The initial effort for Spidernaut's design called for a demonstrator model which would illustrate some of the capabilities of the concept using off the shelf components and simple construction. A single-leg test bed allowed the engineers to perfect leg kinematics and walking capabilities ahead of time, while the later two-leg prototype facilitated testing of software and onboard electronics. The two leg model, combined with an additional wheeled support structure, used linear actuators in a 3 DOF design which could support 100 lbs per leg pair.
The prototype legs were designed around several requirements:
- no discrete foot fall locations
- low applied forces
- design simplicity
While the design performed admirably, a few factors were identified for improvement before buildup of the 8 legged Spidernaut. These included reducing the hip actuator packaging and eliminating flex between the leg and connecting structure.