Abstract:
A system for determining the rotational direction of a ready mix concrete truck drum can be used to accurately determine the time interval between when a batch of concrete is loaded into a ready mix truck and when it is discharged. This time interval is critical to the overall quality of the concrete. The present invention comprises a camera, a computing platform, and software that runs on the computing platform that can interpret the visual data captured by the camera and determine the rotational direction of the ready mix drum. This rotational direction data can then be used to determine the time interval from when the concrete is loaded on the truck and when the concrete is discharged. This time interval directly relates to the quality of the concrete.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 62/175,764 filed Jun. 15, 2015 entitled “Drum Rotation Detection System,” and is incorporated by reference herein for all purposes. 
     
    
     FIELD 
       [0002]    The invention disclosed herein is a system and method for determining the direction of drum rotation for ready mix concrete delivery trucks and the timing of the discharge of concrete from ready mix concrete delivery trucks. 
       BACKGROUND AND SUMMARY 
       [0003]    Ready mix delivery trucks (concrete delivery trucks) are the work horses in the ready mix industry delivering concrete from the batch plants, where the mix to make concrete is loaded on to the truck, to the construction site. Once at the construction site, the concrete may be pumped through an external pumping system or may be simply discharged (off loaded) directly to the location that needs the concrete. 
         [0004]    In order to guarantee the quality and structural strength of a building, the concrete that is delivered must adhere to rigorous standards. The quality of the concrete is correlated to the amount of time the concrete has been inside the drum and the amount of water that has been added to ensure that the concrete is easy to pour. In order to ensure that customers receive the concrete in adherence with the standards required for a particular job, ready mix companies locate their batch plants strategically in order to reach the construction sites within the shortest possible time. External factors also contribute to the quality of the ready mix. Conditions such as roadway congestion, heat, and the weather conditions in general can impact the quality of ready mix concrete. 
         [0005]    As one can see from the above description, the concrete is extremely susceptible to external factors that have a direct bearing to the quality of the concrete. The quality of the concrete has a direct bearing on the structural strength of the building. A building that has been built with compromised material can crack and collapse, threatening the lives of people and destroying any important items housed within the building. 
         [0006]    The quality of the concrete is a key component when building a building. The quality of the concrete relates to the time interval between when the concrete mix is loaded onto the ready mix truck and when the concrete is delivered to the construction site. If the concrete has been sitting in the ready mix truck for too long, it may exceed the standards, and the customer will reject the load. 
         [0007]    Most ready mix trucks contain a set of blades or fins in the interior of the mixing drum. When the drum is rotated one direction, the truck may be loaded and the concrete mixed. When the drum is rotated the other direction, the mixed concreted is discharged or unloaded. The ready mix companies keep records of when the ready mix concrete is discharged at a particular location. To prevent any future lawsuits due to substandard ready mix, the ready mix companies use several methods to record the time of discharge. This information can be used, along with the time the concrete was loaded onto the ready mix truck, to determine how long the ready mix has been in a ready mix truck drum. This time period is a factor in determining if the ready mix complies with the governing standards. 
         [0008]    The most basic and error prone technique used to address this issue is to have the ready mix driver record the time of discharge manually. The customer may additionally assign a person to sign off on the time of discharge, thus providing a validated mechanism to record the discharge event. These records, which rely 100% on human input, are considered quite error prone. 
         [0009]    Several ready mix truck manufacturers have developed their own proprietary drum rotation sensor solutions, such as the solution disclosed in U.S. Pat. No. 7,722,243 B2 by Schumacher et al. This solution relies on the hydraulics of the drum rotation drive to determine the direction of rotation. Although this is an accurate solution, it is only applicable when the ready mix truck is manufactured by a particular company. There are many other ready mix truck manufacturers; hence the solution is not universally applicable. 
         [0010]    With proprietary solutions, a ready mix truck operator will face a daunting task to keep the fleet well maintained because different manufacturers will each provide their own solutions. Furthermore, proprietary solutions also mandate that the ready mix fleet operator must purchase that particular truck manufacturer&#39;s solution. What happens to a truck before that particular truck is purchased is another unanswered question which may impact the availability of some drum rotation detection solutions. Due to these basic issues, proprietary solutions are often not applicable across an entire fleet of ready mix trucks. 
         [0011]    An alternative prior art solution involves placing magnets on the drum. This system also requires a sensor that has been developed by Trimble Corporation and is covered under several patents (e.g., U.S. Pat. No. 6,611,755). The sensor detects the movement of the magnets, which informs the speed and direction of drum rotation. While this is the most common solution currently in use, it is not ideal considering the standard practices of the ready mix industry. 
         [0012]    In the Trimble solution, the magnets are bolted to the drum. These magnets are then exposed to acids that are used to clean the drums when concrete splashes onto the drum. The exposure to acid over a period of time destroys the magnets. The ready mix company has to replace the magnets that have malfunctioned, and this will impact the productivity of the ready mix truck. 
         [0013]    Furthermore, the sensor that detects the magnets gets exposed to acid as well. The sensor degrades over a period of time and eventually must be replaced by the ready mix company. Both the ready mix truck and the drum itself vibrate due to the motion of the drum. The drum and the chassis vibration often cause the sensor to become misaligned. When the sensor is not in proper alignment, the rotation of the drum is not detected. 
         [0014]    The average ready mix truck operator estimates that the sensor must be adjusted, repaired, or replaced at least three times per year. This repair requires the truck to be out of service and reduces the productivity of the truck for that period of time. 
         [0015]    The Trimble solution involving magnets and sensors is a potentially universal solution, but the problems associated with cleaning acid and harsh chemicals makes that solution very expensive to maintain. The precision required to align the sensor or to rerun the cables from the drum sensor to the control box consumes significant time and cost. 
         [0016]    A ready mix truck may work for 12-15 hours per day or more. When a sensor malfunctions, the loss of a truck for a few hours can cause significant financial harm to the operator. 
         [0017]    An aspect of the invention is to provide a solution for determining the direction of rotation of a ready mix truck drum that is protected from the harsh conditions and chemicals associated with ready mix trucks. 
         [0018]    Another aspect of the invention is to determine the time interval between the loading and discharge of a ready mix truck drum. 
         [0019]    An additional aspect of the invention is to provide a solution for ready mix truck operators to determine if concrete complies with the governing regulations. 
         [0020]    A system and method of determining the direction of rotation of a ready mix truck drum is disclosed. The system described herein comprises a camera, a computing platform optimized for image processing, and software that runs on the computing platform to process the images and compare the position of the drum in one image against the previous image to determine the direction of rotation of the drum. 
         [0021]    The present invention addresses the most common issues faced by the ready mix delivery truck operators, determining the direction of rotation in a way that is both reliable and easy to maintain. The present invention operates with little or no exposure to the harsh environmental conditions and chemicals associated with ready mix delivery trucks. The invention is mounted inside the interior of a ready mix truck&#39;s cabin on the rear window of the ready mix truck. This position provides the camera with a clear view of the drum without exposing any of the components to the exterior conditions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a block diagram showing the components of the visual direction detection system  100  and how the system  100  can be attached to the back window  350  of a vehicle. 
           [0023]      FIG. 2  is a flow diagram of a technique provided by the system  100  for determining the direction and speed of rotation of a ready mix truck drum  400 . 
           [0024]      FIG. 3  is a depiction of the various potential visible marks that may be man-made  440  or occur due to natural wear and tear  420  on a ready mix truck drum  400 . 
           [0025]      FIG. 4  shows multiple examples of where the camera unit  200  can be mounted on the rear window  350  of the ready mix truck cabin. 
           [0026]      FIGS. 5A-5C  show a series of images of a ready mix truck drum  400  with visible man-made markings  440 , visible wear and tear  420 , and weld marks  410  as the drum  400  rotates. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  is a block diagram of the components that make up a visual direction detection system  100  in a single-module embodiment. In other embodiments of the visual rotation direction detection system  100 , the components may be separated from each other and packaged into multiple discrete modules. These modules may be connected by either wired or wireless communication techniques and placed in a preferred position based on the customer&#39;s needs and the arrangement of a particular ready mix truck. 
         [0028]    The visual direction detection system  100  is mounted as illustrated in  FIG. 1 . The camera  200  is facing the window glass  350  at the rear of the truck cabin. A durable double sided tape or a special mount or mounting bracket may be used to secure the visual direction detection system  100  to the glass  350 . Prior to mounting the system  100 , the camera  200  must be properly focused to ensure the camera  200  obtains a clear image of the ready mix truck drum  400 . Sealing the visual direction detection system  100  to the window glass  350  with double sided tape or another suitable sealant minimizes the chances of dust getting in to the camera  200 . Certain embodiments may also comprise a housing around the camera or around the entire system designed to prevent contamination of the electronics by dust, concrete, and/or humidity. In certain embodiments, the housing my connect to the ready mix truck&#39;s air conditioning and/or heating system in order to maintain appropriate operating temperatures of the electronic components involved. 
         [0029]      FIG. 2  is a flow diagram showing the steps  105 - 125  performed by a preferred embodiment of the system  100  to determine the speed and direction of rotation of the drum  400 . In a first step  105 , the camera  200  captures a video stream, a series of images, and/or a limited set of still images of the ready mix truck drum  400 . In the next step  110 , the images acquired by the camera  200  are inspected by a computing platform  220  that is optimized for image processing. The system  100  then identifies recognizable patterns within the captured images and records the location of these patterns in step  115 . In some embodiments the edge points of a pattern may be identified and used to determine the location of the pattern. This process is repeated for multiple images over a known period of time. The system  100  then proceeds to analyze the location of an identified pattern across a series of captured images in step  120 . In a final step  125 , the change in the location of a particular recognized pattern across a series of images representing a known time interval is used to determine the speed and direction of rotation of the ready mix truck drum  400 . 
         [0030]    The required frame rate of the camera  200  depends on the speed of the rotating drum  400  and the detectable patterns on the drum  400 . Acquiring a greater number of frames will help determine the direction of rotation faster and more accurately. It may be necessary to store the images on board the unit in certain customer configurations. To fulfill this goal, the visual direction detection system  100  can be equipped with an on board data storage component  230 . Along with images and video, a vast array of other data points can be captured and associated with the direction and/or speed of rotation. Data points such as GPS location of the truck, time and/or date stamp, speed of the truck, operator ID, weather conditions, elapsed time since the truck was loaded and many more may be recorded. By correlating these data points with the direction of rotation of the drum, a more thorough understanding of the treatment and conditions associated with unloading ready mix concrete can be developed. 
         [0031]    To improve precision and detect the direction of rotation faster, certain embodiments of the invention may contain an on board global positioning system (“GPS”) module  240 . In instances when the drum  400  is brand new or when the truck is operating in near darkness, the GPS module  240  will help improve accuracy of the detection. The GPS module may be used to determine the location and/or speed of the truck. The algorithm may be configured to know that the truck will not unload concrete when the truck is traveling at above a predetermined speed. Certain embodiments may also be configured to know where the planned unloading site of the truck is. In some embodiments, the algorithm may be configured to understand it is more likely that the truck will be unloading when it is at or near its predetermined unloading location and less likely to unload at more remote locations. 
         [0032]    Once the visual direction detection system  100  is mounted on the rear window  350 , there may be a need to periodically calibrate the camera or upgrade the software and firmware. If this activity is done manually, it may be advantageous to have a physical interface. In some embodiments, an optional Universal Serial Bus (USB) port  250  may be added to the system  100 . 
         [0033]    When the drum rotation direction changes from charging to discharging (unloading the concrete), it is often desirable to notify the dispatch center. Depending on the embodiment of the invention used, the rotation direction data can be sent over a cellular data connection or a Wi-Fi connection. This transmission is achieved through the communication interface  260 . 
         [0034]      FIG. 3  illustrates a view from the rear window glass  350  in the cabin of a ready mix truck. The driver must be able to see the drum  400  for safety reasons, therefore clear glass  350  is used in ready mix trucks. Depending on the type of truck, there are typically some components that are fixed in position and create a visible obstruction  500  through the rear window of the ready mix truck cabin. The visual rotation direction detection system  100  must be positioned so that any visible obstruction  500  does not prevent the camera  200  from having a clear view of the drum  400 . The system  100  works best when the weld marks  410  are clearly visible on the drum  400 . The drum  400  almost always has some weld marks  410 , which are necessary to manufacturing the drum  400 . 
         [0035]    The visual direction detection system  100  operates in a manner that is unique, because it does not need any equipment placed on the drum  400 . The system  100  does not require any man-made markings  440  placed on the drum  400  either; however, any visible marks placed on the drum  400 , such as stickers, logos and/or reflectors  440 , can greatly assist the detection process as discussed below. 
         [0036]    The illustration in  FIG. 3  shows a drum  400  that is considered in excellent condition for the visual direction detection system  100 . Due to the chemicals used and exposure to the environment, the steel drums  400  often start to rust leaving visible wear-and-tear marks  420  on the surface of the drum  400 . Initially, there is typically discoloration and paint peeling off of the drum  400 . Shortly after the paint peels off of the drum  400 , rust starts to appear. These visible marks  420  can be clearly seen by the camera  200  and used by the system  100  to determine the direction of rotation. By comparing one still image captured by the camera  200  to the next, the system  100  will compare the movement of detectable visual marks  420  over a period of several images. The visible marks  420  are then normalized by the system  100  to determine a general direction of rotation. This technique may also be applicable to video streams but is most useful when applied to a series of still images. 
         [0037]    The drum  400  is set at an angle on the chassis of the truck. The drum  400  is frequently elliptical rather than circular but the disclosed invention will operate regardless of the exact drum shape. Due to these frequently elliptical drum conditions, some of the points tracked by the system  100  will not move directly in the charging or discharging direction. The system  100  compensates for these angles and normalizes the direction of rotation to determine if the drum  400  is rotating in the charging or discharging direction. The major direction of movement of these points over a certain time period or number of image frames will increase the confidence threshold of the system. 
         [0038]    In a new drum  400  that has fewer visual marks  420  due to wear-and-tear, the visual direction detection system  100  will detect the pattern of points on the weld marks  410 . Weld marks  410  are not smooth and typically consist of many low and high relief features, which will constitute points of interest to the system  100 . The direction of movement of these points is normalized by the system  100  and used to determine the direction of drum rotation. 
         [0039]    By using the on board GPS  240 , the system  100  can improve the speed and accuracy of its determination. A ready mix truck will not engage the drum  400  to discharge while the truck is traveling at significant speed. There is a possibility that the vehicle will move at a very slow speed if it has to pour a narrow path. The system  100  can compensate for this possibility and generally can assume that a vehicle traveling at a significant speed will not discharge. A GPS module  240  can be directly integrated into the system  100 , or an external GPS module  240  can be plugged into the USB port  250  to provide speed and location information. This input from the GPS module  240  can improve the determination of rotation direction, especially for brand new drums  400  or when the ready mix truck is operating in low-light conditions. 
         [0040]    Several ready mix companies place stickers or logos  440  on the drum  400  to assist the driver in determining the direction of rotation or for company branding. The presence of these stickers  440  improves the speed and accuracy of the rotation determination similar to the presence of visible marks  420  caused by rust. In both cases, the system  100  uses a visible pattern with multiple points of interest to verify its determination. 
         [0041]    If a pattern of stickers or markers  440  is placed on a ready mix truck drum  400 , that pattern can be used to determine the speed of rotation as well as the direction of rotation. The system  100  is capable of determining the approximate speed of rotation, but if the customer has no interest in determining drum rotation speed, that portion of the system  100  can be disabled. The most critical problem facing ready mix companies is to determine the moment that the concrete is discharged from the drum  400 . This visual direction detection system  100  is capable of determining that moment without calculating the speed of drum rotation. 
         [0042]      FIG. 4  illustrates some examples of where the camera  200  can be mounted on the glass  350  at the rear of the truck cabin. From a proper mounting position, the camera  200  can be focused to see the rust or discoloration marks  420 , a particular logo  440 , or the weld marks  410 . The location of the camera  200  can be changed to achieve the optimal detection of rotation direction according to the specific layout of each ready mix truck. 
         [0043]      FIGS. 5A through 5C  depict a series of images of a ready mix truck drum  400  as it rotates. The system  100  acquires images similar to this series and analyzes the images. The system is able to recognize the visible patterns on the drum and note their location in each image. As the series of images progresses, the location of the visible patterns changes. By comparing the location of a visible pattern across a series of images taken over a known period of time, the system  100  is able to determine both the speed and direction of drum rotation. 
         [0044]    Multiple embodiments of the invention have been described above. The claimed subject matter is not intended to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope of the appended claims.