Regenerative braking in an electric vehicle

Abstract: Electric vehicles have been attracting unprecedented attention in light of the volatile market prices and prospect of diminishing supplies of fuel. Advances in battery technology and significant improvements in electrical motor efficiency have made electric vehicles an attractive alternative, especially for short distance commuting. This paper describes the application of Brushless DC (BLDC) motor technology in an electric vehicle with special emphasis on regenerative braking. BLDC motors are being encountered more frequently in electric vehicles due to their high efficiency and robustness; however a BLDC motor requires a rather complex control to cope with the reversal of energy flow during the transition from motoring regime to regenerative braking. In an electric vehicle, regenerative breaking helps to conserve energy by charging the battery, thus extending the driving range of the vehicle. There is a number of different ways to implement regenerative braking in a BLDC motor. This paper describes the Independent Switching scheme for regenerative braking [1] as applied to a developmental electric vehicle at the University of South Australia. Electric vehicles and regenerative braking In recent times, electric vehicles (EVs) have received much attention as an alternative to traditional vehicles powered by internal combustion engines running on non-renewable fossil fuels. This unprecedented.focus is mainly attributable to environmental and economic concerns linked to the consumption of fossil-based oil as fuel in internal combustion engine (ICE) powered vehicles. With recent advances in battery technology and motor efficiency, EVs have become a promising solution for commuting over greater distances. Plug-in EVs utilise a battery system which can be recharged from standard power outlets. Since performance characteristics of electric vehicles have become comparable to, if not better than those of traditional Internal Combustion Engine (ICE) vehicles, EVs present a realistic alternative. Regenerative braking can be used in an EV as a way of recouping energy during braking, which is not possible to do in conventional ICE vehicles. Regenerative braking is the process of feeding energy from the drive motor back into the battery during the braking process, when the vehicle's inertia forces the motor into generator mode. In this mode, the battery is seen as a load by the machine, thus providing a braking force on the vehicle. It has been shown that an EV, which uses regenerative braking can have an increased driv ing range of up to 15% compared with an EV, which only uses mechanical braking BLDC motor Principally, a brushless DC (BLDC) motor is an inside-out permanent magnet DC motor, in which the conventional multi-segment commutator, which acts as a mechanical rectifier, is replaced with an electronic circuit to do the com

Fast, Interactive Worst-Case Execution Time Analysis With Back-Annotation

Abstract—For hard real-time systems, static code analysis is needed to derive a safe bound on the worst-case execution time (WCET). Virtually all prior work has focused on the accuracy of WCET analysis without regard to the speed of analysis. The resulting algorithms are often too slow to be integrated into the development cycle, requiring WCET analysis to be postponed until a final verification phase. In this paper we propose interactive WCET analysis as a new method to provide near-instantaneous WCET feedback to the developer during software programming. We show that interactive WCET analysis is feasible using tree-based WCET calculation. The feedback is realized with a plugin for the Java editor jEdit, where the WCET values are back-annotated to the Java source at the statement level. Comparison of this treebased approach with the implicit path enumeration technique (IPET) shows that tree-based analysis scales better with respect to program size and gives similar WCET values. Index Terms—Real time systems, performance analysis, software performance, software reliability, software algorithms, safety I