Design of a linear observer for the thrust force in 1D

BSc assignment


In the theory of control of UAVs, the thrust force  generated by a propeller is typically modeled as a function of the spinning rate depending on a constant .

However, in multi-rotor vehicles with mutual interaction between propellers, this model may not be satisfactory. The airflow of adjacent propellers affects the thrust that a propeller can generate, resulting in lower thrust than without cross-influence.
Predicting thrust loss is a crucial issue in the control and design of multi-rotor UAVs. To investigate this phenomenon, a reasonable approach is to collect force measurements from sensors mounted on a multi-rotor structure and use them to validate more realistic model proposals.


The force sensor's measurement will differ from the actual measurement by a constant term. This assignment aims to use classical control theory to observe the bias term without directly measuring it. The student will work on a simplified 1D problem with only one propeller. The force sensor is modelled as a spring and a damper, while the motor and the load are considered to be two point masses.


The assignment comprises three questions. Once the student has obtained the associated state space representation of the system, the questions are formulated as follows: 

  • Can the full state be reconstructed without measuring the bias term?

  • If so, what is the minimum set of measurements required?

  • If possible, build an observer and show it works in simulation

• As an extra task, is it possible to develop a control action  that will cause the output to asymptotically converge to the desired trajectory for the load mass?