Abstract:
A method of detecting a leak in an air trailer brake circuit of a trailer includes providing a controller, a base valve, a first sensor, a second sensor, a leak control valve having a solenoid, a pneumatic fluid supply, a first brake output, and a second brake output. The method further includes supplying a first pressure to an inlet of the base valve and outputting a second pressure from an outlet of the base valve. The first pressure is detected with the first sensor and the second pressure is detected with the second sensor. The method also includes communicating the detected first pressure and the second pressure to the controller, and comparing a difference between first pressure and the second pressure to a threshold. A leak is detected in the air trailer brake circuit if the difference satisfies the threshold.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure relates to a pneumatic trailer brake control circuit, and in particular, to a pneumatic brake control circuit with breakaway detection. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Tractor trailer combinations generally require a braking system on the trailer that is engaged when a braking system of the tractor is selectively engaged. Often the braking system of the trailer is coupled to the braking system of the tractor to allow the tractor to simultaneously apply the braking system of the tractor and the trailer. Conventional on-road trucks with pneumatic or air service brakes utilize a mechanical breakaway valve since the same operating pressures are used for air service brake and air trailer brake systems. On an agricultural tractor or work machine, however, the service brakes are hydraulic which utilize a much greater operating pressure than a pneumatic or air brake system. 
       SUMMARY 
       [0003]    In one embodiment of the present disclosure, a method of detecting a leak in an air trailer brake circuit of a trailer includes providing a controller, a base valve, a first sensor, a second sensor, a leak control valve having a solenoid, a pneumatic fluid supply, a first brake output, and a second brake output; supplying a first pressure to an inlet of the base valve, where the first pressure is a hydraulic pressure; outputting a second pressure from an outlet of the base valve, where the second pressure is a pneumatic pressure; detecting the first pressure with the first sensor and the second pressure with the second sensor; communicating the detected first pressure and the second pressure to the controller; comparing a difference between first pressure and the second pressure to a threshold; and detecting a leak in the air trailer brake circuit if the difference satisfies the threshold. 
         [0004]    In one example of this embodiment, the method may include energizing the solenoid of the leak detect valve via the controller if the difference satisfies the threshold. In a second example, the method may include actuating the leak detect valve to a closed position if the difference satisfies the threshold. In a third example, the method may include supplying pressurized fluid from the pneumatic fluid supply to the leak control valve. In a fourth example, the method may include supplying a third pressure to a second inlet of the base valve from the pneumatic fluid supply, where the third pressure is a pneumatic pressure. In a fifth example, the method may include determining the difference by first multiplying the first pressure by a ratio, and then subtracting the second pressure therefrom. 
         [0005]    In a sixth example of the embodiment, the method may include de-energizing the solenoid if the difference does not satisfy the threshold. Moreover, the method may include fluidly coupling the pneumatic fluid supply to the first and second brake outlet if the leak detect valve is de-energized. In another example, the method may include blocking pneumatic fluid from the first and second brake outlets when the difference satisfies the threshold. In yet another example, the method may include releasing a park brake of the trailer if the difference satisfies the threshold. In a further example, the method may include disengaging the park brake of the trailer if the difference does not satisfy the threshold. 
         [0006]    In yet a further example, the method may include fluidly coupling the leak detect valve and the base valve in series when the difference does not satisfy the threshold. The method may also include fluidly coupling the pneumatic fluid supply to the first brake output via the leak detect valve; and fluidly coupling the pneumatic fluid supply to the second brake output via the leak detect valve and the base valve. Moreover, the method may include stopping the detected leak between the base valve and the second brake output by energizing the solenoid of the leak detect valve. 
         [0007]    In another example of this disclosure, a braking system of a trailer includes a pressurized supply of pneumatic fluid and hydraulic fluid; a base valve including an inlet and an outlet, where the inlet is fluidly coupled to the pressurized supply of hydraulic fluid; a solenoid control valve including an inlet fluidly coupled to the pressurized supply of pneumatic fluid, the solenoid control valve operably controlled between an energized state and a de-energized state; a brake output fluidly coupled to the outlet of the base valve; a first sensor and a second sensor fluidly coupled to the base valve, the first sensor configured to detect a first pressure at the inlet of the base valve, and the second sensor configured to detect a second pressure at the outlet of the base valve; wherein, the solenoid valve is operably controlled to its energized state when a difference between the first pressure and second pressure satisfies a threshold. 
         [0008]    In one example of this embodiment, in the de-energized state the pressurized supply is fluidly coupled to the base valve and the brake output, and in the energized state the solenoid control valve fluidly de-couples the pressurized supply from the base valve and the brake output. In a second example, the system may include a second brake output fluidly coupled to the solenoid control valve in the de-energized state. In a third example, the system may include a park brake pneumatically controlled by the second brake output between a disengaged position and an engaged position, wherein in the de-energized state the park brake is in its disengaged position, and in the energized state the park brake is in its engaged position. 
         [0009]    In another example of this embodiment, the system may include a controller disposed in electrical communication with the first sensor, the second sensor, and the solenoid, the controller storing the threshold and a ratio, where the ratio is a function of the base valve; wherein, the controller determines the difference by multiplying the first pressure by the ratio and then subtracting the second pressure therefrom; wherein, the controller compares the difference to the threshold, and sends an electrical signal to the solenoid to control the solenoid valve between its energized and de-energized states. 
         [0010]    In a further embodiment of this disclosure, a pneumatic braking system of a trailer towed by a work machine includes a pressurized supply providing pneumatic fluid; a pilot line providing hydraulic fluid; a base valve including a first inlet, a second inlet, and an outlet, where the first inlet is fluidly coupled to the pilot line; a solenoid control valve including an inlet and an outlet, the inlet of the solenoid control valve fluidly coupled to the pressurized fluid supply, and the outlet being coupled to the second inlet of the base valve; a first control line fluidly coupled to the outlet of the base valve; a second control line fluidly coupled to the outlet of the solenoid control valve; wherein, the solenoid control valve is operably controlled between an energized state and a de-energized state; wherein, in the de-energized state the pressurized supply is fluidly coupled to the second inlet of the base valve and the second control line, and in the energized state the solenoid control valve fluidly de-couples the pressurized supply from the second inlet of the base valve and the second control line. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a side view of a combined tractor and trailer system; 
           [0013]      FIG. 2  is a control schematic view of a hydraulic system of a combined tractor and trailer brake system; 
           [0014]      FIG. 3  is a control schematic view of a combined hydraulic and pneumatic system of a combined tractor and trailer brake system; 
           [0015]      FIG. 4  is a pneumatic control circuit of a combined tractor and trailer brake system; and 
           [0016]      FIG. 5  is a flow diagram of a control process for controlling a combined tractor and trailer brake system. 
       
    
    
       [0017]    Corresponding reference numerals are used to indicate corresponding parts throughout the several views. 
       DETAILED DESCRIPTION 
       [0018]    The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure. 
         [0019]    Referring to  FIG. 1 , a combined tractor trailer system  100  is shown. In this system, a tractor  102  is shown coupled to and pulling a trailer  104 . The tractor  102  may have a chassis  106  that spans between a front ground engaging mechanisms  108  and a rear ground engaging mechanisms  110 . In the embodiment of  FIG. 1 , each ground-engaging mechanism is in the form of a wheel defined along a respective axle, i.e., a front axle and a rear axle. In other embodiments, however, the ground-engaging mechanism may be a track that propels the tractor  102  along a ground surface. Likewise, the trailer  104  may also include at least one ground-engaging mechanism such as a wheel  126 . 
         [0020]    A cab  112  may be coupled to the chassis  106  and define a location for an operator to be positioned in an operator&#39;s seat  114 . From the cab, the operator may control the tractor  102  and trailer  104  via a plurality of controls. As shown, the cab  112  may include a display  116  or dashboard that visually shows control characteristics of the tractor  102  or trailer  104  such as speed, power, temperature, pressure, direction, and any other type of control characteristic. The display  116  may be a touchscreen display that includes one or more operator controls for selectively controlling the operation of the tractor  102  or trailer  104 . Other controls may include a steering wheel or yoke  118 , a pedal  120  (e.g., a brake pedal, clutch pedal, or throttle pedal), any other type of control such as a joystick, switch, lever, knob, etc. for controlling the tractor trailer system  100 . 
         [0021]    While a tractor  102  is shown and described herein, any type of work machine may utilize the teachings of this disclosure and therefore it is not intended to be limited to applying to only tractors. In other embodiments, a truck configured to tow a trailer may utilize the teachings of this disclosure. Accordingly, the tractor  102  can be any type of work machine used to pull a trailer. 
         [0022]    The tractor  102  may be coupled to the trailer  104  through a hitch member or drawbar  116 . The hitch member or drawbar  116  may be sufficiently strong to transfer motion of the tractor  102  to the trailer  104 . In one embodiment, when the tractor  102  travels in a forward direction, the hitch member  116  pulls the trailer  104  along therewith in approximately the same direction. 
         [0023]    One or more fluid lines  118  may also be provided. For purposes of this disclosure, a fluid may include a gas or liquid. Thus, any pneumatic or hydraulic line may be referred to as a fluid line herein. The one or more fluid lines  118  may selectively fluidly couple a tractor brake system to a trailer brake system. More specifically, the tractor  102  may provide a trailer brake output that is coupled to the trailer brake system. In this configuration, when the user initiates a brake command, both the tractor brake system and the trailer brake system may simultaneously engage to slow the tractor  102  and trailer  104 . 
         [0024]    In some tractor trailer systems, one or more brake pedals may be engaged by an operator to apply a tractor service brake. Brake actuators may be pressurized to apply the brakes, which will be described in greater detail below with reference to  FIG. 2 . Once the operator commands engagement of the tractor braking system, the trailer braking system also must engage to prevent the trailer from contacting or running into a back end of the tractor. In many conventional braking systems, there may be a single hydraulic line that connects between the tractor and trailer braking systems. In addition, a single hydraulic trailer brake valve may have a fixed gain associated with it due to its geometry. Thus, depending upon the fixed gain, an amount of pressure entering the valve if multiplied by the fixed gain to deliver a predetermined outlet pressure. As braking systems change and new federal and international guidelines or standards change, there is a need for both lower and higher outlet pressures depending upon the type of trailer. As a result, an adjustable gain across the hydraulic trailer brake valve is desirable over a fixed gain valve. Other needs and advantages will become apparent from the principles and teachings of the present disclosure. 
         [0025]    In some tractor trailer systems, the trailer braking system includes a hydraulic braking system, a pneumatic braking system, or a combination thereof. An example of a trailer brake system is shown in  FIG. 2 . In this embodiment, a hydraulic braking system  200  of a tractor and a trailer may include a brake controller  202  as shown. The brake controller  202  may be in electrical communication with a vehicle controller (not shown), an engine controller (not shown), a transmission controller (not shown), and any other type of controller for controlling the tractor or trailer. The brake controller  202  may include a plurality of inputs and outputs for receiving and communicating electrical signals or commands to different components within the braking system  200 . In  FIG. 2 , for example, the brake controller  202  may be disposed in electrical communication with a tractor display  250 . This communication may exist over a controller area network (CAN) bus  252  or communication link. The display  250  may allow an operator to selectively communicate instructions to the brake controller  202  for controlling the tractor braking system or the trailer braking system  200 . 
         [0026]    Other operator controls may also be in communication with the brake controller  202 . For example, one or more brake pedals  204  may be selectively engaged by an operator. A brake position sensor  206  may detect a movement of the one or more brake pedals  204  and communicate this movement to the brake controller  202 . Upon application of the one or more brake pedals  204 , a brake valve  212  may be triggered such that fluid from a hydraulic supply line  254  (via a pump or other pressure source) is delivered to brake actuators. In turn, the brake actuators are controllably actuated to deliver hydraulic brake pressure to the tractor braking system to control the speed of the tractor. In  FIG. 2 , the braking system  200  illustrates a right brake actuator  208  and a left brake actuator  210 . In this embodiment therefore the operator may depress a right brake pedal and a left brake pedal to engage the tractor braking system. The right brake pedal and right brake actuator  208  may control brake pressure to a service brake on the right, rear wheel of the tractor, and the left brake pedal and left brake actuator may control brake pressure to a service brake on the left, rear wheel of the tractor. In doing so, the right brake actuator  208  and left brake actuator  210  deliver hydraulic pressure to the tractor service brakes to slow the vehicle. This hydraulic pressure may also be delivered to the trailer braking system as will be described below. 
         [0027]    As is known, an operator may apply the brake pedals to brake the tractor and slow its speed. In addition, an operator may gently apply or tap on the brake pedal, as is often the case with an operator desiring to disable cruise control in a motor vehicle. In the tractor trailer system, it may be desirable to begin braking the trailer as soon as the brake controller  202  detects engagement of the one or more brake pedals  204 . In this example, the brake controller  202  may execute a pre-brake routine or algorithm to begin applying the trailer braking system. In the embodiment of  FIG. 2 , the brake pedal position sensor  206  can send a signal to the brake controller  202  indicating that the operator has begun to depress the pedals  204 . Before any brake pressure or a substantial amount of brake pressure is generated, the brake controller  202  may execute the pre-brake routine and send a signal to the trailer braking system to begin braking the trailer. This signal may be an adjustable or proportional signal from the brake controller  202 . The signal may be received by a trailer brake valve that includes a first solenoid valve and a second 2-way position valve (i.e., an on/off valve). In one example, up to seven bars of pressure may be output from the valve to the trailer brakes to begin a braking operation. 
         [0028]    During this pre-brake routine, the first solenoid valve may receive the signal from the brake controller and deliver the hydraulic pressure to the trailer brakes. The second, 2-way position valve may be disposed in its open position to allow fluid pressure to pass through. However, if there is a failure detected in the system, the second, 2-way position valve can be actuated to its off or closed position to block fluid pressure to the trailer brake system. This “fail-silent” condition may be utilized to protect against possible failures in the system. In any event, hydraulic pressure may still pass through a main hydraulic trailer brake valve  226  ( FIG. 2 ) so that the trailer braking system is engaged during a braking operation. The pre-brake valve set, however, may be disabled or closed so that no output pressure passes through the valve set to the trailer brakes. 
         [0029]    In  FIG. 2 , hydraulic brake pressure from the right brake actuator  208  may be detected by a first pressure transducer  214 , and from the left brake actuator  210  may be detected by a second pressure transducer  216 . The first and second transducers may be in electrical communication with the brake controller  202 . This electrical communication may be either wired or wireless communication, or any other known or to be developed form of communication. As a result, the brake controller  202  can monitor brake pressure from both actuators. 
         [0030]    A shuttle valve  218  may be disposed in fluid communication with the right brake actuator  208  and the left brake actuator  210 . The shuttle valve  218  may be actuated in either direction depending upon which brake pressure is the greatest. As such, the greater of the two brake pressures passes through the shuttle valve  218  and is referred to as brake pilot pressure. In  FIG. 2 , the brake pilot pressure flows downstream from the shuttle valve  218  along a brake pilot line  242 . 
         [0031]    The braking system  200  of  FIG. 2  may also include a hydraulic valve set  220 . This valve set  220  may be similar to the aforementioned pre-brake valve set in that it includes both a proportional solenoid valve and a 2-way shutoff valve. As shown, the brake controller  202  may be in electrical communication with the hydraulic valve set  220  to control its operation. For example, a trailer brake command  248  may be communicated from the brake controller  202  to the valve set  220 . Moreover, the valve set  220  may send signals to the brake controller  202  in response to its operation (i.e., a pressure transducer  224  may communicate a pressure associated with the valve set to the controller  202 ). 
         [0032]    Outlet pressure from the hydraulic valve set  220  may flow through a fluid line  244  as shown in  FIG. 2 . The hydraulic valve set fluid line  244  and the brake pilot line  242  may converge upon a second shuttle valve  222 . Similar to the operation of the first shuttle valve  218 , the greater of the brake pilot pressure and hydraulic valve set pressure may pass through the second shuttle valve  222  and enter hydraulic line  246 . The pressure in hydraulic line  246  may be referred to as the hydraulic pilot pressure. A pressure transducer  228  can detect the hydraulic pilot pressure and communicate this pressure to the brake controller  202 , as shown in  FIG. 2 . This hydraulic pilot pressure may pass through a hydraulic trailer brake control line  230  to the trailer brakes. 
         [0033]    In the system  200  of  FIG. 2 , the trailer may also include a trailer park brake. The trailer park brake may be operably controlled via a hydraulic trailer park control valve  232 . This valve  232  may include a solenoid  234  that is in electrical communication with the brake controller  202 . The hydraulic trailer park control valve  232  may be biased to its vented position to allow pressure to flow through a supplementary hydraulic line  240 . The valve  232  may also be in fluid communication with a tank or reservoir  236  as shown. As such, hydraulic pressure may be delivered from a supply line  238  to the hydraulic trailer park control valve  232 , and in its normally or biased open position, pressure passes therethrough to the hydraulic trailer brake supplementary line  240 . 
         [0034]    Referring to  FIG. 3 , a portion of the braking system  200  of  FIG. 2  is removed and an air or pneumatic trailer braking system  300  is shown. As described above, the trailer braking system may be hydraulic, pneumatic, or a combination thereof. In this disclosure, the pneumatic trailer braking system may use any form of gas for controlling its brakes. However, for sake of simplicity, the type of gas will be referred to as air through the remainder of this disclosure. Thus, the pneumatic trailer braking system  300  will be referred to as the air trailer braking system  300 , but it is to be understood that any type of gas may be used to control the trailer brakes. 
         [0035]    In  FIG. 3 , the air trailer braking system  300  may include an air or pneumatic trail brake valve  302 . The air trailer brake valve  302  may be located downstream from the second shuttle valve  222  of the hydraulic system  200  such that hydraulic pressure is used as an inlet to control the valve  302 . Hydraulic pressure may flow through a pilot pressure line  312  to an inlet of the air trailer brake valve  302 . 
         [0036]    In addition to the air trailer brake valve  302 , the air trailer braking system  300  may also include an air supply line  320 , a shuttle valve  304 , an air trailer park brake control valve (not shown), and a leak detect valve  306 . The shuttle valve  304  is disposed downstream of the air trailer brake valve  302  and the air trailer park brake control valve. Thus, air pressure may be output from the air trailer brake valve  302  via a first pressure line  314  and from the air trailer park brake control valve via a second pressure line  316 . The greater of the two pressures from the first and second line may trigger the shuttle valve  304  open so that air pressure can flow through a first air trailer brake control line  318  to the air trailer brakes. A pressure transducer  310  may be in fluid communication with the control line  318  to detect the pressure and communicate it to the brake controller  202 . 
         [0037]    The leak detect valve  306  may be in the form of a normally open solenoid control valve. The valve  306  may include a solenoid  308  that is disposed in electrical communication with the brake controller  202 . As such, the brake controller  202  can control the leak detect valve  306  between its open and closed positions via a communication link  324  with the solenoid  308 . 
         [0038]    Air pressure may be supplied via the supply line  320  to the leak detect valve  306 . Since the leak detect valve  306  may be biased to its open position, fluid may flow through the valve  306  to the air trailer brake valve  302  and to an air trailer brake supply line  322 . 
         [0039]    The embodiments of  FIGS. 2 and 3  are illustrative of only one example of a braking system for a tractor trailer combination. Other embodiments of a braking system is possible and within the scope of this disclosure. For instance, another embodiment may include one or more electrohydraulic secondary brake valves. 
         [0040]    Referring to  FIG. 4 , an air trailer brake control system or circuit  400  is shown. As previously described, many non-agricultural trucks and machines utilize a mechanical breakaway valve as a breakaway detection feature. This is possible since these vehicles include a similar or same operating pressure for the air service brake and air trailer brake systems. With an agricultural machine such as a tractor, however, the work machine includes service brakes which are hydraulic. Hydraulic service brakes often require a much higher operating pressure than an air system, and the high pressure hydraulic brake system can make it difficult to utilize a mechanical breakaway valve solution. Thus, a system such as the one illustrated in  FIG. 4  is necessary and utilizes an electro-pneumatic valve for breakaway control on agricultural work machines. 
         [0041]    The control system  400  may include the air trailer brake valve  302  and the leak detect valve  306  as described above with reference to  FIG. 3 . Here, the leak detect valve  306  may be an electro-pneumatic valve that is disposed in series with the air trailer brake valve  302 . The leak detect valve  306  may function as an on/off valve, where the valve is actuated between an energized or de-energized position. As shown, the valve  306  includes a solenoid  308  that is in electrical communication with the brake controller  202 . Thus, the brake controller  202  can control the leak detect valve  306  between its energized and de-energized positions. 
         [0042]    An air supply  402  is provided in fluid communication with an inlet side of the leak detect valve  306 . Air may be supplied via an air supply line  320  as shown in  FIG. 3 . During normal operation, the leak detect valve  306  may be de-energized and air flow is possible from the supply  402  to the second control line  322  and the air trailer brake valve  302 . In this position, a spring  404  may bias the leak detect valve  306  to an open position to allow the air supply  402  to be fluidly coupled with the second control line  322  and air trailer brake valve  302 . The second control line  322  may be fluidly coupled to a park brake of the trailer such that when air flows through the second control line  322 , the park brake is held or disposed in its disengaged position. When there is no air flow through the second control line  322 , the park brake may be released to slow or stop the machine. 
         [0043]    The brake controller  202  is configured to detect if there is a leak or a break in the first control line  318  of  FIG. 3 . When a leak is detected, the controller  202  may send a signal (e.g., a current) to the solenoid  308  to energize the leak detect valve  306 . Once energized, the leak control valve  306  may actuate to a closed position to block air flow from the supply  402  to the second control line  322  and the air trailer brake valve  302 . With no air flow provided to the second control line  322 , the park brake (not shown) may be released to slow the trailer. Moreover, without air flow, the air trailer brake valve  302  may not provide any flow to the first control line  318 . The air trailer brake valve  302  may include a spring  406  that biases it to a position. Air or hydraulic fluid may vent  408  to tank  236  or another location. 
         [0044]    Referring to  FIG. 5 , a control process  500  is provided for controlling the system  400  of  FIG. 4  when a leak is detected. The process  500  may include one or more blocks or steps which are executed during the process  500 . In a first block  502 , for example, the air supply  402  provides pressurized air to an inlet side of the leak detect valve  306 . This block may be executed regardless of whether a leak is detected. When there is no leak, block  504  is executed and the leak detect valve  306  is de-energized. In this condition, the spring  404  biases the valve open so that air is able to flow therethrough. When air is able to flow through the leak detect valve  306 , blocks  506  and  508  are executable such that the air supply  402  is fluidly coupled to the second control line  322  and the air trailer brake valve  302 . In particular, the air supply  402  is able to provide pressurized air to an air inlet side of the air trailer brake valve  302 . Moreover, as air flows through the second control line  322 , the park brake (not shown) of the trailer is biased or held in its disengaged position. 
         [0045]    Since the service brakes on an agricultural work machine are hydraulic, block  510  is executable such that hydraulic pressure may be provided via the pilot pressure line  312  to a hydraulic inlet side of the air trailer brake valve  302 . Pilot pressure may be detected by a pressure sensor or transducer  410  at a location along the pilot pressure line  312 . Moreover, in block  512 , the outlet air pressure from the air trailer brake valve  302  may also be detected by a second pressure sensor or transducer  310 . The pressures on both sides of the air trailer brake valve  302  may therefore be used to detect a possible leak in the first control line  318 . 
         [0046]    In order to detect a leak, the pilot pressure and outlet pressure may be communicated to the brake controller  202  via the respective sensor. In block  514 , the brake controller  202  may determine or receive an air trailer brake ratio that exists across the valve  302 . This ratio may be associated with an output gain across the valve. This may be a fixed ratio that is predefined and stored in a memory unit of the controller  202 . Alternatively, the ratio may be determined by a calculation made by the controller  202 . In any event, the brake controller  202  determines the air trailer brake ratio and multiplies it by the pilot pressure detected by the first pressure sensor  410 . The result of this calculation is then compared to the output pressure detected by the second pressure sensor  310 . From this calculation, a difference is determined in block  514 , and it is compared to a broken line threshold value in block  516 . The broken line threshold value may be stored in the controller  202 , i.e., in its memory unit. If the difference exceeds the threshold value in block  516 , then the controller  202  may make a determination that a leak exists in the first control line  318 . 
         [0047]    If, in block  516 , the brake controller  202  determines that a leak exists in the second control line  318 , then the process  500  may advance to block  518  where the controller  202  sends a signal to the solenoid  308  to energize the leak detect valve  306 . This signal or command may be a current, for example. By energizing the leak detect valve  306  in block  518 , the leak detect valve  306  may actuate to its closed position to block air flow to the second control line  322 . As air flow is blocked by the leak detect valve  306 , the park brake (not shown) may be released in block  520  to slow or stop the trailer. Moreover, air flow is blocked from the air trailer brake valve  302 , and the air leak in the first control line  318  is stopped. 
         [0048]    The control process  500  of  FIG. 5  may be executed continuously. However, leak detection is only executed when there is pilot pressure provided to the air trailer brake valve  302 . Otherwise, the control system  400  is not actively trying to brake the trailer. 
         [0049]    While this disclosure has been described with respect to at least one embodiment, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.