E-Bike, also known as electric assisted bicycle, is a bicycle with auxiliary power of electric drive but still mainly driven by human pedaling.

In recent years, electric power products have blossomed, and many manufacturers have also rushed to participate in technology research and development. More and more good products have sprung up, gradually entering the daily lives of riders. However, electric power assistance is still a new thing, various proprietary vocabulary related to E-Bike, in this article we are here to make a simple science popularization for everyone.

1. Mid-mounted motor/wheel hub motor

According to the position of the motor on the e-bike, electric assisted bicycles are generally divided into two types: mid-mounted motor and hub motor. At present, the electric power solutions of mainstream high-end brands are mainly center-mounted motors, which belong to the most cutting-edge level in the industry. The mid-mounted motor is located in the bottom bracket part of the frame, with a gear box structure, which replaces the position of the bottom axle; while the hub motor is integrated with the hub of the bicycle at the hub of the front and rear wheels.

2. Sensor

In addition to the electric motor, the core technology of the electric bicycle is also a part that needs to be refined. Different manufacturers have their own patented technology to optimize the algorithms for different sensing parts. Generally speaking, the more important sensors are the cadence/torque sensors inside or around the motor. These sensors can sense movement and transmit different signals to the controller for calculations to achieve changes in output and achieve the purpose of acceleration and deceleration.

In fact, advanced E-BIKE will generally use more advanced torque sensors, that is, sensing the changes of the rider's force acting on the pedals, cranks, and bottom brackets, and its feedback to the actual riding situation is more realistic.

Finally, there is a speed sensor, which is generally located inside the front and rear forks, connected to the motor through a cable, and senses the rotation of the wheels, and measures real-time speed, mileage and other data for the control dashboard. The principle is similar to the wired code table, electromagnetic/infrared induction is available, and it is one of the standard sensors of electric-assisted models.

3. Current, power

Current: How fast the e-bike can run depends on the output of the motor, which is generally achieved by controlling the output current of the battery. The size of the current is controllable, precisely controlled by the controller algorithm, with high accuracy, and a constant current output, so that the output power of the motor can be adjusted steplessly.

Power: Generally, what we call the motor power refers to the rated output power of the motor, that is, the maximum output power that can operate normally for a long time under ideal conditions. Some people call it the "maximum use power". Note that the rated power of the motor is not equal to the peak power. The greater the power, the stronger the motor output, and the more it can measure whether an E-BIKE is capable of heavy work. Generally, the motor power of mountain-assisted models will be higher, while the urban and portable models are more compact and balanced.

4. Torque and speed reduction device

Torque is a special moment that causes an object to rotate. The torque in the E-BIKE parameter refers to the torque output by the motor from the crank end, which reflects the load capacity of the car within a certain range. Torque is similar to the pedaling force exerted on the crank. The larger it represents the stronger the motor output, which is more suitable for difficult riding situations, such as mountain biking off-road and undulating terrain.

After the motor directly rotates and outputs, it needs to pass a series of mechanical speed reduction devices to amplify its original torque, reduce the speed, and indirectly apply kinetic energy to the crank and chainring. In this way, the motor output can be softer, and the auxiliary power feels more simulating human stepping, and it also protects the motor, reduces the load pressure, and delays the life of its internal mechanism. This is especially important for the violent output E-BIKE.

5. Battery, capacity

At present, most electric bicycles on the market use 18650 lithium battery cells, which have long life, large unit density and capacity, stable working performance, and standard specifications. "18650" means the battery cell specification model (diameter 18mm, length 65mm).

In addition, many people are used to expressing battery capacity in milliamperes, but strictly speaking, this is a wrong way of expression. Milliampere is the unit of measurement of current, milliampere hour (mAh) is the correct battery capacity unit, and some rigorous brands will also mark watt hours (wh) at the same time.

6. Clutch and clutch ratchet

The clutch is a special mechanical structure unique to the central motor. When the motor is not energized, the motor is separated from the bottom axle gear, and there is no resistance. At this time, it is the same as the ordinary bicycle pedaling method. The key mechanism at play is called the "overrunning clutch".

The overrunning clutch emerged with the development of mechatronics products, and is an important part of the power transmission and separation function between the driving shaft and the driven shaft inside the machine. It is a device that uses the speed change or rotation direction change of the main and driven parts to make the power self-clutch under certain conditions.

7. Sine wave control

This is a way to control the motor current. To put it the key point, the power-assisted motor controlled by sine wave tends to be absolutely stable in current pulsation, with smooth speed changes, energy transfer does not pulsate, it is not easy to cause motor jitter, and the operating noise is lower.

What is a sine wave? The single most single signal in the frequency component is named because its waveform resembles a mathematical sine curve. We can understand it a little bit here, so I won't elaborate on it. The principle of sine wave control is to modulate multiple pulse signals with natural or regular width in each sine cycle, so that the phase angle and area equivalent to the sine function value are modulated at one time. The pulse sequence is equivalent to the sine curve. , To form a sinusoidal current output of equal amplitude and unequal width, by controlling the amplitude and phase of the sinusoidal current, the purpose of controlling the motor torque is achieved.

8. Protection level

Basically all E-BIKE, its motor, battery has the function of waterproof and dustproof, and to measure the strength of this kind of function, it is expressed by the IP protection level. The IP protection level is an international standard and is composed of two numbers: the first number indicates the level of dust and foreign objects intrusion; the second number indicates the degree of airtightness against moisture and water intrusion. The larger the two numbers, the higher the protection level.

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