Differential lock actuator systems and methods for moving flight control surface

A differential actuator system for controlling a flight control surface, the system comprising:

• a first control lane subsystem including a first motor for rotating a first drive shaft and a first brake operably coupled to the first motor and configured to control rotation of the first drive shaft;
• a second control lane subsystem including a second motor for rotating a second drive shaft and a second brake operably coupled to the second motor and configured to control rotation of the second drive shaft;
• a differential subsystem including:
• a first compound planetary gear set having a first sun gear driven by the first drive shaft, a first planet gear configured to control the flight control surface, and a first gear train operably coupling the first sun gear to the first planet gear, wherein the first compound planetary gear set forms a first load path from the first control lane to the flight control surface;
• a second compound planetary gear set having a second sun gear driven by the second drive shaft, a second planet gear configured to control the flight control surface, and a second gear train operably coupling the second sun gear to the second planet gear, wherein the second compound planetary gear set forms a second load path, separate from the first load path, from the second control lane to the flight control surface;
• a differential lock subsystem operably coupled to the first compound planetary gear set and the second compound planetary gear set, wherein the differential lock subsystem includes:
• a gear coupling between the first compound planetary gear set and the second compound planetary gear set;
• and
• a third brake operably coupled to the gear coupling;
• a controller configured to send control signals to the first and second control lane subsystems and the differential lock subassembly for operating the differential actuator system, wherein the controller is configured to send a first set of control signals for engaging the third brake and disengaging the first and second brakes for operating the differential actuator system in a torque-summing mode and to send a second set of control signals for disengaging the first, second and third brakes for operating the differential actuator system in the velocity-summing mode.