The goal of this work is to address challenges with developing and utilizing mobile powered orthotic devices or exoskeletons, especially those that depend on miniature pneumatic power systems. We present an ongoing research testbed to explore hardware and software solutions related to effective, efficient control and operation of such devices. The testbed platform is a pneumatically-powered ankle-foot orthosis that can provide bidirectional (dorsiflexor, plantarflexor) torque. A mobile pneumatic power source can be used to examine issues related to providing gait assistance in a variety of environments beyond walking on a treadmill or confined level-ground space. We refer to this platform as the Portable Powered Ankle-Foot Orthosis (PPAFO) (Fig. 1) [1].