Even the humble bicycle hasn't escaped the clutches of modern technology. A whole herd of new e-bikes with electric motors are taking to our cities' streets. Adding a motor to a standard cycle does ramp up the price significantly, but it takes much of the effort out of cycling, making your commute to the office a sweat-free experience and allowing you to sit back and enjoy your suburban cruise.
Vehicles exceeding any of the criteria above must be registered and titled as a motorcycle. Other types of vehicles, such as electric scooters, "pocket rockets" and mini-choppers, may fit the definition of a moped or a motorcycle, but cannot be registered by the Department of State if they lack the equipment required by law to legally drive on public roads.
That aside, the Axis is a fantastic e-bike. At 'only' 16kg, it's almost lively by e-bike standards, but it also feels rock solid. It's geared too low in my opinion – I think it's fair to say I am not the target market – but in 8th, you can breeze on past the legally mandated, electrically-assisted 15.5mph. The hydraulic disk brakes will then bring you to a pleasingly rapid dead stop. The range and charging time are good, too. Cheap it is not, mind you.
Controllers for brushless motors: E-bikes require high initial torque and therefore models that use brushless motors typically have Hall sensor commutation for speed and angle measurement. An electronic controller provides assistance as a function of the sensor inputs, the vehicle speed and the required force. The controllers generally allow input by means of potentiometer or Hall Effect twist grip (or thumb-operated lever throttle), closed-loop speed control for precise speed regulation, protection logic for over-voltage, over-current and thermal protection. Bikes with a pedal assist function typically have a disc on the crank shaft featuring a ring of magnets coupled with a Hall sensor giving rise to a series of pulses, the frequency of which is proportional to pedaling speed. The controller uses pulse width modulation to regulate the power to the motor. Sometimes support is provided for regenerative braking but infrequent braking and the low mass of bicycles limits recovered energy. An implementation is described in an application note for a 200 W, 24 V Brushless DC (BLDC) motor.
A new European product safety standard EN 15194 will be published in 2009. EN 15194 contains several new requirements for ebikes to be sold in European Union and European Economic Area, including weight and voltage limitations. EN 15194 also defines a specific name for EU approved electrically-assisted cycles, EPAC - "Electrically Pedal Assisted Cycle".