Structure of Welding Manipulator

It is mainly composed of three parts: actuator, drive mechanism, and control system.

The hand is a part used to grasp the workpiece (or tool), and has a variety of structural forms according to the shape, size, weight, material and operation requirements of the object being grasped, such as clamping type, holding type and adsorption type, etc. The motion mechanism enables the hand to complete various rotations (swings), movements, or compound movements to achieve prescribed movements, and change the position and posture of the grasped object. The independent movement methods such as lifting, telescopic and rotating of the motion mechanism are called the degrees of freedom of the manipulator. In order to grab objects at any position and orientation in space, 6 degrees of freedom are required. The degree of freedom is a key parameter for robot manipulator design. The more degrees of freedom, the greater the flexibility of the manipulator, the wider the versatility, and the more complex the structure. General special manipulators have 2 to 3 degrees of freedom. The control system is to complete specific actions by controlling the motor of each degree of freedom of the manipulator. At the same time, the information fed back by the sensor is received to form a stable closed-loop control. The core of the control system is usually constituted by a micro-control chip such as a single chip microcomputer or DSP, and the desired function is realized by programming it.

Executive body

The execution mechanism of the welding manipulator is divided into hand, arm, and torso.

hand

The hand is mounted on the front of the arm. A transmission shaft is installed in the inner hole of the arm, and the application can be transmitted to the wrist to rotate, stretch the wrist, and open and close the fingers. The structure of the hand of the manipulator imitates human fingers and is divided into three types: no joint, fixed joint, and free join. The number of fingers can be divided into two fingers, three fingers, four fingers, etc. Among them, two fingers are the most used. According to the shape and size of the clamping object, a variety of shapes and sizes of chucks can be equipped to meet the needs of the operation. The so-called hands without fingers generally refer to vacuum suction cups or magnetic suction cups.

Arm

The role of the arm is to guide the finger to accurately grasp the workpiece and transport it to the desired position. In order for the manipulator to work correctly, the three degrees of freedom of the arm must be accurately positioned.

The torso is a bracket for mounting arms, power sources, and various actuators.

Drive mechanism

There are four main types of drive mechanisms used by manipulators: hydraulic drives, pneumatic drives, electrical drives, and mechanical drives. Among them, hydraulic drive and pneumatic drive are used the most.

Welding Manipulator

Hydraulic drive

Welding manipulator China usually consists of a hydraulic system (various oil cylinders, oil motors), servo valves, oil pumps, oil tanks, etc. to form a drive system, which is driven by the actuator of the manipulator to work. Generally, it has a large snatching capacity (up to several hundred kilograms or more), which is characterized by compact structure, smooth movement, impact resistance, vibration resistance, and explosion-proof performance, but hydraulic components require high manufacturing accuracy and sealing performance. Otherwise, oil leakage will pollute the environment. The pneumatic drive type drive system usually consists of an air cylinder, air valve, air tank, and air compressor. It is characterized by convenient air sources, rapid action, simple structure, low cost, and easy maintenance. But it is difficult to control the speed, and the air pressure should not be too high, so the snatch ability is low. Electrically driven electric drives are the most frequently used drive method for manipulators. It is characterized by the convenient power supply, fast response, the large driving force (articulated weight has reached 400kg), convenient signal detection, transmission, processing, and can use a variety of flexible control schemes. The driving motor generally adopts a stepping motor, and a DC servo motor (AC) is the main driving method. Due to the high speed of the motor, a speed reduction mechanism (such as harmonic drive, RV cycloidal pinwheel drive, gear drive, screw drive, and multi-rod mechanism, etc.) is usually required. Some manipulators have begun to use high-torque, low-speed motors without deceleration mechanisms for the direct drive (DD). This can both simplify the mechanism and improve control accuracy. The mechanical drive type of mechanical drive is only used in fixed action. Generally, a cam link mechanism is used to achieve a prescribed action. It is characterized by reliable movement, high working speed, and low cost, but it is not easy to adjust. Others use hybrid drives, namely liquid-gas or electro-hydraulic hybrid drives.

Control System

The elements controlled by the manipulator include work sequence, arrival position, action time, movement speed, acceleration, and deceleration, etc. The control of the manipulator is divided into point control and continuous trajectory control.

The control system can be designed to use digital sequence control according to the requirements of the action. It must first compile a program to store it, and then according to the prescribed program, control the manipulator to carry out the work program storage method has separate storage and centralized storage. Separate storage is to store the information of various control factors in more than two storage devices, such as sequence information in the latch plate, cam drum, and perforated belt; position information in the time relay, fixed speed rotary drum, etc.; Centralized storage is to store all the information of various control factors in a storage device, such as magnetic tape and magnetic drum. This method is used when the sequence, position, time, speed, etc. must be controlled simultaneously, that is, in the case of continuous control.

Among them, the latch board is used on occasions where the program needs to be changed quickly. To change a program, only one type of plugboard can be replaced, and the same plug-in can be used repeatedly; the length of the program accommodated by the punching tape can be unlimited, but it must be replaced if an error occurs; the information capacity of the punched card is limited, But it is easy to replace, save, and can be reused; the magnetic core and drum are only suitable for occasions with large storage capacity. As for which control element to choose, it is determined according to the complex and precise procedures of the action.

For manipulators with complex movements, a repetitive control system is used. More complex manipulators use digital control systems, small computers, or microprocessor-controlled systems.

The control system uses the bolt plate most, followed by the cam drum. It is equipped with many cams, each of which is assigned to a motion axis, and the drum completes one cycle after a week of movement.