What Is The Difference Between A Sensor Control And A Sensorless BLDC Controller

A sensorless BLDC controller is a very technical controller which uses Brushless Direct Current (BLDC) and an algorithm for filtering Back Electromotive Force, so what are the differences and which one is best? A BLDC motor can be used for industry and several consumer purposes because it is highly effective, compact, easy to control, and as a result it is now being applied to the automotive industry to aid the elimination of hydraulic systems and belts which will reduce fuel costs and add extra functions the vehicle. In recent years the cost of magnets and electronics have dropped significantly making the BLDC  motor more reasonably priced and being added to more items every day.

This motor is normally operated with one or more rotor positions however it is desirable that they are run without motion sensors as they are costly and easily breakable this is why the BLDC motor is a sensorless operation. A sensor less controller has to detect the rotors position the most popular method is drive two phases and then observe the generated voltage or the back EMF, this uses a more technical way to assess the position and speed however for machinery with propellers this does not have a problem with sensor less controllers.

In a sensor motor you have 3 sensors which are positioned at set degree angles and the positions depend on several details which are number of slots, winding configuration and the number of magnetic poles. The benefit of sensor commutation is that the sensor knows where the motor is all the time and because of this they often stall and work at low speed. Sensor failures can mean not being able to operate the motor at all and replacing this can be very difficult and sometimes impossible.

The only major difference between sensor and sensor less motors is the use of sensors, however controllers are a big trend in the technological world and people keep finding more items to use them on and more advancement to make them more effective and accurate. Controllers are used in hundreds of items that we use every day and we are more dependent than ever on using controllers as we do more things than ever mechanically rather than physical labor. Controllers have made factories, vehicles and many other things safer to use and have made our lives easier; however this sensor less BLDC controller is at present at the forefront of sensor less control technology and has proven itself as reliable and efficient. Even though it is a very technical piece due to prices of its components becoming cheaper, it makes this sensor less controller one of the best buys available in the market.  

How BLDC Motors Work

Before using BLDC motors, understand its mechanism.

You will be able to find BLDC motors or brushless DC motors in industrial equipment, appliances and medical instruments as they provide various advantages as compared to others like it.

However, before usingthese motors particularly for blade pitch control, you must first have a complete understanding of its mechanism which consequently results to a fast review of the construction of a DC motor.

A BLDC motor is particular type of servo motors which basically relies on wire coils on rotors and frames of rigid motors which on the other hand places permanent magnets all over the rotor.

Electric current passing through the windings make some magnetic field which either repels it from the magnet or attracts a winding to the magnet. Brushes placed on stators and contacts placed on rotors choose various windings as power while the rotors turn.

In BLDC motors, the coils make up the motors’ outsides and the rotors provide permanent magnets. Once again, the repulsions and attractions of the coils and the permanent magnets make the rotors spin. However, in BLDC motors, commutations do no occur on spinning shafts.

Even though these motors are more expensive than other brush-DC motors, they provide benefits. Their exterior coils dissipate heat better than those on rotors. BLDC motors do not have commutators or brushes to tire out or need maintenance regularly, thus they can function unattended for a very long period of time. Lastly, these motors don’t produce electromagnetic interference or EMI from machine-driven commutators.

Rather than utilizing mechanical commutators, servo motors like BLDC use automated commutation in switching the coils to on or to off. This kind of commutation is classified into two – the sensorless or the sensor-based.

The sensor-based motors, Hall-effect sensors are placed inside the coils of the motor to sense the position of the permanent magnets of the rotors. Microcontrollers or MCU read the states of the sensors and utilize a particular algorithm to know which of the coils to power as well as when.

On the other hand, sensorless motors require MCUs to measure the back electromotive force orr EMF produced across coils by spinning rotors’ magnets. The back EMF or BEMF defines the magnets’ positions.

However, the sensorless method is faced with a challenge because controller as well should power coils consequently to make the motors turn. Thus, how can one separate pulse-width signals of modulation which drive coils BEMF signals?

The answer is quite simple. Program MCUs to filter high-frequency PWM signals out as well as measure BEMF near the time when PWM signals pass through zero Voltage. The BEMF depends on various factors like coil resistance, number of coil windings, rotor magnets strengths and many others.