Computer simulation of an electric bicycle wheel drive with real load emulation

Abstract

Topicality. Micro-mobile electric vehicles, whose drives are based on brushless DC motors, have become widespread in the last decade. The features of the electric drive systems of these vehicles and their on-board power supply systems are the subject of scientific research aimed at solving such key problems as: increasing the driving range, reducing electromagnetic torque ripple, improving the efficiency of regenerative braking, etc. A review of the literature shows that solving each individual problem involves two different approaches: computer simulation and physical experimentation. Purpose and objectives. To combine both approaches of testing: conducting experimental research with real vehicle systems and simulating the effect of road load and real dynamic load on the drive in transient modes using a corresponding load emulator. The latter consists of hardware that generates mechanical load on the drive and software that allows simulating various specified and repeated vehicle motion modes in experiments. Methods. In this work, the Hardware-In-The-Loop approach is applied to an electric bicycle test bench, in which a real wheel with in-wheel motor is connected via a friction transmission to a DC loading machine controlled by a two-quadrant DC-DC converter. Results. In this work, to control the torque of the loading machine, an emulator control system structure was developed, in which the conditions for the movement of the electric bicycle are set and tasks related to these conditions are formed for static and dynamic loads. A computer model of a test bench for studying the electric bicycle drive, developed in the Matlab/Simulink environment, made it possible to identify the features of the hardware part of the in-wheel motor load emulator. In particular, during the emulation of a dynamic load associated with the high moment of inertia of the drive, when the electric bicycle starts and initially accelerates at low speeds, the two-quadrant DC-DC converter is unable to provide the required value of the braking current of the load machine. Therefore, it was necessary to ensure the operation of the DC-DC converter in the third quadrant for the specified mode using an additionally introduced two-transistor switch, which allows switching the operation of the DC-DC converter from the second to the third quadrant and vice versa. A control system has been developed that performs such switching. Conclusions. A comparison of the results of computer simulation of the operation of the electric bicycle in-wheel motor drive on a test bench with load emulation with the corresponding results of simulation of the operation of the same drive in an electric bicycle under the same driving conditions showed a discrepancy in the main motion coordinates of no more than of seven percent, which confirms the adequacy of the emulation and the operability of all solutions adopted for the creation of the test bench.