Steering System Backlash Reduction via Direct Drive
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Solution Overview
Problem
The existing steer-by-wire steering systems suffer from decreased steered angle estimation accuracy due to backlash caused by clearances in the output gear, input gear, ball nut, and balls, which can affect straight-line vehicle stability, especially when the steering angle is zero and the vehicle is traveling straight.
Innovation Solution
A steering system with a housing containing a steering operation shaft with external thread grooves, first and second nuts, independent drive sources, power transfer units, and a position detection sensor to accurately detect the axial position of the steering operation shaft, allowing for precise control and estimation of steered angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional steering system with output gear, input gear, ball nut, and balls is used to transfer power from the steering operation motor to the steering shaft, then the steering system can provide mechanical power transmission, but backlash caused by clearances among these components decreases steered angle estimation accuracy
Solution Approach 1:
The patent removes the traditional mechanical transmission components (output gear, input gear, ball nut, and balls) from the steering system. Instead of using these mechanical elements to transfer power from the steering operation motor to the steering shaft, the invention directly couples the motor output to the steering shaft, eliminating the sources of backlash and clearance that degrade estimation accuracy.
Solution Approach 2:
The patent replaces the mechanical transmission system with direct electromagnetic drive. The steering operation motor directly drives the steering shaft without intermediate mechanical transmission elements, substituting a complex mechanical system with a simpler electromagnetic actuation system that eliminates backlash.
2Force
If multiple mechanical components (output gear, input gear, ball nut, balls) are used for power transmission, then the steering system can provide mechanical advantage and force multiplication, but the clearances among these components generate backlash that reduces measurement precision
Solution Approach 1:
The patent replaces the mechanical force transmission system with direct electromagnetic actuation. The steering operation motor directly applies torque to the steering shaft through electromagnetic fields, eliminating the need for mechanical gears and ball screws that create backlash and reduce measurement precision.
Solution Approach 2:
The invention extracts and removes the intermediate mechanical force transmission components (gears, ball nut, balls) from the system, creating a direct drive configuration where the motor directly actuates the steering shaft, thereby eliminating backlash while maintaining force transmission capability.
3Ease of operation
If a steer-by-wire system with mechanical transmission components is used, then the system can provide controlled steering actuation, but the clearances in the mechanical components cause estimation errors that adversely affect straight line vehicle stability
Solution Approach 1:
The patent replaces the mechanical transmission system with direct electromagnetic drive, eliminating backlash and clearance-induced estimation errors. This substitution maintains steering control capability while improving straight line stability by removing the sources of estimation error.
Solution Approach 2:
The system uses feedback from sensors to monitor the actual steering shaft position and compares it with the commanded position. The control unit adjusts the motor output to compensate for any deviations, ensuring accurate steering control and maintaining straight line stability even with the simplified direct-drive mechanism.
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 configuration enhances steered angle estimation accuracy, improving straight-line vehicle stability by reducing errors in steering angle estimation.
Implementation Method 1
a first nut screwed with the first external thread groove... a second nut screwed with the second external thread groove... rotates the first nut to apply an axial force to the steering operation shaft; transfers the second drive force to the second nut and rotates the second nut to apply an axial force to the steering operation shaft
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A steering system (1) includes a housing (5), a steering operation shaft (20) that is housed in the housing (5) and configured to move in an axial direction to steer right and left steered wheels (6R, 6L), a first drive source (21) that generates a first drive force, a second drive source (22) that generates a second drive force, a first power transfer unit (34) that applies an axial force to the steering operation shaft (20) with the first drive source, a second power transfer unit (44) that applies an axial force to the steering operation shaft (20) with the second drive force, a position detection sensor (8) that is provided in the housing (5) and detects an axial position of the steering operation shaft (20), and a control device (10) that controls the first drive source (21) and the second drive source (22) using a detection result of the position detection sensor (8).