Boots – shoes – and leggings
Patent
1992-03-24
1995-03-28
Chin, Gary
Boots, shoes, and leggings
73510, 73518, 180197, 303 95, 303103, B60T 832
Patent
active
054023459
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In order to calculate the brake slip, which is defined by which is formed either with reference to the wheels or with reference to the vehicle, instead of the free-rolling (unbraked) wheel peripheral speed Ffr. Because, generally speaking, describes a method for obtaining Vref and for control to a desired relative slip.
In many applications (for example the control of vehicle yaw motion or transverse motion and observation units for yaw and transverse motion), it is necessary to know the absolute slip as accurately as possible.
The object of the invention is to make it possible to estimate the actual free-rolling wheel peripheral speeds and the vehicle longitudinal speed so that the absolute slip and other derived values can be more accurately determined.
SUMMARY OF THE INVENTION
The above object is achieved according to the present invention by a method for determining the speed of a braked vehicle and/or the free-rolling peripheral speed of at least one of the vehicle wheels with the aid of measurement of the instantaneous wheel speed of the at least one vehicle wheel wherein: the brake pressure on at least one vehicle wheel is periodically reduced (adaptation condition) such that the working point (operating point) of the at least one wheel is located in the substantially linear range of the braking force characteristic as a function of wheel slip; the free-rolling peripheral speed Vfri of the wheel i is determined during the adaptation condition from the instantaneous wheel speed Vri and the braking force F.sub.B i at the associated wheel i; a vehicle speed Vf' referenced, or relative, to a desired point on the vehicle is determined from the free-rolling peripheral speed Vfri using measured parameters for steering angle .delta. and yaw angular velocity .psi. about the vehicle vertical axis, the skew running angle .alpha.i of the wheels, and the vehicle dimensions; the estimated value for the vehicle speed Vf and the acceleration error b.sub.o are obtained using the filter equations ##EQU1## and with the aid of the estimated value Vf referenced to the vehicle point, the steering angle .delta., the yaw rate .psi. and the skew running angle .alpha.i parameters, together with vehicle dimensions referenced to the vehicle point; at least one estimated value Vfri is obtained for the free-rolling speed of the at least one wheel i, where ##EQU2## is the acceleration estimated from the vehicle mass m.sub.F and the braking forces F.sub.B i, b.sub.o is an error term and K1 and K2 are correction amplifications which are positive during the adaptation condition and are zero outside this condition.
According to a preferred feature of the invention, the wheel slip S is determined from the measured value of the wheel speed and the estimated free-rolling wheel speed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic plan view of a four wheeled vehicle showing various geometrical relationships necessary to explain the method according to the invention.
FIGS. 2a and 2b are graphs of braking force as a function of slip for two different skew running angles used to illustrate the respective relative force reductions utilized during the method according to the invention.
FIG. 3 is a graph showing the variation with time of the estimated vehicle speed resulting according to the present invention, the associated wheel speed of a rear wheel, the associated brake pressure of a rear wheel and the associated skew running angle of the rear wheel, as well as the corresponding actual or measured vehicle speed.
FIG. 4 is a block circuit diagram of an arrangement for carrying out the method according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A precondition for the method according to the present invention is that one vehicle wheel (at least) is underbraked from time to time. In these "adaptation phases", the slip should be within the (almost) linear range of the F.sub.B (S) characteristic (FIG. 2a). In order to achieve this, a reduction by .DELTA. F.sub.B is undertake
REFERENCES:
patent: 4818037 (1989-04-01), McEnnan
patent: 4912744 (1990-03-01), Hurst
patent: 4981190 (1991-01-01), Nakayama et al.
patent: 5029089 (1991-07-01), Braschel
patent: 5083631 (1992-01-01), Nakayama
patent: 5157611 (1992-10-01), Ikeda et al.
Chin Gary
Park Collin W.
Robert & Bosch GmbH
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