Sakiichi Okabe

Development of Powerful Airborne Ultrasonic Transmitter for Robot Metrology

An airborne ultrasonic transmitter which uses an electric spark discharge was developed for robot metrology. By inserting a condenser of a few hundred picofarads to the secondary side of an ignition coil in the electric circuit of the transmitter, the sound pressure of the radiated ultrasonic pulse becomes about ten times as strong as the case in which the condenser is not inserted. An ultrasonic ranging system which uses this transmitter was also developed.

Measurement of 3-D position and orientation of a robot using ultrasonic waves

A system for measuring the 3-D position and orientation of a robot hand using ultrasonic waves is proposed. The principle is a triangulation using distances between transmitters attached to a robot and receivers placed around the robots work space. An electric spark discharge which works as a nondirectional point source of ultrasound is used as a transmitter. This system is simple and economical compared with that using laser beams or light-emitting diodes. The accuracy is good because it measures distances directly from the transit time of an ultrasonic pulse. The relationship between the accuracy and the number of receivers is discussed, and the possibilities of automatic tracking of a moving transmitter are examined.<<ETX>>

Development of Fast and Fine Position Control System of an Ultrasonic Motor

This paper shows experimentally that an ultrasonic motor has an approximate first-order transfer function between phase shift input and rotational speed output. A position control system which feedbacks position and velocity involving integral control action was developed. A fast response of about 100 msec and fairly high positioning accuracy up to a rotary encoder resolution were both realized in this system.

Investigation on Mathematical Exact Model for Actual System.

Motor systems are mainly acted as the devices which produce driving forces. Besides, it is found by carefully observing the condition of motor system that the motor systems may have an examining function about work conditions. In this case, it is required that parameters of the motor systems can be accurately identified, and the mathematical model established for these motor systems must be correct. Nevertheless, the mathematical model established for these motor systems is sometimes ambiguous, or the mathematical model sometimes changes with the change of work conditions. Under these circumstances, the mathematical model established originally is not agree with the actual motor system. So it is impossible to identify the correct parameters. In this paper, an example is given as the case that the mathematical model established originally is not correct. Subsequently, the error between the ambiguous mathematical model and current value of the actual motor system is evaluated. Finally, on the basis of the error evaluation, we try to propose the mathematical model with higher precision.

The Basic Study for Automatic Disassembly. Modeling of Parallel Disassembly Operation Process Using Timed Petri Nets.

Disassembly operations of used machines are very important processes for recycling and reuse of various materials and parts. This paper treats the fundamental concepts of disassembly and the simulation method for planning of disassembly operation using Timed Petri Nets (TPN). Some disassembly operation processes, arranged in parallel, are expressed by a TPN model considering the each function of system. Using this simulation method, the efficient schedule of disassembly process can be obtained analytically. It is shown also that the systems with some AGVs and/or buffers can be treated by this method. This simulation method has following advantages: (1) It is easy to understand the whole process of disassembly systems because the functions of systems are visually shown by the flow diagrams. (2) Mathematical treatment may be possible for time schedule analysis of disassembly processes. These advantages suggest that the proposed method is very useful for analyzing the efficiency and the design of the disassembly systems.

Digital stabilization of nonlinear time-delay systems and its robustness

This paper is concerned with digital control and robust stability for stabilizing nonlinear time-delay systems, in which hunting will often occur. First a new digital controller for stabilization is proposed, which is more effective than the usual Smith method. Next, the error function due to the identified error of dead time is derived, by which the robust stability condition is obtained in discrete time-delay systems. Finally, by applying a new digital controller to the electropneumatic valve positioner, it is confirmed through simulation and experimental studies that both the controller and its robust stability analysis are valid.<<ETX>>

A study of Sheet Feeding Mechanism Using Ultrasonic Vibration.

This study describes a sheet feeding mechanism which uses ultrasonic vibration generated by a piezoelectric actuator. The actuator vibrates in the sheet feeding direction and normal to the sheet feeding direction. It is an elliptical mode of vibration. In this paper, the motion of the vibrator is defined by the two motions of contact with the sheet and separation from the sheet, and it is determined theoretically that a sheet feeding speed can be controlled by the amplitude of elliptical vibration. As a result of fundamental experiments, it was proved that a sheet, such as paper or a telephone card. could be fed easily, and it was confirmed that the experimental curve of sheet feeding speed was in agreement with the theoretical curve.

Hooked Bimorph-Type Piezoelectric Microfinger.

In recent years, miniaturization of mechanical systems has made remarkable progress. Manufacturing systems for minute parts are necessary to advance miniaturization further. Each such system is composed of sections for material feeding, machining and transferring of parts. The handling technique of these workings is the essential point in system construction. This paper proposes that the handling device consists of a pair of bimorph piezo .members rigidly connected with other in series and fingertips attached to the pointed end, which is like a hooked finger. The device is able to move two-dimensionally by application of an independent voltage to each of the members. It is noted that there is an optimum value for height of the feeding plane and optimum combination of the attaching angle of the device and connecting angle of the members, which enhance quasi-static feeding performance. Experimental results agree well with the theoretical ones.

Self-contained Vibration Reducing Function by Interference Method on Vibratory Machine. (1st Report). Drive by Direct Exciting Force.

This study deals with reducing of transmissive vibration force by the interference method. The improved mechanism of the machine is constituted as two degrees of freedom vibration system. Assuming to eliminate a coupling spring, natural frequencies of two mass-spring systems are tuned to the same value each other. Vibrations of two bodies in the mechanical system are always held out of phase independently of exciting frequency. Then a fundamental resonance disappears and the secondary resonance becomes the only resonance, because the system is divided into a pair of mass-spring system by a node in the coupling spring to be regarded as a common fixed end. The new type vibratory feeder for automatic parts assembly system has developed as one of application of the vibration reduction method.

Study on Path-Speed Control of Robot Using Clothoidal Interpolation.

When a robot is used for doing work such as laser processing or water-jet processing, not only the trajectory of the end-effector but also its velocity is very important from the viewpoint of the processing accuracy. On the other hand, several curve-interpolation methods have been suggested, but it is cannot be said with certainty that the correct velocity control of the trajectory is possible. In this study, in order to solve this problem, a method using the clothoidal curve is introduced, and this method enables the velocity control with high accuracy for any trajectory.