Federico Mari

Model-based synthesis of control software from system-level formal specifications

Many embedded systems are indeed software-based control systems, that is, control systems whose controller consists of control software running on a microcontroller device. This motivates investigation on formal model-based design approaches for automatic synthesis of embedded systems control software. We present an algorithm, along with a tool QKS implementing it, that from a formal model (as a discrete-time linear hybrid system) of the controlled system (plant), implementation specifications (that is, number of bits in the Analog-to-Digital, AD, conversion) and system-level formal specifications (that is, safety and liveness requirements for the closed loop system) returns correct-by-construction control software that has a Worst-Case Execution Time (WCET) linear in the number of AD bits and meets the given specifications. We show feasibility of our approach by presenting experimental results on using it to synthesize control software for a buck DC-DC converter, a widely used mixed-mode analog circuit, and for the inverted pendulum.

Automatic control software synthesis for quantized discrete time hybrid systems

Many Embedded Systems are indeed Software Based Control Systems, that is control systems whose controller consists of control software running on a microcontroller device. This motivates investigation on Formal Model Based Design approaches for automatic synthesis of embedded systems control software. This paper addresses control software synthesis for discrete time nonlinear hybrid systems. We present a methodology to overapproximate the dynamics of a discrete time nonlinear hybrid system ℌ by means of a discrete time linear hybrid system Lℌ, in such a way that controllers for Lℌ are guaranteed to be controllers for ℌ. We present experimental results on control software synthesis for the inverted pendulum, a challenging and meaningful control problem.

Synthesis of quantized feedback control software for discrete time linear hybrid systems

We present an algorithm that given a Discrete Time Linear Hybrid System

On placing skips optimally in expectation

{\cal H}

System Level Formal Verification via Distributed Multi-core Hardware in the Loop Simulation

returns a correct-by-construction software implementation K for a (near time optimal) robust quantized feedback controller for

Undecidability of quantized state feedback control for discrete time linear hybrid systems

{\cal H}

On model based synthesis of embedded control software

along with the set of states on which K is guaranteed to work correctly (controllable region) Furthermore, K has a Worst Case Execution Time linear in the number of bits of the quantization schema.

Demand-aware price policy synthesis and verification services for Smart Grids

We study the problem of optimal skip placement in an inverted list. Assuming the query distribution to be known in advance, we formally prove that an optimal skip placement can be computed quite efficiently. Our best algorithm runs in time O (n log n), n being the length of the list. The placement is optimal in the sense that it minimizes the expected time to process a query. Our theoretical results are matched by experiments with a real corpus, showing that substantial savings can be obtained with respect to the traditional skip placement strategy, that of placing consecutive skips, each spanning √n many locations.

Anytime System Level Verification via Random Exhaustive Hardware in the Loop Simulation

The goal of System Level Formal Verification (SLFV) is to show system correctness notwithstanding uncontrollable events (such as: faults, variation in system parameters, external inputs, etc). Hardware In the Loop Simulation (HILS) based SLFV attains such a goal by considering exhaustively all relevant simulation scenarios. We present a distributed multi-core algorithm for HILS-based SLFV. Our experimental results on the Fuel Control System example in the Simulink distribution show that by using 64 machines with an 8 core processor each we can complete the SLFV activity in about 27 hours whereas a sequential approach would require more than 200 days. To the best of our knowledge this is the first time that a distributed multi-core algorithm for HILS-based SLFV is presented.

On-the-Fly Control Software Synthesis

We show that the existence of a quantized controller for a given Discrete Time Linear Hybrid System (DTLHS) is undecidable. This is a relevant class of controllers since control software always implements a quantized controller. Furthermore, we investigate the relationship between dense time modelling and discrete time modelling by showing that any Rectangular Hybrid Automaton (and thus, any Timed Automaton) can be modelled as a DTLHS.