Optimization and Control of Cyber-Physical Vehicle Systems

Justin Bradley, Ella Atkins
2015 Sensors  
A cyber-physical system (CPS) is composed of tightly-integrated computation, communication and physical elements. Medical devices, buildings, mobile devices, robots, transportation and energy systems can benefit from CPS co-design and optimization techniques. Cyber-physical vehicle systems (CPVSs) are rapidly advancing due to progress in real-time computing, control and artificial intelligence. Multidisciplinary or multi-objective design optimization maximizes CPS efficiency, capability and
more » ... ty, while online regulation enables the vehicle to be responsive to disturbances, modeling errors and uncertainties. CPVS optimization occurs at design-time and at run-time. This paper surveys the run-time cooperative optimization or co-optimization of cyber and physical systems, which have historically been considered separately. A run-time CPVS is also cooperatively regulated or co-regulated when cyber and physical resources are utilized in a manner that is responsive to both cyber and physical system requirements. This paper surveys research that considers both cyber and physical resources in co-optimization and co-regulation schemes with applications to mobile robotic and vehicle systems. Time-varying sampling patterns, sensor scheduling, anytime control, feedback scheduling, task and motion planning and resource sharing are examined. A cyber-physical system (CPS) is "the next generation of system that requires tight integration of computing, communication, and control technologies to achieve stability, performance, reliability, robustness, and efficiency in dealing with physical systems of many application domains" [1]. A cyber-physical vehicle system (CPVS), ranging from automobile to aircraft and marine craft, is composed of tightly-coupled locomotion, computational and communication components. Historically, CPVS development has been driven by advances in closely-related (but not identical) autonomous vehicle research [2,3] and cooperative vehicle control to increase system capacity and improve safety and efficiency [4] [5] [6] [7] . CPS research generally aims to synergistically integrate control, computing, communications and physical systems in novel ways that leverage interdependent behavior. CPSs have broad applicability and have been the topic of numerous committee workshops and reports [8-13] focused on identifying and addressing next-generation opportunities and challenges. Consumer devices, such as smartphones, multimedia players and gaming systems, respond to voice commands, and wearable electronics are ubiquitous. Smart buildings are equipped with advanced sensors, pervasive networking and efficient energy management systems [14] . Advances in medical devices can lower costs and improve patient care [15] [16] [17] [18] . New software-enabled functionality, increased connectivity and physiologically closed-loop systems have the potential to reduce human error that can cost lives [15, 19, 20] . A new energy service system dubbed the "smart grid" promises to utilize CPS technologies to increase configurability, adaptability, reactiveness and self-manageability [21], but will simultaneously require CPS breakthroughs in security to monitor, manage and thwart threats both to the physical entities comprising the grid, as well as the cyber attacks on its networked components [22] . Most relevant to the work in this paper is the application of CPS research to vehicle systems. In this domain, CPVS research offers an increase in autonomy, reconfigurability, reliability, system capacity, safety, energy efficiency and robustness [23] . Human beings are the quintessential CPSs possessing heavily interdependent cyber (mind) and physical (body) subsystems. Analogous to this mind-body paradigm, advanced CPVSs utilize both cyber and physical resources. However, unlike the symbiotic mind-body awareness humans have, to date, cyber and physical subsystems are unaware or only partially aware of the other. Typically, the cyber system receives performance feedback and calculates trajectories and control inputs for only the physical system. In this way, the cyber system serves the needs of the physical system. This particular role in CPVS has received a great amount of research attention, most prominently in the form of control theory, path planning and real-time system (RTS) theory. It is also likely that the physical system is accomplishing a mission objective that services the goals of the cyber system, for example surveillance, safe transportation, science data collection, etc. In this way, the physical system serves the needs of the cyber system. This role, however, has historically been dominated by humans in-the-loop who design high-level plans, set waypoints, control or modify tasks either through an interface or direct software manipulation. Comprehensive holistic CPVS co-design would account for cyber and physical resources spanning the life-cycle of a system or system of systems [24] . This would include a priori co-design of the structure, electromechanical and processing components, baseline software, communication protocols Sensors 2015, 15 23022 and subsystem composability and compositionality [25] . Holistic CPS run-time system design optimizes and regulates electromechanical and processing element operation in accordance with mission goals and system actuation, processing and energy constraints [26] . While either the a priori or run-time CPVS design challenges could serve as a worthy survey topic, this paper focuses on run-time CPVS. Continuing the analogy above, humans are not able to choose their bodies (i.e., the physical "hardware"), and yet, still optimize perception, decision and action for their holistic mind-body system considering both physical (body) and cyber (mind) resources. We consider CPS run-time co-design from the perspective of co-optimizing and co-regulating available physical and cyber resources for a single vehicle after the physical hardware has been manufactured. This means that models and algorithms must capture preexisting characteristics and properties of the physical system, as they are not modifiable. Emerging CPVS research extends the traditional independently-designed subsystem architectures for modern vehicles toward methods of interdependent and integrated CPVS co-design. In Figure 1 , we show the often segregated design techniques contrasted with the tight coupling and integration in a co-designed CPVS.
doi:10.3390/s150923020 pmid:26378541 pmcid:PMC4610443 fatcat:os7eflcesbeh3a32g2jdhnj62u