Introduction: In the robot industry, servo drive is a common topic. With the accelerated change of Industry 4.0, the servo drive of the robot has also been upgraded. The current robot system not only requires the drive system to control more axes, but also to achieve more intelligent functions.
In the robotics industry, servo drives are a commonplace topic. With the accelerated change of Industry 4.0, the servo drive of the robot has also been upgraded. The current robot system not only requires the drive system to control more axes, but also to achieve more intelligent functions.
At each node in the operation of a multi-axis industrial robot, it must use forces of different magnitudes in three dimensions to complete tasks such as set handling. The motors in robot are able to provide variable speed and torque at precise points, and the controller uses them to coordinate movement along different axes, enabling precise positioning. After the robot completes the handling task, the motor reduces the torque while returning the robotic arm to its initial position.
Composed of high-performance control signal processing, precise inductive feedback,power supplies, and intelligent motor drives, this high-efficiency servo system provides sophisticated near-instantaneous response precise speed and torque control.
High-speed real-time servo loop control—control signal processing and inductive feedback
The basis for realizing high-speed digital real-time control of servo loop is inseparable from the upgrading of microelectronics manufacturing process. Taking the most common three-phase electric-operated robot motor as an example, a PWM three-phase inverter generates high-frequency pulsed voltage waveforms and outputs these waveforms into the three-phase windings of the motor in independent phases. Of the three power signals, changes in the motor load affect the current feedback that is sensed, digitized, and sent to the digital processor. The digital processor then performs high-speed signal processing algorithms to determine the output.
Not only the high performance of the digital processor is required here, but there are also strict design requirements for the power supply. Let’s look at the processor part first. The core computing speed must keep up with the pace of automated upgrades, which is no longer a problem. Some operation control chips integrate A/D converters, position/speed detection multiplier counters, PWM generators, etc. necessary for motor control with the processor core, which greatly shortens the sampling time of the servo control loop and is realized by a single chip. It adopts automatic acceleration and deceleration control, gear synchronization control, and digital compensation control of three loops of position, speed and current.
Control algorithms such as velocity feedforward, acceleration feedforward, low-pass filtering, and sag filtering are also implemented on a single chip. The selection of the processor will not be repeated here. In the previous articles, various robot applications have been analyzed, whether it is a low-cost application or an application with high requirements for programming and algorithms. There are already many choices on the market. The advantages different.
Not only current feedback, but other sensed data is also sent to the controller to track changes in system voltage and temperature. High-resolution current and voltage sensing feedback has always been a challenge in motor control. Detecting feedback from all shunts/Hall sensors/magnetic sensors at the same time is undoubtedly the best, but this is very demanding on the design, and the computing power needs to keep up.
At the same time, in order to avoid signal loss and interference, the signal is digitized near the edge of the sensor. As the sampling rate increases, there are many data errors caused by signal drift. The design needs to compensate for these changes through induction and algorithm adjustment. This allows the servo system to remain stable under various conditions.
Reliable and precise servo drive—power supply and intelligent motor drive
Power supplies with ultra-high-speed switching functions with stable high-resolution control power reliable and accurate servo control. At present, many manufacturers have integrated power modules using high-frequency materials, which are much easier to design.
Switch-mode power supplies operate in a controller-based closed-loop power supply topology, and two commonly used power switches are power MOSFETs and IGBTs. Gate drivers are common in systems that employ switch-mode power supplies that regulate voltage and current on the gates of these switches by controlling the ON/OFF state.
In the design of switch-mode power supplies and three-phase inverters, various high-performance smart gate drivers, drivers with built-in FETs, and drivers with integrated control functions emerge in an endless stream. The integrated design of built-in FET and current sampling function can greatly reduce the use of external components. The logic configuration of PWM and enable, upper and lower transistors, and Hall signal input greatly increases the flexibility of design, which not only simplifies the development process, but also improves the Power Efficiency.
Servo driver ICs also maximize the level of integration, and fully integrated servo driver ICs can greatly shorten the development time for excellent dynamic performance of servo systems. Integrating the pre-driver, sensing, protection circuits and power bridge into one package minimizes overall power consumption and system cost. Listed here is Trinamic (ADI)’s fully integrated servo driver IC block diagram, all control functions are implemented in hardware, integrated ADC, position sensor interface, position interpolator, fully functional and suitable for various servo applications.
Fully integrated servo driver IC, Trinamic (ADI)
summary
In a high-efficiency servo system, high-performance control signal processing, precise induction feedback, power supply and intelligent motor drive are indispensable. The cooperation of high-performance devices can provide the robot with accurate speed and torque control that responds instantaneously during motion in real time. In addition to higher performance, the high integration of each module also provides lower cost and higher work efficiency.
Post time: Oct-22-2022