Systems-theoretic process analysis on assisted boom control

Abstract

This master’s thesis explores a new safety paradigm based on system theory and the application of Systems-Theoretic Process Analysis (STPA) to the assisted boom control system used in various non-road mobile machines. The study begins with an overview of the history of safety engineering, tracing its evolution from early regulations to modern standards. It then briefly introduces traditional safety analysis methods such as Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), and Hazard and Operability Study (HAZOP). The thesis highlights the changes in engineering systems, including the increased complexity and integration of software and automation, and the limitations of traditional safety analysis methods when addressing the complex system interactions and human factors.

The core of the thesis is the detailed application of STPA, a method based on Systems-Theoretic Accident Model and Process (STAMP), which offers a holistic approach to safety by considering system interactions and human errors. The STPA process is illustrated through a case study on assisted boom control, iterating through the steps to define the purpose of the analysis, model the control structure, identify unsafe control actions, and develop the loss scenarios. The results of this analysis led to the identification of multiple design constraints. Based on these constraints, recommendations were made to enhance the safety of the assisted boom control system in an undefined environment. These recommendations included adding new feedback mechanisms and self-diagnostic algorithms.