A basic onboard setup consists of an internal combustion engine, a brushless electric motor attached to the engine, an onboard battery with a BMS and a Servosila SC-series controller acting as both the electric motor's driver and an electric power converter. The electric motor needs to be equipped with either Hall Sensors or an encoder.

Upon receiving a command from a control computer/autopilot, the Servosila controller drives the electric motor to start up the internal combustion engine. Once the engine is started, the electric motor becomes a three-phase power generator driven by the engine. The Servosila controller then turns itself into an inverter that converts the three-phase AC power into a regulated DC power for onboard payloads, while also charging the battery.

Servosila SC-series controllers receive commands and return telemetry via a CAN/CANopen network interface. A USB interface is also available for ease of configuration on the ground.

Servoscope, a software tool that accompanies all SC-series motor controllers, has been improved with simulation capabilities related to the starter-generator application. The tool helps select an electric motor that matches performance profile of the internal combustion engine as well as onboard payloads.

Furthermore, if an encoder is available in the setup, a range of advanced applications becomes available. For example, in a hybrid power application, an electric motor could be used to assist a piston engine during fuel-mixture compression strokes, while extracting the power during fuel burning strokes. It becomes possible to rotate the propeller into a safer position for engine-off landings.

A Servosila "Engineer" robot fetches a coffee at a research lab. The robot is a 9 years old machine and is still in an active use.

Servosila recently completed a challenging project called "Tracking Telescope" that we would like to tell about.

A customer, an established telescope manufacturer, required a very high precision of motion control at very low speeds for a two-axis direct-drive telescope fixture. The fixtures are equipped with Servosila SC-25C servo drives and Renishaw 26bit optical encoders.

The telescopes are about 2meters long and are pretty heavy due to powerful optics. The positioning tolerance requirement is ~1.0 arc-second which calls for about 21bits of effective positioning accuracy with the 26bit encoders.

Furthermore, since celestial objects keep moving, this accuracy has to be maintained while tracking objects moving at speeds of up to 2.0 degrees per second. This corresponds to RPMs in the range of Zero to 0.30 RPM. Moving at such low speeds is a challenge in its own right.

An extensive use of Servoscope simulation software helped identify an envelop of configuration parameters that allowed the SC-25C servo drives to meet or exceed the tolerance requirements as well as the tracking performance requirements. It took a clever application of Velocity Feed Forward Signal in a PID loop to make such tracking possible.

We are soon publishing a technical paper that records the experiences and details a tuning procedure for Servosila SC-25C servo drives that resulted in the required performance.