Abstract
As a general trend in industrial robotics, an increasing number of safety functions are being developed or re-engineered to be handled in software rather than by physical hardware such as safety relays or interlock circuits. This trend reinforces the importance of supplementing traditional, input-based testing and quality procedures which are widely used in industry today, with formal verification and model-checking methods. To this end, this paper focuses on a representative safety-critical system in an ABB industrial paint robot, namely the High-Voltage electrostatic Control system (HVC). The practical convergence of the high-voltage produced by the HVC, essential for safe operation, is formally verified using a novel and general co-verification framework where hardware and software models are related via platform mappings. This approach enables the pragmatic combination of highly diverse and specialised tools. The paper's main contribution includes details on how hardware abstraction and verification results can be transferred between tools in order to verify system-level safety properties. It is noteworthy that the HVC application considered in this paper has a rather generic form of a feedback controller. Hence, the co-verification framework and experiences reported here are also highly relevant for any cyber-physical system tracking a setpoint reference.
Highlights
The liberation of industrial robots from traditional metal cages and steadily increasing number of co-bots working side by side with humans are illustrative examples of a general trend in industrial robotics
To set the stage for and address this ongoing industrial trend, this paper advocates use of formal verification techniques, which can provide an extra level of assurance by verifying the logic of a system
Using the co-verification framework as illustrated in Fig. 8, we address the formal verification of system Property P1
Summary
The liberation of industrial robots from traditional metal cages and steadily increasing number of co-bots working side by side with humans are illustrative examples of a general trend in industrial robotics. Modern industrial robots are heavily dependent on software-implemented safety signals to monitor and control various critical subsystems such as current/voltage supervision and emergency stop or short circuit interrupts This trend brings several distinctive advantages such as cost-reduction and increased flexibility. 5. using a novel approach to co-verification to combine the results from hardware simulations in Simulink with the modelchecking capabilities of RoboTool [16] to verify that the high-voltage produced by the HVC follows the setpoint, a system-level safety property. It details the coverification framework and explains how the state machine was modelled in RoboChart and combined with Mathworks SDV simulation and verification results in order to verify the system-level safety property concerning the high-voltage.
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