Aerodynamic force control actuator, robot with same and polishing method

Abstract

The invention discloses an aerodynamic force control actuator, a robot with the aerodynamic force control actuator and a polishing method. The aerodynamic force control actuator comprises a mounting plate, a double-acting air cylinder, an electric proportional valve set, a controller, a shaft, a floating connector, a three-axis force sensor and a pneumatic polishing head, the double-acting cylinder is mounted on the mounting plate, and piston rods are distributed downwards; two electric proportional valves of the electric proportional valve group are respectively connected and communicated with a rodless cavity and a rod cavity of the double-acting cylinder; the top end of the shaft is connected with a piston rod through a floating joint; the bottom end of the shaft is connected with a triaxial force sensor; the pneumatic polishing head is connected with the three-axis force sensor through a coupler. The three-axis force sensor is electrically connected with the controller, and the controller is electrically connected with the electric proportional valve set. The double-acting air cylinder and the two electric proportional valves are adopted, small contact force can be accurately controlled and rapidly adjusted, the requirement for force / heat sensitive characteristics of organic glass and other materials is met, and surface burning is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of robotic automated precision machining, and more particularly to a pneumatic force-controlled actuator, a robot having the same, and a polishing method. Background Art

[0002] In the fields of aerospace and precision optical manufacturing, the polishing of complex-curved transparent parts (such as aircraft cockpit canopies, high-precision lenses) places extremely high requirements on surface integrity and optical performance. Materials represented by polymethyl methacrylate (PMMA) have excellent light transmittance, but are significantly force / heat sensitive. Microscopic contact force exceeding the limit easily causes microcracks, and excessive frictional temperature rise leads to surface softening or even burning. Traditional manual polishing relies on workers' experience, with low efficiency and poor consistency, and it is difficult to meet the large-scale demand for high-precision curved surface machining.

[0003] With the development, although existing robotic polishing technologies have solved the automation problem to a certain extent, some key problems remain unsolved: 1) The control accuracy of microscopic contact force is insufficient. For example, conventional pneumatic actuators use single-acting cylinders or airbags for driving, and are limited by the single-chamber air pressure adjustment range, making it difficult to achieve precise control of microscopic forces at the ±0.5 N level; 2) In the polishing of complex curved surfaces, the component of the tool's gravity changes dynamically with the pose. Existing solutions lack a real-time pose detection and compensation mechanism, resulting in significant contact force fluctuations.

[0004] Therefore, providing a high-precision pneumatic force-controlled actuator, a robot having the same, and a polishing method is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a pneumatic force-controlled actuator, a robot having the same, and a polishing method, which achieve precise control of small contact forces, ensuring that while meeting the processing requirements of the force / heat sensitivity characteristics of polymethyl methacrylate, the polishing efficiency, surface integrity, and optical performance are improved.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A pneumatic force-controlled actuator includes a mounting plate, a double-acting cylinder, an electro-pneumatic proportional valve group, a controller, and a shaft, a floating joint, a three-axis force sensor, and a pneumatic grinding head that are coaxially distributed with the piston rod of the double-acting cylinder. The double-acting cylinder is mounted on the mounting plate with the piston rod facing downward; the two electro-pneumatic proportional valves of the electro-pneumatic proportional valve group are respectively connected and communicated with the rodless cavity and the rod cavity of the double-acting cylinder; the top end of the shaft is connected to the piston rod through the floating joint, and the bottom end of the shaft is connected to the three-axis force sensor; the pneumatic grinding head is connected to the three-axis force sensor through a coupling; the three-axis force sensor is electrically connected to the controller, and the controller is electrically connected to the electro-pneumatic proportional valve group.

[0008] By adopting the above technical solutions, the beneficial effects of the present invention are as follows:

[0009] By using a double-acting cylinder and two electro-pneumatic proportional valves, the small contact force can be precisely controlled and quickly adjusted to meet the requirements of the force / heat sensitive characteristics of materials such as plexiglass, and surface burns can be avoided.

[0010] Furthermore, it further includes a plurality of guide shafts and a support plate. The plurality of guide shafts are circumferentially distributed along the double-acting cylinder and are parallel to the axis. Each guide shaft is connected to the mounting plate through a guide sleeve near the top; the support plate is located between the floating joint and the three-axis sensor, and the support plate is horizontally mounted on the plurality of guide shafts near the bottom through a plurality of linear bearings.

[0011] The beneficial effects produced by adopting the above further technical solutions are that it can limit the radial runout of the shaft, ensure the linearity of the axial movement, withstand the torque generated by the change of the surface curvature during the polishing process, and avoid the jamming of the transmission structure.

[0012] Furthermore, the shaft is a ball spline shaft.

[0013] The beneficial effects produced by adopting the above further technical solutions are that the axial thrust of the cylinder can be accurately transmitted to the polishing tool, and at the same time, the radial torque (such as the lateral force during the polishing process) can be borne by the ball spline structure to prevent the tool from yawing. The ball circulation design enables the repeated accuracy of the axial movement to reach ±0.02 mm, and the force control fluctuation caused by mechanical clearance can be avoided.

[0014] Furthermore, the pneumatic grinding head includes a pneumatic grinding head body and a flexible polishing disc, and the flexible polishing disc is clamped to the pneumatic grinding head body.

[0015] The beneficial effects produced by adopting the above further technical solutions are that it is convenient for the quick switching of sandpapers with different grits.

[0016] A robot includes a robot body and the pneumatic force control actuator as described above, and the mounting plate is installed at the output end of the robot body.

[0017] By adopting the above technical solutions, the beneficial effects of the present invention are as follows:

[0018] The pneumatic force control actuator cooperates with the automatic polishing system of the robot body, which can ensure the stability of the normal contact force during the polishing process, uniform material removal, and greatly improve the surface integrity and optical performance of complex curved transparent parts.

[0019] A polishing method is carried out based on the robot as described above, and includes the following steps:

[0020] 1) The robot body drives the pneumatic force control actuator to move along a preset trajectory. During this process, the three-axis force sensor detects the actual contact force F n (t) in real time. According to the contact force error formula e(t) = F0 - F n (t), e(t) is calculated, where e(t) is the contact force error and F0 is the target contact force;

[0021] 2) According to the PID control equation the controller output signal is obtained, where u(t) is the controller output signal, and k p , k i , k d are the proportional, integral, and differential coefficients respectively;

[0022] 3) The electro-pneumatic proportional valve group receives the control output signal, adjusts the voltage of the electro-pneumatic proportional valve group, adjusts the pressure difference between the rodless chamber and the rod chamber of the double-acting cylinder, and finally adjusts the output force of the double-acting cylinder to make the actual contact force track the target contact force. The equation for the gas flow of the electro-pneumatic proportional valve group and the input voltage is u is the input voltage of the electro-pneumatic proportional valve group, k1 and k2 are the valve body characteristic coefficients, F c is the output force of the double-acting cylinder. The relationship between the output force of the double-acting cylinder and the pressure difference is F c = P d ·A d - P f ·A f , where P d is the pressure in the rodless chamber, P f is the pressure in the rod chamber, A d is the effective cross-sectional area of the rodless chamber, A f is the effective cross-sectional area of the rod chamber. The pressure difference formula between the rodless chamber and the rod chamber is ΔP = P d - P f .

[0023] By adopting the above technical solutions, the beneficial effects of the present invention are as follows:

[0024] Collect the data of the three-axis force sensor, output the control signal to the electro-pneumatic proportional valve group, calculate the contact force error in real time, dynamically adjust the pressure difference ΔP, realize the force control closed loop, and make the actual contact force stable within F0 ± 0.5N of the target contact force. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0026] Figure 1 The accompanying drawing is a schematic diagram of the overall structure of a pneumatic force control actuator provided by the present invention. Specific embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] As Figure 1 shown, the embodiments of the present invention disclose a pneumatic force control actuator, which includes a mounting plate 1, a double-acting cylinder 2, an electro-pneumatic proportional valve group, a controller, and a shaft 3, a floating joint 4, a three-axis force sensor 5, and a pneumatic grinding head 6 that are coaxially distributed with the piston rod of the double-acting cylinder 2. The double-acting cylinder 2 is mounted on the mounting plate 1 with the piston rod facing downward; the two electro-pneumatic proportional valves of the electro-pneumatic proportional valve group are respectively connected and communicated with the rodless cavity and the rod chamber of the double-acting cylinder 2; the top end of the shaft 3 is connected to the piston rod through the floating joint 4, and the floating joint 4 allows a deflection angle of ±2° to compensate for the installation error. The bottom end of the shaft 3 is connected to the three-axis force sensor 5. In this embodiment, the shaft 3 and the three-axis force sensor 5 are connected by a flange; the pneumatic grinding head 6 is connected to the three-axis force sensor 5 through a coupling, and the coupling adopts an elastic plum structure to reduce vibration transmission; the three-axis force sensor 5 is electrically connected to the controller, and the controller is electrically connected to the electro-pneumatic proportional valve group. The present invention uses a double-acting cylinder 2 and two electro-pneumatic proportional valves, which can accurately control and quickly adjust small contact forces, meet the requirements of the force / thermal sensitivity characteristics of materials such as plexiglass, and avoid surface burns.

[0029] It is worth noting that the double-acting cylinder 2 of the present invention is designed with low friction. The specific working principle is as follows: a linear thrust or pull is generated through the pressure difference between the rodless cavity and the rod chamber (the chamber containing the piston rod is called the rod chamber, and the chamber without the piston rod is called the rodless cavity), so as to realize the dynamic adjustment of the polishing contact force. The two chambers are independently adjusted, breaking through the force control range limit of a single chamber, and ±0.5N-level accuracy can be achieved within the air pressure range of 0.1-0.7MPa.

[0030] To further optimize the technical solution of the present invention, it further includes a plurality of guide shafts 7 and a support plate 8. The plurality of guide shafts 7 are circumferentially distributed along the double-acting cylinder 2 and are distributed parallel to the axis. Each guide shaft 7 is connected to the mounting plate 1 through a guide sleeve near the top; the support plate 8 is located between the floating joint 4 and the three-axis sensor 5. The floating joint 4 or the shaft 3 penetrates through the support plate 8, and the support plate 8 is horizontally mounted on the positions near the bottom ends of the plurality of guide shafts 7 through a plurality of linear bearings, which can limit the radial runout of the shaft 3 (≤0.01 mm), ensure the linearity of the axial movement, bear the torque generated by the change of the surface curvature during the polishing process, and prevent the transmission structure from jamming.

[0031] To further optimize the technical solution of the present invention, the shaft 3 is a ball spline shaft, which can accurately transmit the axial thrust of the double-acting cylinder 2 to the polishing tool, and at the same time bear the radial torque (such as the lateral force during the polishing process) through the ball spline structure to prevent the tool from yawing. The ball circulation design enables the repeated accuracy of the axial movement to reach ±0.02 mm, avoiding the force control fluctuation caused by mechanical clearance.

[0032] To further optimize the technical solution of the present invention, the pneumatic grinding head 6 includes a pneumatic grinding head main body and a flexible polishing disc, which drives the flexible polishing disc to rotate, combines with sandpaper or polishing liquid to achieve material removal. The flexible polishing disc is clamped with the pneumatic grinding head main body, facilitating the rapid switching of sandpapers with different grits.

[0033] The embodiment of the present invention also discloses a robot, including a robot body and the above pneumatic force control actuator, and the mounting plate 1 is installed at the output end of the robot body. The pneumatic force control actuator of the present invention cooperates with the automatic polishing system of the robot body, which can ensure the stability of the normal contact force during the polishing process, uniform material removal, and greatly improve the surface integrity and optical performance of complex curved transparent parts.

[0034] The embodiment of the present invention also discloses a polishing method, which is carried out based on the above-mentioned robot, and includes the following steps:

[0035] 1) The robot body drives the pneumatic force control actuator to move along a preset trajectory. During this process, the three-axis force sensor 5 detects the actual contact force F n (t) in real time, and calculates e(t) according to the contact force error formula e(t) = F0 - F n (t), where e(t) is the contact force error and F0 is the target contact force;

[0036] 2) According to the PID control equation Obtain the controller output signal, where u(t) is the controller output signal, k p 、k i 、k d Are the proportional, integral, and differential coefficients respectively;

[0037] 3) The electro-hydraulic proportional valve group receives the control output signal, adjusts the voltage of the electro-hydraulic proportional valve group, adjusts the pressure difference between the rodless chamber and the rod chamber of the double-acting cylinder 2, and finally adjusts the output force of the double-acting cylinder 2 to make the actual contact force track the target contact force. The equation for the gas flow rate of the electro-hydraulic proportional valve group and the input voltage is where u is the input voltage of the electro-hydraulic proportional valve group, k1 and k2 are the valve body characteristic coefficients, and F c is the output force of the double-acting cylinder. The relationship between the output force of the double-acting cylinder and the pressure difference is F c = P d ·A d - P f ·A f , where P d is the air pressure in the rodless chamber, P f is the air pressure in the rod chamber, A d is the effective cross-sectional area of the rodless chamber, and A f is the effective cross-sectional area of the rod chamber. The formula for the air pressure difference between the rodless chamber and the rod chamber is ΔP = P d - P f .

[0038] The present invention collects the data of the three-axis force sensor 5, outputs the control signal to the electro-hydraulic proportional valve group, calculates the contact force error in real time, and dynamically adjusts the pressure difference ΔP to achieve a force control closed loop (the pressure difference ΔP is dynamically adjusted by the electro-hydraulic proportional valve group, which directly affects the cylinder output force Fc; at the same time, the change rate of the output force is fed back to the pressure difference adjustment process to form a closed-loop control), so that the actual contact force is stabilized within F0±0.5N of the target contact force.

[0039] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0040] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aerodynamic control actuator, characterized in that, It includes a mounting plate, a double-acting cylinder, an electro-pneumatic proportional valve group, a controller, and a shaft, a floating joint, a three-axis force sensor, and a pneumatic grinding head that are coaxially distributed with the piston rod of the double-acting cylinder. The double-acting cylinder is mounted on the mounting plate with the piston rod facing downwards. Two electro-pneumatic proportional valves of the electro-pneumatic proportional valve group are respectively connected and communicated with the rodless cavity and the rod chamber of the double-acting cylinder. The top end of the shaft is connected to the piston rod through the floating joint, and the bottom end of the shaft is connected to the three-axis force sensor. The pneumatic grinding head is connected to the three-axis force sensor through a coupling. The three-axis force sensor is electrically connected to the controller, and the controller is electrically connected to the electro-pneumatic proportional valve group.

2. The pneumatic force-controlled actuator according to claim 1, characterized in that, It further includes a plurality of guide shafts and a support plate. The plurality of guide shafts are circumferentially distributed along the double-acting cylinder and are parallel to the shaft. Each guide shaft is connected to the mounting plate through a guide sleeve near the top end. The support plate is located between the floating joint and the three-axis sensor, and the support plate is horizontally mounted on the positions near the bottom ends of the plurality of guide shafts through a plurality of linear bearings.

3. The pneumatic force-controlled actuator according to claim 1 or 2, characterized in that, The shaft is a ball spline shaft.

4. The pneumatic force-controlled actuator according to claim 3, characterized in that, The pneumatic grinding head includes a pneumatic grinding head body and a flexible polishing disc, and the flexible polishing disc is snap-connected to the pneumatic grinding head body.

5. A robot, characterized in that, It includes a robot body and the pneumatic force-controlled actuator according to any one of claims 1-4, and the mounting plate is mounted on the output end of the robot body.

6. A polishing method, which is carried out based on the robot as described in claim 5, characterized in that, It includes the following steps: 1) The robot body drives the pneumatic force control actuator to move along a preset trajectory. During this process, the triaxial force sensor continuously detects the actual contact force F n (t), and calculates e(t) according to the contact force error formula e(t) = F0 - F n (t), where e(t) is the contact force error and F0 is the target contact force; 2) According to the PID control equation the controller output signal is obtained, where u(t) is the controller output signal, and k p , k i , k d are the proportional, integral, and derivative coefficients respectively; 3) The electro-hydraulic proportional valve group receives the control output signal, adjusts the voltage of the electro-hydraulic proportional valve group, adjusts the pressure difference between the rodless chamber and the rod chamber of the double-acting cylinder, and finally adjusts the output force of the double-acting cylinder to make the actual contact force track the target contact force. The equation of the gas flow rate of the electro-hydraulic proportional valve group and the input voltage is u is the input voltage of the electro-hydraulic proportional valve group, k1 and k2 are the valve body characteristic coefficients, F c is the output force of the double-acting cylinder. The relationship between the output force of the double-acting cylinder and the pressure difference is F c =P d ·A d -P f ·A f , where P d is the pressure in the rodless chamber, P f is the pressure in the rod chamber, A d is the effective cross-sectional area of the rodless chamber, A f is the effective cross-sectional area of the rod chamber. The formula for the pressure difference between the rodless chamber and the rod chamber is ΔP = P d -P f .

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