MIMO TRMS Modelling and Control

The object is to develop the appropriate software to simulate and control the laboratory helicopter system Twin-Rotor Multiple Input-Multiple Output System (TRMS 33-220), manufactured by Feedback Instruments Limited Company.

For that purpose, the employed hardware must fulfil a well define group of specifications:

- Hard Real Time behaviour.
- Embedded platform.
- Multiple Digital I/O.
- Multiple D/A and A/D converters.
- User Interface capability.

PXI controllers from National Instruments provide a robust environment to develop embedded control systems with the specifications enounced before. In this work, the selected PXI technical characteristics are listed below:

- PXI 1002: 4 slots industrial chassis.
- PXI 8145RT: real time control target.
- NIDAQ 6025E: general purpose acquisition target.
- NIDAQ 6713: analog outputs target.

From a control point of view, the system consists of two inputs and two outputs that are hard-coupled to each other. First effort was to build up the non-linear model by measuring the particular parameters of the system by several experiments, and describing the system by physical equations. Finally, a non-linear state-space-system of 6th order was obtained.

Control design was done in continuous time domain, using the well-known LQR-method based on the linearised version of the original model. Obviously, controller was designed continuously, afterwards was transformed to discrete domain. To control this complex system moreover a Luenberger-Observer was used, which was also firstly designed in continuous domain and afterwards transformed to discrete domain.

Having done these preparations, both the modelled system and the controller was transferred to the PXI-1002. The PXI-1002 used in this case was also equipped with two measurement cards (6025E and 6713) to deal with analog inputs and outputs. Hence in a real-time-loop using a sampling rate of 20 ms the non-linear model and the designed control were implemented. Firstly the controller and the model were connected to each other using general variables within the loop. After successful testing the connections were substituted by physical connections using the measurement cards.
During these pre-tests, the PXI controlled by Labview turned out as a benefit as the particular states both of the observer and the model could be monitored in real-time. This made it quite easy to modify final details concerning the controller and the observer.
Having reached satisfying results of the test, finally the PXI was connected to the helicopter model controlling it in real-time.

Load TRMS Parameter in Matlab Workspace
TRMS Simulink Linear Model
TRMS Simulink Non-Linear Model
Plot Simulink results
Control Framework Article
PID Controller under LabView 2009
State-Space Controller under LabView 2009