Patent Publication Number: US-10779462-B2

Title: Calibrating an actuator for setting a seed depth for a row unit on a planter

Description:
FIELD OF THE DESCRIPTION 
     The present description relates to agricultural machines. More specifically, the present description relates to setting a planting depth on a planter row unit. 
     BACKGROUND 
     There are a wide variety of different types of agricultural machines. Some agricultural machines include planters that have row units. For instance, a row unit is often mounted on a planter with a plurality of other row units. The planter is often towed by a tractor over soil where seed is planted in the soil, using the row units. The row units on the planter follow the ground profile by using a combination of a downforce assembly that imparts a downforce on the row unit to push disc openers into the ground and gauge wheels to set depth of penetration of the disc openers. Some current downforce assemblies provide a relatively fixed downforce. Some allow an operator to change the downforce applied to the row unit by adjusting a mechanical mechanism on the row unit, and others allow the operator to change the downforce from the operator compartment. 
     In many current systems, the gauge wheels are mounted to the row unit by one or more gauge wheel arms. Setting the seed depth on the planter is done by stopping the planter, exiting the operator compartment and manually adjusting a gauge arm stop to limit movement of the gauge wheel relative to the disc opener. The manual adjustment mechanism often uses a spindle drive, a handle, or another mechanical mechanism that can be used to adjust seed depth. This type of adjustment is somewhat cumbersome and time consuming. It also does not lend itself to frequent changes, because of its cumbersome and time consuming nature. 
     Therefore, many planting operations are performed with sub-optimal planting seed depth settings. This can result in a loss of yield potential. For instance, at the beginning of a corn planting operation, the operator may set the seed depth to two inches and then leave it at that depth until the corn planting operation is completed. The operator may leave it at this depth even though the depth may be sub-optimal for changing environmental or soil characteristics. 
     The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
     SUMMARY 
     A planter row unit is positioned so a gauge wheel and an opener are in a known position relative to one another. A planting depth actuator that travels along an extent of travel to change a relationship between the gauge wheel and opener is positioned at one end of its extent of travel, out of engagement with a gauge wheel arm and is then moved to an engagement position where it engages the gauge wheel arm. The location of the engagement position is identified as a calibration point. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of one example of a planting machine. 
         FIG. 2  shows a side view of one example of a row unit of the planting machine illustrated in  FIG. 1 . 
         FIG. 3  shows one example of a planting depth actuator assembly. 
         FIG. 4  shows the actuator assembly illustrated in  FIG. 3 , in two different positions. 
         FIG. 5  is a perspective view of one example of a portion of the actuator assembly illustrated in  FIGS. 3 and 4 . 
         FIG. 6  illustrates another example of a planting depth actuator assembly. 
         FIG. 7  illustrates another example of a planting depth actuator assembly. 
         FIG. 8  is a block diagram showing one example of a planting machine architecture. 
         FIG. 9  is a block diagram showing one example of a planting depth control system in more detail. 
         FIGS. 10A and 10B  (collectively referred to herein as  FIG. 10 ) show a flow chart illustrating one example of the operation of the planting depth control system shown in  FIG. 9 . 
         FIG. 11  is a block diagram of one example of a planting depth calibration system in more detail. 
         FIG. 12A-12C  (hereinafter referred to as  FIG. 12 ) are flow diagrams illustrating one example of the operation of the planting depth calibration system in more detail. 
         FIGS. 13A-13D  are pictorial/schematic illustrations showing calibration steps. 
         FIG. 14  is a block diagram of one example of a computing environment that can be used in the architectures shown in the previous figures. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of one example of an agricultural planting machine  100 . Machine  100  is a row crop planting machine that illustratively includes a toolbar  102  that is part of a frame  104 .  FIG. 1  also shows that a plurality of planting row units  106  are mounted to the toolbar  102 . Machine  100  can be towed behind another machine, such as a tractor. 
       FIG. 2  is a side view showing one example of a row unit  106 . Row unit  106  illustratively includes a chemical tank  110  and a seed storage tank  112 . It also illustratively includes a disc opener  114 , a set of gauge wheels  116 , and a set of closing wheels  118 . Seeds from tank  112  are fed by gravity into a seed meter  124 . The seed meter controls the rate at which seeds are dropped into a seed tube  120  or other seed delivery system, such as a brush belt, from seed storage tank  112 . The seeds can be sensed by a seed sensor  122 . 
     It will be noted that there are different types of seed meters, and the one that is shown is shown for the sake of example only. For instance, in one example, each row unit  106  need not have its own seed meter. Instead, metering or other singulation or seed dividing techniques can be performed at a central location, for groups of row units  106 . The metering systems can include rotatable discs, rotatable concave or bowl-shaped devices, among others. The seed delivery system can be a gravity drop system (such as that shown in  FIG. 2 ) in which seeds are dropped through the seed tube  120  and fall (via gravitational force) through the seed tube into the seed trench. Other types of seed delivery systems are assistive systems, in that they do not simply rely on gravity to move the seed from the metering system into the ground. Instead, such systems actively capture the seeds from the seed meter and physically move the seeds from the meter to a lower opening, where they exit into the ground or trench. 
     A downforce actuator  126  is mounted on a coupling assembly  128  that couples row unit  106  to toolbar  102 . Actuator  126  can be a hydraulic actuator, a pneumatic actuator, a spring-based mechanical actuator or a wide variety of other actuators. In the example shown in  FIG. 2 , a rod  130  is coupled to a parallel linkage  132  and is used to exert an additional downforce (in the direction indicated by arrow  134 ) on row unit  106 . The total downforce (which includes the force indicated by arrow  134  exerted by actuator  126 , plus the force due to gravity acting on row unit  106 , and indicated by arrow  136 ) is offset by upwardly directed forces acting on closing wheels  118  (from ground  138  and indicated by arrow  140 ) and double disc opener  114  (again from ground  138  and indicated by arrow  142 ). The remaining force (the sum of the force vectors indicated by arrows  134  and  136 , minus the force indicated by arrows  140  and  142 ) and the force on any other ground engaging component on the row unit (not shown), is the differential force indicated by arrow  146 . The differential force may also be referred to herein as the downforce margin. The force indicated by arrow  146  acts on the gauge wheels  116 . This load can be sensed by a gauge wheel load sensor which may be located anywhere on row unit  106  where it can sense that load. It can also be placed where it may not sense the load directly, but a characteristic indicative of that load. Both sensing the load directly or indirectly are contemplated herein and will be referred to as sensing a force characteristic indicative of that load (or force). For example, it can be disposed near a set of gauge wheel control arms (or gauge wheel arm)  148  that movably mount gauge wheels  116  to shank  152  and control an offset between gauge wheels  116  and the discs in double disc opener  114 , to control planting depth. Arms (or gauge wheel arms)  148  illustratively abut against a mechanical stop (or arm contact member-or wedge)  150 . The position of mechanical stop  150  relative to shank  152  can be set by a planting depth actuator assembly  154 . Control arms  148  illustratively pivot around pivot point  156  so that, as planting depth actuator assembly  154  actuates to change the position of mechanical stop  150 , the relative position of gauge wheels  116 , relative to the double disc opener  114 , changes, to change the depth at which seeds are planted. This is described in greater detail below. 
     In operation, row unit  106  travels generally in the direction indicated by arrow  160 . The double disc opener  114  opens a furrow in the soil  138 , and the depth of the furrow  162  is set by planting depth actuator assembly  154 , which, itself, controls the offset between the lowest parts of gauge wheels  116  and disc opener  114 . Seeds are dropped through seed tube  120 , into the furrow  162  and closing wheels  118  close the soil. 
     In prior systems, in order to change the planting depth, the operator of the towing vehicle would dismount the towing vehicle and operate a mechanical actuator that would adjust the position of mechanical stop  150 . This would be done on each row unit. In accordance with one example, actuator assembly  154  can be automatically actuated by a control system, from the operator compartment of the towing vehicle. It can be actuated based on an operator input detected through that control system, or it can be automatically actuated to automatically change the planting depth as row unit  106  is towed across the field. In one example, and as is described in greater detail below, it can be actuated to maintain a desired trench contour or trench profile so that the depth of the seed trench varies, in a desired way. 
       FIG. 3  shows one example of the planting depth actuator assembly  154 , in more detail. Planting depth actuator assembly  154  illustratively includes an actuator  190  that drives rotation of a linkage that, itself, drives movement of mechanical stop  150 . In one example, the linkage can include a drive mechanism  180  which can be coupled to output of action  190 . Drive mechanism  180 , in turn, drives movement of a mechanical stop or wedge  150 , as is described in more detail below. Because  FIG. 3  is a side view, only one opening disc  114 , gauge wheel  116 , closing disc  118  and gauge wheel arm  148  are shown. It will be appreciated, however, that each of these can have another member to form a pair. This is one example only. Similar items to those shown in  FIG. 2  are similarly numbered. 
       FIG. 3  shows that the disc opener disc  114  are rotatably mounted to shank  152  at point  173 . are pulled through the soil in the direction indicated by arrow  160  and they open a trench or furrow  162  in the soil. The seeds are placed into trench (or furrow) 162 . The trench is defined by a bottom soil portion  166 , trench sidewalls (one of which is shown at  168 ) and the soil surface  170 . The vertical distance between the soil surface  170  and the trench bottom  166  is defined as the planting depth. To obtain a desired planting depth, the pair of gauge wheels  116  are forced into contact with, and follow, the soil surface  170 . A downforce system (such as downforce actuator  126  and parallel linage  132  shown in  FIG. 2 ) is used to apply a downforce on row unit  106  to ensure full penetration of the opener discs resulting in ground contact between the gauge wheels  116  and the soil surface  170  with the gauge wheels arm  148  engaging the stop  150 . 
     Gauge wheels  116  are movably connected to the row unit shank  152  by a set of gauge wheel arms  148 . The gauge wheels  116  are each connected to an arm  148  by a rotary joint  172 . Similarly, each arm  148  is connected to shank  152  by rotary joint  174 , so that they are pivotable about a pivot point  156 . As the arms  148  pivot about pivot point  156 , they move upwardly and downwardly in  FIG. 3  to increase or decrease, respectively, the distance between the bottom most points of opening discs  114  and gauge wheels  116 , and thus change the planting depth (the depth of a furrow  162 ). 
     In the example shown in  FIG. 3 , the mechanical stop  150  is formed by a wedge that is located between the gauge wheel arm  148  and a further mechanical stop  176  that may be defined by a portion of the row unit shank  152 . The position of the wedge is illustratively changed along a longitudinal axis  178  of a drive mechanism  180 . As the position of the wedge  150  is changed along axis  178 , it changes the position of the upper limit of rotation of gauge wheel arm  148  about pivot point  156 . Thus, when the gauge wheel  116  is forced into contact with the ground, wedge  150  defines the position of gauge wheels  116  relative to the row unit shank  152  and relative to opening discs  114 , thus defining planting depth. 
     In one example, drive mechanism  180  is a lead screw that is mounted inside the row unit shank  152  using a set of bearings  182  and  184 . The lead screw illustratively has a threaded exterior surface  186  that interacts with a threaded interior surface  188  of a carriage  189  that carries wedge  150  so that, as lead screw  180  rotates within bearings  182  and  184 , it drives movement of wedge  150  along longitudinal axis  178  in a direction that is determined by the direction of rotation of lead screw  180 . Changing the position of wedge  150  along axis  178  thus changes the angle between the longitudinal axis  178  of lead screw  180  and the elongate axis of gauge wheel arms  148 . 
     In one example, actuator  190  drives rotation of lead screw  180  at a controllable speed and in a controllable direction. Actuator  190  may illustratively be an electric motor with a locking member (such as a self-locking worm drive) mounted between the electric motor and lead screw  180 . This can serve to increase the torque available to turn lead screw  180 . The self-locking characteristic of the worm drive allows the worm drive to hold the set depth while downforce is acting on gauge wheels  116 , without torque being applied to the electric motor or other actuator  190 . This also illustratively allows the position of wedge  150  to be changed while downforce is acting on the gauge wheel  116 , and allows the actuator  190  to overcome frictional forces between wedge  150  and gauge wheel arms  148 , as well as those forces between wedge  150  and mechanical stop  176 , and further frictional forces between the interior threaded surface  188  of carriage  189  and the exterior threaded surface  186  of lead screw  180 . A different gear ratio may be used, depending upon the force available from actuator  190 . In one example, the gear ratio may be 1:20, although this is just one example. 
       FIG. 4  shows gauge wheels  116  in two different positions relative to disc opener  114 . The items in  FIG. 4  are similar to those shown in  FIG. 3 , and they are similarly numbered. However, when the items, are at a first planting depth setting, the items are labeled “A” and when in a second depth setting, they are labeled “B”. In position B, it can be seen that the planting depth is deeper. This is because wedge  150  is moved along axis  178  more toward bearing  182  so that gauge wheel arm  148 B is rotated vertically upward about point  156  more than in position A. Thus, the distance between the lower most point of disc opener  114  and gauge wheel  116 B is relatively large. In position A, wedge  150  is moved along axis  178  more toward bearing  184  so that gauge wheel arm  148 A is rotated further downwardly about point  156 . Thus, the lower most point of disc opener  114  and that of gauge wheel  116 A are relatively close to one another. Thus, in position B, the trench  168 B is relatively deep while in position A, the trench  168 A is relatively shallow. 
     It should be noted that different configurations of wedge  150  are contemplated herein. For instance, in one example, wedge  150  may illustratively be configured as a single piece that engages both of the left and right gauge wheel arms  148  (both the arm  148  shown in  FIG. 4  and the other gauge wheel arm which is not shown in the figures, and which corresponds to the other gauge wheel, also not shown in the figures). However, the wedge is illustratively configured as a rocker so that it can rotate slightly about axis  178 . This rocker configuration is used to allow some independent motion of the left and right gauge wheels  148  relative to one another. This may occur, for instance, when the row unit  106  is traveling over uneven terrain. 
     In another example, however, wedge  150  may have no direct contact with the gauge wheel arms  148 . Instead, a separate rocker mechanism can be interposed between wedge  150  and the corresponding set of gauge wheel arms  148 . In still another example, a separate wedge can interact with each separate gauge wheel arm  148 . These and other configurations are contemplated herein. 
     It will also be noted that, in one example, wedge  150  can also include a downforce sensor. The downforce sensor may be a load cell or another sensing device to determine the downforce between the corresponding gauge wheels  148  and the ground (e.g., the downforce margin). 
     In another example, wedge  150  or carriage  189  can incorporate a scraper, a rubber lip, or other mechanisms that can be used to clean the lead screw  180  of debris. It can also include a set of plastic bristles or other cleaner. 
     In yet another example, the gauge wheel arms  148  may illustratively be curved. This can be done so that the position where force is induced on the rocker or wedge  150  and/or the direction and magnitude of the applied force on the rocker or wedge  150  is substantially equal for all depth settings. It will be appreciated that, instead of curving arms  148 , the surface of wedge  150  or a corresponding rocker may be curved as well, or both the wedge  150  and arms  148  can be curved. 
       FIG. 5  is a perspective view of one example of the planting depth actuator assembly  154 , in more detail. Some of the items are similar to those shown in  FIG. 3  above, and they are similarly numbered.  FIG. 5  shows that, in one example, a frame structure  200  supports lead screw  180  and bearings  182  and  184  in, or attached to, shank  152  (not specifically shown in  FIG. 5 ). The wedge  150  has carriage  189  with the threaded interior surface  188  that travels over the threaded exterior surface  186  of lead screw  180 .  FIG. 5  also shows that the lower portion of wedge  150  is formed as a rocker  202 . Rocker  202  may illustratively include a first arm engaging portion  204  that engages gauge wheel arm  148  and second arm engaging portion (not shown) that engages the second gauge wheel arm  148  (also not shown). It rocks generally in the directions indicated by arrow  206  about an axis  208  of a mechanical assembly that fastens rocker  202  to the wedge  150  so that it moves with wedge  150  as wedge  150  travels along lead screw  180 . The rocking movement about axis  208  accommodates some independent movement of the gauge wheel arms. 
       FIG. 5  also shows one example of an actuator  190  which includes motor  210  that drives rotation of a self-locking worm drive  212  which rotates within a set of bushings  214  and  216 . Motor  210  illustratively drives rotation of the worm portion of worm drive  212 . Rotation of the worm portion is illustratively translated into rotational movement of lead screw  180  through a worm gear (not shown) in a self-locking way. Worm drive  212  thus acts as a locking member that locks wedge  150  in place. Therefore, any torque or other forces imparted to the rocker mechanism or the wedge  150  are not fed back to the drive output of motor  210 . Instead, they are transmitted back to shank  152  through frame structure  200 . 
       FIG. 6  shows another example of a planting depth actuator assembly  154  that can be used to automatically set the planting depth of a row unit  106 . Some items are similar to those shown in previous figures, and they are similarly numbered. In the example shown in  FIG. 6 , a rocker  220  (or other gauge wheel arm contact member or abutment member) is carried by an adjustment lever  222  that rotates relative to shank  152  about axis of rotation  224 . As it rotates about axis  224 , it drives member  220  to impart force on, and rotate, gauge wheel arm  148  downward about pivot point  156 , or it allows gauge wheel arm  148  to move upward about pivot point  156 . Adjustment arm  222  illustratively has a gear wheel portion  225  that interacts with the threaded surface of lead screw  180 . As lead screw  180  rotates, it thus drives movement of the gear wheel portion  226  to, correspondingly, drive rotation of arm  222  about axis  224  in the directions indicated by arrow  228 . By choosing the geometry of the adjustment arm  222  and the gear wheel portion  226 , the point at which force is applied from abutment member  220  to arm  148  can be adjusted. In one example, it can be adjusted so the point at which member  220  applies force to arm  148  is the same, regardless of the planting depth. Also, by choosing the geometry of adjustment arm  222 , the force needed to rotate lead screw  180 , in order to drive movement of member  220 , can be adjusted as well. 
     In the example illustrated, lead screw  180  may instead be a self-locking worm drive which is connected to electric motor  210  by a worm gear. A reduction gear unit can be implemented to deliver desired torque. The position of the adjustment arm  222  can thus, in one example, only be changed by motor  210  to actively drive the worm of the worm drive  180  because of the self-locking nature of the worm gear. When the motor is not actively driving the worm portion of worm drive  180 , then any forces that are occurring on the worm drive  180  are transmitted from there to the mounting points of bearings  182  and  184 , and finally to shank  152 . This allows isolation of any impact forces that may impact gauge wheel  116 , and thus gauge wheel arm  148 , from the electric motor  210  and thereby protects electric motor  210  from peak loads. 
       FIG. 7  shows another example of a planting depth actuator assembly  154 . Some items are similar to those shown in  FIG. 6 , and they are similarly numbered. In the example shown in  FIG. 7 , the upper limitation of movement of gauge wheel arm  148  is controlled by rotation of cam  230 . The cam defines a groove  232  to guide the movement of a support arm  222  and abutment member (or rocker)  220 . As cam  230  is rotated, a mounting pin  234  follows groove  232 . Because pin  234  resides in and follows groove  232 , an upward bearing is provided in situations where the planter or row unit  106  is lifted and the gauge wheel  116  and arm  148  do not press abutment member  220  against the cam  230 . A second groove defined by groove defining member  236  guides movement of arm  222  and abutment member  220  in a direction generally indicated by arrow  238 . Thus, as cam  230  is driven by an actuator (such as an electric motor), pin  234  follows groove  232  but it also follows the groove defined by frame structure  236 . Therefore, as cam  230  is driven, this drives vertical movement (in the direction indicated by arrow  238 ) of abutment member  220 . Because abutment member  220  bears against the gauge wheel arm(s)  148 , it thus causes rotation of the gauge wheel arms  148  about their pivot points  156  (as shown with respect to the above figures). 
     In the example shown in  FIG. 7 , it can be seen that any vertical force(s) resulting from the gravitational force of the row unit  106  and any additional applied downforce, less the resistance of the soil to reach the desired depth, is born solely by cam  230 . The actuation of the cam can be implemented either directly by integrated teeth partially on the shorter part of the cam or the cam can be connected to a drive shaft on which a gear, such as gear  242 , is mounted. A relatively low speed and a relatively high torque is then applied to the cam  230  in order to control the corresponding planting depth. In another example, a gear box  244 , (or gear reduction) between cam  230  and gear  242  (which is driven by motor  210 ) can be provided. Gear box  244  can have a relatively high transmission ratio in order to supply torque as well as precise control of the depth. A worm drive can be used for the same reasons as described above (e.g., a high transmission ratio and self-locking features). A planetary gear box or other types of gear boxes can be used as well. 
       FIG. 8  is a block diagram of one example of a planting machine architecture  250  for automatically controlling planting depth. Architecture  250 , includes a planting machine, such as planter  100  (also shown in  FIG. 1 ) which has a plurality of row units (such as row units  106  also shown in  FIG. 1 ) and it can have other items  251 . Each row unit may have one or more sensors  252 - 254 . Row unit  106  is also shown with other mechanisms  255 . Mechanisms  255  illustratively include gauge wheels  116 , disc opener  114 , closing wheels  118 , and some or all of the other mechanisms shown in previous figures on row unit  106  or different mechanisms. 
     Row unit  106  can have a wide variety of other things  256  as well. 
     Also, as shown in  FIG. 8 , each row unit  106  may have the downforce actuator  126  and a planting depth actuator assembly  154 . In some examples, downforce actuator  126  illustratively exerts additional downforce on row unit  106  to keep gauge wheels  116  in contact with the ground, as discussed above with respect to  FIG. 2 . Also, in one example, downforce actuator  126  may also be an upforce actuator which can be used to lift the gauge wheels  116 , relative to the disc opener  114 . In examples where downforce actuator  126  is also an upforce actuator that can exert upward force on the gauge wheels  116 , then planting depth actuator assembly  154  may not be needed. These and other examples are described in more detail below. 
     Planting depth actuator assembly  154 , as discussed above, illustratively controls the distance between the lower most points of the gauge wheels  116  and disc opener  114 . Therefore, it can be actuated to control the planting depth at which row unit  106  plants seeds. Sensors  252 - 254  can be any of a wide variety of sensors. For instance, in one example, sensor  252 - 254  include a downforce sensor that senses the downforce exerted by downforce actuator  126  on row unit  106 . In another example, they can be a combination of sensors and logic that senses a downforce margin, as described above. Sensors  252 - 254  may illustratively include a position sensor that senses the position of gauge wheels  116  relative to disc opener  114 . It can be a sensor that senses the depth of the seed trench. The sensors can include a wide variety of other sensors as well, such as sensors that sense soil characteristics (such as moisture, soil compactness, soil type, etc.), and environmental characteristics. The sensors can sense a wide variety of other variables (machine variables, soil variables, environmental variables, etc.) as well. 
       FIG. 8  also shows that, in one example, control system  260  can illustratively receive inputs from additional sensors  262 - 264 , and it can also interact with operator interface mechanisms  266 . Operator interface mechanisms  266  can include operator input mechanisms  268  that operator  270  can interact with in order to control and manipulate control system  260 , and some parts of planting machine  100 . 
     Therefore, in the example illustrated, control system  260  can include one or more processors  272 , a data store  274 , dynamic downforce/upforce control logic  276 , planting depth control system  278 , operator interface logic  280 , and it can include a wide variety of other items  282 . Dynamic downforce/upforce control logic  276  is included in scenarios where downforce/upforce actuator  126  can be dynamically controlled by operator  270 , from the operator compartment of the tractor or other towing vehicle, to controllably impart a either downforce on row unit  106 , an upforce, or both. 
     Planting depth control system  278  illustratively receives sensor inputs and/or operator inputs. It controls planting depth actuator assembly  154 , on each row unit  106 , in order to control the planting depth used by the row units  106  on planting machine  100 . 
     Operator interface mechanisms  266  can include a wide variety of mechanisms, such as a display screen or other visual output mechanisms, audio mechanisms, haptic mechanisms, levers, linkages, buttons, user actuatable display elements (such as icons, displayed links, buttons, etc.), foot pedals, joysticks, steering wheels, among a wide variety of others. Operator interface logic  280  illustratively controls outputs on the operator interface mechanisms  266  and can detect operator inputs through the operator input mechanisms  268 . It can communicate an indication of those inputs to other items in control system  260  or elsewhere. 
     Sensors  262 - 264  can also be a wide variety of different types of sensors that can be used by dynamic downforce/upforce control logic  276 , planting depth control system  278 , or other items. Some of these are described in greater detail below. 
       FIG. 8  shows that, in one example, architecture  250  includes a planting machine (such as planting machine  100  shown in the previous figures) and a control system  260 . Control system  260  can be carried by the towing machine that is towing planting machine  100 , it can be carried by planting machine  100 , or it can be distributed among the towing machine, planting machine  100  and a wide variety of other locations. In one example, control system  260  generates control signals to control the planting machine  100 , and as will be described in greater detail more specifically below, the planting depth that the row units on planting machine  100  are using to plant seeds.  FIG. 8  also shows that, in one example, control system  260  can receive sensor signals from a plurality of different sensors  262  and  264 . It also shows that operator  270  (which may be the operator of the towing vehicle) can interact with control system  260  through operator interface mechanisms  266  which can include, for instance, operator input mechanisms  268 . 
       FIG. 9  shows one example of planting depth control system  278  in more detail. In the example shown in  FIG. 9 , planting depth control system  278  can include target depth identifying logic  290 , force/speed estimation logic  292 , control signal generator logic  294 , planting depth calibration system  295 , and it can include a wide variety of other items  296 . Force/speed estimation logic  292  illustratively receives a target depth which identifies a desired planting depth for planting machine  100 . It can also identify individual planting depths for individual row units  106  on planting machine  100 . It can receive the target depth from target depth identifying logic  290 , from an operator or from another source. 
     Target depth identifying logic  290  can identify the target depth in a variety of different ways. For instance, it can receive an operator target depth input  318  that identifies a target depth input by the operator  270 . It can include map data  320  which includes a wide variety of different information correlated to different geographic locations within the field that is being planted. The information can include soil moisture information, soil type information, soil compactness information and a wide variety of other information that can be used by target depth identifying logic  290  to identify a desired target depth. Logic  290  can also receive sensor data  322  which is indicative of one or more variables that may have an effect on the identified target planting depth. Again, for instance, sensor data  322  can be data generated from a soil moisture sensor, a soil type sensor, a soil or environmental characteristic sensor that senses other soil characteristics (such as compaction or other characteristics) or other environmental characteristics, such as topology, position, etc. Sensor data can include data generated by machine sensors that sense machine variables or other items. 
     As planting machine  100  moves about the field, it may be that the target planting depth identified by target depth identifying logic  290  changes based on the location of planting machine  100 . Therefore, logic  290  may receive a location sensor input indicative of that location, and other inputs that bear on the desired target planting depth, and it may modify the target planting depth as machine  100  moves about the field. Thus, the target planting depth provided by logic  290  to force/speed estimation logic  292  may vary. All of these and other scenarios are contemplated herein. 
     Force/speed estimation logic  292  is also shown receiving, by way of example, sensor data  298 , one or more operator inputs  300 , and it can include a wide variety of other inputs  302 . It illustratively generates an estimate of the force and speed that will be needed to control planting depth actuator assembly  154  in order to achieve the target planting depth. Thus, it can include force estimation model  304  that is used to estimate the force that will be needed to achieve the target planting depth. It can also illustratively include actuation speed estimation model  306  that generates an estimate of the speed at which planting depth actuator assembly  154  is to be actuated to move from a current planting depth to the target planting depth. It can include other items  308  as well. By way of example, force estimation model  304  may estimate a force that needs to be applied to the gauge wheel arms  148  in order to move the gauge wheel in the desired direction (either up or down relative to the disc opener  114 ). Actuation speed estimation model  306  illustratively generates an estimate indicative of how quickly actuator assembly  154  should be actuated to move the gauge wheels to the desired target depth. For instance, it may be that it is undesirable to change the depth profile of the seed trench too quickly. Instead, it may be that it is desired to change planting depth gradually to achieve a desired trench contour or trench depth profile. Thus, actuation speed estimation model  306  can generate an estimate indicating how quickly the actuator assembly  154  should be actuated to change the planting depth. 
     In one example, the force estimation and speed estimation are provided to control signal generator logic  294  which illustratively includes downforce/upforce control signal generator  310 , planting depth actuator control signal generator  312 , and it can include other items  314 . In some examples, control signal generator  310  will control the downforce/upforce actuator  126  (shown in  FIG. 8 ) to remove any applied downforce or to supply an upforce so that the planting depth actuator assembly  154  need not overcome any applied downforce in changing the planting depth. Control signal generator  312  then illustratively controls the planting depth actuator assembly  154  to change the planting depth at a speed corresponding to the speed estimated by model  306 . The output of control signal generator logic  294  is illustratively a set of control signals  316  that are output to row units  106  in order to control downforce/upforce actuator  126  and/or planting depth actuator assembly  154 . 
     As mentioned above, one parameter associated with planting is the depth below the surface of the soil that seed is planted. Various methods have been shown for sensing the depth at which a seed is being placed, while planting. The planting depth (along with other variables, such as soil texture, temperature, moisture, etc.) can effect emergence time and plant vigor. Generally, yield is optimized by having all plants emerge as evenly as possible, but there may be conditions in which it is best to stagger emergence or plant maturity. In addition, the emergence may differ, from one piece of ground to another, if planting depth is maintained constant. Therefore, varying plating depth may be used to obtain uniform emergence as well. 
     While the row unit is engaging the ground and planting, the forces needed to change the planting depth on-the-go, can be significant. Actuators that are large enough and strong enough to operate against such forces can be relatively large and costly. One way of changing planting depth, as is described below, may involve stopping the planting machine, lifting the row units out of the ground, and then automatically actuating the actuator assembly  154  to change the planting depth automatically, before continuing. This may happen at the end rows or it may occur during a brief pause of forward motion to raise the machine while planting to facilitate such an adjustment. The actuators needed to change planting depth can then be relatively small because they need not overcome the large downforces involved with some types of planting equipment. 
     In another example that is described in more detail below, the downforce/upforce control signal generator  310  controls the downforce/upforce actuator  126  in conjunction with the planting depth actuator control signal generator  312  controlling the planting depth actuator assembly  154 , to change planting depth. Control signal generator  310  can control downforce actuator  126  to momentarily relieve any applied downforce, and to optionally provide the force needed to either raise (upforce) or further lower (downforce) one or more row units  106  into the ground with respect to where the gauge wheels  116  are riding at the soil surface. Control signal generator  312  can then control planting depth actuator assembly  154  to simply lock in the new desired depth. This reduces the need of assembly  154  to be able to exert the extra force (and thus incur the extra cost and extra structural stress) that is needed to overcome the downforce, while still allowing the row unit  106  to adjust planting depth on-the-go. Thus, it can be seen that in one example, the downforce/upforce control signal generator  310  can be used to provide all of the power needed to change the planting depth, in which case planting depth actuator control signal generator  312  controls planting depth actuator assembly  154  to simply lock in the new depth. In another example, the downforce/upforce control signal generator  310  can generate a portion of the needed force to adjust the relationship between gauge wheels  116  and opener  114 , or it can simply be used to remove any dynamically applied downforce so the planting depth can be made using a smaller actuator. In these latter two scenarios, the planting depth actuator assembly  154  includes an actuator in addition to actuator  126  which provides additional planting depth adjustment force to change the relationship between gauge wheels  116  and disc opener  114 , and to make the planting depth adjustment, and then to lock that adjustment in place. 
     Also, it will be noted that, in one example, planting depth control system  278  controls planting depth using a control curve that plots desired planting depth against the position of the mechanical stop  150  on the planting depth actuator assembly  154 . Calibration of the control curve may be used to accommodate for changes in the relationship between the planting depth and the position of mechanical stop. For instance, as the opener  114  and gauge wheels  116  are used, they can wear at different rates. Manufacturing and assembly tolerances can also lead to changes. Therefore, as discussed in greater detail below with respect to  FIGS. 11-13 , calibration system  295  can calibrate the control curve. 
     Before describing the operation of planting depth control system  278  in more detail, a number of things will first be noted. When the planting depth of a row unit is changed, it can be changed either from a shallower depth to a deeper depth, or from a deeper depth to a shallower depth. When the planting depth is changed within a field, as the planting machine  100  is moving and planting (e.g., when it is changed on-the-go), it may be desired that the transitions between two planting depth settings and corresponding trench contours be uniform. That is, to be uniform, the trench contour when moving from a shallow planting depth to a deeper planting depth should be the same as the trench contour when moving from a deeper planting depth to a shallower planting depth. 
     This can be very difficult to achieve because the forces required by the actuator assembly  154  to go from a deep planting depth to a shallow planting depth are often much larger than to go in the opposite direction (from a shallow planting depth to a deeper planting depth). This is because the downforce on the row unit  106  is acting against the transition from a deep planting depth to a shallow planting depth. Therefore, in order to reduce the planting depth, the entire row unit  106  must be lifted against its weight and against any downforce provided by an active (pneumatic or hydraulic) or passive (mechanical spring) downforce system  126 . Even if the downforce actuator  126  is dynamic (in that it can be controlled from the operator compartment or by a control system on-the-go), and even though the extra downforce added by the downforce actuator  126  can be relieved, there normally still remains significant force acting against the transition from deep to shallow planting depths due to the weight of the row unit  106 , itself. When the downforce actuator  126  is not dynamic, then the difference in forces acting against the transition from deep to shallow versus the forces acting against the transition from shallow to deep are even significantly larger. 
     Because the forces acting against the change in planting depth are much different, depending upon the adjustment direction (e.g., deep to shallow or shallow to deep), it can be very difficult to achieve a uniform trench contour when moving from shallow to deep and deep to shallow. For instance, it can take more time to overcome the force on the row unit  106  when moving it in one direction than to overcome the force when moving it in the other direction. This can make the trench contour (the change from the current planting depth to the target planting depth much steeper in one direction than in the other. Further, attempting to actuate a depth setting mechanism (such assembly  154 ) without previously obtaining an estimation of the required actuation force can lead to unwanted behavior which is known as backlash. In a backlash scenario, where the actuation force is not known before attempting to make the depth setting adjustment, the planting depth may actually move in the wrong direction before it begins moving in the right direction. By way of example, when moving from a deep planting depth to a shallower planting depth, the entire force on the row unit (as described above) must be overcome. The depth setting actuator may not normally be active at all times. Therefore, if a locking mechanism, that is used to hold the row unit at a desired planting depth, is unlocked so that an adjustment can be made, then when starting to change the planting depth, the row unit  106  may begin moving to even a deeper planting depth before it begins moving to a shallower planting depth, which results in a very undesirable trench contour. However, the present system estimates the actuation force and actuation speed that are needed so that that force can be immediately applied when (or just prior to when) the depth setting mechanism is unlocked. This avoids the undesired trench contour where the planting depth may actually move in the wrong direction before it eventually moves to the target planting depth. 
     In accordance with one example, planting depth control system  278  illustratively controls the planting depth actuator assembly  154  such that it has the same adjustment characteristics independent of the direction of adjustment. It can also include information about the planting speed to allow the characteristics of the adjustment to be consistent in a georeferenced coordinate system so that the same trench contour can be achieved at different planting speeds. 
       FIGS. 10A and 10B  (collectively referred to herein as  FIG. 10 ) illustrate a flow diagram showing one example of the operation of planting depth control system  278  and a row unit  106  of planting machine  100 , in changing planting depth, in more detail. It is first assumed that planter  100  is operating in a field. This is indicated by block  330  in the flow diagram of  FIG. 10 . Force/speed estimation logic  292  then receives a target planting depth. This is indicated by block  332 . Again, as discussed above, this can be based on an operator input  318 . This is indicated by block  334 . It can also be from an automated system, such as target depth identifying logic  290 . This is indicated by block  336 . It can be received in a wide variety of other ways as well, and this is indicated by block  338 . 
     Adjustment identifying logic  303  then illustratively receives the target depth, and a current planting depth. This is indicated by block  340  in the flow diagram of  FIG. 10 . The current planting depth can be an estimated planting depth that is estimated based on sensor signals that sense the position of gauge wheels  116  and openers  114 . It can also be a directly sensed planting depth that uses a planting depth sensor to sense the depth of the seed trench or furrow. 
     Adjustment identifying logic  303  then identifies whether an adjustment is to be performed based on the received target planting depth and the current planting depth. If so, it illustratively identifies a magnitude of the adjustment and a direction for the adjustment (such as how big the adjustment is and whether it is to be made to move the planting depth from shallower to deeper or deeper to shallower). It provides these items to force estimation model  304  and actuation speed estimation model  306 . Determining whether an adjustment is to be performed, and the magnitude and direction of the adjustment, is indicated by blocks  342  and  344  in  FIG. 10 . 
     It will be noted that models  304  and  306  can be integrated into a single model that receives the inputs and generates outputs indicative of the estimated force and speed of actuation. They can be two separate models that process the inputs in parallel or sequential models where the output of one model feeds into the input of another model. All of these and other architectures are contemplated herein. 
     It will also be noted that force/speed estimation logic  292  (and models  304 - 306 ) can detect or receive a wide variety of inputs that can be used to generate the outputs. This is indicated by block  348 . For instance, the inputs can include an input indicative of the current planting depth and the current actual planting depth setting. This is indicated by block  350 . They can include the magnitude of the planting depth adjustment and direction of the planting depth adjustment as indicated by block  352 . They can include a wide variety of crop or environmental sensor signal data or map data  354 . This can include such things as crop characteristics sensed by crop characteristic sensors, environmental characteristics sensed by environmental characteristic sensors, topology information input by a topology map. Among a wide variety of other things. The inputs can also include the downforce  356  acting on the row unit  106  as well as the downforce margin  308 . Examples of these are described above. 
     Logic  292  can receive a ride quality value  360  indicative of a ride quality of the row unit  106 . This value can be generated by accelerometers that generate a signal indicative of accelerations measured on the row unit  106 , or in other ways. It can receive a planting speed input  362  indicative of the ground speed of the planting machine  100 . It can include an input identifying system kinematics (such as the measurements, angles, and other values that define the kinematics of the mechanisms used in adjusting planting depth). The system kinematics are indicated by block  364  in the flow diagram of  FIG. 10 . And it can include a wide variety of other inputs, such as gauge wheel position, or other items  366 . 
     Force estimator model  304  and actuation speed estimation model  306  then generate an estimate of the force and speed of actuation to change the planting depth to the target depth. This is indicated by block  368 . This can be based on a desired trench contour  370 . The desired trench contour  370  may define how quickly the depth is to be changed or the magnitude of the change per lineal foot of trench, or other things. Thus, given the planting speed and the adjustment magnitude, the force and speed estimate may be output to change the planting depth based on the desired trench contour. 
     Again, the estimations can be generated using one or more models. This is indicated by block  372 . 
     The depth adjustment can also be made through a series of incremental changes. This is indicated by block  374 . By way of example, it may be desirable to make a planting depth adjustment in incremental steps. Therefore, the output of force/speed estimation logic  292  may be an output indicating how to control the planting depth actuator assembly  154  to move from the current planting depth to the target planting depth in a series of incremental steps. This may be done instead of controlling the actuator assembly  154  to move continuously from the current depth to the target depth. The estimate of force and speed of actuation to change the current planting depth to the target planting depth can be done in a wide variety of other ways as well, and this is indicated by block  376 . 
     As discussed above, in one example, the force and speed estimates may be made in a system that does not have any additional applied downforce or that does not have a dynamically changeable downforce (such as in a system that does not have a hydraulic or pneumatic downforce actuator but is instead in a system that has a relatively static downforce system, such as one that imparts downforce through a set of mechanical springs or in other ways). 
     If, as indicated by block  378 , the planting depth adjustment is not to be made against an actively applied downforce, then planting depth actuator control signal generator  312  illustratively controls the planting depth actuator assembly  154  to apply the estimated force (received from model  304 ) at the actuation speed (received from model  306 ) to change the planting depth. This is indicated by block  380 . Again, this can be provided as a continuous signal to continuously actuate the actuator assembly  154  (e.g., to turn the lead screw  180  or other actuator) to move the gauge wheel arms  148  to change the planting depth in one continuous control step. It can also be done by making incremental changes that incrementally move the gauge wheel arms  148  to change the planting depth incrementally, from the current planting depth to the target planting depth. It can be made in other ways as well. 
     If, at block  378 , it is determined that the planting depth change is to be made against an actively applied downforce, then, at block  382 , downforce control signal generator  310  determines whether the downforce is applied by a dynamically changeable system, or whether it is a relatively static (e.g., mechanical spring-based) system. If there is an active downforce applied to the row unit, but it is not dynamically changeable, then, processing again continues at block  380  where planting depth actuator control signal generator  312  generates control signals to control the planting depth actuator assembly  154  to change the planting depth as discussed above. 
     However, if, at block  382 , it is determined that the actively applied downforce is dynamic in nature, and that it can be controlled on-the-fly, then downforce control signal generator  310  generates control signals to control downforce actuator  126  to remove the actively applied downforce. This is indicated by block  384 . In the example described herein, this is done by controlling the downforce actuator  126  to become passive or to control the actuator to actively remove the downforce in other ways as well. This is indicated by blocks  386  and  388 . Also, in one example, the row unit can be temporarily lifted out of the ground so that the actively applied downforce is no longer working against the depth setting change (e.g., change can be made during a headland turn or during a brief pause while the row unit  106  is lifted out of the ground). These are examples only. 
     Planting depth actuator control signal generator  312  then generates control signals  316  to control the planting depth actuator assembly  154  to change the planting depth. This is indicated by block  390  in the flow diagram of  FIG. 10 . It will be noted that, as described above, the planting depth actuator assembly  154  may be incorporated into the downforce actuator  126 , so that the downforce actuator  126  also includes an upforce actuator that can exert upforce on the row unit, instead of just downforce. In that case, the upforce actuator can be controlled in making the planting depth change as well. This is indicated by block  392 . The planting depth can be changed by controlling a separate planting depth actuator assembly  154 , as discussed above. This is indicated by block  394 . The actuator (e.g., the motor) in the planting depth actuator assembly  154  can be controlled at the estimated actuation speed so that the planting depth adjustment is made over a certain period of time. This is indicated by block  396 . The planting depth actuator assembly  154  can be controlled based on a desired trench contour. For instance, it can be controlled to make the adjustment, while considering the speed of the planting machine  100 , so that the change from the current depth to the target depth is made according to a desired trench contour (so that the trench does not change depth too rapidly over a given lineal distance) or otherwise. Controlling the planting depth actuator assembly based on a desired trench contour is indicated by block  398 . 
     Once the new planting depth is achieved, then planting depth actuator control signal generator  312  generates control signals to control the planting depth actuator assembly  154  to lock the new planting depth in place. This is indicated by block  400 . By way of example, it may be that the planting depth actuator assembly  154  includes a worm drive. In that case, once the target planting depth is achieved, the worm drive is self-locking. In another example, the new planting depth can be locked in other ways so that forces or accelerations applied to the row unit  106  through the gauge wheels  116  do not transmit back to the actuator (e.g., the electric motor or other motor) in the planting depth actuator assembly  154 . Instead, those forces or accelerations are illustratively transmitted to the frame of the planting machine, such as the shank  152 , or other structural mechanisms. 
     The planting depth adjustment can be made in a wide variety of other ways as well. This is indicated by block  402  in the flow diagram of  FIG. 10 . 
     Once the planting depth adjustment has been made and locked in, then downforce control signal generator  310  illustratively controls downforce actuator  126  to reapply the active downforce that was removed at block  384 . Reapplying the downforce after the planting depth adjustment is made is indicated by block  404  in the flow diagram of  FIG. 10 . 
     It will be appreciated that, in one example, planting depth control system  278  can continue to monitor various sensor signals and other inputs and make planting depth changes, on-the-go, until the planting operation is completed. This is indicated by block  406  in the flow diagram of  FIG. 10 . 
       FIG. 11  is a block diagram of one example of planting depth calibration system  295 . In the example shown in  FIG. 11 , system  295  is seen receiving a calibration start trigger  410 , motor torque signal  412 , and it can receive a wide variety of other items  414 . Based on the received items, it outputs an adjusted control curve  416  that planting depth control system  278  can use to control planting depth. As discussed above, control signal generator logic  294  can access a control curve that plots desired planting depth versus an indication of position of the mechanical stop  150 . However, the position of mechanical stop  150  is determined based upon the kinematics of the physical system (such as the measurements, angles, physical relationships, etc., in portions of the row unit and planting depth actuator assembly  154  that are used to set planting depth). The various kinematic values can be obtained at the time of manufacture, or they can be input later. Some of those values can also be sensed. 
     There are some conditions under which the kinematic values may change. For instance, as a row unit  106  is used, the openers  114  and gauge wheels  116  may exhibit wear. This can cause their diameters to change, and they may not change uniformly with respect to one another. Therefore, the position of mechanical stop  150 , as it bears against gauge wheel arms  148 , may result in a different planting depth than before the gauge wheels  116  and openers  114  had worn. Also, the kinematic values used to generate the control curve may change based on manufacturing and assembly tolerances. Therefore, from one row unit to the next, the kinematic values may be slightly different, even when the parts are new. These and other factors can affect the kinematic values and can thus affect the relationship between the position of mechanical stop  150  along lead screw  180 , and the resulting planting depth. Thus, planting depth calibration system  295  can intermittently run a calibration process that adjusts the control curve based upon the new kinematic values identified during the calibration process. The adjusted control curve  416  can then be used by planting depth control system  278  to control planting depth. 
     In the example shown in  FIG. 11 , planting depth calibration system  295  illustratively includes calibration trigger detection logic  418 , arm contact member position logic  420 , motor torque sensing logic  422 , motor revolution tracking logic  424 , arm contact member position detection logic  426 , calibration curve zero point identifier logic  428 , control curve adjustment logic  430 , wear calculation logic  431 , and it can include a wide variety of other items  432 . Before describing the operation of system  295  in more detail, a brief description of some of the items in system  295 , and their operation, will first be provided. 
     Calibration trigger detection logic  418  detects a calibration start trigger  410  that indicates that a calibration operation is to be performed. This can include an operator input, or it can include an automated trigger, such as where the system monitors a number of acres that have been planted since the last calibration process was performed. These and other triggers are discussed below. 
     Arm contact member positioning logic  420  illustratively generates an output to control signal generator logic  294  (shown in  FIG. 9 ) to generate control signals to move mechanical stop (or arm contact member)  150  to a desired position along lead screw  180 . Motor torque sensing logic  422  illustratively receives a motor torque signal  412  indicative of the torque of the motor driving lead screw  180 , in planting depth actuator assembly  154 . Motor revolution tracking logic  424  can include a revolution sensor, or another sensor that senses a number of revolutions performed by the output of the motor driving lead screw  180 . Arm contact member position detection logic  426  illustratively detects the position of the mechanical stop (or arm contact member)  150 . This is described in greater detail below. Calibration curve zero point identifier logic  428  illustratively identifies a new calibration point, and control curve adjustment logic  430  recalibrates (or adjusts) the control curve, based upon calibration points that are identified during the calibration operation. Wear calculation logic  431  can calculate wear on opener  114  and/or gauge wheels  116 . This is also discussed in greater detail below. 
     As mentioned, control curve adjustment logic  430  adjusts the control curve based upon the calibration points identified by calibration point identifier logic  428 . In one example, the calibration process can be performed for a plurality of different calibration points, and the control curve can be adjusted based upon all of those points. In another example, the calibration process can be run to identify a single calibration point, and the control curve can be adjusted based upon that calibration point. 
       FIGS. 12A-12C  (hereinafter referred to as  FIG. 12 ) show a flow diagram illustrating one example of the operation of planting depth calibration system  295  in performing a calibration process.  FIGS. 13A-13D  are pictorial/schematic illustrations of a portion of row unit  106 , to illustrate different parts of the calibration process. Some items in  FIGS. 13A-13D  are similar to those shown in  FIG. 4 , and they are similarly numbered.  FIGS. 12A-13D  will now be described in conjunction with one another. 
     In one example, calibration trigger detection logic  418  first detects a calibration start trigger. This is indicated by block  434  in the flow diagram of  FIG. 12 . The calibration start trigger  410  can take a variety of different forms. For instance, it can be an operator input  436 , or it can be an indication that a usage threshold has been reached, as indicated by block  438 . For example, the calibration start trigger  410  can be generated when control system  260  determines that a row unit has been used to plant a threshold number of acres, or that it has been used for a threshold amount of time. In another example, usage threshold  438  can be determined based on the soil type, so that if the soil is more likely to promote wear, then the trigger is generated earlier than if the soil is less likely to promote wear. The calibration start trigger can be generated based on a wide variety of other criteria that may indicate wear as well, and this is indicated by block  440 . 
     Once the calibration start trigger has been detected, then arm contact member positioning logic  420  positions the arm contact member (or mechanical stop)  150  for maximum planting depth. This is indicated by block  442 . One example of this is illustrated in the pictorial illustration shown in  FIG. 13A . It can be seen that arm contact member  150  has been moved to its position closest to bearing  182  (or to another known position along its extent of travel). It is also out of contact with gauge wheel arm  138 . This is indicated by block  444  in the flow diagram of  FIG. 12 . The arm contact member  150  can be positioned for maximum planting depth in other ways as well, and this is indicated by block  446 . 
     Next, the row unit  106  is lowered (and the entire planter can be lowered) to relatively flat ground. This is indicated by block  448 . In one example, the ground may be a firm surface, such as concrete, so that neither gauge wheel  116  nor opener  114  penetrate the ground. This is indicated by block  450 . It is also controlled so that both gauge wheels  116  and opener  114  are in contact with the ground as indicated by block  452 . This ensures that the lower portions of openers  114  and gauge wheels  116  are generally coplanar, in a horizontal plane, generally defined by the ground surface  454 . This is also indicated by block  456  and can be detected automatically or through observation as indicated by block  457  in the flow diagram of  FIG. 12 . 
       FIG. 13A  also shows that, in one example, gauge wheel arms  148  include a sensor target  458 , along with a distance sensor  460  (which may be an inductive sensor, or another sensor) that measures the distance to target  458 . Target  458  is tapered so that, as gauge wheel arm  148  pivots about pivot point  156 , the distance between sensor  460  and target  458  changes approximately linearly (or in another known relationship) with the change of the gauge wheel angle. 
     Returning again to the flow diagram of  FIG. 12 , once the row unit  106  is lowered onto the relatively flat ground, then the arm contact member position detection logic  426  measures the gauge wheel position using position sensor  460  and target  458 , or another sensor. This is indicated by block  462  in the flow diagram of  FIG. 12 . In one example, the measurement is taken for both gauge wheels in a pair of gauge wheels, as indicated by block  464 . The measurement can be made in other ways as well, and this is indicated by block  466 . 
     Arm contact member positioning logic  420  then generates a control signal and provides it to control signal generator logic  294  to actuate the motor to move the mechanical stop (or arm contact member)  150  in a direction to decrease planting depth. Referring again to  FIG. 13A , this will cause mechanical stop  150  to move more towards bearing  184 . Actuating the motor to move mechanical stop  150  in this direction is indicated by block  468  in the flow diagram of  FIG. 12 . While this is happening, motor revolution tracking logic  424  tracks the number of revolutions of the motor, as it is moving mechanical stop  150 . Tracking the motor revolutions is indicated by block  470 . 
     This continues until motor torque sensing logic  422  senses that mechanical stop  150  has come into contact with gauge wheel arm  148 , as is illustrated in the pictorial diagram shown in  FIG. 13B . In one example, when this occurs, the torque output by the motor turning lead screw  180  will increase, and this will be indicated by motor torque signal  412 . When this occurs, arm contact member positioning logic  420  outputs a signal to control signal generator logic  294  so that it stops rotation of the motor. Determining that mechanical stop  150  is in contact with the gauge wheel arm  148 , such as through an increase in motor torque or otherwise, is indicated by blocks  472 ,  474  and  476  in  FIG. 12 . Stopping the motor once mechanical stop  150  comes into contact with gauge wheel arm  148  is indicated by block  478 . 
     Arm contact member position detection logic  426  then determines the position, along its extent of travel, of the arm contact member (or mechanical stop)  150 . This is indicated by block  480  in the flow diagram of  FIG. 12 . This can be done in a variety of different ways. For instance, using the number of revolutions of the motor, as indicated by block  482  that were required to move mechanical stop  150  from the position shown in  FIG. 13A  to the position shown in  FIG. 13B , along with the gear ratio of any gear box that is deployed between the motor drive shaft and lead screw  180  (as indicated by block  484 ), along with the pitch of the screw on lead screw  180  (as indicated by block  486 ), logic  426  can identify how far mechanical stop  150  has moved through its extent of motion along lead screw  180 . The position along its extent of travel can be identified in other ways as well, and this is indicated by block  488 . 
     Once this position is known, calibration point identifier logic  428  illustratively identifies this as a zero point on the calibration curve, where gauge wheel  116  and opener  114  are at the exact same height so the corresponding planting depth would be zero. Control curve adjustment logic  430  then adjusts the control curve based upon the identified calibration zero point. This is indicated by block  490  in the flow diagram of  FIG. 12 . Identifying this calibration point as a zero point on the control curve is indicated by block  492 . It illustratively shifts the control curve based on the new zero point, and this is indicated by block  494 . It can adjust the control curve to accommodate for wear or other changes in the kinematics of the system in other ways as well, and this is indicated by block  496 . 
     Wear calculation logic  431  then illustratively calculates the wear on the opener and gauge wheels. This is indicated by block  498 . In one example, where a gauge wheel position sensor  460  is used, and where arm contact member position detection logic  426  is also used (which calculates the position of mechanical stop  150  based upon the revolutions of the motor and the gear ratio and screw pitch), then wear calculation logic  431  can calculate the wear on both the gauge wheel  116  and on the opener  114 . However, where only one of those position sensors is used, then the combined wear of both the opener  114  and gauge wheel  116  can be calculated. Calculating combined wear is indicated by block  500  and calculating separate gauge wheel and opener wear is indicated by block  502 . 
     Wear calculation logic  431  then outputs and indication of the wear on the gauge wheels  116 , and the opener  114 , and this is indicated by block  504 . It can be output to a storage component as indicated by block  506 , where it can be accessed at any time. It can also be displayed to the operator as indicated by block  508 . In one example, wear calculation logic  431  compares the calculated wear to a wear threshold to determine whether replacement of gauge wheels  116  or opener  114  is needed. This is indicated by block  510 . If so, that can be brought to the operator&#39;s attention (or another&#39;s attention) through an alert message, or another type of output mechanism. Outputting the wear can be done in other ways as well, and this is indicated by block  512 . 
     As discussed above, planting depth calibration system  295  can perform either single point calibration (where a single calibration point is identified, as discussed above with respect to  FIG. 12 ) or it can perform a multi-point calibration where multiple calibration points can be identified and used to adjust the calibration curve. If multi-point calibration is to be performed, as indicated by block  514 , then, in one example, a calibration element (illustrated by element  516  in  FIGS. 13C and 13D ), is placed between the ground and the gauge wheels  114 , while allowing opener  114  to remain in contact with the ground. In one example, the calibration element  516  has a known height. This is indicated by block  518  in the flow diagram of  FIG. 12 . Keeping the opener  114  in contact with the ground is indicated by block  520 . The calibration element  516  can be placed under the gauge wheels on a single row unit  106 , or under all gauge wheels, of all row units  106  on a planter. The calibration element can be placed between the ground and the gauge wheels in other ways as well, and this is indicated by block  522 . 
     Planting depth calibration system  295  then performs the motor actuations to the move the arm contact member  150  from one end of travel to contact the gauge wheel arms  148  in order to identify another calibration point on the control curve. This is indicated by block  524  in the flow diagram of  FIG. 12 , and it is described in greater detail above with respect to  FIGS. 13A and 13B . It is also shown in more detail in  FIG. 13C  and  FIG. 13D . For instance,  FIG. 13C  shows that arm contact member  150  is in its furthest extent of travel toward bearing  182 .  FIG. 13D  shows that arm contact member  150  has now been moved until it comes into engagement with gauge wheel arm  148 . Again, this can be sensed based on an increase in torque at the output of the motor driving lead screw  180 , or in other ways. 
     Once the distance traveled by member  150  has been identified (based on the rotations of the motor, any gear ratio, the pitch of lead screw  180 , etc.), then this, in combination with the known offset between opener  114  and gauge wheels  116  (based on the known height of calibration element  516 ), can be used to identify another calibration point. Calibration point identifier logic  428  identifies that calibration point, and control curve adjustment logic  430  adjusts the control curve again, based upon the newly identified calibration point. Adjusting the control curve based on the additional calibration point is indicated by block  526  in the flow diagram of  FIG. 12 . 
     If additional calibration elements  516 , that have different, known heights are provided, then the same process can be repeated to identify still more calibration points that can be used to adjust the calibration curve. If more calibration points are to be identified, as indicated by block  528  in the flow diagram of  FIG. 12 , the processing reverts to block  518 . 
     If not, however, then the planting depth control system  578  illustratively controls the planting depth actuator assembly  154  using the adjusted control curve  416 . This is indicated by block  530  in the flow diagram of  FIG. 12 . 
     The present discussion has mentioned processors and servers. In one embodiment, the processors and servers include computer processors with associated memory and timing circuitry, not separately shown. They are functional parts of the systems or devices to which they belong and are activated by, and facilitate the functionality of the other components or items in those systems. 
     Also, a number of user interface displays have been discussed. They can take a wide variety of different forms and can have a wide variety of different user actuatable input mechanisms disposed thereon. For instance, the user actuatable input mechanisms can be text boxes, check boxes, icons, links, drop-down menus, search boxes, etc. They can also be actuated in a wide variety of different ways. For instance, they can be actuated using a point and click device (such as a track ball or mouse). They can be actuated using hardware buttons, switches, a joystick or keyboard, thumb switches or thumb pads, etc. They can also be actuated using a virtual keyboard or other virtual actuators. In addition, where the screen on which they are displayed is a touch sensitive screen, they can be actuated using touch gestures. Also, where the device that displays them has speech recognition components, they can be actuated using speech commands. 
     A number of data stores have also been discussed. It will be noted they can each be broken into multiple data stores. All can be local to the systems accessing them, all can be remote, or some can be local while others are remote. All of these configurations are contemplated herein. 
     Also, the figures show a number of blocks with functionality ascribed to each block. It will be noted that fewer blocks can be used so the functionality is performed by fewer components. Also, more blocks can be used with the functionality distributed among more components. 
     It will also be noted that the elements of  FIGS. 8 and 9 , or portions of them, can be disposed on a wide variety of different devices. Some of those devices include servers, desktop computers, laptop computers, tablet computers, or other mobile devices, such as palm top computers, cell phones, smart phones, multimedia players, personal digital assistants, etc. 
       FIG. 14  is one example of a computing environment in which elements of  FIGS. 8-9 , or parts of them, (for example) can be deployed. With reference to  FIG. 14 , an example system for implementing some embodiments includes a general-purpose computing device in the form of a computer  810 . Components of computer  810  may include, but are not limited to, a processing unit  820  (which can comprise processors or servers shown in previous FIGS.), a system memory  830 , and a system bus  821  that couples various system components including the system memory to the processing unit  820 . The system bus  821  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. Memory and programs described with respect to  FIGS. 8-9  can be deployed in corresponding portions of  FIG. 14 . 
     Computer  810  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  810  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media is different from, and does not include, a modulated data signal or carrier wave. It includes hardware storage media including both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD) or other optical disc storage, magnetic cassettes, magnetic tape, magnetic disc storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computer  810 . Communication media may embody computer readable instructions, data structures, program modules or other data in a transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. 
     The system memory  830  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  831  and random access memory (RAM)  832 . A basic input/output system  833  (BIOS), containing the basic routines that help to transfer information between elements within computer  810 , such as during start-up, is typically stored in ROM  831 . RAM  832  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  820 . By way of example, and not limitation,  FIG. 14  illustrates operating system  834 , application programs  835 , other program modules  836 , and program data  837 . 
     The computer  810  may also include other removable/non-removable volatile/nonvolatile computer storage media. By way of example only,  FIG. 14  illustrates a hard disc drive  841  that reads from or writes to non-removable, nonvolatile magnetic media, an optical disc drive  855 , and nonvolatile optical disc  856 . The hard disc drive  841  is typically connected to the system bus  821  through a non-removable memory interface such as interface  840 , and optical disc drive  855  are typically connected to the system bus  821  by a removable memory interface, such as interface  850 . 
     Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (e.g., ASICs), Application-specific Standard Products (e.g., ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc. 
     The drives and their associated computer storage media discussed above and illustrated in  FIG. 14 , provide storage of computer readable instructions, data structures, program modules and other data for the computer  810 . In  FIG. 14 , for example, hard disc drive  841  is illustrated as storing operating system  844 , application programs  845 , other program modules  846 , and program data  847 . Note that these components can either be the same as or different from operating system  834 , application programs  835 , other program modules  836 , and program data  837 . 
     A user may enter commands and information into the computer  810  through input devices such as a keyboard  862 , a microphone  863 , and a pointing device  861 , such as a mouse, trackball or touch pad. Other input devices (not shown) may include a joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  820  through a user input interface  860  that is coupled to the system bus, but may be connected by other interface and bus structures. A visual display  891  or other type of display device is also connected to the system bus  821  via an interface, such as a video interface  890 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  897  and printer  896 , which may be connected through an output peripheral interface  895 . 
     The computer  810  is operated in a networked environment using logical connections (such as a local area network—LAN, or wide area network WAN, a controller area network CAN) to one or more remote computers, such as a remote computer  880 . 
     When used in a LAN networking environment, the computer  810  is connected to the LAN  871  through a network interface or adapter  870 . When used in a WAN networking environment, the computer  810  typically includes a modem  872  or other means for establishing communications over the WAN  873 , such as the Internet. In a networked environment, program modules may be stored in a remote memory storage device.  FIG. 14  illustrates, for example, that remote application programs  885  can reside on remote computer  880 . 
     It should also be noted that the different embodiments described herein can be combined in different ways. That is, parts of one or more embodiments can be combined with parts of one or more other embodiments. All of this is contemplated herein. 
     Example 1 is a method of controlling a planting depth actuator, comprising:
         controlling the planting depth actuator to position an arm contact member, that moves along an axis of movement through an extent of travel and that contacts a gauge wheel arm to change a relative position of a gauge wheel relative to an opener on a planter row unit, at a first known position along the extent of travel and out of contact with the gauge wheel arm;   detecting that the row unit is positioned so the gauge wheel and the opener are in a known position relative to one another;   controlling the planting depth actuator to move the arm contact member from the first known position to a second position in which the arm contact member is in contact with the gauge wheel arm;   identifying how far the arm contact member moved along the extent of travel from the first, known position to the second position, to identify the second position as a first calibration point; and   adjusting a control curve, used to position the arm contact member to control planting depth of the row unit, based on the first calibration point.       

     Example 2 is the method of any or all previous examples wherein controlling the planting depth actuator to position the arm contact member at the first, known position, comprises:
         controlling the planting depth actuator to move the arm contact member to a first end of the extent of travel.       

     Example 3 is the method of any or all previous examples and further comprising:
         detecting when the arm contact member is in contact with the gauge wheel arm.       

     Example 4 is the method of any or all previous examples wherein detecting when the arm contact member is in contact with the gauge wheel arm comprises:
         detecting an increase in torque output by the planting depth actuator.       

     Example 5 is the method of any or all previous examples wherein the planting depth actuator comprises a motor with a rotatable output shaft that drives rotation of a lead screw that rotates to drive the arm contact member along the axis of movement and wherein controlling the planting depth actuator to move the arm contact member from the first known position to the second position, comprises:
         controlling the motor to rotate the rotatable output shaft.       

     Example 6 is the method of any or all previous examples wherein identifying how far the arm contact member moved comprises:
         counting a number of rotations of the rotatable output shaft and identifying how far the arm contact member moved based on the number of rotations and a pitch of the lead screw.       

     Example 7 is the method of any or all previous examples wherein the rotatable out shaft is coupled to the lead screw through a gear mechanism having a gear ratio and wherein identifying how far the arm contact member moved comprises:
         counting the number of rotations of the rotatable output shaft and identifying how far the arm contact member moved based on the number of rotations and the pitch of the lead screw and the gear ratio.       

     Example 8 is the method of any or all previous examples and further comprising:
         identifying wear of the opener and the gauge wheel based on the first calibration point.       

     Example 9 is the method of any or all previous examples and further comprising:
         sensing a position of the gauge wheel and wherein identifying wear comprises identifying wear of the opener and the gauge wheel, separately, based on the position of the gauge wheel and the first calibration point.       

     Example 10 is a planting depth control system, comprising:
         control signal generator logic that generates control signals to control an actuator to position an arm contact member along an axis of movement through an extent of travel and that contacts a gauge wheel arm to change a relative position of a gauge wheel relative to an opener on a planter row unit;   a position detector detecting that the row unit is positioned so the gauge wheel and the opener are in a known position relative to one another;   arm contact member positioning logic that generates a position output to the control signal generator logic to position the arm contact member at a first known position along the extent of travel and out of contact with the gauge wheel arm and to move the arm contact member from the first known position to a second position in which the arm contact member is in contact with the gauge wheel arm;   a planting depth calibration system that identifies how far the arm contact member moved along the extent of travel from the first, known position to the second position, to identify the second position as a first calibration point; and   control curve adjustment logic that adjusts a control curve, used to position the arm contact member to control planting depth of the row unit, based on the first calibration point.       

     Example 11 is the planting depth control system of any or all previous examples wherein the arm contact member position logic is configured to control the actuator to position the arm contact member at the first, known position, buy controlling the actuator to move the arm contact member to a first end of the extent of travel. 
     Example 12 is the planting depth control system of any or all previous examples and further comprising:
         a first position detector configured to detect when the arm contact member is in contact with the gauge wheel arm.       

     Example 13 is the planting depth control system of any or all previous examples wherein the first position detector comprises:
         motor torque sensing logic detecting an increase in torque output by the actuator.       

     Example 14 is the planting depth control system of any or all previous examples wherein the actuator comprises a motor with a rotatable output shaft that drives rotation of a lead screw that rotates to drive the arm contact member along the axis of movement and wherein the planting depth calibration system, comprises:
         motor revolution tracking logic configured to track a number of revolutions of the rotatable output shaft; and   arm contact member position detection logic identifying how far the arm contact member moved based on the number of revolutions and a pitch of the lead screw.       

     Example 15 is the planting depth control system of any or all previous examples wherein the rotatable out shaft is coupled to the lead screw through a gear mechanism having a gear ratio and wherein the arm contact member positioning logic is configured to identify how far the arm contact member moved based on the number of revolutions and the pitch of the lead screw and the gear ratio. 
     Example 16 is the planting depth control system of any or all previous examples and further comprising:
         wear identifying logic configured to identify wear of the opener and the gauge wheel based on the first calibration point.       

     Example 17 is the planting depth control system of any or all previous examples and further comprising:
         a gauge wheel position sensor sensing a position of the gauge wheel and wherein the wear identifying logic identifies wear of the opener and the gauge wheel, separately, based on the position of the gauge wheel and the first calibration point.       

     Example 18 is a method of controlling a planting depth actuator, comprising:
         controlling the planting depth actuator to position an arm contact member, that moves along an axis of movement through an extent of travel and that contacts a gauge wheel arm to change a relative position of a gauge wheel relative to an opener on a planter row unit, at a first end position along the extent of travel and out of contact with the gauge wheel arm;   detecting that the row unit is positioned so a lowest position of the gauge wheel and a lowest position of the opener are in a known position relative to one another;   controlling the planting depth actuator to move the arm contact member from the first end position to a second position in which the arm contact member is in contact with the gauge wheel arm;   identifying how far the arm contact member moved along the extent of travel from the first end position to the second position, to identify the second position as a first calibration point; and   adjusting a control curve, used to position the arm contact member to control planting depth of the row unit, based on the first calibration point.       

     Example 19 is the method of any or all previous examples wherein the actuator comprises a motor with a rotatable output shaft that drives rotation of a lead screw that rotates to drive the arm contact member along the axis of movement and wherein controlling the actuator to move the arm contact member from the first known position to the second position comprises controlling the motor to rotate the rotatable output shaft and wherein identifying how far the arm contact member moved comprises:
         counting a number of rotations of the rotatable output shaft and identifying how far the arm contact member moved based on the number of rotations and a pitch of the lead screw.       

     Example 20 is the method of any or all previous examples and further comprising:
         sensing a position of the gauge wheel; and identifying wear of the opener and the gauge wheel, separately, based on the position of the gauge wheel and the first calibration point.       

     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.