BRAKE TORQUE ESTIMATOR

Abstract

The present invention provides a braking torque estimation device capable of accurately estimating braking torque at low cost. A braking torque estimation device (20) according to the present invention can be installed in a vehicle (10) having a plurality of wheels (7) with tires, and includes a braking torque calculation unit (26) that calculates a braking torque (Tbi) of the wheels (7). A wheel speed (Vwi) of the wheels (7) and a longitudinal acceleration (ax), which is an acceleration in the longitudinal direction of the vehicle (10), are input to the braking torque estimation device (20).In addition, the braking torque calculation unit (26) calculates a vehicle speed (Vb), a tire longitudinal force (Fxi) of the wheels (7) and a slip rate of the wheels (7) based on the wheel speed (Vwi), a tire load (Fzi) of the wheels (7), the longitudinal acceleration (ax) and tire characteristics of the wheels (7) and calculates the braking torque (Tbi) based on the calculated tire longitudinal force (Fxi).

Claims

[1] A braking torque estimating device capable of being provided for a vehicle including a plurality of wheels with tires, comprising: a braking torque calculation unit for calculating the braking torque of the wheel, wherein a wheel speed of the wheel and a longitudinal acceleration of the vehicle are input; and wherein the braking torque calculation unit calculates a vehicle speed, the tire longitudinal force of the wheel, and the slip rate of the wheel based on the wheel speed, the tire load on the wheel, the longitudinal acceleration, and tire characteristics of the wheel, and calculates the braking torque based on the calculated tire longitudinal force. [2] The braking torque estimating device according to claim 1, comprising: a tire load estimation unit for calculating the tire load using the longitudinal acceleration. [3] The braking torque estimating device according to claim 1, comprising: a tire characteristic estimation unit that determines the relationship between a slip rate and a friction coefficient as the tire characteristic. [4] The braking torque estimating device according to claim 3, wherein the tire characteristic estimating unit determines, as the tire characteristic, a braking coefficient which is a proportional coefficient between the slip rate and the friction coefficient, and determines the braking coefficient based on the longitudinal acceleration, the wheel speed and the tire load when the vehicle accelerates. [5] The braking torque estimating device according to claim 1, wherein the vehicle comprises an electric motor or an internal combustion engine for generating a braking force and a braking device for generating a braking force; and wherein the braking torque calculation unit calculates the braking torque when at least one of the following six conditions is met: 1) the longitudinal acceleration of the vehicle falls within a predetermined range; 2) the wheel speed falls within a predetermined range and the vehicle drives straight; 3) a road surface on which the vehicle travels meets a predetermined condition; 4) the torque generated by the electric motor is less than a predetermined threshold; 5) the torque generated by the internal combustion engine is less than a predetermined threshold; and 6) the braking device is active. [6] The braking torque estimating device according to claim 1, wherein the vehicle includes an electric motor or an internal combustion engine for generating a braking force and a braking device for generating a braking force; and wherein the braking torque calculating unit determines the braking torque generated by the braking device by subtracting the torque generated by the electric motor or the internal combustion engine from the calculated braking torque. [7] The braking torque estimating device according to claim 1, wherein the vehicle comprises an electric motor or an internal combustion engine for generating a braking force and a braking device for generating a braking force; and wherein the braking torque calculation unit determines the torque generated by the electric motor or the internal combustion engine by assuming that the calculated braking torque is the torque generated by the electric motor or the internal combustion engine, or by subtracting the measured braking torque generated by the braking device from the calculated braking torque. [8] The braking torque estimating device according to claim 1, wherein, when the vehicle turns during running, the braking torque calculating unit calculates the braking torque using the lateral acceleration of the vehicle, a steering angle of the wheel, and tire characteristics depending on a side slip angle when the vehicle turns. [9] The braking torque estimating device according to claim 1, which is connected to a braking control device for controlling a braking device, wherein the braking device is an electric braking device provided for the vehicle and comprising an electric motor; and wherein, when calculating the braking torque, the braking control device stores the current of the electric motor and / or a rotational position of the electric motor. [10] The braking torque estimating device according to claim 3, wherein, when the tire characteristics are determined, the tire characteristic estimating unit acquires the condition of a road surface on which the vehicle is running or weather information on a road on which the vehicle is running. [11] The braking torque estimating device according to claim 1, which is connected to a braking control device for controlling a braking device, wherein the braking device is provided for the vehicle and comprises a brake pad and a disc rotor; and wherein, when calculating the braking torque, the brake control device stores the temperature of the brake pad and the speed of the disc rotor. [12] The braking torque estimating device according to claim 3, wherein the vehicle uses front-wheel drive or rear-wheel drive; and wherein the tire characteristic estimation unit determines, as the tire characteristic, a braking coefficient which is a proportional coefficient between the slip rate and the friction coefficient, and determines the braking coefficient based on the tire longitudinal force, the wheel speed and the tire load when the vehicle accelerates. [13] The braking torque estimating device according to claim 3, wherein the vehicle uses four-wheel drive; and wherein the tire characteristic estimation unit determines, as the tire characteristic, a braking coefficient which is a proportionality coefficient between the slip rate and the friction coefficient, and determines the braking coefficient based on the longitudinal acceleration, a ratio of the driving force between front and rear wheels, the wheel speed, and the tire load when the vehicle accelerates.

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