CN113305825A

CN113305825A - Single-degree-of-freedom rope-driven variable-stiffness joint and measurement and control platform thereof

Info

Publication number: CN113305825A
Application number: CN202110585975.5A
Authority: CN
Inventors: 肖航; 吕胜男; 丁希仑
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2021-05-27
Filing date: 2021-05-27
Publication date: 2021-08-27
Anticipated expiration: 2041-05-27
Also published as: CN113305825B

Abstract

The invention discloses a single-degree-of-freedom rope-driven variable-stiffness joint and a measurement and control platform thereof. Aiming at a single-degree-of-freedom rotary joint, the joint is controlled to rotate by a left rope and a right rope; a tension measuring device is arranged on the transmission path of the driving rope, so that the tension on the driving rope can be measured in real time; a magnetic induction angle sensor is arranged on the joint rotating axis, so that the joint corner and the joint corner deformation under the external load effect can be monitored. The invention also has a set of measurement and control platform, can monitor the running state of each part in real time, can control the rope driving device and the rope tension, and records the detected data on the upper computer, and is convenient to operate.

Description

Single-degree-of-freedom rope-driven variable-stiffness joint and measurement and control platform thereof

Technical Field

The invention belongs to the technical field of machinery and the field of automatic control, and particularly relates to a single-degree-of-freedom rope-driven variable-stiffness joint and a measurement and control platform thereof.

Background

The single-degree-of-freedom rotary joint is widely applied to various electromechanical devices such as robots, mechanical arms and exoskeleton rehabilitation devices as the most common joint form. Compared with the traditional transmission modes such as gears and connecting rods, the rope drive has the advantages of light weight, flexible and various arrangement modes and wide arrangement range, and can reduce inertia in the movement process of the equipment to a great extent, so that the equipment has lighter mass and faster response speed. In order to make the device more adaptable, it is necessary to adjust the stiffness of the joint according to different task requirements and working environments. Therefore, the design of the single-degree-of-freedom rope-driven variable-stiffness joint and the measurement and control platform thereof is needed.

Disclosure of Invention

Aiming at the problems, the invention provides a single-degree-of-freedom rope-driven variable-stiffness joint and a measurement and control platform thereof, wherein the joint is driven to move by a rope, and the stiffness of the joint can be adjusted; the joint real-time state is monitored through the measurement and control platform, and the joint rigidity change rule can be obtained through measurement.

The single-degree-of-freedom rope-driven variable-stiffness joint comprises two sets of rope driving devices which are arranged in bilateral symmetry, and winding and unwinding control of two driving ropes is achieved respectively. The output ends of the two driving ropes are respectively connected with the left end and the right end of the movable platform which can rotate in the horizontal plane. Any one of the two driving ropes is connected with a variable stiffness mechanism and a rope tension measuring device in series.

And a magnetic induction sensor is arranged above the rotating shaft of the movable platform, and the magnetic induction angle sensor is matched with a magnet arranged at the top of the rotating shaft of the movable platform to monitor the rotating angle of the movable platform. The middle part of the movable platform is connected with a load rope, and the load rope is connected with a load after passing through a pulley on the pulley seat;

aiming at the single-degree-of-freedom rope-driven variable-stiffness joint with the structure, the measurement and control method is realized by the following steps:

make directly connect the rope drive who moves the platform through the driving rope and be rope drive A, another is rope drive B, then has:

step 1: and (5) initializing the upper computer, the data acquisition card and the motion controller when the operation is started.

Step 2: and controlling motors in the two sets of rope driving devices to start to move, and driving the driving ropes to wind and unwind through the winding rollers.

And step 3: measuring whether the movable platform moves to a specified angle or not through a magnetic induction angle sensor, and if so, stopping the motor to move; if not, repeat step 2.

And 4, step 4: and the motor of the rope driving device A stops moving, and the motor of the rope driving device B rotates, so that the driving rope is wound on the winding roller until the tension value of the driving rope measured by the pressure sensor reaches a target set value.

And 5: applied weight of G₁The weight of (2) measures the joint corner deformation delta theta after the weight is applied through a magnetic induction angle sensor; according to weight G₁And the angular deformation delta theta is summed to obtain a tensile value F₁Joint stiffness in time.

Step 6: and (5) changing the set value of the rope tension target, repeating the step (5) and the step (6), and obtaining the relation between the joint stiffness and the rope tension.

The invention has the advantages that:

1. according to the single-degree-of-freedom rope-driven variable-rigidity joint, the variable-rigidity mechanism is added on the driving rope, and the rigidity of the joint can be adjusted by changing the tensile force of the driving rope, so that the requirements of different tasks on the rigidity of the joint are met.

2. The single-degree-of-freedom rope drives the variable-rigidity joint, the rope tension measuring assembly is introduced, the rope tension is converted into the pulley pressure for measurement, the driving rope tension is monitored in real time, and the adjustment of the joint rigidity is guided.

3. The single-degree-of-freedom rope-driven variable-stiffness joint is simple in structure, the sensor is not in direct contact with the rotating shaft, and the influence on joint motion is reduced.

4. The measurement and control method for the single-degree-of-freedom rope-driven variable-stiffness joint can control all actions of the joint and monitor related data, and an upper computer can automatically record detected data, so that the method is simple to operate and convenient in data processing.

Drawings

FIG. 1 is an overall schematic view of a single degree of freedom rope-driven variable stiffness joint of the present invention.

Fig. 2 is a schematic structural diagram of a rope driving device in the variable stiffness joint of the invention.

FIG. 3 is a schematic view of a single degree of freedom rotary joint structure in the variable stiffness joint of the present invention.

FIG. 4 is a schematic structural diagram of a stiffness varying mechanism in the stiffness varying joint according to the present invention.

FIG. 5 is a schematic structural view of a device for measuring the tensile force of a rope in a variable stiffness joint according to the present invention.

FIG. 6 is a schematic structural diagram of a measurement and control system in a variable stiffness joint.

In the figure:

Detailed Description

The invention will be further explained with reference to the drawings.

The invention relates to a single-degree-of-freedom rope-driven variable-stiffness joint, which comprises a rope driving device 1, a single-degree-of-freedom rotating joint 2, a rope tension measuring device 3, a variable-stiffness mechanism 4, an external load applying device 5 and a base 6, and is shown in figure 1.

The rope driving device 1 includes a motor base 101, a motor 102, a coupling 103, a wire roller base a104, a wire roller base B105, a winding roller 106, and a driving rope 107, as shown in fig. 2. Wherein, the motor cabinet 101, the line roller seat A104 and the line roller seat B105 are provided with screw holes, and the matching screws are fixed with the base 6. The winding roller 106 is coaxially and fixedly installed on a rotating shaft, two ends of the rotating shaft are respectively installed in the openings of the wire roller seat A104 and the wire roller seat B105 to form a rotating pair, and a driving rope 107 is wound on the winding roller 106. The motor 102 is fixedly installed on the motor base 101, the output shaft is coaxial with the rotating shaft, and the output shaft is connected with the rotating shaft through the coupler 103. Therefore, the motor 102 rotates, the coupler 103 transmits the rotation of the motor to the winding roller 106, and the winding roller 106 is driven to rotate to drive the driving rope 107 to wind and unwind on the winding roller 106. The rope driving devices 1 having the above-described structure are provided in two sets, and are symmetrically provided on the base 6 in the left-right direction, and the output shafts of the motors 102 are opposite and coaxial.

The single-degree-of-freedom rotary joint 2 comprises a guide seat A201, a guide seat B202, a rotating shaft end cover 203, a rotating shaft support 204, a movable platform 205 and a magnetic induction angle sensor 206, as shown in FIG. 3.

The guide seat a201 and the guide seat B202 are respectively located at the front sides of the winding rollers in the two rope driving devices 1, and are respectively and symmetrically spaced from the two winding rollers 106. Holes are formed in the upper parts of the guide seat A201 and the guide seat B202, and the holes are located right in front of the winding roller 106.

The rotating shaft support 204 is fixedly installed on the base 7 and is located on a perpendicular bisector of a connecting line of the guide seat a201 and the guide seat B202. The upper part of the rotating shaft support 204 is provided with a rotating shaft end cover 203, and the rotating shaft end cover 203 is fixed with the rear side wall of the rotating shaft support through a connecting part at the side. Meanwhile, a shaft hole is formed in the center of the rotating shaft end cover 203, a shaft hole is also formed in the corresponding position of the top surface of the rotating shaft support 204, and two ends of the rotating shaft are respectively matched and spliced with the two shaft holes to form a rotating pair.

The movable platform 205 is a strip-shaped plate structure, a support rod is fixedly mounted at the center position, the support rod is perpendicular to the movable platform, and the tail end opening is fixed with the rotating shaft, so that the movable platform 205 can rotate around the rotating shaft. Holes are symmetrically formed in the left end and the right end of the movable platform 205, so that after the driving ropes 107 in the two rope driving devices 1 respectively penetrate through the holes in the upper parts of the guide seat A201 and the guide seat B202, the output ends of the driving ropes are respectively connected with the holes in the left end and the right end of the movable platform 205, and after the driving ropes are connected, the two driving ropes 107 are guaranteed to be parallel to each other and are parallel to the base 6. Whereby the normal and reverse rotations of the movable platform 205 around the rotation axis are controlled by winding and unwinding the driving cord 107 on the winding roller 106 in the two sets of cord driving apparatuses 1. The magnetic induction angle sensor 206 is erected at the top of the rotating shaft end cover 203 through four upright posts which are uniformly distributed in the circumferential direction, and the magnetic induction angle sensor 206 is matched with a magnet arranged at the top of the rotating shaft to monitor the rotating angle of the movable platform 205.

Any one of the driving ropes 107 in the two sets of rope driving devices 1 is designed into two sections, namely a section A and a section B, wherein the section A is wound on the winding roller 106 and is connected with the variable stiffness mechanism 4 after bypassing the rope tension measuring device 3. One end of the section B is connected with the variable stiffness mechanism 4, and the other end is connected with the movable platform 205.

The variable stiffness mechanism 4 includes an outer frame 401, a disc spring 402 and a tension rod 403, as shown in fig. 4. The outer frame 401 is a rectangular structure, and two opposite ends of the outer frame are respectively provided with a large-diameter hole and a small hole which are coaxial; the large diameter hole is used for installing the pull rod 403; the small hole is used for connecting the section B of the driving rope 107. The tie bar 403 is placed inside the outer frame 401 with its front end passing through the large diameter hole, and the tie bar 403 has its front end perforated radially for connecting the section a of the aforementioned driving rope 107. The belleville springs 402 are sleeved on the pull rods 403, and two ends of the belleville springs are respectively matched and positioned with the outer frame 401 and the limiting shoulders at the tail ends of the pull rods 403. Thus, by controlling winding and unwinding of the driving rope 107 on the winding roller 106, the pull rod 403 slides along the large-diameter hole, and the disc spring 402 is correspondingly extended and shortened, thereby allowing the disc spring 402 to have different rigidities. Thus, the driving rope 107 is wound around and unwound from the winding roller 106, and the tension rod 403 is slid along the large-diameter hole, thereby changing the elastic force of the disc spring 402 to achieve variable stiffness.

The rope tension measuring device 3 includes a pulley seat a301, a pressure sensor 302, a pulley seat B303, a pulley seat C304, a pulley a305, a pulley B306, and a pulley C307, as shown in fig. 5. The pulley seat a301, the pulley seat B302 and the pulley seat C304 are sequentially arranged from front to back. The bottom ends of the pulley seat a301 and the pulley seat C307 are directly and fixedly mounted on the base 6. The bottom of the pulley seat B306 is fixedly arranged at the top of the pressure sensor 302, and the bottom of the pressure sensor 302 is fixedly arranged on the base 6. The pulley A305, the pulley B306 and the pulley C307 are respectively arranged at the tops of the pulley seat A301, the pulley seat B303 and the pulley seat C304 through rotating shafts, the axes are arranged along the left-right direction, the three pulleys are arranged at the same height, the centers of the three pulleys are positioned in the same plane parallel to the base 6, and the distances between the adjacent pulleys are equal. The segment A of the drive rope 107 passes sequentially around the bottom of the pulley C305, the top of the pulley B306 and the bottom of the pulley A307, and the friction between the drive rope 107 and the pulley is reduced by the rotation of the pulley around the rotating shaft. The pressure sensor 302 can monitor the pressure on the pulley B306 according to the geometric relationship between the driving rope 107 and the pulley

The pressure can be converted into the tension of the driving rope 201, that is, the tension on the driving rope 201 can be monitored by the pressure sensor 302. In the above formula, T is the pressure measured by the pressure sensor 302, F is the tension on the driving rope, and α is the included angle between the tension direction on the driving rope 107 and the vertical direction.

The external load applying device 5 includes a load rope 501, a load holder 502, a load pulley 503, and a weight 504, as shown in fig. 1. The load seat 502 is fixedly arranged at the edge of the base 6, the load pulley 503 is fixedly arranged on the load seat 502, and one end of the load rope 501 is connected with the middle point of the connecting line of the two sides of the movable platform 205 and the driving rope 107. The other end is connected with a load weight 504 by bypassing a load pulley 503; and when the rotating angle of the movable platform 205 is 0, that is, the movable platform 205 is in the left-right direction, the load rope 501 is parallel to the movable platform 205. Thus, by varying the weight 504, the effect of different loads on the movable platform 205 can be simulated.

The magnetic induction angle sensor 206 and the pressure sensor 302 are combined with an encoder, an upper computer, a motion controller and a data acquisition card to form a measurement and control system, as shown in fig. 6. The data acquisition card receives data measured by the magnetic induction angle sensor 206 and transmits the data to the upper computer, and the upper computer controls the winding and unwinding of the driving rope on the winding roller 106 in the two sets of rope driving devices 1 through the motion controller, so as to control the motion of the movable platform 205. The data acquisition card receives the data measured by the pressure sensor 302 and transmits the data to the upper computer, and when the rope reaches the specified tension, the upper computer combines the rotation angle information measured by the encoder of the motor 102 in the two rope driving devices 1, and the motion of the motor 102 is controlled to stop through the motion controller. .

The measurement and control method for the single-degree-of-freedom rope-driven variable-stiffness joint is realized by the following steps:

let the rope driving device 1 directly connected with the movable platform 205 through the driving rope 107 be a rope driving device a; the other rope drive 1 is a rope drive B, having:

Step 2: the motors 102 in the two sets of rope driving devices 1 are controlled to start moving, and the driving ropes 107 are driven to wind and unwind through the winding rollers 106.

And step 3: measuring whether the movable platform 205 moves to a specified angle or not through the magnetic induction angle sensor 206, and if so, stopping the movement of the motor 102; if not, repeat step 2.

And 4, step 4: the motor 102 of the rope drive a is stopped and the motor 102 of the rope drive B is rotated so that the drive rope 107 is wound on the winding roller 106 until the tension value of the drive rope 107 measured by the pressure sensor 302 reaches the target set value F1.

And 5: applied weight of G₁The weight 504 of (a), the joint rotation angle deformation (the movable platform rotation angle) Δ θ after the weight 504 is applied is measured by the magnetic induction angle sensor 206. According to weight G₁The tensile value F can be obtained by the sum of the angular deformation delta theta₁Joint stiffness in time.

Step 6: changing the target set values of the rope tension to F2, F3 and F4, wherein F2 is 2F1, F3 is 3F1, and F4 is 4F1, and repeating the step 5 and the step 6 to obtain the relation between the single-degree-of-freedom joint stiffness and the rope tension. The operation is ended.

Claims

1. A single degree of freedom rope drive becomes rigidity joint which characterized in that: the winding and unwinding control device comprises two sets of rope driving devices which are arranged in bilateral symmetry and respectively realize the winding and unwinding control of two driving ropes; the output ends of the two driving ropes are respectively connected with the left end and the right end of the movable platform which can rotate in the horizontal plane; a magnetic induction sensor is arranged above the rotating shaft of the movable platform, and the rotating angle of the movable platform is monitored by matching a magnetic induction angle sensor with a magnet arranged at the top of the rotating shaft of the movable platform; the middle part of the movable platform is connected with a load rope, and the load rope is connected with a load after passing through a pulley on the pulley seat; any one of the two driving ropes is connected with a variable stiffness mechanism and a rope tension measuring device in series.

2. The single degree of freedom rope-driven variable stiffness joint of claim 1, wherein: the rope driving device is a winding roller driven by a motor to rotate, and a driving rope is wound on the winding roller.

3. The single degree of freedom rope-driven variable stiffness joint of claim 1, wherein: the two driving ropes respectively penetrate through the guide seats and are connected with the movable platform.

4. The single degree of freedom rope-driven variable stiffness joint of claim 1, wherein: the variable stiffness mechanism comprises an outer frame, a disc spring and a pull rod; the outer frame is of a rectangular structure, and two opposite ends of the outer frame are respectively provided with a large-diameter hole and a small hole which are coaxial; the large-diameter hole is used for installing a pull rod; the small hole is used for connecting a driving rope; the pull rod is arranged in the outer frame, the front end of the pull rod penetrates through the large-diameter hole, and the front end of the pull rod is provided with a hole along the radial direction for connecting the driving rope; the disc spring is sleeved on the pull rod, and two ends of the disc spring are respectively matched and positioned with the outer frame and the limiting shoulder at the tail end of the pull rod; through the control of winding and unreeling of the driving rope on the winding roller, the pull rod slides along the large-diameter hole, the disc spring correspondingly extends and shortens, and then the disc spring has different rigidity.

5. The single degree of freedom rope-driven variable stiffness joint of claim 1, wherein: the rope tension measuring device comprises a pulley seat A, a pressure sensor, a pulley seat B, a pulley seat C, a pulley A, a pulley B and a pulley C; wherein, the bottom ends of the pulley seat A and the pulley seat C are directly and fixedly arranged on the base; the bottom of the pulley seat B is fixedly arranged at the top of the pressure sensor, and the bottom of the pressure sensor is fixedly arranged on the base 6; the pulley A, the pulley B and the pulley C are respectively arranged on the tops of the pulley seat A, the pulley seat B and the pulley seat C through rotating shafts; the driving rope sequentially rounds the bottom of the pulley C, the top of the pulley B and the bottom of the pulley A; the pressure sensor monitors the tension on the drive rope.

6. The single degree of freedom rope-driven variable stiffness joint of claim 1, wherein: the magnetic induction angle sensor, the pressure sensor, the encoder, the upper computer, the motion controller and the data acquisition card form a measurement and control system; the data acquisition card receives data measured by the magnetic induction angle sensor and transmits the data to the upper computer, and the upper computer controls the winding and unwinding of the driving rope on the winding roller in the two rope driving devices through the motion controller, so that the motion of the movable platform is controlled; the data acquisition card receives the data measured by the pressure sensor and transmits the data to the upper computer, and when the rope reaches the specified tension, the upper computer controls the motor to stop moving through the motion controller;

the measurement and control method of the single-degree-of-freedom rope-driven variable-stiffness joint as claimed in claim 1, characterized in that: the method is realized by the following steps:

step 1: initializing an upper computer, a data acquisition card and a motion controller when the operation is started;

step 2: controlling motors in the two sets of rope driving devices to start to move, and driving the driving ropes to wind and unwind through the winding rollers;

and step 3: measuring whether the movable platform moves to a specified angle or not through a magnetic induction angle sensor, and if so, stopping the motor to move; if not, repeating the step 2;

and 4, step 4: the motor of the rope driving device A stops moving, and the motor of the rope driving device B rotates, so that the driving rope is wound on the winding roller until the tension value of the driving rope measured by the pressure sensor reaches a target set value;

and 5: applied weight of G₁The weight of (2) measures the joint corner deformation delta theta after the weight is applied through a magnetic induction angle sensor; according to weight G₁And the angular deformation delta theta is summed to obtain a tensile value F₁Joint stiffness in time;