A control method of a pneumatic soft robotic arm

Abstract

The application discloses a control method of a pneumatic soft-bodied mechanical arm. First, an image is collected through a visual sensor, a pose sensor senses a current position of a center of an end of the mechanical arm, a target detection algorithm is used to extract position coordinates of an object to be grabbed, and a target position of the center of the end of the mechanical arm is obtained through coordinate conversion. Then, the internal pressure of each soft-bodied driver of each soft-bodied mechanical arm unit when the center of the end of the mechanical arm reaches the target position is calculated. Finally, a PID controller is designed, the charging / discharging amount of each soft-bodied driver is obtained through the PID controller, the charging / discharging control of the soft-bodied driver is performed through an electrical proportional valve, the soft-bodied mechanical arm is driven to move, and the center of the end of the mechanical arm reaches the target position. The method is combined with the object to be grabbed, and precise control of the soft-bodied mechanical arm is realized.

Description

Technical Field

[0001] This invention belongs to the field of robot control technology, specifically a control method for a pneumatic soft robotic arm. Background Technology

[0002] Traditional rigid robotic arms offer advantages such as high response speed, high precision, and ease of control, making them widely applicable in modern industrial production lines. However, rigid robotic arms have limited environmental adaptability, low degrees of freedom, and are restricted in working in confined spaces. They also pose significant safety hazards, particularly in human-robot interaction, as they can easily damage grasped objects or surgical subjects, limiting their application in many specific environments. Soft robotic arms, on the other hand, offer advantages such as good compliance, high adaptability, light weight, and high degrees of freedom. They can also absorb external forces and impacts, minimizing damage to interacting objects, and are widely used in fields such as military reconnaissance, medical rehabilitation, and automated production lines.

[0003] Currently, research on control methods for soft robotic arms is still immature. The control of soft robotic arms generally adopts open-loop control, which has relatively low control accuracy and is not combined with the target to be grasped. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is to propose a control method for a pneumatic soft robotic arm.

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

[0006] A control method for a pneumatic soft robotic arm, wherein the pneumatic soft robotic arm is composed of several soft robotic arm units connected in series, each soft robotic arm unit includes a connecting plate and a soft actuator, three soft actuators are evenly distributed circumferentially and connected to the connecting plate at both ends, and each soft actuator is connected to an air pump through an air pipe and an electro-proportional valve; the method is characterized by the following steps:

[0007] Step 1: Collect images and perceive the current position of the center of the soft robotic arm end via the vision sensor and pose sensor mounted on the end of the soft robotic arm. Use the target detection algorithm to extract the position coordinates of the object to be grasped, and obtain the target position (x, y, z) of the center of the soft robotic arm end through coordinate transformation.

[0008] Step 2: Calculate the internal pressure of each soft actuator in each soft robotic arm unit when the end effector reaches the target position;

[0009] By subtracting the length of the non-deformable part of the soft robotic arm from the target position of the end effector center, and then sequentially piecing together the deformable parts of the soft robotic arm, the position coordinates (u, v, w) of the end effector center of the deformable part of the soft robotic arm are obtained. The transformation relationship from (x, y, z) to (u, v, w) is as follows:

[0010]

[0011] In the formula, d represents the thickness of the connecting disk of the soft robotic arm unit. 12 θ represents the length of the non-deformable portion between two adjacent soft robotic arm units. i This represents the bending angle of the i-th soft robotic arm unit; This represents the deflection angle of the soft robotic arm, where n is the number of soft robotic arm units contained in the soft robotic arm.

[0012] The deflection angle of the soft robotic arm is expressed as:

[0013]

[0014] The formulas for calculating the bending angle of each soft robotic arm unit and the length of the deformable part of the soft robotic arm unit are as follows:

[0015]

[0016]

[0017] In the formula, L i This represents the length of the deformable portion of the i-th soft robotic arm unit;

[0018] Combine equations (1) to (3) to calculate the position coordinates (u,v,w) of the center point of the deformable part of the soft robotic arm, and then substitute them into equation (4) to calculate the length of the deformable part of each soft robotic arm unit.

[0019] The length l of the deformable parts of the three software actuators is calculated using equation (5). i1 l i2 and l i3 :

[0020]

[0021] Where r represents the radius of the circle formed by the center points of the three soft actuators of the soft robotic arm unit;

[0022] Calculate the internal pressure of the software driver according to equation (6):

[0023]

[0024] In the formula, lij p ij Let J represent the length and internal pressure of the j-th soft actuator of the i-th soft robotic arm unit, respectively, where j = 1, 2, 3;

[0025] Step 3: Design a PID controller. The inputs to the PID controller include e1, e2, and e3, and the outputs include Φ1, Φ2, and Φ3. e1 is the internal pressure deviation of the first soft actuator between the current position of the soft robotic arm's end effector center and the target position. e2 is the internal pressure deviation of the second soft actuator between the current position of the soft robotic arm's end effector center and the target position. e3 is the internal pressure deviation of the third soft actuator between the current position of the soft robotic arm's end effector center and the target position. Φ1 is the inflation / deflation amount of the first soft actuator, Φ2 is the inflation / deflation amount of the second soft actuator, and Φ3 is the inflation / deflation amount of the third soft actuator.

[0026] The inflation / deflation volume of each soft actuator is obtained by a PID controller, and then the inflation / deflation of the soft actuator is controlled by an electro-proportional valve to drive the soft robotic arm to move so that the center of the soft robotic arm end reaches the target position.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention utilizes a vision sensor and a pose sensor mounted on the end effector of a soft robotic arm to acquire images and perceive the actual position of the end effector. It extracts the position coordinates of the object to be grasped from the image through target detection, and then obtains the length of the deformable parts of each soft actuator. Based on the relationship between the length of the deformable part of the soft actuator and the internal pressure of the soft actuator, the internal pressure of the soft actuator is obtained. Then, PID control is used to obtain the inflation / deflation amount of the soft actuator, and the soft actuator is inflated / deflated to bring the center of the end effector of the soft robotic arm to the target position, thus achieving precise control of the soft robotic arm. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the pneumatic soft robotic arm of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the soft robotic arm unit of the present invention;

[0031] Figure 3 This is a simplified schematic diagram of the centerline of the soft robotic arm unit of the present invention;

[0032] Figure 4 This is a simplified schematic diagram of the deformable part of the soft robotic arm unit of the present invention;

[0033] In the diagram, 1-connector disk; 2-software driver. Detailed Implementation

[0034] Specific embodiments are given below with reference to the accompanying drawings. These specific embodiments are only used to describe the technical solution of the present invention in detail, and are not intended to limit the scope of protection of this application.

[0035] See Figures 1-2 The pneumatic soft robotic arm is composed of several soft robotic arm units connected in series. Each soft robotic arm unit includes two connecting plates 1 and three soft actuators 2. The three soft actuators 2 are evenly distributed in a circle and their two ends are connected to the corresponding connecting plates 1. Each soft actuator 2 is connected to an air pump through an air pipe and an electric proportional valve. By inflating and deflating the soft actuators 2, the soft actuators 2 are deformed, thereby realizing the extension, bending, and twisting movements of the pneumatic soft robotic arm.

[0036] This invention provides a control method for a pneumatic soft robotic arm (hereinafter referred to as the method, see [link]). Figures 1-4 The process includes the following steps:

[0037] Step 1: Equip the end effector of the soft robotic arm with a vision sensor and a pose sensor. The vision sensor is used to acquire images containing the object to be grasped, and the pose sensor is used to perceive the current position of the center of the end effector. Use a target detection algorithm to extract the position coordinates (r, s, t) of the object to be grasped. Based on the position coordinates (r, s, t) of the object to be grasped, use coordinate transformation to obtain the position that the center of the end effector of the soft robotic arm needs to reach, i.e., the target position of the center of the end effector of the soft robotic arm, denoted as (x, y, z).

[0038] Step 2: Calculate the internal pressure of each soft actuator in each soft robotic arm unit when the end effector reaches the target position;

[0039] Since the connecting disk of the soft robotic arm unit is non-deformable, the position coordinates (u, v, w) of the center of the deformable part of the soft robotic arm can be obtained by subtracting the length of the non-deformable part of the soft robotic arm from the target position of the center of the end of the soft robotic arm, and then sequentially splicing the various deformable parts of the soft robotic arm together. The transformation equation from (x, y, z) to (u, v, w) is then:

[0040]

[0041] In the formula, d represents the thickness of the connecting disk of the soft robotic arm unit. 12 θ represents the length of the non-deformable portion between two adjacent soft robotic arm units. i It represents the central angle corresponding to the center line (the center line is an arc) of the deformable part of the i-th soft robotic arm unit, that is, the bending angle of the soft robotic arm unit; This represents the deflection angle of the soft robotic arm, where n is the number of soft robotic arm units contained in the soft robotic arm.

[0042] The deflection angle of the soft robotic arm is expressed as:

[0043]

[0044] Assuming that the deformation of each soft robotic arm unit is the same, then the bending angle and the length of the deformable part of each soft robotic arm unit are also the same. The calculation formula is as follows:

[0045]

[0046]

[0047] In the formula, L i This represents the length of the deformable portion of the i-th soft robotic arm unit, where the length refers to the arc length.

[0048] Combine equations (1) to (3) to calculate the position coordinates (u,v,w) of the center point of the deformable part of the soft robotic arm, and then substitute them into equation (4) to calculate the length of the deformable part of each soft robotic arm unit.

[0049] Then, based on the length of the deformable part of the soft robotic arm unit, the length l of the deformable part of the three soft actuators is calculated using equation (5). i1 l i2 and l i3 Among them, l i1 l represents the length of the deformable portion of the first soft actuator in the i-th soft robotic arm unit. i2 l represents the length of the deformable portion of the second soft actuator in the i-th soft robotic arm unit. i3 This represents the length of the deformable portion of the third soft actuator in the i-th soft robotic arm unit;

[0050]

[0051] Where r represents the radius of the circle formed by the center points of the three soft actuators of the soft robotic arm unit;

[0052] The internal pressure of the software actuator is calculated according to Equation (6) based on the length of the deformable part of the software actuator.

[0053]

[0054] In the formula, l ij p ij Let J represent the length and internal pressure of the j-th soft actuator of the i-th soft robotic arm unit, respectively, where j = 1, 2, 3;

[0055] The formula for calculating the internal pressure of the soft actuator in equation (6) was obtained by fitting several sets of experimental data; since the deformation of all soft robotic arm units is the same, the internal pressure of the first soft actuator of all soft robotic arm units is equal, the internal pressure of the second soft actuator of all soft robotic arm units is equal, and the internal pressure of the third soft actuator of all soft robotic arm units is equal, i.e., p 11 =p 21 =…=p n1 p 12 =p 22 =…=p n2 p 13 =p 23 =…=p n3 .

[0056] Step 3: Design a PID controller to obtain the inflation / deflation volume of each soft actuator, and then control the inflation / deflation of the soft actuator through an electro-proportional valve to drive the soft robotic arm to move, so that the center of the soft robotic arm end reaches the target position, thereby realizing the control of the soft robotic arm;

[0057] The inputs to the PID controller include e1, e2, and e3, and the outputs include Φ1, Φ2, and Φ3. e1 is the internal pressure deviation of the first soft actuator between the current position of the end effector center and the target position. e2 is the internal pressure deviation of the second soft actuator between the current position of the end effector center and the target position. e3 is the internal pressure deviation of the third soft actuator between the current position of the end effector center and the target position. Φ1 is the inflation / deflation amount of the first soft actuator. Φ2 is the inflation / deflation amount of the second soft actuator. Φ3 is the inflation / deflation amount of the third soft actuator.

[0058] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A control method for a pneumatic soft robotic arm, wherein the pneumatic soft robotic arm is composed of several soft robotic arm units connected in series, each soft robotic arm unit includes a connecting plate and a soft actuator, three soft actuators are evenly distributed in a circle and connected to the connecting plate at both ends, and each soft actuator is connected to an air pump through an air pipe and an electro-proportional valve; characterized in that, The method includes the following steps: Step 1: Acquire images and perceive the current position of the center of the soft robotic arm's end effector using vision and pose sensors mounted on its end effector. Extract the position coordinates of the object to be grasped using a target detection algorithm, and obtain the target position of the center of the soft robotic arm's end effector through coordinate transformation. ; Step 2: Calculate the internal pressure of each soft actuator in each soft robotic arm unit when the end effector reaches the target position; By subtracting the length of the non-deformable portion of the soft robotic arm from the target position of its end effector center, and then sequentially piecing together the deformable portions of the soft robotic arm, the coordinates of the end effector center of the deformable portion of the soft robotic arm can be obtained. ,Depend on arrive The conversion relationship is as follows: ， In the formula, This indicates the thickness of the connecting plate of the soft robotic arm unit. This represents the length of the non-deformable portion between two adjacent soft robotic arm units. Indicates the first The bending angle of each soft robotic arm unit; This indicates the deflection angle of the soft robotic arm. It is the number of soft robotic arm units contained in the soft robotic arm; The deflection angle of the soft robotic arm is expressed as: ， Assuming that the deformation of each soft robotic arm unit is the same, and that the bending angle and the length of the deformable portion of each soft robotic arm unit are also the same, the calculation formula is as follows: ， ， In the formula, Indicates the first The length of the deformable part of each soft robotic arm unit; Calculate the coordinates of the center point of the deformable end of the soft robotic arm by combining formulas (1) to (3). Substitute into equation (4) to calculate the length of the deformable part of each soft robotic arm unit; The lengths of the deformable parts of the three software actuators are calculated using equation (5). , and : ， in, This represents the radius of the circle formed by the center points of the three soft actuators of the soft robotic arm unit. Calculate the internal pressure of the software driver according to equation (6): ， In the formula, , They represent the first The first soft robotic arm unit The length and internal pressure of each software driver, ; Step 3: Design a PID controller. The inputs to the PID controller include... , and Output includes , and ; This represents the internal pressure deviation between the current position of the end effector center of the soft robotic arm and the first soft actuator when it reaches the target position. This represents the internal pressure deviation of the second soft actuator between the current position of the soft robotic arm's end effector center and the position reached when the target position is achieved. The internal pressure deviation of the third soft actuator between the current position of the end effector center of the soft robotic arm and the position when it reaches the target position; The charge / depressurization amount for the first software driver. For the charge / discharge volume of the second software driver, For the charge / discharge volume of the third software driver; The inflation / deflation volume of each soft actuator is obtained by a PID controller, and then the inflation / deflation of the soft actuator is controlled by an electro-proportional valve to drive the soft robotic arm to move so that the center of the soft robotic arm end reaches the target position.

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