Abstract: Systems and methods of controlling instruments include first and second actuators configured to actuate a degree of freedom (DOF) in first and second directions using respective transmission mechanisms and a control unit. The control unit is configured to determine positions of the first and second actuators; determine an actuation command based on the positions of the first and second actuators, and a desired state of the DOF; determine respective actuation levels of the first and second actuators so as to maintain tensions in the transmission mechanisms above respective minimum tensions by: using a model based on the force or torque command, the minimum tensions, and the first and second actuator positions; and command actuation of the first and second actuators at the respective actuation levels. The model compensates for an external disturbance on the DOF and for dynamics of the first and second actuators.

Abstract: Systems and methods of dithering to maintain grasp force include a computer-assisted device. The computer-assisted device includes an instrument having a first jaw and a second jaw configured to grasp a material, one or more actuators configured to actuate the first and second jaws to apply force to the grasped material, and a controller coupled to the one or more actuators. The controller is configured to determine that actuation of the one or more actuators should be dithered and in response to the determination, dither one or more control signals to the one or more actuators so as to cause variations in a force or torque applied by the one or more actuators. In some embodiments, the one or more control signals correspond to a force setpoint, a torque setpoint, a current setpoint, or a position setpoint for the one or more actuators.