This paper details the design and architecture of a series elastic actuated snake robot, the SEA Snake. The robot consists of a series chain of 1-DOF modules that are capable of torque, velocity and position control. Additionally, each module includes a high-speed Ethernet communications bus, internal IMU, modular electro-mechanical interface, and ARM based on-board control electronics.

The design of a hyper-redundant serial-linkage snake robot is the focus of this paper. The snake, which consists of many fully enclosed actuators, incorporates a modular architecture. In our design, which we call the Unified Snake, we consider size, weight, power, and speed tradeoffs. Each module includes a motor and gear train, an SMA wire actuated bistable brake, custom electronics featuring several different sensors, and a custom intermodule connector. In addition to describing the Unified Snake modules, we also discuss the specialized head and tail modules on the robot and the software that coordinates the motion.

The bow leg hopper is a novel locomotion design with a highly resilient leg that resembles an archer's bow. During the flight a "thrust" actuator adds elastic energy to the leg, which is automatically released during stance to control hopping height. Lateral motion is controlled by directing the leg angle at touchdown, which determines the angle of takeoff or reflection. The leg pivots freely on a hip bearing, and is automatically decoupled from the leg-angle positioner during stance to preclude hip torques that would disturb body attitude. Upright attitude is maintained without active control by allowing the body to "hang" from the hip joint. Preliminary experiments with a planar prototype have demonstrated impressive performance, high efficiency, and low power requirements. Current experiments are focused on developing control and planning schemes to enable locomotion over discrete "stepping stones" and obstacles.

The bow leg hopper is a new design for a locomotion system with a resilient, flexible leg. It features a passive stance phase and natural pitch stability. It is controlled by actuators that configure the leg angle and stored leg energy during flight. During the stance, the actuators are mechanically decoupled from the leg and the stored energy is released. The trajectory is determined by the spring-mass physics and the state of the leg at impact. This design casts the controller as a function mapping three trajectory parameters to two control outputs once every hopping cycle. Our particular solution uses a combination of graph-search planning and feedback control. The planner searches the sequences of foot placements and computes control outputs using numerical solution of a physical model. The feedback control is computed once per bounce. Experimental data from a planar prototype are included demonstrating navigation of simple artificial terrain.

Mixed-signal testing requires exact synchronization between digital and analog clock domains. A unique ASIC, the CAT, has been developed to automate the vector handoff for analog instrument control and synchronization, while producing arbitrary precision analog clocks.

A unique lossless data compression algorithm has been implemented into a Bitmap Display Processor. This scanner hardware will allow massive non-lossy compression of bitmap failure images on the order of 10000 to one. The capability should allow new opportunities for testing speed and qualities, with small file sizes and fast image updates.