Periodically Controlled Hybrid Systems: Verifying A Controller for An Autonomous Vehicle

This paper introduces Periodically Controlled Hybrid Automata (PCHA) for describing a class of hybrid control systems. In a PCHA, control actions occur roughly periodically while internal and input actions, may occur in the interim changing the discrete-state or the setpoint. Based on periodicity and subtangential conditions, a new sufficient condition for verifying invariance of PCHAs is presented. This technique is used in verifying safety of the planner-controller subsystem of an autonomous ground vehicle, and in deriving geometric properties of planner generated paths that can be followed safely by the controller under environmental uncertainties

Utilizing the infrastructure to assist autonomous vehicles in a mobility on demand context

In this paper we describe an autonomous vehicle that aims at providing shared transportation services in a mobility on demand context. As the service is limited to a known urban environment, prior knowledge of the environment can be exploited, as well as existing infrastructure sensors such as security cameras. We argue that utilizing infrastructure sensors yields greater safety of operation and allows reduction in the number of sensors required on-board, hereby reducing the cost of the vehicle. We describe the role that infrastructure sensors can play and show the resulting improved performances of the system, supported by simulation and field experiment results

Temporal Stream Logic: Synthesis beyond the Bools

Reactive systems that operate in environments with complex data, such as mobile apps or embedded controllers with many sensors, are difficult to synthesize. Synthesis tools usually fail for such systems because the state space resulting from the discretization of the data is too large. We introduce TSL, a new temporal logic that separates control and data. We provide a CEGAR-based synthesis approach for the construction of implementations that are guaranteed to satisfy a TSL specification for all possible instantiations of the data processing functions. TSL provides an attractive trade-off for synthesis. On the one hand, synthesis from TSL, unlike synthesis from standard temporal logics, is undecidable in general. On the other hand, however, synthesis from TSL is scalable, because it is independent of the complexity of the handled data. Among other benchmarks, we have successfully synthesized a music player Android app and a controller for an autonomous vehicle in the Open Race Car Simulator (TORCS.

Autonomous personal vehicle for the first- and last-mile transportation services

This paper describes an autonomous vehicle testbed that aims at providing the first- and last- mile transportation services. The vehicle mainly operates in a crowded urban environment whose features can be extracted a priori. To ensure that the system is economically feasible, we take a minimalistic approach and exploit prior knowledge of the environment and the availability of the existing infrastructure such as cellular networks and traffic cameras. We present three main components of the system: pedestrian detection, localization (even in the presence of tall buildings) and navigation. The performance of each component is evaluated. Finally, we describe the role of the existing infrastructural sensors and show the improved performance of the system when they are utilized

Formal Synthesis of Embedded Control Software: Application to Vehicle Management Systems

Motivated by the transition from federated to integrated architectures in aerial vehicles, we propose an automated methodology for the synthesis of correct-by-construction control protocols for vehicle management systems. We use linear temporal logic as the specification language for precisely describing correct behaviors of the system as well as the admissible dynamic behavior of the environment due to, for example, wind gusts and changes in the flight conditions. We apply the method in the context of dynamic power allocation between a number of subsystems of varying flight-criticality. The resulting power management protocol is guaranteed to be correct, with respect to the overall system specification, for all admissible environment profiles. This approach also enables reasoning about design tradeoffs such as between efficiency (imposed through formal specifications) and system weight (characterized by the amount of required power generation and energy storage). We present our preliminary results in a simple setting and discuss extensions of the methodology to capture more realistic system and environment models and specifications. I

Verification of Periodically Controlled Hybrid Systems: Application to an Autonomous Vehicle

This article introduces Periodically Controlled Hybrid Automata (PCHA) for modular specification of embedded control systems. In a PCHA, control actions that change the control input to the plant occur roughly periodically, while other actions that update the state of the controller may occur in the interim. Such actions could model, for example, sensor updates and information received from higher-level planning modules that change the set point of the controller. Based on periodicity and subtangential conditions, a new sufficient condition for verifying invariant properties of PCHAs is presented. For PCHAs with polynomial continuous vector fields, it is possible to check these conditions automatically using, for example, quantifier elimination or sum of squares decomposition. We examine the feasibility of this automatic approach on a small example. The proposed technique is also used to manually verify safety and progress properties of a fairly complex planner-controller subsystem of an autonomous ground vehicle. Geometric properties of planner-generated paths are derived which guarantee that such paths can be safely followed by the controller

Introspective Environment Modeling

Autonomous systems often operate in complex environments which can beextremely difficult to model manually at design time. The set of agents and objects in the environment can be hard to predict, let alone their behavior. We present the idea of introspective environment modeling, in which one algorithmically synthesizes, by introspecting on the system, assumptions on the environment under which the system can guarantee correct operation and which can be efficiently monitored at run time. We formalize the problem, illustrate it with examples, and describe an approach to solving a simplified version of the problem in the context of temporal logic planning. We conclude with an outlook to future work