/Introduction/
Nowadays, automatic driving is no longer a paper talk, but more of a mass production of actual combat preparations. In this process, wire control technology is gradually becoming the focus of enterprise attention and competition because of its importance and necessity. More experts believe that its development is related to whether automatic driving can land, which can be said to be a barrier that cannot be bypassed by the development of future automatic driving technology, and is the premise for automatic driving to truly achieve landing. So what is the wire control technology, why is it so much attention and attention in the hot field of automatic driving, and is it really impossible to play without this technology? This article will take the reader to an in-depth interpretation.
What is by-wire technology?
Automotive wire-by-wire technology originated from the aircraft's fly-by-wire control system, the pilot no longer through the traditional mechanical circuit or hydraulic circuit to control the aircraft's flight attitude, but through the control bar installed on the sensor to detect the pilot applied to it and displacement, and convert it into an electrical signal, in the ECU the signal is processed, passed to the actuator to achieve aircraft control. This technology later migrated to cars.
Automotive wire-by-wire technology is a system that converts the driver's maneuvering action into an electrical signal through a sensor and transmits it to the actuator through a cable. At present, the car's wire control technology mainly includes: steer-by-wire, throttle-by-wire, line-controlled motion, suspension-by-wire, shift-by-wire, etc., through the sensors distributed throughout the car to obtain the driver's operating intention and various parameter information during the driving process of the car in real time, passed to the controller, the controller will analyze and process this information, get the appropriate control parameters to each actuator, so as to achieve the control of the car, improve the steering, dynamics, braking and compliance of the vehicle.
The key technology of automotive wire control
As mentioned above, the current wire control technology includes a shift-by-wire system, a wire-controlled dynamic system, a wire-controlled suspension system, a wire-controlled boosting system, a wire-controlled throttle system and a steer-by-wire system. In the future autonomous vehicles, the steering lever, brake and accelerator pedal will no longer be retained, the vehicle intelligent perception unit will pass the instructions to the steering or braking system through the wiring harness to achieve the control of the vehicle, therefore, the steer-by-wire and the line-controlled movement are two of the most critical technologies.
First of all, the steer-by-wire, in fact, the electronic power steering (EPS) is very close to the steer-by-wire steering, but the big difference is that the steer-by-wire steering cancels the mechanical connection between the steering wheel and the wheel, uses the sensor to obtain the steering wheel angle data, and then the ECU converts it into specific driving force data, and uses the motor to push the steering machine to rotate the wheel. The EPS, on the other hand, increases the steering force based on the driver's corner. Compared to EPS, steer-by-wire is safer, more responsive, and the steering wheel layout is more flexible. At present, the technology has been applied to high-end cars, sports cars and concept cars.
Line control is the key and difficult part of wire control technology. Academician Li Deyi, chairman of the Chinese Engineering Intelligence Society, once said in his public speech that the mass production of autonomous vehicles is difficult, and the important reason is the braking of wire control. At present, there are two main types of technical models of wire control: hydraulic brakes by wire (EHB) and electromechanical brakes (EMB). Among them, EHB is developed on the basis of traditional hydraulic brakes, but compared to traditional hydraulic brakes, EHB has made significant progress, its compact structure, improved braking efficiency, convenient and reliable control, significantly reduced braking noise, no need for vacuum devices, providing a better pedal feeling, but the limitation is that the entire system is basically inseparable from the brake fluid. The difference between the EMB and the EHB is that it no longer requires brake fluid and hydraulic components, and the braking torque is generated entirely by an actuator driven by an electric motor mounted on 4 tires. Therefore, the brake master cylinder, hydraulic pipeline, etc. are cancelled accordingly, which greatly simplifies the structure of the brake system, and more significantly, with the cancellation of the brake fluid, the pollution is reduced.
In fact, no matter what kind of wire control technology, the goal is very clear, in order to make the car structure simpler, lighter weight, more convenient manufacturing, more efficient operation. For future autonomous driving, wire control is also a standard technology.
Why use in-line technology?
After understanding the technology-by-wire, the next question is why adopt this technology in the field of self-driving cars? In fact, compared with the traditional mechanical control system, the wire control system adopts a completely different control method, which has the incomparable advantages of the mechanical control system.
First of all, the car is lighter, after the use of the wire control system, the traditional mechanical control device is discarded, on the one hand, it greatly reduces the maintenance quality of the car, reduces the energy consumption of the car, and also reduces the noise and vibration of the car; on the other hand, the removal of the traditional mechanical device and the flexibility of the wire layout also save a lot of space, improve the driver and passenger riding comfort, and also help to achieve modular chassis design.
Second, the control is more precise, due to the use of sensors to try to collect the parameters of the car, the driver's action of the stroke, the degree of adjustment can also be accurately recorded through the sensor, the accuracy of the control is greatly improved.
Third, the control strategy is more abundant, and the coordinated control of multiple subsystems of the chassis can be realized to improve the performance of the car.
Fourth, the production and manufacturing is also simpler, the development of wire control technology in the car can greatly simplify the process of automobile production, assembly and debugging, save production costs and development cycle, but also conducive to automobile manufacturers according to the needs of users to carry out personalized customization.
Fifth, security has been greatly improved. Cars with steer-by-wire systems, due to the elimination of the traditional steering axle, when the car hits, reduces the damage of mechanical components to the driver.
Finally, the efficiency of the system work is greatly improved. All kinds of information inside the car are transmitted through electrical signals, which greatly improves the efficiency of information transmission, more rapid control, and more responsiveness, which is crucial for autonomous driving, an area where real-time requirements are so strict.
Application status and future development of wire control technology
Wire control technology is not only in recent years, the technology has existed for more than 20 years, but before because of the immaturity of technology, consumers are not as good as the traditional mechanical system, and the wire control technology is regulated by the driving computer for steering, acceleration and other behaviors, it is difficult to sort out the attribution of responsibility, and various factors hinder its popularization and promotion in the market. In recent years, the rapid development of intelligent networked vehicles has brought new vitality to it, and the good market prospects have triggered the competitive investment of enterprises and related institutions.
In August 2018, Schaeffler and Paravan Co., Ltd., the world's leading provider of drive-by-wire technology, established a joint venture with Paravan Co., Ltd., the world's leading provider of drive-by-wire technology, and as part of the transaction, the joint venture company acquired Paravam's SPACE DRIVE technology. It is understood that SPACE DRIVE began to be developed for the disabled, has been used in the market for 17 years, 100% with a reliable all-electronic system instead of bulky mechanical vehicle control system.
Due to the reliability of the wire control system, fault tolerance technology, production costs, sensor accuracy, battery voltage and power and other factors, the wire control system can only be applied in a small range. However, with the reduction of the cost of electronic products, the gradual improvement of chassis control technology, the increasingly strong energy-saving, environmental protection and safety requirements of automobile development, and the extensive and in-depth research of pure electric vehicles, the application of wire control technology in the field of automatic driving will gradually become a reality and become one of the core technologies that cannot be replaced by future automatic driving.
Resources:
[1] https://baike.baidu.com/item/ Introduction to Autonomous Driving Technology/24437530?fr=aladdin