Electric Motor Torque Control for Backlash Vibration

Solution Overview

Problem

Existing electrified vehicle control methods that limit torque during backlash passage increase backlash passage time, leading to reduced responsiveness in acceleration and deceleration.

Innovation Solution

An electrified vehicle system with a control device that includes a feedforward control section, a timing estimation section, and a torque correction section, which estimates the timing of backlash elimination and applies a correction torque to reduce vibration, thereby maintaining responsiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If torque is continuously limited during backlash passage, then vibration is reduced, but the time required for passage of the dead band increases and responsiveness is lowered

Engineering Contradiction:

Improvebacklash vibrationVSAvoidresponsiveness of acceleration or deceleration

Core Design Contradiction:

Object-generated harmful factorsVSSpeed

Solution Approach 1:

The control device estimates the timing of backlash elimination in advance and applies correction torque proactively at that specific moment, rather than continuously limiting torque throughout the entire backlash passage. This preliminary timing-based intervention reduces vibration effectively while minimizing the duration of torque intervention, thereby preserving vehicle responsiveness.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of continuous torque limitation, the control device applies correction torque periodically or intermittently based on the estimated backlash elimination timing. This periodic intervention achieves vibration reduction while allowing the power transmission system to operate normally during other periods, maintaining acceleration and deceleration responsiveness.

Inventive Principle:

Principle #19Periodic action

2Object-generated harmful factors

If torque is limited during dead band, then vibration due to engagement of power transmission components is reduced, but the time required for passage of the dead band increases

Engineering Contradiction:

Improvevibration due to engagement of gearsVSAvoidbacklash passage time period

Core Design Contradiction:

Object-generated harmful factorsVSLoss of time

Solution Approach 1:

The control device estimates the timing of backlash elimination in advance and applies correction torque proactively at that specific moment, rather than continuously limiting torque throughout the entire backlash passage. This preliminary timing-based intervention reduces vibration effectively while minimizing the duration of torque intervention, thereby preserving vehicle responsiveness.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of applying torque limitation throughout the entire backlash passage, the control device applies correction torque only partially at the critical moment when backlash is eliminated. This partial action is sufficient to reduce vibration while avoiding the time loss associated with continuous torque limitation.

Inventive Principle:

Principle #16Partial or excessive action

3Object-generated harmful factors

If continuous torque limitation is applied to reduce backlash vibration, then vibration is reduced, but acceleration and deceleration performance deteriorates

Engineering Contradiction:

Improvebacklash vibrationVSAvoidacceleration or deceleration performance

Core Design Contradiction:

Object-generated harmful factorsVSPower

Solution Approach 1:

The control device estimates the timing of backlash elimination in advance and applies correction torque proactively at that specific moment, rather than continuously limiting torque throughout the entire backlash passage. This preliminary timing-based intervention reduces vibration effectively while minimizing the duration of torque intervention, thereby preserving vehicle responsiveness.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of continuous torque limitation, the control device applies correction torque periodically or intermittently based on the estimated backlash elimination timing. This periodic intervention achieves vibration reduction while allowing the power transmission system to operate normally during other periods, maintaining acceleration and deceleration responsiveness.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11511629B2Electrified vehicle system and control method of controlling electrified vehicle

Publication Date: 2022.11.29 TOYOTA JIDOSHA KK

AI summary

An electrified vehicle system includes an electric motor coupled to a drive wheel via a plurality of power transmission components and a control device. The control device is configured to act as: a feedforward control section configured based on a transfer function simulating vibration transmission characteristics of a power transmission system, receiving as an input a required torque of the electric motor from a driver, and outputting a base command torque of the electric motor; a timing estimation section estimating, based on information on the power transmission system, a timing at which a backlash between the plurality of power transmission components is eliminated; and a torque correction section applying, to the base command torque, a correction torque for reducing a vibration generated in the power transmission system due to elimination of the backlash, in response to an arrival of the timing estimated by the timing estimation section.