Continuous bounded controllers for active control of structures

This paper considers nonlinear controller under bounded capacity of the actuators. The controller is first derived based on bang–bang type controllers. In order to avoid high-speed switching effect, a continuous function is used to replace signum function in bang–bang controller. Although a variety of continuous and bounded functions are available, a hyperbolic tangent is chosen as the candidate of the controller. The proposed control law is then applied to three- and six-storey buildings utilising active bracing systems. Different earthquake excitations with various intensities are used in the simulation to show the potential benefit of the proposed control law. Numerical results show that in contrast to bang–bang type controllers that utilise maximum capacity of the actuator, the proposed controller is adaptive in the sense that the maximum capacity of the actuator is utilised when only needed. In addition, the proposed controller can avoid the high-speed switching effects presence in the bang–bang controllers if the weighting variables are chosen appropriately.