MDPS Rack Bending Friction Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In motor driven power steering systems, excessive friction between the rack bar and the bearing occurs when the rack bar bends due to lateral forces, leading to uneven steering and discomfort during vehicle turns.
Innovation Solution
A system comprising a rack bending signal processor and a friction compensation controller that determines rack bending and applies a friction compensation torque to the motor, calculated by adding a counter-rack bending torque to the basic steering torque, to compensate for the friction between the rack bar and the bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rack bar rigidity is increased to prevent bending, then structural strength is improved, but device complexity and weight increase
Solution Approach 1:
The patent changes the parameter of rack bar rigidity by selecting appropriate material properties and cross-sectional dimensions to achieve sufficient bending resistance while avoiding excessive weight and complexity. This involves optimizing the rigidity parameter within a reasonable range rather than maximizing it indefinitely.
2Strength
If the rack bar rigidity is increased to prevent bending, then structural strength is improved, but weight increases
Solution Approach 1:
The patent optimizes the rack bar weight by adjusting rigidity parameters such as material selection and cross-sectional geometry to achieve the minimum necessary rigidity for preventing bending, rather than using excessive material that would increase weight unnecessarily.
3Ease of operation
If friction compensation torque is applied to counteract rack bending, then steering smoothness is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary anti-action by calculating and applying friction compensation torque in advance based on detected rack bending conditions. The ECU proactively counteracts the bending force before it significantly degrades steering smoothness, rather than reacting after the problem occurs.
Solution Approach 2:
The patent uses feedback by continuously monitoring rack bending conditions through sensors and adjusting the friction compensation torque accordingly. The ECU receives feedback on rack position and bending state, then dynamically modifies the compensation torque to maintain optimal steering smoothness while minimizing energy consumption.
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 solution ensures smooth steering by effectively reducing excessive friction between the rack bar and the bearing, even when the rack bar is bent, thereby enhancing steering comfort and handling during vehicle turns.
Implementation Method 1
excessive friction is generated on the contact surface between the rack bar and the bearing in the rack bar housing
Data Source
AI summary
Disclosed are a system and a method for compensating friction due to rack bending in a motor driven power steering system. The system for compensating friction may include a rack bending signal processor and a friction compensation controller. The rack bending signal processor may determine whether a rack bar bends when a lateral force is transmitted to the rack bar in turn of a vehicle. The friction compensation controller may calculates a friction compensation torque by adding a counter-rack bending torque according to a bending displacement of the rack bar to a basic steering torque of a motor and control a current supplied to the motor to apply the friction compensation torque if it is determined that the rack bar bends.