Pneumatic multi-degree-of-freedom robot arm and torque control method

Abstract

The application provides a pneumatic multi-degree-of-freedom mechanical arm and a torque control method. The pneumatic multi-degree-of-freedom mechanical arm comprises a first base, a first joint, a second joint, a third joint, a fourth joint, a fifth joint and a sixth joint, the first joint and the second joint are connected through a first joint cylinder drive, the second joint and the third joint are connected through a second joint cylinder drive, the third joint and the fourth joint are connected through a third joint cylinder drive, the fourth joint and the fifth joint are connected through a fourth joint cylinder drive, and the fifth joint and the sixth joint are connected through a fifth joint cylinder drive; each cylinder is a double-chamber cylinder, and a double-chamber air inlet pipeline, an angle sensor signal line and a pressure sensor signal line are connected to each cylinder, and the pipeline and the signal line are arranged in a hollow structure of each joint; each cylinder is connected with a proportional electromagnetic valve. The application reduces the sealing requirement and the cost.

Description

Technical Field

[0001] This invention relates to the field of robotic arm technology, and in particular to a pneumatic multi-degree-of-freedom robotic arm and a torque control method. Background Technology

[0002] With the rapid development of fields such as electronics manufacturing, precision assembly, laboratory automation, small warehousing, and medical massage, the market demand for lightweight, compact six-degree-of-freedom robotic arms is becoming increasingly urgent. These scenarios do not require heavy loads, but impose stringent requirements on the robotic arm's compactness, lightweight design, environmental friendliness, and low cost. It must be adaptable to confined spaces, easy to move, and also avoid oil contamination and high-pressure hazards.

[0003] Existing robotic arms, such as the fully hydraulically driven six-degree-of-freedom robotic arm disclosed in patent publication number CN112589789A, are designed with six degrees of freedom. This robotic arm is directly driven by a hydraulic motor, eliminating the need for high-precision reducers, servo motors, and drivers, and can meet the requirements of high-power, heavy-load, and complex electromagnetic environments. However, its hydraulic control method has the following problems: (a) Hydraulic components have extremely high requirements for sealing performance, which leads to high costs; (ii) Hydraulic oil is incompressible and poses a risk of leakage and contamination, making it unsuitable for clean / explosion-proof environments; (iii) The hydraulic motor can rotate continuously 360° with no limit on the range of motion. Summary of the Invention

[0004] The purpose of this invention is to provide a pneumatic multi-degree-of-freedom robotic arm and a torque control method that reduces sealing requirements and lowers costs.

[0005] The technical solution of the present invention is: a pneumatic multi-degree-of-freedom robotic arm, comprising a first base and a first joint, a second joint, a third joint, a fourth joint, a fifth joint, and a sixth joint, which are connected sequentially from the first base and are hollow inside, characterized in that the first joint and the second joint are driven by a first joint cylinder, the second joint and the third joint are driven by a second joint cylinder, the third joint and the fourth joint are driven by a third joint cylinder, the fourth joint and the fifth joint are driven by a fourth joint cylinder, and the fifth joint and the sixth joint are driven by a fifth joint cylinder; The first joint cylinder, the second joint cylinder, the third joint cylinder, the fourth joint cylinder, and the fifth joint cylinder are all dual-chamber cylinders, each connected to a dual-chamber air intake pipe, an angle sensor signal line, and a pressure sensor signal line. The pipes and signal lines are located within the hollow structure of each joint. The first joint cylinder, the second joint cylinder, the third joint cylinder, the fourth joint cylinder, and the fifth joint cylinder are connected to a proportional solenoid valve.

[0006] Preferably, the first joint cylinder, the second joint cylinder, and the third joint cylinder are large-sized vane-type swing cylinders, and the fourth joint cylinder and the fifth joint cylinder are small-sized vane-type swing cylinders. The size constant ratio of the large-sized vane-type swing cylinder to the small-sized vane-type swing cylinder is 2:1 to 3:1.

[0007] Preferably, the first joint cylinder, the second joint cylinder, the third joint cylinder, the fourth joint cylinder, and the fifth joint cylinder all include a rotor and a cylinder body. One end of the rotor is rotatably disposed in the cylinder body. The cylinder body is installed in one joint, and the other end of the rotor is installed in another joint. A buffer block is provided at the lower end of the cylinder body. An angle sensor is coaxially connected to the inner sidewall of each joint via a bracket. An air source port is provided on the cylinder body, and a pressure sensor is connected to the air source port.

[0008] The present invention also provides a torque control method for the above-mentioned pneumatic multi-degree-of-freedom robotic arm, comprising: Step 1: Based on the desired motion trajectory of the robotic arm and the six-degree-of-freedom dynamic model, calculate the reference torque required for each joint in the current control cycle. ; Step 2: Obtain the joint rotation angle in real time using angle sensors at each joint. According to the angle Calculate the joint angular velocity; Step 3: Collect the pressure of the dual air chambers using pressure sensors at each joint. , Then calculate the actual pneumatic output torque of each joint cylinder. in, K This refers to the dimensional constant of the corresponding cylinder; Step four, then calculate the torque error. ; Step 5, based on torque error The control voltage for adjusting the opening of the proportional solenoid valve is output. This enables dynamic tracking of torque under graded loads.

[0009] Preferably, the opening degree of the proportional solenoid valve is controlled by solving the differential equations of air pressure in the two chambers of the cylinder, and by combining this with the Saint-Venant adiabatic mass flow rate formula for gas flowing through the solenoid valve orifice, to establish the effective throttling area. The mapping relationship with the rate of change of air chamber pressure.

[0010] Preferably, the effective throttling area With control voltage Offline data fitting and calibration were performed using a fifth-order polynomial model, satisfying the formula. ,in to These are the model constants obtained through calibration experiments.

[0011] Compared with related technologies, the beneficial effects of the present invention are as follows: I. This invention employs a cylinder drive system, utilizing compressed air to achieve zero oil contamination. It features explosion-proof and overload self-protection characteristics, making it safe for use in cleanrooms, laboratories, and other environments with high environmental and safety requirements. It eliminates the need for expensive reducers, and the core component (vane-type swing cylinder) is low-cost and experiences minimal wear. Combined with a modular design, this reduces overall manufacturing costs. Subsequent maintenance only requires disassembling and reassembling the cylinder, simplifying operation and significantly reducing maintenance costs.

[0012] Second, this invention uses a vane-type swing cylinder for direct drive, realizing a zero-gear transmission mechanism, which is simpler in structure. Moreover, the vane-type swing cylinder directly limits the angle (generally <270°) through a buffer block, which is safer.

[0013] Third, each joint of the present invention adopts a hollow structure, and the air pipes and wiring are placed inside the hollow structure to achieve hidden wiring, avoid messy external wiring, further optimize the structural compactness, and adapt to the layout requirements of narrow working spaces.

[0014] Fourth, the torque adjustment formula of this invention, based on the principle of pneumatic transmission, can adjust the air source pressure to specifically match the load difference between the bottom base joint (heavy load requirement) and the wrist joint (light load requirement), thus avoiding instability caused by insufficient torque of the bottom joint and reducing energy waste caused by power redundancy of the wrist joint; the angle sensor is coaxially connected to the cylinder rotor to provide real-time feedback of the rotation angle signal, forming a closed-loop control to meet the requirements of high-precision operations such as precision assembly.

[0015] 5. The vane-type swing cylinder and the joint housing are detachably connected by bolts, making disassembly and assembly simple and efficient, facilitating component replacement and maintenance. The maximum rotation angle of the joint is adjusted via a buffer stop, allowing for flexible changes in the motion space without modifying the core structure. This adapts to the stroke requirements of different work scenarios, significantly improving the versatility and flexibility of the robotic arm. The built-in air circuit and signal cable layout avoids malfunctions caused by cable tangling and wear, enhancing the stability of the robotic arm's operation.

[0016] VI. This invention uses a vane-type swing cylinder to directly drive the joint, completely eliminating intermediate transmission mechanisms such as reducers and gear sets, greatly reducing the number of parts and significantly reducing the overall weight and volume of the robotic arm. Attached Figure Description

[0017] Figure 1 A schematic diagram of the structure of the pneumatic multi-degree-of-freedom robotic arm provided by the present invention; Figure 2 An exploded view of the installation of the vane-type oscillating cylinder and the angle sensor; Figure 3 This is a schematic diagram of the exploded structure of the first and second joints; Figure 4 This is a schematic diagram of the exploded structure of the long connecting rod and the third joint; Figure 5 This is a schematic diagram of the exploded structure of the third joint and the short connecting rod; Figure 6 This is an exploded structural diagram of the short connecting rod and the fourth joint housing; Figure 7 This is a structural diagram of the fourth, fifth, and sixth joints; Figure 8 This is a schematic diagram of the exploded structure of the fourth, fifth, and sixth joints; Figure 9 This is a flowchart of the torque control process for a pneumatic multi-degree-of-freedom robotic arm.

[0018] In the attached diagram: 10, First joint; 20, Second joint; 30, Third joint; 40, Fourth joint; 50, Fifth joint; 60, Sixth joint; 70, First base; 1, Rotor; 11, Flange; 2, Cylinder body; 3, Air source port; 4, Buffer block; 5, Bracket; 6, Angle sensor; 101, Second base; 102, First joint housing; 103, First joint cylinder; 201, Second joint housing; 202, Second joint cylinder; 301, Long connecting rod; 302, Third joint housing; 303, Third joint cylinder; 401, Short connecting rod; 402, Fourth joint housing; 403, Fourth joint cylinder; 501, Fifth joint housing; 502, Fifth joint cylinder; 601, Sixth joint housing; 602, Sixth joint cylinder. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" used below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0020] like Figure 1As shown, the pneumatic multi-degree-of-freedom robotic arm provided in this embodiment includes a first base 70 and a first joint 10, a second joint 20, a third joint 30, a fourth joint 40, a fifth joint 50, and a sixth joint 60, which are connected sequentially from the first base 70 and are hollow inside. The first joint 10 and the second joint 20 are driven to be connected by a first joint cylinder 103, the second joint 20 and the third joint 30 are driven to be connected by a second joint cylinder 202, the third joint 30 and the fourth joint 40 are driven to be connected by a third joint cylinder 303, the fourth joint 40 and the fifth joint 50 are driven to be connected by a fourth joint cylinder 403, and the fifth joint 50 and the sixth joint 60 are driven to be connected by a fifth joint cylinder 502.

[0021] The first joint cylinder 103, the second joint cylinder 202, the third joint cylinder 303, the fourth joint cylinder 403, and the fifth joint cylinder 502 are all dual-chamber cylinders, each connected to a dual-chamber air intake pipe, an angle sensor signal line, and a pressure sensor signal line. The pipes and signal lines are housed within the hollow structure of each joint. The first joint cylinder 103, the second joint cylinder 202, the third joint cylinder 303, the fourth joint cylinder 403, and the fifth joint cylinder 502 are connected to proportional solenoid valves.

[0022] like Figure 2 As shown, the first joint cylinder 103, the second joint cylinder 202, the third joint cylinder 303, the fourth joint cylinder 403, and the fifth joint cylinder 502 all include a rotor 1 and a cylinder body 2. One end of the rotor 1 is rotatably mounted inside the cylinder body 2. The cylinder body 2 is installed in one joint, and the other end of the rotor 1 is installed in another joint. A buffer block 4 is provided at the lower end of the cylinder body 2. An angle sensor 6 is coaxially connected to the inner wall of each joint via a bracket 5. An air source port 3 is provided on the cylinder body 2, and a pressure sensor is connected to the air source port 3. A flange 11 is provided at the end of the rotor 1, which serves as the cylinder output end and connects to the outer shell of the next-stage joint. There are no intermediate transmission mechanisms such as reducers or gear sets between each joint and the cylinder, realizing direct torque transmission. The detection shaft of the angle sensor 6 is coaxially connected to the rotor 1 to collect the joint rotation angle signal in real time.

[0023] The first joint cylinder 103, the second joint cylinder 202 and the third joint cylinder 303 are large-sized vane-type swing cylinders, while the fourth joint cylinder 403 and the fifth joint cylinder 502 are small-sized vane-type swing cylinders. The size constant ratio of the large-sized vane-type swing cylinder to the small-sized vane-type swing cylinder is 2:1 to 3:1.

[0024] like Figure 1 , Figure 3 , Figure 4As shown, the first joint 10 includes a second base 101, a first joint housing 102, and a first joint cylinder 103. The second joint 20 includes a second joint housing 201 and a second joint cylinder 202. The third joint 30 includes a long connecting rod 301 and a third joint housing 302 connected to the upper end of the long connecting rod 301. The second base 101 is bolted to the first base 70. The bottom of the first joint housing 102 is bolted to the second base 101. The first joint cylinder 103 and the angle sensor 6 are disposed in the first joint housing 102, and the flange 11 on the rotor 1 of the first joint cylinder 103 is connected to the second joint housing 201.

[0025] The second joint cylinder 202 and the angle sensor 6 are housed in the second joint housing 201. The flange 11 on the rotor 1 of the second joint cylinder 202 is connected to the lower end of the long connecting rod 301. The air supply line and sensor line of the first joint 10 are connected through the bottom opening on the side of the second base 101. The air supply line and sensor line of the second joint 20 are connected through the bottom opening of the second joint housing 201. The air supply line and sensor line of the third joint 30 are connected through the side opening of the third joint housing 302 and the hollow long connecting rod 301.

[0026] like Figure 5 , Figure 6 As shown, the fourth joint 40 includes a short connecting rod 401, a fourth joint housing 402 connected to the upper end of the short connecting rod 401, and a fourth joint cylinder 403 disposed within the fourth joint housing 402. The third joint cylinder 303 and the angle sensor 6 are disposed in the third joint housing 302, and the flange 11 of the rotor 1 of the third joint cylinder 303 is connected to the lower end of the short connecting rod 401. The air supply line and sensor line of the fourth joint 40 are connected through the side opening of the fourth joint housing 402 and the hollow short connecting rod 401.

[0027] like Figure 7 , Figure 8As shown, the fifth joint 50 includes a fifth joint housing 501 and a fifth joint cylinder 502. The sixth joint 60 includes a sixth joint housing 601 and a sixth joint cylinder 602. The flange 11 on the rotor 1 of the fourth joint cylinder 403 is connected to the fifth joint housing 501. The fifth joint cylinder 502 is disposed within the fifth joint housing 501, and the flange 11 on the rotor 1 of the fifth joint cylinder 502 is connected to the sixth joint housing 601. The sixth joint cylinder 602 is disposed within the sixth joint housing 601, and the flange on the sixth joint cylinder 602 extends outside the sixth joint housing 601 for mounting end grippers. The air supply line and sensor line of the fifth joint 50 are connected through the bottom opening of the fifth joint housing 501. The air supply line and sensor line of the sixth joint 60 are connected through the bottom opening of the sixth joint housing 601.

[0028] like Figure 2 , Figure 9 As shown, the movement limit of the joint can be adjusted by adjusting the buffer stop 4. After adjusting the limit, the initial volume of the two air chambers can be calculated based on the angle. The joint angle is obtained in real time by the angle sensor 6. The joint angular velocity is obtained by differentiating the joint angle. The air pressure in the two chambers is obtained through two air pressure sensors via air source port 3. , The gas flow rate through the two chambers in the previous control cycle was obtained through calculation. , .

[0029] The present invention also provides a torque control method for the above-mentioned pneumatic multi-degree-of-freedom robotic arm, comprising: Step 1: Based on the desired motion trajectory of the robotic arm and the six-degree-of-freedom dynamic model, calculate the reference torque required for each joint in the current control cycle. .

[0030] Step two: The joint rotation angle is acquired in real time using incremental angle sensors configured in each joint. The joint angular velocity ω is calculated using formula (1): ω=Δθ / Δt(1) In the formula, t represents time.

[0031] Step 3: Collect the pressure of the dual air chambers using pressure sensors at each joint. , Then calculate the actual pneumatic output torque of each joint cylinder. in, K This represents the dimensional constant of the corresponding cylinder.

[0032] Step four, then calculate the torque error. .

[0033] Step 5: For the large-size vane-type swing cylinders used in the first joint cylinder 103, the second joint cylinder 202, and the third joint cylinder 303, and for the small-size vane-type swing cylinders used in the fourth joint cylinder 403 and the fifth joint cylinder 502, two independent control parameter matrices are invoked respectively to calculate the torque error. Input to the closed-loop controller, output control voltage to adjust the opening degree of the proportional solenoid valve This enables dynamic tracking of torque under graded loads.

[0034] Effective throttling area With control voltage Offline data fitting and calibration were performed using a fifth-order polynomial model, satisfying the formula. ,in to These are model constants obtained through calibration experiments; the solenoid valves of large-size cylinders and small-size cylinders correspond to different sets of polynomial calibration constants.

[0035] In specific implementations of this invention, the contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0036] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A pneumatic multi-degree-of-freedom robotic arm, comprising a first base (70) and a first joint (10), a second joint (20), a third joint (30), a fourth joint (40), a fifth joint (50), and a sixth joint (60) connected sequentially from the first base (70) and having a hollow interior, characterized in that, The first joint (10) and the second joint (20) are driven to be connected by the first joint cylinder (103), the second joint (20) and the third joint (30) are driven to be connected by the second joint cylinder (202), the third joint (30) and the fourth joint (40) are driven to be connected by the third joint cylinder (303), the fourth joint (40) and the fifth joint (50) are driven to be connected by the fourth joint cylinder (403), and the fifth joint (50) and the sixth joint (60) are driven to be connected by the fifth joint cylinder (502). The first joint cylinder (103), the second joint cylinder (202), the third joint cylinder (303), the fourth joint cylinder (403), and the fifth joint cylinder (502) are all dual-chamber cylinders, each connected to a dual-chamber air intake pipe, an angle sensor signal line, and a pressure sensor signal line. The pipes and signal lines are located within the hollow structure of each joint. The first joint cylinder (103), the second joint cylinder (202), the third joint cylinder (303), the fourth joint cylinder (403), and the fifth joint cylinder (502) are connected to a proportional solenoid valve.

2. The pneumatic multi-degree-of-freedom robotic arm according to claim 1, characterized in that, The first joint cylinder (103), the second joint cylinder (202) and the third joint cylinder (303) are large-sized vane-type swing cylinders, and the fourth joint cylinder (403) and the fifth joint cylinder (502) are small-sized vane-type swing cylinders. The size constant ratio of the large-sized vane-type swing cylinder to the small-sized vane-type swing cylinder is 2:1 to 3:

1.

3. The pneumatic multi-degree-of-freedom robotic arm according to claim 1, characterized in that, The first joint cylinder (103), the second joint cylinder (202), the third joint cylinder (303), the fourth joint cylinder (403) and the fifth joint cylinder (502) all include a rotor (1) and a cylinder body (2). One end of the rotor (1) is rotatably disposed in the cylinder body (2). The cylinder body (2) is installed in one joint, and the other end of the rotor (1) is installed in another joint. A buffer block (4) is provided at the lower end of the cylinder body (2). An angle sensor (6) is coaxially connected to the inner side wall of each joint through a bracket (5). An air source port (3) is provided on the cylinder body (2), and a pressure sensor is connected to the air source port (3).

4. A torque control method for a pneumatic multi-degree-of-freedom robotic arm as described in any one of claims 1-3, characterized in that, include: Step 1: Based on the desired motion trajectory of the robotic arm and the six-degree-of-freedom dynamic model, calculate the reference torque required for each joint in the current control cycle. ; Step 2: The joint rotation angle is acquired in real time using the angle sensors (6) of each joint. According to the angle Calculate the joint angular velocity; Step 3: Collect the pressure of the dual air chambers using pressure sensors at each joint. , Then calculate the actual pneumatic output torque of each joint cylinder. in, K This refers to the dimensional constant of the corresponding cylinder; Step four, then calculate the torque error. ; Step 5, based on torque error The control voltage for adjusting the opening of the proportional solenoid valve is output. This enables dynamic tracking of torque under graded loads.

5. The torque control method according to claim 4, characterized in that, The opening degree of the proportional solenoid valve is controlled by solving the differential equations of air pressure in the two chambers of the cylinder, and by combining this with the Saint-Venant adiabatic mass flow rate formula for gas flowing through the solenoid valve orifice, thus establishing the effective throttling area. The mapping relationship with the rate of change of air chamber pressure.

6. The torque control method according to claim 5, characterized in that, Effective throttling area With control voltage Offline data fitting and calibration were performed using a fifth-order polynomial model, satisfying the formula. ,in to These are the model constants obtained through calibration experiments.

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