Drones and gimbals - encoders elevating aerial precision

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Drones and gimbals - encoders elevating aerial precision

The rise of drone applications has significantly increased demand for highly accurate and lightweight gimbals. Gimbals enable drones to accommodate a variety of payloads for a range of technologies and use cases.

The vital role of encoders in drone and gimbal applications

A banner of various Renishaw position encoders, including optical encoders and magnetic encoders.jpg

High-precision encoders play a vital role in drone and gimbal applications by providing accurate feedback on movement, orientation, and stabilisation. Here's how encoders are used in drones and gimbals:

Drones

1. Flight control

Maintaining a drone's stability in the air requires precise control over the aircraft's motors. Drone motor controllers therefore use high-precision encoders which provide real-time feedback on the motor's rotational position. This feedback allows the flight controller to adjust motor speeds and angles, in order to maintain stability, hover accurately and navigate smoothly.

The AksIM™ non-contact off-axis rotary absolute magnetic encoder is designed for applications with limited installation space.

An operator flying a drone which designed for sites surveying.jpg

Illustration of a drone designed for sites surveying and area inspection.jpg

A drone designed for surveying sites

2. Navigation and positioning

Drones often use global navigation satellite systems (GNSS) for positioning, but these systems can have errors. High-precision encoders can be integrated with the drone's onboard sensors to provide additional data for higher-accuracy positioning, especially during periods of weak or intermittent satellite signal strength.

3. Cargo control

Depending on their application, drones often need to carry cargo, such as a camera for aerial photography. High-precision encoders can be used in gimbal systems (see next section) to stabilise the device and ensure that the camera remains steady for the capture of high-quality imagery.

A delivery drone is an unmanned aerial vehicle (UAV) transporting packages.jpg

A delivery drone is an unmanned aerial vehicle (UAV) used to transport packages that include medical supplies, food, or other goods

Gimbals

1. Camera stabilisation

In gimbal systems, which are used to stabilise cameras or other payloads mounted on drones, vehicles, or handheld devices, high-precision encoders are placed at the joints of the gimbals' three axes (pan, tilt, and roll). These encoders measure the angles and rotational positions of the axes with exceptional accuracy.

Illustration of a gimbal camera equipped with a Renishaw RESOLUTE absolute encoder readhead and encoder scale, demonstrating rotation along the elevation and azimuth axes..jpg

A gimbal camera fitted with Renishaw RESOLUTE absolute™ encoder systems

The RESOLUTE™ true-absolute encoder is a high-speed, fine-resolution position measurement system where position is acquired instantly without the need for any motion. RESOLUTE™ measures angles and rotational positions along the elevation and azimuth axes in a gimbal camera with exceptional accuracy.

2. Smooth motion

The encoders provide real-time feedback to the gimbal's control system. This information is used to calculate and execute precise counter-movements that offset any unintended vibrations or movements, resulting in smooth and stable footage or payload orientation.

3. Panoramic photography

Encoders help gimbals execute precise panoramic shots by accurately controlling the rotation of the camera along the horizontal axis, ensuring seamless stitching of images.

A camera rotating along the horizontal axis to capture panoramic photos.gif

4. Target tracking

Some gimbals can track specific objects or points of interest. Accurate encoders provide the necessary data to keep the camera focused on the tracked target, even when the gimbal itself is moving.

5. Remote operation

Gimbals can be operated remotely, allowing the user to control camera movement from a distance. Encoders ensure that the camera responds accurately to the flight controller's commands.

Where can you find gimbals?

Gimbals are prevalent in unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), and unmanned ground vehicles (UGVs), playing crucial roles in diverse industries.

From agriculture and surveillance to photography, filmmaking, search and rescue, oceanographic research, environmental monitoring, to industrial inspection, unmanned vehicles benefit from the stability and precise control provided by gimbals.

An unmanned aerial vehicles (UAVs) and an unmanned surface vehicles (USVs).jpg

An unmanned aerial vehicles (UAVs) and an unmanned ground vehicles (UGVs).jpg

Unmanned aerial vehicles (UAVs), unmanned surface vehicles (USVs), and unmanned ground vehicles (UGVs)

Radar

Radar relies on rotation to scan and determine the position, speed, and distance of objects. To ensure accurate object detection, an encoder serves as a feedback system, supplying real-time information about the angular position of the radar's rotating antenna. Continuous rotation enables the radar system to cover a wide area and detect diverse objects.

The encoder functions as a positional feedback system for the rotating antenna, delivering precise information about its angular position during rotation. This data allows the radar system to ascertain the antenna's exact orientation at any given time, which is crucial for precise calculations of the position, speed, and distance of detected objects.

Where can you find radar?

Radar application in maritime navigation and aviation.jpg

Radar application in maritime navigation and weather prediction.jpg

Radar technology is widely utilised in aviation, air traffic control, weather monitoring/prediction, maritime navigation, and space exploration

What to consider when selecting encoder systems for drones and gimbals?

The table below outlines the key factors typically evaluated when choosing an encoder system for precision stages. These factors include encoder performance, environment conditions, installation requirements, and other relevant considerations.

Drones and gimbals

Performance

✔ Resolution
✔ Sub-divisional error
✔ Rotary range
✔ Controller input frequency
✔ Readhead mass
✔ Cable flex radius

Environment

✔ Temperature
✔ Humidity
✔ Vibration
✔ Electromagnetic compatibility (EMC)
✔ IP rating

Installation

✔ Size
✔ Ride height tolerance
✔ Yaw / pitch / roll
✔ Connectors

Others

✔ Protocol

Success stories: pan and tilt

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RF antenna systems – combat the vibration on a Blackhawk

Pacific Antenna Systems (PAS) designs, fabricates and manufactures state-of-the-art antenna systems that use radio frequencies (RF) ranging from 1–110 GHz. Applications include high-resolution radar, high-rate data communications for line-of-sight and satellite (SATCOM) communications, and high-power microwave systems for drone (UAS) countermeasures.

The basic principle of an antenna is the accurate positioning of an RF beam on a target. PAS utilizes several different electro-mechanical designs for its antennas, depending on the application. Rotary position encoders are installed on each motion axis (gimbal) to provide the required precision and accuracy.

UH60 Blackhawk helicopters flying in the sky.jpg

RESOLUTE™ true-absolute encoders have been flown on UH60 Blackhawk helicopters, where the vibration environment is extremely challenging, as part of the collision avoidance radar.

Product shot of a Renishaw Resolute encoder.jpg

Pacific Antenna Systems antenna gimbal assembly on a shock and vibration test stand.jpg

PAS antenna gimbal assembly on a shock and vibration test stand

We need repeatability within a thousandth of a degree. We must test all components on these assemblies due to the significant nature of the applications.

RESOLUTE™ more than exceeds our requirements.

Pacific Antenna Systems (USA)

Astronomical research - telescope precision in desert environments

The Wise Observatory is an astronomical research facility owned and operated by Tel Aviv University. Located in Israel's Negev desert, the observatory has been supporting cutting-edge astronomical research for over 40 years.

Tel Aviv University's telescope is fully robotic and equipped with a very high-resolution spectrograph to discover planets around known stars. Encoders are attached to the telescope's axes to sense the position of the telescope as it moves.

The Wise Observatory is an astronomical research facility owned and operated by Tel Aviv University. Located in Israel's Negev desert..jpg

One-metre main telescope at the Wise Observatory

The temperature in the desert can change drastically. These varying temperatures can negatively impact metals, as they expand and contract with temperature changes.

When designing the bespoke mounting brackets to attach the new encoders to the telescope, we had to account for thermal expansion to ensure that weather conditions did not impact the accuracy of the telescope.

Wise Observatory (Israel)

The team installed the RESOLUTE™ linear encoders to each axis of the telescope. The roll axis controls the orientation of the telescope, which is used to view different areas of sky, while the pan axis controls the side-to-side movement of the lens and camera. Ultra-low Sub-Divisional Error (SDE) and jitter result in a linear encoder system that outperforms any other encoder in its class.

Virtual reality – the beauty of vision technology

Virtual reality (VR) technology relies heavily on camera positional data for perfect synchronisation between virtual and physical elements in real-time broadcasting. This is why camera support equipment manufactured by Hong Kong-based Power Plus depends on the accuracy and repeatability provided by Renishaw encoders.

A cameraman holding a camera for real-time broadcasting.jpg

Power Plus’s camera support equipment depends on the accuracy and repeatability provided by Renishaw encoders.

Compared with the use of traditional enclosed encoders, the non-contact encoder has excellent repeatability and with zero backlash, which is critical for VR performance.

We are very satisfied with Renishaw's encoders which are built for precision.

Power Plus (Hong Kong)

Power Plus’s high-precision pan-tilt head and jib employ Renishaw's incremental rotary encoder system on both the pan and tilt axes, with a non-contact optical readhead offering repeatability to 0.004 arc seconds.

Recommended solution: QUANTiC™ incremental encoder with RESM scale.

Recommended solutions

Drones and gimbals

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For electric vehicles (EVs)

AksIM™ absolute magnetic encoder

A non-contact high-performance off-axis absolute rotary encoder designed for applications with limited installation space. The compact, low-profile readhead detects and evaluates the magnetic field of a thin, axially magnetised ring.

✔ True absolute, single track

✔ Non contact, no hysteresis

✔ High speed

✔ Low profile

More details

AksIM-2™ absolute magnetic encoder

✔ True absolute

✔ Improved repeatability

✔ Built-in self-monitoring

✔ Immunity to external magnetic fields

More details

Orbis™ absolute magnetic encoder

A through-hole rotary encoder suitable for applications where a typical encoder cannot be mounted at the end of the rotating shaft due to space constraints. The through-hole measuring principle allows customisation, with various board and magnet sizes to suit your application.

✔ True absolute encoder

✔ Fixable mounting along the shaft

✔ Optional self-calibration

✔ Wide installation tolerances

More details

RESOLUTE™ true-absolute encoder

The true-absolute encoder with a high-speed fine-resolution position measurement system. Position is acquired immediately on start-up without requiring any motion, offering smooth velocity control and dependable positional stability. Available with linear and rotary scales with a variety of serial interfaces.

✔ High speed

✔ Excellent dirt immunity

✔ Low SDE

✔ Low jitter

More details

AM8192B rotary magnetic encoder IC

Designed for motion.

✔ W

✔ D

✔ H

✔ R

More details

OnAxis™ encoder modules

Designed for motion.

✔ W

✔ D

✔ H

✔ R

More details

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