Vehicle motion estimating system of hybrid type

• US 4,872,116 A
• Filed: 03/20/1989
• Issued: 10/03/1989
• Est. Priority Date: 01/10/1986
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Ito, Ken, Kawabe, Taketoshi
• Primary Examiner(s): Chin, Gary
• Application Number:
  US07/325,119
• Time in Patent Office: 197 Days
• Field of Search: 364/424.01, 364/424.05, 364/602, 364/605, 364/578, 180/79.1, 180/141, 180/142
• US Class Current: 701/41
• CPC Class Codes: B60G 17/0162 mainly during a motion involving steering operation, e.g. cornering, overtaking B60G17/0164 takes precedence
• CPC Class Codes: B60G 17/0182 involving parameter estimation, e.g. observer, Kalman filter
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2600/1873 Model Following
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 2800/24 Steering, cornering
• CPC Class Codes: B60G 2800/70 Estimating or calculating vehicle parameters or state variables
• CPC Class Codes: B60G 2800/9122 ARS - Anti-Roll System Control
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/11 using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance utilising navigation and traffic information in the control strategy B60W20/12
• CPC Class Codes: B60W 2510/20 Steering systems
• CPC Class Codes: B60W 2520/12 Lateral speed
• CPC Class Codes: B60W 40/103 Side slip angle of vehicle body
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01P 3/42 Devices characterised by the use of electric or magnetic means G01P3/66 takes precedence; measuring electric or magnetic values in general G01R
• CPC Class Codes: G06J 1/00 Hybrid computing arrangements digitally-programmed analogue computers G06G7/06

Abstract

A vehicle motion estimating system for estimating a vehicle motion variable such as yaw rate, lateral acceleration, or side slip angle by using a mathematical vehicle model is composed of a digital device such as a microcomputer for digitally solving equations of vehicle motion of a time-varying type such as equations of yawing motion and side slipping motion, and an analog device for solving one or more time-invariant linear differential equation such as an equation of a steering system about a kingpin or an equation of rolling motion.

Claims

1. A vehicle motion estimating system mounted on a vehicle for estimating a vehicle motion variable by solving a mathematical model which is a set of equations of vehicle motion, comprising:

a steering amount sensor for sensing a steering amount of said vehicle;

a vehicle speed sensor for sensing a vehicle speed of said vehicle;

a processing unit connected with said steering amount sensor and said vehicle speed sensor for determining a value of said vehicle motion variable by solving said mathematical model by use of said steering amount and said vehicle speed, and producing an output signal representing said vehicle motion variable,

said processing unit comprising;

a digital device for solving a first subset of said set, said first subset containing a first equation which is one of a nonlinear equation and a time-varying differential equation, and

an analog device for solving a second subset of said set, said second subset containing a second equation which is a time-invariant linear differential equation and which is not contained in said first subset; and

means for controlling said vehicle in response to said output signal of said processing unit.

2. An estimating system according to claim 1 wherein said analog device solves every time-invariant linear differential equation belonging to said set, and said digital device solves the remainder of said set.

3. An estimating system according to claim 2 wherein said time-invariant linear differential equation is a differential equation which can be described by a state equation of a system which is time-invariant and linear.

4. An estimating system according to claim 1 wherein said set comprises an equation of steering system, and said analog device solves said equation of steering system.

5. An estimating system according to claim 4 wherein said set further comprises an equation of side slipping motion and an equation of yawing motion, and said digital device solves said equations of side slipping motion and yawing motion.

6. An estimating system according to claim 5 wherein said set further comprises an equation of rolling motion, and said analog device solves said equation of rolling motion.

7. A vehicle motion estimating system for estimating a vehicle motion variable by solving a mathematical model which is a set of equations of vehicle motion, comprising:

a steering amount sensor for sensing a steering amount of said vehicle;

a vehicle speed sensor for sensing a vehicle speed of said vehicle;

a processing unit connected with said steering amount sensor and said vehicle speed sensor for determining a value of said vehicle motion variable by solving said mathematical model by use of said steering amount and said vehicle speed, and producing an output signal representing said vehicle motion variable,

said processing unit comprising;

a digital device for solving a first subset of said set, said first subset containing a first equation which is one of a nonlinear equation and a time-varying differential equation,

an analog device for solving a second subset of said set, said second subset containing a second equation which is a time-invariant linear differential equation and which is not contained in said first subset; and

means for controlling said vehicle in response to said output signal of said processing unit;

wherein

said set comprises an equation of steering system, and said analog device solves said equation of the steering system, and said set further comprises an equation of side slipping motion and an equation of yawing motion, and said digital device solves said equations of side slipping motion and yawing motion, and wherein

said equation of steering system is an equation given by;

space="preserve" listing-type="equation">I.sub.K δ

.sub.F =K.sub.S (θ

.sub.S /N)-δ

.sub.F)-D.sub.K δ

.sub.F -M.sub.F

wherein M_F equals 2(ξ

_N +ξ

_C)C_F, I_K is a moment of inertia of a kingpin, K_S is a steering stiffness, N is a steering gear ratio, D_K is a viscosity coefficient about a kingpin, δ

_F is a front wheel steer angle, δ

_F is a first derivative of the front wheel steer angle with respect to time, δ

_F is a second derivative of the front wheel steer angle with respect to time, θ

_S is said steering amount, M_F is a self aligning torque, ξ

_N is a pneumatic trail, ξ

_C is a caster trail, and C_F is a front wheel cornering force.

8. An estimating system according to claim 7 wherein said set further comprises an equation of rolling motion, and said equations of side slipping motion, yawing motion and rolling motion are, respectively, expressed as:

space="preserve" listing-type="equation">M(V.sub.y +Vψ

)=2C.sub.F +2C.sub.R

space="preserve" listing-type="equation">I.sub.Z ψ

=2L.sub.F C.sub.F =2L.sub.R C.sub.R

space="preserve" listing-type="equation">I.sub.x φ

=-C.sub.φ

φ

-K.sub.φ

φ

+(H.sub.g +H.sub.φ

)Mα

where

space="preserve" listing-type="equation">C.sub.F =K.sub.F β

.sub.F,C.sub.R =K.sub.R β

.sub.R,

space="preserve" listing-type="equation">β

.sub.F =δ

.sub.F +R.sub.SF φ

-(V.sub.y +L.sub.F ψ

)/V,

space="preserve" listing-type="equation">β

.sub.R =R.sub.SR φ

-(V.sub.y -L.sub.R ψ

)/V,

space="preserve" listing-type="equation">α

=V.sub.y +Vψ

,

and where M is a vehicle mass, I_Z is a yawing moment of inertia, L_F is a distance between a front axle and a vehicle center of gravity, L_R is a distance between a rear axle and the vehicle center of gravity, K_F is front wheel cornering power, K_R is a rear wheel cornering power, I_X is a rolling moment of inertia, Cφ

is a viscosity coefficient of rolling motion, K is a roll stiffness, R_SF is a front roll steer coefficient, R_SR is a rear roll steer coefficient, H_g is a height of the center of gravity, H is a rol center height, ψ

is a yaw rate, ψ

is a yaw acceleration, V_y is a side velocity, V_y is a side acceleration, β

is a side slip angle of the center of gravity, C_R is a rear wheel cornering force, β

_F is a front wheel tire side slip angle, β

_R is a rear wheel tire side slip angle, φ

is a roll angle, φ

is a first derivative of said roll angle with respect to time, and φ

is a second derivative of said roll angle with respect to time.

9. An estimating system according to claim 8 wherein said digital device is connected with said vehicle speed sensor, and arranged to determine said self aligning torque and a lateral acceleration by solving said equations of side slipping motion and yawing motion, said processing unit further comprises an analog to digital converter and a digital to analog converter, and said analog device comprises a first analog computing circuit for receiving as input signals, said steering amount from said steering amount sensor, and said self aligning torque from said digital device through said digital to analog converter, and determining said front wheel steer angle by solving said equation of steering system, and a second computing circuit for receiving, as an input signal, said lateral acceleration from said digital device through said digital to analog converter, and determining said roll angle by solving said equation of rolling motion, and said digital device is connected with said first and second analog computing circuits through said analog to digital converter, and receives said front wheel steer angle and said roll angle through said analog to digital converter.

10. An estimating system according to claim 9 wherein said digital device determines said yaw rate and said side slip angle of the center of gravity in addition to said self aligning torque and said lateral acceleration by solving said equations of side slipping motion and yawing motion by the use of said vehicle speed, said front wheel angle