This disclosure relates generally to a system and method for controlling an implement on a machine. More specifically, the system includes a machine implement, a measurement sensor configured to provide an implement measurement signal indicative of a velocity of a machine implement, and a controller configured to receive the implement measurement signal, receive an operator command signal, and determine an adjusted operator command signal based on the implement measurement signal and the operator command signal.
Machines such as a tractors or bulldozers are equipped with attached implements for performing various tasks. For example, a tractor may be equipped with a blade for scraping the ground and pushing material. An operator can move the position of the blade up and down relative to the ground. This helps the tractor complete the task of properly leveling or contouring the ground on which the tractor is operating. This is a task often performed during the construction of roads, buildings, or other structures.
One difficulty facing a tractor is that the movement of the tractor over uneven terrain results in the blade pitching up or down as the tractor itself pitches up or down across the terrain. For example, if the tractor begins to climb over a bump, the front of the tractor will pitch up, resulting the tractor's blade also pitching up. The causes the blade to dig shallower than if the tractor were on level ground.
Conversely, if the front of the tractor pitches downward, the blade will also pitch downward. Unless the operator corrects for this movement, the pitching of the blade will result in the blade digging into the earth too deeply than is desired.
Operators of a tractor can correct for uneven terrain by adjusting the motion of the blade as the machine moves over uneven terrain. For example, if the operator perceives that the tractor is pitching or will pitch upward, the operator can command the blade to move downward to compensate for the tractor's movement, resulting in a smoother surface. However, the quality of the resulting grade is dependent on the skill of the operator in anticipating the need to adjust the blade. The operator may have to slow the speed of the machine in order to better adjust the blade in response to uneven terrain, which reduces the efficiency of the machine and may increase the cost of completing the work.
Systems and methods exist to automatically adjust the position of an implement, such as a blade on a tractor, to produce more uniform results. For example, systems may produce a map of the worksite with target finishes, which can be fed to sensors on the machine to automatically adjust the blade to produce a desired finish. These systems may produce desirable results, but may be very expensive. Also, the finished surface must often be defined accurately before work can begin, rather than allowing for adjustment that can be achieved as work at the site progresses. It is desirable to have a system that still produces a smoother finish than obtainable by operator adjustment alone, but does not require as much expensive equipment and control systems as in many prior art grading systems. The system should provide greater efficiency than no control on the machine.
U.S. Pat. No. 7,121,355 to Lumpkins et. al (“Lumpkins”) discloses a system for controlling the position of a machine blade for grading. In Lumpkins, a control system determines the difference between a target position of a blade and an actual position, and generates a control signal calculated to move the blade to the target position.
Although the system disclosed by Lumpkins purports to more accurately control the position of a blade, the Lumpkins system may not adequately compensate for the fact that the operator may be commanding the machine implement in anticipation of uneven terrain. The system disclosed by Lumpkins does not electronically attempt to discern a difference between when an operator is attempting to move the blade to a new target position, and when the operator is merely attempting to compensate for uneven terrain. Consequently, the Lumpkins system requires a separate lever that the operator controls, which alternately tells the system to return the blade to a target position, or tells the system that the operator is attempting to override the control system and move the blade to a new target position.
It is desirable to have a control system which is easier to operate, and which adjusts the implement rate of change on a machine in response to uneven terrain while recognizing that the operator may simultaneously be issuing implement commands which attempt to achieve the same intention as the control system. Moreover, it is desirable to have a machine implement control system that produces a smoother grade or contour without the necessity of knowing or calculating an actual target position for the implement.
The present disclosure is directed to overcoming or mitigating one or more of the problems set forth above.
In one aspect, a control system for a machine is disclosed. The control system includes a sensor configured to provide an implement measurement signal indicative of a velocity of a machine implement, and a controller configured to receive the implement measurement signal, receive an operator command signal, and determine an adjusted operator command signal based on the implement measurement signal and the operator command signal.
In another aspect, a method for adjusting a machine implement is disclosed. The method includes the steps of providing an implement measurement signal indicative of a velocity of the machine implement, and providing an operator command signal indicative of an operator-desired movement of the machine implement. The method also includes the steps of determining an adjusted operator command signal based on the implement measurement signal and the operator command signal, and commanding a change in the velocity of the machine implement based on the adjusted operator command signal.
In another aspect, an earth-moving machine includes a ground-engaging blade, and a measurement sensor mounted on the ground-engaging blade and configured to provide an implement measurement signal indicative of a velocity of the ground-engaging blade. The earth-moving machine also includes a controller configured to receive the implement measurement signal, receive an operator command signal indicative of an operator-desired movement of the ground-engaging blade, and determine an adjusted operator command signal based on the implement measurement signal and the operator command signal.
Tractor 10 includes a blade 18 pivotally connected to frame 12 by arms 20 (only one side shown) on each side of tractor 10. Hydraulic cylinders 22 coupled to frame 12 support blade 18 in the vertical direction, and allow blade 18 to pitch up or down vertically from the point of view of
Hydraulic cylinders 22, 24 are preferably electro-hydraulically controlled, receiving signals from a control module 26. Control module 26 generates a signal that is translated into a direction and magnitude of movement of the appropriate hydraulic cylinders 22, 24. As shown in
Control module 26 may be mounted at any convenient location on tractor 10. Tractor 10 may include more than one control module 26 to control various different functions and systems of tractor 10.
Control module 26 may include one or more of the following: a microprocessor, memory (e.g., RAM, ROM), data storage devices (e.g., optical media, memory, hard drives), sensor input circuits, system control circuits, and executable software. These components perform the functions of the control system disclosed herein and/or perform tasks related to other systems on tractor 10. One skilled in the art may choose a suitable combination of hardware and/or software components as appropriate for the machine.
Tractor 10 includes cab 28 from which an operator may control tractor 10. Cab 28 includes one or more controls from which the operator issues commands.
Joystick 30 may also be configured to control other aspects of blade 18, such as blade angle rate of change (e.g., actuating hydraulic cylinders 24). Preferably, joystick 30 operates as part of an electro-hydraulic control system on tractor 10 wherein the operator's movement of joystick 30 (including the magnitude of the movement of joystick 30) are translated into a signal and sent to control module 26. Thus, movement of joystick 30 generates a signal to control module 26 indicative of the magnitude and direction of the operator's movement of joystick 30. Control module 26 may process this signal and potentially adjust the signal prior to issuing a signal to hydraulic cylinders 22, 24 to adjust blade 18. This is further described below.
Tractor 10 is equipped with measurement sensor 32. Measurement sensor 32 is preferably mounted on blade 18, but may be mounted on arms 20 or frame 12. Measurement sensor 32 provides data that is indicative (directly or indirectly) of velocity of an implement such as blade 18. Measurement sensor 32 may be a pitch rate sensor (e.g., gyroscope), to measure the rate of change of the blade 18 as it rotates about an axis defined by a pivot connection 23 of blade 18 to frame 12 (e.g., the pivot connection of arms 20 to frame 12). The height of blade 18 relative to the machine centerline (shown in
Similarly, when tractor 10 pitches upwards or downwards, such as when traversing uneven terrain, blade 18 also pitches upwards or downwards. Thus, measurement sensor 32 may register an angular rotation signal proportional to the amount of movement (rotation around the mounting axis) of blade 18.
Alternatively, measurement sensor 32 may be an accelerometer. In this configuration, the accelerometer is preferably mounted to blade 18 or arms 20. In this embodiment, the accelerometer may provide a signal indicative of the acceleration and/or velocity of blade 18.
Tractor 10 may be equipped with a user switch (not shown) to activate or de-activate the electronic control system that uses measurement sensor 32. If the control system is de-activated, then tractor 10 will ignore the signal generated by measurement sensor 32. In this case, blade 18 will move according to the operator's commands and will not be otherwise adjusted for pitching of tractor 10.
If the control system is activated,
Signal 204 is an “implement measurement signal,” used herein to denote a signal representing an amount of blade 18 rotation command required to counteract the motion of blade 18 as registered by measurement sensor 32. For example, if tractor 10 is pitching up, measurement sensor 32 may measure that blade 18 is moving upwards. Control module 26 will calculate the signal required to send to hydraulic cylinders 22, 24 to counteract the movement of blade 18, which is represented by signal 204. Signal 204 may be converted to a “normalized” signal at converter 206 to produce signal 207. In other words, if signal 206 represents an implement velocity command in degrees per second, this signal may be converted to represent an equivalent percent command of the operatory joystick. Signal 207 thus represents the controller-calculated signal, represented in terms of a hypothetical operator joystick movement that would need to be issued to counteract the movement of blade 18.
Control module 26 compares signal 202 and signal 207 and produces an adjusted operator command signal 210 based at least in part on signal 202 and/or signal 207. The process of combining signal 202 and signal 207 is represented by combination circuit 208. The methodology of comparing and combining signal 202 and signal 207 to produce adjusted operator command signal 210 is described in detail below, specifically with respect to
It should be noted that the combination method shown in
b shows the extension length (in mm) of a hydraulic cylinder controlling blade height versus time. The graph of
The present disclosure provides an advantageous systems and methods for controlling the implement on a machine, such as a blade on a tractor or a bucket on a loader. A machine implement can be controlled to produce a smoother implement motion while remaining intuitive to the operator and without employing more expensive control systems that require predefined data about conditions at the worksite.
In step 406, the control module on board the machine provides an operator command signal. In some embodiments, an operator command signal may be generated even when the operator has not commanded any implement movement (i.e., the joystick is in the neutral position). This may be helpful to verify to the electronic control module that no operator command is presently issued.
In step 408, the implement measurement signal of step 404, and the operator command signal of step 406 are compared and potentially combined to determine a new signal, an “adjusted operator command signal,” that directs the desired movement of the implement. In step 410, the machine implement velocity is adjusted, preferably whereby signal 408 actuates an electro-hydraulic control system to adjust the velocity of the machine implement. The implement velocity may be adjusted to counteract all velocity of the blade, or alternatively the implement velocity may be adjusted to set a substantially constant target rate of change of machine implement velocity, for applications such as grading. In reviewing method 400 in
In the first step, step 502, an implement measurement signal is input to a controller on the machine containing the control system. In step 504, the implement control system is disabled. This may be the default condition when the machine is powered on, until the controller determines that one or more threshold conditions are satisfied prior to activating the implement control system. In this situation, the controller might receive an implement measurement signal but ignore this signal until the threshold activation conditions are met.
In step 506, the controller determines whether main threshold conditions are met in order to activate the control system. For example, the machine may contain an operator switch to indicate whether the operator of the machine wishes to activate the implement control system. One threshold condition may thus be whether a switch is in an “on” position, or similar indication is given by the operator to turn on the control system. In addition, the machine might have an implement lock switch or other device designed to stop the implement from moving. A threshold condition prior to starting the control system may be that an implement lock is not in place.
Another main threshold condition may be that the machine transmission is in a certain state (e.g., not in neutral). Still another example threshold condition may be that the machine ground speed is above a threshold amount (for example, above zero), or that the engine RPM is within a certain range. Still another threshold condition may be that one or more other control systems are not active and controlling the implement. This type of condition is desirable if the machine is equipped with multiple different implement control systems that are mutually exclusive and that cannot operate together.
If the main threshold conditions are not met in step 506, the implement control system is not activated, and the machine system returned to an earlier step (e.g., step 502) until the main threshold conditions are met.
If the main threshold conditions are met in step 506, the controller may proceed to determine whether any secondary threshold conditions are met before activating the implement control system, step 508. For example, the controller may examine whether the machine ground speed is below a maximum allowable speed for the implement control system. The controller may also determine whether the machine steering is below a maximum turn rate, to turn off the implement control system during large turns. The controller may also check whether the implement is in a float configuration.
The controller may also check whether the operator is commanding a very large movement of the implement, above a threshold value. For example, if the operator is giving a command to raise the implement by a large magnitude (e.g., the operator is attempting to raise the implement over an obstacle), the controller may de-activate the implement control system (or prevent the control system from initially activating) and not attempt to mitigate the operator-commanded implement movement. Thus, another secondary threshold condition may be that the operator's command to move the implement is below a threshold magnitude.
For steps 506 and 508, the controller may optionally also determine whether the main and/or secondary threshold conditions are met for a predetermined amount of time before activating the implement control system. For example, the controller may ensure that the machine speed is above a threshold speed for a predetermined amount of time (e.g., 80 milliseconds) before considering the threshold condition satisfied. The predetermined amount of time may apply to one, some, or all threshold conditions prior to activating the implement control system. In addition, the controller may have different predetermined time thresholds for different threshold conditions. For example, the controller may ensure that the machine speed is above a threshold speed for at least 80 milliseconds and that the machine steering is below a maximum threshold for 2 seconds prior to activating the implement control system.
If the main and secondary threshold conditions are met, then the implement control system is initialized, step 510. The system begins to interpret the implement measurement signal. This may include employing a low pass filter to eliminate sensor noise, and/or a high pass filter to reduce any steady-state offsets due to temperature variation, unbalanced noise, and/or other common causes of signal deviation known to those of skill in the art.
In the next step, step 512, the controller checks to see if the sensor input signal falls in between a “zero” band for a specified amount of time. Essentially this tests whether the magnitude of the motion of the blade, as measured by the measurement sensor, is so small as to be considered zero by the controller. The controller may set a magnitude below which the motion of the implement is to be considered zero, and no automatic implement control signal is generated to counteract this minimal sensed motion of the implement. This strategy may help prevent undesirable “drift” of the implement when the measurement sensor registers a very small but mathematically non-zero implement motion. If the input signal is within the zero band, then the controller may re-attempt step 510 (and/or steps 506 and 508).
If the implement measurement signal is not in the “zero” band (i.e., is of a sufficiently large magnitude), the controller may compare the implement measurement signal to the magnitude and direction of the operator command signal (if any).
During the comparison, a number of different scenarios may result, as shown in
Another possible scenario, shown as Case #2 in
Case #3 in
Another potential scenario is shown in Case #4 in
One of skill in the art can appreciate that the numbers listed in
Returning to
Other embodiments, features, aspects, and principles of the disclosed examples will be apparent to those skilled in the art and may be implemented in various environments and systems.