Steering Device Torque Estimation Using Multiple Compensation Values
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Solution Overview
Problem
Existing steering devices fail to accurately estimate driver torque applied to the steering wheel, as they do not consider all contributing torques such as torsion bar torque, steering wheel inertial torque, spiral cable torque, rotating unbalance torque, viscous friction torque, and Coulomb friction torque.
Innovation Solution
A steering device that includes a torsion bar, a spiral cable, a torque sensor, and an electronic control unit to compute driver torque by adding compensation values for inertial, spiral cable, rotating unbalance, viscous friction, and Coulomb friction torques, providing a precise estimation of driver torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If driver torque is estimated using only torsion bar torque and steering wheel inertial torque, then the computation is simple, but the estimation precision is insufficient
Solution Approach 1:
The patent segments the total driver torque into multiple distinct components: torsion bar torque, steering wheel inertial torque, spiral cable torque, rotating unbalance torque, viscous friction torque, and Coulomb friction torque. Each component is calculated separately using specific formulas and then summed to obtain the total driver torque, thereby improving estimation precision while maintaining systematic computation
Solution Approach 2:
The patent introduces an electronic control unit as an intermediary that automatically performs the complex computations of multiple torque components and their summation. This intermediary handles the computational complexity, allowing the system to achieve high-precision driver torque estimation without burdening the overall system architecture
2Measurement precision
If spiral cable torque is not considered in driver torque computation, then the computation is simpler, but the driver torque estimation accuracy deteriorates
Solution Approach 1:
The patent explicitly segments spiral cable torque as a separate component from the total driver torque. It is calculated using the formula Ts = k × θsw, where k is the spiral cable spring constant and θsw is the steering wheel rotation angle. This segmentation ensures that the spiral cable's contribution to the steering system is accurately captured without conflating it with other torque components
3Measurement precision
If rotating unbalance torque and friction torques are not compensated, then the computation is simpler, but the hands-on and hands-off state determination accuracy is reduced
Solution Approach 1:
The patent segments friction-related torques into two distinct components: viscous friction torque (Tv = cv × dθsw/dt) and Coulomb friction torque (Tf = μ × N). Each is calculated separately with its own coefficient and then added to the total driver torque, ensuring that friction effects are accurately compensated without oversimplifying the physical phenomena
Solution Approach 2:
The patent performs preliminary compensation for rotating unbalance torque, viscous friction torque, and Coulomb friction torque before determining hands-on and hands-off states. By pre-calculating these compensation values and incorporating them into the driver torque estimation, the system ensures that state determination is based on accurate torque data that already accounts for these disturbing factors
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
Enables high-precision estimation of driver torque by considering multiple torque components, improving the accuracy of steering wheel operation state determination, including hands-on and hands-off states.
Implementation Method 1
a torsion bar provided at an intermediate portion of a rotary shaft that rotates together with the steering wheel
Implementation Method 2
a spiral cable, a first end of which is connected to a first member that rotates together with the rotary shaft and a second end of which is connected to a second member that is stationary with respect to a vehicle body
Implementation Method 3
The steering wheel inertial torque compensation value is a product of a steering wheel inertial moment and a second-order differential value of the rotational angle of the steering wheel
Implementation Method 4
The rotating unbalance torque may be torque applied to the rotary shaft by a gravitational force that acts on a center of gravity of the steering wheel
Data Source
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AI summary
A steering device includes a steering wheel (2), a torsion bar (10), a spiral cable (33), a torque sensor (11), and an electronic control unit (12). The electronic control unit (12) is configured to compute a rotational angle of the steering wheel (2). The electronic control unit (12) is configured to compute, as driver torque, a value that includes a sum obtained by adding torsion bar torque, a steering wheel inertial torque compensation value, and a spiral cable torque compensation value. The steering wheel inertial torque compensation value is the product of a steering wheel inertial moment and a second-order differential value of the rotational angle of the steering wheel. The spiral cable torque is torque that acts on the steering wheel (2) because of the spiral cable (33).