Servo motor is one of the three core parts of the robot as an actuator in the control system. Robot servo system is composed of servo motor, servo driver and command mechanism. Servo motor is the executive mechanism, which realizes motion. Servo driver is the power supply of servo motor. The command mechanism sends pulse or gives speed to cooperate with the normal operation of servo driver.
Domestic and foreign servo system manufacturers regard the robot market as the key development direction in the future. Servo motors are generally installed in the "joints" of robots. Robot joint drive can not be separated from servo system. The more joints, the higher the flexibility and accuracy of robots, the more servo motors to be used.
Robot demand is expanding all over the world, and China is now the fastest growing robot market in the world. From 2013 to 2016, China has become the world's largest consumer market of industrial robots for three consecutive years. IDC predicts that China's robot market will reach 59.4 billion US dollars by 2020. China's robot market will account for more than 30% of the total global robot market, with huge market space. The rapid growth of robots will drive the huge demand for servo motors.
In 2015, the market scale of robotic servo system in China is about 1.06 billion yuan. By 2020, the market scale will reach about 4.7 billion yuan, and the compound growth rate in the next five years will be about 35%.
Robot Joint Motor
Robot Servo Motors Face Challenges
Servo motors are often connected with terminal actuators in automated control systems, so they are also called executive motors. Servo motor is an actuator in servo system. Its function is to convert the pulse signal of servo controller into angular displacement and angular velocity of motor rotation.
Servo motors are divided into DC and AC servo motors. Compared with ordinary motors, their main characteristics are that they are usually used with feedback devices to achieve precise control.
Servo motor classification:
In order to improve the flexibility of industrial production, robots are becoming lighter and lighter. At the same time, in order to ensure the dynamics and accuracy of robots, high power density servo motors are very important. In the field of finishing, robots even need the flexibility of human hands, which requires motors to achieve high performance in the size of cans. In the field of medical robots, in order to enable robots to help patients recover health as soon as possible, the stability and reliability of motors are put forward the highest requirements.
The high requirements of robots for servo motors are as follows:
1. The servo motor is required to have fast response. The time from acquiring the command signal to completing the working state required by the command should be short. The shorter the response time of the command signal, the higher the sensitivity of the electro-servo system and the better the fast response performance. Generally, the electro-mechanical time constant of the servo motor is used to illustrate the fast response performance of the servo motor.
2. The starting torque inertia ratio of servo motor is larger. In the case of driving load, it is required that the starting torque of the servo motor of the robot is large and the moment of inertia is small.
3. Servo motor should have the continuity and linearity of control characteristic. With the change of control signal, the speed of motor can change continuously. Sometimes, the speed of servo motor must be proportional to or approximately proportional to the control signal.
4. In order to fit the body of the robot, the servo motor must be small in size, small in weight and short in axial dimension.
5. Can withstand harsh operating conditions, can carry out very frequent forward and backward acceleration and deceleration operation, and can withstand several times of overload in a short time. AC servo driver is widely used in industrial robots because of its high ratio of moment of inertia, brushless and commutation spark.
The gap is obvious, domestic manufacturers need to catch up
In the domestic servo motor market, the top three Panasonic, Mitsubishi and Anchuan are Japanese brands, with a total share of 45%. European brands such as Siemens, Bosch and Schneider mainly occupy the high-end market, with a market share of about 30%. The overall share of domestic enterprises is less than 10%.
Domestic servo motors mostly imitate Japanese servo motor design, with power less than 3 kw, medium and small power more, while 5.5-15 kW medium and high power servo motors are less.
Domestic servo motors still need to break through in the following aspects:
First, the shape is generally long and rough, which makes it difficult to apply to some high-end robots, especially on desktop robots with a light load of about 6 kg. Because the installation space of the arm of the robot is very narrow, the length of the servo motor is strictly required.
Secondly, the reliability of the signal connector needs to be improved, and it needs to be designed in the direction of miniaturization, high density and integration with the servo motor body to facilitate installation, debugging and replacement.
Thirdly, another core technology is the high-precision encoder, especially the multi-ring absolute value encoder used on robots, which relies heavily on imports, which is a big bottleneck restricting the development of high-end robots in China. Encoder miniaturization is also the core technology of servo motor miniaturization.
Fourthly, basic research is lacking, including absolute encoder technology, high-end motor manufacturing technology, breakthroughs in production technology, practical verification of performance indicators and formulation of assessment criteria.
Fifth, the insufficient synergy of all parts of the servo system industry leads to the difficulty of the overall performance of the servo motor and drive system.
Although the proportion of domestic servo motors in the market is relatively low, there is a big gap in technology and performance with foreign brands, and the product quality and stability can not be the same as foreign brands.