Electric Machine Backlash Torque Control for Faster Vehicle Drive-Off
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Solution Overview
Problem
Existing vehicle drivetrain systems experience disruptive oscillations due to backlash, leading to delayed drive-offs and discomfort, as conventional methods like torque ramps and clutch control are inefficient and unreliable, causing unwanted vehicle motion.
Innovation Solution
A method and system that utilize an electrical machine to apply a controlled backlash torque to the drivetrain when no positive drive torque is transferred, eliminating backlash by rotating the drivetrain and maintaining the elimination until drive-off, using braking torque, holding torque, and internal gearbox friction to prevent reoccurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If limiting torque ramps are used to eliminate backlash, then drivetrain oscillations are reduced, but drive-off speed is delayed and vehicle response becomes slow
Solution Approach 1:
The system performs preliminary action by eliminating backlash during vehicle standstill or freewheeling conditions before drive-off occurs. The electrical machine applies controlled torque to rotate the drivetrain and take up backlash in advance, so that when drive-off is requested, the drivetrain is already engaged without oscillations, enabling both stable operation and fast response.
2Speed
If clutch plates are positioned closely together to speed up drive-off, then drive-off delay is reduced, but unwanted vehicle motion may occur due to inexact control
Solution Approach 1:
The system replaces the mechanical clutch control system with an electrical machine-based control system. The electrical machine provides precise and reliable torque control to eliminate backlash without the positioning errors inherent in mechanical clutch systems, enabling both fast drive-off and high reliability simultaneously.
3Stability of the object's composition
If a relatively flat torque ramp is applied to wind up backlash, then drivetrain oscillations are minimized, but torque build-up time is prolonged
Solution Approach 1:
The system uses periodic or phased action by first applying a controlled torque to eliminate backlash during standstill/freewheeling conditions, then transitioning to full torque delivery when backlash is eliminated. This two-phase approach minimizes oscillations during the elimination phase while reducing the overall time loss compared to continuously applying limited torque ramps.
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
This approach reduces drivetrain oscillations, enhances drive-off speed, and extends component lifespan by eliminating backlash before motion, providing a comfortable and powerful driving experience without additional hardware costs or complexity.
Implementation Method 1
controlling the at least one electrical machine to provide a backlash torque having a controlled value for turning the drivetrain if there is a backlash present in the drivetrain
Implementation Method 2
The drivetrain includes a number of components, such as e.g. a clutch, a gearbox/transmission device, shafts, and a differential
Data Source
AI summary
A method and a system for a vehicle comprising: one or more power sources including at least one electrical machine; and a drivetrain for transferring torque between the one or more power sources and at least one drive wheel of the vehicle. The method comprises: controlling, when no positive drive torque (Tdrive) is transferred from the drivetrain to the at least one drive wheel, the at least one electrical machine to provide a backlash torque (Tbacklash) to the drivetrain, the backlash torque (Tbacklash) having a controlled value for turning the drivetrain if there is a backlash present in the drivetrain.