Abstract

The B-spline function representation is commonly used for data approximation and trajectory definition, but filter-based methods for NWLS approximation are restricted to a bounded definition range. We present an algorithm termed NRBA for an iterative NWLS approximation of an unbounded set of data points by a B-spline function. NRBA is based on a MPF, in which a KF solves the linear subproblem optimally while a PF deals with nonlinear approximation goals. NRBA can adjust the bounded definition range of the approximating B-spline function during run-time such that, regardless of the initially chosen definition range, all data points can be processed. In numerical experiments, NRBA achieves approximation results close to those of the Levenberg–Marquardt algorithm. An NWLS approximation problem is a nonlinear optimization problem. The direct trajectory optimization approach also leads to a nonlinear problem. The computational effort of most solution methods grows exponentially with the trajectory length. We demonstrate how NRBA can be applied for a multiobjective trajectory optimization for a BEV in order to determine an energy-efficient velocity trajectory. With NRBA, the effort increases only linearly with the processed data points and the trajectory length.

Highlights

  • B-spline functions, curves, and surfaces are widely used for approximation [1,2,3] and for defining the trajectories of vehicles [4,5], robots [6,7] and industrial machines [8]

  • In Reference [43], we presented the recursive B-spline approximation (RBA) algorithm, which iteratively approximates an unbounded set of data points in the linear weighted least squares (WLS) sense with a B-spline function using a Kalman filter (KF)

  • We presented a filter-based algorithm denoted nonlinear recursive B-spline approximation (NRBA)

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Summary

Introduction

B-spline functions, curves, and surfaces are widely used for approximation [1,2,3] and for defining the trajectories of vehicles [4,5], robots [6,7] and industrial machines [8]. They are common in computer graphics [9,10] and signal processing for filter design and signal representation [11,12,13,14,15]. We address the approximation of a set of data points by a B-spline function in the nonlinear weighted least squares (NWLS) sense as well as the nonlinear optimization of a B-spline trajectory. A Bayesian filter determines the coefficients of the B-spline function

Nonlinear Weighted Least Squares Data Approximation
Trajectory Optimization
Bayesian Filters
Contribution
Structure of the Data Set
Outline
B-Spline Function Representation
Marginalized Particle Filter
Nonlinear Recursive B-Spline Approximation
Initialization
Measurement Update
Time Update with Shift Operation
Effect of the Shift Operation
Numerical Experiments
General Experimental Setup
Effect of Weighting and Nonlinear Measurement Function
Effect of Interval Count
Effect of Particle Count on Convergence
Mean and Standard Deviation of NRBA Error
Conclusions

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