Mechanical hand self-adaptive flexible clamping force control method for hot extrusion forming

Abstract

The application discloses a kind of mechanical hand adaptive flexible clamping force control method of hot extrusion forming piece, belong to special operation robot technical field.This method includes: according to the minimum clamping force of workpiece weight and friction coefficient, maximum clamping force is determined in combination with the deformation resistance of material at different temperatures and the allowable machining allowance, and it is converted into the torque limit value of drive motor;Adopt force / position hybrid control strategy, clamping is carried out in position control mode, real-time detection motor output torque, stop and lock position when reaching limit value, realize flexible clamping;Through infrared thermometer, workpiece surface temperature is monitored on-line, and the appropriate opportunity of avoiding the lowest stage of workpiece deformation resistance is selected to clamp.The application can realize reliable, non-destructive clamping to easily deformed workpiece in high temperature environment, effectively avoid the annealing softening problem caused by long time heating of mould, improve production efficiency and mould service life.

Description

Technical Field

[0001] This invention belongs to the technical field of special operation robots, specifically relating to an adaptive flexible clamping force control method for a manipulator of a hot-extruded part. Background Technology

[0002] A forging robot is an automated auxiliary device used in the forging process to clamp and transfer workpieces; it is a type of specialized robot. The mechanism used by a forging robot to clamp the workpiece is generally called a clamp, as shown in the attached image. Figure 1 The clamp shown is a linkage lever type clamp structure. Its main components include jaws, clamping claws (lever), connecting rods, push rods, and clamp supports. Its working principle is as follows: The clamp drive element (electric cylinder or hydraulic cylinder) pushes the push rod, which rotates through two connecting rods connected to the hinge point at the push rod head. This causes the two clamping claws to rotate symmetrically in opposite directions around the hinge point fixed on the clamp support, bringing the jaws closer to the center line and generating a clamping force on the workpiece.

[0003] A type of thermoextruded part, shaped as a deep-hole, thin-walled cylindrical component, exhibits very low deformation resistance at forming temperatures of 1000–1100°C. This presents a challenge: the clamping force must be appropriate for the robot to hold and transfer this workpiece. Excessive clamping force can cause surface deformation or even render the workpiece unusable; insufficient clamping force will result in insufficient friction between the jaws and the workpiece, preventing it from being properly gripped.

[0004] Currently, due to the lack of manipulators capable of flexible clamping, molded parts must be placed inside the mold for 7-8 hours until they naturally cool to room temperature before they can be removed using an internal lifting tool. This drawback undoubtedly keeps the mold in an overheated state for an extended period, essentially subjecting it to annealing and reducing its performance.

[0005] Therefore, it is necessary to develop an adaptive flexible clamping force control technology for robotic arms for hot extruded parts that are easily deformed at high temperatures, so as to ensure that after the deep hole thin-walled cylindrical parts are extruded, the robotic arm clamp can hold the workpiece and move it out of the mold cavity without damaging the workpiece surface. Summary of the Invention

[0006] In view of this, the present invention provides a method for controlling the adaptive flexible clamping force of a robot for hot-extruded parts, which can dynamically adjust the magnitude of the robot's clamping force so that the robot's gripper can clamp the workpiece in a red-hot state without damaging the workpiece surface.

[0007] The technical solution for implementing the present invention is as follows: A method for controlling the adaptive flexible clamping force of a robot for hot-extruded parts includes the following steps: S1. Determine the range of flexible clamping force: Calculate the minimum clamping force N to ensure reliable clamping based on the workpiece weight and the friction coefficient between the jaws and the workpiece. min Based on the deformation resistance of the workpiece material at different temperatures and the allowable workpiece surface deformation, the maximum clamping force N without damaging the workpiece is calculated. max ; S2, apply the minimum clamping force N min With maximum clamping force N max Converting this to the output torque limit value of the clamp drive motor yields the minimum output torque T of the motor. mmin With the maximum value T mmax ; S3. Detect the surface temperature of the workpiece online, and call the preset clamping process formula according to the detected temperature. The clamping process formula includes the clamping position range corresponding to the temperature and the motor output torque limit value. S4. Perform clamping operation: Control the clamp drive motor to operate in position mode, moving the jaws toward the workpiece, while simultaneously detecting the motor output torque T in real time. m When the motor output torque T is detected m The torque limit value T at the current temperature determined in step S2 is reached. mmin <T m <T mmax When the motor stops running and the clamp position is locked, adaptive flexible clamping of the workpiece is achieved.

[0008] Further, in step S1, the minimum clamping force N min Calculated using the following formula: N min = G / (2f) Where G is the weight of the workpiece, and f is the coefficient of friction between the jaws and the workpiece surface.

[0009] Further, in step S1, the maximum clamping force N max The determination includes: The deformation resistance σ of the workpiece material in the vicinity of the final forging temperature was obtained through experimental calibration. t The correspondence between temperature t and temperature; The allowable workpiece surface deformation for clamping is determined based on the allowable machining allowance of the forging, and the maximum clamping force N is calculated by combining this with the area S of the clamping force application. max .

[0010] Furthermore, the clamping force application area S corresponds to the single-sided contact area between the V-shaped jaws and the workpiece.

[0011] Furthermore, in step S2, the minimum value T of the motor output torque... mmin and maximum value Tmmax It is by using the minimum clamping force N min and maximum clamping force N max It is obtained by converting the lever ratio of the clamp arm, the thrust relationship of the clamp drive rod, and the transmission parameters of the electric cylinder in sequence.

[0012] Furthermore, in step S3, the online detection of the workpiece surface temperature is achieved using an infrared thermometer.

[0013] Furthermore, the clamping drive mechanism is an electric cylinder driven by a servo motor or a servo hydraulic cylinder.

[0014] Beneficial effects: Compared with the prior art, the technical solution provided by the present invention has the following significant advantages: 1. This invention enables online rapid removal of high-temperature workpieces, effectively protecting the lifespan of the mold. Through adaptive flexible clamping force control, the robot can safely clamp and remove the workpiece from the mold cavity while it is still red-hot, avoiding the "annealing" effect caused by the workpiece cooling in the mold for a long time (7-8 hours). This significantly extends the service life of the mold and improves production efficiency.

[0015] 2. This invention dynamically determines the clamping force window (between the minimum and maximum clamping forces) that can reliably clamp the workpiece without causing plastic deformation by combining theoretical calculations with high-temperature performance calibration of materials. It is then precisely executed through a force / position hybrid control strategy, fundamentally solving the problem of workpiece surface crushing, deformation, or scrapping caused by improper clamping force.

[0016] 3. This invention uses an infrared thermometer to detect the surface temperature of the workpiece in real time online. This not only provides a basis for determining the real-time deformation resistance of the material, but also intelligently determines the best clamping time, avoiding the dangerous temperature range where the workpiece material has the lowest deformation resistance, thereby further ensuring the success rate of the clamping operation and the quality of the workpiece.

[0017] 4. The core of the control method of the present invention lies in the calculation model and control logic of the clamping force. Its principle is not only applicable to electric cylinder clamps driven by servo motors, but also applicable to clamping mechanisms of other drive forms such as servo hydraulic cylinders. It has good versatility and portability, and is easy to modify and promote on existing equipment. Attached Figure Description

[0018] Figure 1 This refers to the linkage lever type clamp structure involved in this invention.

[0019] Figure 2 This is a force diagram of the cylindrical part during clamping.

[0020] Figure 3This is a diagram showing the force and dimensions of a linkage lever clamp structure. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] This invention provides a method for controlling the adaptive flexible clamping force of a robot for hot-extruded parts. The core of this invention lies in achieving adaptive flexible clamping of high-temperature workpieces by a robotic arm through calculating the clamping force range, employing a hybrid force / position control strategy, and utilizing online temperature detection. Specifically, it comprises three main parts: clamping force calculation and calibration, a flexible clamping force control strategy, and online detection of workpiece surface temperature and determination of clamping timing.

[0023] Specific technical solutions 1. Clamping force calculation and calibration First, such as Figure 2 As shown, based on the workpiece weight G and the coefficient of friction (f, usually taken as 0.1 to 0.3, or measured by friction and wear test), the minimum clamping force N required at the jaw end is calculated. min To ensure the workpiece does not slip; (1) Secondly, regarding the deformation resistance σ of the workpiece material near the final forging temperature... t Actual measurements and calibrations were performed, and the relationship between temperature t and deformation resistance σ was established through data fitting. t The corresponding relationship is as follows: Based on the allowable machining allowance of the forging, the allowable workpiece surface deformation for clamping is designed, the area S of the clamping force is determined, and then the maximum allowable clamping force N is calculated. max To prevent workpiece deformation: Finally, the clamping force is converted into the output torque T of the electric motor driving the clamp. m .like Figure 3 As shown, for a V-jaw clamp, the clamping force on one side of the contact surface, the total clamping force, the driving force at the rear end of the clamp arm, and the thrust of the clamp drive rod are calculated through a mechanical model, and finally the motor output torque is derived. V-jaw clamping force on one side of the contact surface (2) Total clamping force of V-jaws on one side (3) Clamp arm rear drive force (4) Clamp drive rod thrust (5) The output torque of the electric cylinder drive motor (6) According to formulas (1), (3), (4), (5), and (6), the minimum output torque Tm of the electric cylinder drive motor under the clamping condition can be obtained:

[0024] According to formulas (2), (3), (4), (5), and (6), the maximum output torque Tm of the electric cylinder drive motor under the condition of not damaging the workpiece can be obtained:

[0025] Where L is the lead of the electric cylinder lead screw, i is the gear ratio of the reducer, and η1 and η2 are the transmission efficiencies of the electric cylinder and the reducer, respectively. Based on the above calculations, the minimum value T of the motor output torque is obtained. mmin and maximum value T mmax Ensure that the clamping force is within a safe range.

[0026] 2. Flexible clamping force control strategy A force / position hybrid control strategy is adopted based on the following criteria: Rule 1: The gripper position exceeds the theoretical contact position.

[0027] Criterion 2: The motor output torque meets T mmin <T m <T mmax ; Based on the clamping position range and clamping force limit value under different temperature ranges, a process formula is formulated. During clamping, the clamp drive motor is first controlled to perform the clamping action according to the position mode, while the motor output torque is detected in real time. When the torque reaches the limit value, the clamp action is immediately stopped and the position is locked to achieve flexible clamping.

[0028] 3. Online detection of workpiece surface temperature and determination of clamping timing Infrared thermometers are used to monitor the workpiece surface temperature in real time. Because the workpiece is too hot and has low deformation resistance when it is first formed, it is necessary to wait for the temperature to drop to a level that avoids the lowest stage of workpiece material deformation resistance before clamping. The system calls the corresponding clamping process formula based on the online temperature detection, driving the robotic arm to adaptively clamp, ensuring that the clamping force does not cause workpiece deformation while reliably transferring the workpiece.

[0029] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the adaptive flexible clamping force of a robotic arm for hot-extruded parts, characterized in that, Includes the following steps: S1. Determine the range of flexible clamping force: Calculate the minimum clamping force N to ensure reliable clamping based on the workpiece weight and the friction coefficient between the jaws and the workpiece. min Based on the deformation resistance of the workpiece material at different temperatures and the allowable workpiece surface deformation, the maximum clamping force N without damaging the workpiece is calculated. max ; The minimum clamping force N min Calculated using the following formula: N min = G / (2f) Where G is the weight of the workpiece, and f is the coefficient of friction between the jaws and the workpiece surface; The maximum clamping force N max The determination includes: The deformation resistance σ of the workpiece material in the vicinity of the final forging temperature was obtained through experimental calibration. t The correspondence between temperature t and temperature; The allowable workpiece surface deformation for clamping is determined based on the allowable machining allowance of the forging, and the maximum clamping force N is calculated by combining this with the area S of the clamping force application. max ; S2, apply the minimum clamping force N min With maximum clamping force N max Converting this to the output torque limit value of the clamp drive motor yields the minimum output torque T of the motor. mmin With the maximum value T mmax ; S3. Detect the surface temperature of the workpiece online, and call the preset clamping process formula according to the detected temperature. The clamping process formula includes the clamping position range corresponding to the temperature and the motor output torque limit value. S4. Perform clamping operation: Control the clamp drive motor to operate in position mode, moving the jaws toward the workpiece, while simultaneously monitoring the motor output torque T in real time. m When the motor output torque T is detected m The torque limit value T at the current temperature determined in step S2 is reached. mmin <T m <T mmax When the motor stops running and the clamp position is locked, adaptive flexible clamping of the workpiece is achieved.

2. The method for controlling the adaptive flexible clamping force of a robotic arm for hot-extruded parts according to claim 1, characterized in that, The clamping force area S corresponds to the single-sided contact area between the V-shaped jaws and the workpiece.

3. The method for controlling the adaptive flexible clamping force of a robot for hot-extruded parts according to claim 1, characterized in that, In step S2, the minimum value T of the motor output torque. mmin and maximum value T mmax It is by using the minimum clamping force N min and maximum clamping force N max It is obtained by converting the lever ratio of the clamp arm, the thrust relationship of the clamp drive rod, and the transmission parameters of the electric cylinder in sequence.

4. The method for controlling the adaptive flexible clamping force of a robot for hot-extruded parts according to claim 1, characterized in that, In step S3, the online detection of the workpiece surface temperature is achieved using an infrared thermometer.

5. The method for adaptive flexible clamping force control of a robotic arm for hot-extruded parts according to claim 1, characterized in that, The clamp drive mechanism is either an electric cylinder driven by a servo motor or a servo hydraulic cylinder.

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