Abstract: A device with vertical buoyancy tanks fitted to its upper part is provided with rotors which generate horizontal and vertical propulsion, and which stirs the liquid uniformly as it moves freely through a liquid storage tank, thereby preventing the accumulation of sludge. The vertical buoyancy tanks stabilize the stirrer and provide a restoring force if the stirrer is upset. The stirrer is fitted with an ultrasonic wave emitter, and ultrasonic receptors are installed at several positions in the liquid tank. An ultrasonic pulse is emitted after a certain interval when the stirrer is at rest on the bottom of the tank. The position of the stirrer is computed for each pulse emission, and the average is taken to give the actual position of the stirrer.

Abstract: A device with vertical buoyancy tanks fitted to its upper part is provided with rotors which generate horizontal and vertical propulsion, and which stirs the liquid uniformly as it moves freely through a liquid storage tank, thereby preventing the accumulation of sludge. The vertical buoyancy tanks stabilize the stirrer and provide a restoring force if the stirrer is upset. The stirrer is fitted with an ultrasonic ultrasonic wave emitter, and ultrasonic receptors are installed at several positions in the liquid tank. An ultrasonic pulse is emitted after a certain interval when the stirrer is at rest on the bottom of the tank. The position of the stirrer is computed for each pulse emission, and the average is taken to give the actual position of the stirrer.

Abstract: A control system for a mobile robot calculates the instantaneous position of the robot, and sequentially stores data representative of the respective robot positions. The system studies and stores a range which the robot is to travel, and calculates a running pattern of the robot in the specific range. The robot is allowed to travel within the range without leaving any region untravelled in spite of the presence of obstructions which alters its path, while checking its own position. Also, the robot compensates for dislocations caused by slippage of its drive wheels or errors in the operation of its motors.