple and geometric equations describing the manipulator kinematics. The obtained kinematic equations are analyzed in two ways compared with the Frenet-Serret formula of a spatial curve which is utilized for a reference shape of the manipulator. One way is based on limit analysis where we increase the number of joints while the total length of the manipulator remains constant. The other way utilizes an extended mechanism through the link-joint duality. The information presented in this paper is useful for mechanism design dynamic analysis, control design and motion planning of the manipulators in whole-arm manipulation.

Impulse force generator based on snap-through buckling of robotic closed elastica: Analysis by quasi-static shape transition simulation

In this paper, we investigate the property of an impulse force generator based on snap-through buckling of a robotic closed elastic rod which is considered as one of good examples of continuum robots. The impulse force generator considered here utilizes a snap through buckling of an elastic rod where its base end is pinned and driven by a rotary actuator forcibly while the tip end is pinned or clamped to the fixed point. One of the most fundamental design problems is to maximize the released elastic energy at each buckling state subject to limited ranges of driving torque and angle of a given actuator. From this design viewpoint, we show two findings obtained from quasi-static planar shape transition simulation of the closed elastica, which will be useful for a design of the robot, that is, the ratio of the elastica length and the endpoint distance decides 1) the buckling angle which relates to the range of an actuator driving angle, and 2) the released elastic energy per the maximum driving torque. We also provide a mathematical description of snap-through buckling based on which we can measure a distance to a buckling point.

Shooting Manipulation Inspired by Chameleon

In this paper, we propose two chameleon-like shooting manipulation systems for manipulating a distant object in an instant. The proposed systems mechanistically act on a remote target by constraining an end-effector catapulted by an impulsive air flow through a flexible string. One prototype constrains the end-effector by an elastic cantilever through the string, and experimental results show that a prototype realizes a quick capturing of a falling object 0.7 m away with a high success rate of 92%. The other prototype constrains the end-effector by an inertial wheel through the string. We consider a 2-D model of the system and simulate its trajectory. Simulation results show appropriate trajectory and clarify the robustness for the variation of some parameters. Furthermore, experimental results show that the second type of the shooting manipulation system can manipulate a distant target object in a blind spot not only in the case of a vertical blind spot but also in the case of a lateral one.