In the trend of industrial automation, motion control is a key part of it. Automating operations through machines can avoid a lot of human error, and can also speed up production efficiency and efficiency. How to make the machine act according to the command is the application category of machine motion control.
Today, the behavior patterns of robots are mainly based on the programming content provided by humans to perform repeated operations. The difference between robots and all kinds of mobile electronic products today, including cars, airplanes, etc., lies in whether they can operate on their own without participation in control. In the field of industrial manufacturing, due to the huge demand for repetitive and regular movements, this also happens to provide an excellent environment for the development of industrial robots.
Why do industry need motion control?
In the environment of industrial automation, motion control is one of the most critical links. The biggest shortcoming of mankind is that there will be mistakes, which for industrial production lines will often cause damage to the production line at a minor level and injuries to personnel in serious cases.
Automating operations through machines can avoid a lot of human error, but it must be ensured that the machine can accept the correct instructions and perform the expected actions, and these instructions must still be given to the machine manually. How to make the machine be able to act according to the command is the application category of machine motion control.
The motion controller is the brain of the machine's motion control system and is responsible for calculating the movement trajectory required by the machine. Because this operating procedure is very important, it is often executed by a digital signal processor (such as DSP) on the board to avoid additional burden and interference to the host computer. For example, the operation of the machine is interrupted due to the execution of anti-virus software, which will cause the production line to stop. The motion controller will use the orbit calculated by itself to determine the appropriate torque command, and send the command to the motor amplifier to generate the process moving.
The PID control loop must be closed during the operation of the motion controller. Since this operation requires extremely high accuracy and is necessary for stable operation, the control loop is often closed directly on the board. In addition to closing the control loop, the motion controller also monitors the emergency limit and stop functions to ensure the safety of the process. If these tasks can be performed directly from the board or real-time system, the stability, accuracy, and safety of the motion control system can be ensured.
The motion track usually represents the board control operation of the motion controller or the command signal output to the driver and amplifier, and then the motor will follow the track to move. The motion controller calculates the track section of the motion trajectory according to the parameter values of the program. For the calculation of the orbit, the motion controller can use the required target position, the maximum target speed, and the acceleration value provided by the user to determine the position in the three main action sections (including acceleration, constant velocity, and deceleration) it takes time.
For the acceleration section of the general trapezoidal trajectory, the movement operation will be started according to the stop position or the previous movement and will follow the designated acceleration ramp until the speed reaches the predetermined target speed of the movement operation. The movement operation can continue to move within the specified time according to the current target speed until the controller determines the start of the deceleration section and stops the movement at the specified target position.
If the exercise job is very short, usually before the acceleration is completed, the deceleration starting point is reached, the trajectory will be triangular rather than trapezoidal, and the actual speed reached may be lower than the set target speed. The S-curve acceleration and deceleration are the basic trapezoidal track enhancements, that is, the linear ramp for acceleration and deceleration is modified into a non-linear curve track. In this way, the appearance of the ramp has a fine-tuning control function, which can be adjusted for the performance of the motion tracking according to the restrictions of inertia, friction, motor dynamics, and other machine motion systems.
Create A Customized Motion Controller
Although motion controllers with DSP can already be used in many applications, for high-precision motion control operations like a 200kHz servo update rate, engineers must design the required motion controllers through a customized PCB. As a result, it is necessary to increase the development cost and time, and this type of motion controller has fixed functions and lacks the flexibility of redesign, making it more difficult to adapt to changes in motion control calculation formulas during operation. Other applications that require higher accuracy and flexibility include wafer processing machines in the semiconductor industry, or production line vehicle sequencing operations that can reset assembly lines in the automotive industry.
Motor Amplifier and Drive
Motor amplifiers or drives are important components in the system. The motion controller first uses a low-current analog voltage signal to form a command. After receiving the command through the motor amplifier, it converts it into a high-current signal to drive the motor. In order to be able to drive different types of motors, usually motor drives have many different variables. For example, the stepper motor drive only connects to the stepper motor, but not to the servo motor.
In addition to matching the corresponding motor technology, the drive must also provide the correct voltage, continuous current, and peak current to drive the motor correctly. If the drive supplies too much current, the motor may be damaged. If the current supplied by the drive is insufficient, the motor cannot achieve the full torque function. If the voltage is insufficient, the motor will not be able to run at full speed. In addition, the user must also consider the connection method between the amplifier and the controller.
The feedback device can be used to assist the motion controller to understand the position of the motor. The most common position feedback device is a phase difference encoder, which provides the relative position of the starting point. Most motion controllers are designed with this type of encoder. Other feedback devices include a displacement meter that can provide analog position feedback, a tachometer that can provide speed feedback, an absolute encoder that can perform absolute position measurement, and a resolver that can perform absolute position measurement.
Best motion control benefits
In the application of industrial robots, only through the complementary use of offline programming and online decision-making can the operation of the robot achieve the best benefits. With the rapid advancement of computer computing speed, more mature algorithms, and the advent of various industrial sensors, the application of traditional robots and the vast number of mobile electronic products has been accelerated.
CNC pointed out that through the integration of software and hardware, it can provide offline auxiliary programming and online acceleration decision-making for robot motion control. For example, the robot's drag action, automatic tracking, and other functions belong to offline auxiliary programming, and the integration of visual recognition technology belongs to the realization of online decision-making. Under this logic, we can define that the route planning of self-driving cars belongs to offline programming, and obstacle avoidance during driving belongs to online decision-making. Based on this principle, these mobile electronic products can be included in the broad definition of robots.
Motion control market trend:
The global motion control market is expected to expand from US$12.26 billion in 2020 to a compound annual growth rate (CAGR) of 5.09% by the end of 2025, reaching US$16.152 billion. The main factors for market growth are the increased adoption of manufacturing process automation and the increased interest in using integrated motion controllers.
In fact, the real purpose of artificial intelligence is to allow machines to have the ability to learn by themselves and to independently adjust appropriate production strategies according to different situations. At present, most of the functions called artificial intelligence in practical applications are used to transform human intelligence into calculation codes to achieve automatic decision-making purpose.
In the future, the development of artificial intelligence will grow stronger day by day, and good decision-making also requires a good motion controller to present the required manufacturing process. In the motion control of artificial intelligence, the controller needs to be able to provide a high-speed communication channel in order to receive and execute decisions from artificial intelligence and to feedback the status information of the robot. In addition, the function of the controller itself will also directly affect the workload of artificial intelligence. For example, if the controller can support the space arc function, artificial intelligence does not need to separately calculate the point coordinates on all arcs, which will also help reduce communication the amount of data.