Composition of Welding Manipulators:

Welding manipulators primarily consist of three major components: the end-effector, the drive mechanism, and the control system. The end-effector is the component used to grasp workpieces (or tools). Its structure varies based on the shape, dimensions, weight, material, and operational requirements of the object being grasped, including types such as gripping, supporting, and suction. The motion mechanism enables the end effector to perform various rotations (swivels), translations, or compound motions to execute specified actions, altering the position and orientation of the grasped object. The independent movement capabilities of the motion mechanism—such as lifting, extending, retracting, and rotating—are referred to as the robot's degrees of freedom. To grasp objects at any position and orientation in space, six degrees of freedom are required. Degrees of freedom are a key parameter in robotic arm design. More degrees of freedom enhance flexibility and versatility but increase structural complexity. Specialized robotic arms typically have 2 to 3 degrees of freedom. The control system executes specific actions by controlling motors for each degree of freedom. It simultaneously receives feedback from sensors to establish stable closed-loop control. The control system's core is usually a microcontroller chip, such as a microcontroller or DSP, programmed to achieve desired functions.

Actuators of Welding Manipulators:

Manipulator actuators comprise the hand, arm, and torso;

1. Hand

The hand is mounted at the arm's front end. A drive shaft within the arm's inner bore transmits motion to the wrist, enabling rotation, extension/flexion, and finger opening/closing.

The gripper's structure mimics human fingers, categorized into three types: fingerless, fixed-joint, and free-joint. The number of fingers can be two, three, or four, with two-finger configurations being most common. Various gripper shapes and sizes can be configured based on the object's form and dimensions to meet operational requirements. A fingerless gripper typically refers to a vacuum suction cup or magnetic chuck.

2. Arm

The arm guides the fingers to accurately grasp workpieces and transport them to designated positions. For precise operation, all three degrees of freedom of the arm must be accurately positioned.

3. Torso
The torso serves as the mounting frame for the arm, power source, and various actuators.

Welding Manipulator Drive Mechanisms:

Four primary drive mechanisms are used in manipulators: hydraulic drive, pneumatic drive, electric drive, and mechanical drive. Hydraulic and pneumatic drives are the most commonly employed.

1. Hydraulic Drive

Hydraulically driven manipulators typically consist of a drive system comprising hydraulic actuators (various cylinders and motors), servo valves, pumps, and reservoirs. This system powers the manipulator's effectors. Such systems offer substantial lifting capacity (often exceeding several hundred kilograms) and feature compact design, smooth motion, impact resistance, vibration tolerance, and excellent explosion-proof properties. However, hydraulic components demand high manufacturing precision and sealing performance; otherwise, oil leakage may cause environmental contamination.

2. Pneumatic Drive

The drive system typically comprises air cylinders, pneumatic valves, air tanks, and air compressors. Key advantages include readily available air sources, rapid response, simple structure, lower cost, and ease of maintenance. However, precise speed control is challenging, and operating pressure must remain within limits, resulting in lower lifting capacity.

3. Electrically Driven Electric drive is the most widely used drive method for robotic arms. Its advantages include readily available power sources, fast response times, high driving force (jointed types can handle loads up to 400kg), and convenient signal detection, transmission, and processing. It also supports various flexible control schemes. Drive motors typically use stepper motors, with DC servo motors (AC) as the primary drive method. Due to the high motor speeds, reduction mechanisms are usually required (e.g., harmonic drives, RV cycloidal drives, gear drives, worm drives, and multi-link mechanisms). Some robotic arms now employ direct drive (DD) using high-torque, low-speed motors without reduction gears. This simplifies the mechanism while improving control precision.

4. Mechanical Drive

Mechanical drives are used only for applications with fixed motions. Typically, cam-linkage mechanisms are employed to execute specified actions. Their characteristics include reliable and precise operation, high working speeds, and low cost, though they are difficult to adjust. Other approaches include hybrid drives, such as hydraulic-pneumatic or electro-hydraulic hybrid systems.

Control Systems for Welding Manipulators:

Key control elements for manipulators include work sequence, target position, action timing, movement speed, acceleration/deceleration, etc. Manipulator control is categorized into point-to-point control and continuous trajectory control.

Control systems can be designed with digital sequential control based on operational requirements. This involves programming and storing sequences, then executing the manipulator according to the stored program. Program storage methods include distributed storage and centralized storage. Distributed storage involves storing different control parameters across multiple devices: sequence data on plugboards, cam drums, or punched tape; positional data on time relays or constant-speed rotary drums. Centralized storage consolidates all control parameters into a single device, such as magnetic tape or magnetic drums. This method is used when sequence, position, timing, and speed require simultaneous control—i.e., in continuous control scenarios.

Punch cards are employed when rapid program changes are required. Switching programs only necessitates replacing a single punch card, and the same card can be reused repeatedly. Punch tape can accommodate programs of unlimited length, but must be entirely replaced if errors occur. Punch cards have limited information capacity but are easy to replace, store, and reuse. Magnetic cores and magnetic drums are only suitable for applications requiring large storage capacities. The selection of control components depends on the complexity and precision of the required movements. For complex robotic arms, teach-and-repeat control systems are employed. More intricate robotic arms utilize digital control systems, microcomputer-controlled systems, or microprocessor-controlled systems. Pin-tape systems are most commonly used for control systems, followed by cam drums. These drums are equipped with multiple cams, each assigned to a specific motion axis, completing one cycle per drum rotation.

Advantages of Welding Manipulators:

Manipulators reduce labor requirements, enhance efficiency, lower costs, improve product quality, offer superior safety, and elevate factory image.

Advantages of articulated manipulators include: flexible motion, low inertia, high versatility, ability to grasp workpieces near the base, and maneuvering around obstacles between the body and work machinery. Production demands increasingly require higher flexibility, positioning accuracy, and operational space for articulated arms. Multi-jointed arms have transcended traditional concepts, featuring joint counts ranging from three to over a dozen. Their configurations are not limited to human-like arms but adapt to diverse operational scenarios. The superior performance of multi-jointed arms far surpasses that of single-jointed manipulators.

Application Prospects of Welding Manipulators:

With advancements in networking technology, networked operation of manipulators represents a future development direction. Industrial robots represent a high-tech automated production equipment developed over recent decades. Industrial manipulators constitute a vital branch of industrial robots. Characterized by programmable execution of diverse predefined tasks, they combine structural and functional advantages of both humans and machines, particularly embodying human intelligence and adaptability. The precision of manipulator operations and their capability to perform tasks across various environments offer broad development prospects across all sectors of the national economy.

Welding manipulators primarily consist of three major components: the end-effector, the drive mechanism, and the control system. The end-effector is the component used to grasp workpieces (or tools). Its structure varies based on the shape, dimensions, weight, material, and operational requirements of the object being grasped, including types such as gripping, supporting, and suction.