Autopark Steering Wheel Snap Reduction via Torque Ramp-Out

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Solution Overview

Problem

Tire windup during automatic parking events causes steering wheel angle to snap unexpectedly when the power-steering motor torque is released, leading to undesirable steering wheel jerk, especially when the vehicle is stationary or moving slowly.

Innovation Solution

A system comprising a power-steering motor, a steering-wheel torque sensor, and a controller that ramps out the power-steering motor torque over a set duration or at varying rates to compensate for tire windup, maintaining torque until driver input or vehicle acceleration is detected to prevent steering wheel snap.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If the power-steering motor provides torque during autopark events, then the steering system can complete the parking maneuver, but the steering wheel may snap to a different angle when the motor ceases to provide torque due to tire windup

Engineering Contradiction:

Improveautopark maneuver executionVSAvoidsteering wheel angle stability

Core Design Contradiction:

Extent of automationVSStability of the object's composition

Solution Approach 1:

The controller applies torque to the steering system in advance (during the autopark maneuver) to counteract tire windup effects before the driver needs to take control. This preliminary action ensures that when the driver grabs the steering wheel, the angle remains stable and predictable, preventing sudden snapping movements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses a steering-wheel torque sensor to detect when the driver applies torque to the steering wheel during autopark events. This feedback signal triggers the controller to adjust its torque output accordingly, ensuring smooth transition from automated to manual control and preventing steering wheel snap.

Inventive Principle:

Principle #23Feedback

2Speed

If the power-steering motor torque is reduced quickly to stop autopark event, then the steering system responds faster to driver input, but tire windup causes steering wheel jerk and snap

Engineering Contradiction:

Improveresponse speed to driver inputVSAvoidsteering wheel jerk and snap

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The controller dynamically adjusts the torque reduction rate based on real-time conditions. When the driver inputs torque during autopark, the system transitions from maintaining high torque to reducing torque at a controlled rate, rather than abruptly stopping. This dynamic adjustment balances quick response with smooth steering wheel behavior, preventing jerk and snap.

Inventive Principle:

Principle #15Dynamics

3Stability of the object's composition

If the controller maintains power-steering motor torque during autopark event, then steering wheel snap is prevented, but the system does not respond quickly to driver take-over

Engineering Contradiction:

Improvesteering wheel angle stabilityVSAvoidtime delay in responding to driver input

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The controller applies partial torque (not full torque) during autopark events to maintain steering wheel stability while still allowing for gradual response to driver input. This partial action approach prevents complete locking of the steering system, enabling the driver to take control more quickly while still benefiting from torque assistance to prevent snap.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system effectively mitigates steering wheel snap and jerk by gradually reducing power-steering motor torque to match steering-wheel torque, ensuring smooth transitions from autopark events to driver control, thereby enhancing safety and comfort during automatic parking maneuvers.

Implementation Method 1

As the wheel is turned, portions of the tire near the wheel turn with the wheel while portions of the tire near the contact patch with the ground may resist the turning motion. As a result, a portion of the tire between the wheel and the contact patch may elastically deform. The elastic deformation of the tire, or more specifically the desire of the tire to return to a non-deformed shape, provides the potential energy referred to as tire windup.

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

A power-steering motor is configured to provide steering torque for the vehicle

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 3

A steering-wheel torque sensor is configured to detect torque applied to a steering-wheel by an operator

Methodology Applied

Scientific EffectTorque detection: Torque

Data Source

PatentUS11919568B2Autopark steering wheel snap reduction

Publication Date: 2024.03.05 FORD GLOBAL TECH LLC

AI summary

A system and strategy for reducing rapid steering wheel movement at the end of an autopark maneuver. The strategy includes maintaining or ramping-out power-steering motor torque to reduce steering wheel movement that may occur due to tire windup that has occurred up to that point in the autopark maneuver. The strategy may include the stopping of an autopark maneuver at any time during the maneuver, or functioning at the end of an autopark maneuver. The autopark event may be a park-out maneuver.