How to conveniently solve the problem of short-distance travel? Bike sharing? electric car? car? Or a new type of electric scooter?
Careful friends will find that small and portable electric scooters have become the first choice for many young people.
Various electric scooters
The most common shape of electric scooters is the L-shaped, one-piece frame structure, designed in a minimalist style. The handlebar can be designed to be curved or straight, and the steering column and the handlebar are generally at about 70°, which can show the curvilinear beauty of the combined assembly. After folding, the electric scooter has a “one-shaped” structure. On the one hand, it can present a simple and beautiful folded structure, and on the other hand, it is easy to carry.
Electric scooters are very popular among everyone. In addition to the shape, there are many advantages:
Portable: The size of electric scooters is generally small, and the body is generally made of aluminum alloy, which is light and portable. Compared with electric bicycles, electric scooters can be easily loaded into the trunk of a car, or carried on subways, buses, etc. , can be used in combination with other means of transportation, very convenient.
Environmental protection: It can meet the needs of low-carbon travel. Compared with cars, there is no need to worry about urban traffic jams and parking difficulties.
High economy: The electric scooter is powered by a lithium battery, the battery is long and the energy consumption is low.
Efficient: Electric scooters generally use permanent magnet synchronous motors or brushless DC motors. The motors have large output, high efficiency, and low noise. Generally, the maximum speed can reach more than 20km/h, which is much faster than shared bicycles.
The composition of the electric scooter
Taking a domestic electric scooter as an example, there are more than 20 parts in the whole car. Of course, these are not all. There is also a motor control system motherboard inside the car body.
Electric scooter motors generally use brushless DC motors or permanent magnet synchronous motors with hundreds of watts and special controllers. The brake control generally uses cast iron or composite steel; lithium batteries have various capacities, which can be adjusted according to your actual needs. Choose, if you have certain requirements for speed, try to choose a battery above 48V; if you have requirements for cruising range, try to choose a battery with a capacity above 10Ah.
The body structure of an electric scooter determines its load-bearing strength and weight. It must have a load-bearing capacity of at least 100 kilograms to ensure that the scooter is strong enough to withstand the test on bumpy roads. At present, the most commonly used electric scooter is aluminum alloy, which is not only relatively light in weight, but also excellent in sturdiness.
The instrument panel can display information such as the current speed and mileage, and capacitive touch screens are generally selected; tires generally come in two types, tubeless tires and pneumatic tires, and tubeless tires are relatively expensive; for lightweight design, the frame is generally made of aluminum alloy. Such an ordinary electric scooter generally sells for between 1000-3000 yuan.
Core Analysis of Electric Scooter Technology
If the components of the electric scooter are disassembled and evaluated one by one, the cost of the motor and control system is the highest. At the same time, they are also the “brains” of the electric scooter. The start, operation, advance and retreat, speed, and stop of the electric scooter depend on All are motor control systems in scooters.
Electric scooters can run quickly and safely, and have high requirements on the performance of the motor control system, as well as high requirements on the efficiency of the motor. At the same time, as a practical means of transportation, the motor control system is required to withstand vibration, withstand harsh environments, and have high reliability.
The MCU works through the power supply, and uses the communication interface to communicate with the charging module and the power supply and power module. The gate drive module is electrically connected with the main control MCU, and drives the BLDC motor through the OptiMOSTM drive circuit. The Hall position sensor can sense the current position of the motor, and the current sensor and speed sensor can form a double closed-loop control system to control the motor.
After the motor starts running, the Hall sensor senses the current position of the motor, converts the position signal of the rotor magnetic pole into an electrical signal, and provides correct commutation information for the electronic commutation circuit to control the switch of the power switch tube in the electronic commutation circuit state, and feed the data back to the MCU.
The current sensor and the speed sensor form a double closed-loop system. The speed difference is input, and the speed controller will output the corresponding current. Then the difference between the current and the actual current is used as the input of the current controller, and then the corresponding PWM is output to drive the permanent magnet rotor. Rotate continuously for reversing control and speed control. Using a double closed-loop system can enhance the anti-interference of the system. The double closed-loop system increases the feedback control of the current, which can reduce the overshoot and oversaturation of the current, and obtain a better control effect, which is the key to the smooth movement of the electric scooter.
Additionally, some scooters are equipped with electronic anti-lock braking systems. The system detects the wheel speed by sensing the wheel speed sensor. If it detects that the wheel is in a locked state, it automatically controls the braking force of the locked wheel so that it is in a state of rolling and sliding (the side slip rate is about 20%) ), ensuring the safety of the owner of the electric scooter.
Electric scooter chip solution
Due to the safety speed limit, the power of general electric scooters is limited to 1KW to 10KW. For the control system and battery of the electric scooter, Infineon provides a complete solution:
The hardware design scheme of the conventional scooter control system is shown in the figure below, which mainly includes the drive MCU, gate drive circuit, MOS drive circuit, motor, Hall sensor, current sensor, speed sensor and other modules.
The most important thing about electric scooters is safe riding. In the previous section, we introduced that there are 3 closed loops to ensure the safety of electric scooters: current, speed and Hall. For these three closed-loop main devices – sensors, Infineon offers a variety of sensor combinations.
The Hall position switch can use the TLE4961-xM series Hall switch provided by Infineon. TLE4961-xM is an integrated Hall-effect latch designed for high-precision applications with superior power supply voltage capability and operating temperature range and temperature stability of the magnetic threshold. The Hall switch is used for position detection, has high detection accuracy, has reverse polarity protection and overvoltage protection functions, and uses a small SOT package to save PCB space.
The current sensor uses the Infineon TLI4971 current sensor:
TLI4971 is Infineon’s high-precision miniature coreless magnetic current sensor for AC and DC measurement, with analog interface and dual fast over-current detection output and passed UL certification. The TLI4971 avoids all negative effects (saturation, hysteresis) common to sensors using flux density technology and is equipped with internal self-diagnostics. The TLI4971′s digitally assisted analog technology design with proprietary digital stress and temperature compensation provides superior stability over temperature and lifetime. The differential measurement principle allows great stray field suppression when operating in harsh environments.
The speed sensor uses the Infineon TLE4922, an active Hall sensor ideal for detecting motion and position of ferromagnetic and permanent magnetic structures, an additional self-calibration module is implemented for optimal precision. It has an operating voltage range of 4.5-16V and comes in a small PG-SSO-4-1 package with enhanced ESD and EMC stability
Physical design skills of electric scooter hardware
Electric scooters also have some particularities in structural design. In the hardware part, the interface used is generally a multi-interface golden finger plug, which is convenient for the stability and reliability of the electrical connection.
In the control system board, the MCU is arranged in the middle of the circuit board, and the gate drive circuit is arranged a little far away from the MCU. During design, attention should be paid to the heat dissipation of the gate drive circuit for consideration. Screw terminal power connectors are provided on the power board for high current interconnection via copper terminal strips. For each phase output, two copper strips form the DC bus connection, connecting all the paralleled half-bridges of that phase to the capacitor bank and the DC power supply. Another copper strip is connected in parallel to the output of the half bridge.
Post time: Dec-23-2022