Multi-rotor synchronous machine permitting relative movement between rotors

A multi-rotor synchronous machine, comprising:

• a pair of rotors at least one of which has permanent magnet field poles, said rotors being arrayed coaxially to be rotatable relative to each other;
• a stator core;
• armature coils wound in said stator core, interlinking with a field flux produced by said rotors;
• a sensor measuring a relative angle between said rotors;
• and
• a rotor-to-rotor relative angle controller working to establish a relative rotation between said rotors to change the relative angle measured by said sensor to a target angle,
• wherein:
• said stator core is made of a hollow cylindrical member,
• said rotors are an outer rotor disposed around an outer periphery of said stator core and an inner rotor disposed around an inner periphery of said stator core,
• said rotor-to-rotor relative angel controller includes a relative rotation controlling mechanism disposed inside said inner rotor for controlling a relative rotation between said rotors,
• said relative rotation controlling mechanism includes an elastic member laid between said rotors in a circumferential direction thereof to keep said rotors in a neutral position, and
• said rotor-to-rotor relative angle controller changes magnetic torques acting on said rotors to adjust a relative angle between said rotors to a target angle.