Energy-Efficient Train Operation Using Control Parameterization Technique (CPT)

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Addis Ababa University


The energy consumed by the traction systems takes the most significant portion of the majority of total energy consumption in Addis Ababa Light Rail Transit (AALRT) system. Finding the energy-efficient train reference profile, also known as an optimal train control problem, is one of the most significant ways of saving energy. However, this optimal control problem belongs to complex computational problems which need robust and efficient solving techniques or algorithms. In this thesis, an efficient numerical strategy known as the control parameterization technique (CPT) is deployed to solve this optimal train control problem. The core idea of this scheme is to approximate the control functions (i.e., the tractive and braking control forces) by piecewise-constant function. In this manner, the optimal train control problem is transformed into a non-linear constrained optimisation problem (NCOP), albeit one with one complex of the state constraints. To overcome this complexity, the constraints are introduced into the cost function via a penalty function in such a way that any violation of the constraints is penalised, transforming a constrained optimisation problem (COP) into an unconstrained optimisation problem (UOP) that can be easily solved with existing unconstrained solvers. Various solutions for every section of the AALRT system/East-West line (i.e., from Ayat to Tor Hailoch station) were generated. The results showed that the speed profile meets the maximum speed limits between two consecutive stations. It has been noticed that the control force successfully satisfies the boundary control constraints between two consecutive station. Moreover, It is worth noting that the train energy consumption from Ayat to Tor Hailoch station has reduced about 9.709% when compared to the one consumed before optimisation.



Energy-efficient train operation, control parameterization technique, constrained optimisation problem, unconstrained optimisation problem