Optimal Slip Ratio Estimator for Traction Control System of Electric Vehicle based on Fuzzy Inference

Abstract

In this paper, we propose the optimal slip ratio estimation method based on Fuzzy Inference. One of the remarkable advantages of electric vehicle (EV) is the quick and precise torque response of electric motor, which realizes a novel traction control system (TCS). To prevent wheel skid phenomena, the optimal slip ratio control has been successfully developed. It maintains the slip ratio to the optimal value which gives the maximum driving force. The remaining problem is how to generate the optimal slip ratio command to the controller. First, we indicate that the effective estimation of the optimal slip ratio is difficult for a simple gradient method, which is one of the well-known optimization methods. Various knowledge obtained by experiments can be easily installed into Fuzzy Inference. Therefore, its estimation performance can be easily improved by accumulation of human experiences. This is a remarkable advantage in nonlinear estima tion of actual road-tire characteristics. The effectiveness of the proposed estimation and control methods is confirmed by numerical simulation.

A review of fuzzy methods in automotive engineering applications

“…Takagi-Sugeno fuzzy model [137] Fuzzy linear regression [9] Fuzzy preview control [138] Model reference adaptive fuzzy control [44] Neuro-fuzzy method [123] Hierarchical fuzzy integral [24] Fuzzy clustering [139] Type-II fuzzy system [140] Sliding mode control [141] Grey predictor [142] PI and PID control [91,143] Genetic algorithm [71,144] Optimization gradient method [145] Multi-objective optimization [108] Variable structure control [146] Reinforcement learning [94] Bayesian methods [147] in automotive engineering applications. The following positions can be especially mentioned in this context:…”

Coordinated control of differential drive assisted steering system with vehicle stability enhancement system

“…The optimal longitudinal slip ratio opt λ is defined by the value to give the peak µ in ( ) µ λ curve, and it depends on the road condition. Some researchers also proposed traction control system based on optimal slip ratio which is estimated using fuzzy inference [14]. In this study, the optimal slip ratio is searched by the gradient method based on the first-order derivative of the variable.…”

Slip mitigation control for an Electric Powered Wheelchair

“…The desire to achieve a specific slip ratio led to several studies in slip control [3], [4], [6], [9], [11]. However, the more fundamental problem is to determine the optimal slip ratio.…”

“…However, λ opt varies with both the terrain type and surface conditions (e.g., degree of wetness). In [5], [6], [9], a proportional plus integral (PI) controller was used to drive λ to λ opt , which was determined offline. The output torque of the PI controller was subtracted from the commanded torque and the actual slip ratio was determined by comparing the velocity of the driven wheels with the velocity of the non-driven wheels.…”