Steering Apparatus Torque Estimation Using Compensation Algorithms
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Solution Overview
Problem
Existing steering systems face challenges in accurately estimating driver torque applied to the steering wheel, as they do not adequately consider various torque components such as gravity, inertia, viscous friction, coulomb friction, and lateral acceleration, leading to inaccuracies in torque estimation.
Innovation Solution
A steering apparatus that includes a torsion bar, a torsion bar torque detection unit, and an electronic control unit capable of computing driver torque by adding torsion bar torque, steering wheel inertia torque compensation, gravity torque compensation, viscous friction torque compensation, coulomb friction torque compensation, and lateral acceleration torque compensation, along with a rotational angle detection unit to determine the steering wheel rotation angle and hands-on state, allowing for precise torque estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If only torsion bar torque is used for driver torque estimation, then the device complexity is low, but the measurement precision of driver torque is insufficient
Solution Approach 1:
The driver torque estimation is segmented into multiple independent torque components: torsion bar torque, inertia torque, gravity torque, viscous friction torque, coulomb friction torque, and lateral acceleration torque. Each component is calculated separately using specific sensors and formulas, then summed to obtain the total driver torque. This segmentation allows for accurate estimation while maintaining clear computational structure.
Solution Approach 2:
The electronic control unit performs multiple functions: it detects torsion bar torque, computes steering wheel rotation angle, calculates various torque components (inertia, gravity, friction), and synthesizes the total driver torque. This multi-functional approach consolidates complexity into a single control unit rather than requiring separate devices for each function.
2Measurement precision
If multiple torque components are considered, then the measurement precision of driver torque is improved, but the device complexity increases
Solution Approach 1:
The system uses readily available sensor data (torsion bar torque, steering angle, vehicle acceleration) and standard computational formulas to automatically calculate all torque components. The electronic control unit self-serves by processing its own sensor inputs through predefined algorithms, eliminating the need for additional complex hardware or manual calibration.
3Measurement precision
If gravity torque compensation is added, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The gravity torque compensation is achieved by calculating the torque based on the steering wheel rotation angle and the known gravity center position. As the steering angle changes, the gravity torque parameter dynamically adjusts according to the formula Tg = mg·dcg·sin(θsw), providing accurate compensation without requiring additional sensors or complex mechanisms.
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
The solution enables high-accuracy estimation of driver torque by considering multiple torque components, improving the accuracy of steering control and reducing driver discomfort during transitions between manual and automatic steering modes.
Implementation Method 1
a torsion bar; a second shaft which is coupled to the first shaft through the torsion bar; a torsion bar torque detection unit detecting a torsion bar torque which is applied to the torsion bar
Implementation Method 2
the steering wheel inertia torque compensation value being a product of a second-order differential value of the steering wheel rotation angle and an inertia moment of the steering wheel
Implementation Method 3
the gravity torque compensation value being a compensation value for a gravity torque to be applied to the first shaft by gravity that acts on a gravity center of the steering wheel
Data Source
AI summary
A steering apparatus includes: a first shaft which is coupled to a steering wheel; a torsion bar; a second shaft which is coupled to the first shaft through the torsion bar; a torsion bar torque detection unit detecting a torsion bar torque which is applied to the torsion bar; and an electronic control unit configured to estimate a driver torque which is applied to the steering wheel by a driver. The electronic control unit is configured to: i) compute a steering wheel rotation angle which is a rotation angle of the steering wheel; and ii) compute a value including an added value, as the driver torque, the added value being a value resulting from adding the torsion bar torque, a steering wheel inertia torque compensation value, and a gravity torque compensation value.