Since the birth of the car, the steering wheel has always been the operating wheel of the car steering, and by mechanically connecting the steering lever with the steering wheel dial, the vehicle can be steered according to the needs of the driver. With the development of science and technology, electronic control has gradually replaced the design of mechanical connections, such as electronic handbrakes, electronic shift paddles, etc., and the steering has not changed on mass production vehicles. However, at the end of 2021, Toyota released its first pure electric vehicle model bZ4X built with the e-TNGA platform, although this car does not show enough hard power in terms of product strength, but its steer-by-wire system is still very eye-catching. In this issue of the 2021 automotive new technology inventory, we may wish to talk about the "steer-by-wire".
So, what is the sacred nature of steer-by-wire technology? Imagine that in the future of autonomous vehicles, components such as steering levers, brakes and accelerator pedals will no longer be retained. The vehicle's Acceptic unit will transmit commands to the steering or braking system via a harness to achieve vehicle control, i.e. between the driver input interface (steering wheel) and the actuator (steering wheel) is connected by wire control, and there is no direct hydraulic or mechanical connection between them. After the mechanical connection between the steering wheel and the wheel is removed, the steering wheel angle data is obtained by the sensor, and then the ECU converts it into specific driving force data, and then uses the motor to push the steering machine to rotate the wheel.
In fact, Toyota is not the first person to eat crabs, and steer-by-wire technology has been practically applied on the Infiniti Q50 before. However, everyone knows that the failure rate of electronic systems is much higher than that of mechanical systems, and if the electronic system suddenly fails when turning at high speed, the consequences are unimaginable. Therefore, Infiniti installed 3 independent ECU driving computers for the Q50, which must be issued by two or more ECUs to complete the steering, if one suddenly fails, the other two ECUs can ensure normal steering, but if the instructions issued by the three ECUs are all different, then the steering-by-wire cannot work properly, Infiniti has reserved a set of pure mechanical steering system as a backup, in case there is a problem with the wire control, the machinery can be on top.
Therefore, although the steer-by-wire is not a new thing, it has not been used on a large scale at present, which is more or less related to the fact that the technology is not mature enough. Toyota, which has always been conservative, is so bold in using the on-line control steering technology, does that mean that the technology is mature and reliable enough? I believe many people are curious. And with Toyota's influence, the help to promote steer-by-wire technology is not comparable to Infiniti.
Relatively speaking, the steer-by-wire steering compared to the mechanical steering actually has a lot of advantages, the first is that the steering ratio can be freely changed, the steering wheel plays a few laps in the end is completely determined by the ECU driving computer, if you need direct steering feeling, 1:1 steering ratio can be achieved, steering is no longer limited by machinery.
Second, the steering rack and the steering wheel is not physically connected, the steering is no longer subject to the vibration caused by the tire force feedback, the traditional mechanical steering needs to use rubber bushings to slow down the impact, and the steering-by-wire steering can be rigidly mounted on the steering tie rod, the problem of large steering wheel rotation margin is solved, and the rigid connection can speed up the steering response and improve the accuracy.
Third, steer-by-wire can freely change the steering ratio in combination with the driving dynamics of the vehicle, such as driving on the highway and encountering the influence of crosswind, and the ECU can adjust the steering angle in real time by detecting the wind speed. The fourth point will be that the electronic control steering can be combined with the design of automatic driving, if the future automatic driving technology reaches a certain height, after the use of steer-by-wire, the weight of the front of the car can be greatly reduced, and eliminate mechanical wear problems.
Fourth, there is no mechanical steering tube column, which is conducive to the engineer's better occupant protection design and improves the crash safety of the vehicle.
So what are the disadvantages of steer-by-wire? First of all, the steering feedback can only be simulated, Infiniti's wire control steering with the motor to generate resistance to simulate the steering force feedback, from the perspective of everyone for the Q50 general reaction road sense is too false, the simulation force feedback is obviously not the reality of the traditional mechanical steering, the motor can not simulate the direction of the tire force to bring the direction of the jump and small vibration, for the control is not helpful, just like the racing simulator, always can not bring the real driving experience, so the simulation effect is good or bad, or depends on the ability of the engineer.
brief summary:
If you agree that autonomous driving is a big trend, then unfortunately, this "nasty" steer-by-wire technology will also become the mainstream of the future, and the reason for the annoyance is that it may make you lose your sense of the road and the pleasure of driving. The steer-by-wire system eliminates the intermediate shaft connection of the traditional steering system and realizes the non-mechanical connection of the upper steering and lower steering, which is simpler and also conducive to the control of autonomous vehicles. What cannot be done in the era of fuel vehicles can naturally be achieved in the era of electrification.