How does hydraulic casting manipulator work
The manipulator is mainly composed of three parts: the actuator, the driving mechanism and the control system. The hand is used to hold the workpiece (or tool) parts, according to the shape of the object to be held, size, weight, material and operational requirements and have a variety of structural forms, such as clamping type, holding type and adsorption type. A motor mechanism THAT enables the HAND to perform various rotations (swings), movements or COMBINATIONS of movements to achieve specified movements and change the position and posture of the object being held. The lifting, expansion, rotation and other independent motion modes of the motion mechanism are called the degrees of freedom of the manipulator.
In order to grasp the object at any position and orientation in space, 6 degrees of freedom are required. The degree of freedom is the key parameter of manipulator design. The more degrees of freedom, the greater the flexibility of the manipulator, the wider the versatility, the more complex the structure. General special manipulator has 2 ~ 3 degrees of freedom. The control system is through the control of the motor of each degree of freedom of the manipulator, to complete the specific action. At the same time, the sensor feedback information is received to form a stable closed-loop control. The core of the control system is usually composed of microcontroller or DSP and other microcontrol chips, through its programming to achieve the desired function.
I. Implementation mechanism
The executive mechanism of the manipulator is divided into hand, arm and trunk;
1, hand
The hand is mounted at the front of the arm. The inner hole of the arm is equipped with a drive shaft, which can be transferred to the wrist to rotate, extend the wrist, open and close the fingers.
The structure of the manipulator hand mimics human fingers and is divided into three kinds: unjointed, fixed and free joints. The number of fingers can be divided into two fingers, three fingers, four fingers, and so on, among which two fingers with the most. According to the shape and size of the clamping object can be equipped with a variety of shapes and sizes of the chuck to meet the needs of the operation. The so-called fingerless hand, generally refers to the vacuum or magnetic suction cup.
2, arm
The role of the arm is to guide the fingers to accurately grasp the workpiece and transport it to the desired position. In order for the manipulator to work correctly, all three degrees of freedom of the arm should be accurately positioned.
3, trunk trunk is the installation of arms, power sources and various actuators of the support.
Two, driving mechanism
The driving mechanism used by the manipulator mainly has 4 kinds: hydraulic drive, pneumatic drive, electrical drive and mechanical drive. Among them, hydraulic drive and pneumatic drive are used most.
1, hydraulic drive type
Hydraulic actuated manipulator is usually composed of hydraulic motor (various cylinders, oil motors), servo valve, oil pump, oil tank and other components of the drive system, which is driven by the manipulator actuator. Usually it has a great snatch capacity (up to hundreds of kilograms), which is characterized by compact structure, smooth action, impact resistance, shock resistance, good explosion-proof, but the hydraulic components require high manufacturing accuracy and sealing performance, otherwise oil leakage will pollute the environment.
2, air pressure driven type
The driving system is usually composed of cylinders, air valves, gas tanks and air compressors. It is characterized by convenient air source, rapid action, simple structure, low cost and convenient maintenance. But it is difficult to control the speed, the air pressure can not be too high, so the snatch ability is low.
3, electric drive type electric drive is the most used of the manipulator a driving mode. It is characterized by convenient power supply, fast response, large driving force (the weight of the joint type has reached 400kg), convenient signal detection, transmission and processing, and can use a variety of flexible control schemes. The driving motor is generally stepper motor, DC servo motor (AC) as the main driving mode. Because of the high speed of the motor, it is usually necessary to use deceleration mechanism (such as harmonic drive, RV cycloid pin drive, gear drive, spiral drive and multi-bar mechanism, etc.). Some manipulator has begun to use non-decelerating mechanism of large torque, low speed motor for direct drive (DD), which can simplify the mechanism, but also improve the control accuracy.
4, mechanical drive type
Mechanical drive is only used when the action is fixed. Generally, the CAM connecting rod mechanism is used to achieve the prescribed action. Its characteristics are reliable action, high working speed, low cost, but not easy to adjust. Others use hybrid drive, that is, liquid-gas or electric-liquid hybrid drive.
Three, control system
The elements of manipulator control include working sequence, arriving position, action time, movement speed, adding and subtracting speed and so on. The control of manipulator is divided into point control and continuous trajectory control.
The control system can be designed according to the requirements of the action, using digital sequence control. It first needs to be programmed to be stored, and then according to the prescribed program, the storage mode of the control manipulator for the working program has two kinds of separate storage and centralized storage. Separate storage is to store the information of various control factors in two or more storage devices, such as sequence information stored in the bolt board, CAM drum, perforation belt; The position information is stored in 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 tape, magnetic drum, etc. This method is used in order, position, time, speed and other occasions must be controlled at the same time, that is, the use of continuous control.
Where the latch board is used in the need for rapid change of procedures. Change a program only need to switch a pin plate limit, and the same plug-in can be used repeatedly; There is no limit to the length of the program that the perforated tape can hold, but it should be replaced in case of error. The information capacity of punch card is limited, but it is easy to change, save and reuse. Magnetic core and drum are only suitable for large storage capacity occasions. As for which control element to choose, it depends on the complex and precise procedures of the action. For the manipulator with complex movements, the teaching-seeking and reproducing control system is adopted. More complex manipulators use digital control systems, minicomputers or microprocessor-controlled systems. Control system with the pin board used most, followed by the CAM drum. It is equipped with a number of cams, each CAM assigned to a movement axis, the drum movement one week to complete a cycle.
