Leonardo's inspiration came from ancient Greek texts. Ctesibus (3rd century BC) produced the first organ and water clocks with moving figures. Hero of Alexandria (1st century AC) detailed several automata that were used in theater and for religious purposes. The Antikythera Mechanism (ca. 87 BC), an astronomical mechanical calculator, shows how sophisticated Greek mechanism technology had become. The Greek tradition was revived by Vitruvius (1st century BC), who described several automata and developed the canon of proportions, which is the basis of classical anatomical aesthetics. Arab authors also designed complex mechanical arrangements. Al-Jazari (1150?-1220?), for instance, illustrated several designs which also anticipated the principle of the modern flush toilet.
In approximately 1495, before he began work on the Last Supper, Leonardo designed and possibly built the first humanoid robot in Western civilization. The robot, an outgrowth of his earliest anatomy and kinesiology studies recorded in the Codex Huygens, was designed according to the Vitruvian canon. This armored robot knight was designed to sit up, wave its arms, and move its head via a flexible neck while opening and closing its anatomically correct jaw. It may have made sounds to the accompaniment of automated drums. On the outside, the robot is dressed in a typical German-Italian suit of armor of the late fifteenth century. On the inside, it was made of wood with parts of leather and metal and operated by a system of cables. This robot would influence his later anatomical studies in which he modeled the human limbs with cords to simulate the tendons and muscles.
The robot consisted of two independent systems: three-degree-of-freedom legs, ankles, knees, and hips; and four-degree-of-freedom arms with actuated shoulders, elbows, wrists, and hands. The visor, neck, jaw and possibly the spine may also have been actuated. The orientation of the arms indicates it was designed for whole-arm grasping, which means that all the joints moved in unison. A mechanical, analog-programmable controller within the chest provided power and control for the arms. To drive the arms, the controller had a cylindrical, grooved cam that triggered high-torque worm gears attached to a central pulley. A central shaft, perhaps splined, provided power while still permitting the robot to stand and sit. The legs were powered by an external crank arrangement driving the cable, which was connected to key locations in the ankle, knee, and hip.
Mark E. Rosheim