Some experts believe that its development is crucial to the practical application of autonomous driving, representing an unavoidable hurdle in the future development of autonomous driving technology and a prerequisite for its true implementation. So what exactly is drive-by-wire technology, and why is it receiving so much attention and importance in the booming field of autonomous driving? Is autonomous driving truly impossible without this technology? This article will provide an in-depth analysis.
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What is drive-by-wire technology?
Automotive fly-by-wire technology originated from aircraft fly-by-wire systems. Pilots no longer control the aircraft's attitude through traditional mechanical or hydraulic circuits. Instead, sensors mounted on the control stick detect the forces and displacements applied by the pilot, converting them into electrical signals. These signals are then processed in the ECU (Electronic Control Unit) and transmitted to the actuators to achieve aircraft control. This technology was later adopted for automobiles.
Automotive drive-by-wire technology is a system that converts the driver's actions into electrical signals via sensors, which are then transmitted to the actuators via cables. Currently, automotive drive-by-wire technologies mainly include: steer-by-wire, throttle-by-wire, brake-by-wire, suspension-by-wire, and gear shifting-by-wire. Sensors distributed throughout the vehicle acquire the driver's intentions and various parameters during vehicle operation in real time, transmitting this information to the controller. The controller analyzes and processes this information to obtain appropriate control parameters, which are then sent to the various actuators to achieve vehicle control and improve the vehicle's steering, power, braking, and ride comfort.
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Key technologies of automotive drive-by-wire
As mentioned above, current drive-by-wire technologies include drive-by-wire shifting systems, drive-by-wire braking systems, drive-by-wire suspension systems, drive-by-wire supercharging systems, drive-by-wire throttle systems, and drive-by-wire steering systems. In future autonomous vehicles, steering levers, brake pedals, and accelerator pedals will no longer be present. The vehicle's intelligent sensing unit will transmit commands to the steering or braking systems via wiring harnesses to achieve vehicle control. Therefore, drive-by-wire steering and drive-by-wire braking are two crucial technologies within this framework.
First, let's talk about steer-by-wire. In fact, Electronic Power Steering (EPS) is very similar to steer-by-wire, but the major difference is that steer-by-wire eliminates the mechanical connection between the steering wheel and the wheels. Sensors obtain the steering wheel's angle data, which the ECU then converts into specific driving force data, using an electric motor to drive the steering gear to turn the wheels. EPS, on the other hand, increases steering force based on the driver's steering angle. Compared to EPS, steer-by-wire is safer, reacts faster, and offers a more flexible steering wheel layout. Currently, this technology is already being used in some high-end sedans, sports cars, and concept cars.
Braking by steer is a crucial and challenging aspect of steer-by-wire technology. Academician Li Deyi, Chairman of the Chinese Association for Artificial Intelligence, stated in a public speech that the mass production of autonomous vehicles faces significant difficulties, largely due to the limitations of steer-by-steer braking. Currently, there are two main types of steer-by-steer technology: hydraulic brake-by-steer (EHB) and electromechanical brake (EMB). EHB evolved from traditional hydraulic brakes, but it represents a significant improvement. It boasts a compact structure, improved braking performance, convenient and reliable control, significantly reduced braking noise, eliminates the need for a vacuum device, and provides a better pedal feel. However, its limitation is that the entire system still relies heavily on brake fluid. The difference between EMB and EHB lies in the fact that EMB eliminates the need for brake fluid and hydraulic components. The braking torque is generated entirely by motor-driven actuators mounted on the four wheels. This eliminates the need for a master cylinder and hydraulic lines, greatly simplifying the braking system structure. More significantly, the elimination of brake fluid reduces pollution.
Regardless of the type of drive-by-wire technology, the goal is clear: to make car structures simpler, lighter, easier to manufacture, and more efficient in operation. For future autonomous driving, drive-by-wire technology can be considered a standard feature.
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Why use drive-by-wire technology?
After understanding drive-by-wire technology, the next question is why this technology is used in the field of autonomous vehicles? In fact, compared with traditional mechanical control systems, drive-by-wire systems use a completely different control method and have unparalleled advantages over mechanical control systems.
First, the car is lighter. With the adoption of the drive-by-wire system, the traditional mechanical control device is eliminated. On the one hand, this greatly reduces the car's curb weight, reduces energy consumption, and also reduces noise and vibration. On the other hand, the removal of traditional mechanical devices and the flexibility of wiring also save a lot of space, improve the ride comfort of the driver and passengers, and facilitate the realization of modular chassis design.
Secondly, the control is more precise. Because sensors are used to collect various parameters of the car, the driver's movements and the degree of adjustment required can also be accurately recorded by the sensors, greatly improving the precision of the control.
Third, the control strategies are more diverse, enabling coordinated control of multiple chassis subsystems to improve various vehicle performance aspects.
Fourth, manufacturing is also simpler. The development of drive-by-wire technology in automobiles can greatly simplify the production, assembly and debugging process, save production costs and development cycles, and also help automobile manufacturers to personalize products according to different user needs.
Fifth, safety is greatly improved. Cars using steer-by-wire systems eliminate the traditional steering shaft, reducing the risk of mechanical injury to the driver in the event of a collision.
Finally, the system's efficiency is greatly improved. All information within the car is transmitted via electrical signals, significantly increasing information transmission efficiency, resulting in faster control and more sensitive responses—crucial for autonomous driving, a field with extremely stringent real-time requirements.
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Current Status and Future Development of Drive-by-Wire Technology
Drive-by-wire technology is not a recent development; it has existed for over 20 years. However, its immaturity previously resulted in a less satisfying user experience compared to traditional mechanical systems. Furthermore, the fact that drive-by-wire technology relies on the vehicle's computer to regulate steering and acceleration made it difficult to clearly define responsibility, hindering its widespread adoption. In recent years, the rapid development of intelligent connected vehicles has revitalized this technology, and its promising market prospects have attracted significant investment from companies and related organizations.
Among them, Schaeffler, a leading global chassis systems integrator, has made significant moves in the past two years. In August 2018, Schaeffler established a joint venture with Paravan GmbH, a leading global provider of drive-by-wire technology. As part of the transaction, the joint venture acquired Paravan's SPACE DRIVE technology. It is understood that SPACE DRIVE was initially developed for people with disabilities and has been on the market for 17 years, replacing bulky mechanical vehicle control systems with a 100% reliable, fully electronic system.
Due to factors such as reliability, fault-tolerant technology, production costs, sensor accuracy, and battery voltage and power, drive-by-wire systems are currently only applicable on a small scale. However, with the reduction in the cost of electronic products, the gradual improvement of chassis control technology, the increasingly stringent requirements for energy conservation, environmental protection, and safety in automobile development, and the extensive and in-depth research on pure electric vehicles, the application of drive-by-wire technology in the field of autonomous driving will gradually become a reality, becoming one of the indispensable core technologies for the future implementation of autonomous driving.
