Electric Power Steering Tuning Device Using Polynomial Approximation
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Solution Overview
Problem
The existing methods for tuning electric power steering apparatuses require a large number of manually determined points for linear interpolation, increasing work cost, while high-order polynomial techniques reduce work cost but increase processing time due to complex calculations.
Innovation Solution
A tuning device that uses a combination of candidate points and high-order polynomial approximation to reduce the number of manually determined points, calculating adjustment points and linear functions to optimize the assist map, thereby reducing work cost and processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If linear interpolation is used with manually determined points, then steering feel can be optimized, but the work cost of tuning increases due to requiring a large number of points
Solution Approach 1:
The patent transforms the assist map from a discrete set of manually determined points into a continuous function represented by polynomial parameters. By changing the representation from point-based to function-based, the system reduces the number of parameters that need manual adjustment while maintaining the ability to optimize steering feel across the entire operating range.
Solution Approach 2:
The patent replaces the manual mechanical process of determining numerous points with an automated computational system that calculates polynomial parameters. This substitution eliminates the need for manual point-by-point tuning and automatically generates the assist map parameters through mathematical computation.
2Loss of time
If high order polynomial is used to approximate the points, then the work cost of tuning is reduced, but the operation processing time increases due to complex calculations
Solution Approach 1:
The patent implements a dynamic parameter selection strategy where the polynomial order is adjusted based on the operating conditions. By using lower-order polynomials when sufficient and higher-order polynomials only when necessary, the system optimizes the balance between tuning efficiency and real-time calculation speed, avoiding unnecessary computational complexity.
Solution Approach 2:
The patent changes the polynomial parameters offline during the tuning phase and stores them in the assist map. During real-time operation, the system only needs to retrieve and apply these pre-calculated parameters through simple interpolation, rather than performing complex polynomial calculations, thus minimizing processing time while maintaining accuracy.
3Stability of the object's composition
If a large number of points are manually determined for linear interpolation, then the changes in steering auxiliary command value can be smoothed, but the productivity of the tuning process decreases
Solution Approach 1:
The patent replaces the manual process of determining numerous points for smooth interpolation with an automated polynomial fitting algorithm. This computational approach automatically generates smooth transitions in the steering auxiliary command value across the entire torque range without requiring manual determination of multiple points, thereby maintaining smoothness while dramatically improving tuning productivity.
Data Source
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AI summary
To reduce the work cost of tuning of an electric power steering apparatus and reduce the operation processing time of a steering auxiliary command value. A tuning device of an electric power steering apparatus assisting steering based on the correspondence relationship between a steering torque and a steering auxiliary command value according to the steering torque, and the tuning device has a candidate point receiving portion receiving a plurality of candidate points represented by a steering torque and a candidate value of the steering auxiliary command value according to the steering torque, a polynomial calculation portion calculating a high order polynomial approximating the plurality of candidate points, an adjustment point calculation portion calculating a plurality of adjustment points, the number of which is larger than the plurality of candidate points and which are represented by the steering torque and the steering auxiliary command value according to the steering torque, based on the high order polynomial, a linear function calculation portion calculating a plurality of linear functions connecting two adjacent points in the plurality of adjustment points, and an adjustment information outputting portion outputting information on the plurality of linear functions in order to adjust the correspondence relationship.