The future of automobiles can be simplified as becoming “toy cars”. Even though I did not graduate from an automotive engineering program, when I open a gasoline-powered car, I always become inexplicably thoughtful. However, now when I open a pure electric car, even though I am not particularly knowledgeable, I can still generally see the similarities with the toy cars I played with as a child.
Cars have always been a complex system, with the essence of traditional cars mainly concentrated in the “three major components”: the engine, transmission, and chassis. They are called the essence because of their complex mechanical design, assembly calibration, and cost-quality control, which cannot be achieved overnight. Each component requires long-term accumulation from a supplier or a car company. Cars are difficult, and the difficulty lies in this, which also builds the “moat” of the industry’s core companies. We will continue to briefly introduce their composition, but while praising the ingenuity of the automotive industry, we must also ask a critical question with a critical spirit: why are there fewer and fewer car parts in the new era?
Composition of the core system of traditional cars
The role of the engine is obvious, to provide necessary power for the car. It can be further divided into seven subsystems. The structural components (such as cylinder head, cylinder block, and crankcase) provide installation frames and necessary structural strength for the sub-components; the crankshaft connecting rod mechanism (piston, connecting rod, crankshaft, flywheel, etc.) is the key active component that converts thermal energy into mechanical energy; the supply system (fuel tank, filter, oil pump, injector, regulator, etc.) injects fuel into the combustion chamber on time, with a set quantity and pressure; the valve train (intake and exhaust valves, rocker arms, camshafts, etc.) guides the combustion air to enter and exit the body promptly; the starting device (starter motor, battery, etc.) drives the engine into a normal working cycle from a stationary state; the cooling system (water pump, thermostat, radiator, etc.) dissipates the heat of the heated parts into the air, maintaining the engine’s normal operating temperature; the lubrication system (oil pump, oil filter, lubrication oil passage, etc.) reduces the friction resistance between moving parts through oil flow. Simply put, as a high-heat, high-pressure, high-vibration power component, the engine requires the participation of many peripheral systems to maintain its long-term stable operation.The gearbox is mainly composed of a clutch, a variety of gears, and a hydraulic mechanism. Although there are many types of gearboxes, the core purpose is to change the transmission ratio, expand the range of torque and speed changes (including supporting reverse gear). Why do we need a gearbox? It’s because the engine, like human muscles, has an optimal working condition. It’s very difficult for a person to ride a bicycle uphill continuously, but this can be easily solved by changing the gear ratio of the bicycle. The same goes for the engine. In order to adapt to frequently changing driving conditions and keep the engine operating at a reasonable condition, we need to use the gearbox as a bridge. The gearbox is actually part of the chassis transmission system. It’s singled out because its mechanical design complexity may be the highest in the entire vehicle mechanical structure.
The chassis accepts the power transmitted by the engine and is a system that ensures normal vehicle operation. It is divided into four core subsystems: transmission system, driving system, braking system, and steering system. Simply put, these subsystems will ultimately act on the wheels through non-rigid transmission structures (universal joints, hydraulic pipelines, etc.). The transmission system transfers power to the wheels, the steering system changes the angle of the wheels, the braking system suppresses the rotation of the wheels, and the driving system is used to support the overall weight and buffer the vibration transmitted by the wheels in the opposite direction. Going into more detail:
The transmission system includes the clutch and gearbox mentioned earlier, as well as the main reducer (further lowers the speed to expand the torque), differential (synchronizes the speed difference between the left and right wheels during turning), and universal drive shaft (can continue to transmit power non-rigidly during tire steering and suspension bumps), etc., to further adapt to the power generated by the engine.
The driving system is composed of the car frame (axle), wheels, and suspension, etc., which make up the entire vehicle as a whole, buffer the impact of uneven road surfaces on the vehicle body, and attenuate the vibration during vehicle operation. The car frame and wheels are easy to understand. Here, let’s briefly explain the suspension. Simply put, except for the tires and some brake transmission devices, all equipment on a passenger car can be regarded as an entire rigid body mounted on the car frame. The mechanism connecting the four tires and the entire car body is the suspension. Another important concept needs to be introduced here, that is, unsprung mass and sprung mass. The total weight of the four tires and their associated equipment under the suspension is the unsprung mass, while the total weight of the entire rigid body above the suspension is the sprung mass. This is like tying a weight to your feet when running. To achieve better athletic performance, the two weights must be matched and the unsprung mass minimized as much as possible. In addition, the structure of the suspension itself is also important. It consists of two parts: shock absorber (damping) and spring. The spring can convert energy and cushion the impact, but because it does not consume too much energy itself, it cannot damp vibration. If there is only a spring, the vehicle will frequently bounce up and down. The shock absorber consumes part of the vibrational energy as frictional heat, thereby reducing the vibration, but it cannot replace the spring to provide necessary structural support for the vehicle. Therefore, a suspension system needs to have both of these components.The braking system and steering system are easy to understand. The entire mechanism that delivers the steering instruction and energy from the steering wheel to the wheels through mechanical or electrical structures is called the steering system. The entire mechanism that delivers the braking instruction and energy to the brake caliper through hydraulic or electrical structures is called the braking system. Both systems share a common feature: due to the limited strength of human force, it is impossible to provide all the energy required for steering and braking. Therefore, both systems contain their own power-assistant systems, which employ means such as electric power assistance, hydraulic amplification, vacuum assistance, etc. to amplify the force required for the corresponding operation. In autonomous driving systems, the role of human force is further eliminated, and this series of actions needs to be completely carried out by the vehicle itself. This requirement also runs through the overall development of these two systems.
The essence of the traditional automotive industry is fully demonstrated in the development process of these two systems. These component systems often reflect the highest level of related civilian industrial products, and we must express the necessary respect for them. On the other hand, we need to consider whether these designs conflict with the concept of flexibility. The answer is also yes. All of the aforementioned systems are often associated with complex mechanical designs (gear transmissions, hydraulic transmissions, link arm transmissions). And as long as it is a mechanical system, it often has the following inherent defects:
- Accompanied by inevitable physical wear and mechanical vibration.
- Occupying the valuable user space of the car.
- Generally relying on various related systems such as oil lubrication, cooling and heat dissipation, and gas-liquid exchange.
- A large number of components make assembly and quality control work huge.
- Large calibration difficulty, relying on professional technicians and long-term experience accumulation of enterprises.
- After calibration is locked, it is difficult for the relevant features to change flexibly or be inherited and reused.
- The issue of industry monopoly of traditional key components brought about by the above complexity.
Therefore, under the new development trend, the automotive architecture is also undergoing fundamental changes, the core of which is “electrification” or “demechanization”. We have already mentioned the disadvantages of mechanization. So, how does “electrification” avoid these problems? Let’s continue to read on.
Mechanical components are being replaced one by one
The basic policy of electrification development is to minimize mechanical components and the associated components serving the mechanical structure as much as possible, thereby rapidly reducing the hardware complexity of the entire automotive system and providing better adaptability and flexibility for downstream software systems. With the development of autonomous driving technology and the continuous tightening of automotive emission standards, the directional trend is very clear. The flexible application of motor technology and wire control technology is reducing the dependence of the entire automotive system on mechanical structures, while the development of battery systems is accelerating this process.# Introduction to Electric Motors
An electric motor is a device that generates a rotational magnetic field using energized coils (also known as stator winding), which acts on the central rotor to produce an electromagnetic rotational torque. It can replace internal combustion engines for power output. Compared with traditional internal combustion engines, electric motors have a simpler structure, lower cost, longer lifespan, simpler maintenance, and lower noise levels. The energy conversion efficiency of electric motors is also higher because the stator and rotor do not directly contact each other. In addition, the control of electric motors is more linearized than that of traditional engines, making them more adaptable to autonomous driving systems. Moreover, because the ideal performance range of electric motors is far wider than that of internal combustion engines, complex gearbox mechanical structures can be simplified or even omitted.
Different motor arrangement methods also bring more surprises and possibilities. When two motors work together in the front and rear, the original drive shaft design can be eliminated, and the visible change is the disappearance of the protruding part in the middle of the rear seat. On the other hand, motors arranged independently on the left and right can further replace the functions of the original reducer and differential.
Even more forward-looking and bold designs have originated from the development of hub motors, wire-controlled steering, and wire-controlled braking technologies. It is hoped that the current hydraulic pipeline braking system, the swivel mechanical structure in the steering system, and the universal mechanical structure in the transmission system can be eliminated. Electric motors, steering, and braking mechanisms can be arranged in the spring area and connected only to the control system on the spring by electric signals.
This design has the potential to become the ultimate form of traditional automotive design. The simplification of mechanical structure and the ultimate release of user space may lead to a new understanding of vehicle operation and user space definition.
Although there are still many technical challenges to be overcome before this design can be achieved, such as the problem of excessive weight in the spring area, the maturity of hub motors and wire-controlled braking and steering technologies. However, these are not insurmountable in theory, and the development of relevant technologies is still very promising and in line with the trend of technology.The development trend of batteries can be briefly explained here. The battery system consists of a power battery, a battery management system, and on-board chargers. As the use of electric motors has basically reached industry consensus, the development of batteries mainly focuses on the choice between hybrid and pure electric. Due to the higher energy density of fuels compared to chemical batteries, and the immaturity of battery technology, the problems of service life and loss exist. The combination of “generator + fuel” still has its cost-effectiveness. In the short term, hybrid vehicles have advantages in terms of endurance and cost. However, with the breakthrough of battery and charging technology, accompanied by the mass production of batteries and the reduction of costs, the author believes that electric vehicles are still more suitable as carriers of future autonomous driving technology, and the core logic is still the pursuit of “flexibility” in the era. Power is a flowable energy source, and with the traditional mechanical structure and physical properties of gasoline, hybrid vehicles do not conform to the characteristic of flexibility. Therefore, it is likely to be overturned by pure electric vehicles in a more “network-oriented and flexible” way, which may have little to do with physical energy density, such as the breakthrough of wireless charging technology or changes in traffic organization. The flexibility advantage implied by technology can often compensate for the shortcomings of technology in a single physical characteristic. In addition, the flexibility of battery arrangement is also worth attention. Unlike the fuel tank that stores gasoline, the power storage consists of a large number of small power batteries, so they can be dispersed or embedded in the body for integrated design, which will be very advantageous for space utilization and lightweight.
Summary
In the future development of automobiles, including autonomous driving, to sum up in one sentence: traditional automobiles and practitioners in the transportation industry will not have an easy life! Yes, simplification has brought the depletion of barriers, and new structures have given birth to software development that was not highly valued in the automotive industry before. Under the simplified automotive architecture, software-defined cars have more imagination space. With the landing of autonomous driving and other systems, the automotive and transportation revolution has increasingly affected not only the automotive industry itself but also its practitioners.
The era is forcing us, and we can only choose a more comfortable posture. Let’s work hard together with practitioners.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.