CN111113399A

CN111113399A - Linear motion joint flexible mechanical arm based on series elastic driver

Info

Publication number: CN111113399A
Application number: CN202010024547.0A
Authority: CN
Inventors: 周乐来; 宋召鹏; 李贻斌; 荣学文; 李健华; 刘大宇
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-01-10
Filing date: 2020-01-10
Publication date: 2020-05-08
Also published as: NL2026200A; NL2026200B1; ZA202003802B

Abstract

A linear motion joint flexible mechanical arm based on a series elastic driver comprises a joint arm and two series elastic drivers; the joint arm comprises a shoulder arm, an upper arm and a lower arm which are sequentially hinged, a first series elastic driver is installed in the shoulder arm, the output end of the first series elastic driver is connected with the upper arm through a first slider-crank mechanism, a second series elastic driver is installed in the upper arm, and the output end of the second series elastic driver is hinged with the lower arm through a second slider-crank mechanism. The invention has compact structure, good flexibility and large rigidity change rate, can ensure the flexibility of motion and the safety of human-computer interaction, introduces a crank-slider structure at a joint, and realizes the transformation of the movement of a lead screw and the rotation of the joint through the structure.

Description

Linear motion joint flexible mechanical arm based on series elastic driver

Technical Field

The invention relates to a linear motion joint flexible mechanical arm, and belongs to the technical field of mechanical arms of robots.

Background

With the development of science and technology, the aging of the population of countries in the world is becoming more serious and the labor cost is increasing, and the robot is urgently required to replace human beings to complete work in more fields. The industrial robots that have been used most widely before have not been able to meet the increasing demands of the human society, and therefore the development of a new generation of more friendly robots is becoming a key requirement in the current field of robotics.

To meet new social needs, new generation robots are first faced with more and more human-computer interactions. The robot is not limited to a factory closed environment, but is cooperated with a human or gradually merged into a human society to assist or replace the human to complete daily activities. Aiming at the uncertainty and safety in the human-computer interaction process, the ideal mechanical arm has the compliance characteristic similar to that of a human arm, and the motion speed and the motion damping of the mechanical arm can be actively changed according to the change of an external environment. This requires the robot body, particularly the joint area, to be changed from a rigid drive to a flexible drive. The control technology of the robot should also be developed from conventional position control to force control that better embodies the compliance characteristics.

In the field of current compliant robotic arms, some actively change joint flexibility by using a compliant control algorithm, which puts high demands on both the controller and the sensor. In addition, the flexible joint is passively changed by introducing an elastic element, and the method has a simple control system, so that the method becomes a research hotspot of the flexible drive at present.

Chinese patent document CN108608458A discloses a tandem drive compliant mechanical arm joint, which comprises a joint motor, a harmonic reducer, a four-bar linkage, a joint housing, and an output housing, wherein a leaf spring is fixedly connected above a leaf spring base, the four-bar linkage is arranged above the leaf spring, a driving bevel gear is driven by a stiffness motor, a driven bevel gear is driven by gear engagement, so as to drive a cam to rotate, and the position of a supporting point of a four-bar saddle-shaped bracket on the leaf spring is changed due to the contact of the cam and a connecting point of the four-bar linkage, so as to change the stiffness of the joint, and realize the controllable adjustment of the stiffness of the joint. However, the method has a complex structure and a large volume, and is difficult to be practically applied to the mechanical arm.

CN104924320A discloses a three-degree-of-freedom flexible mechanical arm based on a series elastic driver, which comprises a steering engine in a joint, a drive conversion module and a connecting arm between the joints, wherein the three-degree-of-freedom flexible mechanical arm is arranged by imitating the degree of freedom of a human body, the adopted drive conversion module can be converted from rigid drive to elastic drive, the flexibility of motion and the safety of human-computer interaction are ensured, and the three-degree-of-freedom flexible mechanical arm is simple to assemble and easy to arrange. However, the spring of the device is limited in size, limited in deformation range and small in rigidity change range.

Disclosure of Invention

The invention aims to provide a novel mechanical arm based on series elastic driving, aiming at the requirements of the current society on a cooperative robot and overcoming the defects of the traditional driving mode. The mechanical arm has the advantages of compact structure, large output torque, simple control method, large movement space and the like.

The invention discloses a linear-motion joint flexible mechanical arm based on a series elastic driver, which adopts the following technical scheme:

the mechanical arm comprises a joint arm and two elastic drivers connected in series; the joint arm comprises a shoulder arm, an upper arm and a lower arm which are sequentially hinged, a first series elastic driver is installed in the shoulder arm, the output end of the first series elastic driver is connected with the upper arm through a first slider-crank mechanism, a second series elastic driver is installed in the upper arm, and the output end of the second series elastic driver is connected with the lower arm through a second slider-crank mechanism.

The shoulder arm comprises a left shoulder connecting rod and a right shoulder connecting rod, and one end of the left shoulder connecting rod is connected with one end of the right shoulder connecting rod.

The upper arm comprises a left upper arm and a right upper arm, and the left upper arm is connected with the right upper arm through a fixing piece.

The lower arm is fork-shaped (one end is U-shaped), and two sides of the fork-shaped are respectively hinged with the left upper arm and the right upper arm of the upper arms.

The first slider-crank mechanism is connected with the upper arm through a fixing piece, and the fixing piece is connected to the upper arm and hinged to the output end of the first slider-crank mechanism.

The crank sliding block mechanism comprises a sliding shaft, a transmission rod and a sliding sleeve, wherein two ends of the sliding shaft are respectively connected with the output end of the serial elastic driver and the transmission rod, the sliding shaft is sleeved in the sliding sleeve, and the sliding sleeve is fixedly connected to a shoulder arm or an upper arm.

The series elastic driver comprises a driving motor, a spring spacer, a die spring, a shell, a transmission shaft, a ball screw and a joint connecting rod; a guide shaft is connected between the driving motor and the shell, a spring spacing piece is sleeved on the guide shaft, and die springs are arranged between the spring spacing piece and the driving motor and between the spring spacing piece and the shell; a transmission shaft is arranged in the shell and connected with a main shaft of the motor; the transmission shaft is fixedly connected with a nut, the ball screw is sleeved in an inner hole of the transmission shaft and connected with the nut, and the joint connecting rod is connected with the ball screw. The driving motor comprises a motor box body, a motor rotor, a motor stator and a motor spindle, wherein the motor stator and the motor rotor are both arranged in the motor box body, and the motor rotor is fixed on the motor spindle. And a Hall sensor is arranged in the motor stator.

When the device works, the motor in the series elastic driver drives the transmission shaft to rotate according to the control signal. The transmission shaft drives the nut to rotate, so that the ball screw and the joint connecting rod stretch out and draw back. The joint connecting rod drives the upper arm or the lower arm to rotate through the crank-slider mechanism. When the upper arm and the lower arm are impacted by the outside, the serial elastic driver moves integrally through the guide shaft except the spring spacing part, so that the die spring is compressed, the die spring absorbs the impact of the fluctuation of the external load, and the mechanical flexibility of the joint is realized.

The invention has compact structure, good flexibility and large rigidity change rate, and can ensure the flexibility of movement and the safety of human-computer interaction. Has the following characteristics:

1. the dynamic characteristics of the mechanical arm are more flexible, and the safety is improved.

2. The advantages of large output torque of the torque motor, simple and compact structure and the like are fully utilized, and the driving part of the robot can be miniaturized and lightened.

3. The double-spring design improves the rigidity change rate of the driver, and the robot joint can bear bidirectional high-load impact.

4. The crank-slider mechanism is introduced, the translation of the movement of the lead screw and the rotation of the joint is realized through the structure, and the moving space of the mechanical arm is greatly enlarged.

Drawings

Fig. 1 is a schematic view of the overall structure of the robot arm of the present invention.

FIG. 2 is a schematic view of the right shoulder link and right upper arm of the robotic arm of the present invention shown removed.

Fig. 3 is a schematic structural diagram of the appearance of the series elastic driver in the invention.

Fig. 4 is a schematic view of the internal structure of the series elastic driver of the present invention.

In the figure: 1. the novel motor comprises a base, 2, a left shoulder connecting rod, 3, a right shoulder connecting rod, 4, a left upper arm, 5, a right upper arm, 6, a lower arm, 7, a fixing piece, 8, a first series elastic driver, 9, a second series elastic driver, 10, a first crank block mechanism, 11, a second crank block mechanism, 12, a sliding sleeve, 13, a bush, 14, a sliding shaft, 15, a transmission rod, 16, a motor box cover, 17, a motor box body, 18, a guide shaft, 19, a die spring, 20, a spring spacer, 21, a housing box body, 22, a housing box cover, 23, a joint connecting rod, 24, a motor stator, 25, a motor rotor, 26, a motor spindle, 27, a flat key, 28, a transmission shaft, 29, a cross roller bearing, 30, a ball screw, 31, a nut, 32, a thin-wall bearing, 33, an oil-free bush, 34, a ball bearing and 35, and a spindle.

Detailed Description

As shown in figure 1, the linear motion joint flexible mechanical arm based on the series elastic drivers comprises a joint arm and two series elastic drivers. The entire articulated arm is attached to the base 1. The articulated arm comprises a shoulder arm, an upper arm and a lower arm 6 which are sequentially hinged together, and two joints are formed between the shoulder arm and the upper arm and between the upper arm and the lower arm 6.

The shoulder arm is composed of a left shoulder connecting rod 2 and a right shoulder connecting rod 3, and one ends of the left shoulder connecting rod 2 and the right shoulder connecting rod 3 are connected together and fixed on the base 1 through bolts. A first series elastic driver 8 is installed between the left shoulder connecting rod 2 and the right shoulder connecting rod 3, and a spring spacer 20 on the first series elastic driver 8 is fixedly connected to the left shoulder connecting rod 2 and the right shoulder connecting rod 3 (see fig. 3). The output of the first series elastic driver 8 is hinged to the upper arm by a first slider-crank mechanism 10.

The upper arm comprises a left upper arm 4 and a right upper arm 5, and a fixing part 7 is connected between the left upper arm 4 and the right upper arm 5. One end of the left upper arm 4 and one end of the right upper arm 5 are respectively hinged with the left shoulder connecting rod 2 and the right shoulder connecting rod 3 through rotating shafts, and meanwhile, the fixing piece 7 is connected with the output end of the first series elastic driver 8 through the first crank block mechanism. A second series elastic driver 9 is arranged between the left upper arm 4 and the right upper arm 5 and is fixed with the left upper arm and the right upper arm. The spring spacers on the second series elastic driver 9 are fixed to the left upper arm 4 and the right upper arm 5 (see fig. 3). The output of the second series elastic actuator 10 is hinged to the lower arm 6 through a second slider-crank mechanism 11.

One end of the lower arm 6 is in a U-shaped fork structure, and as shown in fig. 2, two sides of the U-shaped fork are respectively hinged with the left upper arm 4 and the right upper arm 5.

The first crank-slider mechanism 10 and the second crank-slider mechanism 11 enable two joints between the shoulder arm and the upper arm and between the upper arm and the lower arm 6 to adopt a crank-slider mechanism driving mode, the moving space of the mechanical arm is greatly expanded, and the structure of the mechanical arm is shown in fig. 2. For the sake of easy viewing of the movement pattern of the slider-crank structure, the sliding sleeve 12, the graphite bushing 13, the sliding shaft 14 and the transmission rod 15 can be regarded as one slider-crank structure. The two ends of the slide shaft 12 are respectively hinged with a joint link 23 (see fig. 3) and a transmission rod 15 of the tandem elastic driver. The transmission rod of the first series elastic actuator 8 is hinged to the fixed part 7 and the transmission rod of the second series elastic actuator 9 is hinged to the lower arm 6. The sliding shaft 14 is sleeved in the sliding sleeve 12, a bushing 13 (graphite bushing) is arranged in an inner hole of the sliding sleeve 12, and the sliding shaft 14 slides in the bushing 13. The sliding sleeve 12 is fixed to the left and right shoulder links 2, 3 (for the first series elastic driver 8) or the left and right upper arms 4, 5 (for the second series elastic driver 9).

The first and second series

elastic drivers

8 and 9 are identical in structure, and as shown in fig. 3 and 4, the series elastic drivers include a driving motor, a spring spacer 20, a die spring 19, a housing, a transmission shaft 28, a ball screw 30, and a knuckle link 23. Four guide shafts 18 are connected between the driving motor and the shell, and the four guide shafts 18 are fixed on the motor box body 17 and the shell box body 21 through screws. The spring spacer 20 is mounted on four guide shafts 18 for movement along the guide shafts. The spring spacers 20 of the first series elastic actuator 8 are fixedly connected to the left shoulder link 2 and the right shoulder link 3, and the spring spacers 20 of the second series elastic actuator 9 are fixedly connected to the left upper arm 4 and the right upper arm 5. Mold springs 19 are provided between the spring spacer 20 and the driving motor and between the spring spacer 20 and the housing. The housing includes a housing case 21 and a housing case cover 22 attached to the housing case 21. A transmission shaft 28 is arranged in the shell, and two ends of the transmission shaft 28 are supported on bearing seats of the shell box body 21 and the shell box cover 22 through a cross roller bearing 29 and a thin-wall bearing 32 respectively. The drive shaft 28 is connected to the motor spindle 26 by a flat key 27. The transmission shaft 28 is fixedly connected with a nut through a screw, and the ball screw 30 is sleeved in an inner hole of the transmission shaft 28 through the oilless bushing 13 and is in threaded connection with the nut. The knuckle linkage 23 is connected to a ball screw 30, and the ball screw 30 is connected to a fixing nut 31 in the housing case 21. The articulated links 23 of the first series elastic drive 8 are connected to the left upper arm 4 and the right upper arm 5 by a first slider-crank mechanism 10. The articulated link of the second series elastic actuator 9 is likewise connected to the lower arm 6 via a second slider-crank mechanism 11.

The driving motor comprises a motor box cover 16, a motor box body 17, a motor rotor 25, a motor stator 24 and a motor spindle 26, wherein the motor stator 24 is installed in the motor box body 17, the motor rotor 25 is arranged in the motor box body 17, and the motor box cover 16 is installed on the motor box body 17 and tightly presses the motor stator 24. The motor stator 24 incorporates a hall sensor. The motor rotor 25 is fixed to the motor spindle 26 by a spindle fixing piece 35. The motor spindle 26 is supported at both ends by two ball bearings 34 on bearing blocks of the motor case 17 and the motor case cover 16.

When the flexible joint mechanical arm works, a motor rotor 25 in the series elastic driver rotates according to a control signal and is output to a transmission shaft 28 through a motor spindle 26 and a flat key 27. The transmission shaft 28 drives the nut 31 to rotate, so that the ball screw 30 and the joint connecting rod 23 extend and retract. The joint connecting rod 23 extends and retracts to make linear motion, so that the sliding shaft 14 is driven to make linear motion in the sliding sleeve 12, the transmission rod 15 rotates around the node, and the upper arm and the lower arm are pushed to rotate around the central point respectively. When the upper arm and the lower arm are subjected to external impact, the series elastic driver moves integrally through the guide shaft 18 except the spring spacer 20, thereby compressing the die spring 19, and the die spring 19 absorbs the impact of external load fluctuation, thereby realizing the mechanical flexibility of the joint. Because both die springs 19 themselves have a pre-compression, the rate of change of spring force produced is twice that of one spring.

The invention introduces a crank-slider structure at the joint, and the structure realizes the conversion of the movement of the screw rod 30 of the serial elastic driver and the rotation of the joint.

Claims

1. A linear-motion joint flexible mechanical arm based on a series elastic driver is characterized by comprising a joint arm and two series elastic drivers; the joint arm comprises a shoulder arm, an upper arm and a lower arm which are sequentially hinged, a first series elastic driver is installed in the shoulder arm, the output end of the first series elastic driver is connected with the upper arm through a first slider-crank mechanism, a second series elastic driver is installed in the upper arm, and the output end of the second series elastic driver is hinged with the lower arm through a second slider-crank mechanism.

2. The tandem-spring-drive-based linear-motion joint flexible robotic arm of claim 1, wherein the shoulder arm comprises a left shoulder link and a right shoulder link, one end of the left shoulder link and one end of the right shoulder link being connected together.

3. The linear motion joint flexible mechanical arm based on the series elastic driver as claimed in claim 1, wherein the upper arm comprises a left upper arm and a right upper arm, and the left upper arm and the right upper arm are connected through a fixing member.

4. The tandem elastic drive-based linear motion joint flexible robotic arm of claim 1, wherein said lower arm is fork-shaped.

5. The linear motion joint flexible mechanical arm based on the series elastic driver as claimed in claim 1, wherein the first slider-crank mechanism is connected with the upper arm through a fixing member, and the fixing member is connected with the upper arm and hinged with the output end of the first slider-crank mechanism.

6. The linear motion joint flexible mechanical arm based on the series elastic driver as claimed in claim 1, wherein the slider-crank mechanism comprises a slide shaft, a transmission rod and a slide sleeve, two ends of the slide shaft are respectively connected with the output end of the series elastic driver and the transmission rod, the slide shaft is sleeved in the slide sleeve, and the slide sleeve is fixedly connected to the shoulder arm or the upper arm.

7. The linear motion joint flexible mechanical arm based on the serial elastic driver as claimed in claim 1, wherein the serial elastic driver comprises a driving motor, a spring spacer, a die spring, a housing, a transmission shaft, a ball screw and a joint connecting rod; a guide shaft is connected between the driving motor and the shell, a spring spacing piece is sleeved on the guide shaft, and die springs are arranged between the spring spacing piece and the driving motor and between the spring spacing piece and the shell; a transmission shaft is arranged in the shell and connected with a main shaft of the motor; the transmission shaft is fixedly connected with a nut, the ball screw is sleeved in an inner hole of the transmission shaft and connected with the nut, and the joint connecting rod is connected with the ball screw.

8. The linear motion joint flexible mechanical arm based on the series elastic driver as claimed in claim 7, wherein the driving motor comprises a motor box body, a motor rotor, a motor stator and a motor spindle, the motor stator and the motor rotor are both arranged in the motor box body, and the motor rotor is fixed on the motor spindle.

9. The linear motion joint flexible mechanical arm based on the series elastic driver as claimed in claim 7, wherein a Hall sensor is arranged in the motor stator.