# Software Fault Tolerance for Cyber-Physical Systems via Full System Restart

## TL;DR

This paper introduces a novel fault-tolerant control approach for cyber-physical systems that ensures safety and enables safe system restart, even with complex controllers like neural networks, demonstrated on inverted pendulum and helicopter systems.

## Contribution

It presents a formal, abstraction-based controller synthesis method that guarantees safety and fault tolerance, allowing safe restarts during runtime for complex embedded control systems.

## Key findings

- Successfully verified safety under various fault injections
- Implemented on real systems: inverted pendulum and 3-DOF helicopter
- Enables use of unverified controllers like neural networks

## Abstract

The paper addresses the issue of reliability of complex embedded control systems in the safety-critical environment. In this paper, we propose a novel approach to design controller that (i) guarantees the safety of nonlinear physical systems, (ii) enables safe system restart during runtime, and (iii) allows the use of complex, unverified controllers (e.g., neural networks) that drive the physical systems towards complex specifications. We use abstraction-based controller synthesis approach to design a formally verified controller that provides application and system-level fault tolerance along with safety guarantee. Moreover, our approach is implementable using commercial-off-the-shelf (COTS) processing unit. To demonstrate the efficacy of our solution and to verify the safety of the system under various types of faults injected in applications and in the underlying real-time operating system (RTOS), we implemented the proposed controller for the inverted pendulum and three degree-of-freedom (3-DOF) helicopter.