Abstract:
Operation of a vehicle, such as a tractor-trailer, is prevented or modified if operation of the vehicle would be dangerous or destructive due to a brake system abnormality. A motor controller limits the speed of a moving vehicle if a brake system reservoir pressure is below a predetermined threshold or if parking brakes are applied. Additionally, if there is a brake system abnormality, the motor controller limits the motor torque produced in a stationary or slowly moving vehicle. Electronically controlled brake system control modules are recruited to monitor brake system status information and report abnormalities to the motor controller. Preferably, the electronically controlled brake control modules communicate with the motor controller over a serial link.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to the art of vehicle operation monitoring and control. The invention finds application where a driving force of a vehicle can be inappropriately opposed by a braking force of the vehicle. The invention will be described in relation to monitoring and control of a tractor-trailer type vehicle. However the invention is also applicable to other machines. For example, the invention may be beneficially applied in the operation and control of automobiles and electric vehicles as well as other vehicles and machines.  
           [0003]    2. Description of Related Art  
           [0004]    Tractor-trailer vehicles are capable of producing tremendous amounts of torque. Under normal circumstances that torque is beneficially put to use to move and accelerate heavy loads. However, due to operator error or system failure, that torque can also be misapplied. For example, a forgetful operator may attempt to drive the truck while parking brakes of the truck are still applied. Accidentally applying torque against the braking system of the truck can lead to various catastrophic failures. For example, applying engine torque against the mass and locked brakes or the vehicle can result in linking components of the drive train being twisted, stripped, snapped and otherwise torn apart. Alternatively, where the operator is successful in moving the truck against the force of the truck brakes, heat caused by the resulting friction could lead to a foundation brake thermal event.  
           [0005]    Brake system failure can cause the brakes of a truck to be applied without the operator&#39;s knowledge. For example, a brake system failure may allow there to be insufficient air pressure available to disengage spring brakes associated with the truck. In a case such as this, the parking or spring brakes may remain engaged even though the operator takes action to disengage the brakes.  
           [0006]    Insufficient air pressure can be detrimental in another way as well. While air pressure is required to disengage the spring brakes (parking brakes) of a truck, air pressure is required in order to apply the brakes that are normally used to stop the truck. Therefore, if there is insufficient air pressure available in a brake system reservoir, the stopping distance of the truck will not be optimal.  
           [0007]    For the forgoing reasons, a system is needed that limits or prevents the movement of a vehicle when the brakes of the vehicle are applied, or when a brake system of the vehicle is not operating within specified parameters.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    To those ends, a vehicle control system operative to improve safety and prevent damage to a drive train of a vehicle has been developed. The vehicle control system comprises an electronic brake system control module, a plurality of sensors operative to report brake system status information, and a motor control module operative to control the operation of at least a portion of the drive train based, at least in part, on the brake system status information.  
           [0009]    The control system is operative to monitor the status of the brake system. If there is an abnormality in the brake system, the control system limits vehicle drive train output. Under certain circumstances the control system limits vehicle drive train torque output. In other circumstances the control system limits vehicle drive train output in order to limit vehicle speed.  
           [0010]    One advantage to the present invention is found in the ability of the invention to reduce vehicle drive train damage by preventing accidental application of motor torque against wheels that are locked in place.  
           [0011]    Another advantage of the present invention resides in the enhanced safety of a vehicle that cannot be operated if a brake system parameter is out of specification.  
           [0012]    Yet another advantage of the present invention is the prevention of a foundation brake thermal event.  
           [0013]    A further advantage of the present invention is the ability to implement some aspects of the invention without adding substantially to the hardware of prior art vehicles.  
           [0014]    Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred and are not to be construed as limiting the invention.  
         [0016]    [0016]FIG. 1 is a schematic diagram of a truck (tractor) brake system operative to limit drive train output during brake system abnormalities;  
         [0017]    [0017]FIG. 2 is a schematic diagram of a trailer brake system, operative to be connected to and operated through the truck brake system of FIG. 1, the trailer brake system being operative to aid in brakes system monitoring;  
         [0018]    [0018]FIG. 3 is a schematic diagram of a dolly brake system, operative to be connected to and operated through the truck brake system of FIG. 1 directly or through connection to the trailer brake system of FIG. 2, the dolly brake system being operative to aid in brakes system monitoring; and  
         [0019]    [0019]FIG. 4 is a flow chart outlining a method for monitoring a brake system and limiting drive train output during brake system abnormalities. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Referring to FIG. 1, a supervisory system  110  for preventing dangerous and damaging operation of a vehicle includes an electronically controlled brake system module  114 , a plurality of sensors  118  that are operative to report brake system status information and a motor control module  122 . Many prior art vehicles have electronically controlled brake modules. Typically these modules are in communication with brake system sensors. Additionally, electronically controlled brake modules are, at least in some instances, in communication with motor control modules. For example, some control brake system control modules communicate with motor control modules via J1922 or J1939 serial links. Furthermore, electronically controlled brake system modules typically comprise computational devices such as, for example, microprocessors. Therefore, the electronically controlled brake module is a convenient tie point and information processor for the supervisory system. In some embodiments, the supervisory system can be implemented by changing software in the electronically controlled brake system module  114  and in the motor control module  122 . In other embodiments it may be necessary to make hardware changes that change the number or types of sensors  118  that can be connected to the electronically controlled brake system module. The sensors report system parameters that indicate the state of the brakes either directly or indirectly. For example, the plurality of sensors can include a parking or spring brake pressure sensor  126 . If the spring brake pressure sensor  126  reports a high pressure in the spring brake system, the report is a strong indication that spring brakes  130  of the truck are released. However, it is possible that one or more spring brakes  130  are engaged even though there is high pressure in a spring brake system. For example, component failure or corrosion may prevent a spring brake  130  from disengaging. Therefore, the supervisory system may optionally comprise spring brake chamber stroke sensors  134 . A potentiometer or switch may be included in the spring brake  130  assemblies for reporting the position of a spring brake actuator arm  138 . The plurality of sensors  118  may also include service reservoir pressure sensors  142  or switches to monitor compressed air stored in the service reservoir. Normally, as air from the tanks is used to engage and disengage the brakes of the truck, a compressor replenishes the supply of compressed air, thereby preventing the pressure in the reservoirs from falling below a predetermined level. If a failure occurs in the reservoir system, air pressure in the service reservoirs can fall below the predetermined level, thereby preventing the brakes from performing optimally. For example, a leak can develop in the service reservoir system. Alternatively, a failure can occur in the replenishment compressor, thereby preventing air pressure replenishment. Service reservoir pressure sensors  142  or switches report any such drop or loss in pressure to the electronically controlled brake system module  114 . The motor control module  122  receives brake system status information, either from the brake system control module  114  as described here or directly from the brake systems sensors. The motor control module  122  may receive information directly from sensors in implementations without brake system control modules  114 . Either way, communication is preferably through a serial link  146 . Typically the motor control module  122  is an internal combustion engine control module, such as, for example, a diesel engine control module. However, other motor control modules are contemplated. The supervisory system can be implemented with an electric motor control module. If the electronically controlled brake system control module  122  and/or the plurality of sensors  118  report that an abnormality exists in the brake system, the motor control module takes appropriate action to prevent detrimental operation of the vehicle. The motor control module  122 , for example, controls the motor so as to limit the torque produced by the motor. Alternatively, the motor control module  122  controls the motor so as to limit the speed of the vehicle.  
         [0021]    In a tractor-trailer system, it is preferable to also monitor and react to the status of the trailer brake system. Referring to FIG. 2, preferably a trailer brake system  210  also comprises an electronically controlled brake module  214  and a plurality of sensors  218 . Again, the plurality of sensors  218  comprises a spring brake pressure sensor  226  and/or a spring brake chamber stroke sensor  234  and/or a service pressure sensor  242  or switch. The trailer electronically controlled brake control module  214  communicates with the motor control module  122  either directly or through the services of the tractor electronically controlled brake module  214 . Either way, communication is preferably through a serial link  246 .  
         [0022]    Those skilled in the art will understand that the system can be expanded as required. For instance, referring to FIG. 3, a dolly brake system  310  also comprises an electronically controlled brake module  314  and a plurality of sensors  318 . The plurality of sensors  318  comprises a spring brake pressure sensor  326  and/or a spring brake chamber stroke sensor  334 . The dolly brake control module  314  communicates with the motor control module  122  either directly or through the services of the trailer  214  and/or tractor  114  electronically controlled brake modules, again, preferably through a serial link  346 .  
         [0023]    Referring to FIG. 4, in a brake system monitoring step  414  the supervisory system reviews input from the plurality of sensors from the tractor and, if applicable, the trailer and the dolly. If the brake system is operating within normal parameters, vehicle operation continues normally  422  and the supervisory system continues to monitor the brake system  414 . If one or more of the sensors and/or electronically controlled brake control modules reports an abnormality in the brake system, such as an engaged spring brake or a low service reservoir pressure, a vehicle status test step  426  is performed. The vehicle status test  426  reports vehicle movement. Vehicle movement information is provided by, for example, the brake control modules  114 ,  214 ,  314 . It is known in the art that electronically controlled brake control modules are informed about vehicle movement by a plurality of wheel movement sensors  430  (see FIGS. 1, 2 and  3 ). Alternatively the motor control module  122  can determine vehicle movement status from information the motor control module  122  has about motor and transmission speed. If the vehicle is moving or moving above a predetermined speed, the operator is warned, in a first operator-warning step  434 , that the supervisory system is limiting speed and the speed of the vehicle is limited in a vehicle speed-limiting step  438 . An indicator light  442  (see FIG. 1) for instance is actuated to warn the operator of supervisory system action and the operator is prevented from accelerating. Preferably the operator responds by slowing the vehicle and pulling over. With each application of the brakes, the vehicle speed is limited to the speed achieved by the application of the brakes. If the vehicle is not moving, or is moving below the predetermined speed, the operator is warned in second operator warning step  446  that the supervisory system is limiting torque and in a motor torque limiting step  450  the motor control module  122  controls the motor in such a way as to limit the torque delivered by the motor.  
         [0024]    Methods of controlling motors to limit torque are known in the art. Limiting the torque delivered by the motor will limit movement of the truck, although the torque limit is high enough to allow the vehicle to move slowly. With motor torque limited and the vehicle limited to extremely slow movements, the operator must attend to the brake system abnormality.  
         [0025]    The invention has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. The invention is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.