Fluid rotating apparatus with plural drive motor synchronization system

A method for controlling rotation of rotors in a fluid rotating apparatus provided with a plurality of rotors accommodated in a housing, a plurality of rotary shafts connected to the rotors, bearings for rotatably supporting the plurality of rotary shafts, a fluid suction port and a fluid discharge port formed in the housing, a positive displacement pump section formed of a combination of the housing and the plurality of rotors, and a plurality of gears connected with the rotary shafts having a backlash set smaller than a backlash between the plurality of rotors, the fluid rotating apparatus further including motors for independently driving the plurality of rotary shafts, a rotation detecting means for detecting one of a rotating angle and speed of rotation of the motors, a motor controlling unit for controlling the motors to synchronously rotate, a motor current detecting unit for detecting a current running in the motors, a relative position detecting unit for detecting a relative position of the plurality of rotary shafts and a rotation commanding unit to which outputs from the motor current detecting unit and the relative position detecting unit are inputted,

• the method characterized by comprising the steps of:
• detecting a shift amount of the synchronous rotation of the plurality of rotary shafts based on the outputs of the motor current detecting unit and/or the relative position detecting unit;
• deciding by the rotation command unit whether or not the shift amount of the synchronous rotation of the plurality of rotary shafts is larger than a specified value;
• and
• decelerating one of the plurality of rotary shafts when the rotation command unit decides that the shift amount of the synchronous rotation of the plurality of rotary shafts is larger than the specified value.