Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-08-17
1995-04-04
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303111, B60T 860, B60T 866
Patent
active
054030749
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an antiblocking system for the driven wheels of an axle of a vehicle. More particularly, the present invention relates to an improvement in such a system in order to at least partially compensate for the mechanical coupling between two driven wheels of an axle due to the differential connected therebetween.
Torques are transmitted between the driven wheels of a vehicle as a consequence of their coupling via a differential. This is shown in FIG. 1a. There, the drive wheels are denoted by 1 and 2, the differential by 3 and the gearbox by 4. The rotational wheel speeds are denoted by .omega..sub.1 and .omega..sub.2 respectively, the braking torques by M.sub.B1 and M.sub.B2 respectively, and the drive torques by M.sub.S1 and M.sub.S2 respectively. J are the moments of inertia. FIG. 1b shows the arrangement of FIG. 1a in a representation in terms of control engineering. The variables V.sub.1 and V.sub.2 are gains. It can be seen that the difference in the torques (at 5) of each wheel passes with a gain V.sub.1 to the associated wheel, and with a different gain V.sub.2 to the other wheel where it is superimposed on the torque differential of the respective wheel (at 6). The gains V.sub.1 and V.sub.2 are specified in the form of formulae where ##EQU1##
The integrators 7 convert the torques into rotational wheel speeds .omega..sub.1 and .omega..sub.2. The slip controllers 8 influence the drive torques M.sub.S1 and M.sub.S2.
As FIG. 2 shows, these coupling torques are not considered in previous ABS control concepts. Individual wheel controllers 9 and actuators 10 for brake pressure control are represented in this figure. Block 11 here contains both the controlled system with the (internal) coupling of the two wheel torques, and the two rotational speed sensors for the drive wheels. This coupling acquires a pronounced influence particularly with the driving position engaged, and can impair the control response in ABS braking.
SUMMARY OF THE INVENTION
The above disadvantages can be avoided according to the invention by regarding the driven wheels not as independent, individual controlled systems, but as a multivariable system, and correspondingly designing a multivariable controller for its control. This results both in an improvement of the control quality and in an increase in the stability of the control loop. The concepts to be described are designed such that conventional ABS control algorithms can largely be employed.
According to a first concept or embodiment of the invention, an antiblocking system for the driven wheels of an axle is provided and contains sensors for determining the respective wheel speeds, a two-channel evaluation circuit to which the respective wheel speed signals are fed and which generates brake pressure control signals for the respective wheels, and brake pressure control devices, responsive to the brake pressure signals for varying the brake pressure of the respective wheels to prevent blocked wheels, and wherein decoupling means are provided for at least partially compensating for coupling of the driven wheels due to the differential, with the decoupling means supplementing the evaluation circuit to form a two-variable controller and being connected to produce electronic coupling between the channels downstream of the evaluation circuit, with this decoupling means having a transfer matrix G(z) whose elements G1(z) and G2(z) determine its output variables u'.sub.1 (z) and u'.sub.2 (z) in accordance with the relationships u'.sub.1 (z)=G1(z)u.sub.1 (z)+G2(z)u.sub.2 (z) or u'.sub.2 (z)=G2(z)u.sub.1 (z)+G1(z)u.sub.2 (z), where u'.sub.1 (z) and u'.sub.2 (z) are the respective analog output signals of the two channels of the evaluation circuit and the elements G1(z) and G2(z) of the matrix are constants determined for the purpose of effective decoupling.
According to a further concept or embodiment of the invention, in an antiblock system for the driven wheels of an axle containing sensors for determining the respective wheel sp
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Kreisselmeier Gerhard
Maier Rolf
van Zanten Anton
Graham Matthew C.
Robert & Bosch GmbH
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