1, actuator
1) hand
The part of the hand in direct contact with the workpiece is generally rotating or translating (mostly rotating because of its simple structure). Most of the hands are two fingers (there are also many fingers); According to the need, it can be divided into two types: external grasping and internal grasping; Negative pressure or vacuum air suction cups (mainly used for adsorbable parts with smooth surface or thin plate parts) and electromagnetic suction cups can also be used.
There are many forms of force transmission mechanism, such as chute lever type, connecting rod lever type, wedge lever type, rack and pinion type, lead screw nut type, spring type, gravity type and so on. In this design, the hand is selected to hold the hand with rotating structure. Manual execution relies on the telescopic movement of the lever to realize its opening and closing movement. The power source of the rod comes from the hydraulic cylinder of the subsequent driving source, and the telescopic hydraulic cylinder can save the lateral working space.
2) Wrist
Wrist is the part connecting hand and arm, which can be used to adjust the orientation of the object being caught, thus expanding the action range of the manipulator and making the manipulator more dexterous and adaptable. Wrist has independent freedom. There is a rotating movement, swinging up and down, swinging left and right. Generally speaking, the wrist has a rotating motion and then swings up and down to meet the work requirements. In order to simplify the structure, some special manipulators with relatively simple movements can directly use arm movements to drive hands to carry workpieces without wrists.
At present, the most widely used wrist slewing mechanism is the slewing hydraulic (pneumatic) cylinder, which is compact and dexterous in structure but has a small slewing angle (generally less than? 270), and strict sealing is required, otherwise it is difficult to ensure the stability of output torque. Therefore, in the case of large rotation angle, rack transmission or sprocket and gear train structure is adopted. The wrist of the handling robot designed this time is to realize the hand? 180 rotation.
Wrist direct drive. Because the wrist is installed at the end of the arm, it must be designed very compactly, and the driving source can be installed on the wrist. The opening and closing of the robot hand is driven by a double-acting single-plunger hydraulic cylinder; The rotating motion of wrist is realized by rotating hydraulic cylinder. Connecting the shell of the clamping piston cylinder with the rotor of the oscillating cylinder; When supplying oil to different oil chambers in the rotary hydraulic cylinder, the wrist can rotate in different directions.
3) arms
The arm part is an important holding part of the manipulator. Its function is to support wrist and hand (including workpiece or fixture) and drive them to do spatial movement.
The purpose of arm movement is to send the hand to any point in the range of spatial movement. If the posture (orientation) of the hand changes, it is achieved through the freedom of the wrist. So generally speaking, the arm has three degrees of freedom to meet the basic requirements, that is, the arm's extension, left-right rotation, lifting (or pitching) movement.
Various movements of the arm are usually realized by driving mechanisms (such as hydraulic cylinders or cylinders) and various transmission mechanisms. From the force analysis of the arm, it not only bears the static and dynamic loads of the wrist, hand and workpiece, but also has many movements and complicated force. Therefore, its structure, working range, flexibility, small grasping weight and positioning accuracy directly affect the working performance of the manipulator. This design realizes the up-and-down movement, forward and backward expansion and rotation movement of the arm. Motion parameters of the arm: telescopic stroke:1200mm; Telescopic speed: 83 mm/s; Lifting stroke: 300mm vertical speed: 67mm/s; Rotation range: 180~0. The extension and contraction of the mechanical arm changes the working length of the arm. In the cylindrical coordinate structure, the maximum working length of the arm determines the diameter of the cylindrical surface that the end can reach. Telescopic arm mechanism can be directly driven by hydraulic cylinder.
4) Framework
The frame is the basic part of the fuselage robot and plays a supporting role. For the fixed robot, it is directly connected to the ground, and for the mobile robot, it is installed on the mobile structure. The fuselage consists of arm movement (lifting, translation, rotation and pitching) mechanism and its related guiding devices and supports. In addition, the driving device or transmission parts for lifting, rotating or pitching the arm are all installed on the fuselage. The greater the arm movement, the more complicated the fuselage structure and force. The body of the handling robot designed in this graduation project adopts the structure of lifting and rotating transformation; The configuration of the arm and fuselage adopts an upright single-arm configuration, and its driving source comes from a rotating hydraulic cylinder.
2. Rotating instrument device
The driving mechanism is an important part of the handling robot. According to the different power sources, the driving mechanism of industrial manipulator can be roughly divided into four categories: hydraulic drive, pneumatic drive, electric drive and mechanical drive.
(1) hydraulic transmission. It has a large power-volume ratio and is often used in heavy load situations. Pressure and flow are easy to control, and stepless speed regulation is possible; Sensitive response, continuous trajectory control and convenient maintenance; But liquid is sensitive to temperature change, and oil leakage is easy to catch fire; Small and medium-sized special manipulators or robots have applications, and heavy mechanical hands are mostly driven by hydraulic pressure; The cost of hydraulic components is high and the oil circuit is complicated.
(2) Pneumatic transmission. The pneumatic system is simple and low cost, which is suitable for occasions with fast beat, small load and low precision requirements. Commonly used in point control, grasping, elastic clamping, vacuum adsorption, etc., it can achieve high speed, but the impact is serious and the positioning is difficult. Simple maintenance, can be used in harsh environments such as high temperature and dust, and has no influence on leakage; Small and medium-sized special manipulators or robots have applications.
(3) electric. There are also asynchronous motors, DC motors, stepping or servo motors and other electric driving methods. The motor is simple to use, and with the improvement of material properties, the performance of the motor is gradually improved. At present, it is mainly suitable for medium load, especially for industrial robots and various micro-robots with complex motion and strict motion trajectory requirements.
(4) Brake:
Brake and its function: Brake is a device that converts the energy of mechanical moving parts into heat energy and releases it, so as to slow down or stop the moving mechanical speed. It can be roughly divided into mechanical braking and electric braking. In the robot mechanism, it is necessary to use the brakes as follows:
(1) Stop suddenly under special circumstances and need to take safety measures.
(2) In case of power failure, prevent moving parts from sliding and damaging other equipment.
Mechanical brake:
Mechanical brakes include spiral automatic loading brakes, disc brakes, shoe brakes and electromagnetic brakes. The most typical one is electromagnetic braking.
Servo motor is often used in the driving system of robot, and the characteristics of servo motor determine that electromagnetic brake is an essential component. In principle, this kind of brake is a disc brake which is braked by spring force. Only when the excitation current passes through the coil, the brake will open, and then the brake will not play a braking role. When there is no excitation current in the power-off coil, it will be in the normally closed mode under the action of spring force. Therefore, this kind of brake is called electromagnetic brake without excitation. Because this kind of brake is often used in safety braking occasions, it is also called safety brake.
electric brake
An electric motor is a device that converts electric energy into mechanical energy. On the contrary, it also has the power generation function of converting rotating mechanical energy into electrical energy. In other words, the servo motor is an energy conversion device, which converts electric energy into mechanical energy through its inverse process to achieve the purpose of braking. However, for different types of motors, such as DC motors, synchronous motors and induction motors, appropriate braking circuits must be adopted respectively.
3. Control mechanism
The core of building a robot platform is to build a robot control system. First, we need to choose the hardware platform. The hardware platform of the control system has a great influence on the openness, realization and development workload of the system. The commonly used hardware platform of control system should meet the following requirements: the hardware system is based on standard bus mechanism and has expansibility; The hardware structure has the necessary real-time computing ability; The hardware system is modular, which is convenient for adding or replacing various interfaces, sensors and special computers. Low cost. Up to now, the hardware platform of universal robot control system can be roughly divided into two categories: systems based on VME bus (Versamodel Eurocard, the first generation of 32-bit industrial open standard bus introduced by Motorola in 198 1) and systems based on PC bus. In recent years, with the rapid development of PC performance, the reliability has been greatly improved, but the price has been greatly reduced. The control system based on PC has been widely accepted in the field of robot control.