The idea and principle of the overall design of the handling robot

Handling is a device used for motion control, generally composed of an execution system, a drive system and. The handling robot has the advantages of simple structure, low cost and ease. It can replace people to do work, move the workpiece from a certain place to a designated working position, or manipulate the workpiece for processing according to work requirements. Let's learn about the handling robot and its structure.

1. Design principle of handling robot

The handling robot is a movable gantry structure, and the arm bearing mechanism can move along the guide rail, which is installed on the column and is located above the guarded equipment.

1. The arm bearing mechanism moves along the guide rail, and the double-acting cylinder drive device installed on the bearing mechanism ensures that the manipulator arm can achieve a reciprocating motion of 600 mm.

2. The rotation of the arm in the shoulder joint is achieved by a double-acting cylinder drive mounted on the bearing mechanism, a motion transmission mechanism and a ball screw mounted on the shoulder.

3. The rotation of the arm in the elbow joint is achieved by a double-acting cylinder drive device installed on the forearm and a motion transmission mechanism.

2. The overall design idea of ​​the handling robot

Designing a robot can generally be divided into two stages:

1. System analysis phase

① Based on the system’s goals, clarify the purpose and tasks of the robots used.

②Analyze the working environment of the robot system.

③ According to the working requirements of the robot, determine the basic functions and solutions of the robot, such as the robot's degree of freedom, storage capacity, computer function, motion accuracy requirements, the weight that can be grasped, the allowable range of motion, and adaptability to temperature, vibration and other environments.

2. Technical design stage

① Determine the robot's degrees of freedom and allowable spatial working range according to the system requirements, and select the robot's coordinate form.

② Draw up the robot’s movement route and spatial operation diagram.

③Determine the type of drive system.

④ Select the specific structure of each component and design the robot assembly drawing.

⑤Draw the parts diagram of the robot and determine the dimensions.

3. Structural composition of the handling robot

The handling robot consists of three parts: actuator, drive mechanism and control mechanism.

1. Executive agency

(1) Hands

The hand is the part that directly contacts the workpiece, and is generally of the rotary or translation type (mostly rotary type because of its simple structure). The hand usually has two fingers (some have multiple fingers); it can be divided into external gripping type and internal gripping type according to the needs; negative pressure or vacuum air suction cups (mainly used for adsorbable, smooth surface parts or thin plate parts) and electromagnetic suction cups can also be used.

There are many types of force transmission mechanisms, and the commonly used ones are: slide lever type, connecting rod lever type, inclined wedge lever type, gear rack type, screw nut type, spring type and gravity type. The hand designed this time chooses a clamping type rotary structure hand.

The hand performs the opening and closing movement by means of the telescopic movement of the rod, the power source of the rod comes from the hydraulic cylinder of the subsequent driving source, and the hydraulic cylinder adopts a telescopic hydraulic cylinder, which can save the lateral working space.

(2) Wrist

The wrist is a part that connects the hand and the arm, and can be used to adjust the position of the grasped object to expand the range of motion of the hand and make the manipulator more dexterous and more adaptable. The wrist has independent degrees of freedom. There are rotational motion, up and down swing, and left and right swing. Generally, the wrist is equipped with rotational motion and an up and down swing can meet the work requirements. Some special manipulators with simpler movements can directly use the arm movement to drive the hand to carry the workpiece without a wrist in order to simplify the structure.

At present, the most widely used wrist rotation mechanism is the rotary hydraulic (gas) cylinder, which has a compact and flexible structure but a small rotation angle (generally less than 270°) and requires strict sealing, otherwise it is difficult to ensure stable output torque. Therefore, when a larger rotation angle is required, a rack drive or sprocket and gear train structure is used. The wrist of the handling robot designed in this paper realizes 180° rotation of the hand.

The wrist is driven by direct drive. Since the wrist is installed at the end of the arm, it must be designed to be very compact so that the drive source can be installed on the wrist. The opening and closing of the robot hand is driven by a double-acting single-piston hydraulic cylinder; while the rotation of the wrist is achieved by a rotary hydraulic cylinder. The outer shell of the clamping piston cylinder is connected to the moving plate of the swing cylinder; when oil is added to different oil chambers in the rotary hydraulic cylinder, the wrist can be rotated in different directions.

(3) Arm

The arm is an important gripping part of the robot. Its function is to support the wrist and hand (including work or fixture) and drive them to move in space.

The purpose of arm movement is to move the hand to any point within the range of spatial movement. If the hand posture (orientation) is changed, it is achieved by using the wrist's degrees of freedom. Therefore, generally speaking, the arm must have three degrees of freedom to meet the basic requirements, namely, extension and retraction, left and right rotation, and lifting (or pitching) of the arm.

The various movements of the arm are usually realized by driving mechanisms (such as hydraulic cylinders or pneumatic cylinders) and various transmission mechanisms. From the analysis of the force on the arm, it is subjected to static and dynamic loads from the wrist, hand and workpiece during work, and its own movements are relatively large, and the force is complex. Therefore, its structure, working range, flexibility, grasping size and positioning accuracy directly affect the working performance of the manipulator. This design realizes the up and down movement, front and back telescopic movement, and rotation movement of the arm. Movement of the arm: telescopic stroke: 1200mm; telescopic speed: 83mm/s; lifting stroke: 300mm; lifting speed: 67mm/s; rotation range: 180~0. The extension and retraction of the robot arm changes the working length of its arm. In the cylindrical coordinate structure, the maximum working length of the arm determines the diameter of the cylindrical surface that can be reached at its end. The telescopic arm mechanism can be driven directly by a hydraulic cylinder.

(4) Machine base

The base is the basic part of the robot body and plays a supporting role. For fixed robots, it is directly connected to the ground, and for movable robots, it is installed on the mobile structure. The fuselage is composed of the arm movement (lifting, translation, rotation and pitching) mechanism and its related guide devices, support parts, etc. In addition, the drive devices or transmission parts of the arm's lifting, rotation or pitching movements are installed on the fuselage. The more arm movements, the more complex the structure and force of the fuselage. The fuselage of the handling robot in this graduation project adopts a lifting and rotating fuselage structure; the configuration type of the arm and the fuselage adopts a column-type single-arm configuration, and its drive source comes from a rotary hydraulic cylinder.

2. Driving mechanism

The driving mechanism is an important part of the handling robot. According to the different power sources, the driving mechanism of industrial manipulators can be roughly divided into four categories: hydraulic, pneumatic, electric and mechanical drive.

(1) Hydraulic transmission. It has a large power-to-volume ratio and is often used in large load situations. The pressure and flow are easy to control and the speed can be adjusted steplessly. It is sensitive to reaction and can achieve continuous trajectory control and is easy to maintain. However, the liquid is sensitive to temperature changes and oil leakage is prone to ignition. It is used in small and medium-sized special manipulators or robots, and heavy-duty manipulators are mostly hydraulically driven. The cost of hydraulic components is relatively high and the oil circuit is relatively complex.

(2) Pneumatic transmission. The pneumatic system is simple and low-cost. It is suitable for situations with fast cycles, small loads and low precision requirements. It is often used for point control, grasping, elastic gripping and vacuum adsorption. It can be high-speed, but the impact is severe and accurate positioning is difficult. It is easy to maintain and can be used in harsh environments such as high temperature and dust. Leakage has no effect. It is used in small and medium-sized special manipulators or robots.

(3) Electric. There are asynchronous, DC motor, stepper or other electric drive modes. Electric motors are easy to use, and with the improvement of material properties, the performance of electric motors is gradually improving. At present, they are mainly suitable for medium loads, especially for complex movements, strict motion trajectories and various micro robots.

(4) Brake: A brake is a device that converts the energy of a moving part of a machine into heat energy and releases it, thereby reducing or stopping the speed of the moving machine. It can be roughly divided into two categories: mechanical brakes and brakes. In a robot mechanism, the situations in which brakes are used are as follows: