Attitude stabilization of slender payloads in partial space elevator transport by super-twisting sliding mode control

This work develops the rigid-flexible coupled dynamic model of a partial space elevator transporting a slender structural payload by the climber during cross-orbit payload transfer. The payload is modeled by Euler–Bernoulli beam theory, and analysis shows that even small bending deformation of the payload can induce large attitude motion of the climber-payload assembly due to strong orbit-rigid–flexible coupling. To quantify this behavior, a closed-form expression is derived for the steady bending deformation of the payload under the gravity-gradient effect. Building on this analytical insight, a nonlinear compensation control torque is formulated to suppress attitude motion caused by rigid–flexible coupling without requiring impractically large control torques. To enhance control robustness, a super-twisting sliding mode control scheme is proposed by embedding the forward control law within a Lyapunov stability framework. This combined strategy eliminates residual dynamics and reduces the chattering inherent in sliding mode control while ensuring global attitude stability. Numerical simulations verify that the proposed strategy significantly reduces the attitude excursions of the climber-payload assembly while keeping the required control torques within the capacity of reaction wheels on the climber (rigid body). Overall, this work establishes a nonlinear dynamic framework for tethered transport systems with slender structure payloads and provides the first validated control solution enabling safe, stable, and efficient operation of partial space elevator transporting slender structure payloads. • Established rigid-flexible coupling dynamics of PSE with slender structure payload • Found small payload deflection induced large attitude of climber-payload assembly • Estimated steady-state bending of slender structure under gravity-gradient effect • Formulated nonlinear compensation torque for rigid-flexible coupling effect in PSE • Proposed ST-MPC based on compensated rigid-flexible dynamics