High-speed communication network for controls with the application on the exoskeleton

Our lower extremity exoskeleton is a wearable robotic device that enables a human to walk with a load for a prolonged period of time without reducing the human's agility. The exoskeleton comprised of two anthropomorphic legs and a spine. The device is designed and controlled autonomously via a spine mounted internal combustion engine and PC104 compliant computer. Custom hardware was designed to accommodate the high-speed network required to link the distributed sensors and actuators. This paper presents the implementation of the high-speed hard real-time network designed to maintain stable control of the exoskeleton during stance and walk. The high-speed ring protocol necessary to maintain strict hard real-time synchronization between the distributed sensors and actuator of the exoskeleton is presented. Communication latency was considered in the design with respect to its impact on performance, and stability. Error detection and recovery was crucial for operation with the exoskeleton. A cyclic redundancy check (CRC) algorithm was incorporated into the protocol to achieve this error detection. The use of this high-speed serial based network greatly minimized the number of cables required over traditional parallel-based systems. The achieved update time of up to 10 kHz for a six-actuator system enables the architecture to be viable system for most industrial controls.