When riding an elevator, you want to get from one floor to another smoothly and safely. In an elevator drive, precise motion control enables the elevator to stop in a designated position and slow down smoothly until it comes to a complete stop. The lack of sophisticated motion control can cause the elevator to stop between floors by mistake, which can make the person riding the elevator feel dizzy and uncomfortable or unsafe.

Robots, CNC machines and factory automation equipment all require precise position control via servo drives, in addition to in many cases precise speed control, in order to properly manufacture products and maintain workflows.

Many aspects of industrial drives are important to achieve precise motion control, which involves three basic subsystems in real-time control design, namely sensing, processing and driving. This article covers examples of supporting technologies for each subsystem.

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Without precise position and speed sensing, precise motion control cannot be achieved. Induction can include motor shaft angular position and speed induction or conveyor belt linear position and speed induction. Designers often use incremental optical encoders with a few hundred to a thousand slots per revolution to sense position and speed. These encoders are typically connected to microcontrollers (MCUS) via quadratically coded pulses (Qeps) and therefore require QEP interface capabilities.

In contrast, the accuracy of absolute encoders is significantly higher, which typically have more slots per revolution and are precisely installed to provide absolute angular position. The sensing position is converted into a digital representation and encoded according to a standard protocol. Examples of such protocols are Tamagawa’s T-Format and iC-Haus GmbH’s Bidirectional Serial Synchronization (BiSS) C. Previously, you also needed field programmable gate arrays (FPgas) to connect such encoders, but now more and more MCUS also have this capability (as shown in Figure 1 below). Because the T-Format and BiSS C protocols are generally different from those supported by popular communication ports or interfaces such as Serial Peripheral Interface (SPI), Universal Asynchronous Receiver Transmitter (UART), or Controller Local Area Network (CAN) that are common on most MCUS, So they often require customizable logical blocks or proprietary processing units.