Wheel speed estimation device

Patent metadata

Field	Value
Publication number	US-10746757-B2
Application number	US-201816173628-A
Country	US
Kind code	B2
Filing date	Oct 29, 2018
Priority date	Oct 30, 2017
Publication date	Aug 18, 2020
Grant date	Aug 18, 2020

Abstract

A wheel speed estimation device is to be applied to a four-wheel drive vehicle including a first coupling device for a rear left-wheel axle and a second coupling device for a rear right-wheel axle. These coupling devices respectively change states of engagement of a left engagement state and a right engagement state to the any one of a completely restraint state, a release state, and an incompletely restraint state. The wheel speed estimation device includes a correction parameter calculator that calculates correction parameters affected by a difference in wheel radius between wheels based on all wheel rotation speed signals, and a wheel speed calculator that calculates wheel speeds based on the wheel rotation speed signals and the correction parameters. Further, the correction parameter calculator stops calculation of the correction parameters when at least one of the left engagement state or the right engagement state is the incompletely restraint state.

First claim

What is claimed is:

1. A wheel speed estimation device to be applied to a four-wheel drive vehicle,
the four-wheel drive vehicle including:
a first coupling device configured to change a rear left-wheel engagement state, which is a state of engagement between a drive output device, to which a driving torque generated by a drive source is to be transmitted via a power transmission device, and a rear left-wheel axle, to which a rear left wheel is coupled, to any one of: a completely restraint state, which is a state in which the rear left-wheel axle rotates integrally with the drive output device; a release state, which is a state in which the rear left-wheel axle rotates freely relative to the drive output device; and an incompletely restraint state, which is a state in which the rear left-wheel axle rotates while slipping relative to the drive output device;
a second coupling device configured to change a rear right-wheel engagement state, which is a state of engagement between the drive output device and a rear right-wheel axle, to which a rear right wheel is coupled, to any one of: a completely restraint state, which is a state in which the rear right-wheel axle rotates integrally with the drive output device; a release state, which is a state in which the rear right-wheel axle rotates freely relative to the drive output device; and an incompletely restraint state, which is a state in which the rear right-wheel axle rotates while slipping relative to the drive output device; and
a controller configured to control the rear left-wheel engagement state by using the first coupling device and to control the rear right-wheel engagement state by using the second coupling device,
the four-wheel drive vehicle being configured such that: when the rear left-wheel engagement state is the completely restraint state while the four-wheel drive vehicle is traveling straight ahead, the power transmission device has, as a predetermined ratio larger than 1, a ratio of a rotation speed of the rear left-wheel axle to an average value of a rotation speed of a front left-wheel axle, to which a front left wheel is coupled, and a rotation speed of a front right-wheel axle, to which a front right wheel is coupled; and when the rear right-wheel engagement state is the completely restraint state while the four-wheel drive vehicle is traveling straight ahead, the power transmission device has a ratio of a rotation speed of the rear right-wheel axle to the average value as the predetermined ratio,

the wheel speed estimation device comprising:
a plurality of rotation speed sensors configured to generate wheel rotation speed signals corresponding to rotation speeds of the front left wheel, the front right wheel, the rear left wheel, and the rear right wheel, respectively;
a correction parameter calculator configured to calculate, for each wheel and based on all the wheel rotation speed signals, a correction parameter that changes depending on a degree of influence given to a wheel speed of each wheel by a difference in wheel radius between wheels; and
a wheel speed calculator configured to calculate the wheel speed of each wheel based on each of the wheel rotation speed signals and each correction parameter,

wherein the correction parameter calculator is configured to stop calculation of the correction parameter when at least one of the rear left-wheel engagement state or the rear right-wheel engagement state is the incompletely restraint state.

2. A wheel speed estimation device according to claim 1 , wherein the correction parameter calculator is further configured to stop calculation of the correction parameter when at least one of the rear left-wheel engagement state or the rear right-wheel engagement state is the completely restraint state.

3. A wheel speed estimation device according to claim 1 ,
wherein the correction parameter calculator is configured to execute calculation of the correction parameter only when the rear left-wheel engagement state and the rear right-wheel engagement state are both the release state and only when the rear left-wheel engagement state and the rear right-wheel engagement state are both the completely restraint state, and
wherein the correction parameter calculator is further configured to:
calculate, when the rear left-wheel engagement state and the rear right-wheel engagement state are both the release state, a calculation parameter correlated to a rotation angle of each wheel in a predetermined period based on each of the wheel rotation speed signals, to thereby calculate the correction parameter by using the calculation parameter; and

calculate, when the rear left-wheel engagement state and the rear right-wheel engagement state are both the completely restraint state, the calculation parameter based on each of the wheel rotation speed signals, to thereby calculate the correction parameter by using the calculation parameter for the front left wheel, the calculation parameter for the front right wheel, a value obtained by dividing the calculation parameter for the rear left wheel by the predetermined ratio, and a value obtained by dividing the calculation parameter for the rear right wheel by the predetermined ratio.

4. A wheel speed estimation device according to claim 1 ,
wherein the correction parameter calculator is configured to update, during one trip period from start of a current operation of the four-wheel drive vehicle to end of the current operation, the correction parameter every time a predetermined period elapses when calculation of the correction parameter is not stopped, and
wherein the correction parameter calculator is further configured to:
initialize the correction parameter when the four-wheel drive vehicle starts the current operation; and
stop update of the correction parameter from when a first convergence condition and a second convergence condition are both satisfied until the end of the current operation, the first convergence condition being satisfied when a magnitude of a deviation between a current correction parameter, which is a correction parameter updated at a current time and a previous correction parameter, which is a correction parameter updated the predetermined period before the current time, at which the correction parameter is updated, is equal to or smaller than a first predetermined deviation, the second convergence condition being satisfied when at least one of a condition that a magnitude of a deviation between a correction parameter for the front left wheel and a correction parameter for the front right wheel is equal to or smaller than a second predetermined deviation or a condition that a magnitude of a deviation between a correction parameter for the rear left wheel and a correction parameter for the rear right wheel is equal to or smaller than a third predetermined deviation is satisfied.

5. A wheel speed estimation device according to claim 2 ,
wherein the correction parameter calculator is configured to update, during one trip period from start of a current operation of the four-wheel drive vehicle to end of the current operation, the correction parameter every time a predetermined period elapses when calculation of the correction parameter is not stopped, and
wherein the correction parameter calculator is further configured to:
initialize the correction parameter when the four-wheel drive vehicle starts the current operation; and
stop update of the correction parameter from when a first convergence condition and a second convergence condition are both satisfied until the end of the current operation, the first convergence condition being satisfied when a magnitude of a deviation between a current correction parameter, which is a correction parameter updated at a current time, and a previous correction parameter, which is a correction parameter

Assignees

• Toyota Motor Co Ltd

Inventors

• Watanabe Ryochi

Classifications

• G01P3/481 Primary

  of pulse signals · CPC title

• B60W30/00

  Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units · CPC title

• G01P3/443 Primary

  mounted in bearings (bearings F16C) · CPC title

• G01P21/00

  Testing or calibrating of apparatus or devices covered by the preceding groups · CPC title

• B60W40/105

  Speed · CPC title