Abstract:
A circuit configuration for an automotive vehicle with anti-lock control and/or traction slip control is equipped with wheel sensors (S1-S4), with circuits for handling and evaluating the sensors signals (respectively 1 and 2-4) and for generating braking pressure control signals and/or traction torque control signals. Further, a compass or compass system (7) is provided whose output signals are feedable to the evaluation circuits (4) and evaluatable for improving control, for identifying cornering, for assessing the driving stability etc. or also for monitoring proper operation.

Description:
This application is a continuation of application Ser. No. 07/673,431 filed Mar. 22, 1991 now abandoned. 
    
    
     This invention relates to a circuit configuration for an automotive vehicle with anti-lock control and traction slip control. In particular, this invention relates to a circuit configuration for an automotive vehicle having an instantaneous positional orientation and having vehicle wheels, and having an operator controlled drivetrain including a prime mover drivingly engaging at least one of the vehicle wheels and a brake system operative to selectively retard rotation of at least one of the vehicle wheels. 
     BACKGROUND OF THE INVENTION 
     Wheel sensors are the main sources for the information needed for control in the known electronic control system for anti-lock control and traction slip control that are available on the market. The rotational behaviour of the individual wheels is measured by means of these sensors and the vehicle speed, or rather the reference speed of the vehicle, is derived from these measured values. By linking the signals it is moreover possible to detect to a more or less reliable extent whether the vehicle momentarily is driving straight onwards or is cornering, whether the friction coefficient is high or low, whether there is a danger of high yawing moments etc. 
     It is likewise known to use vehicle acceleration sensors. Other control systems additionally require braking pressure sensors. 
     For cost reasons, one aim is to get along with as few sensors as possible. On the other hand, there is a need for further information on the momentary behaviour of the vehicle in order to improve control, to exclude misinterpretation of the sensor information and to detect errors, or rather defects, in time. 
     BRIEF DESCRIPTION OF THE INVENTION 
     It is thus a general object of this invention to disclose a circuit configuration which, in a highly reliable manner, adapts anti-lock control and/or traction slip control to the various conditions with an even higher degree of accuracy and which also excludes misinterpretation of the sensor signals in critical situations in which the sensor signals are ambiguous. 
     It now has been found out that this object can be solved with a circuit configuration of the type referred to at the beginning whose special feature consists in that a compass or a compass system is provided whose output signals are feedable to the evaluation circuits and are evaluatable for improving control, in particular for improving accuracy and behaviour of control in critical situations. 
     According to advantageous examples of embodiments of this invention, the output signals of the compass and the information gathered by the sensor signals are evaluatable in the evaluation circuits for identifying cornering and for accessing driving stability. Alteratively, the output signals of the compass are evaluatable in the evaluation circuits for identifying misinformation and faulty control caused by defects, ambiguous sensor information and the like. Alteratively, the evaluation circuits and the compass are only interconnected during predetermined operating conditions during which control by the compass is critical and during which the information gathered by the wheel sensors is ambiguous. 
     According to this invention, in a circuit configuration of this type, it is also possible to use the compass system exclusively for monitoring control, or rather the proper evaluation of the sensor signals, and for triggering warning signals or a cut-off of control in case of trouble. 
     Further characteristics, advantages and applications of this invention will become evident from the following description of an example of an embodiment of this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The sole drawing Figure which, in the form of a (functional) block diagram, represents the main assembly units and components of a circuit configuration according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the drawing figure which represents an example of one embodiment of the present invention, each wheel of an automotive vehicle is equipped with a wheel sensor S1-S4. In a signal processing circuit or trigger circuit 1, the output signals of the individual sensors are processed so that, finally, there is available a signal V R  1-V R  4 which corresponds to the angular velocity of the individual wheels and which can be subjected to further electronic processing. In a stage 2, a reference velocity of the vehicle V REF  is derived from these velocity signals in accordance with known algorithms, said reference velocity of the vehicle V REF  approximately corresponding to the speed of the vehicle. For instance, in some phases of control, the reference velocity of the vehicle corresponds to the speed of the fastest wheel. 
     Further, the first derivative v, as a function of time, of the individual wheel velocities--that is the wheel acceleration or wheel deceleration--and the second derivative v as a function of time, namely the so-called jolt, are formed in a circuit block 3. By comparing the individual wheel velocities with the reference velocity it is possible to determine the wheel slip t. 
     The signals formed in stages 2 and 3 are logically linked and evaluated in evaluation circuits 4. Eventually, braking pressure control signals are available at the outputs A1 of said circuits 4. Said braking pressure control signals are passed on to wheel valves 5 and control the braking pressure in the wheel brake cylinders by actuating said wheel valves. Generally, one pair of inlet and outlet valves is provided per control channel. By means of said valve pair it is possible to keep the braking pressure in the controlled wheels constant to reduce it and to reincrease it depending on the result of the signal evaluation in the circuits 4. 
     In the example of an embodiment represented here, further, so-called ASR valves 6 (ASR=traction slip control) are connected to the outputs A2. In case of excessive traction slip they will come into operation and prevent the wheels from spinning. The signal of an output A3, finally, leads to an engine management system likewise belonging to traction slip control. By controlling, or rather by reducing the torque of the engine of the automotive vehicle it is possible in a known manner to counter act the spinning tendency of a driven wheel. 
     Stage 4 symbolizes the entirety of evaluation circuits. By means of the individual blocks within stage 4 it is suggested that it is possible to subdivide the same again into different functional blocks. The entire circuitry 4, however, also can be realized by one or by a plurality of program-controlled circuits such as microprocessors or microcomputers. The circuit blocks sketched out represent but some of the functional blocks actually needed or used. 
     According to this invention, in addition, a compass or a compass system 7 is provided whose output signals are likewise taken into consideration in the evaluation of the sensor signals derived from the wheel sensors S1-S4 and gained by means of stages 2 and 3 in the described manner. 
     In the example of an embodiment represented here, the output signals of compass 7 are supplied to the evaluation circuitry via a switch 8. Said switch 8 will only be closed via a signal line, connected to an output A4 of the evaluation circuitry 4, if - in critical situations in which the sensor signals are not unambiguous the information supplied by compass 7 is additionally to be made use of In other examples of embodiments, compass 7 is permanently connected, for instance, in order to detect independently of the signals of wheel sensors S1-S4 whether the vehicle is driving straight onwards or whether it is in the actual process of cornering. The different speeds of the wheels on the inside and on the outside of the bend can directly be taken into consideration when evaluating the signals and braking pressure control such as in calculating the reference velocity of the vehicle. 
     An identification of cornering may also be performed in a known manner by comparing the signals supplied by wheel sensors S1-S4. As long as the wheel slips are approximatively the same a criterion in this process will be the different speeds of the wheels of one axle. In this case, compass 7 can be used for checking or monitoring the sensors. If the information supplied by compass 7 and the sensors S1-S4 is contradictory this will be an indication of an error, therefore a warning signal being triggered via a device not illustrated here and, if necessary, the entire anti-lock control system or traction slip control system being switched off. 
     On the other hand, it is also possible to simplify the evaluation of the signals supplied by wheel sensors S1-S4 or even to reduce the number of wheel sensors and to include the statements of compass 7, or rather of the output signal of this stage, into the signal processing by circuits 4 instead. There are numerous ways possible either to achieve a simplification in evaluation logic or to compare redundant information with other such information, to detect errors and thus to enhance operational reliability of the controller circuitry.