The V2Suit “down” tracking algorithm

The Variable Vector Countermeasure Suit (V2Suit) is a wearable intravehicular system that will provide a viscous resistance to movements that are parallel to a specified direction of `down.´ The V2Suit utilizes control moment gyroscopes (CMGs) in modules on the user´s limbs that are commanded to point the gyroscopic torque vector perpendicular to `down´ during movements. An algorithm has been developed to initialize the direction of `down´ and track the V2Suit module with respect to that direction using the output of an on-board inertial measurement unit (IMU). The `down´ tracking algorithm uses the angular velocity and linear acceleration outputs of the IMU to initialize and determine the direction of `down´ in the local module coordinate frame. This paper describes the algorithm for initializing the direction of `down´ for each of the V2Suit wearable modules, and the tracking of the module orientation and velocity with respect to that direction. IMU data from representative arm movements was collected and run through the initialization and `down´ tracking algorithms to quantify performance as a function of time. The performance of the IMU and algorithm combination is used to determine the operational duration before the system must be re-initialized. This work was funded by a Phase II award from NASA´s Innovative Advanced Concepts (NIAC) Program.