Structure diagram of robot body-1
1、 Robot driving device
Concept: in order to make the robot run, it is necessary to install a transmission device for each joint, that is, each degree of freedom. The function is to provide the motive force for each part and joint of the robot.
Drive system: can be hydraulic transmission, pneumatic transmission, electric transmission, or a combination of them; It can be directly driven or indirectly driven by mechanical transmission mechanisms such as synchronous belt, chain, gear train and harmonic gear.
Robot motor drive-1
1. Electric drive
The electric drive device has the advantages of simple energy, wide speed range, high efficiency, high speed and position accuracy. But most of them are connected with speed reducer, so it is difficult to drive them directly.
Electric drive device can be divided into DC, AC servo motor drive and stepper motor drive. The brush of DC servo motor is easy to wear and spark. Brushless DC motor has been more and more widely used. Stepper motor drive is mostly open-loop control, simple control but low power, which is mostly used in low precision and low power robot system.
The following inspection shall be conducted before the electric power on operation:
1) Whether the power supply voltage is appropriate (overvoltage is likely to cause damage to the drive module); The + / - polarity of DC input must not be wrongly connected, and whether the motor model or current setting value on the drive controller is appropriate (not too large at the beginning);
2) The control signal line is firmly connected, and the shielding problem (such as twisted pair) should be considered in the industrial field;
3) Don't connect all the wires that need to be connected at the beginning, just connect them into the most basic system, and then connect them step by step after they run well.
4) We must find out the grounding method, or use floating without grounding.
5) Within half an hour of starting operation, closely observe the state of the motor, such as whether the movement is normal, sound and temperature rise, and stop the machine immediately for adjustment if any problem is found.
2. Hydraulic drive
Through high-precision cylinder and piston to complete, through the cylinder and piston rod relative motion to achieve linear motion.
Advantages: high power, can omit the deceleration device, directly connected with the driven rod, compact structure, good stiffness, fast response, servo drive with high precision.
Disadvantages: it needs to add a hydraulic source, which is easy to produce liquid leakage, and is not suitable for high and low temperature occasions, so the hydraulic drive is mostly used for super high power robot system at present.
Select suitable hydraulic oil. Prevent solid impurities from mixing into the hydraulic system, and prevent air and water from invading the hydraulic system. Mechanical operation should be gentle and smooth, and rough operation should be avoided, otherwise it will inevitably produce impact load, which will lead to frequent mechanical failures and greatly shorten the service life. Pay attention to cavitation and overflow noise. Pay attention to the sound of the hydraulic pump and relief valve at all times during the operation. If the "cavitation" noise occurs in the hydraulic pump, it can not be eliminated after exhaust. The reason should be found out and the fault can be eliminated before use. Keep proper oil temperature. The working temperature of hydraulic system should be controlled between 30 ℃ and 80 ℃.
3. Pneumatic drive
The structure of pneumatic drive is simple, clean, sensitive and has buffering effect But compared with the hydraulic drive device, it has the advantages of small power, poor stiffness, high noise, and difficult to control the speed, so it is mostly used for the point position control robot with low precision.
(1) It has the characteristics of high speed, simple system structure, convenient maintenance and low price. It is suitable for medium and small load robots. But because it is difficult to realize servo control, it is mostly used in robot controlled by program, such as loading, unloading and stamping robot.
(2) In most cases, it is used to realize two position or limited point control of small and medium robots.
(3) At present, most of the control devices use programmable logic controller (PLC controller). In flammable and explosive situations, pneumatic logic elements can be used to form a control device.
2、 Linear transmission mechanism
The transmission device is the key part to connect the power source and the motion link. According to the joint form, the commonly used transmission mechanisms are linear transmission and rotary transmission.
The linear drive mode can be used for X, y, z direction drive of rectangular coordinate robot, radial drive and vertical lifting drive of cylindrical coordinate structure, and radial telescopic drive of spherical coordinate structure.
Linear motion can be converted from rotary motion to linear motion by gear rack, screw nut and other transmission elements. It can also be driven by linear drive motor or directly generated by the piston of cylinder or hydraulic cylinder.
1. Rack and pinion device
Usually the rack is fixed. The rotary motion of the gear is converted into the linear motion of the supporting plate.
·Advantages: simple structure.
·Disadvantages: large return difference.
Rack and pinion unit-1
2. Ball screw
The ball is embedded in the spiral groove of the screw and the nut, and the ball can circulate continuously through the guide groove in the nut.
·Advantages: small friction, high transmission efficiency, no crawling, high precision
·Disadvantages: high manufacturing cost and complex structure.
Self locking problem: in theory, the ball screw pair can also be self-locking, but in practice, it is not used. The main reasons are: poor reliability, or high processing cost; Because the ratio of diameter to lead is very large, generally a set of self-locking device such as worm gear is added.
3、 Rotating transmission mechanism
The purpose of using the rotary transmission mechanism is to convert the higher speed output by the motor drive source into a lower speed and obtain a larger torque. Gear chain, synchronous belt and harmonic gear are widely used in robot.
1. Gear chain
(1) Speed relationship
(2) Moment relation
2. Synchronous belt
Synchronous belt is a belt with many profile teeth, which is meshed with synchronous pulley with the same profile teeth. It works as a soft gear.
·Advantages: no sliding, good flexibility, low price, high repeat positioning accuracy.
·Disadvantages: it has certain elastic deformation.
3. Harmonic gear
Harmonic gear is composed of rigid gear, harmonic generator and flexible gear. Generally, the rigid gear is fixed and the harmonic generator drives the flexible gear to rotate.
Main features:
(1) The transmission ratio of single stage is 50-300.
(2) Stable transmission and high bearing capacity.
(3) High transmission efficiency, up to 70% - 90%.
(4) The transmission accuracy is 3-4 times higher than that of ordinary gear transmission.
(5) It can be less than 3 '.
(6) The flexspline stiffness is low.
Harmonic drive has been widely used in countries with advanced robot technology. Only in Japan, 60% of robot driving devices adopt harmonic drive.
The robot sent to the moon by the United States uses harmonic drive devices in all joints, and 30 harmonic drive mechanisms are used in one upper arm.
The mobile robot "lunar lander", which was launched into the moon by the former Soviet Union, has 8 wheels installed in pairs, which are separately driven by closed harmonic drive mechanism The rohren and gerot R30 robots developed by Volkswagen of Germany and the vertical 80 robots developed by Renault of France all adopt harmonic drive mechanism.
Harmonic gear-1
4、 Robot sensor system
1. The sensing system is composed of internal sensor module and external sensor module, which is used to obtain meaningful information in the internal and external environment.
2. The use of intelligent sensors improves the mobility, adaptability and intelligence of the robot.
3. The use of intelligent sensors improves the mobility, adaptability and intelligence of the robot.
4. For some special information, sensors are more effective than human sensory system.
5、 Robot position detection
Rotary optical encoder is the most commonly used position feedback device. Photodetectors convert light pulses into binary waveforms. The rotation angle of the axis is obtained by calculating the number of pulses, and the rotation direction is determined by the relative phase of the two square wave signals.
The inductosyn outputs two analog signals: sine signal and cosine signal. The rotation angle of the shaft is calculated by the relative amplitude of the two signals. Inductosyn is generally more reliable than encoder, but its resolution is lower.
Potentiometer is the most direct form of position detection. It is connected in the bridge, and can produce a voltage signal proportional to the shaft angle. However, due to low resolution, poor linearity and sensitivity to noise.
The tachometer can output the analog signal which is proportional to the shaft speed. If there is no such speed sensor, the speed feedback signal can be obtained by the difference of the detected position relative to time.
6、 Robot force detection
The force sensor is usually installed in the following three positions of the operating arm:
1. Mounted on joint drive. It can measure the torque or force output of the drive / reducer itself. However, the contact force between the end effector and the environment can not be well detected.
2. The wrist force sensor is installed between the end effector and the end joint of the operating arm. In general, three to six force / torque components applied to the end effector can be measured.
3. Mounted on the "fingertip" of the end effector. Usually, these fingers with force sensors are equipped with strain gauges, which can measure one to four components of force acting on the fingertip.
7、 Robot environment interaction system
1. Robot environment interaction system is a system to realize the interaction and coordination between industrial robot and equipment in external environment.
2. Industrial robot and external equipment are integrated into a functional unit, such as manufacturing unit, welding unit, assembly unit, etc. It can also be the integration of multiple robots, multiple machine tools or equipment, multiple parts storage devices, etc.
3. It can also be a multiple robots, multiple machine tools or equipment, multiple parts storage devices, etc. integrated into a functional unit to perform complex tasks.
8、 Human computer interaction system
Human computer interaction system is a device that enables operators to participate in robot control and contact with robot. The system can be divided into two categories: instruction device and information display device.


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