Spidernaut's avionics are a sophisticated set of custom brushless DC (BLDCs) motor controllers and a power and data distribution network. Located in Spidernaut's thorax are the four motion control modules (MCM). Each MCM consists of six, custom one-axis 500V/20A BLDC motor controllers for operating two of Spidernaut's legs. Each MCM contains two FPGAs for hall data and provides the six step commutation sequence for the BLDCs. The FPGAs also accumulate each motor's encoder data which is shipped upstream on an RS-485 bus to the brainstem for motion control.
The feet of Spidernaut are modular as well, allowing for different shoes to be design for the required application. Each leg weighs 40lbs and is capable of exerting forces greater than 250lbs. The strength of the legs can be augmented by the addition of coil springs around the top linear actuator and extension springs across the lower linear actuator, increasing the strength while minimally increasing its weight.
Each leg has three Degrees of Freedom (DOF) the first is the hip it is a simple rotary joint. The other two DOF are also rotary joist but linear actuators actuate them. This configuration allows for the placement of the foot in space, but does not have a means of independently controlling the angle of the foot. Presently this is taken care of by a passive spherical joint at the foot.
Located at the aft end of the spider is the main power source which is a custom built 72V/3600 Watt-hr lithium ion battery unit that incorporates individual cell health monitoring to ensure balanced discharging. The Li-Ion battery feeds a Power Conditioning and Distribution Module (PCDM) which down-converts Spidernaut's 72V main bus into all the necessary voltages for computer power and all peripheral devices. The PCDM also allows for an off-board 'hot-swappable' AC unit to power Spidernaut when the batteries are unavailable.