Steering Device Load Management via Motor Control

Solution Overview

Problem

In steer-by-wire systems, it is challenging to manage excessive external forces on the transmission unit due to the mechanical separation of wheels and steering wheels, leading to increased load on components, which complicates making the steering device compact and light.

Innovation Solution

A steering device with an electric motor, a transmission unit, an input determination unit to assess excessive external forces, and a reduction unit to adjust the motor's driving force to prevent overload on the transmission unit, ensuring the load does not exceed the unit's strength limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the strength of components constituting the transmission unit is increased to prevent excessive load, then the reliability of the transmission unit is improved, but the size and weight of the steering device increase

Engineering Contradiction:

Improvereliability of transmission unitVSAvoidweight of steering device

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The control unit proactively determines the likelihood of excessive external force being applied to the transmission unit and preemptively reduces the driving force of the electric motor before the excessive load occurs. This preliminary action prevents the need for oversized components designed to withstand maximum possible forces, allowing the use of lighter, compact components while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the driving force parameter of the electric motor based on the determined likelihood of excessive external force. By adjusting the driving force parameter in real-time according to operational conditions, the system optimizes the load on the transmission unit, enabling the use of lighter components that only need to handle normal operational loads rather than extreme maximum loads.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the strength of components constituting the transmission unit is increased to prevent excessive load, then the reliability of the transmission unit is improved, but the size of the components increases

Engineering Contradiction:

Improvereliability of transmission unitVSAvoidsize of transmission unit

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The control unit proactively determines the likelihood of excessive external force being applied to the transmission unit and preemptively reduces the driving force of the electric motor before the excessive load occurs. This preliminary action prevents the need for oversized components designed to withstand maximum possible forces, allowing the use of lighter, compact components while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the driving force parameter of the electric motor based on the determined likelihood of excessive external force. By adjusting the driving force parameter in real-time according to operational conditions, the system optimizes the load on the transmission unit, enabling the use of lighter components that only need to handle normal operational loads rather than extreme maximum loads.

Inventive Principle:

Principle #35Parameter changes

3Weight of moving object

If resin or other materials having less strength than metals are used to make the steering device light, then the weight of the steering device is reduced, but the strength of the components decreases

Engineering Contradiction:

Improveweight of steering deviceVSAvoidstrength of components

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The control unit proactively determines the likelihood of excessive external force being applied to the transmission unit and preemptively reduces the driving force of the electric motor before the excessive load occurs. This preliminary action creates a safety margin that allows the use of lighter materials like resin without compromising the structural integrity of the transmission unit, as the components are never subjected to excessive forces during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the driving force parameter of the electric motor based on the determined likelihood of excessive external force. By adjusting the driving force parameter in real-time according to operational conditions, the system optimizes the load on the transmission unit, enabling the use of lighter materials that only need to handle normal operational loads rather than extreme maximum loads.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11661105B2Steering device

Publication Date: 2023.05.30 ASTEMO LTD

AI summary

A steering device includes: an electric motor configured to apply a driving force to cause a wheel of a vehicle to roll; a transmission unit configured to transmit the driving force of the electric motor to the wheel; an input determination unit 221 configured to determine whether an excessive external force equal to or greater than a predetermined force is input, or likely to be input, to the transmission unit via the wheel while the electric motor is applying the driving force; and a final target current setting unit 23 configured to, in response to the input determination unit 221 determining that the excessive force is input, or likely to be input, to the transmission unit, reduce the driving force of the electric motor so that a load on the transmission unit does not exceed an upper limit that is preset according to strength of the transmission unit.