Photo: Parker Lord
Aerial drones might become lost drones as they disappear beyond the visual line of sight. Whether delivering a package, shooting aerial footage for a commercial or tracking the progress on a construction site, the drone’s position must be known with high certainty while operating within the national airspace.

SOLUTION: The GQ7 Inertial Navigation System
Multiple integrated sensors and support for external aiding; including:

  • High-precision, low-noise MEMS accelerometers and gyroscopes
  • Dual integrated, RTK-capable GNSS receivers
    • Multi-band, multi-constellation GNSS
  • Dual receivers provide high accuracy heading, as well as GNSS system redundancy
  • Integrated barometric pressure sensor
  • Integrated magnetometer
  • Integrated hardware support for wheel odometry
  • API support for external sensor measurements

Product Details

Lost or weak GNSS signals are always a concern – be it due to an urban canyon, a tunnel or other obstructions encountered in real-world applications.

To traverse these satellite outages, an inertial navigation system (INS) is needed. An INS integrates accelerometers, gyroscopes and other sensors with one or more global positioning systems (GPS/GNSS) receivers via a Kalman filter to provide an estimation of an object’s position, velocity and attitude. MicroStrain’s compact 3DMGQ7-GNSS/INS is designed to be used in demanding applications, such as aerial drones, unmanned ground vehicles and advanced wheeled and legged robots.

Parker LORD develops and manufactures MicroStrain inertial sensors and navigation systems, wireless sensor data acquisition systems, micro-displacement sensors and software for a wide range of custom and embedded applications.

Tracking unmanned drones and vehicles requires the highest degree of accuracy, especially when encountering lapses in satellite coverage. MicroStrain’s 3DMGQ7-GNSS/INS, with its high-precision MEMS inertial sensors, dual state-of-the art RTK GNSS receivers and advanced adaptive Kalman filter, is optimally engineered for maximum position, velocity and attitude (PVA) accuracy. It is ideally suited for today’s most demanding applications, such as beyond-line-of-sight drones and self-driving vehicles.

Challenge

Global positioning systems (GPS/GNSS) are widely used in navigation applications. Yet, positioning systems based on GNSS alone can face challenges in urban canyon environments, where the street is flanked by buildings on both sides. The tall, dense, high-rise buildings create GNSS satellite signal reception problems, such as multipath and partial or complete constellation occlusion. The position of a drone or unmanned vehicle can be difficult to determine, resulting in it being “lost” and unable to complete its task.

Photo: Tatiana Shepeleva / Adobe Stock

Areas most affected by satellite signal disruptions

The disruption of satellite signals are most acute in full occlusion situations, like tunnels, but also occur in partial occlusion situations, such as high-rise metro areas, construction sites and even the tree-line suburban streets.

Autonomous delivery vehicles and robots (part of the trend toward delivery without human contact), continue to encounter outage areas regularly. The ability to traverse areas of poor GNSS coverage is essential when considering how to ensure accurate and on-time deliveries. The miniature inertial navigation systems that have been deployed on robots over the years can underperform in these applications because of poor MEMS sensor performance and their use of loosely coupled filtering.

During an outage, performance of inertial sensors is pivotal. Small errors build rapidly over time causing the robot to lose track of its position in a matter of seconds. This problem is compounded by the use of loosely coupled filtering, where the device’s Kalman filter corrects its estimate of position using the position solution from the GNSS receiver. In difficult environments, the GNSS receiver is often unable to form a solution due to seeing less than the required four satellites.

Creating a solution

APPLICATIONS

Multiple integrated sensors and support for external aiding; including:

  • Beyond visual line of sight navigation
  • Autonomous vehicle operation
  • Simultaneous localization and mapping
  • Wheeled and legged robotics

Challenging environments and applications require a new approach to achieve precise positioning for unmanned aerial and land vehicles. MicroStrain developed the 3DMGQ7-GNSS/INS to perform accurately in these situations. The Kalman filter is tightly-coupled, processing the raw satellite measurements directly, allowing the position estimation to continue to track even when only a couple of satellites can be observed.

Furthermore, the GQ7 incorporates two GNSS receivers which provide highly accurate heading measurements when using two antennas. Should this heading be unavailable due to total GNSS signal occlusion, it can be augmented by the onboard magnetometer to maintain an accurate estimation of heading.

During total-occlusion events, the low-noise MEMS accelerometers and low drift MEMS gyroscopes ensure maximum GNSS outage performance. These sensors are factory calibrated over temperature to ensure they maintain their stated performance.

Additionally, a built-in pressure altimeter helps maintain an accurate estimate of altitude during outage periods, a key redundancy for aerial vehicles. Wheel speed sensor inputs help maintain an accurate estimate of velocity during outage periods, a key redundancy for ground vehicles.

Photo: Emesent

Drone flying under bridge using Emesent Hovermap Platform. MicroStrain inertial sensors are built into the Hovermap platform, which automates the collection and analysis of data in challenging GPS-denied environments. (Photo: Emesent)

The GQ7 accepts standard RTCM real-time kinematic (RTK) corrections, which result in a phenomenal 2 cm position accuracy, when available. One of the most important system-level features beyond accuracy and redundancy is easy use. The GQ7 is unique in that not only is it a complete inertial navigation system with multiple integrated aiding sensors, it also has support for external aiding via the MIP (MicroStrain Inertial Packet) API. The MIP API, in use for nearly a decade, provides a lightweight, simple user interface.

The API supports several external measurements, with new measurements added as customer needs are addressed. This flexibility, along with the ability to update the device firmware easily, sets the GQ7 apart from competitive products.

The GQ7 also accepts standard RTCM3 corrections. Should the user not have their own RTK correction source, MicroStrain is rolling out the SensorCloud RTK correction network. This add-on service provides worldwide differential corrections, as well as significant RTK correction coverage in developed nations.

What does it do?

The GQ7 provides easy to use, high accuracy position, velocity and attitude estimates at rates up to 1 kHz. The accuracy is at the top of its class, with up to 2-cm positional accuracy, 0.05 m/s velocity accuracy, 0.1-degree roll/pitch accuracy and 0.25 degree heading accuracy with dual-antenna GNSS.Photo: Parker LORD

It uses an adaptive Kalman filter, which provides a better estimate of position, velocity and attitude when measurement anomalies are encountered, such as intermittent periods of significant vibration or the occasional outlier in GNSS, magnetometer, altimeter or other measurement inputs. Additionally, online tracking of IMU error sources provide superior dead-reckoning performance.

Why is this important?

The 3DMGQ7-GNSS/INS delivers accurate positioning for drones, unmanned vehicle navigation, wheeled and legged robots and autonomous vehicles, so critical navigation information won’t lapse when satellite signals are poor. It provides global multiband RTK coverage and calibrated temperature performance, delivering high accuracy results under all environmental conditions while fitting into a small, lightweight package. Combined with the SensorCloud™ RTK network service and cellular enabled RTK Dongle (3DMRTK), the 3DMGQ7-GNSS/INS and 3DMRTK is a complete out-of-the-box, advanced, centimeter level accuracy navigation solution.

Learn more about the 3DMGQ7-GNSS/INS and 3DMRTK and other inertial sensing solutions from MicroStrain.

MicroStrain Unmanned and Autonomous Vehicle Sensors


This page was produced by North Coast Media’s content marketing staff in collaboration with Parker LORD. NCM Content Marketing connects marketers to audiences and delivers industry trends, business tips and product information. The GPS World editorial staff did not create this content.

Header photo: Aliaksandr Marko / Adobe Stock