There are four main types of driving mechanisms used in robotic arms: hydraulic drive, pneumatic drive, electrical drive, and mechanical drive.
1. Hydraulic driven
A hydraulic driven robotic arm usually consists of a hydraulic motor (various oil cylinders, oil motors), servo valves, oil pumps, oil tanks, etc., forming a driving system, which is operated by the actuator of the driving robotic arm. Usually, it has great gripping capacity (up to several hundred kilograms or more), characterized by compact structure, smooth operation, impact resistance, vibration resistance, and good explosion-proof performance. However, hydraulic components require high manufacturing accuracy and sealing performance, otherwise oil leakage will pollute the environment.
2. Pneumatic driven
The driving system is usually composed of cylinders, valves, tanks, and air compressors, characterized by convenient air supply, rapid action, simple structure, low cost, and convenient maintenance. But it is difficult to control the speed, and the air pressure should not be too high, so the gripping ability is low.
3. Electrically driven
Electric drive is the most commonly used driving method for robotic arms. Its characteristics are convenient power supply, fast response, large driving force (the weight of the joint type has reached 400kg), convenient signal detection, transmission, and processing, and various flexible control schemes can be adopted. The driving motor generally adopts a stepper motor, with DC servo motor (AC) as the main driving method. Due to the high speed of the motor, it is usually necessary to use a reduction mechanism (such as harmonic drive, RV cycloidal pinwheel drive, gear drive, screw drive, and multi bar mechanism). Some robotic arms have begun to use high torque, low speed motors without reduction mechanisms for direct drive (DD), which can simplify the mechanism and improve control accuracy.
4. Mechanical driven
Mechanical drive is only used in situations where the action is fixed. Generally, cam linkage mechanisms are used to achieve specified actions. Its characteristics are reliable movement, high working speed, low cost, but not easy to adjust. Others also use hybrid drive, namely liquid gas or electric hydraulic hybrid drive.
Secondly, according to the different motion forms of the manipulator, the manipulator can be divided into four types: Cartesian coordinate system type, cylindrical coordinate type, polar coordinate type and multi joint type.
(1). Cartesian coordinate system manipulator: the arm moves in a straight line in the three coordinate axes of the Cartesian coordinate system system, that is, the arm stretches back and forth, rises and falls up and down, and moves left and right. This coordinate form occupies a large space but has a relatively small working range and large inertia, making it suitable for situations where the working positions are arranged in a straight line.
(2). Cylindrical coordinate robotic arm: The arm moves forward and backward, up and down, and swings in a horizontal plane. Compared with Cartesian coordinate system, it takes up less space and has a larger working range. However, due to the mechanism structure, the lowest position in the height direction is limited, so objects on the ground cannot be grasped, and the inertia is also large.