Abstract: The nonlinear dynamical model of the planar double inverted pendulum is developed with Lagrangian formulation firstly. Then, the linearization of the model at its equilibrium yields to the decoupled linear systems of the inverted pendulum in two perpendicular control directions. Both of the two systems consist of positioning subsystem of the base cart and balancing system of the poles. For each direction, the adaptive sliding mode fuzzy control approach is developed. Finally, the circular motion of the base cart is implemented while keeping the pole balance, which validates the effectiveness of the adaptive sliding mode fuzzy control strategy in underactuated, unstable, and multi-variable coupled system.