Abstract: A brushless direct current three-phase motor that is self driven and therefore does not require externally generated waveforms for its operation. The circuit connected to the motor is analog and reduces the complexity and present cost of the driver circuitry. There is no electronic commutation of the currents in the stator coils as is the case with other brushless motors.

Abstract: A table tennis practice system comprised of a robot and an enclosure or recycle net which catches balls returned by a player. The robot propels balls fed to it at a set rate so that a player on the other end of the table can receive practice similar to that between humans. The robot and recycle net are constructed so that the robot may be placed anywhere between the sides of one end of the table while simultaneously retrieving and recycling balls returned by a player. This lateral mobility of the robot permits serves from the corners of the table or any point between. Its recycle system does not rely on air movement for ball transportation, hence there is improved reliability. The timing system eliminates jamming when it can be caused by balls falling into the holes of perforated platters or notched wheels of timing devices at an in appropriate time.

Abstract: A table tennis ball projecting apparatus which can be used as the ball propelling mechanism of a table tennis robot. Its construction is such that balls entering its entrance port sequentially, will be ejected by a motor rotated rubber-rimmed thrust wheel. Two smaller rubber-rimmed wheels each on its own smaller motor, provide clockwise or counterclockwise spin on the ejected ball. The lighter spin-producing wheels and motors facilitate the production of rapid spin direction and magnitude changes on consecutively ejected balls thereby closely simulating practice between two humans.

Abstract: A table tennis robot with right and left servers, oscillatory motion, top spin and bottom spin, right and left side spin, combination of spins, or no-spin modes, variable ball speeds, and continuous recycling of balls, to provide a human player with challenging practice serves.A ball catching net is located at one end of the tennis table. Balls caught by the net fall into a pan located below the table and are then fed upward by suction of a fan into a chamber. The chamber distributes balls one at a time into a vertical tube. At its bottom, the tube has right and left branches. A ball deflecting vane is adjustable to selectively direct a ball into either the right or left branch. The branches lead, respectively, to a right server and a left server. Each server has a rotating ball drive wheel. The output port of the right server has adjustable guide rails to impart high top spin to a ball. The output port of the left server has adjustable guide plates to impart various types of spin to a ball.