Kenji Nishibori

PWM driving characteristics of robot hand with fingers using vibration-type ultrasonic motors

A Langevin-type ultrasonic vibrator works as an ultrasonic motor when it is pressed slant wise against the surface of an object. This paper describes a robot hand with three fingers that each works as an ultrasonic motor. This robot hand can simultaneously grasp a cylindrical body and rotate the body about its axis. The authors propose a PWM (pulse width modulation) method for controlling the speed of ultrasonic motors by changing the duty ratio of the voltage applied to the motors. The vibration of the ultrasonic motor and the driving characteristics of a robot hand were examined experimentally. It was confirmed that the vibration speed of the tip of the ultrasonic motor wets approximately proportional to the duty ratio of the applied voltage. The velocity of the motor increases with an increase in duty ratio, except for the offset region. The torque characteristic curves approach the point of origin, moving parallel as the duty ratio decreases.

Position control of robot manipulators with ultrasonic motors using pulse width modulation

This paper proposes position control of robot manipulators using ultrasonic motors under a fuzzy controller and a rotational speed control method, such as pulse width modulation (PWM), by changing the duty ratio of the forward direction duration, which we proposed in a previous paper. From the experiments, it was confirmed that exact position control of the manipulator was achieved through an adjusting motion, such as with a pulse motor, besides the position control using a fuzzy controller for instance. The ultrasonic motor is hardly affected by the friction in the position control since the rotor can approach a desired position with the jitters by PWM.

Robot hand with fingers using vibration-type ultrasonic motors (driving characteristics)

An ultrasonic motor is a promising actuator for robots since it has a simple construction, high response, and high torque at low speeds. This paper proposes a robot hand using vibration-type ultrasonic motors as the fingers instead of moving elements. This robot hand with three fingers can simultaneously grasp and rotate a cylindrical body. The driving characteristics of the robot hand were examined experimentally under various conditions. It was confirmed that high torque was obtained when the optimum contact angle and contact force of the ultrasonic motors were used. The reduction of the output torque is small even when the diameter of the rotational body deviates from the designed value.

Measurement of mirror inclination angle and distance using LED light sources and PSD

This paper proposes measurements of a two-dimensional inclination angle of a mirror, and its distance to the mirror, using four infrared LEDs that are located around a position sensitive detector (PSD). The light of each LED is reflected by a mirror and focused on the two-dimensional PSD through a lens. This method has many advantages. The mirrors inclination angle is able to be measured by two LEDs at opposed positions without having to depend on information about the distance to the mirror. Since the LEDs act as point sources of light, it is unnecessary to have to adjust the axis of light. This device has a simple structure, and the light itself is safe since the source is an LED, not a laser light. It was confirmed that the measurement accuracy of the inclination angle was less than 0.5 degrees in a wide range of −10 to 10 degrees and the result was sufficiently satisfied. This equipment can also measure the distance between the sensor and the mirror with an accuracy of 5 percent.

Driving Characteristics of Robot Hand with Fingers using Langevin-Type Ultrasonic Motors

An ultrasonic motor is a promising actuator for robots since it has a simple construction, high response, and high torque at low speeds. This paper proposes a robot hand using Langevin-type ultrasonic motors as the fingers instead of moving elements. This robot hand with three fingers can simultaneously grasp and rotate a cylindrical body. The driving characteristics of the robot hand were examined experimentally under various conditions. It was confirmed that high torque was obtained when the optimum contact angle and contact force of the ultrasonic motors were used. The reduction of the output torque is small even when the diameter of the rotational body deviates from the designed value.

419 Downsizing of Cap Installation Robot for Tying Task of Traditional Craft "Shibori"

Fig. 2 Cap installation robot 2.2 ロボットの動作 Fig. 2 は布にキャップを装着するロボットの全体図を示 す.キャップの装着には,ニードルを上下させるために IAI 製のリニアアクチュエータ RCP5-SA4Cを使用した. Fig.3 はシリコンキャップを布に装着する一連の動作を示 す.Fig. 3(a) の待機状態では,布の位置合わせを行う.作 業開始ボタンを押すと,ニードルが Fig. 3(b)の位置まで降 下する.この状態までは,安全のためにニードルがニードル ガードから出ていない.さらにニードルを下げると,ニード ルがニードルガードから突き出る.キャップの先端から 4mm 突き出した Fig. 3(c)の位置で止まり,布にキャップが装着 される. その後,ニードルを持ち上げると,ニードルに布とキャッ プが付いた状態で上がってくる.しかし,Fig. 3(d)の状態 まで持ち上がると,ニードルガードがキャップの付いた布を はたき落とす.

Cylindrical tactile sensor for a robot hand using position sensitive detectors on a suspension shell

In this paper, we propose a cylindrical tactile sensor for robot hands that can simultaneously detect the contact angle, contact location, and magnitude of the contact force. This sensor consists of an inner frame with light sources and an outer shell to which two position sensitive detectors (PSDs) are fixed; the concentric outer shell and inner frame are separated by two elastic rings. Since each two-dimensional PSD is installed on the same cross section as an elastic ring, the output of a PSD directly corresponds to displacement of an elastic ring. Based on experiments performed on a prototype, we found that values for contact angle, contact location, and magnitude of the contact force could be obtained with good accuracy from simple mathematical expressions. Consequently, this cylindrical tactile sensor is considered to be effective as a tactile sensor for robot hands.

Automation of tying task on tie-dyeing of traditional craft by robots

There is a serious problem of aging of the craftsmen who have tie-dyeing technique of Japanese traditional craft “Shibori”. In substitution for “tying” process by thread on tie-dyeing, this paper proposes usage of elastic cap with different thickness at the both ends. A cloth is pushed into the cap by a needle of 1 mm diameter attached on the robot hand. It was confirmed that the cloth was tightened at the both ends of the elastic cap and the effect of the tie-dyeing was valid. The usage of the elastic plastic cap realizes the tie-dyeing pattern similar to the conventional method using thread. Moreover, these elastic caps are reusable. To improve the work efficiency, a cap cartridge and a sub robot attached on the robot hand were examined. The high efficiency of the work was achieved and an increase in the speed of robot was also effective. In regard to polyester cloth, its elasticity increases with projections that are created when the wet heat treatment is applied with the caps on. In this case, the stretch properties are also effective.

Passive-type aerial acrobat robot climbing up row of swings with rising slope

This paper describes a theory and experimental results concerning a passive aerial acrobat robot without electric power. As the robot performs hand-to-hand on its flying trapeze, it utilizes no electricity but simply draws power from the mechanical potential energy of its swings. The robot, holding onto the trapeze, overcomes the rotation moment by aid of a counterbalance that is on the opposite side of the swing and the robot begins to move. As the counterbalance is set on the frame of the swing at offsetting distance, a large rotation moment is generated, even when the robot gets to the most inferior point. As the result, the robot rises at an accelerated rate through the bottom point. When the robot reaches up to the height of the next swing, the hand of the robot slips from the handrail and the robot is released from the swing. At that time, the robots arms bend forward by a spring installed inside the body of the robot, and the robot can catch hold of the handrail of the next swing. It was confirmed that the robot was able to transfer continuously throughout a set of the swings. It looks strange that the robot goes upward against the gravitational force and finally makes 90-degree turn to get to the goal.

Measurements of inclination angle and distance of curved mirror using LED light sources

There is a demand for measuring the inclination angle of a convex mirror or a concave mirror (curved mirror) used for a door mirror of a vehicle and a virtual screen display, etc. with non-contact method using an optical system. Therefore in this study, we aim to develop the device that has a simple structure using four infrared LEDs as light sources and a two-dimensional PSD (position sensitive detector). This sensor can measure the inclination angle and distance of the convex mirror or the concave mirror with a high degree of accuracy by utilizing a curvature coefficient depending on the curvature radius of a curved mirror. As the result of experiments, the measurement accuracy of the angle is within ±0.5 degrees and the distance L from the sensor to the mirror can be measured with ±5 percent accuracy that indicates a sufficient accuracy.