Helicopter drones maneuver by adjusting the position of the blades, typically using mechanical linkages. ZHZ, an OEM manufacturer in China, wanted to replace the mechanical control assemblies, which are large, heavy, and complicated, with electromechanical technology. This would require high-power-density servo drives tough enough to survive the vibration and harsh operating conditions of diesel-driven flight. They found their solution in Elmo’s ultra-rugged ExtrIQ Gold Hornet servo drives.

Read this case study to learn about:

  • How high power density servo drives– rugged to endure the vibration and harsh diesel-driven flight– enable the replacement of large, heavy and complicated mechanical control assemblies, with electrometrical technology achieving outstanding motion control in harsh conditions, such as extreme temperatures and high vibration
  • Supporting a wide variety of feedback sensors

Machine Requirements

Helicopters generate lift when the blades turn through the air. Adjusting the angle of each blade changes the amount of lift generated, allowing vertical ascent and descent. This adjustment must occur on all blades simultaneously; so it is called collective control.

To change the tilt and roll of the aircraft, the entire plane of rotation of the rotor needs to be angled as a whole. The process requires continuous and independent repositioning of each blade as it cycles around the center mount of the rotor, known as cyclic control.

The new ZHZ TD220 helicopter drone has two rotors, each fitted with two blades and controlled by three motor-drive assemblies. One performs collective control (ascent/descent); the other two perform cyclic control (tilt and roll). It has a total weight of 140 kg and can carry payloads of up to 100 kg. Its cruising speed is 100 km/h.

The Elmo Motion Control Solution

  • 3 ExtrlQ Gold Hornet servo drives

Keeping precise control

Fast, accurate feedback is essential to proper blade positioning. The ExtrIQ Gold Hornet drives are compatible with the resolver feedback used by the ZHZ design. The drives support a wide range of feedback devices, from digital to analog, incremental to absolute, and so would be able to work with any encoder type the design team might adopt in the future.

The ExtrIQ Gold Hornet drive supports EtherCAT or CANopen (CAN or RS232; optional RS422) Fieldbus networking for high-speed, deterministic communications between the drive and the controller. This supports the rapid adjustment of blade positions, for example during takeoff/ascent or landing/descent. In this application, the controller interrogates the drives over the CAN bus to get position and velocity data, and then sends back the motion commands. With a cycle time of 2ms, the drives maximize the performance and maneuverability of the aircraft.

Designed for harsh environments

The diesel engines used to turn the rotors generate large amounts of continuous vibration at 10 Hz. The aircraft may also undergo shock events of up to 4G during landing. The components are subjected to temperature swings, wind, and precipitation, and sometimes corrosive salt air.

G.Y. Tian, general manager of ZHZ, pointed to the environmental toughness of the ExtrIQ Gold Hornet drives as one of the top reasons for choosing them. “The Hornet drives ensure the system can work very well in these harsh conditions.”

Power and efficiency

ExtrIQ Gold Hornet drives are built to tolerate variations in input voltage, eliminating the need for an external shunt. “Due to the battery, the voltage range of the TD220 is very wide,” says Tian. “The Elmo drives ensure that the system can operate over such a wide voltage range without any malfunction.”

Also, “the small form factor is very important and significant to shrink the size of cabinet and weight,” says Tian.

The outcome

The ExtrIQ Gold Hornet drives have helped ZHZ produce a successful rotary UAV. “They match our target for the control system, and we are very happy with the results,” says Tian.

The Elmo team worked closely with ZHZ during implementation. Elmo’s applications engineers helped with customizing the firmware of the drive to make it 99.6% efficient. “We are very satisfied with Elmo’s after-sales service,” Tian says. “The applications engineers gave us very powerful help in a short timeframe.”

The TD220 rotary UAV has moved into production with a strong market response. Elmo is assisting ZHZ in a new product with the Elmo Gold Drum drives.