Determining a ground speed of a machine

The disclosure describes, in one aspect, a method for determining a machine ground speed. The method includes determining a machine speed from a position determining system, the machine speed includes a horizontal speed component and a vertical speed component, determining a direction the machine is moving at the machine speed, determining a machine inclination angle, determining a machine rate of inclination, and determining a compensated ground speed as a function of the horizontal speed component, the vertical speed component, the direction, the machine inclination angle, and the machine rate of inclination.

TECHNICAL FIELD

This patent disclosure relates generally to a control system, and more particularly to systems and methods for a control system adapted to determine and use a ground speed of a machine.

BACKGROUND

Earthmoving machines such as track type tractors, motor graders, scrapers, and/or backhoe loaders, have an implement such as a dozer blade or bucket, which is used on a worksite in order to alter a geography or terrain of a section of earth. The machine and/or the implement may be controlled by an operator or by a control system to perform work on the worksite such as achieving a final surface contour or a final grade on the worksite. Positioning the implement, however, is a complex and time-consuming task that requires expert skill and diligence if the operator is controlling the movement. Thus, it is often desirable to provide autonomous control of the machine and/or the implement to simplify operator control.

For autonomous control, it is sometimes necessary to determine the accurate ground speed of the machine to compare against a desired ground speed value for the control systems. Some machines use ground penetrating radar (GPR) and other ground based position systems to determine the ground speed. GPR components, however, are prone to failure, which may introduce errors in the ground speed determination and are often easily covered with dirt, which an operator must get out of machine, crawl under it, and remove the debris from the mounted radar. Further, radar components due to location can be damaged by rocks.

For example, U.S. Pat. No. 5,8640,480 to Jayaraman et al. (“Jayaraman”) disclose a method for determining pitch and ground speed of an earth moving machine. Jayaraman discloses an automatic control system that includes a ground speed sensor that senses the ground speed of the earth moving machine and responsively produces a ground speed signal. Jayaraman teaches that the ground speed sensor is suitably positioned on the bulldozer and includes for example, a non-contacting ultrasonic or Doppler radar type sensor.

The disclosed systems and methods are directed to overcoming one or more of the problems set forth above.

SUMMARY

In one aspect, the disclosure describes, a method for determining a machine ground speed. The method includes determining a machine speed from a position determining system, the machine speed includes a horizontal speed component and a vertical speed component, determining a direction the machine is moving at the machine speed, determining a machine inclination angle, determining a machine rate of inclination, and determining a compensated ground speed as a function of the horizontal speed component, the vertical speed component, the direction, the machine inclination angle, and the machine rate of inclination.

DETAILED DESCRIPTION

This disclosure relates to systems and methods for determining a ground speed of a machine. An exemplary embodiment of a machine100is shown schematically inFIG. 1. The machine100may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, the machine100may be a track-type tractor or dozer, as depicted inFIG. 1, a scraper, or any other machine known in the art. While the following exemplary embodiments are described in connection with a dozer, it should be appreciated that the description applies equally to the use of the embodiments in other machines.

In an illustrated embodiment, the machine100includes a power source102, an operator's station or cab104containing controls necessary to operate the machine100, such as, for example, one or more input devices (not shown) for propelling the machine100and/or controlling other machine components. The machine100further includes an implement106, such as, for example, a blade, a bowl, a ripper, or a bucket for moving earth.

The one or more input devices may include one or more joysticks disposed within the cab104and may be adapted to receive input from an operator indicative of a desired movement of the implement106. The cab104may also include a user interface having a display for conveying information to the operator and may include a keyboard, touch screen, or any suitable mechanism for receiving input from the operator to control and/or operate the machine100, the implement106, and/or the other machine components.

The implement106may be adapted to engage, penetrate, or cut the surface of a worksite and may be further adapted to move the earth to accomplish a predetermined task. The worksite may include, for example, a mine site, a landfill, a quarry, a construction site, or any other type of worksite. Moving the earth may be associated with altering the geography at the worksite and may include, for example, a grading operation, a scraping operation, a leveling operation, a bulk material removal operation, or any other type of geography altering operation at the worksite.

The implement106may be moveable by one or more hydraulic mechanisms operatively connected to the input device in the cab104. The hydraulic mechanisms may include one or more hydraulic lift actuators108and one or more hydraulic tilt actuators110for moving the implement106in various positions, such as, for example, lifting the implement106up or lowering the implement106down, tilting the implement106left or right, or pitching the implement106forward or backward. In the illustrated embodiment, the machine100includes one hydraulic lift actuator108and one hydraulic tilt actuator110on each side of the implement106(only one side shown).

The power source102is an engine that provides power to ground engaging mechanisms112adapted to support, steer, and propel the machine100. The power source102may embody an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of combustion engine known in the art. It is contemplated that the power source102may alternatively embody a non-combustion source of power (not shown) such as, for example, a fuel cell, a power storage device, or another suitable source of power. The power source102may produce a mechanical or electrical power output that may be converted to hydraulic power for providing power to the machine100, the implement106, and to other machine100components.

The machine100further includes a frame or rigid body114disposed between the implement106and the ground engaging mechanisms112. A position determining system116adapted to receive and process position data or signals may be mounted to the rigid body114of the machine100. The position determining system116may be mounted to the fixed body114of the machine100at a reference position R, which may be representative of an absolute position of the position determining system116. In some embodiments, the position determining system116may be mounted on or proximate to the top of the cab104at a distance A relative to the bottom of the ground engaging mechanisms112and a distance B relative to the tip of the implement106. The position determining system116may be a global position satellite (GPS) system or GPS receiver118. The GPS system118, as is well known in the art, receives signals from a plurality of satellites and responsively determines a position of a receiver in a coordinate system relative to the worksite, that is, in a site coordinate system. The site coordinate system may be a Cartesian system having an x-coordinate, a y-coordinate, and a z-coordinate.

In addition to position data, the GPS system118may be adapted to process a corresponding speed of the receiver118. The corresponding speed may be used to determine the speed of travel of the machine100; in other words, the GPS system118may be adapted to determine the travel speed or ground speed of the machine100. In some embodiments, the GPS system118may determine a three-dimensional position, for example, latitude, longitude, and height, and may determine a three-dimensional speed, for example, northward, eastward, and vertical speeds.

In the illustrated embodiment, the GPS system118is adapted to provide a ground speed of the machine100that includes a horizontal velocity component and a vertical velocity component. The ground speed from the GPS system118may also include a magnitude that is determined by the square root of the sum of the squared horizontal and vertical velocity components. In alternative embodiments, the position determining system116may include other types of positioning systems mounted to the rigid body in a plurality of locations, such as, for example, inertial navigational systems (INSs), and may include a plurality of methods for determining a corresponding ground speed without departing from the scope of this disclosure.

The machine100may further include a control system120operatively connected to the input device and to the hydraulic actuators108,110for controlling, for example, movement of the implement106. In some embodiments, the control system120may be operatively connected to the input device and to other machine components for controlling other operations of the machine100, such as, for example, connected to the ground engaging mechanisms112for controlling a speed of the machine100. The control system120may direct the implement106to move to a predetermined or target position in response to an operators' desired movement of the implement106for engaging the implement106with the terrain of the worksite. The control system120may further direct the implement106to move to a predetermined or target position indicative of an automatically determined movement of the implement106, based in part on, for example, an engineering or site design, a map, a productivity or load maximizing measure, or a combination of site design and productivity measure.

For precise control, such as, for example, to direct the implement106to move precisely in response to an automatically determined movement signal or command, the control system120may require certain predetermined or acquired data associated with the machine100, such as, for example, the ground speed and/or the pitch of the machine100. The control system120may include one or more sensors122operatively connected to or associated with the machine100for determining certain operational characteristics of the machine100, such as, for example, an inclination or pitch rate sensor124for determining an angle, inclination, or pitch of the machine100and/or a rate of change associated with the angle, inclination, or pitch of the machine100.

A location position C of the inclination sensor124may be operatively related to or associated with the reference position R of the GPS system118. As shown inFIG. 1A, the reference position R of the GPS system118may be a linear distance L and an angular distance N from the inclination sensor124. The positional relationship between the GPS system118and the inclination sensor124may be calculated or determined using trigometric and/or geometric methods based on the angle N and the vertical P and horizontal M components of the distance L. The inclination sensor124may also be located proximate to a pitch center of the machine100, such as, for example, near a transmission case (not shown) of the machine100. In some embodiments, the one or more sensors122may be embodied as an inertial measurement unit (IMU) in an INS that measures linear and rotational degrees of freedom, such as, for example, pitch, yaw, and roll.

The control system120may be adapted to receive inputs from the input device, the position determining system116, and the sensors122,124. The control system120is further adapted to control or direct the movement of the implement106based at least in part on the inputs from the input device, the position determining system116, and the sensors122,124. It is contemplated that the one or more sensors122may in alternative embodiments include appropriate sensors adapted for determining roll rates and/or yaw rates to provide a three dimensional representation of the orientation of the machine100to determine ground speed in accordance with this disclosure.

The control system120may include one or more control modules (e.g. ECMs, ECUs, etc.). The one or more control modules may include processing units, memory, sensor interfaces, and/or control signal interfaces (for receiving and transmitting signals). The processing units may represent one or more logic and/or processing components used by the control system120to perform certain communications, control, and/or diagnostic functions. For example, the processing units may be adapted to execute routing information among devices within and/or external to the control system120.

Further, the processing units may be adapted to execute instructions, including from a storage device, such as memory. The one or more control modules may include a plurality of processing units, such as one or more general purpose processing units and or special purpose units (for example, ASICS, FPGAs, etc.). In certain embodiments, functionality of the processing unit may be embodied within an integrated microprocessor or microcontroller, including integrated CPU, memory, and one or more peripherals. The memory may represent one or more known systems capable of storing information, including, but not limited to, a random access memory (RAM), a read-only memory (ROM), magnetic and optical storage devices, disks, programmable, erasable components such as erasable programmable read-only memory (EPROM, EEPROM, etc.), and nonvolatile memory such as flash memory.

INDUSTRIAL APPLICABILITY

The industrial applicably of the systems and methods for determining a ground speed for the machine described herein will be readily appreciated from the foregoing discussion. Although the machine is shown as a track-type tractor, the machine may be any type of machine that performs at least one operation associated with, for example, mining, construction, and other industrial applications. Moreover, the systems and methods described herein can be adapted to a large variety of machines and tasks. For example, scrapers, backhoe loaders, skid steer loaders, wheel loaders, motor graders, and many other machines can benefit from the systems and methods described.

In accordance with certain embodiments,FIG. 2illustrates an exemplary embodiment of the control system120and the process of determining the ground speed of the machine100(200). The control system120is adapted to receive a speed associated with the machine100from the GPS system118(Step202). The GPS system118provides the speed of the machine100based in part on the speed at the GPS system118receiver mounted to the body114of the machine100. The control system120is adapted to receive direction information associated with the direction in which the machine100is traveling (204). The speed information received from the GPS system118may be filtered, such as, for example, using a weighted moving average (Step206).

In some embodiments, since the GPS system118is mounted to the body114of the machine100, which may be on or near the top of the cab104, the GPS system118receiver may be located at a significant distance away from the center of gravity of the machine100. This distance away from the center of gravity may introduce errors when the speed is determined by the GPS system118. The errors may be associated with or correlated with the pitch of the machine100. Thus, the control system120is adapted to receive a pitch rate from the one or more sensors122embodied as the inclination sensor124(Step208). In some embodiments, the pitch rate data or signal may be processed to eliminate noise and bias, such as, for example, using high pass and low pass filters.

Further, the distance the GPS system118is away from the center of gravity is a function of the size of the machine100. Consequently, the magnitude of the error when determining the speed may be proportionate to the distance the GPS system118is away from the center of gravity. The control system120is adapted to determine a machine dependent scale factor for adjusting the speed determined by the GPS system118as a function of the pitch rate (Step210). The factor may be determined from the following equation:

A pitch lever arm, or lever_arm in the above equation, which is essentially the distance L between the inclination sensor124and the GPS system118receiver, may approximate the distance the GPS system118is away from the center of gravity or the center of pitch. The above factor may be used to determine a scaled pitch rate compensation term, which is based in part on the size of machine100, to be used for addressing the errors introduced by the GPS system118as discussed above. The scaled pitch rate compensation term and the filtered speed are summed to provide a corrected ground speed (Step212). The control system120is adapted to receive the corrected ground speed and may use the corrected ground speed for more precise control, for example, of the implement106in response to an automatically determined movement signal or command. It is contemplated that the corrected ground speed may be used by the control system120to control other machine operations that require an accurate ground speed, such as, for example, to control the speed of the machine100.

In accordance with an alternative embodiment,FIG. 3illustrates an exemplary embodiment of the control system120and a process of determining a ground speed of the machine100when the ground speed includes a horizontal component and a vertical component (300). The control system120is configured to receive a horizontal ground speed component from the GPS system118(302). The control system120is further configured to receive a vertical speed component from the GPS system118(304). The control system120receives a direction signal or direction information (306). The direction information may be associated with a gear of a transmission (not shown) of the machine100.

The control system120is further configured to receive a pitch rate from the inclination sensor124(308). The signal received from the inclination sensor124indicative of the pitch rate may be processed for filtering and unit conversion and for mathematical or statistical processing by the control system120(310). The control system120is configured to determine a machine dependent scale factor as a function of the relative distance L between the inclination sensor124and the GPS system118(312). The pitch lever arm distance L is discussed in more detail above. The control system120scales or multiplies (314) the pitch rate (308) by the scale factor (312) to determine a scaled pitch rate compensation parameter (316).

The control system120is further configured to receive a pitch signal associated with the machine100(318). In some embodiments, the pitch signal (318) may be processed or filtered, such as, for example, using a Kalman filter or any another linear quadratic or other such filter. The control system120determines a pitch lever angle factor as a function of the relative angle N between the inclination sensor124and the GPS system118(320). The pitch signal (318) and the pitch lever angle factor (320) are summed (322) and processed for unit conversion (324) to determine a pitch angle compensation parameter (326).

The control system120multiplies the pitch rate compensation parameter (316) by the cosine of two times pi times the pitch angle compensation parameter (326) to determine or calculate a horizontal compensation parameter (328). The control system120multiplies the pitch rate compensation parameter (316) by the sine of two times pi times the pitch angle compensation parameter (326) to determine or calculate a vertical compensation parameter (330). The horizontal compensation parameter (328) is added to the horizontal speed component (302) to determine the compensated horizontal speed (332). The vertical compensation parameter (330) is added to the vertical speed component (304) to determine the compensated vertical speed (334).

The control system120determines or calculates a compensated ground speed (336) as a function of the compensated horizontal speed (332) and the compensated vertical speed (334). In some embodiments, a magnitude of the compensated ground speed (336) is calculated or determined by the square root of the sum of the squared horizontal (332) and vertical compensated (334) speeds. In some embodiments, the direction of movement of the machine100is associated with the compensated horizontal speed (332) before and/or after the magnitude of the compensated ground speed (336) is determined (338). In addition, or alternatively, the control system120may be configured to filter or process the compensated horizontal speed (332) and the compensated vertical speed (334) individually or to filter or process the magnitude of the compensated ground speed (336). The control system120is adapted to receive the compensated ground speed (336) and may use the compensated ground speed (336) for more precise control, for example, of the implement106in response to an automatically determined movement signal or command. It is contemplated that the compensated ground speed (336) may be used by the control system120to control other machine operations that require an accurate ground speed.