Clean room robot with non-contact joints using magnetic bearingsHiguchi, Toshiro; Oka, Koichi; Sugawara, Hiroshi
doi: 10.1163/156855393X00078pmid: N/A
A new type of robot whose joints are supported by magnetic bearing mechanisms is proposed. This robot's joints are supported without mechanical contact. This avoids dust generation and oil lubrication which often create problems when robots are used in clean rooms, vacuum chambers, or in space. In addition to cleanliness and freedom from maintenance, the robot has a number of other advantages such as freedom from friction, and can accomplish functions such as micro-manipulation, force control, force sensing, active vibration control, and so on. A prototype manipulator with magnetic bearing joints has been made. The experimental results on the magnetic bearing joint show the feasibility of the proposed functions. A levitation experiment on the prototype robot link shows that the robot joints can be supported by a magnetic bearing mechanism and shows the feasibility of a robot with no mechanical contacts.
Turning gaits of a quadrupedal walking machineZhang, Chang-De; Song, Shin-Min
doi: 10.1163/156855393X00087pmid: N/A
The gaits used in the turning motion of a quadruped are studied and a general approach to compute the gait stability margins of turning gaits is derived. Depending on the location of the turning centre, the turning gaits are divided into two types: spinning gait and circling gait. The former is applied when the turning centre is at or close to the centre of gravity, whereas the latter is suitable for a more distant turning centre. The spinning gait is developed on the basis of the z type creeping gait and is optimized for stability. The optimization procedure yields two special gaits: the wave-spinning gait and the equal-phase-spinning gait. The circling gaits are developed based on the wave-crab gaits and they are called wave-circling gaits. The numerical results reveal that the analytical stability equations of wave-crab gaits can be applied to wave-circling gaits with a good accuracy for a large turning radius. In order to assist the selection of a turning gait, the stable areas of the turning centre of both spinning and circling gaits are generated graphically.
Estimation and control of the attitude of a dynamic mobile robot using internal sensorsMatsumoto, Osamu; Kajita, Shuuji; Tani, Kazuo
doi: 10.1163/156855393X00096pmid: N/A
For the control of a dynamic mobile robot, the attitude in gravity space is an important state of the robot. Usually, the attitude is difficult to detect by simply using the signals from sensors. For example, an external sensor contacting the ground suffers disturbances from the roughness of the ground; the integration of a gyroscope signal has the problem of drift; an inclination sensor does not indicate the direction of gravity when acceleration exists. To solve these problems, we propose a control method in which the attitude of a mobile robot is estimated by an observer considering the robot dynamics and using only the information obtained by internal sensors. We applied this method to a wheeled inverted pendulum as an example of a dynamic mobile robot. The estimation of the attitude was made with good accuracy using the signals from the rate gyroscope and the motor encoder, and the control of stable running of the pendulum on a flat level plane worked successfully. We also realized the running control of a pendulum on an unknown rough road using the estimation of the slope gradient made by the observer. Thus, the effectiveness of the proposed method was demonstrated experimentally.
Robot technology in medicineDohi, Takeyoshi
doi: 10.1163/156855393X00104pmid: N/A
Robot technologies widely used in the medical field are discussed, particularly the micro-surgery robot system and the computer-aided surgery (CAS) system, which have been developed in our laboratory. The micro-surgery robot system for corneal transplantation can measure and cut the cornea using an excimer or He-Ne laser. The computer-aided surgery system can simulate a pre-surgical operation for the surgeon's convenience. This system reconstructs a three-dimensional image from the image slices acquired from magnetic resonance imaging/X-ray computed tomography imaging devices. These medical robot technologies will contribute significantly to the various fields.