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Use sensorless vector control with BLDC and PMS motors to deliver precise motion control

07 September 2021

The need for precise motion control is growing across applications such as robotics, drones, medical devices, and industrial systems.

Figure 1
Figure 1

Brushless DC motors (BLDCs) and AC-driven permanent magnet synchronous motors (PMSMs) can deliver the required precision, while also meeting the need for high efficiency in a compact form factor.

However, unlike brushed DC motors and AC induction motors, which are easy to connect up and run, BLDCs and PMSMs are much more complex.

Examples of precision motion control applications

Drones are complex motion control systems and typically employ four or more motors. Precise and coordinated motion control is needed to enable a drone to hover, climb, or descend. 

To hover, the net thrust of the rotors pushing up the drone must be balanced and equal to the gravitational force pulling it down. By equally increasing the thrust (speed) of the rotors, the drone can climb straight up. Conversely, decreasing the rotor thrust causes the drone to descend. In addition, there’s yaw (spinning the drone), pitch (flying the drone forward or backwards) and roll (flying the drone to the left or right).

Precise and repetitive motion is one of the features of many robotics applications. A stationary multi-axis industrial robot has to deliver different amounts of force in three dimensions in order to move objects of varying weights (Figure 1). Motors inside the robot supply variable speed and torque (rotational force) at precise points, which the robot’s controller uses to coordinate motion along different axes for exact speed and positioning...


Read the full article in DPA's September issue






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