Robotic fish with controlled bistable elastic propulsion system

A robotic fish, comprising:

• a) a head comprising a housing;
• b) a battery received within the housing;
• c) a controller received with the housing;
• d) an elastic spine comprising a fixed end mounted to the housing, and a free end;
• e) a complaint caudal fin connected to the free end of the elastic spine;
• and
• f) a parallel linkage mechanism comprising a first link and a second link;
• wherein a first end of the first link is pivotally connected to the housing;
• the first end of the first link adapted to pivot by a first servo motor secured to the housing;
• a first end of the second link pivotally connected to the housing;
• the first end of the second link adapted to pivot by a second servo motor secured to the housing;
• the first and second servo motors adapted to be driven by the controller;
• and
• wherein a second end of the first link and a second end of the second link are pivotally connected to each other, as well as to the free end of the elastic spine, to form a passive rotational joint;
• a motion of the caudal fin being determined by a moving trajectory of the passive rotational joint;
• and
• wherein the motion of the caudal fin is adapted to be switched between a monostable mode and a bistable mode.