A self-calibration method and system for a laser measuring device
By combining hardware and software self-calibration methods, the problems of cumbersome operation and large measurement errors in existing laser measurement equipment are solved, realizing low-cost, high-precision laser measurement with self-calibration function, and improving the portability and reliability of the equipment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 古文坤
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-05
AI Technical Summary
Existing laser measurement equipment requires carrying multiple devices during measurement, which is cumbersome to operate. The measurement results rely on manual readings and have large errors. Furthermore, they are affected by the equipment's posture and friction, making it difficult to achieve low-cost, high-precision real-time calibration and compensation.
By combining hardware and software, a cross-shaped laser emission unit, an angle detection unit, an attitude detection unit, and a central control interaction unit are used, along with a self-test program and a damping mechanism, to achieve real-time compensation of the equipment's attitude and friction, reducing the requirements for mechanical precision. Closed-loop control is achieved using MEMS sensors and a touch screen.
It achieves low-cost, high-precision laser measurement with a measurement error of less than 0.1°, has a self-calibration function, reduces reliance on high-precision mechanical structures, and improves the portability and reliability of the equipment.
Smart Images
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Abstract
Description
[Technical Field]
[0001] This invention belongs to the field of measuring instrument technology, specifically relating to a comprehensive instrument integrating laser ranging, horizontal measurement, and tilt measurement, and particularly to an automatic calibration control method for the instrument. [Background Technology]
[0002] Existing laser measuring equipment is mainly divided into three categories: laser rangefinders, laser levels, and tilt meters. When conducting engineering surveys, users often need to carry multiple devices, which is cumbersome to operate, and the measurement results rely on manual readings, resulting in significant errors.
[0003] In horizontal measurement scenarios, traditional equipment typically relies on high-precision mechanical structures or expensive encoders to achieve angle control. Low-cost solutions, however, often suffer from the following drawbacks: 1. Affected by equipment posture: If the equipment itself is not in a perfectly horizontal position, the angle of the emitted laser will be superimposed on the tilt angle of the equipment, resulting in measurement error. Second, friction interference: When the motor rotates, friction will cause the actual rotation angle to differ from the expected rotation angle. Furthermore, friction will change with wear and temperature, making it difficult to establish a fixed mathematical model. Second, the lack of real-time closed-loop calibration: Most existing equipment uses open-loop control, which cannot verify and correct the actual output angle. Therefore, a low-cost, high-precision measurement and control method is needed that can self-calibrate in real time and compensate for equipment attitude and friction interference. [Summary of the Invention]
[0004] The purpose of this invention is to provide a self-calibration method for laser measurement equipment. By combining hardware and software, it can achieve real-time compensation for the frictional forces experienced by the equipment during posture and motor rotation, thereby improving measurement accuracy and reducing the requirements for mechanical precision. This results in a low-cost, portable, and highly reliable comprehensive measurement instrument.
[0005] To achieve the above objectives, the technical solution adopted by this invention includes three parts: hardware structure design, core control algorithm, and self-test program. Hardware Structure
[0006] Cross-shaped laser emission unit: The front end of the miniature brushless motor is connected to the cross-shaped laser emitter, and the motor drives the cross-shaped laser emitter to rotate.
[0007] Ranging unit: A diffuse reflector receiver and a single-point laser emitter are mounted on the top surface of the device.
[0008] Calibration equipment insertion slot: On the surface of the device where the cross laser emitter is located, take the point where the cross laser emitter is located as the center and the touch screen as the circumference, take four points outside the circumference, and in the line segments from each of these four points to the center of the circle, the included angle between adjacent line segments is 90°. These four points are the positions for the screws to install the calibration equipment.
[0009] Angle detection unit: A hard rubber ring is fitted on the horizontal axis of the cross laser emitter, and the hard rubber ring has a protrusion; a self-capacitive touch screen is set within a 360° range around the hard rubber ring. The protrusion of the hard rubber ring contacts the touch screen. When the motor rotates, the protrusion slides across the touch screen, and the touch screen records the arc of the slide, thereby obtaining the actual rotation angle θ.
[0010] Attitude detection unit: The device is equipped with a MEMS gyroscope, MEMS accelerometer, and MEMS pressure gauge to measure the horizontal tilt angle of the device.
[0011] Central control interaction unit: The device panel features an LCD display screen (for display only, no touch function), numeric keys, an OK key (to confirm that the data on the operation screen will be set as the input value), a backspace key, an angle data display lock button (to lock the angle data for easy reading), a device power on / off button, a distance measurement mode on / off button, a level mode on / off button, and a calibration button; the user inputs the target angle θ via the keys.
[0012] Damping mechanism: A damping element (such as a wool felt pad + wave spring) is installed between the motor output shaft and the cross laser emitter to keep the cross laser emitter in a stable position when there is no external force driving it, and resist minor collisions and cable pulling.
Core Control Algorithm
[0013] Define the following angle variables: 0 Input: The angle value input by the user via a button; positive when the motor rotates clockwise. 0. Equipment: The horizontal tilt angle of the equipment measured by MEMS sensors; negative when the equipment rotates clockwise. Target angle θ: The angle of rotation required for the motor to reach the target angle in the horizontal orientation of the equipment (involved in time calculation); clockwise rotation of the motor is positive. θactual: The actual rotation angle measured by the touchscreen; positive when the motor rotates clockwise. θ adjustment: Angle adjustment in the self-test program; positive when the motor rotates clockwise.
[0014] Core formula: θ target angle = θ input + θ device
[0015] Formula meaning: The angle θ input by the user is the expected value when the device is in a horizontal state; when the device has a tilt angle θ, the tilt angle needs to be superimposed on the motor rotation angle to ensure that the actual laser direction is consistent with the user's expectation.
[0016] Motor rotation direction and rotation time: • If the target angle θ is positive, the motor rotates clockwise; • If the target angle θ is negative, the motor rotates counterclockwise; • Take the absolute value of the target angle θ and substitute it into the formula for calculating the motor rotation time.
[0017] "Roll once" motor time calibration: Before the initial startup of the device, one side of the protruding part is calibrated so that, in a horizontal orientation, it is near the point where the X-axis, passing through the cross-section of the self-capacitive touchscreen and through the center of the circle, intersects on the edge of the touchscreen cross-section. Then, the motor drives the cross-shaped laser emitter to rotate a standard angle. The touchscreen records the actual arc traversed. The time required for each 0.1 arc is calculated by dividing the motor's running time by the arc. Subsequent motor control calculates the running time as "target angle × T". This calibration automatically compensates for the effects of friction, voltage fluctuations, and other factors. After calibration, recalibration is generally unnecessary, and the device can be used normally.
[0018] Self-check procedure: After the motor completes its rotation, it enters a self-test program, using the actual rotation angle θ as feedback to perform closed-loop correction. Step 1: Obtain the current θ data (touchscreen reading) and the current θ device data (MEMS reading). Step 2: Calculate the ideal angular distance from the target angle under conditions free from friction, equipment wear, etc. = 0 target angle + θ equipment angle. Step 3: Compare the actual θ with the target angle + θ (device angle).
[0019] Branch processing: • If θactual > θtarget angle + θdevice The motor direction was changed to counterclockwise. θ_adjustment = |θ_target angle - θ_actual angle + θ_equipment| Assign the value of θ to the target angle θ. Drive motor to rotate the target angle θ Return to step 1 • If θactual = 0 target angle + θdevice: No adjustment Return to step 1 (waiting for the next trigger or termination) • If θactual < θtarget angle + θdevice Change the motor direction to clockwise θ_adjustment = |θ_target angle - θ_actual angle + θ_equipment| Assign the value of θ to the target angle θ. Drive motor rotates 0 target angle Return to step 1
[0020] Self-test procedure instructions: • θ target angle -0 real +0 equipment indicates the angle and direction that the current deviation needs to be compensated (the influence of factors such as changes in equipment attitude, friction on the motor, equipment wear, human touch, and bumps has been taken into account; the sign of this value only indicates the direction). • The absolute value is taken as the motor rotation amount, and the direction is determined by the comparison result. The program executes repeatedly until the deviation is zero. • All angles are calculated to an accuracy of 0.1°, with any excess rounded off.
[0021] Synergistic operation of damping and self-testing • The damping mechanism filters out minor disturbances (such as cable pulling or slight impacts) to avoid frequent triggering of the self-test program. • When the disturbance exceeds the damping threshold and causes the laser head to deflect, the self-test program is activated to correct the deviation and minimize back-and-forth oscillations. Damping and self-checking work together to achieve system stability through "mechanical stabilization + software correction". [Attached Image Description]
[0022] To assist in calibration, this device comes with a specially designed calibration apparatus. The invention and the calibration apparatus are further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a top view of the calibration equipment. Example: Place the protruding part of the rubber ring at the upper right corner of the circle, then fix the device to the measuring equipment with screws. Press one side of the protruding part of the rubber ring down onto the line segment on the right side of the circle. Press the "calibrate" button to set the starting point, and then press the calibration button again to confirm. (Before pressing the calibration button again, allow the motor to drive the protruding part of the rubber ring to rotate counterclockwise to recalibrate the value of "time T required per 0.1 radians". If the button is pressed again without performing this process, the value of "time T required per 0.1 radians" will remain unchanged, and the starting point will be updated.)
[0023] To enhance the flexibility of the level's function and ensure precise tilt angle of the laser emitter's axis, a tripod with a gimbal is designed as an accessory to the device. This tripod is small, with its legs collapsing for easy portability. The invention and the tripod are further described below with reference to the accompanying drawings: Figure 2 This is a front view of the bracket. The bracket has clamping devices at both ends of the top for clamping the two sides of the device (not the top and bottom sides, nor the side where the cross laser emitter is located and the opposite side). The tripod is used to fix the position of the device. The bracket only supports the device to rotate on the axis where the laser emitter is located. When the device rotates on the axis, the LCD screen displays the tilt angle of the device on the axis so that the user can accurately control the tilt angle of the device on the axis.
[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 3 This is a cross-sectional schematic diagram of the device structure of the present invention. In the diagram: 1. Motor, 2. Cross laser emitter, 3. Damping element, 4. Hard rubber ring, 5. Rubber ring protrusion, 6. Touch screen, 7. MEMS sensor, 8. Main control panel (including LCD display and buttons), 9. Diffuse reflection receiver, 10. Single-point laser emitter.
Detailed Implementation Methods
[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. Hardware implementation
[0026] Taking a miniature brushless motor (such as the N20 miniature geared motor) as an example, the output shaft is connected to a cross-shaped laser emitter bracket. A hard rubber ring (material: carbon fiber-doped POM, hardness 60 Shore D) is fitted on the bracket. The inner side of the rubber ring is fixed to the motor shaft, and the outer side has a protrusion (0.5mm high, 2mm wide). A self-capacitive touch screen (such as a custom ring touch sensor from Guangzhou Dacai or Lixin Zhixian) is mounted within a 360° radius around the hard rubber ring. The touch screen surface is covered with a hydrophobic coating to prevent water droplet interference.
[0027] A damping plate is installed between the motor output shaft and the bracket: a wool felt washer (0.5mm thick) + a wave spring washer. Adjust the nut pressure to make the damping torque 0.5~1N·cm, and the feel is "can be turned but has uniform resistance".
[0028] The device is equipped with a MEMS six-axis sensor (such as MPU6050) for measuring tilt angles. The front panel features a 2.4-inch LCD (non-touch) and 12 physical buttons (0-9 numeric keys, OK, Backspace, angle data lock button, device power on / off button, distance measurement mode on / off button, level mode on / off button, and calibration button), all with a luminous coating.
[0029] A diffuse reflector receiver and a single-point laser emitter are mounted on the top side of the device.
Usage Example
[0030] The user wants to measure the distance to an obstacle in front of them: 1. Press the distance measurement button, place the device on the ground or hold it in your hand, and point the emission port of the single-point laser emitter toward the object. 2. When the laser beam is emitted and illuminates the obstacle, the diffuse reflection receiver receives the diffuse reflection light of the laser beam and automatically measures the length of the hypotenuse (the location of the laser), the vertical side, and the horizontal side (horizontal distance) using a built-in algorithm. 3. The distance value is displayed on the LCD.
[0031] The user wants to refresh the starting point or the calibration time: 1. Install the calibration equipment and secure it with screws. 2. Press one side of the protruding part of the rubber ring onto the right side of the inner circle of the calibration device, press the "Calibrate" button, and set the starting point. 3. If you need to calibrate the "time T required per 0.1 radians", input the angle value, rotate the device counterclockwise and calculate the new "time T required per 0.1 radians" through the internal program. If not, press the "calibrate" button again without performing this step to set only the starting point.
[0032] The user wants to use the level function: 1. Press the level mode on / off switch, and the cross laser will be emitted. 2. Set the tilt angle of the cross laser relative to the horizontal position through the device input (e.g., if you want to rotate the cross laser "counterclockwise by 45° relative to the horizontal position", input "-45°" through the button and then press the "OK" button). 3. Install the device onto the included bracket and place the bracket on the object surface (because the device has a self-calibration function, the object surface used to place the device does not need to be extremely flat). Rotate the device along the axis of the cross laser emitter. At the same time, the LCD screen displays the tilt angle of the device on that axis, so that the user can accurately control the tilt angle of the device on that axis.
[0033] The above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. [Beneficial Effects]
[0034] Compared with the prior art, the present invention has the following advantages: 1. High precision: The actual rotation angle is measured directly through the touch screen. Combined with the closed-loop self-test program, errors caused by factors such as friction and wear are eliminated, and the measurement accuracy can reach 0.1°. II. Low cost: High-precision control can be achieved using ordinary motors, touch screens, and damping plates without the need for expensive components such as high-precision encoders and precision gearboxes, significantly reducing BOM costs. 3. Strong anti-interference capability: The damping mechanism isolates small disturbances, and the self-testing program can handle large disturbances, resulting in high system stability. IV. Automatic Compensation of Equipment Attitude: The core formula is θ target angle = θ input + θ device. The device automatically integrates user input and equipment tilt angle, eliminating the need for manual leveling. V. Adaptive Wear: The periodically executed "roll" calibration program automatically updates the motor's time parameters to compensate for mechanical wear and aging. 6. High Functional Integration: A single hardware system enables three main functions: laser ranging, level measurement, and tilt measurement, making it a multi-functional device.
Claims
1. A self-calibration method for a laser measurement device, characterized in that, Includes the following steps: Obtain the target angle θ input by the user. The device is used to obtain the horizontal tilt angle θ of the device. The target rotation angle of the motor is calculated using the formula 0 target angle = θ input + θ device. The drive motor rotates the laser emitter. The actual rotation angle θ of the laser emitter is obtained. The actual rotation angle θ is compared with the theoretical angle θ target angle + θ device. Based on the comparison results, the drive motor performs closed-loop correction until θ is equal to 0 target angle + θ device.
2. The self-calibration method according to claim 1, characterized in that, The step of performing closed-loop correction based on the comparison results further includes: If θactual > 0target angle + 0device, then control the motor to rotate in the opposite direction, with a rotation angle of |θtarget angle - θactual angle + 0device|. If θ<0 target angle + 0 device, then control the motor to rotate in the same direction, with a rotation angle of |θ target angle - θ<0 target angle + θ device|. If θactual = θtarget angle + 0device, then no adjustment is required.
3. A self-calibration system for a laser measurement device for implementing the method as described in claim 1 or 2, characterized in that, include: The cross-shaped laser emitting unit includes a motor and a cross-shaped laser emitter that is driven to rotate by the motor. The ranging unit includes a diffuse reflector receiver and a single-point laser emitter. The calibration equipment insertion slot is used to install the calibration equipment that comes with the device. An angle detection unit is used to measure the actual rotation angle θ of the laser emitter. Attitude detection unit, used to measure the horizontal tilt angle θ of the equipment. The central control interaction unit is used to receive the target angle θ input from the user. The control unit is connected to the motor, the angle detection unit, the attitude detection unit, and the central control interaction unit, respectively, and the control unit is used to execute the method as described in claim 1 or 2.
4. The system according to claim 3, characterized in that, The angle detection unit includes: A rigid rubber ring is fitted onto the rotating shaft of the laser emitter, and the rigid rubber ring has a protrusion. The self-capacitive touchscreen is arranged in a ring around the periphery of the hard rubber ring and contacts the protrusion. When the motor rotates, the protrusion traverses the touchscreen, and the touchscreen records the arc of the traverse, thereby obtaining the actual rotation angle θ.
5. The system according to claim 3, characterized in that, It also includes a damping mechanism, which is located between the motor output shaft and the laser emitter to provide damping force for the rotation of the laser emitter to resist small disturbances.
6. The system according to claim 5, characterized in that, The damping mechanism works in conjunction with the control unit: The damping mechanism is used to filter out small disturbances below a preset threshold. When the disturbance exceeds a preset threshold and causes the actual turning angle to change, the control unit performs correction by executing the method as described in claim 1 or 2.
7. The system according to claim 3, characterized in that, The control unit is also used to perform motor time calibration. The calibration method includes: placing the protruding part of the rubber ring in the upper right corner of the calibration device, fixing the calibration device, pressing the edge of the protruding part of the rubber ring onto the right side line segment in the calibration device, pressing the "calibrate" button to set the starting point, controlling the motor to drive the laser emitter to rotate counterclockwise by a standard angle, recording the actual arc traversed on the touch screen, calculating the time T required per unit arc by dividing the motor running time when traversing the arc by the arc, and subsequently calculating the running time of the motor control according to the target angle × T.
8. The calibration method according to claim 7, characterized in that... A special calibration device is used for precise calibration. This device consists of a hollow ring with four baffles underneath, and the four baffles extend outwards through holes.
9. The system according to claim 3, characterized in that, The central control interaction unit includes an LCD display screen and physical buttons, or a communication interface for receiving external commands.
10. The system according to claim 4, characterized in that, The angle detection unit can also be one of a magnetic encoder, a grating code disk, or a potentiometer.
11. The system according to claim 5, characterized in that, The damping mechanism can also be one of a magnetic damper, a viscous damper, or a worm gear self-locking structure.
12. The system according to claim 3, characterized in that... A specially designed bracket is used for precise crosshair laser placement. This bracket has a ball head, a collapsible tripod, and a clamp at the top for holding the two ends of the device in place.