Parallel arrangement type series elastic driver

Abstract

The utility model belongs to the technical field of robots, and discloses a parallel arrangement type series elastic driver which comprises Bowden cables, special springs, a rotating disc and joint input and output flanges. Bearings are arranged among the output flange, the output shaft and the rotor and aim at bearing non-torque loads and achieving relative rotation between the input part and the output part. The output shaft, the rotor, the special spring and the bearing are all fixed to the output flange, the servo motor is installed on the input flange, and the encoder is located below the output flange and used for measuring angles. When the output shaft of the series elastic driver is subjected to an external instantaneous load, the load transmits the impact force to the spring through the pull rope so as to absorb the influence of the impact force, so that the external impact is reduced, and the safety of man-machine interaction is improved. The device has the advantages of being simple in structure, small in size, high in research value, wide in application prospect and the like, and is suitable for interaction scenes between a robot and people or between the robot and the environment.

Description

Technical Field

[0001] The invention belongs to the field of robots, and in particular relates to a parallel-arranged series elastic driver. Background Art

[0002] With the continuous development of modern precision manufacturing technology, robotics technology has been widely used in the fields of industry and medicine, such as rehabilitation robots, exoskeleton robots and industrial robotic arms. At present, upper limb rehabilitation robots are mainly divided into two types: end-traction type and exoskeleton type. The end-traction upper limb rehabilitation robot achieves the purpose of upper limb rehabilitation by driving the patient's hand. Its advantages include simple structure, flexibility and ease of use, large workspace and wide application. The exoskeleton upper limb rehabilitation robot can provide comprehensive and detailed rehabilitation training for the patient's entire upper limb. Its rehabilitation parts include shoulders, arms and hands, but its mechanical structure is more complex, and the control strategy and use process are also more complex. It is necessary to accurately match the patient's upper limb position and joints to avoid injury. A common problem is that when the patient is in the relaxation and spasticity stage, the muscle strength is extremely low, and rehabilitation training cannot be performed independently, and it cannot effectively avoid danger in an emergency.

[0003] Series elastic actuator (SEA) is a widely used passive compliant actuator that provides a certain degree of passive compliance when active compliance control fails (such as power failure, software and hardware loss of control, etc.) by setting elastic elements in series between traditional drive units (such as servo motors, hydraulics, etc.) and connecting rods. Compared with traditional rigid actuators, SEA has precise force control capabilities, low mechanical impedance, impact resistance and energy storage capabilities, and can provide soft interactive forces during human-computer interaction.

[0004] However, different current series elastic actuator designs still have some defects in ensuring the safety and stability of human-machine interaction, such as complex joint structure, high energy consumption, complex control and low safety. Therefore, the present invention aims to provide a solution with simple structure, small size and suitable for human-machine interaction scenarios in different stiffness environments. Summary of the invention

[0005] The object of the present invention is to provide a parallel-arranged series elastic driver, which aims to overcome the defects of the series elastic driver in the prior art, such as relatively complex structure, difficult control and low safety, and realize safer and more reliable human-computer interaction.

[0006] The specific approach to the present invention is as follows:

[0007] The parallel-arranged serial elastic actuator is mainly composed of the following parts: Bowden cable, special spring, turntable and joint input and output flange, including output flange 1, output part 2, rotor 3, Bowden cable 4, bearing 5, special spring 6 and input flange 7. The overall structure of the device is compact and light, and can adapt to different application scenarios. Its rope drive design allows the motor to be separated from the robot frame, thereby reducing the weight of the robot body. The device can output up to 30Nm of torque to meet the needs of robot-assisted rehabilitation training. Bearings are provided between the output flange and the output shaft and rotor to bear non-torque loads, thereby realizing relative rotation between the input part and the output part; the output shaft, rotor, special spring and bearing are all installed on the output flange, the servo motor is fixed above the input flange, and the encoder is installed below the output flange to measure the relative rotation angle between the input and output. There are four special springs in total, which are divided into two groups and arranged in parallel on both sides of the output flange. One end is connected to the rotor through the Bowden cable, and the other end is fixed on the output shaft.

[0008] The rotor is designed with two Bowden wire groove structures and two sets of symmetrical threaded holes. When the rotor is installed through the bearing, the parallel arrangement of one end of the spring can be rotated around the outer periphery of the rotor along the parallel groove to ensure the linearity of the tension. The encoder positioning hole and threaded hole are designed on the lower side of the output flange to measure the relative rotation angle between the input and output shafts after the encoder is installed in place.

[0009] The advantage of this patent is that it has a simple structure and is easy to process and assemble. It only needs to replace the spring with the required stiffness according to different usage scenarios to output the required linear stiffness and bidirectional rotation torque. The springs arranged in parallel help to alleviate external impacts and reduce possible damage to personnel or the machine itself. They have good passive compliance and significantly improve the safety of human-machine interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the overall structure of the parallel-arranged series elastic actuator in the present invention.

[0011] Figure 2 It is a parameterized model diagram of the parallel-arranged series elastic actuator in the present invention.

[0012] Figure 3 It is a cross-sectional schematic diagram of the parallel-arranged series elastic actuator of the present invention.

[0013] In the attached drawings, the meanings of the numbers are: output flange-1, output member-2, rotor-3, Bowden cable-4, bearing-5, special spring-6, input flange-7. DETAILED DESCRIPTION

[0014] The present invention is further described below in conjunction with the accompanying drawings:

[0015] See also Figures 1 to 3 The utility model relates to a spring-type linear series elastic driver, which is specially designed to connect the servo motor to the input flange 7 of the series elastic driver through screws. The bearing 5 is mounted on the inner wall of the output flange 1. One side of the output flange 1 is provided with a spring mounting component according to the height of the rotor 3. There are four special springs 6, which are respectively installed between the output member 2 and the input flange 1, and are arranged in parallel and in an antagonistic layout. One side of the spring 6 is fixed to the screws on the rotor 3 at a distance of 180 degrees from the outer periphery of the rotor 3 in parallel, and the output shaft and the output flange are fixedly connected by threaded screws. An encoder is installed near the lower side of the output flange 1.

[0016] The power transmission process is described as follows: the input torque is provided by the servo motor. The output shaft of the motor is integrated with the rotor 3, and the rotation of the series elastic driver rotor 3 is achieved through the rotation of the motor shaft. When the external load is fixed to the output member 2, the antagonistic springs 6 located on both sides of the output flange provide the necessary torque through the parallel arrangement connected to the rotor 3 and one end of the spring 6.

[0017] like Figure 2 As shown in the figure, the parametric model of the series elastic actuator is constructed based on an ideal physical model, in which the friction between the Bowden cable, special spring, turntable and mass / inertia are ignored. The model assumes that the turning radius of the turntable is R, A 1 ,A 2 They are special springs connected to the output end, the elastic coefficient of the special spring is k, and the pre-compression amount is x 0 , F 1 ,F 2 are the forces exerted by the compression spring on the rope end, and the torque output by the motor through the reducer is T d , the output torque at the output end of the driver is T s .

[0018] When there is a relative angle Δξ between the motor output disc and the turntable, the linear deformation Δx produced by the special spring can be obtained as:

[0019] Δx=2Rsin(Δξ)≈2RΔξ Formula (1.1)

[0020] At the same time, it is also determined that for the special spring installed at the output end, when there is a relative angle Δξ between the output disk of the motor and the turntable, the force generated by the special spring is:

[0021] F 1,2 = k(x 0 ±Δx) Formula (1.2)

[0022] Similarly, the torque generated by the compression spring is:

[0023] τ=2kRΔx Formula (1.3)

[0024] Then the equivalent rotational stiffness k of the designed series elastic actuator is s It can be expressed as:

[0025]

[0026] The present invention is not limited to the above-mentioned implementation cases. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some of the technical features according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A parallel arrangement type series elastic actuator, characterized by: The driver is mainly composed of four parts, including Bowden cable, special spring, turntable and joint input and output flange. Bearings are provided between the output flange, the output shaft and the rotor to bear non-torque loads and realize relative rotation between the input part and the output part; the output shaft, rotor, spring and bearings are all installed above the output flange, the servo motor is fixed above the input flange, and the encoder is installed below the output flange to measure the relative rotation angle between the input and output; there are four special springs, which are divided into two groups and arranged in parallel and placed on both sides of the output flange, one end of each spring is connected to the rotor through a Bowden cable, and the other end is fixed on the output shaft.

2. The parallel-arranged series elastic actuator according to claim 1, characterized in that: The rotor is provided with two Bowden wire groove structures and two groups of symmetrical threaded holes. When the rotor is installed in place through the bearing, the parallel arrangement of one end of the spring can rotate a certain angle around the outer periphery of the rotor along the parallel arrangement groove to ensure the linearity of the tension.

3. The parallel-arranged series elastic actuator according to claim 1, characterized in that: An encoder positioning hole and a threaded hole are provided on the lower side of the output flange, so as to realize accurate measurement of the relative rotation angle between the input and output shafts after the input flange of the encoder is in place.

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