Multi-degree-of-freedom pneumatic flexible touch gripper and self-adaptive rigidity control method thereof

Abstract

The invention discloses a multi-degree-of-freedom pneumatic flexible touch gripper and a self-adaptive rigidity control method thereof, and relates to the technical field of robot gripping and soft robot, the flexible touch gripper comprises a palm base and at least three multi-cavity finger bodies fixed on the palm base; the multi-cavity finger body comprises three longitudinal air cavities which are distributed in parallel; an electric control module, a multi-way electromagnetic valve and a micro air compression pump are arranged in the palm part base, the micro air compression pump is connected with the longitudinal air cavity through the electromagnetic valve by utilizing a pipeline, and the electric control module is electrically connected with the electromagnetic valve and the micro air compression pump respectively; and one electromagnetic valve is connected with one longitudinal air cavity. Bending, radial shrinkage and integral rigidity adjustability can be realized on the same structure, and a quick response control algorithm is supplemented, so that the requirements of the service robot in multi-scene and multi-material grabbing are met.

Description

Technical Field

[0001] This invention relates to the field of robot grasping and soft robot technology, and more specifically to a multi-degree-of-freedom pneumatic soft-touch gripper and its adaptive stiffness control method. Background Technology

[0002] With the popularization of service robots in home care, warehouse sorting, agricultural product harvesting and hazardous environment operation, the shape, weight and surface characteristics of the objects grasped by robots are highly diversified. Although traditional rigid two- or three-finger grippers have high load capacity, they often damage fragile objects (such as fruits, glassware and flexible packaging) and lack sufficient tolerance for irregularly shaped objects. In order to improve compliance, soft grippers based on silicone rubber or fiber weaving have emerged in recent years. However, the existing technology still has the following significant shortcomings: (1) The stiffness is not adjustable or the adjustment range is limited; most soft grippers rely on the inflation and expansion of a single cavity to achieve bending. Although they can conform to the object, they cannot change the overall stiffness in real time during the grasping process, resulting in insufficient gripping stability when grasping heavy objects. (2) The control accuracy and response speed are limited; pneumatic drive is affected by the compressibility of air. Without precise pressure-displacement-force closed-loop control, it is difficult to achieve rapid adjustment during the grasping dynamic process, especially when a "soft first, hard later" action sequence is required. (3) Insufficient sensing and feedback; existing soft-touch grippers often lack high-resolution pressure, deformation and air cavity status monitoring, making it difficult to achieve unified force control and position control.

[0003] Therefore, how to provide a gripper that satisfies both stiffness adjustment and rapid, precise control is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a multi-degree-of-freedom pneumatic soft-touch gripper and its adaptive stiffness control method to overcome or at least partially solve the above problems. The soft-touch gripper can achieve bending, radial contraction and overall stiffness adjustment on the same structure, and is supplemented by a fast-response control algorithm to meet the needs of service robots in grasping multiple scenarios and materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a multi-degree-of-freedom pneumatic soft-touch gripper, including a palm base and at least three multi-cavity fingers fixed on the palm base; the multi-cavity fingers include three longitudinal air cavities distributed radially and vertically; the palm base is provided with an electronic control module, a multi-way solenoid valve and a micro air pump, the micro air pump is connected to the longitudinal air cavities via pipelines through the solenoid valves, and the electronic control module is electrically connected to the solenoid valves and the micro air pump respectively; one solenoid valve is connected to one longitudinal air cavity.

[0007] Preferably, the longitudinal air chambers are divided into bending drive chambers and stiffness adjustment chambers; two bending drive chambers are distributed on both sides of the multi-cavity finger body, and the stiffness adjustment chamber is distributed in the middle of the multi-cavity finger body. The bending angle of the multi-cavity finger body is adjusted by the bending drive chambers, and the stiffness of the multi-cavity finger body is adjusted by the stiffness adjustment chambers, thereby adjusting the gripping force during grasping. Each multi-cavity finger body has three longitudinal air chambers vertically distributed along the thickness direction of the palm base. By controlling the different inflation states of the bending drive chambers on both sides, the multi-cavity finger body is controlled to bend inward toward the palm base to form a grasping posture.

[0008] Preferably, the outer wall of the multi-cavity finger body is made of double-layer silicone rubber sandwiched with reinforcing fiber woven mesh, which ensures high ductility and limits excessive radial expansion.

[0009] Preferably, a pressure sensor is arranged within the longitudinal air cavity, and flexible strain gauges are attached to the outer wall of the fingertip of the multi-cavity finger. The pressure sensor monitors the air cavity pressure in real time, and the electronic control module adjusts and controls the miniature air pump or solenoid valve according to the air cavity pressure; the flexible strain gauge is used to collect the strain, which is transmitted to the electronic control module for estimating the bending angle and contact force of the multi-cavity finger, thereby achieving collision safety control.

[0010] Preferably, the longitudinal air chamber runs through the entire multi-cavity finger body, and the root of the multi-cavity finger body is provided with a quick-plug air circuit interface and an electrical interface; one end of the air circuit interface is connected to the longitudinal air chamber, and the other end is connected to the solenoid valve through a pipeline; the electrical interface is connected to the pressure sensor, the flexible strain gauge and the electronic control module.

[0011] Preferably, the palm base is also equipped with a pressure sensor and a six-axis torque sensor, which are electrically connected to the electronic control module. The pressure sensor collects the pressure acting on the palm base and transmits it to the electronic control module to simulate human wrist force adjustment; the six-axis torque sensor collects force vectors and torque vectors and transmits them to the electronic control module for overall force control of the gripping action.

[0012] Preferably, the palm base is also provided with a finger mounting seat for matching and installing multi-cavity fingers.

[0013] Preferably, the palm base adopts a lightweight aluminum alloy frame, and the internal electrical connection is achieved through flexible FPC wiring, which is lightweight and reduces the interference of external cables on the movement of the multi-cavity fingers.

[0014] Secondly, embodiments of the present invention provide an adaptive stiffness control method for a multi-degree-of-freedom pneumatic flexible gripper, comprising the following steps:

[0015] Step 1: Open the solenoid valve connecting the two longitudinal air chambers in the multi-chamber finger body via the electronic control module;

[0016] Step 2: Start the micro air pump through the electronic control module to slowly inflate the longitudinal air chambers on both sides, so that the multi-chamber finger body can flexibly bend and fit the surface of the target object to achieve initial coverage;

[0017] Step 3: Open the solenoid valve connecting the middle longitudinal air chamber in the multi-chamber finger body via the electronic control module;

[0018] Step 4: Slowly inflate the longitudinal air chamber in the middle of the multi-cavity finger body to adjust the grip stiffness, enhance the overall stiffness, and achieve continuous adjustment between soft and hard states.

[0019] Preferably, the following steps are also included:

[0020] Collect the weight and surface material properties of the target object to determine the target gripping force. ;

[0021] The air chamber pressure in the bending drive chamber and the strain at the fingertip are collected, and the bending angle of the multi-chamber finger is calculated based on the strain. Contact force F; the air chamber pressure of the bending drive chamber includes the left air chamber pressure P. L and the right air chamber pressure P R ;

[0022] The pressure P in the intermediate air chamber of the stiffness adjustment cavity is collected. C Calculate the pressure P in the intermediate air chamber. C With the pressure P in the left air chamber L Right side air chamber pressure P R The pressure difference is used to adjust the bending angle of the multi-cavity finger body through two sets of pressure differences. ;

[0023] Calculate target grasping force The force error is obtained by measuring the difference between the contact force F and the force error. Based on the force error, the PI control algorithm is used to adjust the state of the solenoid valve and the micro air pump. The opening degree of the solenoid valve and the pump speed of the micro air pump are adjusted. The pressure of the three air chambers is finely adjusted based on the force error.

[0024] The target object is moved, and the air pressure in the bending drive cavity and the strain at the fingertip are continuously collected. The bending angle of the multi-cavity finger is then calculated based on the strain. And the contact force F, based on a model predictive control (MPC) strategy, during the object's motion, according to the current bending angle. The required angle and stiffness changes for the contact force F are predicted, and the pressure of the three air chambers is adjusted in advance based on the angle and stiffness changes.

[0025] The target object is moved to the target position, and exhaust is simultaneously applied to all longitudinal air chambers to place the target object.

[0026] Preferably, when the strain measured by the flexible strain gauge increases significantly in a short period of time, it indicates that a sudden or increased pulse force has been detected, and it is determined that the multi-cavity body has been impacted. At this time, the electronic control module controls all longitudinal air chambers to exhaust air and release pressure instantaneously to avoid causing injury to personnel.

[0027] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0028] This invention provides a multi-degree-of-freedom pneumatic soft-touch gripper and its adaptive stiffness control method. The soft-touch gripper is constructed by multiple multi-cavity fingers to achieve bending drive, radial contraction and overall stiffness adjustment, enabling the soft-touch gripper to move in multiple degrees of freedom. Combined with pressure sensors and strain gauges, the stiffness and clamping force during the gripping process are adaptively adjusted to adapt to the material of the target object at the millisecond level.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a multi-degree-of-freedom pneumatic soft gripper and its adaptive stiffness control method, belonging to the technical fields of service robots, industrial collaborative robots, and special operation robots. It solves the technical problems of fixed stiffness, low control accuracy, and lack of real-time feedback in existing soft grippers, and has the following beneficial effects:

[0030] (1) Provides modular interfaces to facilitate integration into various mobile or industrial robot platforms.

[0031] (2) Wide adaptability, capable of stably gripping objects of different weights and materials;

[0032] (3) High-precision force control, closed-loop control keeps the gripping force error within ±0.2N;

[0033] (4) Dynamic stiffness adjustment, which can complete the transition from soft state to hard state within 0.2 seconds;

[0034] (5) Modular components: Each finger can be replaced and expanded independently, making maintenance convenient;

[0035] (6) Safety: In an environment where people work together, even if there is an accidental collision, it can instantly depressurize and return to a soft state. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1This is a flowchart of an adaptive stiffness control method for a multi-degree-of-freedom pneumatic flexible gripper provided in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention discloses a multi-degree-of-freedom pneumatic soft-touch gripper, including a palm base and at least three multi-cavity fingers fixed on the palm base; the multi-cavity fingers include three longitudinal air cavities distributed radially and vertically; the palm base is provided with an electronic control module, a multi-way solenoid valve and a micro air pump, the micro air pump is connected to the longitudinal air cavities through pipelines via solenoid valves, and the electronic control module is electrically connected to the solenoid valves and the micro air pump respectively; one solenoid valve is connected to one longitudinal air cavity.

[0040] Furthermore, the longitudinal air chamber is divided into a bending drive chamber and a stiffness adjustment chamber; two bending drive chambers are distributed on both sides of the multi-cavity finger body, and the stiffness adjustment chamber is distributed in the middle of the multi-cavity finger body. The bending angle of the multi-cavity finger body is adjusted by the bending drive chamber, and the stiffness of the multi-cavity finger body is adjusted by the stiffness adjustment chamber, thereby adjusting the gripping force during grasping.

[0041] Furthermore, the outer wall of the multi-cavity finger body is made of double-layer silicone rubber sandwiched with reinforcing fiber woven mesh, which ensures high ductility while limiting excessive radial expansion.

[0042] Furthermore, a pressure sensor is arranged within the longitudinal air cavity, and flexible strain gauges are attached to the outer wall of the fingertip of the multi-cavity finger. The pressure sensor can be a MEMS pressure sensor with a range of 0-100 kPa and an accuracy of ±0.5 kPa. The pressure sensor monitors the air cavity pressure in real time, and the electronic control module adjusts and controls the miniature air pump or solenoid valve according to the air cavity pressure. The flexible strain gauge is used to collect the strain, which is transmitted to the electronic control module for estimating the bending angle and contact force of the multi-cavity finger, thus enabling collision safety control.

[0043] Furthermore, the longitudinal air chamber runs through the entire multi-cavity finger body, and the root of the multi-cavity finger body is provided with a quick-plug air circuit interface and an electrical interface; one end of the air circuit interface is connected to the longitudinal air chamber, and the other end is connected to the solenoid valve through a pipeline; the electrical interface is connected to the pressure sensor, flexible strain gauge and electronic control module.

[0044] Furthermore, a pressure sensor and a six-axis torque sensor are also installed on the palm base, which are electrically connected to the electronic control module. The pressure sensor collects the pressure acting on the palm base and transmits it to the electronic control module to simulate human wrist force adjustment; the six-axis torque sensor collects force vectors and torque vectors and transmits them to the electronic control module for overall force control of the gripping action.

[0045] Furthermore, a finger mounting base is provided on the palm base to match and install multi-cavity fingers.

[0046] Furthermore, the palm base adopts a lightweight aluminum alloy frame, and the internal electrical connection is achieved through flexible FPC wiring, which is lightweight and reduces the interference of external cables on the movement of the multi-cavity fingers.

[0047] Furthermore, the miniature air pump provides adjustable pressure from 0 to 120 kPa.

[0048] Furthermore, the electronic control module uses an STM32H7 chip, with a cycle time of 1ms when executing the adaptive stiffness control method. It integrates 24 high-speed ADCs, I²C bus, MEMS pressure sensing interface, and RS485 / ROS2 communication module. It also provides ROS2 driver package or EtherCAT bus integration with robot platform, supports real-time data interaction and control command issuance, and is suitable for industrial collaborative and service robot scenarios.

[0049] On the other hand, an adaptive stiffness control method for a multi-degree-of-freedom pneumatic soft-touch gripper, such as Figure 1 As shown, it includes the following steps:

[0050] S1: The solenoid valve connecting the two longitudinal air chambers in the multi-chamber finger body is opened via the electronic control module;

[0051] S2: The micro air pump is started by the electronic control module to slowly inflate the longitudinal air chambers on both sides, so that the multi-chamber finger body can be flexibly bent and fit the surface of the target object to achieve initial coverage;

[0052] S3: The solenoid valve connecting the middle longitudinal air chamber in the multi-cavity finger body is opened via the electronic control module;

[0053] S4: Slowly inflate the longitudinal air chamber in the middle of the multi-cavity finger body to adjust the grip stiffness, enhance the overall stiffness, and achieve continuous adjustment between soft and hard states.

[0054] On the other hand, an adaptive stiffness control method for a multi-degree-of-freedom pneumatic flexible gripper includes the following steps:

[0055] S1: Collect the weight and surface material properties of the target object to determine the target gripping force. ;

[0056] S2: The solenoid valve connected to the bending drive cavity is opened by the electronic control module, and the micro air pump is started to slowly inflate the bending drive cavity, so that the multi-cavity finger body can be flexibly bent and fit the surface of the target object to achieve initial coverage.

[0057] S3: The pressure in the air chamber of the bending drive cavity is collected by a pressure sensor, the strain at the fingertip is collected by a flexible strain gauge, and the bending angle of the multi-cavity finger is calculated based on the strain. Contact force F; the air chamber pressure of the bending drive chamber includes the left air chamber pressure P. L and the right air chamber pressure P R ;

[0058] S4: The solenoid valve connected to the stiffness adjustment chamber is opened via the electronic control module, slowly inflating the stiffness adjustment chamber to enhance the overall stiffness and achieve continuous adjustment between soft and hard states. Simultaneously, the pressure P in the intermediate air chamber of the stiffness adjustment chamber is collected by a pressure sensor. C Calculate the pressure P in the intermediate air chamber. C With the pressure P in the left air chamber L Right side air chamber pressure P R The pressure difference is used to adjust the bending angle of the multi-cavity finger body through two sets of pressure differences. ;

[0059] S5: Calculate target gripping force The force error is obtained by measuring the difference between the contact force F and the force error. Based on the force error, the PI control algorithm is used to adjust the state of the solenoid valve and the micro air pump. The opening degree of the solenoid valve and the pump speed of the micro air pump are adjusted. The pressure of the three air chambers is finely adjusted based on the force error.

[0060] S6: Move the target object, continuously collect the air chamber pressure of the bending drive cavity and the strain of the fingertip, and calculate the bending angle of the multi-cavity finger body based on the strain. And the contact force F, based on a model predictive control (MPC) strategy, during the object's motion, according to the current bending angle. The required angle and stiffness changes for the contact force F are predicted, and the pressure of the three air chambers is adjusted in advance based on the angle and stiffness changes.

[0061] S7: The target object moves to the target position, exhausts air synchronously in all longitudinal air chambers, and places the target object.

[0062] Furthermore, when the strain measured by the flexible strain gauge increases significantly in a short period of time, it indicates that a sudden or increased pulse force has been detected, indicating that the multi-cavity body has been impacted. At this time, the electronic control module controls all longitudinal air chambers to exhaust air, instantly depressurize, and avoid causing personal injury.

[0063] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0064] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-degree-of-freedom pneumatic soft gripper, characterized in that, The application relates to a multi-freedom-degree pneumatic soft-touch gripper, which comprises the following steps: The application relates to a multi-freedom-degree pneumatic soft-touch gripper, which comprises the following steps:

2. A multi-degree-of-freedom pneumatic soft gripper according to claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

3. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

4. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

5. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

6. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

7. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

8. The multi-degree-of-freedom pneumatic soft gripper of claim 1, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

9. A method for adaptive stiffness control of a multi-degree-of-freedom pneumatic soft gripper, characterized in that, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body. The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body. The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body. The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body. The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body.

10. A method of adaptive stiffness control for a multi-degree-of-freedom pneumatic soft gripper as claimed in claim 9, wherein, The longitudinal air cavity is divided into a bending driving cavity and a rigidity adjusting cavity; two bending driving cavities are distributed on the two sides of the multi-cavity finger body, and the rigidity adjusting cavity is distributed in the middle of the multi-cavity finger body. Collecting weight and surface material properties of a target object, determining target grasping force ; The air cavity pressure of the two longitudinal air cavities and the strain of the fingertips are collected, and the bending angle of the multi-cavity finger body is calculated according to the strain and a contact force F; the air cavity pressure comprises a left air cavity pressure PL and a right air cavity pressure PR; The middle longitudinal air cavity pressure PC in the middle air cavity is taken, the pressure difference between the middle air cavity pressure PC and the left air cavity pressure PL and the right air cavity pressure PR is calculated, and the bending angle of the multi-cavity finger body is adjusted through the two groups of pressure differences ; Computing target gripping force The difference between the contact force F and the target gripping force F0 obtains a force error, and a PI control algorithm is adopted to adjust the states of the electromagnetic valve and the micro air pressure pump according to the force error. 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