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Example: LAPAZ - actuator electronics for a flight control system (avionics)

Stemme AG (Strausberg) developed a flight control system (with full control authority) in the project LAPAZ. Our contribution is the actuator electronic equipment. The key data are: 28 VDC, 15 A.

The electronic unit communicates via CAN bus (CANopen) with the flight control computer and drives an electronically commutated brushless servo motor. The position sensor is a resolver. Besides the key function of controlling the position of the motor there are numerous protective and safety features to ensure a robust operation and a safe flight. An important feature is the two-staged brake chopper which absorbs the regenerative energy (control surface with actuator driven by heavy gusts). To achieve a reliable design the actuator was tested to analyse the operation of the driven motor. With these measurements we conducted a simulation campaign with real gust signals to investigate the selection of the chopper resistors (resistive value and wattage).

The protective features are well beyond the requirements outlined in RTCA DO-160 and ensure a robust operation, especially (as in this case) in a research program.

General layout

The components of the electronic unit are grouped around the key part: the servo module. It drives the brushless servo motor (BLDC). The operation in a high reliability research program needs various protective features, especially for the tests during gusts.

View to the side of the power connectors

The connections for the power supply and the flight control system are in two D-sub connectors on one side.

View to the side of the actuator connectors

The connections for the actuator is on the other side, also with D-sub connectors. Here are the three connectors for the motors phases, the commutation resolver and the safety clutch.