Application of discrete time sliding mode control to a spacecraft in 6DoF with parameter identification

There is a substantial amount of literature within the field of spacecraft control which deals with the separate issues of position and attitude control; comparatively little work has been carried out on the joint nonlinear problem of spacecraft position and attitude control. (R.Pongvthithum etal 2005, H.Wong etal 2001, S.M.Veres etal 2002) provide control solutions for spacecraft position control, where the task is to follow a leader spacecraft. (R.Pongvthithum etal 2005) applies the universal adaptive control approach and (H.Wong etal 2001) uses a continuous time Lyapunov stability based approach in conjunction with disturbance estimates to facilitate tracking of a reference trajectory with unknown spacecraft mass. (S.M.Veres etal 2002) explores a discrete time constrained control method for stabilization and control of two nano-satellites using time optimal control but, similarly to (H.Wong etal 2001), is only applied to position control. (O.Hegrenaes etal 2005) uses quadratic programming to solve a constrained, linear model predictive control problem in a discrete time environment. Within the analysis, the author makes use of Euler angles for attitude specification; which although may be more intuitive for visualization, does not offer the robust benefit of the quaternion method implemented within (J.T.Wen and K.KreutzDelgado 1991) and (F.Lizarralde and J.T.Wen 1995). (F.Terui 1998) presents a combined sliding mode controller for an individual satellite, controlling both attitude and position in the presence of zero disturbance, without guidance and within a continuous time environment. A related paper (O.Junge etal 2006) presents a scheme for both attitude and position control applied to a group of satellites operating in Lagrange point conditions, using a trajectory optimization process based on minimizing a fuel cost function across the satellite group. Alike (F.Terui 1998), the control scheme is based within a continuous time environment. Integration of potential function guidance methodologies with continuous time sliding mode control has been proven suitable for distributed control of large scale satellite swarms: this method was initially conceived by (V.Gazi 2003, Gazi 2003) and subsequently expanded within