Motor Torque Gradient Control for Gear Backlash Vibration
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Solution Overview
Problem
Existing motor control systems in vehicles fail to adequately reduce vibration and noise caused by backlash in gears, especially when torque is increased within a low torque range, leading to a rough driving sensation.
Innovation Solution
A motor control unit with a correction determination unit and a torque gradient correction unit that adjusts the torque gradient by multiplying a correction factor by the first torque gradient, reducing the torque increase rate and extending the torque increase time period when the current torque is within a predetermined low torque range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the torque gradient is set high to improve vehicle responsiveness, then vehicle responsiveness is improved, but vibration and noise due to backlash are generated
Solution Approach 1:
The patent applies different torque gradient strategies to different operating conditions: a first torque gradient map is used when torque direction changes (to prevent backlash vibration), while a second torque gradient map with higher gradients is used when torque direction remains constant (to maintain responsiveness). This localized differentiation resolves the contradiction by optimizing for the appropriate criterion in each specific operating regime.
Solution Approach 2:
The system dynamically switches between different torque gradient maps based on real-time detection of torque direction changes. The control unit monitors whether the torque direction has changed and adjusts the torque gradient accordingly, making the system adaptive rather than static. This dynamic adjustment allows the system to maintain high responsiveness when safe and prevent backlash vibration when necessary.
2Object-generated harmful factors
If the torque gradient is lowered in periods before and after torque direction change to prevent backlash vibration, then backlash vibration is reduced, but when torque is retained low without change in torque direction, the period to which low gradient is applied is shorter, whereby roughness due to backlash still occurs
Solution Approach 1:
The patent segments the torque control strategy into two distinct modes: one for when torque direction changes (using the first torque gradient map with lower gradients) and another for when torque direction remains constant (using the second torque gradient map with higher gradients). This segmentation ensures that the low gradient strategy is applied comprehensively to all cases where torque direction changes, including brief periods where torque is retained low, rather than being limited to only pre- and post-transition periods.
Solution Approach 2:
The system performs preliminary detection of torque direction changes and proactively applies the appropriate torque gradient map before backlash vibration can occur. By continuously monitoring torque direction and switching maps in advance, the system prevents roughness due to backlash even during brief periods when torque is retained low, rather than reacting after the problem manifests.
3Device complexity
If a single torque gradient map is used for all torque conditions, then control simplicity is maintained, but gear alignment cannot be sufficiently performed when torque is increased within low torque range
Solution Approach 1:
The patent implements a dynamic torque gradient control system that automatically selects between two torque gradient maps based on torque direction change detection. While this increases control complexity compared to a single static map, the complexity is justified and managed through automated detection and switching logic. The system maintains gear alignment precision by ensuring sufficient torque increase time periods through appropriate map selection, while the automated nature of the switching keeps the operational interface simple for users.
Data Source
AI summary
Disclosed are a backlash vibration reduction apparatus and method capable of sufficiently performing gear alignment even when torque is increased while a vehicle is driven within a low torque range, thereby minimizing rough vibration due to backlash. The backlash vibration reduction apparatus includes a correction determination unit configured to determine whether it is necessary to correct a torque gradient to be applied for an increase to target torque in the state in which the current torque of a vehicle is retained within a predetermined low torque range and a torque gradient correction unit configured to determine a corrected torque gradient in which a torque increase rate per hour is reduced and a torque increase time period is extended by multiplying a correction factor by a first torque gradient as a torque gradient that increases the current torque upon determining that it is necessary to correct the torque gradient.