PURPOSE: To make a liquid produce its torque in all direction by controlling a magnetic field in a tank and an electric current flowing into a fluid in an inner part of the tank, respectively.

CONSTITUTION: Three magnetic field generating coils 1, 2, 3 generate a magnetic field in a direction optimum to generate torque in a spherical insulating tank 5, and a lot of electrodes 4 are set up on this tank 5. In addition, a controller 6 controls an intensity of magnetic field and its direction as well as an impressed voltage to eachy electrode 4 and polarity according to the torque direction to be generated and the magnitude of torque. A liquid in the tank 5 receives force based on a Fleming's left-hand rule from the magnetic field impressed by these magnetic field generating coils 1, 1, 3 and the voltage to be impressed in a direction being directed by the electrode 4. Owing to this resultant of force, the liquid gets turning effort in the tank, and thereby it functions as a wheel actuator, and it rotates in a desired direction and speed.