Human Horizons Partners with Aisin to Implement Active Rear Steering Technology

In the era of electrification, skateboard chassis design makes extended wheelbase a trend. As we strive for more space for occupants, how do we balance occupant comfort and flexibility with body dimensions?

Human Horizons HiPhi's in-house development team, together with partners such as Aisin and Bosch, has implemented active rear-wheel steering in all speed ranges as a standard feature on HiPhi Z. The steering angle reaches 13.2° (±6.6°) and can cooperate with other driving assistance technologies to achieve intelligent driving control in different speed ranges, leading the premium electric vehicle market with technical strength.



The 34° four-wheel drive four-wheel steering hub motor technology debuted in 2018, as part of the technical layout five years ahead of time

Traditional mechanical rear-wheel steering is enabled by the addition of soft materials (typically rubber materials) to the rear suspension. The lateral tilt pressure generated by turning causes the soft materials to deform, thereby controlling the angle change of the rear wheels. Because it must be triggered by a certain amount of lateral tilt, this type of passive change cannot achieve precise control, and its application range is relatively limited.

As time advances and technology develops, the rear wheel steering technology has gradually evolved from mechanical to electric, which has improved stability. This has led to the birth of active rear wheel steering technology, which controls the movement of the steering rod to the left and right by the motor to realize the real rear wheel steering function.


As early as 2018, the 34° four-wheel independent steering technology was debuted by Human Horizons. 14 sets of drive technologies and algorithms under different working conditions/modes enabled by precise and independent four-wheel drive and four-wheel steering have been developed for intelligent driving. The technologies can realize "tank turn", "barrier-free drift" and "pan-in parking". It is an important milestone of various advanced R&D innovation projects and has paved the way for subsequent mass-production projects. Technologies such as "active four-wheel steering," "integrated vehicle control," and "distributed drive" have been introduced into various mass-production projects, enabling subsequent models of Human Horizons HiPhi to achieve industry-leading precision handling in the age of electronics.


"Top 10 chassis" made possible by the iterative accumulation of algorithm results and the rear-wheel steering in all speed ranges as a standard feature

Due to the cost of hardware and the difficulty of control logic, active rear wheel steering has long been a feature exclusive to large luxury sedans and SUVs priced above 1 million RMB, offered by manufacturers with strong R&D strength. In the ICV world, luxury models such as the Mercedes-Benz S-Class, BMW 7 Series, Audi Q7, and Porsche 911 offer it as an option. In the EV world, it is still an alien tech exclusive to a limited number of premium models.

Since 2018, Human Horizons HiPhi has built a partnership with Aisin, one of the world's top 500 companies, to create rear-wheel active steering technology by combining the results of Human Horizons' in-house 4WD hub motor demonstrator. The complex vehicle control technology was also developed by Human Horizons. Through close cooperation between the two parties and deep integration of software and hardware, the world's leading technology was applied to the vehicle for the first time, and the corresponding rear wheel active steering technology was mass-produced in China.

HiPhi X, HiPhi's first flagship vehicle, which was delivered in May 2021, is equipped with the 10° active rear wheel steering system which was globally leading at the time. The system allows HiPhi X to intelligently control the rear wheels to steer in the opposite direction of the front wheels at speeds of 40 km/h and below, reducing the turning radius by more than 0.5m to a minimum of 5.8m.

For the second flagship, HiPhi Z, delivered at the end of 2022, Human Horizons once again teamed up with Aisin to develop the active rear-wheel steering system as a standard feature in all speed ranges. The system can be adjusted on demand in all speed ranges, and the maximum rear steering angle can reach an astonishing 13.2°. At high speeds, the front and rear wheels are steered in the same direction, greatly enhancing the vehicle's handling control and extreme driving capability. The rear wheels are steered in the same direction at high speeds. When facing continuous lane changes, the rear wheel steering can greatly reduce pushing and drifting due to understeer or oversteer, provide more accurate rear wheel tracking and higher body stability, and greatly improve driving control and extreme driving ability. In low-speed conditions, the rear wheels can be steered in the opposite direction, achieving a turning radius of just 5.7 m, making it easy to handle scenarios such as parking and U-turns, providing a more comfortable and flexible driving experience.


Based on the industry-leading active rear wheel steering in all speed ranges, IVC (Integrated Vehicle Dynamics Control), a dynamic chassis-integrated control system jointly developed and tuned by Human Horizons and Bosch highly integrates rear wheel steering, braking, and power output. IVC enabled HiPhi Z to achieve a high degree of integration of the entire chassis control, allowing the originally separate controllers and actuators to work together and call each other, forming a better chassis synergy, improving the dynamic response control of the chassis, thus improving the overall vehicle performance. According to the ISO-3888-2 test standard, HiPhi Z can easily achieve a moose test result of over 82km/h.


The R&D history of Human Horizons in the field of EV vehicle control, especially rear wheel steering technology, has continuously demonstrated its leading edge in in-house R&D and resource integration and has also accumulated rich experience in premium product technology for HiPhi dual flagships, consolidating the position advantage and uniqueness of a premium brand. The bold adoption and refined R&D of innovative technologies also show the positive attitude of a technology company toward independent innovation. Previously, HiPhi X and HiPhi Z flagship models won the 2022 "Top 10 Body" and "Top 10 Chassis" awards in China respectively, which also proved the long-term development capability and technological innovation accumulated by Human Horizons HiPhi.

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