A damping coefficient testing device and method for an independently supplied air-floating frictionless cylinder capable of generating eddy current damping

Abstract

The present invention provides a damping coefficient test device for an independently supplied air-floating frictionless cylinder capable of generating eddy current damping, comprising an independently supplied air-floating frictionless cylinder, a laser displacement sensor, an air supply system and a control system. The air supply system ventilates the air-floating piston and the inner cavity of the air bearing, and forms an air pressure bearing film between the air-floating piston and the inner wall of the cylinder, and between the air bearing and the piston rod to eliminate friction. A permanent magnet is installed in the cylinder, and the eddy current generated by the magnet is used to reduce vibration. During the test, the piston rod-air-floating piston assembly in the cylinder falls freely, and there is no contact between the assembly and the inner wall of the cylinder barrel, and it is only subjected to eddy current damping force, which increases with the acceleration of the falling speed. When the damping force is equal to the gravity, the assembly reaches a uniform speed state; the damping coefficient can be calculated using the speed and the gravity of the assembly. The present invention uses this non-contact eddy current damping force to replace the friction force of the cylinder, which greatly improves the servo control accuracy of the cylinder, is simple to operate, and has accurate test results.

Description

Technical Field

[0001] The invention relates to the technical field of cylinders, and in particular to a damping coefficient testing device and method for an independently air-supplied air-floating frictionless cylinder capable of generating eddy current damping. Background Art

[0002] Pneumatic technology is widely used in many fields such as industrial production and automation due to its advantages such as simple structure, easy maintenance, low cost, clean and pollution-free. The cylinder is the most common actuator in the pneumatic system. However, during the movement of the cylinder, friction will inevitably be introduced due to the presence of the sealing ring. The complexity and uncertainty of friction will make it difficult to perform high-precision output force servo control of the cylinder; the negative damping characteristics of friction at low speed will lead to low position servo control accuracy of the cylinder at low speed. Therefore, finding another form of force that can replace friction to provide a stable shock-absorbing effect to the cylinder is a direction worth exploring.

[0003] In recent years, as the principle of gas hydrostatic lubrication has been applied to cylinders, a variety of air-suspended frictionless cylinders with different structures have been proposed. For example, the Chinese utility model patent with application number 201721624619.5 discloses a universal double-acting air-floating frictionless cylinder, which relies on an air bearing and a self-designed hollow piston with multiple symmetrically distributed throttle holes to achieve frictionless motion of the cylinder. Although this can achieve high-precision output force servo control of the cylinder, due to the lack of damping, the cylinder will produce undesirable vibrations during the position servo control process, making its position control accuracy low. For this reason, the Chinese invention patents with application numbers 201810960129.5 and 201810960472.X disclose two different types of friction-controllable cylinders. On the basis of the frictionless cylinder, a cylinder with controllable friction and friction size is realized by using the expansion and contraction of the airbag. However, this direct contact form of friction is difficult to apply accurately. Although this method can improve the position servo control of the frictionless cylinder to a certain extent, the control accuracy is still a difficult technical problem to overcome. Summary of the invention

[0004] In view of the shortcomings in the prior art, the present invention adds damping to the air-floating cylinder and replaces the unstable friction in the traditional cylinder with stable damping, which can avoid the uncertainty of the friction between the piston and the cylinder in the traditional cylinder and avoid the oscillation of the cylinder during the movement after the frictionless cylinder is realized in the existing air-floating cylinder. However, the system damping will affect the vibration isolation efficiency. The greater the damping, the more energy the cylinder loses. When the damping is very small, the impact on the vibration isolation efficiency is not much different from that when there is no damping. Based on this, the present invention provides a damping coefficient test device and method for an independent air-supplied air-floating frictionless cylinder that can generate eddy current damping to detect the size of the added damping coefficient and observe whether the shock absorption effect meets the working condition requirements. The present invention eliminates the influence of friction by forming a high-pressure bearing film through independent air supply, and at the same time adds a pair of permanent magnet modules to the original air-floating cylinder structure, and uses the damping force generated by it to replace the friction with low control accuracy for shock absorption, avoiding the uncertainty of friction, greatly improving the position control accuracy of the cylinder, and designs a simple damping coefficient test device for the cylinder.

[0005] A damping coefficient testing device for an independent air supply air floating frictionless cylinder capable of generating eddy current damping, comprising an independent air supply air floating frictionless cylinder, a laser displacement sensor, an air supply system and a control system;

[0006] The independent air supply air-floating frictionless cylinder is installed on a vertical mounting platform, and includes a piston rod, an air bearing, a front end cover, a cylinder barrel, a permanent magnet module, an air-floating piston, a conical spiral air pipe, a rear end cover and a piston front cover; the front end cover and the rear end cover are respectively installed at both ends of the cylinder barrel, and the piston rod passes through the front end cover and extends into the cylinder barrel. The air bearing is installed between the piston rod and the front end cover, and a gap is left between the air bearing and the piston rod. A second air inlet that penetrates the inner cavity of the air bearing is opened on the front end cover, and a plurality of throttling holes that radially penetrate the bearing wall are evenly distributed on the circumferential wall of the air bearing; The rear end cover is provided with a first air inlet connected to the air supply system, and the first air inlet is connected to the air inlet hole at the rear end of the air-floating piston by a conical spiral air pipe; a gap is left between the air-floating piston and the cylinder barrel, and a number of throttle holes radially penetrating the piston wall are evenly distributed on the circumferential wall of the air-floating piston, and the piston front cover is fixedly installed at the front end of the air-floating piston; the piston front cover is movably connected to the piston rod; the permanent magnet module is fixed on both sides of the piston front cover or inside the air-floating piston; the rear end cover is provided with a rodless cavity air port penetrating the end wall, and the front end cover is provided with a rod cavity air port penetrating the end wall;

[0007] The outer circumferential wall of the air-floating piston is provided with a plurality of internal channels three, and annular pressure relief grooves are provided at both ends; an axial internal channel two connected to the internal channel three is provided inside the piston front cover; an axial internal channel one is provided inside the piston rod, one end of the internal channel one is connected to the internal channel two through an air pipe, and the other end is connected to the atmosphere; the gas in the air-floating piston flows to the pressure relief grooves at both ends of the air-floating piston through the throttle hole, and is discharged to the atmosphere through the internal channel three, the internal channel two, the air pipe and the internal channel one in sequence;

[0008] The control system includes a computer, a data acquisition card, a PWM signal generator and a switch valve; the switch valve is used to control the on-off of the rodless cavity air port, the rod cavity air port and the atmosphere, and the computer controls the on-off of the switch valve via the data acquisition card and the PWM signal generator;

[0009] The laser displacement sensor is mounted on a vertical mounting platform, and the laser emitted by the laser displacement sensor can be irradiated on the end surface of the piston rod; the position information on the laser displacement sensor is transmitted to the computer via the A / D port of the data acquisition card;

[0010] The air supply system includes an air source and a pressure-stabilizing air tank. The pressure-stabilizing air tank is connected to the first air inlet and the second air inlet. The compressed air generated by the air source is transported to the inner cavity of the air bearing and the air floating piston through the pressure-stabilizing air tank.

[0011] Furthermore, the gas supply system also includes a filter and a proportional directional valve which are sequentially arranged between the gas source and the pressure-stabilizing gas tank along the gas transmission direction, and a pressure sensor responsible for collecting the air pressure information in the pressure-stabilizing gas tank; the compressed air generated by the gas source passes through the filter and the proportional directional valve and then enters the pressure-stabilizing gas tank; the pressure sensor transmits the collected information to the computer via the A / D port of the data acquisition card, and the computer adjusts the proportional directional valve via the D / A port of the data acquisition card, thereby regulating the air pressure value in the pressure-stabilizing gas tank.

[0012] Furthermore, the gas supply system also includes a filter and a precision pressure reducing valve which are sequentially arranged between the gas source and the pressure-stabilizing gas tank along the gas transmission direction. The precision pressure reducing valve is responsible for directly adjusting the pressure of the filtered gas to a set value before passing it into the pressure-stabilizing gas tank.

[0013] Furthermore, the switch valve is divided into a normally closed high-speed switch valve one and a normally closed high-speed switch valve two. The rodless chamber air port of the independent air-supply air-floating frictionless cylinder is connected to the normally closed high-speed switch valve one, and the rod chamber air port is directly connected to the atmosphere; or the rod chamber air port of the independent air-supply air-floating frictionless cylinder is connected to the normally closed high-speed switch valve two, and the rodless chamber air port is directly connected to the atmosphere; or the rod chamber air port and the rodless chamber air port of the independent air-supply air-floating frictionless cylinder are respectively connected to the normally closed high-speed switch valve two and the normally closed high-speed switch valve one.

[0014] Furthermore, the permanent magnet module is axially magnetized, radially magnetized, or has a Halbach array structure.

[0015] Furthermore, the piston front cover and the piston rod are movably connected via a ball joint.

[0016] Furthermore, the piston rod, the air-floating piston, the piston front cover and the ball joint are all made of non-magnetic metal materials.

[0017] Furthermore, both ends of the independent air supply air floating frictionless cylinder are clamped by two fixing frames respectively, and the fixing frames are fixed on the vertical mounting platform by bolts.

[0018] The testing method of the damping coefficient testing device of the air-floating frictionless cylinder with independent air supply capable of generating eddy current damping based on any one of the above items is characterized by comprising the following steps:

[0019] Step 1: Install the front end of the piston rod in the independent air-supply air-floating frictionless cylinder vertically downward in a detachable manner on the vertical mounting table. The laser displacement sensor is installed directly below the piston rod so that the laser emitted by the laser head can irradiate the end face of the piston rod. The pressure-stabilizing gas tank starts to ventilate the air bearing and the inner cavity of the air-floating piston. The computer controls the opening of the switch valve through the data acquisition card and the PWM signal generator.

[0020] Step 2: Manually push the piston rod-air floating piston assembly to the rear end cover, and then let it fall freely. The laser displacement sensor detects and records the position information in real time, and the position information is transmitted to the computer through the A / D port of the data acquisition card;

[0021] Step 3: Set a displacement warning distance. When the laser displacement sensor detects that the displacement of the piston rod-air floating piston assembly is greater than the displacement warning distance, the computer issues a command to close the switch valve.

[0022] Step 4: The position information of the piston rod-air floating piston assembly is obtained through the laser displacement sensor. The speed at the uniform speed stage can be calculated using the time information monitored by the computer, and the eddy current damping coefficient can be calculated based on the gravity of the piston rod-air floating piston assembly.

[0023] The testing method of the damping coefficient testing device of the air-floating frictionless cylinder with independent air supply capable of generating eddy current damping based on any one of the above items is characterized by comprising the following steps:

[0024] Step 1: Install the front end of the piston rod in the independent air-supply air-floating frictionless cylinder vertically upward and detachably on the vertical mounting table. Install the laser displacement sensor directly above the piston rod so that the laser emitted by the laser head can irradiate the end face of the piston rod. The pressure-stabilizing gas tank starts to ventilate the air bearing and the inner cavity of the air-floating piston. The computer controls the opening of the switch valve through the data acquisition card and the PWM signal generator.

[0025] Step 2: Manually push the piston rod-air floating piston assembly to the rear end cover, and then let it fall freely. The laser displacement sensor detects and records the position information in real time, and the position information is transmitted to the computer through the A / D port of the data acquisition card;

[0026] Step 3: Set a displacement warning distance. When the laser displacement sensor detects that the displacement of the piston rod-air floating piston assembly is greater than the displacement warning distance, the computer issues a command to close the switch valve.

[0027] Step 4: The position information of the piston rod-air floating piston assembly is obtained through the laser displacement sensor. The speed at the uniform speed stage can be calculated using the time information monitored by the computer, and the eddy current damping coefficient can be calculated based on the gravity of the piston rod-air floating piston assembly.

[0028] The principle of the present invention is as follows: when the cylinder is working, the pressure-stabilizing gas tank continuously ventilates the air-floating piston and the air bearing inner cavity, and the air entering the air-floating piston inner cavity generates a high-pressure bearing air film between the air-floating piston and the inner wall of the cylinder barrel through the throttle hole, so that there is no contact between the air-floating piston and the inner wall of the cylinder barrel, thereby achieving friction-free. Similarly, the pressure-stabilizing gas tank ventilates the air bearing inner cavity through the second air inlet of the air bearing, and the air generates a high-pressure bearing air film between the air bearing and the piston rod through the throttle hole, so that there is no contact between the piston rod and the air bearing, thereby achieving friction-free.

[0029] When the piston rod-air floating piston assembly drives the permanent magnet module to descend inside the cylinder, an induced current will be generated on the cylinder to form an induced magnetic field, thereby generating an eddy current damping force that hinders relative motion. In this way, the piston rod-air floating piston assembly eliminates the influence of friction when it moves, and is only affected by eddy current damping force and gravity. As the falling speed increases, the damping force on the piston rod-air floating piston assembly gradually increases. When the damping force is equal to the gravity of the assembly, the assembly enters the uniform motion stage, and the gravity it is subjected to is equal to the damping force. At this time, the damping force is equal to the product of the damping coefficient and the speed. Therefore, it is only necessary to measure the gravity of the assembly and the speed of the uniform motion stage to obtain the damping coefficient.

[0030] The beneficial effects of the present invention are:

[0031] 1. The present invention ventilates the inner cavity of the air-floating piston and the air bearing, thereby generating a high-pressure bearing air film between the air-floating piston and the inner wall of the cylinder barrel, and between the air bearing and the piston rod, thereby avoiding direct contact between the air-floating piston and the inner wall of the cylinder barrel, and between the piston rod and the air bearing, and eliminating the uncertainty of the friction between the piston and the cylinder barrel in the traditional cylinder.

[0032] 2. The present invention installs a permanent magnet module inside the cylinder and utilizes the eddy current generated during its falling process to absorb the vibration energy generated during the movement, thereby reducing the vibration. At the same time, the permanent magnet module of the present invention is axially magnetized, radially magnetized, or a Halbach array structure, which can generate the strongest magnetic field with the least amount of magnets, simplify the structure, and maximize the shock absorption efficiency, thereby realizing high-precision servo control of the cylinder.

[0033] 3. The present invention has designed an air supply system separately for the air-floating frictionless cylinder, which filters out tiny particles in the compressed air through a filter to avoid blockage of the throttle holes of the air bearing and the air-floating piston; the air pressure of the compressed air can be adjusted through the precision pressure reducing valve / proportional directional valve, the pressure-stabilizing gas tank and the pressure sensor. As the air pressure increases, the air pressure between the air-floating piston and the inner wall of the cylinder barrel, and between the piston rod and the air bearing also increases accordingly, thereby generating a high-pressure bearing air film with better isolation effect and achieving friction-free operation more stably.

[0034] 4. When the displacement of the piston rod-air floating piston assembly of the present invention is greater than the warning distance, the computer closes the normally closed high-speed switch valve 1 and the normally closed high-speed switch valve 2, the inner cavity of the cylinder is in a sealed state, and the assembly continues to descend under the action of gravity. At this time, the gas below the air floating piston is compressed, which exerts an upward lifting force on the air floating piston, and the gas above the air floating piston is stretched, which exerts an upward tensile force on the air floating piston. Moreover, since the gap between the air floating piston and the inner wall of the cylinder is very small, the gas at the front and rear ends of the air floating piston is almost not circulated, and both of them play a buffering role on the falling assembly at the same time. When the rod cavity air port or the rodless cavity air port is directly connected to the atmosphere, a single lifting force or tensile force can also play a buffering role on the falling assembly, protecting the internal structure from collision damage. This buffering method is simple and efficient, and no additional buffering device is required. The buffering distance can be manually adjusted, and the gas responsible for buffering can be directly discharged to the atmosphere without causing environmental pollution.

[0035] 5. The damping coefficient testing device of the independently air-supplied air-floating frictionless cylinder capable of generating eddy current damping described in the present invention uses a laser displacement sensor to detect the speed of the piston rod-air-floating piston assembly when it enters the uniform falling stage and the gravity of the assembly to obtain the damping coefficient. The operation is simple and easy to implement, and the test results are accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the front view cross-sectional structure of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to the present invention;

[0037] Figure 2 It is a schematic diagram of the top view and cross-sectional structure of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to the present invention;

[0038] Figure 3It is a schematic diagram of the overall structure of the damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to the present invention;

[0039] Figure 4 The figure is a flow chart of the air pressure control in the pressure-stabilizing gas tank of the present invention.

[0040] In the figure: 1-piston rod; 2-air bearing; 3-front cover; 4-cylinder; 5-permanent magnet module; 6-air floating piston; 7-throttle hole; 8-conical spiral air pipe; 9-rear cover; 10-internal channel one; 11-ball joint; 12-air pipe; 13-internal channel two; 14-piston front cover; 15-internal channel three; 16-independent air supply air floating frictionless cylinder; 17-fixed frame; 18-vertical mounting table; 19-laser displacement sensor; 20-computer; 21-data acquisition card; 22-PWM signal generator; 23-air source; 24-filter; 25-precision pressure reducing valve; 26-proportional directional valve; 27-pressure stabilizing gas tank; 28-pressure sensor; 29-normally closed high-speed switching valve one; 30-normally closed high-speed switching valve two; 31-rod cavity air port; 32-rodless cavity air port; 33-first air inlet; 34-second air inlet. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the specific implementation modes of the accompanying drawings, but the protection scope of the present invention is not limited thereto.

[0042] Embodiment 1:

[0043] like Figures 1 to 3 As shown, the damping coefficient testing device of the air-floating frictionless cylinder with independent air supply capable of generating eddy current damping of the present invention comprises an air-floating frictionless cylinder 16, a laser displacement sensor 19, an air supply system and a control system.

[0044] The two ends of the air-floating frictionless cylinder 16 are clamped by two fixing frames 17 respectively, and the fixing frames 17 are fixed on the vertical mounting platform 18 by bolts. The air-floating frictionless cylinder 16 includes a "T"-shaped piston rod 1, an air bearing 2, a front end cover 3, a cylinder barrel 4, a permanent magnet module 5, an air-floating piston 6, a conical spiral air pipe 8, a rear end cover 9 and a piston front cover 14; the front end cover 3 and the rear end cover 9 are respectively installed at the two ends of the cylinder barrel 4, the piston rod 1 passes through the front end cover 3 and extends into the cylinder barrel 4, the air bearing 2 is installed between the piston rod 1 and the front end cover 3, and a gap is left between the air bearing 2 and the piston rod 1. A second air inlet 34 that penetrates the inner cavity of the air bearing 2 is opened on the front end cover 3, and a plurality of throttle holes 7 that radially penetrate the bearing wall are evenly distributed on the circumferential wall of the air bearing 2. The air supply system ventilates the inner cavity of the air bearing 2 through the second air inlet 34, so as to achieve no contact between the piston rod 1 and the air bearing 2, so as to achieve no friction. The rear end cover 9 is provided with a first air inlet 33 connected to the air supply system, and the first air inlet 33 is connected to the air inlet hole at the rear end of the air-floating piston 6 by a conical spiral air pipe 8; a gap is left between the air-floating piston 6 and the cylinder 4, and a plurality of throttle holes 7 radially penetrating the piston wall are evenly distributed on the circumferential wall of the air-floating piston 6. The air supply system ventilates the inner cavity of the air-floating piston 6 through the conical spiral air pipe 8, and a high-pressure bearing air film is generated between the tiny gaps through the action of the throttle holes 7, so that there is no contact between the air-floating piston 6 and the inner wall of the cylinder 4, thereby achieving friction-free. The piston front cover 14 is fixedly installed on the front end of the air-floating piston 6 by means of threads; the piston front cover 14 and the piston rod 1 are movably connected by means of a ball joint 11, and the center of gravity of the piston front cover 14, the piston rod 1 and the air-floating piston 6 are on the same axis, thus solving the coaxiality problem of the piston rod 1 and the air-floating piston 6, and in order to prevent the magnetic field generated by the permanent magnet module 5 from being affected, the piston rod 1, the air-floating piston 6, the piston front cover 14 and the ball joint 11 are all made of non-magnetic metal materials; the permanent magnet module 5 is fixed on both sides of the piston front cover 14 or inside the air-floating piston 6, and is axially magnetized, radially magnetized, or has a Halbach array structure, and this arrangement is to generate the strongest magnetic field with the least amount of magnets; the rear end cover 9 is provided with a rodless cavity air port 32 penetrating the end wall, and the front end cover 3 is provided with a rod cavity air port 31 penetrating the end wall;

[0045] A plurality of internal channels 3 15 are provided on the outer circumferential wall of the air-floating piston 6, and annular pressure relief grooves are provided at both ends; an axial internal channel 2 13 connected to the internal channel 3 15 is provided inside the piston front cover 14; an axial internal channel 10 is provided inside the piston rod 1, one end of the internal channel 10 is connected to the internal channel 2 13 through the air pipe 12, and the other end is connected to the atmosphere; the gas in the air-floating piston 6 flows to the pressure relief grooves at both ends of the air-floating piston 6 through the throttle hole 7, and is discharged to the atmosphere through the internal channel 3 15, the internal channel 2 13, the air pipe 12 and the internal channel 10 in turn.

[0046] The control system includes a computer 20, a data acquisition card 21, a PWM signal generator 22, a normally closed high-speed switch valve 1 29 and a normally closed high-speed switch valve 2 30; the rod chamber air port 31 and the rodless chamber air port 32 of the independent air supply air floating frictionless cylinder 16 are respectively connected to the normally closed high-speed switch valve 2 30 and the normally closed high-speed switch valve 1 29, and the computer 20 controls the on and off of the switch valve via the data acquisition card 21 and the PWM signal generator 22.

[0047] The laser displacement sensor 19 is detachably mounted on the vertical mounting platform 18 , and the laser emitted by the laser displacement sensor 19 can irradiate the end face of the piston rod 1 ; the position information on the laser displacement sensor 19 is transmitted to the computer 20 via the A / D port of the data acquisition card 21 .

[0048] The gas supply system includes an air source 23, a filter 24, a proportional directional valve 26, a pressure-stabilizing gas tank 27 and a pressure sensor 28. The pressure-stabilizing gas tank 27 is connected to the first air inlet 33 and the second air inlet 34. The filter 24 and the proportional directional valve 26 are arranged between the air source 23 and the pressure-stabilizing gas tank 27 in sequence along the gas transmission direction. The pressure sensor 28 is arranged between the pressure-stabilizing gas tank 27 and the data acquisition card 21. The compressed air generated by the air source 23 passes through the filter 24 and the proportional directional valve 26 and then enters the pressure-stabilizing gas tank 27. The pressure sensor 28 is responsible for collecting the pressure information in the pressure-stabilizing gas tank 27 and transmitting the information to the computer 20 via the A / D port of the data acquisition card 21. The computer 20 adjusts the proportional directional valve 26 via the D / A port of the data acquisition card 21, thereby regulating the air pressure value in the pressure-stabilizing gas tank. Its control block diagram is shown as follows: Figure 4 As shown, this method ensures that the pressure-stabilizing gas tank 27 connected to the air bearing 2 and the air floating piston 6 has a stable pressure, so that the air bearing 2 and the air floating piston 6 can work normally.

[0049] The damping coefficient test method is as follows: when the front end of the piston rod 1 of the independently air-supplied air-floating frictionless cylinder 16 is installed vertically downward, the laser displacement sensor 19 is installed directly below the piston rod 1, so that the laser emitted by the laser head can irradiate the end face of the piston rod 1. When the pressure-stabilizing gas tank 27 ventilates the air bearing 2 and the air-floating piston 6, the computer 20 controls the opening of the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30 through the data acquisition card 21 and the PWM signal generator 22, and pushes the piston rod 1-air-floating piston 6 assembly to the rear end cover 9, and then allows it to fall freely. The laser displacement sensor 19 detects and records the position information in real time, and the position information is transmitted to the computer 20 through the A / D port of the data acquisition card 21. In order to avoid the collision between the head of the piston rod 1 and the front cover 3, the maximum buffer distance required by the piston rod 1 is first measured, and a displacement warning distance is set for the piston rod 1-air floating piston 6 assembly in combination with the distance between the front cover 3 and the rear cover 9. When the displacement of the piston rod 1-air floating piston 6 assembly is detected to be greater than the displacement warning distance, the computer 20 issues an instruction to close the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30. At this time, the gas below the air floating piston 6 is compressed, exerting an upward lifting force on the air floating piston 6, and the gas above the air floating piston 6 is stretched, exerting an upward stretching force on the air floating piston 6. Both of them play a buffering role on the falling assembly. By identifying the speed in the uniform speed stage in the position information, the eddy current damping coefficient can be calculated according to the gravity of the piston rod 1-air floating piston 6 assembly.

[0050] The principle of the present invention is as follows:

[0051] When the piston rod 1-air floating piston 6 assembly drives the permanent magnet module 5 to descend inside the cylinder 4, an induced current will be generated on the cylinder 4 to form an induced magnetic field, thereby generating an eddy current damping force that hinders relative motion. In this way, the piston rod 1-air floating piston 6 assembly eliminates the influence of friction when it moves, and is only affected by the eddy current damping force. As the falling speed increases, the damping force on the piston rod 1-air floating piston 6 assembly gradually increases. When the damping force is equal to the gravity of the assembly, the assembly enters the uniform motion stage. The damping coefficient can be obtained by measuring the gravity of the assembly and the speed of the uniform motion stage.

[0052] Embodiment 2

[0053] Based on the damping coefficient test device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping described in Example 1, this embodiment installs the front end of the piston rod 1 of the independent air supply air floating frictionless cylinder 16 vertically upward, and the overall structure remains unchanged, but there are some differences in the specific test method. The test method of this embodiment is as follows:

[0054] The front end of the piston rod 1 of the independent air supply air-floating frictionless cylinder 16 is installed vertically upward, and the laser displacement sensor 19 is detachably installed on the vertical mounting platform 18 and is located directly above the piston rod 1. The laser emitted by the laser displacement sensor 19 can irradiate the end face of the piston rod 1. When the pressure-stabilizing gas tank 27 ventilates the air bearing 2 and the air-floating piston 6, the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30 are opened, and the piston rod 1-air-floating piston 6 assembly is pushed to the front end cover 3, and then it is allowed to fall freely. The laser displacement sensor 19 detects and records the position information in real time. In order to avoid the collision between the tail of the air-floating piston 6 and the rear end cover 9, the maximum buffer distance required by the air-floating piston 6 is first measured, and a displacement warning distance is set for the piston rod 1-air-floating piston 6 assembly in combination with the distance between the front end cover 3 and the rear end cover 9. When it is detected that the displacement of the piston rod 1-air-floating piston 6 assembly is greater than the displacement warning distance, the computer 20 issues an instruction to close the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30 to play a buffering role. By identifying the speed at the uniform speed stage in the position information, the eddy current damping coefficient can be calculated based on the gravity of the piston rod 1-air floating piston 6 assembly.

[0055] Embodiment 3

[0056] Based on the damping coefficient test device of the independent air supply air-floating frictionless cylinder capable of generating eddy current damping described in Example 1, this embodiment connects the rodless cavity air port 32 of the air-floating frictionless cylinder 16 to the normally closed high-speed switch valve 29, and the rod cavity air port 31 is directly connected to the atmosphere, and the rest of the structure remains unchanged. The test method of this embodiment is as follows:

[0057] When the front end of the piston rod 1 of the independently supplied air-floating frictionless cylinder 16 is installed vertically downward, the laser displacement sensor 19 is installed directly below the piston rod 1, so that the laser emitted by the laser head can irradiate the end face of the piston rod 1. When the pressure-stabilizing gas tank 27 ventilates the air bearing 2 and the air-floating piston 6, the computer 20 controls the opening of the normally closed high-speed switch valve 29 through the data acquisition card 21 and the PWM signal generator 22, pushes the piston rod 1-air-floating piston 6 assembly to the rear end cover 9, and then allows it to fall freely. The laser displacement sensor 19 detects and records the position information in real time, and the position information is transmitted to the computer 20 through the A / D port of the data acquisition card 21. In order to avoid the collision between the head of the piston rod 1 and the front cover 3, the maximum buffer distance required by the piston rod 1 is first measured, and a displacement warning distance is set for the piston rod 1-air floating piston 6 assembly in combination with the distance between the front cover 3 and the rear cover 9. When the displacement of the piston rod 1-air floating piston 6 assembly is detected to be greater than the displacement warning distance, the computer 20 issues an instruction to close the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30. At this time, the air pressure below the air floating piston 6 remains unchanged, and the gas above the air floating piston 6 is stretched, which exerts an upward stretching force on the air floating piston 6 and can also play a buffering role on the falling assembly. By identifying the speed in the uniform speed stage in the position information, the eddy current damping coefficient can be calculated according to the gravity of the piston rod 1-air floating piston 6 assembly.

[0058] Embodiment 4

[0059] Based on the damping coefficient test device of the independent air supply air-floating frictionless cylinder capable of generating eddy current damping described in Example 1, the rod cavity air port 31 of the air-floating frictionless cylinder 16 is connected to the normally closed high-speed switch valve 2 30, and the rodless cavity air port 32 is directly connected to the atmosphere, and the rest of the structure remains unchanged. The test method of this embodiment is as follows:

[0060] When the front end of the piston rod 1 of the independently air-supplied air-floating frictionless cylinder 16 is installed vertically downward, the laser displacement sensor 19 is installed directly below the piston rod 1, so that the laser emitted by the laser head can irradiate the end face of the piston rod 1. When the pressure-stabilizing gas tank 27 ventilates the air bearing 2 and the air-floating piston 6, the computer 20 controls the opening of the normally closed high-speed switch valve 2 30 through the data acquisition card 21 and the PWM signal generator 22, pushes the piston rod 1-air-floating piston 6 assembly to the rear end cover 9, and then allows it to fall freely. The laser displacement sensor 19 detects and records the position information in real time, and the position information is transmitted to the computer 20 through the A / D port of the data acquisition card 21. In order to avoid the collision between the head of the piston rod 1 and the front cover 3, the maximum buffer distance required by the piston rod 1 is first measured, and a displacement warning distance is set for the piston rod 1-air floating piston 6 assembly in combination with the distance between the front cover 3 and the rear cover 9. When the displacement of the piston rod 1-air floating piston 6 assembly is detected to be greater than the displacement warning distance, the computer 20 issues an instruction to close the normally closed high-speed switch valve 1 29 and the normally closed high-speed switch valve 2 30. At this time, the gas under the air floating piston 6 is compressed, which exerts an upward lifting force on the air floating piston 6. The air pressure above the air floating piston 6 remains unchanged, and a single force can also play a buffering role on the falling assembly. By identifying the speed in the uniform speed stage in the position information, the eddy current damping coefficient can be calculated according to the gravity of the piston rod 1-air floating piston 6 assembly.

[0061] Embodiment 5

[0062] Based on the damping coefficient testing device of the independently air-supplied air-floating frictionless cylinder capable of generating eddy current damping described in Example 1, a precision pressure reducing valve 25 is used to replace the constant pressure control system composed of the proportional directional valve 26, the pressure-stabilizing gas tank 27 and the pressure sensor 28, and the rest of the structure and testing method remain unchanged.

[0063] The gas supply system includes an air source 23, a filter 24, a precision pressure reducing valve 25 and a pressure-stabilizing gas tank 27. The pressure-stabilizing gas tank 27 is connected to the first air inlet 33 and the second air inlet 34. The filter 24 and the precision pressure reducing valve 25 are sequentially arranged between the air source 23 and the pressure-stabilizing gas tank 27 along the gas transmission direction. The compressed air generated by the air source 23 is passed through the filter 24 and the precision pressure reducing valve 25 to adjust the gas pressure to a set value and then enter the pressure-stabilizing gas tank 27.

[0064] The examples are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A damping coefficient test device for an independently supplied air-floating frictionless cylinder capable of generating eddy current damping, characterized in that: It comprises an independent air supply air-floating frictionless cylinder (16), a laser displacement sensor (19), an air supply system and a control system; The independent air supply air-floating frictionless cylinder (16) is installed on a vertical mounting platform (18), and comprises a piston rod (1), an air bearing (2), a front end cover (3), a cylinder barrel (4), a permanent magnet module (5), an air-floating piston (6), a conical spiral air pipe (8), a rear end cover (9) and a piston front cover (14); the front end cover (3) and the rear end cover (9) are respectively installed at the two ends of the cylinder barrel (4), the piston rod (1) passes through the front end cover (3) and extends into the cylinder barrel (4), the air bearing (2) is installed between the piston rod (1) and the front end cover (3), a gap is left between the air bearing (2) and the piston rod (1), a second air inlet (34) penetrating to the inner cavity of the air bearing (2) is opened on the front end cover (3), and a plurality of radially penetrating bearing wall are evenly distributed on the circumferential wall of the air bearing (2). The throttle hole (7) of the air-floating piston (6) is provided on the rear end cover (9) with a first air inlet (33) connected to the air supply system, and the first air inlet (33) is connected to the air inlet hole at the rear end of the air-floating piston (6) by a conical spiral air pipe (8); a gap is left between the air-floating piston (6) and the cylinder barrel (4), and a plurality of throttle holes (7) radially penetrating the piston wall are evenly distributed on the circumferential wall of the air-floating piston (6); the piston front cover (14) is fixedly mounted on the front end of the air-floating piston (6); the piston front cover (14) is movably connected to the piston rod (1); the permanent magnet module (5) is fixed on both sides of the piston front cover (14) or inside the air-floating piston (6); the rear end cover (9) is provided with a rodless cavity air port (32) penetrating the end wall, and the front end cover (3) is provided with a rod cavity air port (31) penetrating the end wall; The outer circumferential wall of the air-floating piston (6) is provided with a plurality of internal channels three (15), and annular pressure relief grooves are provided at both ends; an axial internal channel two (13) connected to the internal channel three (15) is provided inside the piston front cover (14); an axial internal channel one (10) is provided inside the piston rod (1), one end of the internal channel one (10) is connected to the internal channel two (13) through the air pipe (12), and the other end is connected to the atmosphere; the gas in the air-floating piston (6) flows to the pressure relief grooves at both ends of the air-floating piston (6) through the throttle hole (7), and is discharged to the atmosphere through the internal channel three (15), the internal channel two (13), the air pipe (12) and the internal channel one (10) in sequence; The control system comprises a computer (20), a data acquisition card (21), a PWM signal generator (22) and a switch valve; the switch valve is used to control the on-off of the rodless cavity air port (32), the rod cavity air port (31) and the atmosphere, and the computer (20) controls the on-off of the switch valve via the data acquisition card (21) and the PWM signal generator (22); The laser displacement sensor (19) is mounted on a vertical mounting platform (18), and the laser emitted by the laser displacement sensor (19) can be irradiated onto the end surface of the piston rod (1); the position information on the laser displacement sensor (19) is transmitted to the computer (20) via the A / D port of the data acquisition card (21); The air supply system comprises an air source (23) and a pressure-stabilizing air tank (27). The pressure-stabilizing air tank (27) is connected to a first air inlet (33) and a second air inlet (34) via an air path. The compressed air generated by the air source (23) is transported to the inner cavities of the air bearing (2) and the air-floating piston (6) via the pressure-stabilizing air tank (27).

2. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The gas supply system further comprises a filter (24) and a proportional directional valve (26) which are arranged in sequence between the gas source (23) and the pressure-stabilizing gas tank (27) along the gas transmission direction, and a pressure sensor (28) responsible for collecting air pressure information in the pressure-stabilizing gas tank (27); the compressed air generated by the gas source (23) passes through the filter (24) and the proportional directional valve (26) and then enters the pressure-stabilizing gas tank (27); the pressure sensor (28) transmits the collected information to the computer (20) via the A / D port of the data acquisition card (21); the computer (20) adjusts the proportional directional valve (26) via the D / A port of the data acquisition card (21), thereby adjusting the air pressure value in the pressure-stabilizing gas tank (27).

3. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The gas supply system further comprises a filter (24) and a precision pressure reducing valve (25) which are arranged in sequence between the gas source (23) and the pressure-stabilizing gas tank (27) along the gas transmission direction. The precision pressure reducing valve (25) is responsible for directly adjusting the pressure of the filtered gas to a set value and then passing the gas into the pressure-stabilizing gas tank (27).

4. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The switch valve is divided into a normally closed high-speed switch valve one (29) and a normally closed high-speed switch valve two (30); the rodless cavity air port (32) of the independent air supply air floating frictionless cylinder (16) is connected to the normally closed high-speed switch valve one (29), and the rod cavity air port (31) is directly connected to the atmosphere; or the rod cavity air port (31) of the independent air supply air floating frictionless cylinder (16) is connected to the normally closed high-speed switch valve two (30), and the rodless cavity air port (32) is directly connected to the atmosphere; or the rod cavity air port (31) and the rodless cavity air port (32) of the independent air supply air floating frictionless cylinder (16) are respectively connected to the normally closed high-speed switch valve two (30) and the normally closed high-speed switch valve one (29).

5. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The permanent magnet module (5) is axially magnetized, radially magnetized, or has a Halbach array structure.

6. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The piston front cover (14) and the piston rod (1) are movably connected via a ball joint (11).

7. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The piston rod (1), the air-floating piston (6), the piston front cover (14) and the ball joint (11) are all made of non-magnetic metal materials.

8. The damping coefficient testing device of the independent air supply air floating frictionless cylinder capable of generating eddy current damping according to claim 1 is characterized in that: The two ends of the independent air supply air-floating frictionless cylinder (16) are respectively clamped by two fixing frames (17), and the fixing frames (17) are fixed on the vertical mounting platform (18) by bolts.

9. A test method for the damping coefficient test device of the air-floating frictionless cylinder with independent air supply capable of generating eddy current damping based on any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: An independent air supply air-floating frictionless cylinder (16) is mounted on a vertical mounting platform (18), and a laser displacement sensor (19) is mounted directly below the piston rod (1) so that the laser emitted by the laser head can irradiate the outer end surface of the piston rod (1). The pressure-stabilizing gas tank (27) begins to ventilate the inner cavity of the air bearing (2) and the air-floating piston (6), and the computer (20) controls the opening of the switch valve via the data acquisition card (21) and the PWM signal generator (22); Step 2: The piston rod (1), the air-floating piston (6), the piston front cover (14) and the ball joint (11) are referred to as the piston rod (1)-air-floating piston (6) assembly. The piston rod (1)-air-floating piston (6) assembly is manually pushed to the rear end cover (9) and then allowed to fall freely. The laser displacement sensor (19) detects and records the position information in real time. The position information is transmitted to the computer (20) via the A / D port of the data acquisition card (21); Step 3: a displacement warning distance is set, and when the laser displacement sensor (19) detects that the displacement of the piston rod (1)-air floating piston (6) assembly is greater than the displacement warning distance, the computer (20) issues a command to close the switch valve; Step 4: The position information of the piston rod (1)-air floating piston (6) assembly is obtained by a laser displacement sensor (19), and the speed at the uniform speed stage can be calculated using the time information monitored by a computer (20), and the eddy current damping coefficient can be deduced based on the gravity of the piston rod (1)-air floating piston (6) assembly.

10. A testing method for a damping coefficient testing device for an air-floating frictionless cylinder with independent air supply capable of generating eddy current damping according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: An independent air supply air-floating frictionless cylinder (16) is mounted on a vertical mounting platform (18), and a laser displacement sensor (19) is mounted directly above the piston rod (1) so that the laser emitted by the laser head can irradiate the outer end surface of the piston rod (1). The pressure-stabilizing gas tank (27) begins to ventilate the inner cavity of the air bearing (2) and the air-floating piston (6), and the computer (20) controls the opening of the switch valve via the data acquisition card (21) and the PWM signal generator (22); Step 2: The piston rod (1), the air-floating piston (6), the piston front cover (14) and the ball joint (11) are referred to as the piston rod (1)-air-floating piston (6) assembly. The piston rod (1)-air-floating piston (6) assembly is manually pushed to the rear end cover (9) and then allowed to fall freely. The laser displacement sensor (19) detects and records the position information in real time. The position information is transmitted to the computer (20) via the A / D port of the data acquisition card (21); Step 3: a displacement warning distance is set, and when the laser displacement sensor (19) detects that the displacement of the piston rod (1)-air floating piston (6) assembly is greater than the displacement warning distance, the computer (20) issues a command to close the switch valve; Step 4: The position information of the piston rod (1)-air floating piston (6) assembly is obtained by a laser displacement sensor (19), and the speed at the uniform speed stage can be calculated using the time information monitored by a computer (20), and the eddy current damping coefficient can be deduced based on the gravity of the piston rod (1)-air floating piston (6) assembly.

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