CN108927797A - One kind is coupled hardness with softness mechanical arm - Google Patents

Abstract

The invention discloses a mechanical arm with both rigidity and flexibility. The appearance is a cylindrical body. The main material is an elastic body. The inner layer is a coaxial structure with inner and outer layers. A plurality of axial pipes are evenly distributed in the outer layer of the outer layer, and the inner layer is placed to change the mechanical arm. The shape of the rope; the middle layer is circularly distributed with multiple axial pipes, and heaters and thermistors are placed inside; there is a closed chamber in the center of the mechanical arm, which is filled with low melting point alloys, and the middle layer is as close to the closed chamber as possible. Calculate and analyze the space position and deformation that each section of the robotic arm needs to achieve during work, control the heating wire to heat the low-temperature alloy to its melting point to make it into a liquid state, and control the expansion and contraction of each rope to make the section of the robotic arm reach the preset space position and deformation, stop the heating wire to solidify the liquid cryogenic alloy located in this section. The rigid and flexible mechanical arm of the present invention can change the rigidity of the mechanical arm at an appropriate time during the deformation process, and quickly complete the mutual conversion of the characteristics of the rigid mechanical arm and the flexible mechanical arm.

Description

A rigid and flexible mechanical arm

technical field

The invention relates to the field of soft robots, in particular to a rigidity variable mechanical arm.

Background technique

The robotic arm is an automatic device that can imitate the movement of the human arm, and is used to grab and carry workpieces or operate tools according to a fixed program. Because it can replace people to perform a series of tedious and repetitive labor, and can also replace people to complete some high-risk work, it is widely used in machinery manufacturing and other industries.

In the development process of the robotic arm, the initial stage is a rigid structure, and its end positioning is relatively accurate, which can give full play to its advantages in high-precision machining. However, its complex structure is relatively large and its degrees of freedom are limited, making it difficult to operate in a small operating space or in a complex environment. flexible operation. In addition, each connecting rod of the rigid robotic arm is connected by a hinge, and the hinge structure will have a certain margin. When the load weight at the end changes suddenly or is subjected to a huge external force, it will cause positioning errors and vibrations at the end of the mechanical arm. Each hinge produces a certain positioning error, and the error and vibration of each hinge will accumulate at the end of the manipulator, making it difficult to control the positioning accuracy of the end of the manipulator.

In order to use manipulators in complex environments with limited operating space, flexible manipulators with infinite degrees of freedom have emerged. The flexible manipulator is a strongly coupled, nonlinear time-varying structure, but at the same time, it is difficult to precisely control the positioning accuracy of the end of the flexible manipulator due to its excessive freedom.

At present, researchers have explored this and come up with some solutions: Patent CN101011825A proposes an invention to improve the motion accuracy of the end of the mechanical arm: a safe variable stiffness mechanical joint. This invention can solve the problem of low precision of the end to a certain extent, but the method of performing stiffness transformation by controlling the power on and off of the electromagnet is prone to control delay, and it is difficult to quickly execute the switching command of the control system. Patent CN103273502A proposes a flexible manipulator shock absorbing device and method based on controllable stiffness and controllable damping. Both the stiffness of the elastic body and the damping of the damper in the magnetorheological damping device can be controlled by changing the excitation current, so as to meet the internal resonance requirements between the manipulator and the magnetorheological damping device in the system, and consume vibration energy through the damper . However, the shear stiffness of magnetorheological elastomers has a hysteresis to the change of the applied magnetic field strength, and the use of magnetorheological elastomers is time-sensitive, and must be replaced after a period of use.

Contents of the invention

In order to solve the problem that the hinge mechanism between the existing rigid manipulator links leads to low positioning accuracy at the end of the working state, while the flexible manipulator has too much freedom and is difficult to control due to coupling motion, a new method for deforming the manipulator is proposed. The process body can change the stiffness at an appropriate time to quickly complete the mutual conversion between the rigid manipulator and the flexible manipulator. Through this method, the respective advantages of the two can be combined while avoiding the problem of poor positioning accuracy when the manipulator is working.

The rigid and flexible mechanical arm of the present invention is a cylindrical whole in a non-working state, and there is no connecting rod and hinge mechanism of the rigid mechanical arm. The main material of the manipulator is made of elastic body, such as the same silicone material as most flexible manipulators. The interior is a coaxial structure of the inner and outer layers. A plurality of axial pipes are evenly distributed in the outer layer of the manipulator, and the ropes that change the shape of the manipulator are placed inside; A plurality of axial pipes are evenly distributed in the middle layer, and heaters and thermistors are placed inside; there is a closed chamber in the center of the mechanical arm, which is filled with low melting point alloys, and the middle layer is as close to the closed chamber as possible.

The technical content of the rigid and flexible mechanical arm of the present invention is as follows: the external cylindrical structure of the mechanical arm, and the coaxial structure of the internal and external layers. The central chamber is filled with low-melting point alloys, and multiple segments of electric heating wires of the same specification located in the middle layer can heat the gallium-indium alloy in sections. The temperature outside the alloy is monitored in real time, and the linkage control of the uniformly distributed ropes on the outer layer can realize the precise change of the shape of the mechanical arm. The principle of rigidity change and deformation of the mechanical arm is that the electric heating wire changes the gallium-indium alloy located in the heated section from solid to liquid under the control of the thermistor. At this time, it can be deformed under the action of multiple ropes' linkage pulling or loosening. . The deformation sequence of the manipulator starts from the fixed end to the end of the manipulator and heats the molten metal step by step. After the rope is linked to control the deformation amount, the heating is stopped to fix the deformation angle. Finally, all parts of the manipulator have set the deformation angle, and the manipulator is one. The fixed rigid body can effectively reduce the positioning error of the end. Therefore, the Rigid-Flexible Robotic Arm only has a heated part and an unheated part, that is, it distinguishes the rigid segment and the flexible segment of the robotic arm, avoiding the use of the rod and hinge structure of the traditional robotic arm, and thus effectively The movement error of the end is controlled, so that the mechanical arm of the present invention can complete high-precision operation actions. The length of each segment of the robotic arm is determined by the length of each electric heating wire, so in theory, if the length of each segment of the electric heating wire used is smaller, the rigid-flexible robot is divided into more segments, and the robot control accuracy is higher.

The present invention utilizes a low-melting-point alloy: gallium-indium alloy. Gallium-indium alloy has a low melting point, and its phase transition can occur at tens of degrees Celsius. The phase transition temperature range is as narrow as only 2 degrees Celsius. Therefore, gallium-indium alloy can be quickly solidified from a liquid state without active cooling. Solid gallium indium alloy exhibits strong rigidity, so it helps to avoid deformation and vibration when the end of the robotic arm is loaded or impacted. On the contrary, the liquid gallium-indium alloy can flow freely in the central pipeline of the manipulator, with almost no rigidity, which is convenient for the manipulator to change its shape by pulling it with a rope. In order to achieve rapid cooling, multiple cooling medium channels spaced apart from the axial pipes where the heater and thermistor are placed can be evenly distributed in the middle layer. Curing, improve the curing speed of the robotic arm, and also ensure the rigidity of the robotic arm.

The rigid and flexible mechanical arm of the present invention adopts silica gel as the main material of the mechanical arm. The silica gel material has strong flexibility, which can not only complete bending at any position, but also withstand a certain torque; at the same time, the silica gel material has poor thermal conductivity and relatively slow heat transfer. , which helps to determine the rigid-flexible boundary position of the manipulator. The use of silica gel as the base material of the manipulator can reduce the damage to the manipulator due to collisions and impacts that may occur during the work of the manipulator.

The actual working method of a rigid and flexible mechanical arm of the present invention is as follows: the gallium-indium alloy fills the central cavity of the mechanical arm; The spatial position and deformation required to be achieved by each segment of the manipulator are obtained through analysis. Afterwards, the heating wire and thermistor in the first section of the fixed end start working to heat the gallium-indium alloy located in this section, and control the heating wire to heat the gallium-indium alloy to its melting point to make it into a liquid state. At this time, the section The mechanical arm is flexible, and the telescopic action of each rope is controlled by linkage so that the section of the robotic arm reaches the preset spatial position and deformation. At this time, the heating wire of this section is stopped to solidify the liquid gallium-indium alloy in this section. Arm movement is complete and can remain immobilized continuously. After that, the above steps are carried out step by step from the fixed end to the end, and finally the overall spatial shape of the manipulator can match the set shape, and the deformation process of the manipulator is completed.

The rigid and flexible mechanical arm of the present invention can change the rigidity of the mechanical arm at an appropriate time during the deformation process, and quickly complete the mutual conversion of the characteristics of the rigid mechanical arm and the flexible mechanical arm. The present invention can combine the respective advantages of the rigid and flexible mechanical arms while avoiding the existing problems of the current mechanical arms, and further proposes a solution that can control the mechanical arms with high precision.

Description of drawings

Fig. 1 is a two-dimensional full sectional view of a rigid-flexible mechanical arm of the present invention;

Fig. 2 is a side view of a rigid-flexible mechanical arm of the present invention;

In the figure: 1—the main body of the mechanical arm; 2—electric heating wire; 3—thermistor; 4—alloy with low melting point; 5—rope.

Detailed ways

As shown in FIG. 1 , the structure of a rigid and flexible mechanical arm of the present invention is mainly composed of: a main body of the mechanical arm 1 , an electric heating wire 2 , a thermistor 3 , a low melting point alloy 4 and a rope 5 . The main body 1 of the mechanical arm has an outer cylindrical structure, and an inner inner and outer coaxial structure. The central chamber is filled with low-melting-point alloy 4, and multiple sections of electric heating wire 2 of the same specification that are uniformly distributed in the middle layer can heat the low-melting-point alloy 4 in sections, and multiple thermistors of the same specification are located in the middle layer. The temperature outside the low-melting-point alloy 4 of each section is monitored in real time, and the linkage control of the ropes 5 distributed evenly in the outer layer can realize the precise change of the shape of the main body 1 of the mechanical arm. The principle of rigidity change and deformation of the mechanical arm is that the electric heating wire 2 changes the low melting point alloy 4 located in the heated section from solid to liquid under the control of the thermistor 3. At this time, it can be pulled or loosened by the linkage of multiple ropes 5. deformation under action. The deformation sequence of the manipulator starts from the fixed end to the end of the manipulator by heating and melting the low-melting point alloy 4 step by step, then the rope 5 is linked to control the deformation amount, and then stops heating to fix the deformation angle. Finally, all parts of the manipulator have set the deformation angle, then The mechanical arm is a fixed and rigid whole, which can effectively reduce the positioning error of the end. Therefore, the Rigid-Flexible Robotic Arm only has a heated part and an unheated part, that is, it distinguishes the rigid segment and the flexible segment of the robotic arm, avoiding the use of the rod and hinge structure of the traditional robotic arm, and thus effectively The movement error of the end is controlled, so that the mechanical arm of the present invention can complete high-precision operation actions. The length of each segment of the robotic arm is determined by the length of each electric heating wire 2, so theoretically, if the length of each segment of the electric heating wire 2 used is smaller, the rigid-flexible robot is divided into more segments, and the robot control accuracy is higher. .

The technical method of a kind of rigid and soft mechanical arm of the present invention is as follows: as shown in Figure 2, the low-melting point alloy 4 fills the central cavity of the mechanical arm 1; The state of the surrounding working environment is calculated and analyzed to obtain the spatial position and deformation amount that each segment of the robotic arm needs to achieve. Afterwards, the electric heating wire 2 and the thermistor 3 of the first section of the fixed end start to work, heat the low-melting point alloy 4 located in this section, and control the electric heating wire 2 to heat the low-melting point alloy 4 to its melting point so that it becomes At this time, the section of the mechanical arm is flexible, and the telescoping action of the four ropes 5 is controlled by linkage to make the section of the mechanical arm reach the preset spatial position and deformation amount. The section of liquid low-melting point alloy 4 is solidified, so far the movement of this section of the mechanical arm is completed and can continue to be kept fixed. After that, the above steps are carried out step by step from the fixed end to the end, and finally the overall spatial shape of the manipulator can match the set shape, and the deformation process of the manipulator is completed.

Claims (6)

1. The mechanical arm 1. one kind is coupled hardness with softness, it is characterised in that: appearance is that a cylinder is whole, and material of main part uses elastomer, internal For ectonexine coaxial configuration, multiple axial ducts are evenly distributed in its outer annular, the rope for changing mechanical arm form is placed in inside；In Interbed annular is evenly distributed with multiple axial ducts, and heater and thermistor are placed in inside；Robot central has an airtight chamber, internal It is perfused with low-melting alloy, middle layer is as close as possible to airtight chamber.
2. The mechanical arm 2. one kind according to claim 1 is coupled hardness with softness, it is characterised in that: material of main part is silica gel.
3. The mechanical arm 3. one kind according to claim 1 is coupled hardness with softness, it is characterised in that: low-melting alloy is gallium-indium alloy.
4. The mechanical arm 4. one kind according to claim 1 is coupled hardness with softness, it is characterised in that: mechanical arm deformation sequence is by fixing End starts to stop after to rope linkage control deformation quantity after the piecewise heating hot metal of mechanical arm tail end heating to fix deformation angle The mechanical arm of degree, final all parts sets deformation angle, then mechanical arm is that a fixed rigidity is whole.
5. The mechanical arm 5. one kind according to claim 1 is coupled hardness with softness, it is characterised in that: the length of every section of mechanical arm is by every Electric heating wire length determines that the robot that will couple hardness with softness is divided into more multistage, and it is then higher that robot controls precision.
6. The mechanical arm 6. one kind according to claim 1 is coupled hardness with softness, it is characterised in that: middle layer annular it is uniformly distributed it is multiple with The cooling medium channel of the axial duct of placement heater and thermistor separately.