SOFT ACTUATOR, ITS WORKING METHOD AND ROBOT
20230150121 · 2023-05-18
Assignee
Inventors
Cpc classification
F16D27/14
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Y10S901/19
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
F16D27/12
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
Abstract
A soft actuator, its working method and robot are provided. The soft actuator includes a power input shaft, and multiple electromagnetic clutches are coaxially installed in series on the power input shaft. A bending elastic part is arranged between the thrust plate of each electromagnetic clutch and the gear frame of the electromagnetic clutch. The bending elastic part is installed on the sleeve of the gear frame and in contact with the baffle of the gear frame. The bending elastic part is connected with the clutch output gear of the electromagnetic clutch through the gear frame. The gear frame is fixedly connected with the clutch output gear and rotates coaxially.
Claims
1. A soft actuator, comprising a power input shaft, wherein a plurality of electromagnetic clutches are coaxially connected in series to the power input shaft, wherein a bending elastic part is arranged between a thrust plate corresponding to each electromagnetic clutch and an electromagnetic clutch gear frame, the bending elastic part is installed on a sleeve of the gear frame and contacts with a baffle of the gear frame, the bending elastic part is connected with a clutch output gear of the electromagnetic clutch through the gear frame, and the gear frame is fixedly connected with the clutch output gear and rotates coaxially.
2. The soft actuator according to claim 1, wherein the gear frame is securely connected to the clutch output gear using an internal and external gear with a same modulus.
3. The soft actuator according to claim 1, wherein the soft actuator comprises two bending elastic parts arranged symmetrically with one end of each bending elastic part set on both ends of gear frame sleeves and the other end contacted with the thrust plate.
4. The soft actuator according to claim 1, wherein the thrust plate is fixed to an outer shell which is disposed outside the electromagnetic clutch.
5. The soft actuator according to claim 1, wherein a number of electromagnetic clutches is more than or equal to 3; a number of bending elastic parts added to the soft actuator can be changed through different combinations of power-on states of each electromagnetic clutch to realize different stiffness adjustments of the soft actuator.
6. The soft actuator according to claim 4, wherein a power output shaft is arranged on one side of the outer shell, and the outer shell is connected with the power input shaft by a bearing; a force sensor mounted on the power output shaft is further comprised to measure an output torque of the power output shaft.
7. The soft actuator according to claim 6, wherein encoders are set on the power input shaft and the power output shaft, respectively; the power input shaft is connected to a driving component, and the driving component and the encoder are connected to the controller, respectively.
8. The soft actuator according to claim 1, wherein the soft actuator further comprises a conductive slip ring that is mounted on the power input shaft.
9. A working method of the soft actuator according to claim 1, comprising: when an electromagnetic coil is energized, a generated magnetic force adsorbs a passive friction disc on an active friction disc, a torque of the power input shaft is transmitted to the passive friction disc through the two friction discs, finally, the torque is transmitted from the clutch output gear to the gear frame and then transmitted to the outer shell through the thrust plate in contact with the bending elastic part; when the electromagnetic coil is powered off, the electromagnetic clutch coil loses its magnetic force, at the same time, the passive friction disc and the active friction disc are separated and a power transmission is interrupted; the electromagnetic coil and the active friction disc will rotate independently with the power input shaft; after a power state change of the electromagnetic coil, whether the bending elastic part is connected to a power transmission chain is controlled, and an output stiffness of the soft actuator is adjusted by a stiffness of the bending elastic part.
10. A robot, wherein the robot adopts the soft actuator according to claim 1.
11. The working method according to claim 9, wherein in the soft actuator, the gear frame is securely connected to the clutch output gear using an internal and external gear with a same modulus.
12. The working method according to claim 9, wherein the soft actuator comprises two bending elastic parts arranged symmetrically with one end of each bending elastic part set on both ends of gear frame sleeves and the other end contacted with the thrust plate.
13. The working method according to claim 9, wherein in the soft actuator, the thrust plate is fixed to an outer shell which is disposed outside the electromagnetic clutch.
14. The working method according to claim 9, wherein in the soft actuator, a number of electromagnetic clutches is more than or equal to 3; a number of bending elastic parts added to the soft actuator can be changed through different combinations of power-on states of each electromagnetic clutch to realize different stiffness adjustments of the soft actuator.
15. The working method according to claim 13, wherein in the soft actuator, a power output shaft is arranged on one side of the outer shell, and the outer shell is connected with the power input shaft by a bearing; a force sensor mounted on the power output shaft is further comprised to measure an output torque of the power output shaft.
16. The working method according to claim 15, wherein in the soft actuator, encoders are set on the power input shaft and the power output shaft, respectively; the power input shaft is connected to a driving component, and the driving component and the encoder are connected to the controller, respectively.
17. The working method according to claim 9, wherein the soft actuator further comprises a conductive slip ring that is mounted on the power input shaft.
18. The robot according to claim 10, wherein in the soft actuator, the gear frame is securely connected to the clutch output gear using an internal and external gear with a same modulus.
19. The robot according to claim 10, wherein the soft actuator comprises two bending elastic parts arranged symmetrically with one end of each bending elastic part set on both ends of gear frame sleeves and the other end contacted with the thrust plate.
20. The robot according to claim 10, wherein in the soft actuator, the thrust plate is fixed to an outer shell which is disposed outside the electromagnetic clutch.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The drawings accompanying the specification forming part of the present invention are used to provide a further understanding of the present invention, the schematic embodiments of the present invention and its description are used to explain the present invention and do not constitute an improper qualification of the present invention
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[0058] The spacing or size between parts is exaggerated to show the position of each other in the diagrams, the diagrams are only for schematic use.
[0059] Among them: 1. power input shaft, 2. electromagnetic clutch, 3. power output shaft, 4. clutch output gear, 5. outer shell, 6. electromagnetic clutch gear frame, 7. baffle, 8. bending elastic part, 9. sleeve, 10. electromagnetic coil, 11. active friction disc, 12. passive friction disc, 13. driving motor, 14. power input shaft encoder, 15. conductive slip ring, 16. power output shaft encoder, 17. power input shaft rotation angle θ.sub.1, 18. power output shaft rotation angle q, 19. compression deflection angle θ.sub.2, 20. thrust plate, 21. force sensor, 22. rigid component.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0060] It should be noted that the following details are illustrative and are intended to provide further explanations for the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by ordinary technicians in the technical field to which the present invention belongs.
[0061] It is important to note that the term used here is only intended to describe the specific implementation, not intended to limit the exemplary implementation based on the present invention. As used here, the singular form is also intended to include the plural form unless explicitly stated otherwise in this invention. In addition, it should be understood that when the terms ‘include’ and/or ‘comprise’ are used in this specification, they indicate the presence of features, steps, operations, devices, components, and/or combinations of them;
[0062] As the existing technology introduced in the background technology, the control algorithm is complex, the variable stiffness range is limited, and the mechanism is complex, which leads to the problems of coupling interference, large friction in the stiffness adjustment mechanism, small joint rotation angle, slow variable stiffness response speed, and large mechanical disturbance during stiffness adjustment, the present invention provides a soft actuator.
Embodiment 1
[0063] In a typical embodiment of the present invention, a soft actuator is shown in
[0064] Referring to
[0065] In other examples, as shown in
[0066] As shown in
[0067] Specifically, the power input shaft 1 is used to input torque, and the torque is transmitted to the electromagnetic clutch gear frame 6 through the clutch output gear 4 firstly, and then transmitted through the thrust plate 20 that is in contact with the bending elastic part. Whether the bending elastic part is connected to the power transfer chain is controlled by changing the on-state of the electromagnetic coil of the electromagnetic clutch. The output stiffness of the soft actuator is adjusted by the stiffness of the bending elastic part. The number of bending elastic parts 8 added to the soft actuator is controlled through the different combinations of the on-state of multiple electromagnetic clutches 2 to realize different stiffness adjustments of the soft actuator.
[0068] As shown in
[0069] The number of electromagnetic clutch 2 is more than or equal to 3. The number of bending elastic parts added to the soft actuator can be changed through different combinations of the power-on states of each electromagnetic clutch 2, which realize the different stiffness adjustments of the soft actuator.
[0070] Referring to
[0071] Refer to
[0072] The power input shaft encoder 14 of this embodiment uses a rotary incremental encoder with gears, which is connected to the power input shaft 1 through gear transmission to measure the rotation angle of the power input shaft 1.
[0073] The power input shaft 1 is connected with the driving component, and the driving component of this embodiment adopts the driving motor 13. The driving motor 13 is coaxially installed with the power input shaft 1 and the coupling. Firstly, the motor torque is transmitted to the power input shaft 1 through the coupling, and then it is transmitted to the electromagnetic clutch 2 through the input shaft, finally, it is transmitted to the bending elastic part 8 through the input torque of the electromagnetic clutch gear frame. The output torque of the elastic part finally becomes the driving torque of the outer shell.
[0074] The driving component and the encoders are connected to the controller respectively. The controller can be a PID controller, which can be used for the trajectory tracking effect of the soft actuator under different stiffness.
[0075] The soft actuator also includes a conductive slip ring 15, the conductive slip ring 15 and the electromagnetic clutch 2 are coaxially mounted on the power input shaft 1, and the conductive slip ring 15 for rotational connectivity of the internal electromagnetic clutch 2 to prevent entanglement caused by lines rotation, so the soft actuator can made unlimited continuous rotation with a wide range of operating angles.
Embodiment 2
[0076] This embodiment analyzes the theoretical model of the soft actuator in embodiment 1 and then analyzes the theoretical model of the bending elastic element.
[0077] Dynamics Modeling of Soft Actuator:
M({umlaut over (q)})+C({dot over (q)})+G(q)+τ.sub.d(t)=τ(K.sub.N,θ.sub.2)
J.sub.1{umlaut over (θ)}.sub.1+D.sub.1{dot over (θ)}.sub.1+τ(K.sub.N,θ.sub.2)=μ
θ.sub.2=θ.sub.1−q
[0078] where q, θ.sub.1, θ.sub.2 are respectively the bending elastic part 8, power input shaft rotation angle 17, and the compression deflection angle 19, M, J are respectively the reflection inertia of the power output shaft and the power input shaft, C, D are respectively the equivalent damping coefficients of the power output shaft and the power output shaft, G(q) is used to compensate the gravity torque of the power output shaft, τd(t) is used to compensate the load torque of the soft actuator during operation, the additional torque generated by friction, the internal damping and the uncertain disturbance torque caused by the manufacturing accuracy of the soft actuator. μ represents the equivalent torque on the driving motor, and τ(γ, θ.sub.2) is the elastic torque of the bending elastic part 8.
[0079] The value of τ is derived from τ=K.sub.N×θ.sub.2, where K.sub.N is the output stiffness of the soft actuator.
[0080] Referring to
[0081] Fi is the reaction force of the thrust plate 20, r is the distance from the center of the power input shaft 1 to the bending elastic part 8 (0.026 m), and K is the stiffness of a single bending elastic part (Nm/rad).
[0082] The output stiffness of the soft actuator is the combined action of four bending elastic parts 8. To prevent damage to the soft actuator, an electromagnetic clutch 2 is normally closed, and the corresponding bending elastic part 8 (K2) is controlled to access the system. The other three bending elastic parts 8 are arranged and combined. The soft actuator has a total of 8 different stiffness output states. The theoretical stiffness values of the bending elastic parts are shown in Table 1-1:
TABLE-US-00001 Output stiffness no Theoretical stiffness value K1 0.5 K2 1.2 K3 2.4 K4 4.8
[0083] Bending elastic parts 8 theoretical energy storage formula:
[0084] Finally, the results of the change of the torque of the bending elastic part with the deflection angle and the elastic potential energy of the bending elastic part with the deflection angle are shown in
[0085] Experimental Study:
[0086] For the bending elastic parts 8 with different stiffness, measure the relationship between the torque and the deflection angle of the soft actuator. The torque of the actuator is measured by the force sensor, and the compression deflection angle θ.sub.2 can be obtained by the difference between the input shaft encoder and the soft output shaft encoder. The solid line in
TABLE-US-00002 TABLE 2-1 soft actuator output stiffness fitting curve table Number P.sub.1 P.sub.2 Poly K1 0.4802 (0.4733, 0.487) 0.02535 (0.0173, 0.03339) Poly K2 1.173 (1.151, 1.195) 0.08818 (0.06225, 0.1141) Poly K3 2.499 (2.46, 2.537) 0.03294 (−0.01163, 0.07751) Poly K4 4.398 (4.31, 4.486) 0.4578 (0.3547, 0.5609)
[0087] Where K1=0.4802x+0.02535; K2=1.173x+0.08818; K3=2.499x+0.03294; K4=4.398x+0.4578; From
TABLE-US-00003 TABLE 2-2 Different stiffness settings of soft actuator Stiffness no. (Nm/rad) K2 + K3 + K1 + K2 + K1 + K2 + K1 + K2 + K2 K2 + K1 K2 + K3 K2 + K4 K4 K4 K3 K3 + K4 Value 0.4802 1.6532 3.672 5.571 8.07 6.0512 4.1522 8.5502
[0088] Step Signal Corresponding Test:
[0089] The designed soft actuator has two output stiffnesses, lower output stiffness K2 (0.4802 Nm/rad) and higher output stiffness K1+K2+K3 (4.1522 Nm/rad). To obtain better trajectory-tracking experimental results, a PID controller is designed to study the trajectory-tracking effect of the soft actuator under different stiffnesses. The step signal: 0-120 degrees is selected for trajectory tracking experiments, and the PID parameter values are shown in Table 3-1.
TABLE-US-00004 TABLE 3-1 PID controller parameters PID Parameters Value Kp 0.235 Ki 0.0025 Kd 0.001 Ts 0.001 s
[0090] The experimental results of step response are shown in
[0091] Sine Signal Trajectory Tracking Experiment:
[0092] Test for the sinusoidal signal target tracking performance of soft actuator under fixed stiffness, signal selection: sinusoidal signal: Use
to perform trajectory tracking experiments, excitation signal parameters are set as shown in Table 4-1:
TABLE-US-00005 TABLE 4-1 Parameter setting of the sine signal Signal source Sampling frequency ω Phase angle Sine 0.001 s 2π/5 0°
[0093] As shown in
[0094] Continuous Variable Stiffness Experiment:
[0095] When there is no load, adjust the stiffness of the soft actuator from higher stiffness K1234 (K1+K2+K3+K4, 8.5502 Nm/rad) to lower stiffness K12 (K1+K2, 1.6532 Nm/rad) during the sinusoidal function tracking
[0096] As shown in
[0097] Collision Safety Experiment:
[0098] To fully detect the adaptability and safety of the soft actuator, a collision test was performed on the designed soft actuator with ten collisions.
[0099] As shown in
[0100] Firstly, analyze the stiffness adjustment principle and mechanical structure design of the soft actuator, and establish its mathematical model, the relationship between the torque and the spring displacement angle is obtained after testing the static stiffness performance of the soft actuator. Then, carry out the actuator step signal tracking experiment to verify the target angle tracking effect of the soft actuator, and the sine signal trajectory tracking experiment is also carried out to verify the tracking performance of the soft actuator in the fixed stiffness output state. Finally, carry out the continuous variable stiffness experiment to verify the variable stiffness performance and the collision safety experiments to verify the shock absorption and energy storage capacity of the soft actuator.
Embodiment 3
[0101] The present invention also discloses a working method of the soft actuator, including the following contents:
[0102] When the electromagnetic coil 10 is energized, a certain magnetic force is generated to adsorb the passive friction disc 12 on the active friction disc 11, and the torque of the power input shaft is transmitted to the passive friction disc 12 through two friction discs. Finally, the torque is transmitted from the clutch output gear 4 to the electromagnetic clutch gear frame 6 and then transmitted to the outer shell 5 through the thrust plate in contact with the bending elastic part 8.
[0103] When the electromagnetic coil 10 is powered off, the coil of electromagnetic clutch 2 loses its magnetic force, at the same time, the passive friction disc 12 and the active friction disc 11 are separated and the power transmission is interrupted. The electromagnetic coil 10 and the active friction disc 11 will rotate independently with the power input shaft 1. After the power state change of the electromagnetic coil 10, by connecting or disconnecting the bending elastic part 8 to the power transmission chain is controlled, the output stiffness of the soft actuator is adjusted by the stiffness of the bending elastic part.
[0104] When the bending spring with relatively small stiffness is connected to the soft actuator, the output stiffness of the soft actuator approaches infinity. When the completely rigid component is connected to the soft actuator, the output stiffness of the soft actuator is almost infinite. At this moment, the output stiffness of the soft actuator depends on the choice of different stiffness materials of the bending elastic element.
[0105] Specifically, the number of soft actuators connected to multiple elastic parts is controlled by the electromagnetic clutch to realize the adjustment of output stiffness by turning on or off the electromagnetic clutch 2 and adding or separating the corresponding bending elastic parts from the soft actuator.
Embodiment 4
[0106] The present invention also provides a robot that works by using the soft actuator in embodiment 1.
[0107] The above-mentioned embodiments are only the preferred embodiments of the present invention which are not used to limit the present invention. For technicians in this field, the present invention could have various changes and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principles of the present invention shall be included within the protection scope of this invention.