Patent Application
20140076047
This disclosure relates to volume measurement of a material in a tank or container and has particular usefulness in the context of measuring commodities in an air seeder commodity cart.
When distributing material from a container, it is often beneficial to know the quantity of material in the container. One such material distribution application is in the context of an agricultural air seeder. It is important to know when the material, such as seed or fertilizer, will be exhausted so the machine can be resupplied. Material level sensors have been used to indicate the level. Such sensors have been used to detect when the level drops below a certain point or points, such as one-quarter full, half full or three quarters full. Video cameras have also been used to allow a machine operator to see the material level in the container during operation. The level of material in a tank can also be determined using an ultrasonic or infrared distance sensor to measure the distance from the sensor at the top of the tank to the surface of the material, usually at a single point Such a sensor can be used to provide real time data of the height of the material in the tank.
While knowledge of the material level in the tank is useful to determine when to resupply the tank, this is of limited value. More useful is knowledge of the actual quantity of material in the tank. Recent advances in technology have used load cells supporting a container to continuously measure the weight of material in a tank. However, the ability to accurately weigh a tank or container requires that each container be separated from other containers and scales cannot be used with multiple compartment tanks. Knowing the exact quantity of material in the tank in real time can be useful in automatic meter calibration without a separate calibration procedure with the machine stopped.
The pneumatic distribution system 16 includes a centrifugal fan 26 which is connected to a plenum 28, which is in turn connected by distribution lines 30 to one or more primary distribution manifolds 18, each associated with a product tank 8 or 9. The primary distribution manifolds 18 are connected by distribution lines 30 to a dimpled riser tube 32, which is coupled to a secondary distribution header 34. Secondary distribution lines 36 connect the secondary distribution header 34 to seed boots 38 mounted on the around openers 22.
During operation of the air seeder 2, air and product flow in the pneumatic distribution system 16 from the primary distribution manifold 18 through distribution lines 30 to the dimpled riser tubes 32 which attempt to randomize distribution of product from the secondary distribution headers 34 which are immediately downstream. The secondary distribution headers 34 divide the product substantially evenly into a series of the distribution lines 36 leading to the seed boots 38 on the ground openers 22.
Once the profile of the surface 44 is created from the sensor data, the controller uses the profile and stored data on the size and configuration of the tank 8 to calculate the volume of material in the tank, it is this step that moves beyond mere knowledge of the material height at one or more locations to actual knowledge of the quantity of material in the tank. If the density of the material is known, the weight can then be calculated once the volume is determined. Density information can be stored in a memory using nominal values for different materials. Alternatively, after a known weight of material is supplied to the tank, the surface profile can be determined from distance measurement, the volume calculated and then the density calculated. Operation of the machine may result in compacting of the material thereby increasing the density. This must be accounted for. The use of sensors to generate a surface profile and from there to calculate volume and weight, overcomes the limitations on the use of load cells described above.
Multiple sensors as shown in
Low to midrange consumer cameras typically have three to nine focus points where the sensor determines the distance from the camera to each point. Higher end cameras may have any more focus points. Camera auto-focus sensors typically have the focus points arranged in a grid pattern as shown in
There are various ways a sensor can determine distance, including ultrasonic sound waves and infrared light. In the first case, sound waves are emitted from the sensor, and by measuring the delay in the reflection of the sound waves, distance to the subject is calculated. Several cameras, including the Polaroid Spectra and SX-70 apply an ultrasonic auto-focus sensor. In the case of an infrared sensor, the infrared light is usually used to triangulate the distance to the subject. Compact cameras including the Nikon 35TiQD and 2TiQD, the Canon AF35M, and the Contax T2 and T3 use an infrared system. Other methods of determining the distance to the object instead of triangulation are the time of flight for the reflected signal and the amount of infrared light reflected from the subject.
As with the multiple sensors 50 above, the output signals from the multiple point sensor 60 are communicated to the controller 56. The controller is programmed or configured to receive the distance data from the sensor 60 and determine a profile of the material surface 44. Using the surface profile and stored data on the tank shape, the controller then determines the volume of material in the tank. Material volume can be converted to material weight using density information.
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
