阅读说明：本技术 用于追踪参考激光的系统和方法 (System and method for tracking a reference laser ) 是由 史蒂文·丹尼尔·麦凯恩 杰伊·基肖尔·纳金 埃莱娜·克鲁日科娃 唐纳·凯利 于 2020-02-03 设计创作，主要内容包括：一种用于保持照射在激光检测器组件上的激光的系统和方法,包括确定来自旋转激光发射器的激光照射在激光传感器上的位置。确定激光传感器沿激光检测器组件的杆的当前位置,并且基于激光照射在激光传感器上的位置和激光传感器的当前位置来确定激光传感器沿杆的新位置。然后将激光传感器移动到新位置。该系统和方法通过沿激光检测器组件的杆移动激光传感器来提供激光检测器组件的有效较长工作范围。惯性测量单元用于计算激光入射之间的时间段中的位置信息。(A system and method for maintaining laser light impinging on a laser detector assembly includes determining a location at which laser light from a rotating laser emitter impinges on a laser sensor. A current position of the laser sensor along the rod of the laser detector assembly is determined, and a new position of the laser sensor along the rod is determined based on the position of the laser impinging on the laser sensor and the current position of the laser sensor. The laser sensor is then moved to a new position. The system and method provide an effective longer working range of the laser detector assembly by moving the laser sensor along the stem of the laser detector assembly. The inertial measurement unit is used to calculate position information in the time period between laser incidence.)

1. A method, comprising:

determining a position on the laser sensor where laser light from the rotating laser transmitter impinges;

determining a current position of the laser sensor along the rod;

determining a new position of the laser sensor along the rod based on the position of the laser impinging on the laser sensor and the current position of the laser sensor; and

transmitting a command to an actuator to move the laser sensor to a new position.

2. The method of claim 1, further comprising:

calculating a command to the actuator based on the current position of the laser sensor and the new position of the laser sensor.

3. The method of claim 2, wherein determining the current position of the laser sensor further comprises:

receiving data from an inertial measurement unit, wherein determining the new position of the laser sensor is further based on the data from the inertial measurement unit.

4. The method of claim 3, wherein the data identifying the current position of the laser sensor along the rod and the data from the inertial measurement unit are filtered prior to determining the new position of the laser sensor.

5. The method of claim 1, wherein the actuator is configured to move the laser sensor vertically along the rod.

6. The method of claim 2, wherein the command is calculated further based on a current speed of the laser sensor.

7. An apparatus, comprising:

a memory storing computer program instructions; and

a processor communicatively coupled with the memory, the processor configured to execute computer program instructions that, when executed on the processor, cause the processor to perform operations comprising:

determining a position on the laser sensor where laser light from the rotating laser transmitter impinges;

determining a current position of the laser sensor along the rod;

determining a new position of the laser sensor along the rod based on the position of the laser impinging on the laser sensor and the current position of the laser sensor; and

transmitting a command to an actuator to move the laser sensor to a new position.

8. The apparatus of claim 7, the operations further comprising:

calculating a command to the actuator based on the current position of the laser sensor and the new position of the laser sensor.

9. The apparatus of claim 8, wherein determining the current position of the laser sensor further comprises:

receiving data from an inertial measurement unit, wherein determining the new position of the laser sensor is further based on the data from the inertial measurement unit.

10. The apparatus of claim 9, wherein the data identifying the current position of the laser sensor along the rod and the data from the inertial measurement unit are filtered prior to determining the new position of the laser sensor.

11. The apparatus of claim 7, wherein the actuator is configured to move the laser sensor vertically along the rod.

12. The apparatus of claim 8, wherein the command is calculated further based on a current speed of the laser sensor.

13. A computer readable medium storing computer program instructions that, when executed on a processor, cause the processor to perform operations comprising:

determining a position on the laser sensor where laser light from the rotating laser transmitter impinges;

determining a current position of the laser sensor along the rod;

determining a new position of the laser sensor along the rod based on the position of the laser impinging on the laser sensor and the current position of the laser sensor; and

transmitting a command to an actuator to move the laser sensor to a new position.

14. The computer-readable medium of claim 13, the operations further comprising:

calculating a command to the actuator based on the current position of the laser sensor and the new position of the laser sensor.

15. The computer-readable medium of claim 14, wherein determining the current position of the laser sensor further comprises:

receiving data from an inertial measurement unit, wherein determining the new position of the laser sensor is further based on the data from the inertial measurement unit.

16. The computer readable medium of claim 15, wherein the data identifying the current position of the laser sensor along the rod and the data from the inertial measurement unit are filtered prior to determining the new position of the laser sensor.

17. A laser detector assembly comprising:

a rod;

a laser sensor movable along the rod and configured to detect laser output from a rotating laser emitter;

an actuator to move the laser sensor along the rod;

a laser sensor position sensor; and

a controller in communication with the laser sensor, the laser sensor position sensor, and the actuator, the controller configured to actuate the actuator so as to maintain the laser output from the rotary laser emitter within an operating range of the laser detector assembly.

18. The laser detector assembly of claim 17, wherein the actuator is actuated based on data from the laser sensor and the laser sensor position sensor.

19. The laser detector assembly of claim 18, further comprising:

an inertial measurement unit attached to the rod and in communication with the controller,

wherein the actuator is further actuated based on data from the inertial measurement unit.

20. The laser detector assembly as claimed in claim 18, wherein the laser sensor comprises a plurality of laser detector elements and data from the laser sensor identifies one of the plurality of laser detector elements that the laser is illuminating.

Technical Field

The present invention relates generally to machine control and operation, and more particularly to tracking reference lasers.

Background

Machines used for construction may use a rotary laser system to determine the elevation (e.g., height relative to a reference) of the machine and/or implement of the machine. Fig. 1A depicts a rotary laser system that includes a laser emitter 140 that outputs a laser beam 128 (also referred to as a "laser"), which rotates about a vertical axis of the laser emitter 140. The mirrors, optical components, and/or mechanical components of the laser transmitter rotate the laser in a laser reference plane having a known elevation 132. The laser detector 112 is attached to a rod 114. The laser detector 112 detects the laser beam 128 as it illuminates one of the plurality of laser detector elements (116 shown in fig. 1B and 1C) of the laser detector 112, as is well known in the art. The laser detector element may be a photoreceptor, a photodiode, or other type of sensor that can detect the laser beam 128. The pole 114 is attached to an implement 120 of a machine 110, such as a bulldozer shown in FIG. 1A. The elevation of the laser detector 112 is determined relative to the laser 128, and the elevation of the implement of the machine may be determined based on the elevation of the laser detector 112, since the distance from the implement 120 to the laser detector 112 is known.

Machine controlled laser receivers typically have a fixed working range, which is typically 150mm to 250 mm. The working range of the laser detector is such that the vertical length within the laser beam can be detected. In prior art systems, the operating range of the laser detector is based on the vertical length 118 along which the laser detector element 116 can detect the laser beam 128. As shown in fig. 1B, the vertical length 118 of the laser detector 112 is fixed. The equipment operator must position laser detector 112 so that laser beam 128 illuminates one of the plurality of laser detector elements 116 in order to establish grade elevation prior to use. The laser detector 112 is movably attached to the rod 114, which allows the operator to move the laser detector vertically along the rod 114. Since the laser beam 128 is not visible to the naked eye, the operator must manually search for the rotating laser beam 128 by moving the laser detector 112 vertically along the rod 114 until the laser detector 112 is in the path of the laser 128. Some manufacturers provide motorized rods to move the laser receiver into range via a remote control. While this is more convenient than manually locating the receiver, it still requires a significant amount of time and is inconvenient for locating the laser output from the transmitter.

FIG. 1C depicts a laser beam 128 illuminating one of a plurality of laser detector elements 116 located near a lower end of the laser detector 112. In this example, this occurs when the laser detector 112 has moved upward relative to the laser beam 128. Similarly, when the laser detector 112 has moved downward relative to the laser beam 128, one of the laser detector elements 116 located near the upper end of the laser detector 112 will detect the laser beam 128. As can be seen in fig. 1B and 1C, the laser beam 128 is only detected when the laser light 128 impinges on one of the plurality of laser detector elements 116. Thus, the working range of the laser detector 112 is limited by its length. If the laser detector 112 is moved up or down such that the laser beam 128 does not impinge on one of the laser detector elements 116, the elevation of the laser detector 112 cannot be determined. For example, if the laser detector 112 is moved upward (e.g., by the operator moving the implement 120 upward) such that the laser beam 128 no longer illuminates the laser detector 112, but instead illuminates the rod 114 or the implement 120, the elevation of the laser detector 112 cannot be determined. If the laser detector 112 is moved downward (e.g., by the operator moving the implement 120 downward) such that the laser beam 128 no longer illuminates the laser detector 112, but instead illuminates the cab of the machine 110 or travels without illuminating any portion of the machine 110, the elevation of the laser detector 112 cannot be determined.

Another typical characteristic of most machine-controlled laser detectors is that the output rate of the laser detector is directly related to the rate at which the laser illuminates the laser detector elements. A typical laser transmitter rotates the laser beam at 600rpm (10Hz) in the laser reference plane, which means that between each rotation a 100 ms switch is made, so the laser detector detects the laser at a rate of 10 Hz. Thus, the laser detector outputs information about the incidence of the laser light, in this example 10Hz, at the same rate that the laser light is detected. Movement of the laser detector between successive detections of laser light illuminating the laser detector is not detected.

What is needed is an easier and more efficient method and system for referencing laser tracking and providing elevation information at a faster rate and providing an effectively longer working range.

Disclosure of Invention

A system and method for maintaining a laser beam impinging on a laser detector assembly includes determining a location at which a laser beam from a rotating laser emitter impinges on a laser sensor. A current position of the laser sensor along the rod of the laser detector assembly is determined, and a new position of the laser sensor along the rod is determined based on the position at which the laser beam impinges on the laser sensor and the current position of the laser sensor. A command is then transmitted to the actuator to move the laser sensor to a new position. In one embodiment, the method includes calculating a command to the actuator based on the current position of the laser sensor and the new position of the laser sensor. In one embodiment, the command is calculated based on the current speed of the laser sensor. In one embodiment, determining the current position of the laser sensor further comprises receiving data from an inertial measurement unit and determining a new position based on the data from the inertial measurement unit. In one embodiment, the data from the laser sensor and the inertial measurement unit is filtered before determining the new position of the laser sensor.

In one embodiment, a laser detector assembly includes a rod, a laser sensor movable along the rod for detecting laser light, an actuator for moving the laser sensor, a laser sensor position sensor, and a controller. A controller is in communication with the laser sensor, the laser position sensor, and the actuator and is configured to actuate the actuator to maintain the laser within an operating range of the laser detector assembly. The actuator may be actuated based on data from the laser sensor and the laser sensor position sensor. The laser detector assembly may also include an inertial measurement unit, and the actuator may also be actuated based on data from the inertial measurement unit. The laser sensor may include a plurality of laser detector elements and data from the laser sensor may identify one of the laser detector elements that the laser is illuminating.

Drawings

FIG. 1A depicts a rotary laser system for determining elevation;

FIG. 1B depicts a laser detector in which a laser beam illuminates one of a plurality of laser detector elements;

FIG. 1C depicts the laser detector of FIG. 1B, wherein a laser beam illuminates another laser detector element of the plurality of laser detector elements;

FIG. 2 depicts a system for elevation control including a laser emitter and laser detector assembly according to an embodiment;

FIG. 3 depicts a laser detector assembly according to an embodiment;

FIG. 4 depicts a laser sensor according to an embodiment;

FIG. 5 depicts a stem of the laser detector assembly shown in FIG. 2, in accordance with an embodiment;

FIG. 6A depicts a flowchart of a method for detecting laser position and moving a laser detector along a rod according to an embodiment;

FIG. 6B depicts a flow chart of a method for looking up a laser beam output from a laser emitter;

FIG. 7 depicts different orientations of a machine implement having a laser detector assembly;

FIG. 8 depicts a flowchart of a method for detecting laser light incidence and outputting elevation data, in accordance with an embodiment; and

FIG. 9 depicts a schematic diagram showing measurements fused using a filter according to an embodiment.

Detailed Description

Fig. 2 depicts a laser emitter 140 that outputs a laser beam 128. In one embodiment, the laser transmitter 140 outputs a laser beam 128 that is rotated about a vertical axis to form the horizontal laser reference plane 130. In one embodiment, the elevation of laser transmitter 140 is known. Thus, the elevation 132 of the laser reference plane 130 is also known. Such rotating lasers are well known in the art.

The laser beam 128 is detected by a laser sensor 150 of the laser detector assembly 100, which in one embodiment includes the laser sensor 150, a stem 250, and a base 200 (described in detail below). The laser detector assembly 100 is mounted to an implement 120 of the machine 110, which in this example is the blade of a bulldozer. In one embodiment, the machine 110 is used to modify the surface according to a desired overall plan view based on data from the laser detector assembly 100.

Fig. 3 depicts details of the laser detector assembly 100 including the laser detector base 200. The rod 250 extends vertically from the laser detector base 200 and serves as a support for the laser sensor 150. The laser sensor 150 may be moved along the rod 250 by a motor 205 (also referred to as an actuator) connected to the shaft 220. In one embodiment, laser sensor 150 is approximately 100 millimeters in height and includes a plurality of laser detector elements 310 in a photodiode row or photodiode array. In other embodiments, the laser sensor may comprise other types of sensors and may have other heights, for example, heights ranging from 50 millimeters to 250 millimeters. In one embodiment, a laser sensor having a height of about 100 millimeters is movably located on a long rod to provide a longer detection range with a shorter laser sensor height, which makes its cost lower than using a tall laser sensor height. A toothed pulley 222 is attached to the shaft 220 and engages a toothed belt 215, which is connected to a carrier 260. The toothed belt 215 also engages an idler pulley 232 on the shaft 224 near the end of the rod 250. The idler pulley 232 and the toothed pulley 222 are separated by a distance necessary to maintain a desired tension of the toothed belt 215. In operation according to one embodiment, motor 205 rotates shaft 220 and toothed pulley 222, which moves toothed belt 215 along the length of rod 250. Movement of the toothed belt 215 causes the carrier 260 to move in either a first direction as indicated by arrow 151 or a second direction as indicated by arrow 152 along the length of the rod 250 based on the direction of rotation of the motor 205. The toothed pulleys and belts are used to maintain registration between the position of the carrier 260 and the position sensor 225 (described below).

The carrier 260 is attached to the toothed belt 215 and moves within the rod 250 in response to movement of the toothed belt 215. In one embodiment, the carrier 260 is cylindrically shaped and sized to fit within the shaft 250. The carrier 260 has a plurality of magnets 245 around its circumference that magnetically attract the magnets 246 of the laser sensor 150. As the carrier 260 moves along the length of the rod 250, the attractive force between the magnets 245 and 246 keeps the laser sensor 150 positioned adjacent to the carrier 260. In one embodiment, the carrier 260 is automatically moved to maintain the laser detector elements 310 in the field of view of the laser beam 128. For example, as shown in fig. 1C, laser light 128 is being detected by one of the plurality of laser detector elements 116 located near an end of the laser detector 112 due to upward movement of the implement 120 (e.g., caused by an operator moving the implement 120 or caused by the implement 120 moving upward as the machine 110 moves upward) and thus causing the laser detector 112 to move upward. If the laser detector 112 continues to move upward, the laser light 128 will no longer be detected by any of the plurality of laser detector elements 116. In the embodiment shown in fig. 3, the carrier 260 may be moved down the length of the rod 250 so as to impinge the laser beam 128 at a point near the vertical center of the laser sensor 150.

The shaft 220 is also attached to a position sensor 225, which senses the rotation of the shaft 220. Since the position and rotation of the shaft 220 is directly related to the linear movement of the toothed belt 215 and the carrier 260 is attached to the toothed belt 215, the position of the carrier 260 along the length of the rod 250 can be determined based on the position and rotation of the shaft 220 detected by the position sensor 225. The cogged pulley and cogged belt maintain registration between the position of the carrier 260 and the position sensor 225. Other arrangements may be used in place of the toothed pulley and belt arrangement to maintain registration between the position of the carrier 260 and the position sensor 225. In one embodiment, the position sensor 225 is a rotary encoder but may be other types of sensors for sensing rotation. Data from the position sensor 225 is transmitted to the computer 235.

It should be noted that the motor 205 is actuated and moves the carrier 260 along the length of the rod 250. However, other types of actuators may be used to move the carrier 260 along the length of the rod 250. For example, a hydraulic or pneumatic linear actuator may be used to move the carrier 260 along the length of the rod 250. Different types of actuators may require different types of sensors in order to determine the position of the carrier 260 along the length of the rod 250. In such embodiments, the particular sensor used to determine the position of the carrier 260 is selected based on the type of actuator used.

The computer 235 receives data from the various components of the laser detector assembly 100 and maintains the rotating laser beam 128 impinging on the laser sensor 150 and determines the elevation of the tool 120 relative to the laser reference plane 130. The computer 235 includes a processor 236 that controls the overall operation of the computer 235 by executing computer program instructions that define such operations. The computer program instructions may be stored in the storage device 238 or other computer-readable medium (e.g., diskette, CD ROM, etc.) and loaded into the memory 237 when execution of the computer program instructions is desired. Thus, the method steps of fig. 6A, 6B, 8 may be defined by computer program instructions stored in the memory 237 and/or storage device 238 and controlled by the processor 236 executing the computer program instructions. For example, the computer program instructions may be implemented as computer executable code programmed by one skilled in the art to implement the algorithms defined by the method steps of fig. 6A, 6B and 8. Thus, by executing the computer program instructions, the processor 236 executes the algorithm defined by the method steps of fig. 6A, 6B and 8. The computer 235 may also include one or more network interfaces (not shown) for communicating with other devices via a network, input/output devices (e.g., display, keyboard, mouse, speakers, buttons, etc.) that enable a user to interact with the computer 235, those skilled in the art will recognize that embodiments of a practical computer may also include other components, and that the computer 235 shown in FIG. 3 is a high-level representation of some of the components of such a computer for purposes of illustration.

An inertial measurement unit ("IMU") 230 is located in the laser detector base 200. IMU230 senses movement using one or more accelerometers (e.g., 3-axis accelerometers) and/or gyroscopes (e.g., 3-axis gyroscopes). In one embodiment, the laser detector base 200 is attached to the implement 120 of the machine 110. Thus, the IMU detects movement of the implement 120, regardless of how the implement 120 is moved. For example, the implement may be moved by an operator of the machine 110 that actuates the implement 120. The implement 120 may also move based on the movement of the machine 110 over the surface. The IMU230 may determine movement and data related to the movement of the IMU230 may be transmitted to other devices.

The radio 240 is used to receive data from the laser sensor 150. Fig. 4 depicts a laser sensor 150 having a plurality of laser detector elements 310. The laser sensor 150 transmits data related to the laser detector to the processor 320. In one embodiment, the processor 320 analyzes the data from the laser sensor 150 and determines the vertical position of the laser along the vertical axis of the laser sensor 150 at which the laser beam 128 impinges. For example, a detector element located at the vertical center of the laser sensor 150 that detects the laser beam 128 indicates that the laser 128 is impinging approximately at the vertical center of the laser sensor 150. Similarly, a detector element at one end of the laser sensor that detects the laser beam 128 indicates that the laser beam 128 is impinging at the corresponding end of the laser sensor 150. The processor 320 transmits the vertical position data to the radio 330 for transmission to the radio 240 located in the laser detector base 200 (shown in fig. 3). In one embodiment, the radio 240 is used to receive data from the radio 330 and transmit data, such as elevation data, from the computer 235 to other devices using a wired connection, as described below.

Computer 235 is in communication with radio 240. Elevation data (described in detail below) calculated by computer 235 may be transmitted to other equipment, such as machine control indicators (not shown) associated with operation of machine 110 (shown in FIG. 2). In one embodiment, the transmission of data from computer 235 via radio 240 facilitates automation of the operation of a machine, such as machine 110 shown in FIG. 2. For example, actuation of the implement 120 by the machine 110 may be automated to modify the surface based on a desired grade using elevation data calculated by the computer 235. In one embodiment, the elevation data calculated by the computer 235 is transmitted to other devices using a wired connection. For example, a Controller Area Network (CAN) connector located on the computer 235 may be used to connect the device to the computer 235 using a wired connection. In addition, other types of wired connections may also be used.

FIG. 5 depicts a laser detector assembly 100A having a laser sensor 150A located at the lower end of a rod 250A. Laser detector assembly 100B is depicted with laser sensor 150B located at the upper end of rod 250B. A side-by-side comparison of laser detector assembly 100A and laser detector assembly 100B illustrates an operating range 400 of laser detector assembly 100. The operating range 400 of the laser detector assembly 100 is the range in which the laser beam 128 can be detected by one of the laser detector elements 310 of the laser sensor 150. The fixed working range of the prior art laser sensor is limited by the vertical length of the laser detector element of the fixed laser sensor, as opposed to the laser sensor 150 being vertically movable along the length of the rod 150 during operation, thereby allowing a larger working range of the laser beam 128 to be detectable. In one embodiment, the operating range 400 is approximately two meters. The working range 400 may be longer or shorter based on various factors affecting the selection of the vertical length of the pole 250, including the grade correction required, the type of machine and implement, etc.

FIG. 6 depicts a flowchart of a method 500 for detecting a laser beam position on the laser sensor 150 and moving the laser sensor 150 along the length of the rod 250 to keep the laser beam 128 illuminating the laser sensor 150, in accordance with one embodiment. In one embodiment, the method is controlled by computer 235 (shown in FIG. 3) and begins at step 504, where it is determined whether laser beam 128 (shown in FIG. 3) is detected by one or more laser detector elements 310.

If laser light 128 is detected in step 504, the method proceeds to step 506, where the data received from the laser sensor 150 is analyzed to determine where the laser beam 128 was detected to illuminate the laser sensor 150 (i.e., the particular ones of the detector elements 310 upon which the laser light impinges). In step 508, data is received from the position sensor 225 that identifies the position of the carrier 260 (and thus the laser sensor 150) along the rod 250. At step 510, data (e.g., mobile data) is received from IMU 230. In step 512, the data received from the laser sensor 150 in step 506, the data received from the position sensor 225 in step 508, and the data received from the IMU230 in step 510 are filtered. The filtering of the data is described in more detail below in conjunction with fig. 9. In step 514, the vertical position at which the laser beam 128 irradiates the laser sensor 150 is calculated based on the data received from the laser sensor 150. For example, each particular laser detector element of the plurality of laser detector elements 310 is positioned at a particular location relative to the laser sensor 150. If laser light 128 is detected by a particular laser detector element of the plurality of laser detector elements 310, the location along the length of laser sensor 150 at which laser light 128 is illuminated is known based on the known location of each laser detector element of the plurality of laser detector elements 310. In step 516, the new position of the carrier 260 (and the laser sensor 150, since the two are magnetically coupled) is calculated. The new position of the carrier 260 is based on the current position of the carrier 260 and the vertical direction and distance of movement that the carrier 260 needs to move in order to keep the laser of the laser reference plane 130 substantially centered on the laser sensor 150.

In step 518, a motor command is calculated to command the motor 205 to rotate to move the carrier 260 based on the new carrier position calculated in step 516. In step 520, a signal is transmitted to the motor 205 via the motor controller 210, causing the motor 205 to rotate and the carrier 260 (and laser sensor 150) to move to the new carrier position calculated in step 516. From step 520, the method returns to step 504 and the process continues. The method 500 may be started and stopped by the computer 235 as needed to keep the laser beam 128 substantially centered on the laser sensor 150.

Returning to step 504, if no laser light is detected, the method proceeds to step 508 where data is received from the position sensor 225, which identifies the position of the carrier 260 along the rod 250 and the method continues as described above.

In one embodiment, the look-up mode is used to find the elevation of the laser beam output from the laser emitter when the laser detector assembly is activated. FIG. 6B depicts a flow diagram of a method 550 for looking up a pattern. The laser beam may not impinge on the laser sensor upon initial activation of the laser detector assembly. The look-up mode moves the carrier until the laser sensor detects the laser beam. The method begins at step 552 where it is determined whether a laser beam is detected by a laser sensor. If the laser sensor detects a laser beam, the method proceeds to step 558 where the method 500 of FIG. 6A is initiated and the laser beam is continued to be tracked by moving the carrier as described above. If no laser beam is detected in step 552, the method proceeds to step 554 where the motor command is calculated. During start-up, the carrier is moved to the uppermost or lowermost position of the rod and the motor commands are calculated to move the carrier in increments towards the opposite end of the rod 250. In step 556, the motor is actuated using the command calculated in step 554, which causes the carrier to move. In one embodiment, when the carrier reaches the opposite end of the rod, the motor command calculated in step 554 will cause the carrier to move in the opposite direction toward its original position. In one embodiment, the method 550 continues until the laser beam is detected by the laser sensor or the method is stopped by the user. In one embodiment, the method 550 continues for a set time or multiple opposing movements along the rod before being stopped by the computer 235.

In one embodiment, the look-up mode described in method 550 is also used when the laser beam is not detected by the laser sensor for a period of time, such as about one or two seconds, while computer 235 is performing method 500. The method 550 is performed until the laser sensor detects the laser beam in step 552 of the method 550. In one embodiment, the steps of method 550 may be incorporated into the steps of method 500. If no laser beam is detected using the method 550 after a set period of time or multiple movements of the carrier along the length of the rod, an error message may be generated and output to the user informing the user.

In one embodiment, additional information is considered in order to determine whether the laser sensor 150 needs to be moved up or down. In this embodiment, it is additionally determined in step 506 whether the laser 128 was last detected by the detector element 310 in a pattern indicating that the laser sensor 150 exhibits an upward movement or a downward movement relative to the laser beam 128. The computer 235 may determine the speed at which the laser sensor 150 exhibits upward or downward movement relative to the laser beam 128 based on the pattern. For example, a laser beam 128 detected by detector elements in sequence starting with the first detector element and continuing to be detected by detector elements vertically above the first detector element indicates that the laser sensor 150 is moving downward. Similarly, laser light 128 detected by the detector elements in sequence starting with the first detector element and continuing to be detected by detector elements vertically below the first detector element indicates that the laser sensor 150 is moving upward. In one embodiment, the motor command is calculated by the computer 235 based on the direction and speed in which the laser beam 128 is determined to move vertically relative to the laser sensor 150 in step 518. For example, if it is determined that the laser light is moving upward at a particular speed, the computer 235 calculates the amount of rotation that the motor 205 needs to rotate in order to bring the laser light into view of a particular one of the detector elements 310, such as a detector element located vertically near the center of the laser sensor 150. In step 510, the computer 235 outputs a signal to the motor controller 210 and the motor controller actuates the motor 205 based on the signal received from the computer 235. After the motor has been moved in step 510, the method returns to step 504.

FIG. 9 depicts an embodiment in which Kalman filters 801, 802, and 803 are used to fuse measurements from the position sensor 225, IMU230, and laser sensor 150. As shown in fig. 9, data from the position sensor 225, the IMU230, and the laser sensor 150 are filtered by kalman filters 801, 802, and 803, respectively. The filtered data is then received by the computer 235, which calculates the appropriate motor command and transmits the command to the motor controller 210, as described above in connection with FIG. 6. Measurements are fused using a kalman filter, providing position and movement information about the laser sensor 150. The kalman filter described herein may be software-based, hardware-based, or a combination of software and hardware. In one embodiment, the purpose of the kalman filter is to estimate the position and velocity of the laser sensor and the estimated laser incidence position along the rod relative to the laser detector base 200. For example, in steps 508 and/or 524 of method 500, the position and movement information is used to calculate motor commands to position laser sensor 150 along rod 250.

The frequency at which the laser light 128 impinges on the laser sensor 150 depends on the rate of rotation of the laser light 128 about the vertical axis of the laser transmitter 140. A typical rate of rotation of the laser light 128 about the laser transmitter 140 is about 600 revolutions per minute, which causes the laser light 128 to impinge on the laser sensor 150 at a frequency of 10 Hz. Using data from the IMU230 to sense movement of the laser detector assembly 100 allows output of elevation values at a higher frequency than the laser incident frequency, since changes in position of the laser incident may be predicted based on the data from the IMU 230. Thus, the frequency at which elevation values are calculated is independent of the laser incident frequency and may be any desired frequency supported by the frequency at which data is received from the IMU230 and the frequency at which elevation values may be calculated by the computer 235.

In one embodiment, the two kalman filters 801 and 802 process data from the position sensor 225 and the IMU230 synchronously at 100Hz to track the motion of the laser sensor 150 and the laser incidence position in a decoupled manner. The kalman filter 801 processes the position sensor 225 measurements and also uses the motor commands sent to the motor controller 210 to obtain a better estimate of the speed of the laser sensor 150 relative to the rod 250. A kalman filter 802 that processes IMU measurements uses the IMU230 to estimate the location of the laser incidence between actual laser incidences. This allows reporting of the estimated laser incidence position at 100 Hz.

The kalman filter 803 processes the laser sensor measurements because, as described above, they are typically received at about 10 Hz. As the laser sensor measurements indicate the relative distance between the laser incidence position and the detector position, the kalman filter 803 tracks the movement of both the detector and the laser incidence position in a coupled manner. The kalman filter 803 prevents the stick acceleration kalman filter 802 from deviating over time. As described above, in one embodiment, three kalman filters are used. In other embodiments, less than three kalman filters may be used.

Fig. 7A depicts a fixture 120 whose lowermost edge is positioned parallel to the laser reference plane 130. However, the fixture 120 may not always be positioned parallel to the laser reference plane 130. For example, a machine associated with implement 120 can rotate implement 120 about a longitudinal axis of the machine to which implement 120 is attached. Furthermore, the machine to which the implement 120 is attached may travel on uneven ground, such as an incline, which may cause the implement 120 to be non-parallel to the laser reference plane 130. Fig. 7B depicts the fixture 120A with its lowest edge non-parallel to the laser reference plane 130. Implement 120A may rotate about a longitudinal axis of machine 110 in response to an operator moving implement 120A or in response to machine 110 moving across a slope. As shown in fig. 7A and 7B, rotation of the tool 120A in the three-dimensional space shown in the coordinate system 600 requires the laser sensor 150A to be moved toward the tool 120A, as indicated by arrow 610, in order to keep the laser of the laser reference plane 130 substantially centered on the laser sensor 150A.

To illustrate the change in orientation of rod 250 relative to vertical, a complementary filter is used. The complementary filter fuses data from the 3-axis accelerometer and data from the 3-axis gyroscope measurements obtained by the IMU230 and provides a unit vector indicating the direction of gravity in the coordinate system of the IMU 230. The unit gravity vector is used to determine the angle of the rod relative to the vertical. This angle is used to project a 3-axis accelerometer reading from the IMU230 to derive the bar acceleration along the bar axis. Assuming that the rotating laser plane is fixed in the world frame of reference, this acceleration is interpreted as the acceleration of the laser incidence position along the rod frame, represented in the coordinate system of the rod frame. From experiments, a unit gravity vector estimation is sufficient to control the motor up to 20 degrees from vertical. In other embodiments, other types of filters may be used, such as extended kalman filters, unscented kalman filters, or particle filters. These filters may be used alone or in combination with other filters, such as low pass filters, high pass filters, band pass filters, and/or other types of filters.

FIG. 8 depicts a flowchart of a method 700 performed by the computer 235 for detecting the laser beam 128 illuminating the laser sensor 150 and outputting elevation data. In step 702, the laser beam 128 is detected by the laser sensor 150. In step 704, the location at which the laser 128 strikes the laser sensor 150 is determined. For example, the laser beam 128 is detected by one of the laser detector elements 116 that is located at a known position along the length of the laser sensor 150. In step 706, the position of the carrier 260 (which is at the same location as the laser sensor 150 based on magnetic coupling with the laser sensor) is determined based on data from the position sensor 225. In step 708, data from IMU230 is read. In one embodiment, sensor data from the IMU230 is transmitted to the computer 235 and may be used to determine the position and movement of the estimated laser incident position from the rotating laser beam 128 along the rod 250. In step 710, elevation values are determined (described in detail below). In one embodiment, the elevation value represents the elevation of the bottom edge of the implement 120. In other embodiments, the elevation value may represent other elevations, such as the elevation of the laser detector base 200. In step 712, the elevation values are output from the computer 235 and transmitted to the radio 240, which transmits the elevation values to another device, such as a control device located in the cab of the machine 110.

The elevation values determined in step 710 may be calculated using different data and methods. In one embodiment, the distance from the laser detector base 200 at which the laser irradiation is detected is calculated based on the position at which the laser light is incident on the laser sensor 150 and the distance from the laser detector base 200 at which the laser sensor 150 is detected. The elevation value does not take into account whether the laser detector assembly 100 is tilted away from the vertical. In some cases where the laser detector assembly 100 is unlikely to tilt away from the vertical, it may be sufficient to calculate elevation values using this method.

In one embodiment, the elevation value is calculated based on additional information from the IMU 230. In such embodiments, the elevation value is calculated based on the distance from the laser detector base 200 at which the laser incidence was detected and information from the IMU230 regarding the angle at which the laser detector assembly 100 is tilted away from the vertical. As shown in fig. 7 and described above, the tilting of the laser detector assembly 100 causes a difference between the elevation in the world frame of reference and the elevation in the rod frame of reference. This can cause elevation calculation errors unless data from the IMU230 is used to determine the deviation of the laser detector assembly 100 from the vertical in the world frame of reference.

In one embodiment, data from laser sensors 150, position sensors 225, and IMU230 is used to calculate the elevation values determined in step 710. In such embodiments, the data from the IMU230 is related to: inclination of the laser detector assembly 100 to the vertical; and data relating to the position and movement of the estimated laser incident position along rod 250 from rotating laser beam 128. Using data from all three devices to calculate the elevation value generally provides a more accurate value than the other methods described above. Further, the data received from the three devices may be used to calculate elevation values at a higher frequency than the frequency of laser incidence detected by laser sensor 150 as described above.

The foregoing detailed description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the inventive concepts disclosed herein is not to be determined from the detailed description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are merely illustrative of the principles of this invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the inventive concept. Various other combinations of features may be implemented by those skilled in the art without departing from the scope and spirit of the inventive concept.