Modeling and control of a free-flying space robot interacting with a target satellite

In the thesis a unified control-oriented modeling approach is proposed to deal with the kinematics, linear and angular momentum, contact constraints and dynamics of a free-flying space robot interacting with a target satellite. This developed approach combines the dynamics of both systems in one structure along with holonomic and nonholonomic constraints in a single framework. Furthermore, this modeling allows considering the generalized contact forces between the space robot end-effecter and the target satellite as internal forces rather than external forces. As a result of this approach, linear and angular momentum will form holonomic and nonholonomic constraints, respectively. Meanwhile, restricting the motion of the space robot end-effector on the surface of the target satellite will impose geometric constraints. The proposed momentum of the combined system under consideration is a generalization of the momentum model of a free-flying space robot. A physical interpretation of holonomy/nonholonomic constraints is analyzed based on d'Almberts-Lagrange dynamics and reveals geometric conditions that generate such a behavior. Moreover, a nonholonomy criterion is proposed to verify the integrability of momentum constraints by using a linear transformation via orthogonal projection techniques and singular value decomposition. This criterion can be used to verify the holonomy of a free-flying space robot with or without interaction with a target satellite and to check whether these constraints or their initial conditions are violated. Based on this unified model, three reduced models are developed. The first reduced dynamics can be considered as a generalization of a free-flying robot without contact with a target satellite. In this reduced model it is found that the Jacobian and inertia matrices can be considered as an extension of those of a free-flying space robot. Since control of the base attitude rather than its translation is preferred in certain cases, a second reduced model is obtained by eliminating the base linear motion dynamics. For the purpose of the controller development, a third reduced-order dynamical model is then obtained by finding a common solution of all constraints using the concept of orthogonal projection matrices

Direct adaptive control for underactuated mechatronic systems using fuzzy systems and neural networks : a Pendubot case

This thesis describes the implementation of a vertical motion and position control scheme for a mechatronic system, specifically the Pendubot robot. The Pendubot is a non-linear, underactuated and unstable two-link planar robot arm that is frequently used as a benchmark in research studies involving nonlinear control theory and underactuated systems. Control of the Pendubot poses two challenging tasks: (i) to swing the two links from their stable hanging position to unstable vertical equilibrium positions, and (ii) to balance the links about the desired equilibrium positions. PD fuzzy controller is formulated and employed to meet challenges associated with swing-up control. Vertical balance control employs fuzzy systems and radial Gaussian neural networks. As such, an adaptive neural network and fuzzy controller is further analyzed, where the balance stability depends on a controller weight that is determined using Lyapunov theory. This approach is proven to be globally stable, with errors converging to a neighbourhood of zero. Then, the proposed swing-up and the balancing controllers are coupled together to achieve the motion objective in a stable manner, while resisting the external disturbances. The simulation results show that both the swing-up and balancing control schemes can be realized using 25 and 5 If-Then-rules, respectively. The simulation results confirm the results attained from the theoretical analysis