How Disney built and programmed an animatronic president (2014)

An increase or decrease in voltage was used to activate the more complex types of movement in animatronic figures, according to Persistence of Vision. The harness measured voltage differences across its various joints and mimicked the changes in the animatronic figure connected to it, recording the movements to tape. The animatronic Lincoln used both types of motion, though because of maintenance and space constraints, the actual materials used to execute the necessary motions were improved between the time Disney first started developing animatronics and when the figure debuted.

Source: arstechnica.com