Lightweight high-integration hydraulic actuator

Abstract

The invention provides a light-weight high-integration hydraulic actuator. The light-weight high-integration hydraulic actuator comprises a first knuckle bearing, a second knuckle bearing, a displacement sensor, a servo valve sleeve, a servo valve element, a servo valve motor, a pressure sensor cover cap, a pressure sensor, a plug, an actuating cylinder, an electric connector, a piston rod, a loop, a key, a check nut, a bolt piece, an oil inlet connector and an oil return connector. The servo valve shell is integrated on the actuator cylinder, and the built-in displacement sensor and the embedded pressure sensor are adopted to achieve the high-integration design of the actuator; the actuating cylinder adopts a 3D printing technology to shorten an oil path and optimize the overall structural layout so as to realize miniaturization and light weight of the actuator; a rotary direct-drive servo valve is adopted, so that the oil liquid pollution resistance is high, and the stability of the actuator is facilitated; and the frequency characteristic is high, so that the high dynamic state of the actuator can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic quadruped robots, and in particular relates to a lightweight and highly integrated hydraulic actuator. Background Art

[0002] Robot leg drive actuators are divided into rotary and linear actuators. The load capacity, accuracy and dynamic effect of rotary actuators are inferior to those of linear actuators. Therefore, linear actuators are more widely used in legged robots due to their high power and high dynamic characteristics. With the continuous development of robots, the requirements for their size and weight are becoming more and more stringent. Therefore, integrated, miniaturized and lightweight linear actuators have a broader development prospect in the field of robots. Linear actuators drive the leg structure to rotate around the joints through linear displacement to achieve leg movement. By reasonably controlling the coordinated movement of the robot's legs, the robot can move forward, turn and other functions according to the preset speed, posture and gait.

[0003] At present, the research on linear actuators abroad has a solid foundation mainly in the BIG DOG series of quadruped robots of Boston Dynamics and the HyQ series of hydraulic quadruped robots of the Italian Institute of Technology (IIT), both of which use servo valve-controlled hydraulic cylinders. Among them, the actuator of HyQ uses a structure in which the force sensor and the piston are connected in series, and the speed sensor is installed at the joint, which has low accuracy and poor integration; the actuator of the bipedal robot Altlas derived from the BIG DOG series uses the technology of 3D printing cylinders to integrate the piston, pipeline, and servo valve in the cylinder, and its displacement sensor is external, resulting in a larger axial size, resulting in more space for the robot's leg structure, which will increase the size of the robot.

[0004] Domestic institutions that study quadruped robots are mainly distributed in universities and research institutes. Among them, Shandong University has in-depth experience in Scalf robot research. Its hydraulic actuator uses an external displacement sensor, and the servo valve and force sensor are directly installed on the cylinder, resulting in a low degree of integration and a large size of the actuator. Nanjing Chenguang Group Co., Ltd. invented a robot leg actuator. The actuator cylinder uses 3D printing to integrate the pressure sensor and displacement sensor inside the actuator cylinder, but the servo valve uses a traditional external installation and is fixed to the actuator cylinder by screws, resulting in a low degree of integration and a risk of leakage. In addition, the servo valves of these actuators all use traditional nozzle flapper valves, which have low frequency characteristics and are highly dependent on oil cleanliness. Summary of the invention

[0005] The purpose of the present invention is to provide a lightweight and highly integrated hydraulic actuator to meet the driving and control requirements of the leg joints of a quadruped robot. The actuator should be compact, lightweight, and have high-frequency response capabilities, respectively meeting the robot's narrow space installation requirements, lightweight requirements, and high dynamic requirements.

[0006] The technical solution to achieve the purpose of the present invention is: A lightweight and highly integrated hydraulic actuator, comprising a first joint bearing, a second joint bearing, a displacement sensor, a servo valve sleeve, a servo valve core, a servo valve motor, a pressure sensor cover, a pressure sensor, a plug, an actuator, an electrical connector, a piston rod, a slip ring, a key, a tightening nut, a bolt, an oil inlet joint and an oil return joint; The first joint bearing is mounted on one end of the actuator cylinder, and the second joint bearing 3 is mounted on the bolt member, located at the other end of the actuator cylinder, and is a mechanical interface for connecting the actuator and the robot joint; the bolt member is threadedly connected to the end of the piston rod away from the first joint bearing, and the position is fixed by a key and a tightening nut; The oil inlet joint and the oil return joint are installed on the actuator cylinder and are hydraulic interfaces connecting the actuator and the robot energy system; The electrical connector is fixedly installed in the hole at the bottom of the actuator cylinder, and the cables of the servo valve motor, displacement sensor, and pressure sensor are integrated and installed, and it is the electrical interface connecting the actuator and the robot control system; The actuator is integrated with the housing of the servo valve, the servo valve core and the servo valve sleeve are directly assembled on the actuator, the servo valve motor is connected to the servo valve core, and the movement of the servo valve core is controlled to realize the control of the direction and flow of the oil; The pressure sensor is pressed into the mounting hole on the actuator cylinder and fixed by the pressure sensor cover. The body of the displacement sensor is installed at the center hole of the actuator cylinder. The pull rod of the displacement sensor is fixed inside the piston rod by a locking nut 23. The plug is installed inside one end of the piston rod close to the second joint bearing. The piston rod is installed inside the actuating cylinder, and the sleeve is installed inside the actuating cylinder and outside the piston rod.

[0007] Furthermore, it also includes a pressure plate, which is fixed on the actuator cylinder through a first screw to limit the servo valve sleeve, and the end surface sealing on both sides is achieved through a fifth O-ring.

[0008] Furthermore, the pressure sensor is sealed with the actuator cylinder by a second O-ring.

[0009] Furthermore, the displacement sensor is sealed by a retaining ring and a first O-ring, and is axially limited by a fastening screw.

[0010] Furthermore, the plug is provided with two sealing grooves, and a third O-ring is installed in the sealing groove.

[0011] Furthermore, the piston rod and the actuator are sealed by a Gly ring.

[0012] Furthermore, a wear-resistant ring is installed between the piston rod and the actuator cylinder.

[0013] Furthermore, the servo valve sleeve and the actuator cylinder are radially sealed by a seventh O-ring.

[0014] Furthermore, the oil inlet joint and the oil return joint are mounted on the actuator cylinder via a second screw, and are sealed via a sixth O-ring.

[0015] Furthermore, the sleeve is axially limited by a clamping nut, and the sleeve is statically sealed with the actuator cylinder by a double-pass fourth O-ring, and is dynamically sealed with the piston rod by a step seal and a rem seal.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a rotary direct-drive servo valve and a servo valve motor direct-drive control method, which is suitable for high pressure and large flow requirements, improves the system's anti-pollution ability, and maintains high precision under harsh working conditions; (2) The present invention optimizes the structure of the rotary direct-drive servo valve housing, removes the redundant parts, and only retains the installation space of the servo valve sleeve. The servo valve housing is optimized to a very simple cylinder, and the servo valve housing and the actuator are integrated using 3D printing technology, which greatly improves the integration of the actuator and reduces the weight and sealing parts, which is conducive to reducing the risk of hydraulic oil leakage; the internal oil circuit of the servo valve is optimized, which is conducive to the high dynamic response of the servo valve; (3) The present invention adopts a built-in LVDT displacement sensor and an embedded miniaturized pressure sensor, which are integrated inside the actuator, which is conducive to improving overall integration and high-frequency data acquisition, and realizing real-time feedback of displacement and system oil pressure; (4) The actuator cylinder of the present invention adopts 3D printing technology to optimize the structural layout, reduce redundant volume, improve the lightweight of the actuator, reduce the flow channel length, adopt smooth transition, reduce oil energy loss, optimize flow characteristics, and promote high-frequency response capability; (5) The present invention uses step seals and rem seals as the dynamic sealing structure between the sleeve and the piston rod, which effectively improves the linear dynamic sealing performance, reduces the friction between the piston rod and the seal, and prolongs the service life; (6) The present invention uses a Gly ring as a dynamic sealing structure between the piston and the actuator, and adds a wear-resistant ring as a guide to avoid direct friction between metal parts, increase force uniformity, and improve service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the main cross-sectional view of this patented lightweight, highly integrated actuator.

[0018] Figure 2 This is a side profile of the patented lightweight, highly integrated actuator.

[0019] In the figure, 1-first joint bearing, 2-displacement sensor, 3-retaining ring, 4-first O-ring, 5-servo valve sleeve, 6-servo valve core, 7-servo valve motor, 8-step seal, 9-pressure sensor cover, 10-pressure sensor, 11-second O-ring, 12-rem seal, 13-dust ring, 14-third O-ring, 15-plug, 16-actuator, 17-fastening screw, 18-wear-resistant ring, 19-Glay ring, 2 0-electrical connector, 21-displacement sensor pull rod, 22-piston rod, 23-locking nut, 24-fourth O-ring, 25-slip sleeve, 26-pressure nut, 27-key, 28-tightening nut, 29-bolt, 30-second joint bearing, 31-oil inlet joint, 32-first screw, 33-fifth O-ring, 34-pressure plate, 35-sixth O-ring, 36-seventh O-ring, 37-second screw, 38-oil return joint. DETAILED DESCRIPTION

[0020] The technical solution of the present invention adopts a single-rod valve-controlled hydraulic actuator. The oil provided by the onboard power source flows to the oil inlet of the servo valve. After the servo controller receives the position or force command of the motion controller, it closes the loop of the position feedback signal / force feedback signal in the actuator, and controls the movement direction of the valve core and the opening size of the valve by controlling the polarity and size of the servo valve current, thereby controlling the oil flow and direction of the servo valve. The actuator outputs the corresponding position to realize the electro-hydraulic position / force servo control of the actuator.

[0021] The lightweight and highly integrated hydraulic actuator of the present invention is mainly composed of an actuator cylinder, a piston rod, a servo valve (valve core, sleeve, servo valve motor), a linear displacement sensor, a pressure sensor, an electrical connector, a spherical bearing, a seal, etc. Figure 1 , Figure 2 shown.

[0022] In order to achieve the highly integrated design of the actuator, the original housing structure of the servo valve is simplified, the redundant parts are removed, and only the installation space of the servo valve sleeve is retained. The wall thickness is reduced while ensuring the strength. The servo valve housing is designed as a cylinder, and 3D printing technology is used to merge the servo valve housing and the actuator cylinder. The oil circuit is simplified, and the servo valve sleeve and valve core are directly embedded in the actuator cylinder to improve the integration of the servo valve; the non-contact displacement sensor is installed inside the piston rod; the pressure sensor is installed in an embedded manner to achieve the integrated installation of important components. An electrical connector mounting seat is designed on the actuator cylinder, and the displacement sensor, pressure sensor, and servo valve cable interface are integrated into the same connector to improve the integration of the electrical interface.

[0023] In order to achieve the lightweight design goal of the actuator, the actuator cylinder is made of titanium alloy and a suitable safety factor is selected to reduce the overall thickness while ensuring the design strength margin. The rotary direct-drive servo valve housing and the actuator cylinder are combined to effectively improve the weight reduction effect of the servo valve. 3D printing technology is used to optimize the flow channel layout and reduce the flow channel length. The actuator cylinder is designed with an integrated molding design to effectively reduce redundant structures.

[0024] In order to realize the miniaturization design of the actuator, smaller electrical connectors, displacement sensors and pressure sensors are selected, and embedded installation is adopted to avoid external installation. The servo valve housing is integrated on the actuator cylinder, and the structure is optimized based on the idea of ​​3D printing to achieve the goals of miniaturization, lightweight and integration.

[0025] In order to achieve the high dynamic requirements of the actuator, a rotary direct-drive servo valve is selected, whose valve body shell is integrated on the actuator cylinder. The rotary direct-drive servo valve has the characteristics of fast dynamic response and strong resistance to oil contamination, which is conducive to achieving the high dynamic requirements of the actuator.

[0026] The specific details and working conditions of a highly integrated, lightweight, miniaturized, and highly dynamic hydraulically driven linear displacement actuator proposed in this patent are as follows: The lightweight and highly integrated hydraulic actuator of the present invention mainly comprises a first joint bearing 1, a second joint bearing 30, a displacement sensor 2, a retaining ring 3, a servo valve sleeve 5, a servo valve core 6, a servo valve motor 7, a step seal 8, a pressure sensor cover 9, a pressure sensor 10, a rem seal 12, a dust ring 13, a plug 15, an actuator 16, a fastening screw 17, a wear-resistant ring 18, a Gley ring 19, an electrical connector 20, a displacement sensor pull rod 21, a piston rod 22, a locking nut 23, a slip ring 25, a clamping nut 26, a key 27, a tightening nut 28, a bolt 29, a first O-ring 4, a second O-ring 11, a third O-ring 14, a fourth O-ring 24, a fifth O-ring 33, a sixth O-ring 35, a seventh O-ring 36, an oil inlet joint 31, a first screw 32, a second screw 37, a pressure plate 34, and an oil return joint 38.

[0027] The first joint bearing 1 and the second joint bearing 30 are respectively mounted on the actuator 16 and the bolt member 29, which are the mechanical interfaces between the actuator and the robot joint; the bolt member 29 is threadedly connected to the piston rod 22, has a certain length adjustment function, and is fixed in position by the key 27 and the tightening nut 28.

[0028] The oil inlet connector 31 and the oil return connector 38 are mounted on the actuator cylinder 16 via the second screw 37 and sealed via the sixth O-ring 35 . They are hydraulic interfaces for connecting the actuator to the robot energy system.

[0029] The electrical connector 20 is installed in the hole at the bottom of the actuator cylinder 16 and fixed by screws. The cables of the servo valve motor 7, the displacement sensor 2, and the pressure sensor 10 can be integrated and installed. It is the electrical interface connecting the actuator and the robot control system.

[0030] The actuator 16 integrates the housing of the servo valve, the servo valve core 6 and the servo valve sleeve 5 are directly assembled on the actuator 16, and the servo valve motor 7 controls the movement of the servo valve core 6 to control the direction and flow of the oil. The servo valve sleeve 5 and the actuator 16 are radially sealed by the seventh O-ring 36, and the pressure plate 34 is fixed on the actuator 16 by the first screw 32 to limit the servo valve sleeve 5, and the end face sealing on both sides is realized by the fifth O-ring 33.

[0031] Two pressure sensors 10 are pressed into the mounting holes on the actuator 16, and the pressure sensor 10 and the actuator 16 are sealed by the second O-ring 11, and fixed by the pressure sensor cover 9 to realize the collection of the oil pressure of the two chambers. The main body of the displacement sensor 2 is installed at the center hole of the actuator 16, sealed by the retaining ring 3 and the first O-ring 4, and axially limited by the fastening screw 17. The pull rod of the displacement sensor 2 is fixed inside the piston rod 22 by the locking nut 23 to realize the real-time collection of the displacement of the piston rod 22. The plug 15 is installed inside the piston rod 22, and the two sealing grooves on the plug 15 are installed with two third O-rings 14 to realize the sealing between the inside and outside of the piston rod 22.

[0032] The piston rod 22 is installed inside the actuator 16. The piston rod 22 and the actuator 16 are sealed by the Gly ring 19, and the wear ring 18 is used to guide and reduce wear. The wear ring 18 can provide radial support protection to avoid direct contact between the piston rod 22 and the actuator 16, thereby improving the sealing reliability and service life of the piston rod.

[0033] The looper 25 is installed inside the actuator 16 and is axially limited by the compression nut 26. The static seal between the looper 25 and the actuator 16 is achieved by the sealing form of the double-pass fourth O-ring 24. The dynamic seal between the looper 25 and the piston rod 22 is achieved by the sealing form of the step seal 8 and the rem seal 12. In addition to the sealing function, the step seal 8 and the rem seal 12 can also provide radial support for the piston rod 22. A dust ring 13 is installed on the outermost side of the looper 25 to prevent the inside of the actuator from being contaminated by dust and other debris.

[0034] When the lightweight and highly integrated actuator of this patent is working, the high-pressure oil of the robot energy system enters the actuator from the oil inlet connector 31, and the command current issued by the robot control system controls the rotation of the servo valve motor 7, driving the servo valve core 6 to produce relative displacement in the servo valve sleeve 5, and controlling the high-pressure oil to flow to the left / right cavity of the actuator cylinder 16. The oil pushes the piston rod 22 to extend or retract in the cavity of the actuator cylinder 16, and the piston rod 22 drives the displacement sensor rod 21 to move synchronously. The oil flows out from the other cavity of the actuator cylinder 16 and flows to the energy system through the return oil connector 38. In the process of the oil pushing the piston rod 22 to move, the displacement sensor rod 21 and the displacement sensor 2 fixed on the actuator cylinder 16 produce relative displacement, that is, a voltage signal will be output. The voltage signal is amplified and converted to the displacement value of the piston rod 22, which is used to control the position closed loop of the system. The two pressure sensors 10 respectively collect the pressure values ​​of the oil in the two cavities of the actuator cylinder 16, which are used to control the pressure closed loop of the system.

[0035] The highly integrated actuator of the present invention integrates the servo valve housing on the actuator cylinder, and adopts a built-in displacement sensor and an embedded pressure sensor to realize a highly integrated design of the actuator; the actuator cylinder adopts 3D printing technology to shorten the oil circuit and optimize the overall structural layout to realize the miniaturization and lightweight of the actuator; a rotary direct-drive servo valve is adopted, which has high resistance to oil and liquid contamination, which is beneficial to the stability of the actuator; and the high frequency characteristic is conducive to realizing the high dynamics of the actuator.

[0036] The above-mentioned specific examples are only preferred examples of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lightweight and highly integrated hydraulic actuator, characterized in that: The invention comprises a first joint bearing (1), a second joint bearing (30), a displacement sensor (2), a servo valve sleeve (5), a servo valve core (6), a servo valve motor (7), a pressure sensor cover (9), a pressure sensor (10), a plug (15), an actuator (16), an electrical connector (20), a piston rod (22), a sleeve (25), a key (27), a tightening nut (28), a bolt (29), an oil inlet joint (31) and an oil return joint (38); The first joint bearing (1) is mounted on one end of the actuator cylinder (16), and the second joint bearing 3 is mounted on a bolt member (29) located at the other end of the actuator cylinder (16), which is a mechanical interface for connecting the actuator and the robot joint; the bolt member (29) is threadedly connected to the end of the piston rod (22) away from the first joint bearing (1), and the position is fixed by a key (27) and a tightening nut (28); The oil inlet joint (31) and the oil return joint (38) are mounted on the actuator cylinder (16) and are hydraulic interfaces for connecting the actuator to the robot energy system; The electrical connector (20) is fixedly mounted in a hole at the bottom of the actuator cylinder (16), and is used to integrate the cables of the servo valve motor (7), the displacement sensor (2), and the pressure sensor (10), and is an electrical interface for connecting the actuator to the robot control system; The actuator (16) is integrated with the housing of the servo valve, the servo valve core (6) and the servo valve sleeve (5) are directly assembled on the actuator (16), and the servo valve motor (7) is connected to the servo valve core (6) to control the movement of the servo valve core (6) to achieve control of the direction and flow of the oil; The pressure sensor (10) is press-fitted into a mounting hole on the actuator cylinder (16) and fixed by a pressure sensor cover (9); the main body of the displacement sensor (2) is mounted at the center hole of the actuator cylinder (16); the pull rod of the displacement sensor (2) is fixed inside the piston rod (22) by a locking nut (23); and the plug (15) is mounted inside one end of the piston rod (22) close to the second joint bearing (30); The piston rod (22) is installed inside the actuator cylinder (16), and the sleeve (25) is installed inside the actuator cylinder (16) and outside the piston rod (22).

2. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: It also includes a pressure plate (34) which is fixed to the actuator cylinder (16) by a first screw (32) to limit the position of the servo valve sleeve (5), and achieves end face sealing on both sides by a fifth O-ring (33).

3. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: The pressure sensor (10) is sealed with the actuator (16) via a second O-ring (11).

4. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: The displacement sensor (2) is sealed by a retaining ring (3) and a first O-ring (4), and is axially limited by a fastening screw (17).

5. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: The plug (15) is provided with two sealing grooves, and a third O-ring (14) is installed in the sealing grooves.

6. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: The piston rod (22) and the actuator cylinder (16) are sealed via a Gly ring (19).

7. A lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: A wear-resistant ring (18) is installed between the piston rod (22) and the actuator cylinder (16).

8. A lightweight and highly integrated hydraulic actuator according to claim 7, characterized in that: The servo valve sleeve (5) and the actuator cylinder (16) are radially sealed via a seventh O-ring (36).

9. The lightweight and highly integrated hydraulic actuator according to claim 1, characterized in that: The oil inlet joint (31) and the oil return joint (38) are mounted on the actuator (16) via a second screw (37) and are sealed via a sixth O-ring (35).

10. A lightweight and highly integrated hydraulic actuator according to any one of claims 1 to 9, characterized in that: The sleeve (25) is axially limited by a clamping nut (26); the sleeve (25) is statically sealed with the actuator (16) by a double-pass fourth O-ring (24), and is dynamically sealed with the piston rod (22) by a step seal (8) and a rem seal (12).

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