Isao Shimoyama

Dynamic Walk of a Biped

The authors have developed five kinds of biped locomotive robots so far. They are named BIPER-1, 2, 3, 4, and 5. All of them are statically unstable but can perform a dynamically stable walk with suitable control. BIPER-1 and BIPER-2 walk only sideways. BIPER-3 is a stilt-type robot whose foot contacts occur at a point and who can walk sideways, back ward, and forward. BIPER-4s legs have the same degrees of freedom as human legs. BIPER-5 is similar to BIPER-3, but in the case of BIPER-5 all apparatus, such as the computer, are mounted on it. This paper deals with the control theory used for BIPER-3 and BIPER-4. In both cases, basically the same control method is applied. The most important point is that the mo tion of either robot during the single-leg support phase can be approximated by the motion of an inverted pendulum. Ac cordingly, in this paper, dynamic walk is considered to be a series of inverted-pendulum motions with appropriate condi tions of connection.

An air flow sensor modeled on wind receptor hairs of insects

A new conceptual air flow sensor modeled on wind-receptor hairs of insects which can detect low velocity air flow is demonstrated. Since the viscous force is dominant at micro size, the velocity of air flow can be determined by measuring the force on a sensory hair. Two mechanical structures modeled on insect sensory hairs have been fabricated. An array of a 1-DOF (Degree Of Freedom) sensory hairs has selectivity of frequencies. A 2-DOF sensory hair array can detect the direction angle of air flow. Both sensors have cantilevers and strain gauges fabricated at the bottom of the sensory hairs. The output voltage was proportional to the velocity of air flow in good agreement with the theory. Both the 1-DOF sensory hair and the 2-DOF sensory hair arrays detected the velocity of air flow from several tens of cm/s to 2 m/s. Also, the 2-DOF sensory hair array detected the direction angle of 360 degrees as a function of a sinusoidal curve.

Insect-model based microrobot with elastic hinges

This paper describes the new concept of making a microrobot based upon insects and its implementation using rigid plates and elastic hinges. One unique feature of an insects structure is its deformable external skeleton, to which wings and legs are attached, forming a closed-loop mechanism. Frictionless deformation of elastic elements, instead of conventional rotational joints, allows for efficient actuation in the microscale. We propose three-dimensional micromechanisms based on an external skeleton and have fabricated several examples using polysilicon plates and polyimide hinges. By folding the polysilicon plates along the polyimide hinges just like paper, 3D structures can be constructed on silicon wafers. These structures can be easily actuated by electrostatic force. Closed-loop flapping mechanisms have been fabricated and electrostatically actuated to demonstrate the motion of the external skeleton system. Resonant vibration was observed in a frequency range of around 10 kHz. Actuation using electrostatic induction is also considered. >

Force sensing submicrometer thick cantilevers with ultra-thin piezoresistors by rapid thermal diffusion

One of the most important requirements for a cantilever-type sensor to obtain high force sensitivity is small thickness. By using current micromachining technology it is possible to produce cantilevers of submicrometer thickness. Where self-sensing piezoresistive cantilevers with submicrometer thickness are concerned, it is necessary to use a technology which can create ultra-thin (<100 nm) piezoresistors on a cantilever surface. This work demonstrates for the first time the application of a relatively simple, rapid thermal diffusion method by using spin-on glass film to fabricate sub-100 nm piezoresistors on an ultra-thin single-crystal silicon cantilever. Compared to other shallow junction fabrication methods, which involve implantation or deposition of a doped layer, this method is advantageous since no damage is created in the crystal structure and no toxic gas or hazardous material is used during the process. Besides, this technique can be applied by using low-cost rapid annealers, which can be readily found in most laboratories. By using this method, piezoresistive cantilevers with stiffness in the range of 0.001 N m−1 with sub-100 nm thick piezoresistors are fabricated, and a complete characterization of the fabricated cantilevers is performed.

Locomotion control of a bio-robotic system via electric stimulation

This paper investigates the reaction of a living insect to electric stimulation. Artificial electrical stimulation is one of the tools of neuroethology to investigate the neural system. By creating artificial inputs to the system, specific reaction can be observed. The escape turn is a well-known reaction pattern of an insect in response to the appearance of a predator. In the first part we analyze the locomotory reaction of an insect (Periplaneta Americana) to various electrical stimuli. These stimulus-reaction measurements are done on a light-weight styro-foam trackball which is connected to a computer. This allows us to record the turning rate and the forward movement of the insect in response to antennal stimulation. Based on this data a simple mathematical model is established. As a simple example of an autonomous bio-robotic system and to verify the black-box model an electronic backpack which does line-tracking has been built. Using two photosensors as inputs the electronic backpack forces the insect to walk along a black line.

Polymer thin film deposited on liquid for varifocal encapsulated liquid lenses

We developed a process for making liquid lenses that have a tunable focal distance. In our process, polymer thin films are directly deposited on liquid droplets in vacuum. Conducting the deposition in vacuum helps preserve the delicate spherical droplet shape so that they can be used as lenses. The polymer film is mechanically stable, which protects the droplets from the ambient, but it is also extremely thin and flexible, which allows the droplets to deform. The droplets are deformed using electrostatic force to change their focal distance. Our lens is structurally simple and can be operated by an electrical input.

Synthesis of the pheromone-oriented behaviour of silkworm moths by a mobile robot with moth antennae as pheromone sensors

The authors have studied the emergent mechanism in insect behavior by using a robotic system. Since insects have a simpler nervous system than humans, it is an appropriate model for clarifying the above mechanism. In this study, the pheromone oriented behavior of male silkworm moths was shown by a pheromone-guided mobile robot which had male moth antennae that can detect sex pheromones. This study focuses on the pheromone sensor that used antennae from a living moth. Since the antennae of silkworm moths are very sensitive as compared to artificial gas sensors, they can be used as living gas sensors that can detect pheromone molecules.

Three-dimensional micro-self-assembly using hydrophobic interaction controlled by self-assembled monolayers

This paper describes three-dimensional micro-self-assembly using hydrophobic interaction. The interaction between microparticles was controlled using self-assembled monolayers formed on the particles. The particles were stirred in a dispersion liquid to create a binding for connecting their surfaces directly. The interaction between the particles was described by the thermodynamic free energy of adhesion, which was calculated using the surface free energies of the solids and the liquid. The calculated free energy was then used to predict the bindings between particles. The binding probability was estimated by counting the number of microparticles that became bound to hydrophobic and to hydrophilic areas patterned on a substrate. The ratio of the bound particles was correlated to the difference between the free energies of the two areas, as predicted using the free energy calculation. This means that microparticle binding is controlled by the surface properties. Structures composed of several microparticles were successfully self-assembled using this principle. Hydrophobic interaction can thus be applied to micro-scale self-assembly.

A radio-telemetry system with a shape memory alloy microelectrode for neural recording of freely moving insects

A radio frequency (RF) telemetry system with a shape memory alloy microelectrode was designed and fabricated. The total size and weight are 15 mm /spl times/8 mm and 0.1 g, respectively. Since the telemeter is small and light enough to be loaded on a small animal such as an insect, the system can be used for the neural recording of a freely moving insect. The RF-telemeter can transmit signals by frequency modulation transmission at 80-90 MHz. The transmitted signals can be received up to about 16 meters away from the telemeter with a high signal-to-noise ratio. The neural activity can be detected without attenuation by using an instrumentation amplifier with its input impedance set to 2 M/spl Omega/ at 1kHz. The telemeter was loaded on a cockroach and the neural activity during a free-walk was successfully measured through this telemetry system.

Home-Assistant Robot for an Aging Society

Many countries around the world face three major issues associated with their aging societies: a declining population, an increasing proportion of seniors, and an increasing number of single-person households. To explore assistive technologies that can help solve the problems faced by aging societies, we have tested several information and robot technologies. This paper introduces research on a home-assistant robot, which improves the ease and productivity of home activities. For people who work hard outside the home, the assistant robot performs chores in their home environment while they are away. A case study of a life-sized robot with a humanlike functional body performing daily chores is presented. An integrated software system incorporating modeling, recognition, and manipulation skills, as well as a motion generation approach based on the software system, is explained. Moreover, because housekeepers perform chores one after another in their daily environment, we also aim to develop a system for continuously performing a series of tasks by including failure detection and recovery.