Slip Ratio Estimation Using Torque and Normal Force
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Solution Overview
Problem
Existing slip ratio estimation techniques for vehicle traction control face challenges in accuracy and speed due to offset errors, integration interval limitations, and the need for additional wheels or advanced tire modeling, which complicates accurate estimation across various vehicle conditions.
Innovation Solution
A slip ratio estimation device and method that acquires rotational speeds and normal reaction forces to calculate friction coefficients and slip ratios, using torque instruction values and rotational speeds, allowing for rapid and accurate estimation without requiring additional wheels or advanced tire modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time integrated values of motor torque and rotational speeds are used to calculate slip ratios, then slip ratio estimation can be performed, but offset errors accumulate and estimation accuracy deteriorates
Solution Approach 1:
The patent replaces the mechanical integration method (time integration of acceleration or torque) with a model-based calculation approach. Instead of integrating values over time which accumulates offset errors, the invention uses tire models and force balance equations to directly calculate slip ratios from measured quantities, eliminating integration drift and improving both accuracy and reliability.
2Measurement precision
If time integration method is used to obtain slip ratios, then slip ratio calculation can be performed, but calculation speed decreases due to integration interval requirements
Solution Approach 1:
The invention substitutes the time-consuming integration process with direct algebraic calculations based on tire models. By using measured torque, rotational speed, and normal force inputs in model-based equations, the system achieves rapid slip ratio estimation without the computational burden of time integration, thereby improving calculation speed while maintaining estimation capability.
3Measurement precision
If non-driving wheel rotational speed is used to estimate vehicle speed, then slip ratio calculation becomes possible, but additional wheel installation is required which increases device complexity
Solution Approach 1:
The patent enables driving wheels to serve dual purposes: both propulsion and speed sensing. By using the rotational speed of driving wheels combined with torque and normal force measurements in model-based calculations, the system estimates vehicle speed without requiring separate non-driving wheels, thereby reducing device complexity while maintaining estimation capability.
4Productivity
If tire drive characteristics modeling is used to calculate slip ratios, then slip ratio estimation can be performed, but modeling accuracy is insufficient for accurate slip ratio estimation under various conditions
Solution Approach 1:
The invention improves upon basic tire modeling by dynamically adjusting model parameters based on operating conditions. The system uses measured normal forces, torque, and rotational speed to update tire friction coefficients and model parameters in real-time, allowing accurate slip ratio estimation across varying conditions such as different road surfaces, vehicle loads, and speeds, thereby resolving the accuracy limitation of fixed-parameter models.
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 precise and rapid slip ratio estimation for each driving wheel, improving traction control accuracy across different driving conditions and vehicle types, while avoiding the need for complex tire modeling or additional sensors.
Implementation Method 1
a friction coefficient information calculation part that calculates friction coefficient information related to each of the plurality of driving wheels on the basis of a torque instruction value for each of the plurality of driving wheels, results of acquisition by the rotational speed acquisition part, and results of acquisition by the normal reaction force information acquisition part
Data Source
AI summary
An acquisition part acquires the rotational speeds of a plurality of driving wheels of a moving vehicle, and normal reaction forces acting on the plurality of driving wheels. Subsequently, a friction coefficient information calculation part calculates friction coefficients relating to the plurality of driving wheels on the basis of torque command values for the plurality of driving wheels transmitted from a torque control part and the results of acquisition by the acquisition part. A slip ratio calculation part calculates the slip ratios of the plurality of driving wheels on the basis of the calculated friction coefficients, and the rotational speeds acquired by the acquisition part. Consequently, the slip ratios of the respective driving wheels are easily, rapidly, and accurately estimated.