Supervisory Controller to Prevent Damage to 3 Degrees of Freedom (3DOF) Helicopters


  • Safety controller for 3-Degrees of Freedom (3DOF) helicopters
  • Remote laboratory to enable online coursework in control systems 

Problem Addressed

3DOF helicopters enable users to select both the velocity and elevation angle, and are an example of the type of control systems problem studied in introductory engineering classes. 3DOF helicopters are useful educational tools, but their adoption has been limited because they are easily damaged.


The supervisor software consists of the initialization controller, the landing controller, the simulation module, and the system controller. The supervisor operates in three phases: initialization of the plant, real-time monitoring of the plant with lookahead simulation, and landing of the plant after the user is finished with the experiment. The user-defined controller is activated only during the simulation phase, which is between the plant initialization and landing phases. Once the user's controller is turned on, the plant monitoring is achieved through a real-time lookahead simulation of the dynamic response of the closed-loop system, which runs in parallel with the user's controller. At each time step, the simulation takes as inputs the current system states and simulates the closed-loop dynamic response for a certain lookahead time. The closed-loop system simulation consists of a system model linearized over an appropriate trim state and a system controller whose command is to bring the 3DOF helicopter to the nearest trim state as possible. If the simulation predicts that the plant has entered the unsafe region sometime during the lookahead time, the supervisor overrides the user's control inputs. The controllers used in the lookahead simulation are the actual controllers the supervisor would use should he/she decide to override the user's commands.


  • Improves safety for 3DOF helicopters, reducing maintenance costs
  • Predicts the helicopter’s future position and only removes control in the case of a potential crash, so the user experience is not compromised
  • Enables remote control, making products appealing for use in distance learning laboratories