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2. The basic structure of electric vehicles The composition of electric vehicles includes electrical drive and control systems, mechanical systems such as driving force transmission, and working devices to complete established tasks. The electric drive and control system is the core of electric vehicles, and it is also the biggest difference from vehicles with internal combustion engines. The electric drive and control system consists of a drive motor, a power supply, and a speed control device for the motor. The other devices of electric vehicles are basically the same as those of internal combustion engine vehicles.
2.1. Power
The power supply provides electric energy to the driving motor of the electric vehicle. The electric motor converts the electric energy of the power supply into mechanical energy, and drives the wheels and working devices through the transmission device or directly. At present, the most widely used power source for electric vehicles is lead-acid batteries, but with the development of electric vehicle technology, many new types of batteries are also under development. These power sources (batteries) mainly include sodium-sulfur batteries, nickel-chromium batteries, lithium batteries, fuel cells, flywheel batteries, etc. The application of new power sources opens up broad prospects for the development of electric vehicles.
2.2. Drive the motor
The function of the drive motor is to convert the electrical energy of the power supply into mechanical energy, and drive the wheels and working devices directly through the transmission device or directly. At present, DC series motors are widely used in electric vehicles, which have "soft" mechanical characteristics, which are very consistent with the driving characteristics of automobiles. However, due to the presence of commutation sparks, DC motors have low specific power, low efficiency, and heavy maintenance workload. With the development of motor technology and motor control technology, it is bound to be gradually used by DC brushless motors (BCDM) and switched reluctance motors. (SRM) and replaced by AC asynchronous motors.
2.3. Motor speed control device
The motor speed control device is set for the speed change and direction change of electric vehicles, and its function is to control the voltage or current of the motor, and complete the control of the driving torque and rotation direction of the motor.
In the early electric vehicles, the speed regulation of the DC motor was realized by connecting resistors in series or changing the number of turns of the motor field coil. Because its speed regulation is stepped, and will produce additional energy consumption or use the structure of the motor is complicated, it is rarely used now. At present, the most widely used electric vehicle is the thyristor chopping speed regulation, which realizes the stepless speed regulation of the motor by uniformly changing the terminal voltage of the motor and controlling the current of the motor. In the continuous development of electronic power technology, it has gradually been replaced by other power transistors (including GTO, MOSFET, BTR and IGBT, etc.) chopper speed regulation devices. From the perspective of technological development, with the application of new drive motors, it will become an inevitable trend that the speed control of electric vehicles will be transformed into the application of DC inverter technology.
In the rotation conversion control of the drive motor, the DC motor relies on the contactor to change the current direction of the armature or magnetic field to realize the rotation conversion of the motor, which makes the circuit complex and reduces the reliability. When an AC asynchronous motor is used for driving, only the phase sequence of the three-phase current of the magnetic field can be changed to change the rotation direction of the motor, which can simplify the control circuit. In addition, the use of AC motor and its variable frequency speed regulation control technology makes the braking energy recovery control of electric vehicles more convenient and the control circuit simpler.
2.4. Transmission
The function of the electric vehicle transmission is to transmit the driving torque of the electric motor to the drive shaft of the vehicle. When the electric wheel is used for driving, most parts of the transmission can often be ignored. Because the electric motor can be started with a load, the clutch of a traditional internal combustion engine vehicle is not needed on an electric vehicle. Because the rotation of the drive motor can be changed through circuit control, the electric vehicle does not need the reverse gear in the internal combustion engine vehicle transmission. When the stepless speed regulation control of the electric motor is adopted, the electric vehicle can ignore the transmission of the traditional vehicle. When using electric wheel drive, the electric vehicle can also omit the differential of the traditional internal combustion engine vehicle transmission system.
2.5. Driving device
The function of the driving device is to turn the driving torque of the motor into a force on the ground through the wheels to drive the wheels to walk. It has the same composition as other cars, consisting of wheels, tires and suspension.
2.6. Steering device
The special device is set up to realize the turning of the car, and consists of a steering gear, a steering wheel, a steering mechanism and a steering wheel. The control force acting on the steering wheel deflects the steering wheel to a certain angle through the steering gear and steering mechanism to realize the steering of the car. Most electric vehicles use front-wheel steering, and electric forklifts used in industry often use rear-wheel steering. The steering devices of electric vehicles include mechanical steering, hydraulic steering and hydraulic power steering.
2.7. Braking device
The brake device of an electric car is the same as other cars, it is set up for the car to slow down or stop, usually by the brake and its operating device. In electric vehicles, there is generally an electromagnetic braking device, which can use the control circuit of the driving motor to realize the generating operation of the motor, so that the energy during deceleration and braking is converted into the current for charging the battery, so as to be recycled.
2.8. Working device
Working devices are specially set up for industrial electric vehicles to complete the work requirements, such as the lifting devices, masts, forks, etc. of electric forklifts. The lifting of the fork and the tilting of the mast are usually completed by a hydraulic system driven by an electric motor.
Recommended Reading : The Future Development Trend Of Electric Vehicles(1)
2.1. Power
The power supply provides electric energy to the driving motor of the electric vehicle. The electric motor converts the electric energy of the power supply into mechanical energy, and drives the wheels and working devices through the transmission device or directly. At present, the most widely used power source for electric vehicles is lead-acid batteries, but with the development of electric vehicle technology, many new types of batteries are also under development. These power sources (batteries) mainly include sodium-sulfur batteries, nickel-chromium batteries, lithium batteries, fuel cells, flywheel batteries, etc. The application of new power sources opens up broad prospects for the development of electric vehicles.
2.2. Drive the motor
The function of the drive motor is to convert the electrical energy of the power supply into mechanical energy, and drive the wheels and working devices directly through the transmission device or directly. At present, DC series motors are widely used in electric vehicles, which have "soft" mechanical characteristics, which are very consistent with the driving characteristics of automobiles. However, due to the presence of commutation sparks, DC motors have low specific power, low efficiency, and heavy maintenance workload. With the development of motor technology and motor control technology, it is bound to be gradually used by DC brushless motors (BCDM) and switched reluctance motors. (SRM) and replaced by AC asynchronous motors.
2.3. Motor speed control device
The motor speed control device is set for the speed change and direction change of electric vehicles, and its function is to control the voltage or current of the motor, and complete the control of the driving torque and rotation direction of the motor.
In the early electric vehicles, the speed regulation of the DC motor was realized by connecting resistors in series or changing the number of turns of the motor field coil. Because its speed regulation is stepped, and will produce additional energy consumption or use the structure of the motor is complicated, it is rarely used now. At present, the most widely used electric vehicle is the thyristor chopping speed regulation, which realizes the stepless speed regulation of the motor by uniformly changing the terminal voltage of the motor and controlling the current of the motor. In the continuous development of electronic power technology, it has gradually been replaced by other power transistors (including GTO, MOSFET, BTR and IGBT, etc.) chopper speed regulation devices. From the perspective of technological development, with the application of new drive motors, it will become an inevitable trend that the speed control of electric vehicles will be transformed into the application of DC inverter technology.
In the rotation conversion control of the drive motor, the DC motor relies on the contactor to change the current direction of the armature or magnetic field to realize the rotation conversion of the motor, which makes the circuit complex and reduces the reliability. When an AC asynchronous motor is used for driving, only the phase sequence of the three-phase current of the magnetic field can be changed to change the rotation direction of the motor, which can simplify the control circuit. In addition, the use of AC motor and its variable frequency speed regulation control technology makes the braking energy recovery control of electric vehicles more convenient and the control circuit simpler.
2.4. Transmission
The function of the electric vehicle transmission is to transmit the driving torque of the electric motor to the drive shaft of the vehicle. When the electric wheel is used for driving, most parts of the transmission can often be ignored. Because the electric motor can be started with a load, the clutch of a traditional internal combustion engine vehicle is not needed on an electric vehicle. Because the rotation of the drive motor can be changed through circuit control, the electric vehicle does not need the reverse gear in the internal combustion engine vehicle transmission. When the stepless speed regulation control of the electric motor is adopted, the electric vehicle can ignore the transmission of the traditional vehicle. When using electric wheel drive, the electric vehicle can also omit the differential of the traditional internal combustion engine vehicle transmission system.
2.5. Driving device
The function of the driving device is to turn the driving torque of the motor into a force on the ground through the wheels to drive the wheels to walk. It has the same composition as other cars, consisting of wheels, tires and suspension.
2.6. Steering device
The special device is set up to realize the turning of the car, and consists of a steering gear, a steering wheel, a steering mechanism and a steering wheel. The control force acting on the steering wheel deflects the steering wheel to a certain angle through the steering gear and steering mechanism to realize the steering of the car. Most electric vehicles use front-wheel steering, and electric forklifts used in industry often use rear-wheel steering. The steering devices of electric vehicles include mechanical steering, hydraulic steering and hydraulic power steering.
2.7. Braking device
The brake device of an electric car is the same as other cars, it is set up for the car to slow down or stop, usually by the brake and its operating device. In electric vehicles, there is generally an electromagnetic braking device, which can use the control circuit of the driving motor to realize the generating operation of the motor, so that the energy during deceleration and braking is converted into the current for charging the battery, so as to be recycled.
2.8. Working device
Working devices are specially set up for industrial electric vehicles to complete the work requirements, such as the lifting devices, masts, forks, etc. of electric forklifts. The lifting of the fork and the tilting of the mast are usually completed by a hydraulic system driven by an electric motor.
Recommended Reading : The Future Development Trend Of Electric Vehicles(1)
