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Design of Advanced Antenna and Multi-Sensor Hybrid Receiver for Machine Control in Harsh Environment

Final Report Summary - ADVANSYS (Design of Advanced Antenna and Multi-Sensor Hybrid Receiver for Machine Control in Harsh Environment)

Executive Summary:
This report relates the ADVANSYS project trajectory and main achievements. During the first quarter, the focus of the project has been refined, based on a thorough market analysis conducted by SAT and SSN (D111) and a state-of-the-art survey conducted by DLR (D121). This resulted in basic customer requirements (D112) that were baselined during the first progress meeting and which were used as starting point to specify, during the second quarter of the project, the overall demonstrator concept (D122) and its building blocks: beamforming antenna (D131) and hybrid GNSS/INS receiver (D132).

The third, fourth and fifth quarters were dedicated to design activities:

- The antenna element and front-end have been designed, documented in D211 and manufactured. Two iterations were needed to stabilize the front-end while the antenna element has been iterated 3 times.

- The receiver board has been designed, documented in D221 / D222 and manufactured. Most of the functionality was first-time right, at the exception of the baseband fabric that needed a short iteration to enable to full capacity of the channel matrix

- Besides, algorithmic approaches for beamforming and GNSS/INS integration have been refined and documented in D311 while the concept of using vision-aiding for more cost-effective GNSS/INS solution has been researched (D321), including a concrete test campaign conducted by UNOTT and SSN in Leuven.

Those results were reviewed at MTR, after what, focus was set on implementation and test:

- A first version of the antenna array was designed (D213), assembled (D214), measured at SATIMO (D215) and characterized together with the hybrid receiver in operational static conditions at SSN (D411, D412), respectively during the sixth, seventh and eighth quarters. The ninth quarter was focused on kinematic testing (D421, D422), showing promising results notably in DGNSS under dense canopy.
- The GNSS/INS approach developed during the first part of the project has been implemented on SSN AsteRx3 board and deployed in a GNSS/INS product in collaboration with an INS partner. Although also usable in Machine Control applications, the eventual product was primarily targeted to Mobile Mapping applications, which have also to cope with very harsh operational conditions.

- In parallel again, beamforming algorithm research has been further advanced leading to D311 v2.0 and the redundant IMU and vision researched pursued, leading to D321, D322, D323 and D324

This document relates the main public result achieved during the course of the project.

Project Context and Objectives:
1.1. Context
Machine Control is one of the fastest growing professional GNSS market segments both in terms of addressable market and in revenue. SSN, the coordinator of this proposal, has a multi-year track-record in delivering GNSS hardware and software solutions notably for machine control in various fields of application such as Precision Agriculture, Land and Offshore Construction or Dredging. Several cutting-edge technologies have been pioneered in this segment such as attitude determination through multi-antenna processing or moving-base Real Time Kinematic (RTK) for cm-accurate relative positioning between vehicles. These innovations contributed in a great extend to the growth of the company and its leadership at European scale.

With the increasing acceptance of GNSS technologies in professional applications, competition – especially with US companies – is increasing dramatically and disruptive innovation is mandatory to consolidate leadership at European scale and ambition capturing a significant part of the global market growth.

The ADVANSYS project aimed at supplying the seeds for such disruption, addressing one of the key limitations of GNSS solutions in Machine Contol applications: their ineffectiveness in non-benign environment.

1.2. Objective
In Machine Control applications, GNSS is a preferred technology thanks to its global availability and easiness to deploy and operate (“Plug and Play” character). Common requirements in all high precision Machine Control applications are:

• Sub-meter down to centimeter positioning or guiding accuracy (RMS).
• Attitude (at least heading) determination with accuracy <1 (RMS).
• High Availability and Continuity (24/7 operation, 90%+ availability)
• High Reliability (wrong fix yields major cost)
• High Robustness (resilience to dust, obstruction, high vibration, low motion)

Those requirements are met by high bandwidth, multi-constellation, multi-frequency GNSS receivers enabled with carrier phase-based positioning technologies such as differential Real-Time Kinematic (RTK) or real-time Precise Point Positioning (PPP). Such systems were considered as the baseline of the project

Although very successful, such GNSS-only technologies suffer however from fundamental limitations that make them not-fited in non-benign environment:

• Carrier phase-based techniques such as RTK require high quality phase measurements to properly fix and maintain estimation of the phase ambiguities in order to provide a non-biased positioning solution.
• at least 6 satellites should be in view with good Dilution of Precision (DOP) in order to guaranty cm-level accuracy

Overcoming these limitations is mandatory to extend the field of application outside benign environments and, hence, extend the addressable market. Important opportunities for disruption are identified in enabling applications such as:

• Forestry which yield the need of operating under foliage.
• Mining which yield the need of operating in canyon, with continuously bad DOP.
• Warehouse (Extreme case) where dead-reckoning or backup navigation is required.

Addressing those environments requires the following improvements:

• High sensitivity GNSS (low acquisition and tracking threshold) to maximize the number of satellites that can be exploited in the positioning solution.
• Effective multi-path mitigation to maximize phase measurement quality
• Multi-sensor aiding to overcome possible GNSS outage

Multi-antenna beamforming and GNSS/INS hybridization are two complementary technologies to achieve high sensitivity GNSS. In forestry for instance, state-of-the-art receivers tend to lose lock and suffer from heavy multipath when working under dense foliage. Even if the actual signal masking by the tree only lasts, say, one second, it typically takes 5 seconds or more to recover full lock onto the carrier phase of the signal. This means that the availability of RTK in forestry applications is seriously degraded.

Beamforming offers a potential solution to that problem: having beams directed to the satellites improve the signal-to-noise ratio, and will allow the receiver to maintain track even under dense foliage. This will remove long relocks periods, significantly improving the availability.

But, beamforming alone is not sufficient. For precise positioning, the receiver must accurately measure the propagation delay of the satellite signal. When the satellite signal passes through the branches and trunk of the trees, it is retarded, causing a bias in the delay measured by the receiver. So, while beamforming will allow tracking the signal under trees, the resulting delay measurements will be corrupted, and not usable for high accuracy positioning. The solution to that problem is to combine INS and GNSS. During the (usually short) periods where the GNSS signal is biased by the propagation through materials, the INS can still produce valid update of the receiver position while phase prediction can be exploited to reduce the phase measurement noise and distortion.

The purpose of the ADVANSYS project was to provide a disruptive, high value-added, multi-technology positioning/guidance solution addressing the identified limitation of current professional GNSS offering for Machine Control in non-benign environment.

Therefore, the following technologies were developed and implemented into a prototype:

• solutions for high sensitivity and high resilience GNSS including an integrated multi-element antenna array and a multi-antenna multi-constellation GNSS receiver with built-in beamforming digital signal processing capabilities
• multi-sensor GNSS-aiding solution including
• Tighter coupling between the GNSS engine and a multi-sensor navigation system based on a cost effective INS solution
• In order to achieve cost effective INS, enabling the use of lower grade IMU through
• the exploitation of a redundancy of IMU
• the hybridization with at least one complementary technology: vision-based motion determination

1.3. Team

The meet this challenging objective, the talent, previous experience and background of a well balanced team were exploited. The team was made of:

SEPTENTRIO SATELLITE NAVIGATION, N.V. was founded in January 2000, as a privately held company for the development and production of high-end dual frequency GNSS receivers. Headquarters are in Leuven's DSP Valley, close to Brussels, Belgium. Septentrio is an Original Equipment Manufacturer (OEM), providing both the hardware and the software for high-end satellite navigation equipment for precise positioning, time and time-transfer applications, and attitude determination applications. We actively support customers with customization, prototypes, field tests and application integration.
DEUTSCHES ZENTRUM FÜR LUFT- UND RAUMFAHRT (DLR) is Germany's national research center for aeronautics and space. Its extensive research and development work is integrated into national and international cooperative ventures. As Germany's Space Agency, DLR has been given responsibility for the forward planning and the implementation of the German space program by the German federal government as well as for the international representation of German interests. Approximately 5,100 people are employed in DLR's 31 institutes and facilities at 8 locations in Germany.
SATIMO Industries, S.A.S .is a private company founded in 1986. The core activity of SATIMO concerns the development, the industrialization and the commercialization of antenna measurement systems based on multi-sensor technology. Recently, SATIMO has introduced its real-time multi-sensor technology in industrial sectors like quality control and 3D imagery. Since 2000, SATIMO is involved in the design, industrialization and commercialization of specific high performance antennas dedicated to measurement systems, military applications, GNSS reference fixed stations and GNSS professional applications. Headquarters are in Villebon-sur-Yvette, close to Paris, France. The antenna team is composed by 17 persons and is present in Villebon, Brest and Rome. Additional offices in Atlanta, Hong-Kong, Goteborg and Tokyo ensure to SATIMO a global coverage and a strong reactivity with its customers in terms of commercial contact, installations, upgrades, after sales services and maintenance.
UNIVERSITY OF NOTTINGHAM excels in world-changing research. Ranked by Newsweek in the world's Top 75 universities, its academics have won two Nobel Prizes since 2003. UNOTT and the East Midlands Development Agency (emda) have recently signed a formal agreement which will see a £9m state-of-the-art GNSS/Galileo Research and Application Centre of Excellence (GRACE) built in Nottingham, capitalizing on existing world-leading research and training at the IESSG to support industry, including SMEs and entrepreneurs. The IESSG is part of the Department of Civil Engineering, one of the leading of its type in the UK, with a large multidisciplinary research portfolio, with a particular emphasis on knowledge transfer. The IESSG has a longstanding research record on GNSS and on Galileo, and currently employs 8 full-time and 1 part-time academic staff, 10 post-doctoral researchers and 3 senior experimental officers.

Project Results:
see pdf
Potential Impact:
see pdf
List of Websites:
https://fp7advansys.eu
bruno.bougard@septentrio.com