A system including a flexible catheter configured to articulate along a degree of freedom. An actuator is disposed at a proximal portion of the flexible catheter. The actuator is configured to actuate the flexible catheter along the degree of freedom. An articulation sensor is configured to provide articulation sensor signals representing articulation of the flexible catheter. An actuator sensor is configured to provide actuator sensor signals representing movement of the actuator. A controller is coupled to the actuator and configured to, based on determining that a state of a first articulation sensor signal prevents or hinders the first articulation signal from being used as a feedback signal for controlling the actuator to: determine an articulation estimate of the flexible catheter based on a model of the flexible catheter applied to a first actuator sensor signal; and, control the actuator based on the articulation estimate.