Kinematics parameters, material structure and cont

2022-08-12
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Detailed explanation of kinematics, parameters, materials, structure and control system of industrial robot: structure, drive and technology of industrial robot

1) common kinematic configuration

2) main technical parameters of robot

3) common materials of robot

4) main structure of robot

5) control system of robot

common kinematic configuration

1 Advantages of Descartes manipulator

it is easy to achieve high accuracy through computer control. Disadvantages: it hinders work, covers a large area, has low movement speed and poor sealing

① welding, handling, loading and unloading, packaging, palletizing, destacking, detection, flaw detection, classification, assembly, labeling, code spraying, code printing, (soft imitation) spraying, target following, blasting and other work

② it is especially suitable for flexible operations with multiple varieties and batches, and plays a very important role in stabilizing, improving product quality, improving labor productivity, improving labor conditions and rapid product upgrading

2. Hinge type operating arm (joint type)

the joints of joint robots are all rotating, similar to human arms, which is the most common structure in industrial robots. Its scope of work is more complex

① rapid testing and product development of auto parts, molds, sheet metal parts, plastic products, sports equipment, glass products, ceramics, aviation, etc

② CMM measurement and error detection for manufacturing quality control of body assembly, general mechanical assembly, etc

③ rapid prototyping of antiques, works of art, sculptures, cartoon character modeling, portrait products, etc

④ vehicle on-site measurement and detection

⑤ human body shape measurement, bone and other medical equipment production, human body shape production, medical cosmetic surgery, etc

3. SCARA manipulator

scara robots are often used in assembly operations. The most remarkable feature is that their movement on the X-Y plane has great flexibility, and they have strong rigidity along the Z axis. Therefore, it has selective flexibility. This kind of robot has been well applied in assembly work

① it is widely used for assembling printed circuit boards and electronic parts

② moving and placing objects, such as integrated circuit boards

③ it is widely used in plastic industry, automobile industry, electronic products industry, pharmaceutical industry, food industry and other fields

④ carry out parts and assembly work

4. Spherical coordinate operating arm

features: the working range near the central support is large, and the two rotating driving devices are easy to seal, covering a large working space. However, the coordinate is complex and difficult to control, and the linear drive device has the problem of sealing

5. Cylindrical coordinate manipulator

advantages: simple calculation; The linear part can be hydraulically driven, which can output large power; It can reach into the cavity machine. Disadvantages: the space that its arms can reach is limited, and it cannot reach the space near the column or the ground

the linear drive part is difficult to seal and prevent dust; When the rear arm works, the rear end of the arm will touch other objects within the working range

6. Redundant mechanism

usually six degrees of freedom are required for spatial positioning, and the use of additional joints can help the mechanism avoid singular configurations. The following figure shows the configuration of the 7-DOF operating arm

7. Closed loop structure

closed loop structure can improve the stiffness of the mechanism, but it will reduce the range of joint motion and reduce the workspace to a certain extent

① motion simulator

② parallel machine tool

③ micromanipulation robot

④ force sensor

⑤ cell operated robots in biomedical engineering can realize cell injection and segmentation

⑥ microsurgery robot

⑦ attitude adjustment device of large radio astronomical telescope

⑧ hybrid equipment, such as the Tricept hybrid manipulator module of SMT company, is a successful example of modular design based on parallel mechanism units

several common structural forms of industrial robots (Figure) ▼

main technical parameters of robots

technical parameters of robots reflect the competent work and the highest operating performance of robots, which must be considered in the design and application of robots. The main technical parameters of the robot include degrees of freedom, resolution, workspace, working speed, working load, etc

1, degree of freedom

the number of independent coordinate axis motions that the robot has. The degree of freedom of robot refers to the number of independent motion parameters required to determine the position and posture of robot hand in space. The opening and closing of fingers and the degree of freedom of finger joints are generally excluded The number of degrees of freedom of a robot is generally equal to the number of joints. The number of degrees of freedom commonly used by robots generally does not exceed 5~6

2. Joint

is a mechanism that allows relative motion between parts of the robot arm

3. Workspace

all space areas that can be reached by the robot arm or hand installation point. Its shape depends on the number of degrees of freedom of the robot and the type and configuration of each moving joint. The workspace of robot is usually represented by graphical method and analytical method

4. Working speed

the distance or rotation angle of the mechanical interface center or tool center point in unit time during the uniform motion of the robot under the working load

5. Working load

refers to the maximum load that the robot can bear at any position within the working range, which is generally expressed by mass, torque and moment of inertia. It is also related to the direction of running speed and acceleration. Generally, the weight of the workpiece that can be grabbed during high-speed operation is specified as the bearing capacity index

6. The minimum moving distance or rotation angle that can be achieved by the resolution

7. Accuracy

repeatability or repeated positioning accuracy: refers to the difference degree of the robot repeatedly reaching a certain target position. Or under the same position command, the robot repeats its position dispersion several times continuously. It measures the density of a series of error values, that is, the degree of repetition

materials commonly used in robots

1, carbon structural steel and alloy structural steel

these materials have good strength, especially alloy structural steel, whose strength has increased by 4-5 times, elastic modulus E is large, and deformation resistance is strong. They are the most widely used materials

2. Aluminum, aluminum alloy and other light alloy materials

the common characteristics of these materials are light weight, small elastic modulus E, but low material density, so e/ρ The ratio can still be compared with steel. The quality of some rare noble aluminum alloys has been more significantly improved. For example, the elastic modulus of aluminum alloys added with 3.2% (weight percentage) lithium has increased by 14%, e/ρ Increased by 16% over the previous year

3, fiber reinforced alloy

such alloys as boron fiber reinforced aluminum alloy, graphite fiber reinforced magnesium alloy, etc/ρ The ratio reached 11.4 respectively × 107 and 8.9 × 107。 This fiber reinforced metal material has a very high e/ρ But the price is expensive

4. Ceramics

ceramic materials have good quality, but they are brittle and difficult to process. Japan has trial produced a ceramic robot arm sample used in small high-precision robots from the previous and current situation, which has almost no self-locking property in the ball screw

5, fiber reinforced composites

these materials have excellent e/ρ It also has the outstanding advantage of large damping. Traditional metal materials cannot have such large damping, so there are more and more examples of composite materials used in high-speed robots

6. Viscoelastic large damping material

increasing the damping of the robot connecting rod is an effective method to improve the dynamic characteristics of the robot. At present, there are many methods to increase the damping of structural materials, among which the most suitable method for robots is to use viscoelastic large damping materials to damp the original components

main structure of robot

1. Robot driving device

concept: in order to make the robot run, it is necessary to place a transmission device for each joint, that is, each degree of freedom of motion. Function: provide the motive force for the action of each part and joint of the robot

drive system: it can be hydraulic transmission, pneumatic transmission, electric transmission, or an integrated system combining them; It can be driven directly or indirectly through mechanical transmission mechanisms such as synchronous belts, chains, gear trains, harmonic gears, etc

1) electric drive

the electric drive has simple energy, wide speed range, high efficiency, and high speed and position accuracy. However, most of them are connected with the reducer, so it is difficult to drive directly

electric drive devices can be divided into DC, AC servo motor drive and stepper motor drive. The brush of DC servo motor is easy to wear and spark. Brushless DC motor has also been more and more widely used. Stepper motor drive is mostly open-loop control, which is simple to control but has little power. It is mostly used in low-precision and low-power robot systems

check whether the power supply voltage is appropriate (overvoltage is likely to cause damage to the drive module) before the electric machine is powered on for operation; The +/- polarity of DC input must not be connected incorrectly, and whether the motor model or current setting value on the drive controller is appropriate (not too large at the beginning)

the control signal line is firmly connected, and it is best to consider the shielding problem on the industrial site (such as using twisted pair)

don't connect all the wires that need to be connected at the beginning, only connect them into the most basic system, and then connect them step by step after running well

be sure to find out the grounding method, or adopt floating without grounding

within half an hour after the start of operation, closely observe the state of the motor, such as whether the movement is normal, sound and temperature rise. If any problem is found, stop the machine immediately for adjustment

2) hydraulic drive

is completed by the high-precision cylinder block and piston, and the linear motion is realized by the relative motion of the cylinder block and piston rod

advantages: large power, can be directly connected with the driven rod without the reduction device, compact structure, good stiffness, fast response, and high accuracy of servo drive

disadvantages: it needs to add a hydraulic source, which is easy to produce liquid leakage, and is not suitable for high and low temperature occasions. Therefore, hydraulic drive is currently mostly used in super high-power robot systems

select the appropriate hydraulic oil. Prevent solid impurities from mixing into the hydraulic system and prevent air and water from invading the hydraulic system. The mechanical operation should be gentle and smooth. The mechanical operation should avoid rough, otherwise it will inevitably produce impact load, which will cause frequent mechanical failures and greatly shorten the service life. Pay attention to cavitation and overflow noise. Pay attention to the sound of the hydraulic pump and overflow valve at all times during operation. If the hydraulic pump has "cavitation" noise, which cannot be eliminated after venting, the reason should be found out and the fault should be eliminated before use. Maintain proper oil temperature. The working temperature of the hydraulic system is generally controlled between 30~80 ℃

3) pneumatic drive

pneumatic drive has simple structure, clean, sensitive action and cushioning effect However, compared with the hydraulic drive device, the power is small, the stiffness is poor, the noise is large, and the speed is not easy to control, so it is mostly used for point control robots with low accuracy

(1) it has the characteristics of fast speed, simple system structure, convenient maintenance and low price. It is suitable for robots with medium and small loads. However, because it is difficult to realize servo control, it is mostly used in robots with program control, such as loading, unloading and stamping robots

(2) in most cases, it is used to realize two digit contingent

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