| In the mechanical transmission system, the torque is a fundamental parameterreflecting the system performance. Using proper torque measure device, on-line real-timemeasurement and torque controlling is very important to guarantee the whole system stableoperation.Currently electric bicycles are mostly driven by hub motor. Motor placed in front orrear wheels when driven by hub motor which causes the center of gravity of vehicleforward or rearward does not meet people’s riding style, and also driving speed is fullycontrolled by grip, which will make big traffic problems. At the same time, it makesinstallation and maintenance more difficult to use this kind of mechanical hub wheelstructure, invisibly it increases the use costs and failure rates of electric bicycles. Mid-drivesystem use hub motor rather than BLDC and motor is installed in shaft, which meansreleasing driving motor from the front and rear wheels. Mid-drive system combined torquesensor and motor controller, and grip was removed. The output torque was controlled byforce value, cadence and direction. The heavier you pedal, the more assist you will getfrom motor, excellent riding performance will become the development direction ofelectric bicycles.Two key technical points of mid-drive system are introduced in this article: torque andFOC controller[2]. Torque is based on wireless and strain gauge technique. The main chipof FOC is dsPIC30F6010A from Microchip, current sensor is ACS712from Hall and thedrive of MOS is FAN7888from Fairchild.In this article, not only the hardware of torque and FOC, but also the software systemwas designed. The software system includes programs like torque, main loop of FOCcontroller, IaIb current sample, Clark, Parke transform and inverse. |
