Robots, CNC machines, and factory automation equipment all require precise position control through servo drives, and in many cases, precise speed control is also required to manufacture products correctly and maintain workflow.

Many aspects of industrial drivers are important for achieving precise motion control, which involves three fundamental subsystems in real-time control design, namely sensing, processing, and driving. This article will discuss examples of supporting technologies for each subsystem.

Induction

Without precise position and speed sensing, precise motion control cannot be achieved. Induction can include motor shaft angle position and speed induction or conveyor belt linear position and speed induction. Designers often use incremental optical encoders with hundreds to 1000 slots per revolution to sense position and speed. These encoders are usually connected to microcontrollers (MCU) through orthogonal encoded pulses (QEP), thus requiring QEP interface functionality.

In contrast, absolute encoders have significantly higher accuracy, typically with more slots per revolution, and are precisely installed to provide absolute angular position. The sensed position is converted into a digital representation and encoded according to standard protocols. Examples of such protocols include Tamagawa's T-Format and iC-Haus GmbH's BiSS C. Previously, you needed a Field Programmable Gate Array (FPGA) to connect such encoders, but now more and more MCUs also have this function (as shown in Figure 1 below). Due to the fact that T-Format and BiSS C protocols are typically different from the protocols supported by popular communication ports or interfaces such as Serial Peripheral Interface (SPI), Universal Asynchronous Receiver Transmitter (UART), or Controller Area Network (CAN) commonly found on most MCUs, they typically require customizable logic blocks or proprietary processing units.

Absolute encoders can also be based on electromagnetic or rotary transformer like circuits, which require precise measurement of sinusoidal electrical signals. Therefore, precision operational amplifiers and voltage references are also important. Accurate motor current and voltage detection is always required for motor and motion control, especially when using sensorless control. A common solution is to use isolated/non isolated amplifiers and integrated low side current detection drivers for inline and inverter bridge arm low side detection.

handle

Executing motion control configuration files and algorithms in precision motion control systems requires a MCU with high computing power. To provide the necessary precision and accuracy, this type of MCU typically has a word length of 32 bits and native 64 bit floating-point support. Because the algorithm relies heavily on trigonometric function, logarithm and exponential mathematics, many MCU have hardware accelerators.

Considering the number of controlled motion axes or control loops, designers often use multi central processing unit (CPU) architectures or CPU like parallel accelerators. If there are additional supervision and communication tasks, multiple C's can also be considered