Those who experienced the IONIQ 6, Hyundai Motor’s second dedicated EV, said it was very comfortable to drive because it had good ride quality and was very quiet. People often have a prejudice that general EVs do not have engine noise, so they cannot block road noise and wind noise, and that the ride is solid and heavy because they have a heavy battery. However, the IONIQ 6, developed to create a ‘personal space’ optimized for individual lifestyles, differentiated it from other EVs by focusing on suspension settings for excellent NVH performance, a comfortable ride, and dynamic driving performance. Ui‒je Kim, a senior researcher from Hyundai Motor’s Noise and Vibration Test Team 2, and Jae‒wook Suh, a senior researcher from R&H Test Team 1, talked about how the outstanding quietness and ride comfort were realized.
Q. EVs are known to have a firm ride quality because of their heavy batteries. How did the IONIQ 6 suspension setup go?
Jae‒wook Suh, senior researcher | The IONIQ 6 was developed with the goal of dynamic driving performance in line with the sporty sedan design that inherits the sleek silhouette of the Prophecy concept. By raising the rear suspension bushing rigidity to that of the IONIQ 5, the car reacts and moves in a coherent manner as the driver controls it. In addition, the low center of gravity due to the heavy EV battery and the low posture of the sedan, in addition to the increase in the stiffness of the stabilizer bar that suppresses the rolling motion (the phenomenon that the car moves up and down), will show agility just as sports cars. Thanks to this, the IONIQ 6 has the size of a mid‒size family sedan, but feels fun to drive.
In general, EVs, which are much heavier than internal combustion engines in their class, have stiffer suspension settings to control driving stability. Moreover, the IONIQ 6 required a relatively stiffer suspension setup to improve handling performance for driving pleasure, which inevitably made the ride a bit stiffer. However, we could maintain the ride quality and dynamic handling performance at the same time by using a vertical hydro lower control arm G bush and a frequency‒sensitive high‒performance shock absorber (SDC3, Selective Damping Control) for the front suspension.
Q. Please explain in more detail about the characteristics and application effects of the vertical hydro lower control arm G‒bush utilized for the first time by Hyundai Motor Company.
Jae‒wook Suh, senior researcher | Unlike general rubber bushings, the hydro bushing effectively combines the elasticity of rubber with the resistance of the liquid flow path by encapsulating a liquid inside. General rubber busings have strong elasticity, so they can further reduce vibration caused by uneven surfaces. In other words, only luxury sedans have housed such parts because it absorbs more road vibrations from the wheels, reduces vibrations and shocks transmitted to the driver, and provides a pleasant and comfortable ride.
The automaker first used vertical‒type hydro G bushing installed at the rear of the lower control arm. The vertical hydro bushing has a complicated structure to ideally implement various functions required for the bush, such as durability, vibration reduction, and handling performance improvement. However, the IONIQ 6 achieved the final target performance through the process of repeating evaluation and improving the design of the hydro bush eight times in order to achieve both excellent ride quality and agile handling performance. Even ordinary people who don’t care too much about ride comfort can even notice that the IONIQ 6’s road vibration reduction performance is outstanding.
Q. Is the frequency‒sensitive high‒performance shock absorber (SDC3) the same specifications as those used in current internal combustion locomotives? How was its setting determined to make it best suitable for IONIQ 6?
Jae‒wook Suh, senior researcher | The SDC3 of the IONIQ 6 looks identical on the outside, but the internal structure has been developed differently for optimization. Generally, shock absorbers prevent the car from swaying up and down when going over bumps or turning corners. This is because electric vehicles, which are much heavier than internal combustion engines of the same class, have a large amount of energy moving up and down due to their weight, so conventional hydraulic shock absorbers have limitations in controlling the movement. This makes the driver feel that the car is unstable as it passes fast through small bumps on the road.
SDC3 was completed by adding a frequency‒sensitive valve under the fixed valve that controls the speed of the shock absorber movement inside the piston rod of the current shock absorber. In addition, a new flow path was utilized so that the oil inside the current piston rod could move to the frequency‒sensitive valve chamber. As a result, it increased the damping force under low‒frequency vibration.
The frequency‒sensitive valve effectively controls the rebound phenomenon when the suspension spring is compressed and stretched again by adjusting the damping force according to the frequency of the vibration. In other words, SDC3 is developed to improve ride quality and handling performance at the same time. In order to optimize the ride quality and driving performance of the electric vehicle IONIQ 6, a frequency‒sensitive valve was set and refined to complement the fixed valve. The goal of the IONIQ 6 was to offer more agile handling and a more stable ride at high speeds than the IONIQ 5 did. And in the process, if the steering response of the car becomes slow or the ride comfort becomes too rough, we developed it by adjusting the balance of the two valves to find the optimal point.
Q. In addition to the hydro bush and SDC3, what improvements have been made to complete the excellent ride quality of the IONIQ 6?
Jae‒wook Suh, senior researcher | You can feel the difference in riding comfort not only through vibrations and shocks felt from the seat, but also through the sensation of your hand holding the steering wheel. Because our hands are very sensitive, constant vibrations or foreign shocks are also considered unpleasant ride. The IONIQ 6 increases its support stiffness by adding a bearing in the center of its column to reduce steering wheel vibration. Thanks to this, the vibration of the steering wheel caused by road impact is reduced, making the ride much more luxurious.
Jae‒wook Suh, senior researcher | In order to provide driving pleasure even in everyday corner driving, we conducted tests not only on the circuit course of Namyang Technology Research Center, but also on numerous winding courses in Korea. In order to enable stable movement and a sense of unity in corners large and small even at low speeds, we repeated the process of finely adjusting the SDC3 shock absorber of the IONIQ 6 and continuing the course again. In addition, in order to maintain excellent riding comfort even in extreme driving conditions, high‒speed driving stability was verified on the German Autobahn, an unlimited speed road, in collaboration with the European Institute of Technology. And we constantly communicated with them and improved the level of perfection.
Q. In order to emphasize the quietness, which is the strength of EVs, it seems that the response to road noise and wind noise should be more certain. What areas did you focus on to realize the excellent ride quality of the IONIQ 6?
Ui‒je Kim, senior researcher | IONIQ 6 is a car developed based on E‒GMP, an EV‒dedicated platform. Therefore, it was developed with the goal of achieving the same level of NVH performance as Hyundai’s IONIQ 5 and Kia’s EV6, which have superior performance compared to competitors and share the same platform. Just as different internal combustion locomotives developed on the same platform share many parts, but have slightly different characteristics through detailed tuning, IONIQ 6 has secured basic performance by reflecting NVH‒related platform improvements from the beginning of development to secure basic performance The completeness has been improved through detailed performance verification.
There are various factors that affect the NVH performance of finished vehicles. For this reason, when the chassis, body, and interior systems that make up the IONIQ 6 are integrated, the effect on system components by frequency has been analyzed to improve the NVH performance of each system in a balanced way. In addition, by strengthening local evaluation activities, problems that may occur in various driving environments were identified in advance and improved in advance, and the opinions of local engineers were actively reflected in the development process.
Q. What is the biggest cause of noise and vibration in EVs, and how did you try to prevent them?
Ui‒je Kim, senior researcher | For EVs without an engine, tire noise from the interior is relatively prominent, so improving road noise is important. For this, IONIQ 6 was developed after reviewing all measures to reduce tire noise, reduce suspension vibration, improve body rigidity, and improve sound absorption and insulation performance of interior materials according to the process in which road surface excitation force is transmitted. To reduce tire noise, the IONIQ 6 uses EV‒dedicated tires with sound‒absorbing materials that minimize the internal resonance of the tire.
Also, like other E‒GMP‒based EVs, IONIQ 6 used a detachable front carpet that separated the upper carpet and the lower decoupler, which had been one so far. The carpet installed on the floor panel is made thick and rigid by itself to block noise, so it cannot be completely adhered to it, but the decoupler at the bottom made of thin fabric bends well, so it can adhere to the shape of the floor panel as it is. The decoupler reduces the noise generated by vibrating the floor panel, and has been optimized to fit the shape of the IONIQ 6 panel.
By dividing the previously single part into two, the effect of reducing noise and vibration without increasing weight and cost is enhanced. Although there was a problem that the manufacturing process of parts increased, the mass production was finally successful because of the common goal of improving the NVH performance of IONIQ 6 and smooth consultation with the production team. The front‒separated decoupler is being gradually expanded and used as a component to block load noise.
Q. In order to reduce the noise and vibration transmitted from the tires to the interior, it seems that countermeasures at the level of suspension were also necessary.
Ui‒je Kim, senior researcher | Since the suspension is positioned between the tire and the vehicle body, the road surface excitation force transmitted to the vehicle body at a specific frequency may increase due to suspension resonance. To solve this problem, a dynamic damper was used in the rear cross member to reduce resonance vibration. On the other hand, increasing the rigidity of the vehicle body is an effective measure to improve road noise by reducing the excitation force transmitted to the vehicle body. IONIQ 6 uses more hot stamping to minimize body deformation in the event of a crash while increasing body rigidity, and also increases torsional stiffness. In addition, in order to reduce the vibration that rises from the rear shock absorber, the automaker used a separate reinforcement material that increases the rigidity of the body in the area where the shock absorber is connected and reduces the sound of the peripheral panel.
Q. EVs will not be able to block other noises, including tire and road noise, as engine and exhaust sounds disappear. How did you prepare for this?
Ui‒je Kim, senior researcher | Instead of a powertrain, EVs have a PE (Power Electric) system consisting of an electric motor, an inverter and a speed reducer. It’s not as severe as engines, but these parts also produce noise and vibration. The IONIQ 6 has various measures to reduce PE noise ‒ like a separate upper trim under the cargo barrier divider.
Since the IONIQ 6 is a sedan‒type electric vehicle, like any sedan, there is a shelf where small luggage can be placed behind the head of the rear seat occupant. A separate trim with sound‒absorbing material was installed on the lower part of the shelf to separate the boarding space and the trunk space and simultaneously block PE noise coming through the trunk. At the same time, the position of the vent hole (ventilation hole), which is another inflow path of PE noise, was moved from near the ears of the rear seat occupants to the rear to improve NVH performance while maintaining ventilation performance. In addition, due to the nature of the motor that uses electric power, a separate ground wire attached to the vehicle body is required. twisted and flattened wire) was used.
In fact, it is impossible to see directly without disassembling the parts, but there are measures to reduce noise and vibration in various parts throughout the body. In order to reduce the intake sound coming in through the side mirrors (the noise produced when air leaks through the gap between the inside and outside of the car), the power cable inside is wrapped with a soft material; and a sound‒absorbing material is used to the space between the connecting parts. The finish was focused on reducing wind noise. Reducing the thickness of the body and side mirror connection and improving the shape of the side mirror cover are also measures against wind noise. In addition, a dynamic damper is installed inside the horn cover of the steering wheel to reduce driving vibrations that you can feel while driving. These factors are all NVH factors commonly applied to E‒GMP‒based electric vehicles. These are applied to develop the same NVH performance, although slightly different for each vehicle model.
Q. Please explain the characteristics of the NVH element applied to reduce the wind noise flowing around the vehicle body.
Ui‒je Kim, senior researcher | Wind noise from the upper body was reduced by installing double laminated sound insulation glass in the above‒mentioned side mirror area, front window, and side window. The glass thickness of the side window was changed to 4T (4mm) to enhance the sound insulation performance. Changing the shape of the belt inside and outside the door so that it can be closer to the side glass is another improvement to reduce the wind noise coming through the door. Another of the NVH elements is an undercover mounted on the front and back of the battery to reduce wind noise passing under the body. This not only reduces wind noise, but also improves aerodynamic performance by helping the air flowing under the car flow smoothly to the rear of the car. This undercover covering the front of the lower body was completed through collaboration with the aerodynamic performance development team.
Photography by Dae‒il Choi, Beom‒Seok Kim
HMG Journal Operation Team
group@hyundai.comPursuant to the Creative Commons License (CCL) 2.0, all users can copy, distribute, and transmit Information available on the Hyundai Motor Group Newsroom, or use it for exhibitions and performances. Please note, however, that all information is protected by copyright. Information users must use the information available on the Hyundai Motor Group Newsroom for strictly private/personal purposes only.
HMG Operation Policy