Energy Management of Parallel Hydraulic Hybrid Wheel Loader

Abstract: Hybridization of driveline system is one possible solution to increase fuel eciency.In this thesis a parallel hybrid hydraulic wheel loader concept was studied. A highpressure accumulator was added to the system and acted as a second source of energy.By adding the high pressure accumulator, regenerative braking energy canbe stored for later utilization. A backward facing simulation model was developedwhere the high pressure accumulator's State Of Charge (SOC) as state variableand hydraulic pump/motor's displacement as control input. Furthermore, dierentenergy management strategies: Dynamic Programming (DP), rule-based andEquivalent Consumption Minimization Strategy (ECMS) were developed. Thesestrategies were evaluated and compared to each other all with respect to the fuelconsumption. The result from conventional machine acted as the benchmark forother strategies to compare with. From simulation results, rule-based strategiesshowed to be the most robust, resulted in lower fuel consumption in every testeddriving cycle. For ECMS, the performance varied from cycle to cycle. A reductionin fuel consumption was observed for short-loading cycles. Especially in one cycle,ECMS result outclassed rule-based and was almost the same as DP. However, asmall increment was observed for long-carry cycle. Here the introduction of lock-upfeature in the torque converter yielded instead the most fuel saving. These valuableconclusions acted perfectly as a good starting point for future product development.