Pressure control method of z-axis module

Abstract

The embodiment of the application discloses a pressure control method of a Z-axis module, comprising: a pressure calibration step: driving an output shaft to move from position A to position C downward at a first speed, collecting the current of a Z-axis motor during the movement from position A to position C at a preset frequency, and returning to position A; driving the output shaft to move from position A to position B at a second speed, driving the Z-axis motor with preset calibration currents I1 and I2 respectively, so that the output shaft moves to position C, and detecting and recording the pressure values F1 and F2 of the output shaft; a grabbing control step: driving the output shaft to move from position A to position B at a preset speed, driving the Z-axis motor according to the obtained control current, and making the output shaft press down to position C. The application does not need to install a pressure sensor on the Z-axis module, has simple structure design, high stability and simple operation, and can ensure accurate open-loop force control output when the mechanical assembly and friction resistance are inconsistent.

Description

Technical Field

[0001] This invention relates to the field of robotic arm technology, and in particular to a pressure control method for a Z-axis module. Background Technology

[0002] In applications such as chip mounting, die bonding and removal, camera module assembly, and lithium battery scraping, the pressure control requirements of the Z-axis module output are high during chip mounting, lens assembly, or scraping. Moreover, customer products have certain tolerances. Excessive pressure will cause product damage, while insufficient pressure will affect the product qualification rate. Therefore, it is required that the Z-axis downward pressure needs to output constant force at different heights. Thus, the market needs a solution that can guarantee accurate pressure values ​​at different downward pressure heights while also requiring high efficiency.

[0003] Existing similar solutions:

[0004] 1. Servo Motor Pressure Closed-Loop Module: A pressure sensor is installed on the Z-axis module to collect pressure data in real time and feed it back to the driver to adjust the servo motor torque and output force in real time. This closed-loop pressure control method results in relatively low overall efficiency. The pressure sensor needs to transmit real-time data to the driver, which then determines whether the motor output force is sufficient based on the sensor signal. This inefficiency places high demands on the refresh rate of the pressure sensor and the scanning frequency of the driver, leading to higher overall costs.

[0005] 2. Constant force spring module: A constant force spring is installed on the Z-axis module to ensure a constant force output at the end of the actuator module through mechanical means. A constant force magnetic spring counterweight is installed on the linear motor, and pressure is output by outputting a constant current.

[0006] However, the solution using a servo motor pressure closed-loop module has disadvantages: slow electrical response time; physical contact between the servo motor and the lead screw, which can lead to wear and affect accuracy; real-time adjustment of the force output using a pressure sensor closed-loop control severely affects work efficiency; the control module is large in size and relatively complex in structure; and the resistance varies too much at different strokes, making it impossible to output constant force.

[0007] The solution using constant force spring modules has disadvantages: for each specification and torque, the springs need to be replaced frequently when different pressure control requirements are met, which is inconvenient for maintenance; and the force control accuracy will be affected after the springs are repeatedly compressed a certain number of times. Summary of the Invention

[0008] The technical problem to be solved by the embodiments of the present invention is to provide a pressure control method for a Z-axis module to solve the problem of unstable pressure output.

[0009] To address the aforementioned technical problems, this invention proposes a pressure control method for a Z-axis module. The Z-axis module includes an output shaft and a Z-axis motor for driving the output shaft to move up and down. The method includes:

[0010] Pressure calibration steps: Define positions A, B, and C from top to bottom, where position A is the initial waiting position of the output shaft, position C is the lowest position of the output shaft pressing down, and position B is the preset position to start contacting the product to be gripped.

[0011] The drive output shaft moves from position A downwards at a first speed to position C. The current driving the Z-axis motor during this movement is collected at a preset frequency, resulting in a current set {K1, K2...K...}. b K b+1 ...K n}, then return to positions A and S AC / n=S AB / b = First speed / Preset frequency, S AC Let S be the distance from position A to position C. AB This represents the distance from position A to position B.

[0012] The drive output shaft moves from position A to position B at a second speed. The Z-axis motor is driven by a preset calibration current I1 to move the output shaft to position C. The pressure value F1 of the output shaft is detected and recorded. The drive output shaft returns from position C to position B at a first speed, and then returns to position A at a second speed.

[0013] After the output shaft is driven to move from position A to position B at the second speed, the Z-axis motor is driven with the preset calibration current I2 to press the output shaft down to position C. The pressure value F2 of the output shaft pressing down is detected and recorded. The output shaft is driven to return from position C to position B at the first speed, and then to return to position A at the second speed to complete the calibration, where I2 > I1.

[0014] Grasping control steps: Divide position B to position C into nb segments, calculate the control current of each segment from position B to position C, drive the output shaft from position A to position B at a preset speed, drive the Z-axis motor according to the obtained control current, so that the output shaft presses down to position C, and after the product to be grasped is grasped, drive the output shaft to return to position B at the first speed, and then return to position A at the second speed.

[0015] M p =F 目 *( | I2- I1| / | F2-F1|) +I 偏 +(I 偏 - K p );

[0016] I偏 = I1-F1*(I2-I1) / (F2-F1);

[0017] Where p∈{b, b+1…n}, M p I is the control current for segment p. 偏 F is the deviation value compensated for from position B to position C. 目 The pressure value applied to the target product to be grasped.

[0018] Furthermore, the distance from position B to position C is ≤2mm.

[0019] Furthermore, the preset speed is the second speed.

[0020] Furthermore, the pressure calibration step is followed by a calibration verification step: adjust position B and verify whether the deviation between the target downward pressure value and the actual downward pressure value at different heights is within the preset range. If not, recalibrate.

[0021] Furthermore, the range of the first velocity is 0.5 mm / s to 5 mm / s.

[0022] Furthermore, the preset frequency is 10kHz.

[0023] The beneficial effects of this invention are as follows: This invention does not require the installation of a pressure sensor on the Z-axis module, resulting in a simple structural design and high stability; the power transmission of this invention involves no physical contact, and the power transmission mechanism is wear-free; for pressure control of different product heights, only the controller parameters need to be changed, making operation simple; this invention can also ensure accurate open-loop force control output even when mechanical assembly and frictional resistance are inconsistent. Attached Figure Description

[0024] Figure 1 This is a front view of the Z-axis module according to an embodiment of the present invention.

[0025] Figure 2 This is a rear view schematic diagram of the Z-axis module according to an embodiment of the present invention.

[0026] Explanation of icon numbers

[0027] 1. Controller, 2. R-axis motor, 3. Spring, 4. Guide rail, 5. Output shaft, 6. Z-axis motor. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] In this embodiment of the invention, directional indicators (such as up, down, left, right, front, back, etc.) are only used to explain the relative positional relationship and movement of each component in a specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0030] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0031] Please refer to Figure 1 The pressure control method of the Z-axis module in this embodiment of the invention includes a pressure calibration step and a gripping control step. The Z-axis module includes a controller, a driver, an R-axis motor, a spring, a guide rail, an output shaft, and a Z-axis motor (linear motor) for driving the output shaft up and down. A suction nozzle is provided at the end of the output shaft. The spring is preferably a constant-force magnetic spring. The controller controls the current driving the Z-axis motor through the driver. This part of the structure is prior art and will not be described in detail here. In existing Z-axis modules with this structure, when the Z-axis motor is under open-loop force control, there is a problem of inconsistent frictional force at different strokes, leading to unstable pressure accuracy output.

[0032] Please refer to Figure 2 Define positions A, B, and C from top to bottom. Position A is the initial waiting position before the output shaft is pressed down, position C is the lowest position when the output shaft is pressed down, and position B is the preset position to start contacting the product to be grasped (this position can be adjusted by the user).

[0033] Pressure calibration steps: Drive the output shaft from position A to position C at a first speed (slow speed) from top to bottom. Collect the current of the Z-axis motor during the process from position A to position C at a preset frequency to obtain the linear relationship between the output shaft and the current, that is, n sets of current value data of the output shaft from position A to position C at intervals of the first speed / preset frequency. The 1st to nth sets of current data are recorded as K1-K1 respectively. n This yields the current set {K1, K2...K}. b K b+1 ...K n}, then return to position A, i.e., S AC / n=S AB / b = First speed / Preset frequency, S AC Let S be the distance from position A to position C. AB K represents the distance from position A to position B. bThis refers to the current value data in group b, which is the data detected at position B. The purpose of this step in the invention is to detect the frictional force between the guide rails at different positions of the output shaft. When the frictional force varies with height, it can compensate for the frictional force with current, enabling precise control of the pressure output throughout the entire Z-axis motion stroke, achieving force control. The force control deviation fluctuation is within 2g throughout the entire motion stroke. This invention ensures accurate open-loop force control output even when mechanical assembly and guide rail friction resistance are inconsistent.

[0034] A pressure sensor for detecting calibration pressure is placed at position B below the output shaft. The pressure sensor detects the downward pressure on the output shaft; alternative methods can also be used. A 1KG range sensor can be used. Before calibration, a 500kg weight can be used to calibrate the sensor's analog signal, ensuring the actual weight matches the sensor's feedback weight. After calibration, retest with 20g, 50g, 100g, and 200g weights. An error within 1g and no abnormalities are acceptable.

[0035] The drive output shaft moves from position A to position B at a second speed (rapid, about 400 mm / s, acceleration: 2G). The Z-axis motor is driven by a preset calibration current I1 to move the output shaft to position C. The pressure value F1 is detected and recorded. The drive output shaft returns from position C to position B at a first speed, and then returns to position A at a second speed.

[0036] After the output shaft moves from position A to position B at the second speed, it drives the Z-axis motor with a preset calibration current I2, causing the output shaft to press down to position C. The pressure value F2 is detected and recorded. The output shaft is then driven to return from position C to position B at the first speed (slow speed), and then returns to position A at the second speed (fast speed), completing the calibration. Here, I2 > I1. The second speed is greater than the first speed.

[0037] After calibration, precise torque control, i.e., precise control of downward pressure, can be achieved. Once calibration is complete, no further calibration or pressure calibration steps are required; only the gripping control steps are executed cyclically. That is, if the calibration is successful, the pressure calibration step is executed only once, and subsequent operations only involve the gripping control steps. Gripping control steps: Divide position B to position C into nb segments, calculate the control current for each segment from position B to position C, drive the output shaft from position A to position B at a preset speed (rapid), drive the Z-axis motor based on the obtained control current to press the output shaft down to position C, and after successfully gripping the product, drive the output shaft back to position B at a first speed, then back to position A at a second speed.

[0038] M p =F 目 *( | I2- I1| / | F2-F1|) +I偏 +(I 偏 - K p );

[0039] I 偏 = I1-F1*(I2-I1) / (F2-F1);

[0040] Where p∈{b, b+1…n}, M p I is the control current for segment p. 偏 F is the deviation value compensated for from position B to position C. 目 The target downward pressure value set by the user for the product to be grabbed.

[0041] In one implementation, the distance from position B to position C is ≤2mm.

[0042] As one implementation method, the preset speed is the second speed. In practice, the preset speed can also be adjusted according to the user's needs.

[0043] As one implementation method, the pressure calibration step is followed by a calibration verification step: adjusting position B to verify whether the deviation between the target downward pressure value and the actual downward pressure value at different heights is within a preset range (2g). If not, recalibrate. The purpose of the calibration verification step is to verify the linear relationship obtained from the calibration using random pressure output. In specific implementation, F 目 When pressing the product at different heights (position B at different heights) with values ​​of 10g, 30g, 100g, and 200g, the force control deviation should be within 2g.

[0044] As one implementation method, the first speed ranges from 0.5 mm / s to 5 mm / s.

[0045] As one implementation method, the preset frequency is 10kHz.

[0046] This invention utilizes open-loop control of a Z-axis motor (linear motor) to collect current values ​​throughout the entire stroke range. Because the frictional force on the guide rail varies at different stroke heights, force control compensation is performed based on these current differences, achieving precise open-loop force control even at different heights. This invention leverages the high responsiveness and low force constant of linear motors. A pressure sensor calibrates the motor output current and compensates for frictional forces. The controller outputs commands to the driver via an algorithm, and the driver subdivides the current to precisely output torque to the motor.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pressure control method of a Z-axis module, the Z-axis module comprising an output shaft and a Z-axis motor for driving the output shaft to move up and down, characterized in that, The method comprises: A pressure calibration step: defining position A, position B and position C from top to bottom, wherein position A is the starting waiting position of the output shaft, position C is the lowest position of the output shaft under pressure, and position B is the preset starting contact position of the product to be grabbed; The driving output shaft moves from position A to position C downward at a first speed, the current of the Z-axis motor during the movement from position A to position C is collected at a preset frequency, and a current set {K1, K2, …, K b , …, K b+1 , …, K n} is obtained, and then returns to position A, S AC / n = S AB / b = the first speed / the preset frequency, S AC is the distance from position A to position C, and S AB is the distance from position A to position B. Driving the output shaft to move from position A to position B at a second speed, driving the Z-axis motor at a preset calibration current I1 to move the output shaft to position C, detecting and recording the pressure value F1 of the output shaft under pressure, driving the output shaft to return from position C to position B at a first speed, and then returning to position A at a second speed; Driving the output shaft to move from position A to position B at a second speed, and then driving the Z-axis motor at a preset calibration current I2 to move the output shaft to position C, detecting and recording the pressure value F2 of the output shaft under pressure, driving the output shaft to return from position C to position B at a first speed, and then returning to position A at a second speed, completing the calibration, wherein I2>I1; A grabbing control step: dividing the distance from position B to position C into n-b segments, calculating the control current of each segment from position B to position C, driving the output shaft to move from position A to position B at a preset speed, driving the Z-axis motor according to the obtained control current to move the output shaft to position C under pressure, and driving the output shaft to return to position B at a first speed and then to position A at a second speed after completing the grabbing of the product to be grabbed; M p =F 目 *( | I2- I1| / | F2-F1|) +I 偏 +(I 偏 - K p ); I 偏 = I1-F1*( I2- I1) / (F2-F1); where p e {b, b+1,..., n}, M p is the control current for the pth segment, I 偏 is the offset value for the position B to position C compensation, F 目 is the target downforce value for the product to be grabbed.

2. The pressure control method of the Z-axis module according to claim 1, wherein, The distance from position B to position C is ≤2mm.

3. The method of claim 1, wherein the pressure control method is applied to a Z-axis module. The preset speed is the second speed.

4. The method of claim 1, wherein the pressure control method is applied to a Z-axis module. The pressure calibration step further comprises a calibration verification step: adjusting position B to verify whether the deviation between the target pressure value and the actual pressure value under pressure is within a preset range, and if not, recalibrating.

5. The method of claim 1, wherein the pressure control method of the Z-axis module is characterized by, The first speed ranges from 0.5mm / s to 5mm / s.

6. The method of claim 1, wherein the pressure control method of the Z-axis module is characterized by, The preset frequency is 10Khz.

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