# Challenges in the Guidance, Navigation and Control of Autonomous and Transport Vehicles
## 1 Introduction  
In recent years, autonomous and transportation vehicles have been evolving towards more electric or hybrid electric systems, with new challenges arising in their guidance, navigation and control (GNC) systems. Some of these challenges are focused on allowing vehicles to operate more autonomously and efficiently but also more safely in challenging or increasingly congested city environments. Some of the challenges also involve anticipated requirements for collaborative GNC to allow new capabilities such as platooning or to benefit from the new mission capabilities that can be made possible through the coordination of different vehicle types. Some answers to these challenges have been developed in recent years, such as simultaneous localisation and mapping (SLAM) approaches [1]. Increasing levels of autonomy are also driving a need for advances in sensor fusion, trajectory optimisation and control, while new actuation and control technologies are giving rise to new control problems. These include torque vectoring [2], for which energy-optimised control allocation approaches have been developed but with little consideration of lateral motion control, for example. Another control challenge is the development of regenerative braking solutions for electric or hybrid vehicles in driving modes such as eco-approach [3] and autonomous lane management. Other challenges are associated with the new environments where some vehicles are increasingly required to evolve. These challenges must be addressed while meeting requirements regarding safety, efficiency and emissions for different types of autonomous or transportation vehicles, ranging from mobile robots to ground vehicles and aircraft. In the field of electric aviation, policies are shaping some of the priorities in the fields of GNC and vehicle autonomy. The Federal Aviation Authority (FAA) was recently (May 2024) authorised by the United States (US) House of Representatives to issue approvals for beyond visual line of sight (BVLOS) electric vertical take-off and landing (eVTOL) and drone operations, which will imply advances in their flight safety and autonomy. In Europe, the European Union has also adopted legislation on drones and eVTOLs, including air taxis, as part of a wider strategy towards reaching net-zero emissions by 2050. In the United Kingdom (UK), routine BVLOS drone operations by 2027 and fully autonomous eVTOL flights by 2030 are part of the UK Future of Flight Action Plan [4]. Many of the proposed innovative drone and eVTOL designs use hybrid aircraft configurations with new fault tolerance, aerodynamics and control challenges, combining the ability to cruise like a plane with VTOL capability. In car manufacturing, similar electrification trends are being observed, and the UK has, for example, mandated that zero-emission vehicles will represent 80% of all car manufacturers's sales by 2030 and 100% by 2035. The majority of road vehicles will also offer autonomy level 2+ (as defined by the Society of Automobile Engineers (SAE) International) or higher from 2030 [5], which will include new features such as lane-keeping assistance, safe distance maintenance, and automatic lane change manoeuvres. The proportion of vehicles with level 3 to level 5 autonomy willalso significantly increase compared to current levels. A direct implication is the need for higher-performance integrated sensor fusion using radar, Lidar and visual navigation technologies and higher-level computation performance, which also implies efficient GNC algorithm implementation. These trends are global; a fast-growing electric vehicle and eVTOL industry is also emerging in China, for example. Advances in vehicle autonomy also require the development of sense-and-avoid technologies and algorithms, the ability to autonomously handle constraints and recover from faults or sensor signal interruption, and an efficient combination of manned and automated control systems.