A rotary actuator is provided which includes a crankshaft, a first eccentric gear disposed on a first end of the crankshaft, a second eccentric gear disposed on a second end of the crankshaft, first and second end plates, a first crosslink disposed between the first eccentric gear and the first end plate, and a second crosslink disposed between the second eccentric gear and the second end plate. The first crosslink has a first set of surface features on a surface thereof which engage a second set of surface features on the first eccentric gear, and at least one of the first and second eccentric gears is equipped with circular arc gear teeth.