Braking distance and stability enhancement via alternating lateral steering impulses in single-axle drive vehicles

Abstract

The invention relates to a vehicle dynamics control method for single-axle drive vehicles aimed at improving stability and reducing braking distance under asymmetric friction conditions (μ-split). The method generates alternating lateral steering impulses within a defined steering angle range and frequency. Each impulse is followed by a neutral phase in which the steering angle returns to zero. During these neutral phases, vehicle dynamics data are evaluated to determine whether further impulses are required. The alternating steering impulses induce a transient lateral redistribution of wheel loads, enabling asymmetric braking force effects without brake pressure modulation or torque intervention. This results in enhanced vehicle stability and reduced braking distance during critical braking scenarios.

Description

00269371-0017 04.12.2025 PCT / DE0ffl2^ / |QQffi118TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025Title of the InventionBraking distance and stability enhancement via alternating lateral steering impulses in singleaxle drive vehiclesTechnical Field

[0001] The invention relates to a vehicle dynamics control method for motor vehicles with single-axle drive (front- or rear-wheel drive), intended to improve vehicle stability and reduce braking distance under asymmetric friction conditions. The method employs software-controlled alternating lateral steering impulses to generate short-term variations of wheel loads.[0001a] The present invention is technically related to German patent applicationDE 102024004430.2 of December 17, 2024. While the earlier application discloses general steering-impulse concepts for restoring stability under grip loss, the present invention applies these principles specifically to braking phases under asymmetric friction conditions in singleaxle drive vehicles and introduces a dedicated control logic for this purpose.Background Art

[0002] DE 102024001 244 A1 (hereinafter: DI) discloses a drive function for vehicles with steer-by-wire steering in which sinusoidal steering movements are applied automatically to improve traction on loose ground. The continuous steering angle profiles are intended to increase traction and avoid getting stuck. DI does not describe discrete steering impulses with intermediate neutral phases or any evaluation of vehicle dynamics data.DE 102005019339 A1 (hereinafter: D2) relates to a vehicle control system with active steering for overcoming off-road obstacles. Steering oscillations are introduced to help maintain the intended path. The disclosure concerns obstacle-crossing scenarios and does not describe side-specific wheel-load transfer during braking operations.

[0003] DE 102015224760 A1 (hereinafter: D3) discloses periodic steering angle profiles for assisting a vehicle that is stuck. These rocking manoeuvres are performed at standstill and do not address braking-distance optimisation in dynamic driving situations.Page 1 to 600269371-0018 04.12.2025 PCT / DE0ffl2^ / |QQffi118•04- TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025DE 11 2020004314 T5 (hereinafter: D4) describes a steering control device that determines a reference steering angle under slip and actuates the steering accordingly. The disclosure does not include alternating impulse sequences with neutral phases.DE 11 2019002782 T5 (hereinafter: D5) relates to rear-wheel steering control in dynamic driving scenarios. The disclosed system determines phase-shifted rear steering angles but does not teach a cycle-based impulse control for braking-distance reduction under -split conditions.

[0004] None of the above references discloses a method in which alternating lateral steering impulses are executed within a defined amplitude and frequency range, with neutral phases in between and evaluation of vehicle-dynamics parameters to determine continuation of the impulses. In particular, no side-specific, cycle-based wheel-load variation for braking-distance reduction in single-axle drive vehicles is described.Object of the Invention

[0005] The object of the invention is to provide a control method which, during critical braking phases under asymmetric friction conditions, generates software-controlled alternating lateral steering impulses to produce a short-term, side-dependent variation of wheel loads. This lateral load variation enables an asymmetric braking effect that stabilises the vehicle and contributes to a reduction of the effective braking distance without requiring brake-pressure modulation or torque intervention.

[0006] The effect of the steering impulses can be explained by the induced roll moment Mroll= h · m · ay· sin (δ)which generates a wheel-load difference that contributes to an asymmetric wheel deceleration. The variables represent the vehicle mass m, centre-of-gravity height h, lateral acceleration ayand steering angle 3. The resulting short-term lateral load redistribution improves braking behaviour under / z- split conditions and supports vehicle stabilisation.

[0007] The physical effect of the alternating steering impulses can be demonstrated with simplified vehicle models in which defined steering deflections at frequencies in the typical vehicle roll-pitch natural frequency range produce measurable lateral wheel-load differences. Even small steering impulses within the stated amplitude range can generate wheel-load variations on the order of several tens of newtons without exceeding typical stability limits such as a yaw rate of approximately ± 8° / s. These load variations contribute to the asymmetric wheel deceleration observed under - split conditions.Page 2 to 600269371-0019 04.12.2025 PCT / DE0ffl2^ / |QQffi118-©03:9TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025

[0008] In front- or rear-wheel drive vehicles, the steering impulses are automatically activated when unstable braking conditions are detected, such as on ice, on a slope or under p-split. The impulses are applied within a steering-angle amplitude of ± 3° to ± 15° and a frequency of 2 to 10 Hz, producing alternating wheel-load variations that dynamically modulate the braking behaviour.

[0009] The method is intended for single-axle drive vehicles without axle decoupling devices. No torque distribution or mechanical intervention is required; the effect arises solely from the steering-induced lateral redistribution of wheel loads.

[0010] Depending on the friction profile, the lateral load redistribution results in asymmetric wheel deceleration that contributes to stabilising the vehicle path. The method does not require brake-pressure modulation and can operate in parallel with existing ABS functions, which adapt the braking forces automatically.

[0011] To avoid instability, the steering impulses are activated only when unstable braking behaviour is detected and are limited by a maximum steering rate, for example about 40° / s, and a short activation duration. The impulse direction is synchronised with the required drift correction so that yaw rate is reduced rather than amplified.

[0012] The steering impulses are terminated once stable vehicle dynamics are detected. The method is implemented in software within existing control units and requires no additional hardware.

[0013] The method can be implemented as a software module on existing electronic control units and communicated via vehicle bus systems. In extended implementations, the activation and frequency of the impulses can be adapted based on vehicle-dynamics parameters such as brake-pressure gradient, yaw rate, steering-angle velocity and lateral acceleration.

[0014] The steering impulses are implemented as short, asymmetric single pulses(for example with a rise time of about 50 ms and a return time of about 300 ms) that serve exclusively to modulate lateral wheel loads. Due to their limited amplitude and frequency, the pulses remain imperceptible to the driver and do not actively change the driving direction.

[0015] Unlike sinusoidal or trapezoidal steering profiles, the impulses are applied as single, non-linear deflections with a brief effect followed by a defined idle phase. This impulse shape enables controlled lateral wheel-load transfer without causing abrupt yaw changes.Page 3 to 600269371-0020 04.12.2025 PCT / DE0ffl2^ / |QQffi118TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025Advantages of the Invention

[0016] The method provides increased stability during braking phases and enables a reduction of braking distance on slippery or n - split surfaces. The controlled lateral load redistribution supports lane keeping and contributes to vehicle stabilisation without requiring additional hardware. The effect mechanism is physically traceable and remains within predetermined stability limits.

[0017] Further advantages include its suitability for single-axle drive configurations, compatibility with existing ABS and ESP systems, and the ability to adapt the impulse parameters to measured vehicle-dynamics data. The method is particularly effective for compact vehicles in asymmetric friction scenarios or downhill braking.

[0018] Due to the limited amplitude and frequency of the pulses, the steering inputs remain largely imperceptible to the driver or are compensated by actuator damping.System Integration

[0019] The method can be implemented as a software module on existing electronic control units and communicated via the vehicle bus system. It can operate in conjunction with higher-level stability functions and is scalable for vehicles equipped with steering actuators. In extended versions, the impulse parameters may be adapted based on vehicle-dynamics data such as brake-pressure gradient, yaw rate, steering-angle velocity and lateral acceleration.

[0020] To avoid possible oversteer caused by asymmetric deceleration, the steering impulses are activated only within a predefined stability window, for example defined by a yaw rate of approximately ± 8° / s. The impulses are deactivated automatically if critical vehicle-dynamics thresholds are exceeded or once a stable driving condition has been restored.Example

[0021] In a front-wheel-drive vehicle descending on snow, asymmetric slip may occur on one side. The alternating steering impulses increase the normal force on the wheel with the higher friction potential, improving wheel deceleration and reducing the tendency of the vehicle to break away.

[0022] Activation occurs only within the defined stability window and is supplemented by lateral-acceleration and brake-pressure analysis. No active wheel-speed differential analysis is required, which distinguishes the method from more complex all-wheel-drive systems.Page 4 to 600269371-0021 04.12.2025 PCT / DE0ffl2^ / |QQffi118TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025Escalating Steering Impulse Modulation with Evaluation Intervals

[0023] In one embodiment, the alternating steering impulses are activated in discrete cycles. A cycle consists of an alternating steering impulse sequence followed by a neutral phase during which the steering angle is returned to zero. A subsequent evaluation interval of predefined duration, typically between 0.3 s and 0.7 s, is used to assess vehicle-dynamics parameters such as yaw rate, deceleration and wheel-speed behaviour. Based on this assessment, it is determined whether a further impulse cycle is required.

[0024] The impulse activation occurs in discrete cycles in which a single alternating steering impulse sequence is executed, followed by an evaluation interval. If insufficient stabilisation is detected, the number of cycles is increased in subsequent stages, typically up to three stages. The impulse frequency remains constant to maintain directional stability and driving comfort.

[0025] If the initial impulse cycle does not result in sufficient stabilisation or deceleration improvement, additional impulse cycles are executed, each followed by a neutral phase with the steering angle returned to zero. The process is escalated up to a predefined maximum number of cycles, after which the steering impulses are terminated automatically once a stable vehicle condition or a target deceleration is achieved. This ensures controlled intervention and prevents continuous activation.

[0026] The method is limited to single-axle drive systems and deliberately avoids mechanical interventions in the drive train, differential or clutch systems. No axle decoupling or active torque redistribution is required or foreseen.Page 5 to 600269371-0022 04.12.2025 PCT / DE0ffl2^ / |QQffi118TACTOS - 2.0 - PCT Description (TACTOS - 2.0)Date: 24 Nov 2025Brief Description of the DrawingsFIG. 1 schematically illustrates the functional principle of the method in a single-axle drive vehicle. Shown are:(T) sensors detecting asymmetric friction conditions,@ activation of alternating lateral steering impulses,@ the resulting differential response at the driven axle contributing to braking-distance optimisation, and(4) deactivation of the system after stabilisation.FIG. 2 shows the temporal progression of alternating steering impulses with neutral phases. The zig-zag line represents the alternating steering deflections, with neutral intervals between them during which vehicle-dynamics data are evaluated. The figure also illustrates the escalation logic, in which one to four consecutive impulse cycles may be executed depending on the detected vehicle response.Page 6 to 600269371-0023 04.12.2025 PCT / DE0S£ / |SQffi118REFERENCE SIGNS LIST PER FIGURE(TACTOS-2.0 - PCT Application)FIG. 1 - System architecture of TACTOS-2.010 -Vehicle12 -Steering system14 - Steering actuator (lef t / right)16 - Brake system18 - Wheel / wheel assembly20 - Vehicle dynamics sensors (wheel-speed, yaw-rate, lateral acceleration) 22 - Control unit (TACTOS-2.0)24 -Communication interfaceFIG. 2 - Alternating steering impulse cycle (T-L)30 - Impulse phase: left steering deflection32 - Impulse phase: right steering deflection34 - Neutral phase (steering angle returns to zero)36 -Evaluation phase38 - ACTOS-based cycle structure (TACTOS-2.0)40 -Time axis42 - Steering angle amplitude (±3° to ±15°)44 - Steering frequency window (2-10 Hz)General reference signsT-L- Alternating lateral steering impulse control (TACTOS-2.0) / / -split — Asymmetric road-friction conditionACTOS- Alternating Control of Torque and Steering cycle (conceptual framework)

Claims

00269371-0025 04.12.2025 PCT / DE0ffl2^ / |QQffi118TACTOS - 2.0 - PCT Claims (TACTOS - 2.0)Date: 24 Nov 2025Claims1 Independent ClaimA method for improving vehicle stability and reducing braking distance of a motor vehicle during braking,characterised in that software-controlled alternating lateral steering impulses are generated within a defined steering angle amplitude range of ± 3° to ± 15° and at a frequency of 2 to 10 Hz,wherein each alternating steering impulse sequence comprises a steering deflection from a zero steering-angle reference position to one lateral direction and back to zero, followed by a steering deflection to the opposite lateral direction and back to zero, and wherein each said alternating steering impulse sequence is followed by a neutral phase in which the steering angle is returned to zero,and vehicle dynamics data including at least yaw rate and deceleration are evaluated during the neutral phase to determine whether the impulse sequence is to be continued, repeated or terminated,such that a transient lateral redistribution of wheel loads is produced which contributes to vehicle stabilisation and braking-distance reduction.2 - 6 Dependent Claims2 The method according to claim 1,wherein the alternating steering deflections are performed to opposite lateral directions around a zero steering-angle reference position, each deflection returning to zero before the next deflection is initiated.3 The method according to any of the preceding claims,wherein the amplitude, frequency or duration of the steering impulses are adaptively adjusted in dependence on measured vehicle-dynamics parameters including at least vehicle speed and lateral acceleration.4 The method according to any of the preceding claims,wherein the generation of the steering impulses does not require brake-pressure modulation or anti-lock braking intervention.5 The method according to any of the preceding claims,wherein activation of the steering impulse sequence is permitted only when the vehicle yaw rate lies within a predefined stability window including a typical range of about ± 8° / s.6 The method according to any of the preceding claims,wherein the control logic is implemented as a software module executed on an existing electronic control unit of the vehicle.

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