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1 A quaternion-based attitude control system is developed for the X-33 in the ascent flight phase. A non-linear control law commands body-axis rotation rates that align the angular velocity vector with an Euler-axis defining the axis of rotation that takes the body-axis system into a desired-axis system. The magnitude of the commanded body rates are determined by the magnitude of the rotation error. The commanded body rates form the input to a dynamic inversion-based adaptive/reconfigurable control law. The indirect adaptive control portion uses on-line system identification to estimate the current control effectiveness matrix to update a control allocation module. The control allocation runs in a null-space injection mode that excites and decorrelates the effectors without degrading the vehicle response in order to enable on-line system identification. A direct adaptive control scheme uses the output of a neural network to compensate for dynamic inversion error. The overall system is designed to provide fault and damage tolerance for the X-33 on ascent. Preliminary results are shown to demonstrate the feasibility of the approach.
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Casting is one of the most widely used construction techniques. Complex geometries produced via computational design processes are not readily achievable through traditional rigid formwork and are subject to increased material waste. More suitable casting techniques are required to represent digital design output efficiently. This article presents a variable fabric formwork developed to work in conjunction with a 6-axis robotic arm for casting doubly curved panels based on hyperbolic paraboloid geometry. The variable formwork is designed to be extendable in length and width so that it can produce a wide range of outcomes within a single formwork. The interface established in the workflow allows the physical formwork and digital design to influence each other. The article concludes by discussing a verification method used to confirm the accuracy of the outcome. This variable fabric form-work reduces construction waste and is a more sustainable method for casting complex geometries.
Highlights Robotic arm used to manipulate a bespoke mould for fabric formwork casting. Constraints of mould design used to inform robotic arm of its fabrication limits. Workflow allows the physical formwork and digital design to influence each other. Verification of result reveals future area of research.
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