Steering Gear Stiction Detection via Torque Breakaway Rate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The transient stiction condition in manual steering gears, caused by manufacturing tolerances and gear wear, affects steering precision and feel, particularly in electronic power-assisted steering systems, and is difficult to isolate and correct due to its transient nature.
Innovation Solution
A method and system that quantify the stiction condition by generating a stiction metric based on the rate of torque breakaway in a controlled test environment, using a rotary actuator, torque transducer, and controller to impart controlled steering input signals and measure torque output, comparing it to a threshold rate to detect and characterize stiction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional steering test processes are used to evaluate steady-state performance, then steering kinematics and steady-state performance can be assessed, but transient characteristics indicative of stiction condition are ignored and cannot be detected
Solution Approach 1:
The test system applies controlled acceleration profiles to the steering shaft before the stiction condition occurs, creating predictable transient torque conditions that will reveal stiction when it happens. This preliminary action of controlled acceleration enables detection of the transient stiction condition without requiring complex real-time monitoring systems.
Solution Approach 2:
A torque transducer is introduced as an intermediary measurement device between the steering shaft and the control system. This intermediary sensor measures torque variations during acceleration, providing the data needed to detect stiction conditions without directly observing the complex transient mechanical behavior.
2Reliability
If controlled acceleration is applied to the steering shaft, then transient torque characteristics can be measured to detect stiction, but the test system requires additional components including torque transducer and controlled actuator
Solution Approach 1:
The controlled actuator serving as the rotary motor for the steering shaft also functions as the torque source for the test. The same torque transducer that measures steering torque during normal operation is used to detect stiction conditions during accelerated testing. This multi-functionality reduces the need for separate dedicated test equipment.
Solution Approach 2:
The test system changes the acceleration parameter of the steering shaft from normal operational values to controlled high acceleration profiles. This parameter change creates the transient conditions necessary to reveal stiction, allowing detection without requiring complex mechanical modifications to the steering gear itself.
3Measurement precision
If the torque breakaway rate is used as a metric to characterize stiction, then a quantitative measure can be obtained, but the method requires precise measurement and comparison to threshold values
Solution Approach 1:
The control system continuously monitors the torque transducer output during accelerated rotation and compares the measured torque breakaway rate against predetermined threshold values. This feedback mechanism automatically identifies stiction conditions when the rate exceeds thresholds, providing quantitative measurement without requiring complex analysis algorithms.
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 improves the design and validation of manual steering gears by effectively identifying and addressing stiction conditions, enhancing steering precision and feel by focusing on transient characteristics typically ignored in traditional steering tests.
Implementation Method 1
A steering output torque value is measured with respect to the steering axis using a torque transducer simultaneously with rotation of the steering shaft
Implementation Method 2
rotating a steering shaft of the manual steering gear with constant acceleration via the rotary actuator in response to the steering input control signal
Implementation Method 3
determine a torque breakaway rate, compare the torque breakaway rate to a threshold rate, and execute a control action indicative of a detected stiction condition when the threshold rate is exceeded
Data Source
AI summary
A method for characterizing a stiction condition in a manual steering gear includes transmitting a steering input control signal to a rotary actuator, and rotating a steering shaft with constant acceleration, via the rotary actuator, in response to the steering input control signal. A steering output torque is determined while rotating the steering shaft with the constant acceleration, receiving the steering output torque via the controller, and executing a control action when a rate of the received steering output torque exceeds a threshold rate indicative of the stiction condition. A system includes a rotary actuator, a manual steering gear having a steering shaft connected to the rotary actuator, a torque transducer for measuring a steering output torque imparted to the steering shaft by the actuator, and a controller programmed as set forth above.