CRUISE: fault tolerant Control for highly Redundant multirotor Unmanned aerIal vehicle using Sliding modEs
Lead Research Organisation:
University of Exeter
Department Name: Engineering
Abstract
Recent reports by the EU and House of Lords on the civilian use of unmanned aerial vehicles (UAVs) have highlighted examples of UAV applications for civil and commercial applications, which include search & rescue, inspection and filming. In fact recent media coverage highlighted prominent companies such as Amazon, DHL and Google which are seriously considering, and testing, small UAVs for delivery services.
Despite the huge potential impact of small UAVs on civil life and commercial practices, an increase in reported UAV-related incidents (e.g. a collision with a bridge, near collisions with large passenger aircraft, and injury to an athlete) has been a major concern for regulators worldwide. At present, the commercial use of small UAVs is currently heavily restricted and regulated in the UK. Some incidents occurred due to operator shortcomings, but raise serious concerns about the safety of UAVs, especially when one considers the presence of a large number of civil and commercial UAVs flying autonomously in heavily populated areas. Therefore, there is an urgent need to develop control technologies which will compensate for faults and failures, and enable the safe operation of autonomous UAVs. In fact, it is envisaged that small UAVs will embrace and implement advanced state-of-the-art fault tolerant control schemes before their manned aircraft counterparts could, partly due to their versatility and the fundamental need to ensure safety for civil and commercial applications.
This project will therefore: (1) help improve safety, resilience and survivability of small multirotor unmanned aerial vehicles in the event of in-flight faults and failures, and (2) bridge the gap between the theory and application of sliding mode control, thus encouraging adoption of sliding mode control in industry, particularly aerospace. Flight control systems will be developed for a small, highly redundant UAV for commercial and civil applications. A resilient control system, typically known as fault tolerant control (FTC), will be built based on sliding mode control (SMC) schemes. The fault tolerant schemes will initially be simulated with realistic faults/failures using a simulation tool developed in this project, then followed by hardware implementation and rigorous evaluation on a highly redundant UAV.
An important aspect of this proposal is the partnership with Bristol Robotics Laboratory (BRL) and Blue Bear Systems Research Ltd (BBSR). Driven by industrial challenges and supported by BRL and BBSR, a rigorous assessment and evaluation campaign will be undertaken to highlight the maturation of the control schemes developed during the project. By demonstrating an increase in technology readiness level (TRL), the project will promote the adoption of these technologies in industry.
Despite the huge potential impact of small UAVs on civil life and commercial practices, an increase in reported UAV-related incidents (e.g. a collision with a bridge, near collisions with large passenger aircraft, and injury to an athlete) has been a major concern for regulators worldwide. At present, the commercial use of small UAVs is currently heavily restricted and regulated in the UK. Some incidents occurred due to operator shortcomings, but raise serious concerns about the safety of UAVs, especially when one considers the presence of a large number of civil and commercial UAVs flying autonomously in heavily populated areas. Therefore, there is an urgent need to develop control technologies which will compensate for faults and failures, and enable the safe operation of autonomous UAVs. In fact, it is envisaged that small UAVs will embrace and implement advanced state-of-the-art fault tolerant control schemes before their manned aircraft counterparts could, partly due to their versatility and the fundamental need to ensure safety for civil and commercial applications.
This project will therefore: (1) help improve safety, resilience and survivability of small multirotor unmanned aerial vehicles in the event of in-flight faults and failures, and (2) bridge the gap between the theory and application of sliding mode control, thus encouraging adoption of sliding mode control in industry, particularly aerospace. Flight control systems will be developed for a small, highly redundant UAV for commercial and civil applications. A resilient control system, typically known as fault tolerant control (FTC), will be built based on sliding mode control (SMC) schemes. The fault tolerant schemes will initially be simulated with realistic faults/failures using a simulation tool developed in this project, then followed by hardware implementation and rigorous evaluation on a highly redundant UAV.
An important aspect of this proposal is the partnership with Bristol Robotics Laboratory (BRL) and Blue Bear Systems Research Ltd (BBSR). Driven by industrial challenges and supported by BRL and BBSR, a rigorous assessment and evaluation campaign will be undertaken to highlight the maturation of the control schemes developed during the project. By demonstrating an increase in technology readiness level (TRL), the project will promote the adoption of these technologies in industry.
Planned Impact
Economic impact:
Recent reports from Innovate UK acknowledged that the UK is 'well placed in the soaring UAV market' to unlock the extensive use of UAVs for commercial and civil applications. In formal reports on the civilian use of UAVs, the House of Lords and the European Union have estimated potential growth in the commercial UAVs market of $8.3bn by 2018, with the creation of 150,000 jobs across Europe. The reports also highlight the use of UAVs in civil and commercial applications is envisaged to become an intrinsic part of public life by 2020. Some industries, e.g. filming and leisure, have already embraced the technology, but concerns over safety remain.
This project will tackle challenges, which currently restrict full utilisation of UAVs for civil and commercial applications. Research into fault tolerant control for UAVs is rapidly expanding due to its potential to transform businesses, protect the environment and safeguard our wellbeing. By addressing current safety and technological issues associated with UAVs, this project will facilitate the civil and commercial employment of small UAVs in the UK and Europe, enabling growth of the small UAVs market, thereby solidifying the UK's position as a global leader in this rapidly expanding industry.
Industrial impact:
The technology developed during the project will be valuable to the aerospace sector by addressing UAV safety issues, which are critical for realising the potential of civil and commercial UAV applications in populated areas. Close collaboration with Blue Bear System Research Ltd (BBSR) will allow the company to rapidly access the technological advances developed through this project, thus giving them a strategic lead in the market. Furthermore, the activities in this project will highlight the maturation of the control scheme considered and promote its adoption in industry (e.g. Airbus, Deimos, Qinetiq and QuestUAV), by demonstrating an increase in technology readiness level (TRL). Additionally, the control schemes developed in this project will ultimately benefit areas beyond the UAV application considered in this project, for example: automotive, healthcare and renewable energies (e.g. wind and marine).
Societal impact:
Small UAVs are popular among younger generations, film-makers and tech enthusiasts. Therefore, this project promotes public awareness of the safety hazards associated with UAVs, particularly among commercial and 'emerging leisure users'. This project will also help enable the safe use and applications of civil and commercial UAVs (e.g. search and rescue service) and foster public confidence in the adoption of UAV technology, i.e. safety, security, privacy and data protection. Furthermore, the research in this project has the potential to attract the attention of regulators, and thereby influence UAV safety legislation across the globe.
The project will also inspire younger generations about UAVs, and other engineering topics, e.g. aerospace and coding/programming. Students across the South West of England will be the immediate beneficiaries through outreach, public engagement, open days and summer schools. A wider outreach initiative to inspire the researchers of the future will also be possible through a dedicated webpage created for the project and the University's media service. The webpage will feature the latest news and exciting developments in the field of small UAVs in general such as 'drone racing' and nature-inspired UAV designs (e.g. bats, moths and birds).
Recent reports from Innovate UK acknowledged that the UK is 'well placed in the soaring UAV market' to unlock the extensive use of UAVs for commercial and civil applications. In formal reports on the civilian use of UAVs, the House of Lords and the European Union have estimated potential growth in the commercial UAVs market of $8.3bn by 2018, with the creation of 150,000 jobs across Europe. The reports also highlight the use of UAVs in civil and commercial applications is envisaged to become an intrinsic part of public life by 2020. Some industries, e.g. filming and leisure, have already embraced the technology, but concerns over safety remain.
This project will tackle challenges, which currently restrict full utilisation of UAVs for civil and commercial applications. Research into fault tolerant control for UAVs is rapidly expanding due to its potential to transform businesses, protect the environment and safeguard our wellbeing. By addressing current safety and technological issues associated with UAVs, this project will facilitate the civil and commercial employment of small UAVs in the UK and Europe, enabling growth of the small UAVs market, thereby solidifying the UK's position as a global leader in this rapidly expanding industry.
Industrial impact:
The technology developed during the project will be valuable to the aerospace sector by addressing UAV safety issues, which are critical for realising the potential of civil and commercial UAV applications in populated areas. Close collaboration with Blue Bear System Research Ltd (BBSR) will allow the company to rapidly access the technological advances developed through this project, thus giving them a strategic lead in the market. Furthermore, the activities in this project will highlight the maturation of the control scheme considered and promote its adoption in industry (e.g. Airbus, Deimos, Qinetiq and QuestUAV), by demonstrating an increase in technology readiness level (TRL). Additionally, the control schemes developed in this project will ultimately benefit areas beyond the UAV application considered in this project, for example: automotive, healthcare and renewable energies (e.g. wind and marine).
Societal impact:
Small UAVs are popular among younger generations, film-makers and tech enthusiasts. Therefore, this project promotes public awareness of the safety hazards associated with UAVs, particularly among commercial and 'emerging leisure users'. This project will also help enable the safe use and applications of civil and commercial UAVs (e.g. search and rescue service) and foster public confidence in the adoption of UAV technology, i.e. safety, security, privacy and data protection. Furthermore, the research in this project has the potential to attract the attention of regulators, and thereby influence UAV safety legislation across the globe.
The project will also inspire younger generations about UAVs, and other engineering topics, e.g. aerospace and coding/programming. Students across the South West of England will be the immediate beneficiaries through outreach, public engagement, open days and summer schools. A wider outreach initiative to inspire the researchers of the future will also be possible through a dedicated webpage created for the project and the University's media service. The webpage will feature the latest news and exciting developments in the field of small UAVs in general such as 'drone racing' and nature-inspired UAV designs (e.g. bats, moths and birds).
People |
ORCID iD |
| Halim Alwi (Principal Investigator) |
Publications
Edwards C
(2018)
Flight Evaluations of Sliding Mode Fault Tolerant Controllers
Khattab A
(2019)
Fault Tolerant Control of a Spherical UAV
Mizrak I
(2021)
Fault Tolerant Control of an Octoplane UAV Using Sliding Modes
Waitman S
(2021)
Flight evaluation of simultaneous actuator/sensor fault reconstruction on a quadrotor minidrone
in IET Control Theory & Applications
2021 European Control Conference (ECC)
(2021)
Fault Tolerant Control of a Quadplane UAV Using Sliding Modes
Mizrak I
(2022)
Sliding Mode FTC of an Octoplane UAV transition mode
| Description | Generally, the overall original aims and objectives of the project have been met. The aims of the original proposal are twofold. The first is to help improve safety, resilience and survivability of small multirotor unmanned aerial vehicles (UAVs) in the event of in-flight faults/failures. The second aim is to bridge the gap between the theory and application of sliding mode control through hardware implementation work. To achieve these aims, the original project objectives are: A) Addressing the lack of a virtual testing platform (i.e. a benchmark model and software tool), which is suitable for testing and evaluating fault tolerant control schemes (or any control scheme in general). B) Tackling the issues of safety, resilience and survivability of multirotor UAVs by investigating and developing new fault tolerant controllers, which exploit the robustness of sliding modes. C) Constructing a prototype of the highly redundant multirotor UAV and subsequent implementation, testing and evaluation of existing and new fault tolerant control schemes. Objective A has been met and the outcome is a legacy simulation software of a multirotor UAV which can be used beyond the project. The software has been used to develop various flight control schemes that are resilient to sensor and actuator faults and failures. The software currently mimics a multirotor with 8 propellers which allow new and advanced resilient flight control to be developed and exploit the available redundancy. Although the software can easily be modified to mimic a four, six twelve or sixteen propellers UAVs. The skills developed in the development of these simulations have also be extended to develop other UAV such as the spherical UAVs (developed in this project) and fixed-wing high altitude pseudo satellite UAVs (developed outside this project). Using the software and tools developed through objective A, various resilient flight control have been developed in the virtual testing platform in preparation for the flight tests using prototype hardware developed for objective C. A fixed testing rig was developed for static test of the UAVs (rather than free flight) due to safety reason, but still allow the UAV to rotate freely to mimic the actual flight behaviour. To date, a resilient flight control has been fully tested on the static test rig and results have been published and presented in an international fault tolerant control conference. Other implementation work is still being planned using the prototype UAV and the test rig, beyond the life of the project. Another outcome of the project includes the development of spherical UAV model and simulation software which is unique for fault tolerant control. This is different in comparison to the typical multirotor UAVs considered in the literature. The advantage includes the ability to roll on floors/walls due to the protective outer frame thus allowing this UAVs to be utilised in confined space such as tunnels or cave without damaging the propellers. Another key outcome of the project (as part of objective B) is the development of resilient flight control in the event when no redundancy is available. Typical resilient flight control developed rely on the availability of redundant actuator to maintain control when faults/failures occurred. The work developed in this project can handle the situation when no redundancy is available but still maintain required control and allow for a safe landing. |
| Exploitation Route | One of the main outcomes of the project is the development of spherical UAV which is unique for fault tolerant control. This UAV configuration is different as compared to the typical multirotor UAVs used by many researchers in the area and have many advantages over the typical multirotor. This should provide an alternative for other researchers or UAV developers to exploit. The development of the resilient flight control that can handle the lack of redundant actuator is also currently an open topic and expected to be considered by other researchers interested in the area. |
| Sectors | Aerospace, Defence and Marine |
| Description | The technology developed in this paper is the first to exploit redundancy in an octocopter to achieve a fault-tolerant drone using a novel Sliding Mode scheme. It improves the resilience of drones to faults/failures that develop during flight, therefore, ensuring safety to the public and property, especially for commercial and civil applications. The work is also the first to exploit a special structure of the nonlinear equation of motion of the multicopter drone for control design. The results of the work were presented as one of the keynote presentations at the 2nd World Drone Congress, Shenzhen, China, 2018. The work done in the project also gain widespread interest within academia, with international researchers (e.g., from The Netherlands and France) have explored into the main theoretical ideas due to the robustness properties of the proposed controllers. The work also evolved into a few new PhD research projects in Exeter that focus on tilt-wing and octoplane drones, with taxi drone applications. The work also has generated interest within the industry, due to the importance of safety for aerospace applications, especially with the recent development of the taxi drone. This leads to two collaborative works with Industry: first, an Industrial fellowship supported by the Royal Academy of Engineering, and second, a Knowledge Transfer Partnership supported by Innovate UK; both are hosted by Prismatic Ltd. |
| First Year Of Impact | 2019 |
| Sector | Aerospace, Defence and Marine |
| Description | Flight Control for High Altitude Long Endurance UAV |
| Amount | £29,000 (GBP) |
| Organisation | Royal Academy of Engineering |
| Sector | Charity/Non Profit |
| Country | United Kingdom |
| Start | 09/2018 |
| End | 09/2019 |
| Description | Prismatic:UoExe 2019 |
| Amount | £166,580 (GBP) |
| Funding ID | KTP 12068 |
| Organisation | Innovate UK |
| Sector | Public |
| Country | United Kingdom |
| Start | 01/2020 |
| End | 01/2022 |
| Description | SERAPIS SSE11 (2020-present): Lot 5: Simulation & Synthetic Environment (REF NSC-820-543) |
| Amount | £145,000 (GBP) |
| Funding ID | NSC-820-543 |
| Organisation | Defence Science & Technology Laboratory (DSTL) |
| Sector | Public |
| Country | United Kingdom |
| Start | 10/2020 |
| End | 07/2021 |
| Description | Bristol University - Bristol Robotics Laboratory |
| Organisation | University of Bristol |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | The collaboration with University of Bristol (UoB) and Bristol Robotics Laboratory (BRL) will enable exchange of expertise in the field of aerospace and control systems, and provide our academic research partners with direct access to the expertise and tools available within Control Systems group in Exeter. |
| Collaborator Contribution | The contribution by UoB/BRL are to provide the following facilities and support: • Access to our indoor flight arena and systems here at the BRL for the purposes of flight tests. During the course of the project this would equate to four weeks. • Support from UoB/BRL research staff, for a period of five days over the course of the project. • Access to and use of BRL owned UAV equipment during the period of the Bristol Robotics Laboratory flight trials. • Attending regular progress meetings with Dr Alwi to provide input and to discuss on-going work. |
| Impact | No outcome yet |
| Start Year | 2017 |